Sifting through the opposing rulings on the legality of the subsidies on the federal health insurance exchange.
This review traces the development and study of the second-generation photosensitizer 5,10,15,20-tetra(m-hydroxyphenyl) chlorin through to its acceptance and clinical use in modern photodynamic (cancer) therapy. The literature has been covered up to early 2011.
The field of photodynamic therapy (PDT) (1) has seen continuous advances in the past decades. Modern studies began with investigations on haematoporphyrin (Hp) (2). To some extent the progress made can be traced along the lines of the different types of photosensitizers (PS) which have been developed. Typically, the various PS used in PDT are termed as first-, second- and third-generation PS (3). The first generation is basically Hp derivative (HpD) which was approved as Photofrin for clinical use in 1993 (4), the second generation are simple, chemically pure and defined PS (e.g. Foscan) (5) and the third generation are systems currently in development which contain specific targeting groups or have been developed based on clear medical, photophysical and chemical design principles (6).
Broadly speaking, the properties for an ideal photosensitizer are: chemical purity, high quantum yield of singlet oxygen production, significant absorption in the long wavelength region (700-800 nm), preferential tumor localization, minimal dark toxicity and delayed phototoxicity, stability and easy to dissolve in the injectable solvents (formulation). While Photofrin is an effective photosensitizer, its shortcomings could not be neglected. This gave rise to the development of chemically pure PS with optimized photophysical properties. This so-called second-generation PS have entered a lively competition during the last decade to the benefit of both science and the patients (7-9). This is related not only to the use as a photosensitizing drug for treatment but for the use in photodiagnostics (PD) and imaging as well (10). Within this second generation, porphyrins are the most widely investigated class of compounds and it is generally assumed that these macrocycles and their reduced derivatives such as chlorins and bacteriochlorins are the most suitable candidates for PS drug development (11-17).
5,10,15,20-Tetra(m-hydroxyphenyl)chlorin (mTHPC, 1) with the generic name "Temoporfin" and the proprietary name "Foscan®" is one of these promising reduced porphyrins which has been the subject of investigations by a number of research groups for almost two decades. Now, Temoporfin has reached an exciting state of development as it has gone through the requisite clinical testing and is regarded as an established cancer drug on the market. It can thus serve as an illuminating show and test case for the potentials and limitations of current PDT drugs and might give an insight into the trends of development for the new generation of PS. This review intends to discuss the published works of mTHPC with the intention of: summarizing the available facts and discussing mTHPC's potential continuation; comparing known properties with the required attributes for an ideally designed photosensitizer; if possible, delineating novel design and application principles from the biochemical and clinical results obtained with mTHPC. For ease of argument, unless expressively stated otherwise, in the following "PS," "drug," etc. relates to mTHPC.
Many general PDT reviews have appeared over the years. They are too numerous to list here and often their content overlaps. Likewise, a multitude of brief reviews on individual cancer types or PDT applications can be found; those that add to the context of this treatise are listed in the individual subsections. Next to historical reviews (18-21), Bonnett's book on Chemical Aspects of Photodynamic Therapy (3) is still a good entry into the field for medicinal chemistry students, as are classic reviews by Dougherty and Kessel (4,18,22-24) and more chemically oriented treatises (25). A more recent three part series on the basics of PDT by Castano et al. from 2004 is recommended for an entry into the field especially for students (26-28).
CHEMISTRY AND DEVELOPMENT OF TEMOPORFIN
Synthesis, characterization and detection
In the mid-1980s Bonnett et al. undertook a significant screening procedure (btophysically, biochemically and pharmacologically) of a library of porphyrins for the purpose of discovering an effective second-generation photosensitizer (29). They decided on the tetra(hydroxyphenyl)porphyrins as the most promising compounds after initial tests with their porphyrin analogs revealed a 25-30 times enhancement in photosensitization compared to HpD in tumor models (30) and gave superior tumor localization in C3H mice (31). After thoroughly comparing the essential properties of the ortho, meta and para phenyl isomers (32) a similar necrosis depth was noted for the m,p compounds, while the ortho isomer resulted in higher skin sensitivity. Overall, the meta isomer was the best in terms of cost and benefits (Fig. 1). The only significant drawback of these porphyrins was their weak absorption in the area of 630 nm which meant nothing was gained in this regard compared to Photofrin®. Nevertheless, a number of in vitro and in vivo tests established the basic PDT properties and advantage of the mTHPP porphyrin (33-41).
To improve the absorption properties, chlorin analogs of these hydroxyphenylporphyrins were synthesized via a diimide reduction (42). This reduction step was introduced to gain a more intense and more redshifted absorption band to allow deeper penetration into tissue. The chlorin 5,10,15,20-mTHPC, 1 was derived from the parent porphyrin (5,10,15,20-tetra (m-hydroxyphenyl)porphyrin) (mTHPP, 2) and showed effective induction of necrosis in tumor tissue in PC6 tumor inoculated mice with less muscular edema than in other PDT compounds. This project was the first successful attempt at a methodical approach to synthetically optimize the absorption characteristics of tetrapyrrolic PS for PDT. Formally, the synthesis of mTHPC involves the acid-catalyzed condensation of pyrrole with m-hydroxy benzaldehyde to yield the porphyrinogen, followed by oxidation to mTHPP and then reduction to mTHPC.
In many regards mTHPC fits many of the requirements specified above for an ideal photosensitizer, and thus may be regarded to be "better" than Photofrin (43,44). It can be prepared as a chemically pure compound, it shows enrichment in tumor versus normal tissue and has ari absorption maximum at 650 nm, redshifted compared to HpD which means deeper light penetration. In addition, mTHPC requires smaller quantities for administration, shorter treatment times and a lower light dose to achieve the desired PDT response (45).
Briefly, its industrial development proceeded as follows. Initially, a UK biopharmaceutical company (Scotia Pharmaceuticals Ltd., UK) developed the drug, first in collaboration with Boehringer Ingelheim and in 1999 was granted orphan drug status by the U.S. Food and Drug Administration (FDA) and was accepted for marketing review by the European Medicines Evaluation Agency (EMEA). In 2000, it was granted fast track review status by the FDA. Nevertheless, approval by the FDA was declined in September 2000, and then in January 2001 by the EMEA. As a result, Scotia Holdings plc. had to go into administration. Scotia was one of Britain's oldest biotech compames and at its height in 1997 had a market value of £500 million. Nevertheless, an appeal to the EMEA was successful in June 2001 and later in 2001 marketing authorization was given as a local therapy for the palliative treatment of patients with advanced head and neck cancer who have failed prior therapies and are unsuitable for radiotherapy, surgery or systemic chemotherapy. Financially, this did not save Scotia, which, renamed as Quantanova, was sold to the German Biolitec AG in April 2002. Since then, Biolitec Pharma distributes the drug and investigates further uses.
After mTHPC was recognized as a potential PS analytical investigations were undertaken to obtain detailed knowledge of the compounds properties. The fine structures in the 1 H-, 13 C- and 15 N-NMR spectra have been clarified (46) and mass spectrometric studies undertaken (47). To enable research into kinetic phenomena of the radical Type I mechanism, ESR experiments observing mTHPC with and without stable free radicals (e.g. di-tert-bulyl nitroxide) have been undertaken (48). A suite of photophysical measurements were performed on the o-, m- and p-tetra(hydroxyphenyl)porphyrins in 1988 by Bonnett et al. including fluorescence, flash photolysis and pulse radiolysis studies in order to characterize the singlet and triplet excited states of these macrocycles (49). A comparative study including the reduced derivatives mTHPC and the bacteriochlorin analog (mTHPBC, 3) was performed in 1999 (50). The absorption maximum of the long wavelength absorption band is shifted from 644 in the porphyrin to 650 nm in the chlorin and 735 nm in the bacteriochlorin. Photophysical properties of the first excited state were similar in all three compounds and the quantum yield for singlet oxygen formation was 0.43-0.46 in aerated methanol.
A study of the absorption and emission dependence upon pH was also done for mTHPC, mTHPP and other PS (51). Within the physiological pH range 6.5-7.2 no pH dependence of the fluorescence intensity was found. Only below pH 6 a significant loss of intensity was observed (52). The dynamics of the excited states of mTHPC have been investigated in time-resolved studies on the fs to µs time scales (53). The lifetime of the singlet state was found to be longer for mTHPC compared to other PS, which might be one of the reasons for its high efficacy as a PS. Experiments within the cytoplasm of cells later revealed a decrease of this lifetime from 7.5 to 5.5 ns which was attributed to aggregation in the biological environment (54). Resonance light scattering experiments showed the formation of J-aggregates for mTHPC in aqueous solution (55,56).
The acid-base properties of mTHPC were analyzed by Bonnett et al. (57). Spectrophotometric titration of the photosensitizer in a methanol/buffer mixture gave pK3 and pK4 values of 3.45 and 1 .45, respectively, while the phenolic groups exhibited a pKa of 10. They also investigated the singlet oxygen production from mTHPC through the photobleaching of bilirubin, which was accelerated five-fold in the presence of a catalytic amount (5 mol%) of the PS, but hindered in the presence of the singlet oxygen quenchers, ß-carotene and 2,5-dimethylfuran. A comparative analysis of the pH-dependent properties showed that only mTHPP but not mTHPC changed lipophilicity in the pH range 4-8 (58).
The analytical detection of PS in biological material is a challenging topic. Detection of mTHPC in human plasma following infusion was carried out successfully via reverse-phase HPLC-UV detection with a sensitivity of 15 ng mL-1 (59). This method was then extended to mouse, rat and human tissue (60). Using coloumetric detection, Barberi-Heyob et al. improved the sensitivity for detecting mTHPC in plasma to as low as 5 ng mL-1 (61). A similar detection could also be achieved using an improved HPLC fluorescence detection method (62). Formation of a 1:2 cyclodextrin:mTHPC complex resulted in an up to 300 times enhanced fluorescence signal (63) and could be used for detection in human plasma (64). Similar results were later reported for 5,10,15.20-tetra-kis(4-hydroxyphenyl)porphyrin (65). Two-step laser MS was used as a qualitative analytical tool to study PS purity (66). There is also significant variability in the fluorescence properties depending on the tissue and PS type. Tissue relevant fluorescence excitation-emission matrices have been collected to aid in the analysis (67). Dynamic capillaroscopy has been used as a means to evaluate pharmacokinetics in vivo (68,69).
One of the most important questions regarding the use of a PS relates to its photostability. Porphyrins typically undergo slow photodegradation with time. The importance of the phenomenon of photobleaching, i.e. the irreversible phptodestruction of the pigment, for PDT has been recognized as a potential means to control both the pharmacokinetics of the drug and the occurrence of undesired side-effects. However, the balance of photobleaching versus photoaction is delicate, for if the sensitizer bleaches too rapidly, tumor destruction will not be complete. However, with appropriate knowledge of bleaching rates and drug dosage, light damage to normal tissue at the treated site may be reduced due to controlled minimized sensitizer concentrations in these areas. Another plausible application of photobleaching is the elimination of the drug, consequently reducing postoperative skin photosensitivity, which is the main adverse effect patients experience when undergoing PDT.
Initially, Bonnett et al. examined in a comparative study the photobleaching properties of methanoiic solutions of mTHPC, mTHPP and mTHPBC (70). mTHPC and mTHPBC were subject to pronounced photodegradation following laser irradiation at 514 nm, while mTHPP resulted in the formation of quinoid porphyrins (70,71). The photophysical impact on mTHPP is less pronounced than for either reduced analog, but the rapid degradation of mTHPBC precludes a practical use in PDT. An analysis of the degradation of these sensitizers via NMR. UV and MS showed the photoproducts largely to consist of benzoquinone isomers (4). dihydroxyphenyl derivatives (5) and ring-opened chains followed by further break-down to methyl 3-hydroxybenzoate, succinimide and maleimide (Fig, 2).
Recent results indicate the rate of photobleaching of mTHPBC to be strongly dependent on the degree of aggregation of the PS (72). A combined use of HPLC and electrospray ionization tandem MS (ESI-MS) identified mTHPP and several hydroxylated derivatives of both mTHPC and mTHPP as initial photobleaching products (73). Angotti et al. found evidence for both Type I and Type II reactions being involved in the photobleaching of mTHPC (74) and identified mTHPP as the primary photoproduct (75). Similar results were obtained using the HPLC separation of mTHPC photoproducts after irradiation with 514 nm laser light in combination with MALDI-TOF MS and UV/Vis spectroscopy. Again, the formation of mono, di und trihydroxylated derivatives of mTHPC and an unidentified degradation product was reported (76). Interestingly, pulse laser irradiation of mTHPP at 647.5 nm resulted in the formation of benzoquinoid porphyrins followed by formation of dimeric (6) and oligomene photoproducts (77).
ESR experiments of organic solutions of mTHPC were performed to elucidate the mechanism of photobleaching in more detail (78,79). mTHPC produces superoxide anion radicals more efficiently than Photofrin and while both singlet oxygen and superoxide anion radicals contribute to the photobleaching the latter is primarily involved in the conversion to mTHPP. Initial in vitro photobleaching experiments were undertaken with Chinese hamster lung fibroblasts and showed that the rate of photobleaching was much higher for mTHPC than mTHPP or Photofrin (80). A study of mTHPC in solution with fetal calf serum (81) showed that this process depends on oxygen level and alterations in the microenvironment of the sensitizer. A clear relationship between 1 O2 and bleaching rate was found (82) and the singlet oxygen concentration is inversely related to cell survival (83). Likewise, there is a correlation between drug concentration and rate of photobleaching for a fixed laser fluence rate (84).
Overall, the light-induced chemical changes of mTHPC described in the various works covering ex vivo experiments are similar in terms of identified photoproducts. However, the quantitative findings differ strongly depending on the experimental conditions and the microenvironment (83,85-89). This limits the utility of the in vivo photobleaching models. For example, the intracellular photobleaching in a murine macrophage cell line was found to exhibit a complex dependence on oxygen level and an inverse dependence on fluence rate (90). For rat skin the photobleaching kinetics were biphasic and were different from those for tissue oxygen consumption (91). Monitoring photobleaching in vivo is especially difficult in an interstitial environment (55).
Few studies have investigated the relative photostability of various PS. For example, a study investigating the stability of hypericin in various model systems noted significant differences in stability, with mTHPC being one of the least stable PS compared to phthalocyanine derivatives and hypericin (92). Likewise, a recent study compared Photoditazine, Radachlorin and Foscan and found Foscan to be the most stable of the three PS (93). This can be attributed to the higher degree of aggregation for mTHPC in solution, which inhibits singlet oxygen formation.
PHARMACOLOGY AND BIOCHEMISTRY
Uptake, localization and metabolism
Uptake. The uptake of the compound into cells appears to be pH independent (94). A comparative study of the uptake of some PS into human breast cancer cells showed a pH-dependent uptake for Hp IX and similar results were obtained with other human cancer cell lines (95). However, in contrast to this, its activity once taken up decreased with extracellular pH (better at 6.8 than 7.4). Likewise, low temperature (4°C versus 37°C) resulted in increased photosensitivity of human colon carcinoma cells (95,96). The uptake is determined to some extent by the deaggregation process of the drug and the drug appears to bind to lipoproteins (97). This was further indicated by experiments with [14 C]-mTHPC which was shown to bind to several lipoprotein fractions of the human serum. The approximate distribution was: VLDL 6%, LDL 22%, Lp(a) 17%, HDL 39% and soluble fraction of mTHPC 16% (98). The exact physicochemical type of binding to these species is still unknown. However, a binding study of 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin with human serum albumin showed that hydrophobic interactions appear to be the main driving force (99) Interestingly, this study indicated that chromophore binding reduces the a-helix structure of the protein.
The uptake of Foscan is affected by many factors. For example, in vitro studies indicated that the PDT activity is five times lower in the presence of protein as compared to serum-free medium (100). It appears that the drug is taken up in aggregated form and that subsequent monomerization is a slow process which may explain the observed time delay in maximum PDT activity. However, the presence of serum during the illumination period had no effect indicating that the drug may be sequestered upon entering the cell (101). There is also evidence for the existence of aggregated forms of Foscan in the presence of protein which are not protein bound, indicating the possibility for similar states of matter in vivo (102). Aggregation effects were also noted in HeLa cells (103). A model study investigated the release and redistribution of Foscan from various plasma proteins. The rate of redistribution was low and HDL-mediated endocytosis was proposed as the main mode of drug transport in cells (104). Nevertheless, the uptake of LDL and thereby mTHPC is far more efficient and may reflect the real uptake pathway for the drug. Administration of glucose resulted in increased PDT effect in animal models, most likely due to changes in tumor physiology or transport processes (96). Metabolic inhibitors were reported to have no effect (105). In a mouse model the plasma mTHPC level correlated with the PDT effect, while the tumor uptake did not, indicating that shorter drug-light intervals with low drug doses might be better for treatment (106).
A detailed study compared the pharmacokinetics in mice and humans and found that the drug distribution over the lipoproteins and the metabolism of the lipoproteins had no impact on the plasma pharmacokinetics. Thus, the longer time needed for high drug concentrations in human plasma compared to that in mice could indicate the formation of a drug depot. The different pharmacokinetics between rodents and human illustrate the problems associated with using animal models for predicting drug behavior in humans (107).
Localization. The exact localization of the PS in the cell determines its impact on the molecular machinery and thus the efficacy of the PDT effect. This is mainly a result of the short life time and diffusion constant of the reactive oxygen species. In practical terms the identification of the localization sites has become much easier since the advent of confocal laser scanning microscopy. Administration of the drugs with organelle specific probes which have fluorescence maxima different from the PS now allows the identification of the intracellular sites where PS accumulate and the damaged sites after photoactivation.
Generally speaking the localization of PS depends on their charge, their hydrophobic or hydrophilic properties, their aggregation state and the molecular substituent pattern. As a rough approximation hydrophobic PS with =2 negative charges pass the plasma membrane easily and typically show good uptake. More polar PS with > 2 negative charges cannot pass the membrane via diffusion and are taken up by endocytosis. Thus, the various PS exhibit quite different intracellular localizations (26). This can be modulated significantly through use of different delivery vehicles and strategies for the PS drugs (108).
In terms of organelles the most interesting ones for PDT are the lysosomes, mitochondria, plasma membrane, Golgi apparatus and endoplasmic reticulum. Examples for PS localizing (predominantly) in these organelles include aluminum phthalocyanine disulfonate, benzoporphyrin derivative (BpD), deuteroporphyrin IX and Foscan. However, it must be taken into account that intracellular redistribution and relocalization may occur as a result of light-induced relocalization (109). Even more specific intraorganellar localizations have been observed for PS related to the natural protoporphyrin IX system. For example, dicationic protoporphyrin IX PS were found to be highly effective inhibitors of the peripheral benzodiazepine receptor in the outer mitochondrial membrane, which is upregulated in some tumors (110). The binding to such specific receptor sites is the driving force for the development of third-generation targeted PS bioconjugates. For an excellent review on the various physicochemical parameters affecting PS localization see Mojzisova et al. (111).
The subcellular localization of mTHPC in human adenocarcinoma cells was studied by Melnikova et al. using fluorescence microscopy (112). Initial studies reported that mTHPC localized generally within cellular organelles, but not the nucleus. After cell illumination, photosensitized damage was detected using a fluorescent probe. The mitochondria and the Golgi apparatus were found to exhibit extensive cytoplasm vacuolization and other alterations. Kessel initially described the localization in mitochondria, where illumination resulted in a release of cytochrome c (97). Chinese hamster lung fibroblasts exhibited a diffuse localization in the cytoplasm (113), as did murine macrophages (114). A 2005 study of mouse sarcoma cells using fluorescence anisotropy imaging showed localization of Foscan in the nuclear envelope (115). No such localization was found for other PS (PPIX, LS11, Photofrin, Pc4, HPPH). Some studies reported localization of mTHPC in the lysosomes (116). More details are given in Table 1 for individual cell lines.
A detailed confocal fluorescence microscopy study of a human adenocarcinoma by Guillemin and coworkers showed only weak localization in lysosomes and mitochondria. Instead, Fosean was found to be localized in the endoplasmic reticulum (ER) and the Golgi apparatus and the latter two were the sites of primary PDT damage (117,118). In this context it has been speculated that the human ATP-binding cassette transporter isoform B6 (ABCB6), which is located in the Golgi and has elevated expression levels in breast cancer patients, might play a role in transporting porphyrin-related compounds (119).
The tissue localization has been studied in many experiments most of which are discussed below in the animal model section. An interesting effect noted in an early study was the difference between mTHPP and mTHPC (120). Chemically, both are similar in hydrophobicity. Nevertheless, the porphyrin localized mainly in the stroma of tumors (breast cancer implanted in mice) while the chlorin was distributed in the vascular interstitium and neoplastic cells of the tumor. Thus, PDT with the former resulted mainly in destruction of the mierovasculature of the tumor while the latter affected both the vascular walls and the tumor cells. However, the PDT drug blood serum levels and vascular photosensitization appear to be decoupled (69) indicating a more indirect effect of the PS on the blood capillaries.
The time course of the uptake differs from organ to organ. A squamous carcinoma cell (SCC) hamster model showed initial uptake in the liver and kidney and then later in the blood vessels and smooth muscle (121). However, many of these studies report overall tissue distribution or bulk uptake and that tells little about the real extravascular distribution. This was clearly shown in a study by Mitra et al. who used two-color confocal spectroscopy and a mouse mammary tumor model and identified the intratumor distribution of the drug. It clearly varies significantly with time and spatially within the tumor (122). All these aspects clearly have clinical implications.
Metabolism. An important question in drug development is whether mTHPC is metabolized by the body. However, only a small number of studies have addressed this question. Analytical work on samples of plasma, bile, feces, urine and liver using HPLC and electrospray MS confirmed that mTHPC was not metabolized but excreted unchanged apart from fractions of mTHPP and hydroxylated mTHPC derivatives which were already known to be photochemical oxidation side products (123,124). Its plasma binding is quite distinct from other PS (125). A study with radiolabeled Temoporfin in colorectal cancer induced mice showed a rapid clearance from blood and the concentration in the tumor reached a maximum at 2 days. Nearly 40% of the drug was excreted in the feces during the first day, almost none was recovered from the urine. The elimination half-life was estimated to be 10-12 days for this system (126).
Pharmacokinetics. The pharmacokinetics of any PS depend on a variety of factors. These range from aggregation-deaggregation equilibria in the blood, binding to serum components, binding to and penetration through the blood vessel wall, diffusion through the organ/tumor parenchyma, potential metabolization and finally excretion. In principle the quantification of PS in tissue and blood is easy due to their fluorescence. For Foscan, ex vivo fluorescence spectroscopy is a relatively fast and reliable method (121) and can be accompanied by to vivo spectrofluorimetry and chemical analysis after extractions (127). However, quantification methods based on this are problematic and depend on the extraction method used and the type of PS. One example for this is the use of Solvable(TM) as a tissue solubilizer (128).
Other methods include HPLC analysis of tissue sample or administration of radiolabeled compounds followed by scintillation measurements. Likewise, noninvasive measurements based on tissue fluorescence are possible. In reality a comparison of pharmacokinetic data from different sources and laboratories is difficult. This relates to the use of different standards, sample preparation and the incompatibility of some animal models. Based on the different uptake and localization mechanisms the overall pharmacokinetics vary significantly from PS to PS and half-lives range from a few minutes to days (28). A good comparison of the pharmacokinetics of the various PS available up to the mid nineties was given by Moore et al. (129). Similar to the situation for uptake, the exact pharmacokinetics depend on the species and tumor model used (28).
For Foscan, the following data are based on a number of Phase I studies (130-132). The pharmacokinetics of mTHPC in humans was evaluated thoroughly in 1996 in a clinical study with concentration measurements of plasma, cancer and normal tissue biopsies (130). After drug delivery blood was taken in periodic time intervals and biopsies were taken immediately prior to PDT from 25 patients who suffered from various cancers. The maximum concentration of mTHPC in blood was reached by 10-24 h which distinguishes Foscan® from other drugs when delivered directly into the blood cycle. Depending on the study a half-life of the drug of 30-45 h was established (130,131). Probably, it is initially accumulated in the liver followed by a slow release mechanism. The pharmacokinetics of mTHPC compared to ALA was reviewed previously (133). Early studies in a murine model indicated that Temoporfin concentrations in heart and skeletal muscle decline much slower than in blood (134).
Clearly the interaction of Temoporfin with plasma is of relevance. A study of the distribution in human plasma and in a rat model in vivo concluded that the drug quantitatively binds to plasma components (125). The site of binding appeared to be highly localized to a hitherto unidentified nonlipoprotein fraction of plasma. This behavior is unique compared to other PS and might be responsible for the specific pharmacokinetic behavior of mTHPC. The importance of a careful study of the pharmacokinetics was shown again in a recent study on "compartmental targeting" of Foscan. A mouse model showed clearly that a fractionated double injection protocol was superior to a single dose administration of the drug (135).
Many efforts have been made to develop effective PDT dosimetry methods (136). The photobleaching mTHPC (see above) has been proposed as one method. However, while the photobleaching rate is oxygen dependent and the oxygen concentration correlates with the photobleaching rate, this dependency is related to the microenvironment. Thus, without knowledge about the tissue oxygenation photobleaching cannot be used for dosimetry (82). Photobleaching results can differ widely depending on the experimental conditions making clear conclusions about the utility of dosimetry difficult (83,85-87). An alternative dosimetric method might be the determination of the mTHPC plasma level, as indicated by a comparative study of the mucosa of the oral cavity, the esophagus and the bronchi of 27 patients using light-induced fluorescence spectroscopy (131). This is supported by a study which compared dogs, rabbits, rats and humans (137).
Other methods included low-power remittance fluorescence (138), optic fiber spectrofluorimetry, reactive oxygen species assays using dichlorofluorescein determination (139) and soft tissue models based on agar gel (140), among others. Overall, it has to be concluded that an approximation of the appropriate drug dose from preclinical results is problematic. The biodistribution of the drug varies from tissue to tissue and from species to species. To use body weight and/or amount of surface area as a means of extrapolation from species to species is unreliable, and even variations between individuals are often huge (133,137). This is clearly a significant problem. A better approach might be taking into account the plasma concentration of drug and/or good fluorescence measurement and clinical experience (131). A study by Wang et al. criticized the correlation/prediction of the PDT response based on singlet oxygen production metrics (141). However, the model employed is rather specific and it is yet unclear how general these results are.
Another problem is how to effectively measure and control the various parameters that affect PDT during interstitial application. While this area is well developed for radiotherapy, phototherapeutical applications still require further developments (142). This is a fundamental problem irrespective of the tumor treated. A first animal study that attempted to address the problem of monitoring both explicit (fluence rate) and implicit parameters (photobleaching, oxygenation and blood volume) was performed recently and showed that indeed such a monitoring is possible, albeit difficult (55). PDT dosimetry is probably the most complex and difficult aspect of any PDT application. The exact methods used will always depend on the individual situation.
Formulation is an important aspect of any drug development. For PS this is especially important as different treatment modalities (e.g. skin versus internal cancers) or chemically very distinct drugs (e.g. ALA versus porphyrin based drugs) require diverse application systems. Thus, significant potential still exists for the investigation of different formulations and drug delivery strategies for PS (143). For example, a possibility js the incorporation of the drugs into gel systems. The cubic phase (monoolein/water, 70:30, wt/wt) appears to be a suitable system as initial studies showed good stability of various PS in the gel formulations (144).
Due to the poor solubility mTHPC can only be used with a formulation process prior to administration. Initial applications used formulations in PEG and ethanol or propylene glycol (97). Some results point toward problems with regard to optimum administration of the drug. For human skin fibroblasts it was found that preincubation of mTHPC at 37°C for a day prior to administration significantly improved the PDT effect (145). This indicates problems with solubility (or drug preparation) of the active PS. Considerable effort has been spent on the preparation of nanocarrier formulations for PS (146,147). For mTHPC this is evidenced by the shift in developmental attention from Foscan® (a solution) to Foslip® (a liposomal formulation).
As a photochemical reaction PDT requires investigations into the dependency on exciting wavelength, light intensity, fluence rate and type of light application, photophysical characteristics of the PS and so on. It is also dependent on the clinical setting, i.e. the type of cancer to be treated. Nevertheless, some general considerations, for example those made for photobleaching above, can be made for Foscan.
Early studies with malignant mesothelioma cells indicated that the drug-light interval has a significant effect on the therapeutic action. Typically selectivity is improved with longer drug-light intervals and Foscan showed better results with longer intervals than used for Photofrin (148). Higher light doses were found to be more advantageous than increasing the drug dose (149). Obviously, this also means that the light dose is important when considering the toxicity of the treatment for healthy tissue (150). The optimum drug-light interval varies with the tissue. Various studies addressed the effects of green (514 nm) versus red light (652 nm). Roughly speaking the tissue absorption is 2-3 times greater at 514 nm and 4-5 times as much light might be required to achieve the same phototoxic effect as 652 nm light (151). Even more importantly light penetration is shorter at 514 nm which reduces the chance of tissue perforations, e.g. in the esophagus.
Fractionation of light can also improve the PDT effect. However, the effects are very dependent on the dark intervals between light administrations. Typically, short dark times appear to be better. For example, an animal study on Rifi tumors indicated dark times of 30 s to be best (152). An interesting study using MCF-7, an estrogen-dependent human breast carcinoma cell line, showed that fractionated light, i.e. giving the illumination in short pulses (0.05 s light, 0.05 s dark) instead of continuous illumination for a few minutes increased the photodynamic effect significantly (ca 50% for mTHPC, somewhat less for mTHPC-MD2000) (153). A later study with on/off illumination delivering the same total light fluence, i.e. a 50% reduction of the power density, doubled the cytotoxicity (154). A study using an SCC model showed a clear dependence of the photodynamic effect on the fluence rate. Lower fluence rates at both 514 and 652 nm induced higher tissue damage but less selectivity (155). Other animal studies gave similar results (156). A detailed study by Coutier et al. correlated the fluence rate, tumor oxygenation and PDT effect and found that lower fluence rates limit the extent of oxygen depletion in the tumor and thus result in better PDT outcomes (157).
Mechanism of action
From a chemical viewpoint the mode of action of any porphyrin PS is based on simple photochemistry and mTHPC primarily acts through the generation of singlet oxygen like other PS. Early studies on the photodynamic effect in the presence of singlet oxygen scavengers showed a reduction in the photoinactivating ability of mTHPC (113). For example, sodium azide strongly suppressed PDT activity in human tumor cells, while superoxide anion radical, H2 O2 or hydroxyl radical scavengers had no effect (158). However, optimization of current and future drugs requires a more detailed understanding of the intracellular chemical and biochemical reactions in molecular medicine terms. In conceptual cell biological terms this requires knowledge about the impact of PDT on cell signaling and cell metabolism (159). In clinical terms it is necessary to know the mechanism of tumor destruction at the individual tumor cell level, to understand vascular effects and unravel the related immune system effects (160). Unfortunately, single cell studies on the singlet oxygen distribution are thus far available only for other PS (161).
Cell signaling and metabolism. PS can affect many different signaling pathways (162). For example, a number of PS induce a rise in intracellular Ca2+ and affect directly or indirectly Ca2+ -binding chaperones, antiapoptotic proteins, caspases, phospholipases and the nuclear factor of activated T cells. The phospholipases link the calcium signaling to the lipid metabolism, e.g. through the release of acrachidonic acid derivatives. Likewise, cyclooxygenase-2 expression can be activated through PDT. Other affected second messengers are ceramide, cytokines and tryrosine kinases, especially mitogen-activated protein kinase and epidermal growth factor. PDT also acts on transcription factors, e.g. activator protein 1, NF?B and transcription factor E2F. Cell-cell interactions, e.g. cell adhesion can be influenced as well. Other regulatory factors such as cytokines and neutrophils or stress response proteins are important for the PDT effect as well. Other possible PDT effects include angiogenesis and tumor responses to changes in the oxygen level. The latter notably includes tumor hypoxia as PDT can rapidly deplete the tissue oxygen and affects the tumor blood supply. Note, that many of these responses are interconnected. For a detailed discussion of the effect of the various PS see Castano et al. (27). Likewise, NO might be an important target for PDT action. While data on the interplay of mTHPC and NO action are sparse, the importance of nitric oxide has been discussed widely for other PS (163).
For Foscan the available data are as follows. A study by Kessel in 1999 showed that illumination of murine leukemia cells treated with mTHPC resulted in the release of cytochrome c and activation of caspase-3 resulting in an apoptotic response (97). Mitochondrial damage and cyt c release was also described for other myeloid leukemia cells (164), human colon adenocarcinoma cells (165) and squamous cell carcinomas (166). Later Bezdetnaya and coworkers showed that the ER and Golgi are the sites of the primary effects (117,118). They clearly showed that enzymes in the Golgi, such as uridine 5'-diphosphate galactosyl transferase, or in the ER, such as NADH cyt c reductase, are inactivated through PDT treatment, while mitochondrial marker enzymes (cyt c oxidase and dehydrogenases) were unaffected (167). In order to correlate these data it must be noted that 24 h post-treatment the fluence dependency of the PDT effect was similar for changes in mitochondria and cell death (118). Thus, although mitochondria are not affected directly they will be affected significantly by late and indirect effects. This gives rise to a model wherein the ER/Golgi complex originates a death signal for the mitochondrial apoptotic processes. Thus, ER/Golgi localizing PS act in a different, more indirect manner compared to mitochondria localizing PS.
Reactions of the lipid peroxidation pathway appear to be not very important for the Foscan action. A study of human adenocarcinoma cells which incorporated a-tocopherol, a lipophilic phenolic antioxidant, did not elicit any photoprotection against PDT. Instead, the mTHPC PDT effect was enhanced at concentrations of 0.33 mM and above (158,168). An interesting study investigated the effect of radio- and phototreatment on the level of serum a-N-acetylgalactosaminidase, an extracellular matrix degrading enzyme that appears to be exclusive for cancer cells (169). While radiodynamic treatment reduced the level of this enzyme significantly, PDT lowered it to background level within 2-3 days after PDT. The level of this enzyme appears to be a suitable diagnostic tool for dosimetric applications. Another notable enzyme activation involves poly(adenosine diphosphate-ribose) polymerase, a key regulator of cell death-survival transcriptional programs. It is activated significantly by Photofrin or Foscan PDT (170). This induction occurred 30 min after PDT. followed by further increases in enzyme levels by 2 h.
Few biochemical studies of isolated cell organelles were performed to assess the intracellular Foscan PDT effects. Both Type I and II effects were noted in isolated rat mitochondria. The PDT treated mitochondria had a reduced membrane potential and impaired Ca2+ uptake (171). Similarly, only limited information is available for the impact of Foscan PDT on cell adhesion. Post-PDT cell removal by trypsinization was found to depend on the PS type and the fluence rate (172).
Sometimes laser hypothermia is compared with PDT as both use the same application principles. However, their modes of action are different, especially with regard to collagen damage. A comparative study clearly showed no effect of mTHPC PDT on collagen-related heat-shock protein expression (173). Likewise HpD PDT had no effect; only riboflavin PDT gave an upregulation of the HSP47 heat-shock protein (174). This supports the nation that PDT "spares" the connective tissue. In this context Mitra et al. developed an interesting model system that utilized green fluorescent protein (GFP) as an analytical tool of the PDT effect. They transfected EMT6 cells with a plasmid containing the gene for GFP driven by an hsp70 promoter (175). mTHPC induced a concentration dependent GFP expression in cells and in a rat model.
Cell death. Ultimately the aim of PDT is the death of unwanted cells and tissues in the body. The type and degree of cell mortality depends on the various factors involved in PDT and typically two types of cell death are considered. Necrosis is a rapid form of cell death, whereby the cell organelles are destroyed and the plasma membrane ruptures. This results in inflammation and a release of the intracellular materials. In contrast, apoptosis is characterized by a shrinking of the cell and blebbing of the plasma membrane. The cell organelle and plasma membrane structure are maintained for a considerable time. Ultimately apoptosis results in vitro in fragmentation into vesicles while in the body the cell remnants are taken up by phagocytes without inflammation. Apoptosis is a highly controlled process and involves the transcriptional activation of specific genes, DNA degradation and caspase activation. By now, other forms of cell death, e.g. programmed necrosis, mitotic cell death, autophagy and lysosomal death pathways have been described. In most cases PDT related studies focus on the first two types. However, Foscan has been implicated in autophagy as well (176). Necrosis and apoptosis can often be induced at the same time and the exact mode of cell death then depends on the PS, cell type, oxygen supply and experimental conditions. For basic reviews on cell death in PDT see the following articles; (162,177,178). While evidence for the signaling role of reactive oxygen species is mounting (179) it remains an open question to what extent the various effects are directly related to PDT or if they are more general effects resulting from cell damage.
Both necrosis and apoptosis effects are associated with the action of Temoporfin, One indication is that low levels of post-treatment energy metabolism favor further cell decay (180). A lack of glucose in the incubating medium significantly increased the extent of necrosis (181). Bourré et al. undertook a first in vitro study to quantify the apoptotic effect of Foscan. ALA (proto IX) and, more so mTHPC, were found to be strong apoptotic inducers. The maximal apoptosis enrichment factor, a measure of this effect, depended on the PS and cell type (182). Interestingly, apoptosis inhibitors had only slight effects on the PDT efficacy indicating that necrosis and apoptosis might be linked and share common initiation pathways. This requires active caspases and these results would indicate that apoptosis inhibition reorients cells to necrosis (183). A related study investigated the role of two genes, p53 a tumor suppressor gene important for cellular stress response and ATM, a gene mutated in patients suffering from ataxia telangiectasia. mTHPC PDT did kill the cells with these mutations quite efficiently through necrosis. Apoptosis appeared to be more a long-term process that depends to some extent on the p53 and ATM function (184). A detailed assessment of the expression of caspase-3, caspase-7 and cleaved poly-ADPribose polymerase 1 in Foscan treated cells has been given by Bressenot et al. (185).
mTHPC resulted in a much better apoptotic effect than merocyanine 540 in murine myeloid leukemia cells and cleaved the DNA to very small 150 base pair fragments (186). Induced apoptosis was observed in an intracranial tumor model (187) and in human colon adenocarcinomas (116). The action of some cationic PS can be counteracted to some extent through antiapoptotic protocols. A study of mouse fibrosarcoid L929 cells with an overexpressed protooncogene (bcl-2), which protects cells against apotogenic stress, showed no evidence for a positive or negative effect on the PDT results (188). However, for murine leukemia cells it was clearly shown that the first detectable effect of several PS, including mTHPC, is the loss of activity of the antiapoptotic protein Bcl-2, followed by cyt c release and caspase-3 activation (189). A detailed study using MCF-7 cells addressed the question whether the post PDT apoptotic effects originated from the ER/Golgi or the mitochondria. The study clearly showed localization of Foscan in the ER and Golgi. After 3 h leakage from the Golgi was observed and prolonged incubation times showed photo-damage to Bcl-2 in the cell extract, but not in the mitochondrial fraction. Likewise caspase-7 and -6 activation was observed indicating that localization in the ER enhances the photoactivation of the caspase-7 apoptotic pathway (190).
An intriguing treatment possibility is the coadministration of apoptosis inducing drugs. One such possibility to increase the tumor selectivity is the presence of the TAT-RasGAP317-326 peptide which sensitizes tumor cells to cytostatic agents. A comparison of H-meso-1 and human fibroblast cell cultures showed that, indeed, the PDT effect is enhanced by peptide administration but only in the H-meso-1 cells. This effect occurs only at low Temoporfin concentrations (0.04 µg mL-1). No such effect was found with 0.10 µg mL-1 Foscan (191). Thus, this effect is dose dependent. Another important effect in tissues is the bystander effect, i.e. the degree to which a dead cell results in death of a neighbor (192). A model study using MDCK II cells indicated that this bystander effect was significantly lower for mTHPP than for Photofrin or ALA PDT and treatment with metabolic inhibitors (193).
Any phototreatment has the potential to affect DNA at the molecular level through photochemical reactions. This occurs either through direct absorption by nucleobases or through photosensitized reactions involving endogenous PS (natural porphyrins and flavins) or the drug themselves. DNA is highly susceptible to singlet oxygen, resulting in single strand breaks and free radicals. ALA and porphyrin based PDT clearly can result in DNA damage (194). However, while this probably does not give lethal effects the mutagenic potential depends on the cell type and the effectivity of the repair mechanisms (195). No evidence was found for Temoporfin genotoxicity using a simple Drosophila melanogaster model (196). Likewise no DNA damage was found in in vitro tests with, human leukemia cells (197). This study revealed DNA damage upon PDT with HpD or methylene blue, indicating quite different effects of various PS. Use of murine glioblastoma cells showed that mTHPC PDT does induce DNA damage in a dose-dependent manner but that treated cells are able to repair this damage (198).
A different issue is the relative susceptibility of different tissues and cell types to PDT. A comparative study of microvascular endothelial cells, fibroblasts and tumor cells indicated that endothelial cells are not per se more sensitive than other cell types (199). Only continued drug uptake after 24 h resulted in increased photosensitivity under certain conditions. PDT also does not induce any resistance to chemo or radiotherapy or subsequent cycles of PDT in human breast cancer cells (200). DNA mismatch repair-deficient cells are known to be resistant to many chemotherapeutic drugs and to radiotherapy, and have the potential of rapidly acquiring additional mutations leading to tumor progression. Using in vitro cell lines either proficient or deficient in DNA mismatch repair no differences were found between the cell lines upon Foscan PDT. Thus, PDT appears to not induce loss of DNA mismatch repair nor does loss of mismatch repair result in resistance to PDT (201). But how do all these mechanisms lead to tumor destruction? Tumor eradication requires and relies not only on effects at the molecular level, i.e. individual cell death, but even more so involves more "indirect" effects such as vascular and immune system effects.
Direct tumor cell effects. This might be considered the first target of PDT. However, studies with several PS (mostly with Photofrin) showed that while PDT results in a decrease in the number of tumor cells, the overall effect is not enough for tumor eradication. This is a result of the often inhomogenous PS distribution, of photobleaching and the requirement for oxygen, which limits the utility of PDT in hypoxic tissue. The latter may be overcome by using lower light fluence rates or fractionated light delivery.
Vascular effects. Almost from the advent of PDT studies, it was clear that vascular effects impact long-term tumor control. In general these effects are associated with vascular damage that occurs after the PDT treatment and result in tumor hypoxia. Depending on the PS various mechanisms are involved. These include vessel constriction and vascular leakage, mostly related to platelet activation and aggregation. Early studies with chlorins noted that the primary target of PDT is often the tumor vasculature (202,203). Although differences exist in the exact distribution of Hp and mTHPC the latter seems to act in a more indirect manner on the blood capillaries (69). Animal models showed that the exact nature of the PDT effect depends on the pharmacokinetics. Thus, often an "early" response can be differentiated from a later effect in tissue (204). While tumor and plasma drug levels often do not correlate with PDT efficacy the Foscan concentration in leukocytes does. This indicates that leukocytes might play a role in the vascular damage process (205). For example, a detailed study of the pharmacokinetics of human tumor xenografts in mice showed that plasma levels of mTHPC decrease exponentially with time while the tumor drug levels remained at maximum for 48 h. At 3 h postadministration the drug was located in the blood vessels and only later distributed in the rest of the tumor. Illumination at 3 h resulted in a 100% cure rate while illumination at 48 h resulted in tumor regrowth and only 10% cure. Thus, the early vascular response appears to be responsible for optimum Foscan PDT response (206).
Immune system effects. The immune system plays a significant role in the success of any PDT treatment. Based on initial studies with Photofrin it is now accepted that PDT can result in the generation of antitumor inflammatory cells and can lead to a persistent antitumor immune response. The advantage of this response is that it can be elicited by PDT even when not all cells are killed directly. There are even indications that Photofrin PDT can be used to generate antitumor vaccines (207). The immune system effect involves complex signaling pathways and relies on cytokines, growth factors and neutrophils all of which are significantly affected by PDT (160,208).
Secondary effects of the oxidative stress imposed by PS include vascular damage, ischemia-reperfusion injury, cytolytic activity of inflammatory cells and tumor-sensitized immune reactions (209). The latter was investigated through adjuvant administration of mycobacterium cell-wall extract, a nonspecific immunostimulant that gives a local inflammatory response associated with antitumor activity (210). Studies of a mammary sarcoma revealed that the PDT effect of various PS including mTHPC could be increased by a single treatment of this extract directly after light treatment. Mouse models clearly showed that Photofrin or Foscan PDT of solid tumors results in a strong and lasting induction of systemic neutrophils mediated by complement activation (211). More detailed studies revealed an increase in neutrophilic myeloperoxidase and an expression of MHC class II molecules in PDT-treated tumors. The most important regulatory inflammatory cytokine appears to be IL-1ß, which inactivation diminished the PDT cure rate (212).
Similar to other PS mTHPC PDT activates macrophage-like cells (213). A detailed study of a model system revealed a light-energy dependent production of tumor necrosis factor TNF-a and a fluence dependent release of NO in U937ø cells. Fosean treatment of rat liver tumors showed that while PDT effectively necrosed the tumor tissue it had no effect on the growth of nonilluminated tumor areas in the same liver. PDT did not result in an increase of T cell numbers, natural killer (NK) cells or macrophages in nonilluminated tumors. Thus, no PDT-induced systemic immune response was observed in this system (214).
IN VITRO TESTS AND ANIMAL MODELS
In vitro tests
The photodynamic action of mTHPC became clear quickly after its synthesis, for example in a cost-benefit analysis comparing it with other PS (44,215). Naturally, the early tests included mostly in vitro tests of various cell lines. A survey of cell lines used for studies with Fosean, i.e. simple solutions of mTHPC, is given in Table 1, which also gives a brief description of the main results.
Initial tests with murine leukemic cells (216) or Chinese hamster lung fibroblasts (80,113) indicated that Temoporfin would be a better PS than Photofrin. This was substantiated by studies of human colorectal adenocarcinoma grafted subcutaneously in mice (216). Next were studies with human breast cancer cell cultures that indicated almost a total cell killing at nontoxic drug concentrations (217). Other studies indicated that lower light doses might be better (100) and experiments addressed the role of reactive oxygen scavengers (158), the beneficial effect of lower fluence rates (218), activation of phagocytic capacity (213) or the biodistribution of the drug with time (219,220), to name only a few. Initial studies on the effect of PDT on cell adhesion have also been reported (172). A study of the intracellular aggregation processes in MCF-7 cells indicated progressive sensitizer aggregation with increasing incubation time. Fluorescence lifetime imaging measurements showed a substantial decrease in the lifetime of mTHPC fluorescence at 24 h compared to 3 h. In addition, the intracellular localization changed from a diffuse pattern at short incubation times to a punctiform pattern at 24 h. Thus, the loss of photosensitizing efficiency at higher mTHPC concentrations is probably due to self-quenching of the triplet states of the PS (221).
mTHPC ticked more of the boxes of an optimum PS than other PS available in the early nineties. A comparison of its effect in human colon adenocarcinoma with that of BpD showed that it was more efficient by a factor of 20 (222). However, even the then available pegylated mTHPC derivatives (see below) appeared to be better suited than the unpegylated form (223). For an ovarian cancer cell line it was shown that the cytostatic cytotoxicity of mTHPC is comparable to that of cisplatin and only one order of magnitude below that of taxol (224). Similarly, Temoporfin was superior to merocyanin 540 (225) and HpD (166) in nasopharyngeal cells. In vitro studies also indicated the utility of PDT to perhaps suppress hematogenous metastasis (229). Cell studies indicated a rapid onset of apoptosis in such cells (227). Naturally, Foscan is not always the best PS for everything. Studies on the photoinduced hemolysis of red blood cells showed that cationic and hydrophobic phthalocyanines have improved activity compared to mTHPC and other PS (228).
Experiments with human breast cancer cells expressing a multidrug resistance phenotype showed that both the resistant and normal cancer cells showed a similar uptake profile for mTHPC. However, the drug and light dose that resulted in 50% cytotoxicity in the "normal" cell gave 85% cytotoxicity in the drug resistant cell (229,230). Such an effect has been noted frequently with PDT. Thus far most studies indicate that this is the result of a different localization of the drugs. For the MCF-7 cell line a more pronounced localization in lysosomes in the drug resistant strain was discussed (229,230). In vitro tests have also been performed with freshly prepared human gynecological tumors (breast, ovary and ascites) and indicated that individual treatment protocols might be required (231). Cell tests also indicated the utility of Foscan (and Foslip) for perihilar cholangiocarcinoma. Treatment of two biliary cancer cell lines gave a high phototoxic potential (LD90 600 ng mL-1 and irradiation with 1.5 J cm-2 (660 ± 10 nm). Both formulations gave similar localizations and similar PDT effects (232,233).
Other studies investigated the combined use of PDT and radiotherapy in human breast cancer cells (234), or effects on resistance against chemo or radiotherapy, which is not induced by PDT (200). Two cell lines resistant against poly-Hp or PPC were prepared through radiation. However, they showed no cross-resistance against mTHPC PDT (235). The results indicated that the mode of resistance depends to some extent on the nature of the PS.
For future applications it is also important to know the ability of neurons to survive. Here an interesting in vitro study compared the stability of neurons, satellite glia and human adenocarcinoma cells (236). The latter two were significantly more susceptible to Foscan PDT than the neurons. Even more importantly, Wright et al. identified conditions where no effect on the neurons was observed but the other two were killed. Thus, neurons in culture can survive mTHPC PDT under conditions sufficient to kill tumor cells and other nervous system cells. An intriguing model, based on the use of isolated nerve cells from a crayfish was developed by Uzdensky et al. (237). It allows the continuous recording of PDT-induced electrophysiological and biochemical properties. mTHPC was found to be highly effective in the nM range to abolish neuronal activity. It was much more effective than many chlorin e6 derivatives.
Individual cell phenotypes exhibit significantly diverse drug uptake and phototoxicity. A comparison of nine different biliary tract cancer cell lines identified two groups of cell lines with either high or low susceptibility to Foscan PDT (238). The high susceptibility ones were characterized by low cytokeratin-19, high vimentin and a high proliferative phenotype. This indicates the potential to identify suitable markers for the optimization of clinical cholangiocarcinoma treatment. Other related cell line studies are discussed below in the related sections on animal and clinical studies.
Many animal models have been employed over the years. The first such report on hydroporphyrins was published by Bonnett et al. in 1989 (29). As in many other cases the use of animal models to predict effects in humans is problematic. Many studies have pointed out the varying biodistribution of Temoporfin in different animal species (137,239). Likewise, sometimes similar distribution but different photophysics are observed (240). In addition, such models are only of limited use for predicting the best conditions for clinical purposes. For example, a comparison of three different xenografts in mice showed different pharmacokinetics for the same drug/light dose (241). Thus, these systems can only serve to establish the basic conditions for further tests. Even with limited goals in mind the choice of the right animal model is critical for the utility of the in vivo tests. Here, orthotopic tumor models present the closest resemblance to the clinical situation with regard to PDT and a concise analysis of the PDT relevant models has been given by D'Hallewin et al. (242).
Table 2 summarizes most of the models and techniques used with mTHPC and related compounds. The following sections give only a brief overview on selected animal studies with Temoporfin.
Skin. Many studies on squamous cell carcinoma used a SCC hamster model (121,127). Although obvious from a chemical viewpoint, the same model was used to determine the range of ? = 647.5-652.5 nm as the most effective wavelength range for PDT (243). A determination of the threshold of muscle damage (1-3J) during interstitial PDT (IPDT) showed that 85% of the SCC tumor could still be destroyed under these conditions (244). A comparison with BpD showed that this drug localizes to a smaller extent in the smooth muscle and is cleared more rapidly indicating some advantages for using BpD (245). However, a comparison of the pharmacodynamics of normal hamster and human mucosa indicated that this model is limited in its use for clinical predictions but has value for preclinical screenings (240). Earlier localization studies based on fluorescence spectroscopy were confirmed using 14 C-labeled mTHPC (246). Skin cancer offers itself to topical applications. Thus, an initial study of a mTHPC thermogel formulation after topical application on hairless SKH-1 mice bearing nonmelanoma skin carcinomas showed good tumor: tissue selectivity (247). The highest PS concentration in tumor was observed 6 h after drug application while no drug was detected (248) in normal tissues or plasma after topical drug application. A study using a hairless mice skin papilloma model indicated that HpD can give a slightly higher tumor/normal skin tissue ratio than mTHPC, but the latter reached its peak at a lower dose (249). The related carcinoma cells showed lower but similar tumor/normal skin ratio for both PS (250).
Head & neck. Several animal model studies were performed for H&N cancers (251). Human oral SCC cells xenografted in mice gave a good response to mTHPC (252). Analysis of a series of human keratinocyte cell lines derived from human SCC gave interesting results with regard to the regulation of invasion promoting tumor factors. Exposure to sublethal PDT doses showed that both active and latent MMP-2 and MMP-9 were down-regulated in some cell lines (UP, VB6) while H376 showed an increase in active MMP-2 (253). Thus, while there is clearly potential for using this for predicting PDT outcomes the divergent results for different cell lines indicate the need for further studies. In terms of detection one study, with cat H&N SCC, showed that the vascular effects of PDT could be followed with power Doppler ultrasonography (254).
Chest. Breast cancer carcinoma implanted in mice was effectively treated with mTHPC and the chlorin was much more effective than the porphyrin mTHPP (120). A comparison with Photofrin for treatment of a murine cancer clearly showed mTHPC to be the better PDT agent and to have a more rapid skin clearance (255). The same PDT effect could be obtained with lower light doses when the drug was administered together with the bioreductive agent mitomycin C (202). This animal model also revealed the possibility to improve the PDT effect through light fractionation (152). Use of labeled mTHPC showed that the drug concentration in the tumor was highest after 24-48 h (106). Surprisingly, the best tumor response was achieved 1-3 h after drug administration when the drug tumor concentration had not yet reached its highest value. Bacillus Calmette-Guérin (BCG) vaccine administration was found to enhance the cure Tate for mouse mammary carcinoma. Interestingly, this effect was still observed when the BCG injection was given 7 days after the PDT treatment, i.e. it effects events involved in preventing tumor recurrence (256).
Early studies with human malignant mesothelioma implanted in nude mice established the basic therapeutic conditions (148,149) and also indicated better effects with mTHPC-MDS000 (257). For example, these studies showed the importance of the drug-light interval and the light dose (149). Detailed studies of a human mesothelioma xenograft showed a marked difference between tumor or skin drug level and PDT effect and between tumor drug level and optimum drug-light interval (258). Preclinical studies showed a strong dependence of the PDT effect on the drug-light interval but not the fluence rate (259). In addition, the PDT effect could be enhanced by an increase in tumor oxygenation through carbogen breathing or nicotinamide injection.
IPDT was shown to give zones of necrosis in the normal lung that heal safely, indicating potential for PDT treatment of lung cancers (260). An endobronchial study with pigs showed that PDT of the trachea results in atrophy and acute inflammation of the epithelium and the submucosal glands. Using fluences of 50 J cm-2 or less, full recovery occurred in 14 days (262). Initial pharmacokinetic data indicated that the drug level was the same in the trachea at Day 6 and 20. Nevertheless, significant interanimal variation was found indicating the necessity of optimum dosimetry. A comparison of laser photocoagulation and IPDT of normal pig lung parenchyma showed that both techniques offer good potential, with the latter giving better healing (262). An attempt to use intraoperative PDT (IOPDT) of the chest cavity for malignant pleural mesothelioma failed. All rats treated with pneumonectomy followed by spherical PDT died within 48 h (263). A comparison of Fosean and Verteprofin intracavitary PDT on local malignant mesothelioma in the mediastinum of syngenic rats showed that both PS can be used. The PDT effect of verteporfin was better (264).
Similar results were obtained with papillomavirus-induced tumors in rabbits (297). The canine laryngeal edema was used as a model to define safety standards for drug use within the airways (265). Intraperitoneal PDT (IPPDT) of rats was used to establish the basic toxicity profile, which was similar for both mTPHC and Photofrin (150). A comparison of red and green light illumination indicates the latter might be better for TPPDT treatment, however, it is limited by the ineffective light distribution in the peritoneum (151). Nevertheless, IPPDT results were better than i.v. applications (266).
Induced adenocarcinoma was used to determine the tissue distribution in rats and indicated a significant difference between tumor and muscle tissue (267). This early study indicated that abdominal or thoracic treatment might be better performed with longer drug-light intervals. Lewis lung carcinoma was studied in a mouse model and gave initially good results, inhibited tumor growth and prolonged mice survival. However, tumor growth was regained after 9 days (268).
Gastrointestinal tract. A mouse model showed the utility of adjuvant IOPDT (AIOPDT) for colon cancer (269). Application of 0.3 mg kg-1 mTHPC, 3 days incubation followed by total tumor resection and then followed by illumination (? = 652 nm, 5 J cm-2) gave an increase of the time to tumor recurrence from 11.4 to 33.3 days. Likewise, colon adenocarcinoma induced in the rat liver was used to study the potential for PDT on liver metastases. Different pharmacokinetics were found for the liver and tumor tissue with the former rapidly being cleared of the drug. PDT under standard conditions gave 87% tumor free animals after 28 days indicating that this modality might be able to induce complete tumor remission of liver tumors (270). Fractionated light application or lower light fluences improved the PDT effect (156). In another study with murine colorectal cancer implanted mice it was shown that the highest tumontissue ratios after 4 days were found for the small intestine, liver and skeletal muscle (134). This animal model was used as a general test bed for PDT assessment (271) and for AIOPDT (45). A study of healthy hamsters showed highest drug levels in the gastric and duodenal mucosa and acinar pancreas after 2-4 days (272). Except for the duodenum all lesions healed safely. Similarly, intravesical PDT in normal mice resulted in moderate to severe functional bladder damage with full recovery within a few weeks (273). The utility of treating pancreatic cancer in animals was shown with a hamster model (274).
One of the first animal studies related to esophageal cancer used a sheep model (275). A test of mucosal ablation through PDT in normal animals revealed significant complications in the esophagus following illumination with green light (514 nm) especially at high doses (276). Blue light irradiation (412 nm) resulted in significantly less damage. Clearly treatment of the precursor lesions of esophagus adenocarcinoma would be an optimum treatment choice. However, here an appropriate animal model was lacking. A thorough study of sheep treated with mTHPC showed that this might serve as such a model (277). The plasma pharmacokinetics were similar in sheep and humans, with Fosean reaching its maximum at 10 h post i.v. Two days after injection it was mainly distributed in the lamina propria, followed by a penetration into the epithelium. The sensitivity of both sheep and human tissue to mTHPC PDT was similar. Use of rodents as models for esophageal cancer is problematic as they do not allow a study of stricture side-effects. Thus far, pigs might be the best choice for related PDT studies (278).
Ovary. A rat model for the study of peritoneal cancer gave a promising tumontissue ratio of greater than four (267). Likewise, both superficial irradiation and IPDT of mTHPC treated hypercalcémic ovary small cell carcinoma in a mouse xenograft model gave good results (279). A NuTu-19 ovarian cancer rat model was developed and used for testing debulking techniques. Use of mTHPC-PEG gave a very high (40 ± 12) tumor/tissue ratio after 8 days (280).
Brain. Most studies in this area have focused on ALA PDT and its effect on the blood brain barrier. Initial tests with Temoporfin in this area indicated less skin toxicity than other PS and effective cytotoxicity at a wavelength of 652 nm and light doses of up to 20 J cm-2. The tumor/normal brain tissue ratio was 20:1 (120,219). A first study of the pharmacokinetics of 14 C-labeled mTHPC was performed using a rat glioma model (281). A rabbit model showed induced apoptosis as a result of several PS (187). A comparison of intratumoral administration and systemic one showed that both result in complete tumor localization in a C6 rat model. However, intratumoral administration gave an optimum drug dose already after 4 h postadministration (282).
Other. A first rat study showed that the adrenal gland can take up PS and indicated the possibility for treating medullary neoplasia (283). Interestingly, only steroid synthesizing cells of the adrenal gland exhibited an intense photosensitizer-induced fluorescence after administration (284). Treatment of the prostate was evaluated in beagles and showed a good localization of the drug in the prostate within 2-3 days. Significant areas of glandular tissue could be necrosed with good healing (285) although regeneration of urethral epithelium could take up to 3-4 days (286). Various Temoporfin formulations were evaluated for the treatment of choroidal neovascularization associated with age-related macular degeneration (287). Possible side effects of IOPDT on blood vessels and nerves were assessed in rabbits (288). PDT at high drug concentrations (0.3 mg kg-1) and light doses (20 J cm-2) led to necrosis of all illuminated tissue. At lower concentrations the blood vessels showed severe edema, media hyperplasia or loosening of the endothelial layer, but no damage of the vessel wall or rupture was observed. Nerve cells underwent 75% demyelization, however, without clinical symptoms. Thus IOPDT was suggested as a safe treatment option.
Only few specific studies have addressed veterinary applications of PDT. This is surprising as the regulatory process is less involved and the related drug development cheaper. With the increasing willingness of individuals to spend significant amounts of money on pet health care this area offers potential for industry. One study investigated the biodistribution of mTHPC in cats and found a situation similar to other species and no clinical or pathological changes attributable to the drug (289). Likewise, the time necessary for maximal accumulation in various feline tissues has been determined (290). Thus, Fosean PDT might be a good treatment protocol for feline neoplasm, e.g. SCC. Here, mTHPC-LIP was found to be superior to standard mTHPC (291). An in vivo study with 18 cats showed a complete remission (CR) of 75% after 1 year (292). The only application in the equestrian area was the test of a novel light diffuser during the treatment of equine sarcoids (293).
Apart from Photofrin, Foscan is the only other photosensitizer approved for use in systemic cancer therapy. Various derivatives of ALA (e.g. Levulan and Metvix) have also received approval as sensitizers for topical applications, meaning they are at present limited to skin cancers but with a high degree of success (294). Additionally, Verteporfin must be mentioned here. Developed as a photosensitizer for light-activated treatments it was successfully used for the treatment of age-related macular degeneration (295,296). Excellent overviews of recent advances in the clinical field concerning these established PS were published in 2004 (297,298) and newer treatises are available as well (299,300). The clinical impact of mTHPC and other PS in the treatment of gynecological diseases and head & neck cancer has been discussed (301-303). Reviews on skin cancer (basal cell carcinoma [BCC]) (304) as well as gastrointestinal and esophageal (305-308). brain (309), prostate (9,310), pancreas (311), breast (312), urological malignancies in general (313,314) and new treatment options thereof (315) and gynecological (316) malignancies show that these cancers can be treated with a reasonable degree of success with Temoporfin. A review by Konan et al. has surveyed the drug delivery and formulation aspects of drugs used for PDT (143). Table 3 summarizes details about the various clinical studies available for Foscan and related drugs and formulations.
A first comprehensive meta-analysis of the available data on PDT for most applications has just been published by Fayter et al. (317). They analyzed 88 trials reported in 143 publications and clearly outlined the problems associated with the currently available data. Their analysis indicated good prospects for PDT for actinic keratosis and Bowen's disease. Likewise PDT of BCC might be superior to surgery or cryotherapy due to better cosmetic outcomes. Similar indications for Barrett's esophagus were promising but no conclusions could be made for esophageal cancer. Limited evidence was noted for applications in lung, brain and H&N cancer and cholangiocarcinoma. Overall, no significant adverse sideeffects were noted. The authors noted as problematic the absence of large scale randomized control trials and noted limitations in the quality of life and resource outcome reporting.
Obviously photosensitivity is a major concern for lightactivated drugs. Several studies have indicated that mTHPC results in less photosensitivity than Photofrin (132). Still, the major problem involving mTHPC PDT is skin photosensitivity in the few weeks postdrug administration. Injuries resulting from this light hypersensitivity are generally minimized by following medical advice. Thus, burn-related incidents are rarely seen in PDT patients; those that are observed mostly occur when medical advice is ignored. However, in isolated cases, injuries have been received during treatment in the operating theater where devices such as the pulse oximeter have been a source of causing burns to the victim (318). To reduce the risk to patients several types of creams have been tested on patients and, for example, dark cover cream promises acceptable protection (319). Other side effects are mild to moderate pain in the treated area. More specific, but also rarer, are side effects related to specific cancer treatment protocols, e.g. for esophageal cancer (vide infra).
In 2000, a report of post PDT partial sickness burn occurring in 6 of 12 patients was challenged by the Foscan producers and created a lively debate in BMJ. As then no similar reports have been made and it appears to have been the result of the drug application procedure. The furor created by this report and its subsequent discussion in the scientific literature and (financial) mass media is an illuminating example for the interrelationship of financial interests, research, scientific publication ethics and news spin (319).
Head & neck
Foscan was first approved in 2001 in Europe for the treatment of advanced H&N cancer. There is a relatively high morbidity and cost associated with standard head and neck mucosal squamous cell cancer treatment. Typically, therapy involves a combination of radical surgery, radiotherapy and chemotherapy. Radiotherapy to the head and neck area commonly causes a wide range of debilitating side effects, such as xerostomia, mucositis, loss of taste and loss of smell (320). In severe cases, malignancies have sometimes been found unsuitable for any treatment because of the imminent loss of functionality. The treatment of squamous cell carcinoma (SCC) of the soft palate is an example (321); however, there are many more. While multidisciplinary H&N cancer care is well established (322), PDT has been slow to gain an entry (302). In an overview from 1997 on multitreatment approaches it was mentioned only as an emerging technique (323). More recent overviews of this area are available (324-326).
Nevertheless, while it was initially only used for palliation in inoperative patients with advanced stage H&N SCC, PDT quickly was used with a curative intent for the treatment of small localized and recurrent tumors and premalignant lesions. Initial clinical studies were promising and showed that PDT is suitable for the treatment of early (CIS, T1) carcinomas and of small T2/T3 superficial carcinomas ( <0.5 cm) (327). Likewise, fluorescence guided resection was quickly shown to be a feasible option (328). In situ dosimetry during oral cavity illumination is indicated and should be required as the basis for light dose prescription in H&N PDT (329).
The introduction of mTHPC PDT, even as an adjuvant treatment, has offered a new possibility of tumor clearance and possesses the advantage over the related use of ALA or Photofrin, in that much lower drug and light doses are required (330,331). The length of time skin remains photosensitive is halved while deeper tissue penetration is achieved. The pharmacokinetics of mTHPC were studied by Braichotte et al. in early clinical tests on patients with SCC in the oral cavity using fluorescence spectroscopy and a noninvasive optical fiber (332) and later in a hamster model (240). The measurements were performed at 420 and 520 nm and showed encouraging results for oral SCC at both wavelengths. A more recent trial using standard conditions with longer mean follow-up times (37 months) of early SCC in the oral cavity resulted in a total clearance of 86%, which underlines the usefulness of mTHPC for these and similar cancers (333). The complete response rates for mTHPC PDT are similar to those of surgery and/or chemoradiotherapy but with the advantage of a lower morbidity and better cosmetic results (331,333,334).
The first studies on 17 H&N cancer patients (SCC, malignant melanoma and verrucous carcinoma) treated with different PS (15 Foscan, 1 ALA, 1 Photofrin) were published in 1995 and were encouraging (330). An early explicit trial including 20 cases of SCC and BCC confirmed the potential use of low light dose (5-10 J cm-2), and found the outcome of treatments at low light dose preferable as selectivity of necrosis of normal to cancer tissue was often higher (335). However, this only was found to be true for minor lesions. All cases of SCC showed complete response with a follow-up of 8-24 months. Lymph node metastasis was shown to be absent. Complete response of BCC was slightly lower (92%) with the remainder showing only partial reduction of the tumor. mTHPC-mediated PDT was found to be superior to that of Photofrin, ALA and BPD. Additional medication (e.g. antibiotics or pain reliever) after irradiation was unnecessary as side effects were minimal. Side effects only occurred because of oppositional behavior to medical advice (burns due to exposure to open daylight during the first weeks after treatment).
But do isolated tumors and "field change" tumors (multiple lesions at one anatomical site) respond equally well to irradiation? Clinical trials performed by Bown's group on various oral SCC's indicated that isolated lesions gave the best PDT response whilst cases of "field change" showed less photoreaction and often incomplete necrosis of cancer tissue (336). Repeated treatment at higher light doses sometimes led to an improved outcome. Still, evaluation of a variation of the light dose between 5 J cm-2 and the recommended 20 J cm-2 suggested that lower light doses might very well be sufficient for smaller isolated lesions.
In early 2001, the possibility of treating head and neck cancer with mTHPC PDT came to be known more broadly as two complete Phase II studies showed encouraging results (337,338). Kübler et al. examined 25 patients with primary lip SCC and showed a 96% complete response after 12 weeks (337). A brief report on the treatment of lip cancer was also published in 1995 (339) and followed by a case report indicating good cosmetic results (340). About this time, Scotia sought regulatory approval in the USA and Europe for palliative use of Temoporfin in head and neck malignancies. Extensive clinical research in a Phase III study had confirmed an improved quality-of-life benefit in 53% of patients with incurable cases of recurrent/refractory SCC of the head and neck (341). Other clinical studies have been reported as well and indicated good results with patients for whom all other treatment options had been exhausted (342,343).
The efficacy of mTHPC in the primary treatment of a wide range of head and neck mucosal SCC was reinforced in 2003 (344). Although this study encompassed a rather heterogenous group of patients with oral cavity, nasal, oropharyngeal, hypopharyngeal and laryngeal malignancies, some of which had already received radiotherapy, the results were promising. A CR to primary treatment was seen in 19 of 21 patients (90%) in tumors ranging in stage from T1 to T3. Treatment of laryngeal cancer, recurrent postradical radiotherapy, however, was less successful, with only 25% of patients showing CR. This study concluded that while the complete response rates are similar to those of surgery and chemoradiotherapy, PDT had a lower morbidity rate. There is also the ability to retreat or treat uncompromised areas with standard techniques in the event of a recurrence. Prime sites for PDT when treating head and neck mucosal SCC were established to superficial looking (around 5 mm depth) floor of mouth, buccal pouch, lip, lateral pharyngeal wall/tonsil, soft palate and posterior pharyngeal wall carcinomas. Larger studies of BCC skin cancer in the H&N region with Foscan indicated 97% CR after 8 weeks and a 100% CR with low doses of Foscan (345). Thus, H&N PDT appears to be one area where PDT significantly improved on other treatment approaches (346). Foscan has been used clinically for the treatment of benign neoplasms in the H&N as well. All cases showed a significant reduction in the volume of abnormal tissue; better results were observed with lymphatic malformations compared to venous ones (347). Other studies involved use of a new light applicator for nasopharyngal cancer (348,349).
A contemporary Dutch study analyzed the results of Foscan treatment of early stage oral cavity and oropharynx neoplasms in 170 patients with 226 lesions (350). The very promising results gave an overall response rate of 91% and a CR of 71%. However, clearly the selection of the patients is of critical importance for the outcome of the treatment. A thorough subgroup analysis revealed that some sites (e.g. oral tongue and floor of mouth) are more suited to PDT treatment than others (e.g. alveolar process, soft palate). Unfortunately, the latter are the areas that are less suited for conventional surgical resection. Nevertheless, the success rate is promising, side effects were acceptable and the PDT effect was independent of the T stage for invasion depths < 5 mm. Overall, Fosean PDT appears to be a suitable first treatment for areas that would have functional problems after resection. A recent multicenter study of Foscan use for H&N SCC showed complete response in 19 of 39 treated patients with a significantly increased median survival (37 months compared to 7.4 months) (351). Mild-to-moderate side-effects were observed, the most significant ones related to photosensitivity, pain and dysphagia. Foscan was the first PS to be investigated for its utility in H&N cancer in a multicenter study (352).
A second way to raise the effectiveness of treatment of large tumor sites was the advent of IPDT (353). IPDT involves the penetration of the cancer tissue with the optical fibers during irradiation to insure complete irradiation of the malignancy (354). Utilizing this modality on some recurring head and neck cancers has delivered some impressive results. Several patients, previously regarded as otherwise unsuitable for any further treatment, showed a complete response (11% after 10-60 months) after mTHPC PDT. Nevertheless, in some cases repeated PDT was necessary to reach this outcome. A recent, larger study with 68 patients with various deep-seated pathologies showed that ultrasound-guided IPDT was well tolerated and that image-guided PDT gave improved results. Quality-of-life assessments were found to be a good criterion for the results, especially since the clinical results vary for patients with the same disease (355). Optical guidance methods for PDT in this area are currently under development. One study explored the use of fluorescence differential path length spectroscopy for monitoring Foscan IPDT (356).
Similarly, the use of surgical palliation using PDT is becoming more developed for the treatment of end-stage head and neck cancer. An excellent overview on the current best practice of this modality has been given by Jerjes et al. (357). A case study reported Foscan PDT use for the treatment of cystic hygroma in a 6-month-old-patient (358). They also presented a case study which showed that the occurrence of carotid artery rupture in the treatment of peri-carotid disease can be reduced via endoluminal carotid stenting prior to PDT (359). Other areas of potential use include the hyoid. Chrondrosarcoma of the hyoid has been reported to be radioresistant and cannot effectively be treated with chemotherapy, which typically leaves hyoidectomy as the only option, resulting in disruption of speech, swallowing and respiration. A case study showed that IPDT can be used effectively for this treatment (360).
Practical applications also demand a cost-effectiveness analysis. An analytical model was developed for the UK market using a computerized cost-effectiveness model. It revealed that palliative mTHPC PDT used against advanced head and neck cancers not only resulted in an increase of life quality avoiding the common side effects of extensive palliative surgery or palliative chemotherapy but was also much more cost-effective than the other optional treatments or even nontreatment (361). This study also showed significant health gains. Of the three treatment strategies PDT gave 129 extra days of life compared with no treatment and extensive palliative surgery and 48 extra days of life compared to four cycles of palliative chemotherapy. This model was also used for Germany using the local cost data in 2005 and confirmed the results of the British study. Financial costs for PDT were 8761euro compared to 11 600 for four cycles of palliative chemotherapy (362).
Due to the accessibility by light skin cancer is a natural target for all PDT drugs (304). For a comprehensive clinical review on cutaneous malignancies see Allison et al. (363). Several in vitro and animal studies (249) were performed and established the principal effects of Temoporfin in this area. A pilot study using a gel formulation of mTHPC for topical treatment of BCC and Bowen's disease showed some response but was found to be inferior to both intravenous mTHPC PDT and topical PDT with ALA (364). Still, initial studies of the treatment of BCC (304) were promising with about 86% complete response (365). A slightly larger study optimized the drug-light interval and showed that light activation after 1 day gave the best results with 75% CR after 6 months (366). Even better results were observed in a larger study with 117 patients where an overall CR of 96.7% was reported (345). Overall, the clinical and cosmetic results are promising. Foscan has also been used in a case study to evaluate the utility of optical coherence tomography-guided PDT. Administration of a 0.05 mg kg-1 dose 2 days prior to tumor mapping followed by light treatment of the mapped area resulted in CR at 6 months (367). A recent review has addressed clinical treatment decisions for topical PDT in nonmelanoma skin cancers (368).
GI tract-esophagus and bronchi
The esophagus is often the site of second primary tumors occurring in patients suffering from SCC in the head and neck. PDT quickly became of interest for the relevant clinicians due to the possibility of endoscopic light delivery (305-308,369). Nevertheless, only a few groups were the driving force behind this obvious application in the early years (370). As mTHPC PDT already showed success in these areas, and as esophageal cancer had previously been treated with Photofrin® PDT, it was logical to test the effect of mTHPC PDT on esophageal SCC (371) or Barrett's esophagus (372). Preliminary studies (370) on the impact of treatment on patients with (second) primary SCC located in the esophagus or the bronchi showed success (373) and were confirmed in subsequent studies (374,375). For example, a total clearing rate of 84% in the treatment of early SCC in esophagus and bronchi was found after a mean follow-up of 15.3 months (376). With the assistance of fluorescence spectroscopy, an adjustment of the fluence rate to only 8-12 or 7-16 J cm-2, respectively, was possible. An analysis of the early studies in this area using various PS in the GI and aerodigestive tract was given by Radu et al. (371,374) and they discussed their experiences with PDT and endoscopic mucosal resection in Switzerland in detail (275).
Experiments performed by Braichotte et al. on oral SCC were extended into other treatment sites in patients such as the esophagus (377) and bronchi (378). The results showed that while there was a direct correlation of photosensitizer accumulation (as detected by fluorescence spectroscopy) to PDT response in the tumor, the efficacy between patients varied largely. This is largely due to each patient having an individual pharmacokinetic response and rate of metabolism for the same drug-time level. Thus, the efficacy of PDT in the esophageal and bronchial SCC can be improved by prior monitoring of the accumulation of mTHPC in the tumor cells and before applying the correct light dosage. Zellweger et al. demonstrated that this is indeed possible in a study with five patients and avoids to a certain extent over- or underirradiation, hence increasing total response rate and abating side effects (379). However, due to the difficulty of endoscopic measurements, fluorescence measurement of the oral cavity was recommended as the ideal methodology. Indeed, it was shown that intrapatient fluctuations in oral measurements were two to three times smaller than in endoscopic procedures, thus being more reliable.
Light dosimetry is especially important in esophageal treatments (380). To facilitate endoscopic irradiation in esophageal PDT, a through-the-scope balloon applicator was proposed and tested on a small number of patients who underwent either mTHPC or ALA PDT (381). In the bronchi, the complex and elaborate architecture of the tracheobronchial tree leads to less accurate delivery. Consequently, the risk of recurrences due to probable undertreatment is enhanced for this site. But at least in early noninvasive tumors slight overillumination might help, as nonmalign bronchial cartilage has a low uptake of mTHPC and is hence relatively insensitive to photosensitization. But still, sufficient light delivery in this part is a medical challenge.
Although early esophageal SCC was found to respond very well to mTHPC PDT, irradiation at 652 nm also led to necrosis of a substantial amount of surrounding normal tissue and a deeper level so as to impair functionality. This often led to heavy side effects due to perforations and the development of tracheo-esophageal fistula. To avoid this, therapy with green light (514 nm) was introduced, allowing light penetration of only a few millimeters which subsequently diminished the undesired photosensitization of deeper tissues (382, see also 377). As one means of optimizing PDT for this particularly sensitive area, Blant et al. studied the time-dependent histological localization in the aerodigestive tract by comparative fluorescence spectroscopy of normal and malign tissues (383). However, for advanced invasive tumors in the esophagus it is likely that, due to the mentioned disadvantages, conservative treatment (surgery, radiotherapy) is the better choice at present.
Recent studies have shown success with mTHPC PDT in patients with Barrett's esophagus (384,385) and/or adenocarcinoma (386). Both conditions are closely related to one another as patients who show a Barrett's associated dysplasia are 40-50 times more likely to develop an adenocarcinoma than the general population. Thus far, PDT is only used for high-grade dysplasia or carcinoma. The initial results suggested that response rates with mTHPC PDT are better compared to ALA or Photofrin, with a 100% clearance rate of early stage neoplastic lesions and a complete re-epithelization of the squamous within a mean of 34 months using green light. Interestingly though, a comparative study was performed by Lovat et al. recently in the treatment of dysplasia and early esophageal cancer using red and green light (387). In this study, the most effective light-delivery technique was found to be the use of red light equipped with a diffuser. Note that this study pointed out that complications (including death) can arise from taking biopsy species too early. It was recommended that biopsy specimens should not be taken for at least 2 months after treatment. A comparative analysis of the various PS available in 2004 concluded that depending on the presence or absence of macroscopic abnormalities Photofrin or ALA might be the best indication (388).
As adenocarcinoma is a very severe illness with a 1-year-survival rate of only around 20% the different light-delivery techniques recommended in the various studies complicate the issue of treating esophageal cancer using PDT. As a result, the general conservative solution remains esophasectomies as the primary solution. Despite this, mTHPC PDT offers a potential second line treatment and a solution for patients who are deemed inadequate for surgery. For a recent review of this rapidly developing field see Gross and Wolfsen (389).
The very first published clinical work with mTHPC described trials investigating the photodynamic effect in the treatment of diffuse malignant pleural mesothelioma, an asbestos-related cancer (390). This severe disease is characterized by its resistance to conventional modalities such as surgery, radiotherapy and chemotherapy (391). Even with radical resection combined with chemoradiotherapy, close to one third of all patients develop a recurrence of the malignancy and a small number develop multiple recurrences (392). The tumor is fast growing and very aggressive in invading the surrounding vital structures and thus only cases in which early detection is achieved are classified as suitable for surgery. In these instances two procedures have been established depending upon the severity of the malignancy: extrapleural pneumonectomy, which involves the radical removal of one lung or pleurectomy, a procedure involving the debulking of the tumor. Extrapleural pneumonectomy is accompanied by heavy morbidity. While pleurectomies are less morbid for the patients there is an associated enhanced risk that the original tumor tissues remain in the chest cavity. The main drawback to both surgical procedures is that mesothelioma has the tendency for frequent local recurrence within a short time with associated high lethality. A recent review on the use of PDT in this area was given by Lindenmann et al. (393) while a comparison of the state-of-the-art techniques was published by Yarmus et al. (394).
At present cryotherapy, brachytherapy and PDT are the three methods suitable for the endoluminal treatment of lung cancers. While no comparative studies have been published it appears as if a complementary use of these methods is indicated. Cryotherapy is cheap and is suitable for the treatment of superficial tumors (3 mm) similar to PDT, while brachytherapy allows a deeper invasion into the bronchial wall and thus allows the treatment of more aggressive tumors (395). As mTHPC PDT was known to be superficially effective against certain malignancies Ris et al. tried to combine mTHPC PDT with the known surgical procedures (390). The idea was to illuminate the tumor surrounding surfaces in the regarded chest hemisphere posttumor removal to destroy remnants of malignant tissue, thus improving local tumor control. Investigations of the potential conditions for PDT on mesothelioma were carried out with some preliminary experiments using nude mice bearing human malignant mesothelioma xenografts (148,149). These studies also showed the utility of pegylated mTHPC (257) and the importance of the drug-light interval. Likewise, low oxygenation levels either resulting from oxygen consumption or vascular occlusion may adversely affect the PDT effect (396). This can be counteracted by nicotinamide injection and carbogen breathing (259).
In a first Phase I study on diffuse malignant mesothelioma of the chest. Ris et al. concluded that 0.3 mg kg-1 drug dose should be combined with a total fluence of 10 J cm-2 at a drug-light interval of 48 h. The study used surgical tumor resection followed by IOPDT with mTHPC. These conditions led to tumor necrosis of up to 10 mm in depth (397). Such a high impact at such low light dose had not been reported with either HpD or Photofrin previously and was an early indication for the utility of mTHPC in PDT. However, the treatment of more patients with longer follow-up times revealed that the chosen conditions were less than optimal. Longer drug-light intervals (72 h) showed a greater selectivity for tumor necrosis and less pronounced burning of normal tissue.
IOPDT was initially faced with a number of difficulties. First of all, the equal illumination of the surface of the lungs takes a very long time, increasing operational theater times which made the already heavy impact of the procedure on the patient even more troublesome (398). The fact that the large areas to be treated were complex and delicate did not help to make the practical work and estimation of the correct fluence any easier on the physician. Due to the therapy taking place in the chest, the vicinity of the site being treated also houses many of the vital organs, thus overillumination must be avoided. As a direct result of IOPDT, patients showed an additional morbidity beyond that of surgery alone, but the procedure related mortality rate was thought to be comparable to surgery without the adjuvant phototherapy. In a follow-up of 4-18 months, all patients developed either contralateral disease or distant metastasis and eventually died of their illness. Thus mTHPC IOPDT of mesothelioma has so far not led to improved survival rates, but has given some conditions for better local tumor control if the pathways for cellular localization for this type of cancer can be understood better. Further PDT developments in this area will depend on improved sensitizer accumulation and a more detailed understanding of the synergistic effects between PDT and chemotherapeutic agents.
Several other clinical studies were performed in this area (399,400). In a preliminary study. Baas et al. introduced a light-delivery system that allowed integral chest illumination and reduced the treatment time significantly. After patients had undergone extrapleural pneumonectomy the cavity was filled with a sterile plastic bag with 2.5-4 L saline solution. The bag contained a spherical bulb fiber as light source. Four isotropic detectors were positioned at various places within the chest cavity therefore allowing real-time light dosimetry. The fiber was repositioned in a way that all detectors reported comparable fluence rates. During a succeeding Phase I/II study adjustments to the conditions were made for adjuvant PDT alongside EPP to 0.1 mg kg-1. 10 J cm-2 and 96 h druglight interval, as previous treatments with 0.15 mg kg-1 led to several fatalities (401). However, the choice of quantities and light dosage for IOPDT was difficult due to the small number of patients in the study (28 in this particular case). Twenty patients showed local or distant recurrences during follow-up; however, local control could be registered in about 50% of the patients. A median follow-up of 31 months showed a median survival time of 10 months.
Friedberg et al. recently carried out a Phase 1 study combining surgical debulking (either by pleurectomy or extrapleural pneumonectomy) and adjuvant mTHPC mediated PDT (400). The maximally tolerated dose of mTHPC PDT was found to be 0.1 mg kg-1 with a fluence rate of 10 J cm-2 after a 6 day drug-light interval. Patients treated at higher doses showed several cases of acute capillary leak syndrome, which was assumed to be a dose-limiting toxicity; the PDT treatment correlated with an increase in interleukin-6 level (402). It was concluded that, unlike most other surgery-based multimodal treatments for mesothelioma. mTHPC PDT affords the option of accomplishing tumor debulking with a lung-sparing procedure rather than an extrapleural pneumonectomy. IOPDT has so far not been an answer to the highly metastatic nature of the disease (occurrence in > 50% of all patients) but in future optimized IOPDT-gained local tumor control might become part of a combined treatment strategy. Note, that the 6 day interval differs from the standard 4 days used by Schouwink et al. (401). Both studies taken together clearly indicate that compromises between minimizing toxicity, maximizing efficacy and ability of the patient to tolerate the procedures will always need to be made on a case by case basis (403,404). An excellent review of the practical aspects of clinical use of PDT and IOPDT for malignant pleural mesothelioma has been given by Friedberg (391). A few meta-analyses have addressed the use of PDT for malignant pleural mesothelioma in general. Moghissi and Dixon compared data from 10 papers (up to 2004) with 230 patients (170 with Photofrin, 60 with Foscan) (405). They calculated an overall mortality of 4.9% for Photofrin and 13.3% for Foscan. Morbidity was 38% and 70%, respectively. Overall, the mortality and morbidity associated with IOPDT was not larger than that of the related surgical procedures.
Breast cancer offers another possible area for PDT (312,406). This was indicated by early in vitro tests (217). Breast cancer patients with chest wall recurrences after mastectomy were treated successfully with mTHPC. In a study by Wyss et al. all 89 treated lesions showed complete responses (407). Two different conditions of treatment (0.1 mg kg-1, 5 J cm-2, 48 h or 0.15 mg kg-1, 10 J cm-2, 96 h) led to comparable results. The amount of pain during the first days after treatment differed considerably, depending on the size of illuminated area, but was controllable with analgesics. Still, normal tissue morbidity was relatively high.
For general reviews on the use and utility of PDT in this area see Gannon and Brown (408), Allison et al. (299) and Hillemanns et al. (316). Relevant in vitro and ex vivo tests have been described above (231). The use of mTHPC in gynecological cancers was initiated by Wierrani et al., who reported success in a small group of women suffering from recurrent intraperitoneal carcinoma of the ovary (409). Post-operative observations showed total clearance and a significant improvement of life quality. A study of eight patients with terminal disease and treated with IOPDT also indicated the utility of this drug (410). Continued work on recurrent ovary, cervix and corpus cancers showed responses in selected cases, but whether a significant life extension can be achieved remains unclear as the number of reported patients up to now is limited (411). Other investigators treated four advanced cases of SCC or adenocarcinoma located in the vulva, vagina or cervix with a rather unsuccessful outcome. The overall survival of the patient was between 3 and 4 months (412). In these instances, the patient suffered local recurrences despite an initial good PDT response, or developed systemic disease. One explanation offered was the advanced status of the tumor being beyond recovery.
mTHPC PDT was also found to be an effective measure in the treatment of vulval intraepithelial neoplasia (413). Most of the patients exhibited total response with a follow-up of 2 years. Subsequent management, like minor excisions or multiple sessions of PDT, was required in most cases. However, good cosmetic healing and preservation of function was reported overall. A case study of vulval intraepithelial neoplasia III (severe atypia) with a lowered drug dose (0.05 mg kg-1) gave excellent results in a case study (414). For a recent review on PDT of human papillomavirus-related genital dysplasias see Soergel and Hillemanns (415).
Other clinical uses
Naturally many other potential applications exist. These include the treatment of brain (309,416,414). prostate (9,310). pancreas (311) and others.
Brain. Malignant brain tumors carry a lethal prognosis with a median survival of 15 months, despite surgery, radiotherapy and chemotherapy. As it is difficult to differentiate between glioma brain tumor tissue and normal brain tissue by examination, intraoperative fluorescence diagnosis has become an important tool for neurological cancer surgery. Most work in this field was done with the ALA/PpIX and HpD systems, which afforded promising results due to the articulated concentration differences between malign and normal tissue (416,417). Temoporfin has been tested for this purpose as well. An accordant procedure has been introduced and initial encouraging experiences on patients have been made using a combination of IOPDT and fluorescence guided resection. The results showed a Umited advantage compared to the first-generation PS (418). One of the first larger studies was performed by Zimmerman et al. who conducted their experiments on 138 samples from 22 patients and were able to achieve 88% selectivity and 96% specificity from IOPDT involving fluorescence guiding resection of brain tumors such as glioblastoma multiforme (338). Similar selectivities and specifities were observed in other studies. For example, intraoperative photodiagnosis and fluorescence guided resection for radical tumor removal in a group of 25 patients improved the tumor prediction and gave a radical resection in 75% under fluorescence guided resection compared to 52% in the control group. The median survival time for the PDD/PDT group was 9 months compared to 3.5 months in the control group (419).
Stomach. A preliminary study of mTHPC PDT of early cancers of the stomach resulted in 80% total response in cancers of the intestinal type at a mean follow-up of 12 months (420,421). The drug dose chosen was lower than usual (0.75 mg kg-1) to obviate possible perforations. It was concluded that if this encouraging outcome was to be verified in following studies with larger numbers of patients mTHPC PDT could become a therapeutic option alternative to radical gastrectomy (421).
Pancreas. An initial study of normal hamsters indicated that the normal pancreas is able to tolerate PDT well, indicating that PDT might be a good modality for treatment of pancreatic cancers (272,422). This was confirmed by a related transplanted pancreatic cancer model (274). In 2002, two Phase I studies were reported on the application of percutaneously implemented mTHPC on inoperable adenocarcinomas localized in the pancreas (423) and on locally recurring prostate cancer (424). Several needles were inserted into the tumor separated by ca 1.5 cm to deliver light in both of these circumstances. Optical fibers matching these needles were subsequently inserted. During illumination, the needles were pulled back step-wise in ca 1 cm steps to cover the entire tumor with the same light dose. For the pancreatic cancer, substantial tumor necrosis was reported. The median survival rate was an encouraging 9.5 months and the quality of life was found to be improved after PDT in most patients. Recurrences at the site of PDT were not found, but often occurred at the periphery indicating that illumination should include more tumor surrounding tissue. However, the use of PDT was complicated if either major blood vessels or the duodenum wall were involved with the tumor. PDT on tumors located at these sites led to notable bleeding or perforation of the duodenum after PDT. The prostate adenocarcinomas showed significant tumor response but PDT was commonly accompanied by loss of sexual function and discomfort in urination. Still, conservative treatments of this disease have similar or worse side effects and thus further research in this is warranted (311). Later in vivo studies with a hamster model showed that Verteporfin gave a profile similar to Foscan, however with the added benefit of shorter druglight intervals and elimination times (425).
Prostate. A recent clinical review was given by Ahmed et al. (314) and a comparison of the state-of-the-art use of lithotripsy versus PDT was published by Waidelich (426). mTHPC was first used in studies with dogs and was shown that it can be safely used for treatment of the gland (285). Next PDT was described as a salvage treatment after failure of external beam radiotherapy (424). A Phase I study showed that prostate cancer can indeed be treated; the level of prostate specific antigen fell by up to 67% in the six patients tested (427). Dosimetry is of critical importance for an effective treatment in this area (428). In this context an interactive dosimetry by sequential evaluation module has been developed for clinical trials of primary prostate cancer with Foscan (429). Preliminary studies on the use of IPDT have been reported as well (430). Alternative minimally invasive techniques are cryotherapy and high intensity focused ultrasound.
Biliary system. PDT treatment of bile cancers is only slowly emerging (431,432). A significant problem for the palliation of patients with malignant bile duct obstruction using metal or plastic biliary stents is stent occlusion. In this context endoscopically performed Foscan PDT was investigated in 13 patients with malignant biliary carcinoma obstructions (nine biliary tract, three pancreas, one stomach). All patients had been initially palliated with stents; however, recurrent obstructive jaundice had occurred due to local tumor progression. After PDT tumor necrosis and/or metal stent recanatization was observed in all patients and the median patency of plastics stents increased from 3.5 to 5 m. Median survival times increased from 8 to 21 m. However, although PDT was tolerated well, significant complications were observed in this study (433). At present intraoperative radiotherapy appears to be more suitable. However, preliminary data of PDT in bile duct cancer gave good reduction of cholestasis, improvement of life quality and prolongation of survival time (434,435). Studies on cholangiocarcinoma are presently expanding (233,436).
Papillomatosis. Only one investigation has explored the efficacy of mTHPC PDT in the treatment of recurrent respiratory papillomatosis (437). A reduction of the severity of laryngeal papillomas was seen during the first year after PDT. However, this was attributed to a probable improved immune response.
Retinoblastoma. An initial study with Foscan utilized three xenograft cell lines derived from surgical samples taken from children. A significant response upon Foscan treatment was observed for one of the cell lines (RB111-MIL) and partial regression was observed after 60 days (438).
Anal cancer. One study with four patients studied the use of a light applicator for the treatment of anal intraepithelial neoplasia Grade III. Here an applicator based on a standard anoscopy instrument was used and it was shown that blood saturation, volume and fluorescence and fluence rate can be monitored without changes in the light protocol (439). Nevertheless, a study with Fosgel administered to nine patients (eight HIV-positive males and two HIV-negative women) with anal intraepithelial neoplasia (III) showed no effect of the PDT treatment (440). This was attributed to the limited penetration of the liposomal formulation and the study of other topical PS applications is indicated.
Many possibilities exist to use PS in areas other than cancer treatment. These include the well known treatment of agerelated macular degeneration, use in dermatology (441), esthetics (photodynamic photorejuvenation), periodontal uses (442) and more. Sterilization and antibacterial action are clearly suitable application areas as well (443). Antifungal PDT may also be used, but has not been used with mTHPC derivatives yet (444). However, porphyrins, ALA and phthalocyanines have all been shown to kill yeast and dermatocytes through photodynamic action, indicating the utility of this approach. Use of mTHPC is ever expanding and will see many new applications in the near future. To give only one example, an interesting study by Hansch et al. showed that mTHPC-based phototreatment may be used for the treatment of rheumatoid arthritis (445). They used a murine antigen-induced arthritis model and found that mTHPC-PEG was taken up best in arthritic joints. Light treatment resulted in lowered arthritic scores at lower drug doses compared to what is used in cancer PDT. Thus, local treatment of arthritis appears to be feasible.
Ophthalmological applications for Foscan PDT are only slowly emerging (446). Liposomal formulations of BpD-MA and Foscan were tested in the chick chorioallantoic membrane model with regard to the treatment of choroidal neovascularization which is secondary to age-related macular degeneration. Here, PDT treated areas were treated with a soluble antivascular endothelial growth factor (recombinant human soluble VEGF R1 [sF1t-1]/Fc chimera). The topical application of this factor helped with occlusion and limited subsequent angiogenesis in a dose-dependent manner (447).
More and more studies with PS address their use for antibacterial action, including intracellular pathogens (325,443). A study from 1995 using isomers of THPP already indicated the potential antibacterial action of this type of compound (448). An early study into the antibacterial action showed that Foscan has antibacterial effects on Staphylococcus aureus (wild type) in the dark while hematoporphyrin derivative showed suppressive growth effects only after white-light illumination (411). Many of the newer derivatives and formulations of Temoporfin (vide infra) are now tested for the treatment of infectious diseases.
Antibacterial nanoparticle formulations are especially interesting. For example, a test of different cationic liposomal formulations of Foscan for antibacterial action showed that subtle variations significantly affect the uptake. Only one of the formulations tested gave results similar to the free drug (449). Likewise, calcium phosphate nanoparticles were surface-functionalized with different polymers, and PS was incorporated into this layer (450). Here, methylene blue and mTHPP showed good performance with HIG-82 synoviocytes. Moderate activity was found with HT29 epithelial cells while good photoxicity was found against S. aureus, both with positively and negatively charged nanoparticles loaded with mTHPP. The Gram-negative Pseudomonas aeruginosa could only be treated with positively charged nanoparticles containing mTHPP (451).
The dental care field has also become interested in PDT. Mostly this involves antibacterial PDT for periodontal applications (442). Such an approach is warranted as there is increased antibiotic resistance, the number of immune-suppressed patients has risen, and diverse pathogens play a role in periodontal infections, mandating different drug approaches. Foscan fluorescence in the buccal mucosa can be used to determine its concentration (379). A recent study investigated the effect of PDT on cariogenic bacteria. A comparative analysis of mTHPC and hypericin with Streptococcus mutans and S. sobrinus showed that the latter could easily be killed with both PS (the light source used was a dental polymerization instrument). At similar concentrations the former exhibited dark toxicity to mTHPC and no effect with hypericin. However, coadministration of both PS eradicated the bacterium effectively. Thus potentially there is a role for PDT in oral cavity antibacterial action. However, while the study showed very good results for a single bacterial species it appears that the really multispecies environment of the oral cavity presents a significant treatment problem (452). The use of Fospeg was studied as well. It provides a means to deliver an aqueous solution via spray techniques, and gave a significant reduction in bacterial cell count (453).
PDT combined with other methods
Naturally PDT is often used in conjunction with surgical treatments. However, some potential exists for the combined use with other cancer treatment protocols. This is a rapidly emerging field and includes the combined use of PDT with other chemotherapeutic drugs or immunostimulants and dual modality treatments.
PDT and chemotherapeutics. Foscan PDT could be improved by coadministration of mitomycin C in an animal model (202). This allowed the use of lower light and PS doses for the same therapeutic effect. This effect did not occur when using a bacteriochlorophyll a analog. A water-soluble vitamin E analog, Trolox, has been shown to enhance the PDT effect. When administered together with the PDT drug it resulted in an increase in the tumor doubling time in a human tumor xenograft model (454). Possibly, this is the result of the Trolox-mediated radical pathway acting in conjunction with the singlet oxygen reactions; Trolox did not prevent photobleaching of the PS.
Immunostimulants have been shown to enhance the PDT effect in animal models (210). Adoptive immunotherapy using a human NK cell line (NK92MI) that was genetically altered to produce interleukin-2 has also been successfully applied to several human and murine cancer cell lines (455). BCG immunotherapy was found to be effective in a mouse mammary carcinoma model (256). Another possibility would be to impair the complement system to affect the antitumor response to PDT. Using mouse tumor models it was shown that for example Zymosan, an alternative complement pathway activator reduces the recurrence rate of tumors and increases the permanent cure rate (456). Likewise systemic complement activation with streptokinase and PDT treatment gave better results. Thus, complement activating agents can be used for adjuvant treatment. Another immunostimulant which has shown potential as an adjuvant for PDT is a glycated chitosan, described by Chen et al. (457). In a related study the ceramide analog LCL29 was coadministered with Foscan PDT and resulted in enhanced long-term tumor cure (458). The effect was highly specific for certain sphingolipids and indicated that the sphingolipid profile distribution can serve as a biomarker for the PDT response.
Clearly the combined use of chemotherapy and PDT would be attractive. However, early studies gave mixed results. In vitro tests of the effect of fluoropyrimidines with PDT showed a significant dependence of the outcome on the treatment protocol and the cell lines (MCF-7 and LNCaP) (459). A human case study showed significant side-effects and indicated the necessity for further studies (459). A validation of viability assays with two rodent tumor lines showed an increased PDT effect in the presence of the cytostatic drug doxorubicin (460). Similar results were obtained with studies on murine hepatoma (461). Interestingly, preliminary data indicate that the treatment of PDT + doxorubicin was better than first giving doxorubicin and then PDT. Thus, administration of doxorubicin directly after light treatment appears to be best (461). On the other hand, a study of murine leukemia treated with a combination of Foscan and either cisplatin or navelbine as chemotherapeutics and administration of immuno lymphocytes from PDT pretreated cells showed a significant synergistic effect (462). A possible means to lower the PDT effects on healthy tissues was reported from a pig stomach study. Standard Fosean PDT gave 71.4% full-thickness necrosis. However, with octreotide the PDT effect was only 28.5% (463). Octreotide is a somatostatin analog and decreases the splanchnic blood flow and has multiple inhibitory effects on the peptic system. Thus, it might be possible to down regulate the PDT effect in normal gastric tissue in pigs.
Dual treatment modalities. A combination of PDT with other treatment modalities is indicated for several cancer types and has been discussed above. Typically this involves PDT in conjunction with surgery, chemotherapy or radiotherapy. For example, an early in vitro study of breast cancer cells already showed that PDT and radiotherapy effects are additive and independent of each other (234). Another possibility is the use of magnetic nanoparticles. This allows the combination of PDT with magnetic hypothermia therapy (464).
The physical properties of mTHPC, although principally investigated for its potential as a PDT photosensitizer, have fortuitously resulted in its use in other applications. For example, mTHPC has been tested successfully as matrix material for the use in MALDI-TOF MS for low molecular weight compounds (47). Potential for application in a non-clinical area exists in the nutrition industry, where sterilization of surfaces is an important subject. The usefulness of non mTHPC PS was successfully demonstrated to kill microorganisms fixed on solid surfaces (465). Water sterilization is another potential application for PDT. In the context of the topic of this review one example is the use of immobilized 5,10,15, 20-tetrakis(4-hydroxyphenyl)porphyrin for the disinfection of water (466). This indicates that in practical terms PS which failed in medical terms due to high toxicity may still be useful for technical applications.
RELATED SENSITIZERS AND DEVELOPMENTS
Clearly, mTHPC has proven to be a successful and interesting photosensitizer to date. Thus, it is none too surprising that the development of new PS is partly resting upon the so far gained knowledge of its properties. In fact, a significant area of photosensitizer development relates to the modification of mTHPC in an attempt to address some of its shortfalls. This is similar to the situation for any other second-generation PS, where continuously advances are made with regard to chemical modification, different formulations or new targeting strategies. Many of these advances are related to new strategies for drug delivery (108). In addition, many PS drugs closely related to mTHPC are now available. For reasons of space only the developments relating to direct use of the mTHPC molecule will be described. An analysis of chemically related compounds will be given elsewhere. No real QSAR study involving the various derivatives has been performed for the latter and an assessment of their utility and benefits relies on individual studies and comparisons. Likewise, it is somewhat surprising that the p-isomer of THPP still often features in preclinical studies.
General. Efforts to modify the basic mTHPC properties through chemical manipulations began early in the Fosean "story." In an attempt to improve the localization of mTHPC in tumor cells and its solubility, it was proposed that the construction of a photosensitizer-polymer conjugate would lead to an increased selective retention of the drug in tumor tissue resulting in an enhancement of selective tumor destruction by light in PDT (467). Since then the development and use of mTHPC-PEG (7) has developed almost into a separate research interest (223,251,252,256,280,291,468-482). In chemical terms pegylation of Foscan is achieved through etherification reactions of the hydroxy groups. Depending on the exact type of side chain attached (mostly its length) or the type of linker group used for attachment different types of mTHPC-PEG have been prepared. Examples are mTHPC-MD2000 (sometimes listed as SC102), mTHPC-MD5000 and others. Often the tradename Fospeg® is used as well. Sometimes clinical publications are problematic in that the exact type of "PEG" is not specified.
Different materials require different detection methods. For the analytical detection of mTHPC-PEG, HPLC is not sensitive enough and spectrofluorimetric methods are better suited (468). MS analysis requires HPLC ESI-MS to separate the oligomers for molecular mass analysis (483). Its absorption spectrum is similar to that of unmodified mTHPC and the major difference in solution is the absence of dye aggregation effects. Based on the fluorescence quantum yield of chlorophyll a and mTHPC (0.22), mTHPC-PEG exhibited a slightly lower quantum yield of 0.19 in aerated ethanol (470).
Cell and animal tests. Fospeg and analogs have tested in various in vitro and in vivo settings (Tables 2 and 3). Selected in vitro tests are compiled in Table 4. Representative cell studies included investigations on malignant mesothelioma (223,257,475,482). Chinese hamster lung fibroblasts (223), human colorectal carcinoma cells (470) and xenografts (467) and murine leukemic cells L1210 (470). Other examples were studies on ovarian cancer cells (474) with very high tumor/tissue ratios (280) and liver tumor models (478), which showed no significant advantage. For example, mTHPC-MD2000 in a rat colon adenocarcinoma resulted in an increase of PS concentration in the liver with time, thus resulting in a loss of tumor selectivity (478). In human prostate cancer cells Fospeg exhibited a lower LD50 than Foscan (484). In vitro studies related to ophthalmology were reported as well (447).
Many of the studies made comparisons of the PDT efficacy between free mTHPC and mTHPC-PEG. However, which one prevails as the more efficient PDT photosensitizer is dependent upon the site of the tumor, linker groups (251,469,473) and the conditions employed for the study (252). A study with SCC cells yielded similar PDT effects for mTHPC and mTHPC-PEG and at lower light intensities mTHPC was shown to be 20 times more effective. However, mTHPC-PEG showed higher tumor accumulation rates (477). The photodynamic effect of mTHPC-MD2000 is dependent on the light protocol, as was observed for mTHPC. Similar to the situation for mTHPC the photodynamic effect of mTHPC-MD2000 is dependent on the light protocol used (153). For example, studies with interthoracic tissue of minipigs showed that while mTHPC resulted in damage to almost all tissues except nerves at short drug-light intervals, mTHPC-PEG showed no obvious damage to any tissues at any drug-light intervals (257,470) and was considered a safe drug for further applications in PDT (576). An endobronchial PDT study in minipigs showed that mTHPC under standard conditions resulted in ulceration and bronchial mucosa necrosis while mTHPC-PEG gave no such effect (471). Similarly, good results were obtained in testing the feasibility of extrapleural pneumonectomy followed by mTHPC-MD2000 PDT. No adverse side-effects were observed (482). Other animal tests included SCC (251,471,475) and adenocarcinoma xenografts (471,475), where mTHPC-PEG led to larger tumor necrosis than mTHPC in the former but not in the latter. Rabbits inoculated with cottontail rabbit papilloma virus served as another test case and gave a 58% cure rate with high drug doses. Skin tolerance was excellent in the rabbit model and in a healthy dog larynx model (485). For human oral SCC xenografts mTHPC was found to be superior to mTHPC-PEG (252). The action of mTHPC-MD5000 is delayed compared to mTHPC, but significantly exceeds that of the latter at Day 4 (475).
In human colon carcinoma xenografts the pegylated form gave on average a two-fold higher tumor uptake than free mTHPC and, at early times after injection, showed a two-fold longer blood circulating half-life and a four-fold lower liver uptake (472). mTHPC-MD5000 was preferentially localized near the tumor vessels while mTHPC was distributed more diffusely in the tumor tissue. Maximum fluorescence in this system was observed after 24 h with adequate tumor:skin (2.95) and tumor:muscle (6.61) ratios (470). Human malignant mesothelioma implanted in mice showed a similar PDT response for mTHPC and mTHPC-MD2000 but lower skin phototoxicity for the latter (486). Other studies focused on side-effects (476) or the preparation of (487) and incorporation into nanocapsules (481,488). Alternative developments for drug delivery are liposomal pegylated formulations (Fospeg) that have been used in studies on SCC (291) or mTHPC incorporated into liposomes (Foslip) (287). All three were compared for their effect to occlude neovascularization and it showed that Fospeg was the superior of the three (287). Multiphoton excitation of pegylated derivatives has been studied (479,480) and the antibacterial action of Fospeg was shown (453). More detailed biochemical studies on the intracellular effects of pegylated compounds are slowly emerging (489).
In line with other PS further reduction of the mTHPC (a chlorin) will yield the related bacteriochlorin (mTHPBC) 3 with redshifted absorption spectrum (735 nm) (29). Its photophysical properties were described by Bonnett et al. (50). This bacteriochlorin undergoes photobleaching at ca 20 times the rate of mTHPC (490). It also suffers partial phototransformation to mTHPC in buffer solution (491) and can form other photoproducts as well (72). Initial tests with a mouse colon cancer cell line indicated that mTHPBC is prone to aggregation and oxidation in aqueous media (492). The cell tests showed a similar uptake profile for mTHPBC and mTHPC and identified several "forms" of mTHPBC in the cells. About 30% of the bacteriochlorins was oxidized to mTHPC in the cell within 24 h; after that its oxidation level remained stable. Initial PDT studies showed that mTHPBC has ca 60-70% of the activity of mTHPC. Its pharmacokinetics were determined in a rat colon tumor model and showed that the PDT threshold depends mainly on the administered drug dose (490). Necrosis of normal rat liver tissue was enhanced in IPDT compared to Temoporfin or Photofrin (493). Overall, the increased lability of the compound and only minor advantages suggest that this dye might not be worth further development.
Nowadays "nano" is often considered the savior of everything that is wrong in medicine and science and PDT is no exception. In the early years of PS development this mainly meant the preparation of nanodelivery vehicles, i.e. liposomes. Naturally, there are many different means by which a "nano" approach can be used in PDT. Many reviews on the use of "nano PDT" have been published in recent years and give a good overview of the field (146,147) and about potential carrier systems (494). Others addressed more specific aspects such as quantum dots or nanoparticles (495), liposomal formulations (496), skin permeation (497) or dendritic micelles (498). There are many reasons for using nanosized materials in PDT. Perhaps the most basic is to improve the tumor selectivity through limiting the reticuloendothelial system uptake, i.e. letting "size" dictate the localization of the drug. Longer retention times of the drugs, although counterintuitively with regard to photosensitivity, also allows multiple illuminations and such can overcome the problem of oxygen depletion in the tissue.
Liposomal formulations. Similar to the development of Fospeg® in parallel to Foscan liposomal formulations of mTHPC (some under the trademark Foslip®) have progressed well. Foslip® is a recently designed third-generation photosensitizer based on unilamellar dipalmitoylphosphatidylcholine/dipalmiloytphosphatidylglycerol (DPPC/DPPG) liposomal formulations of mTHPC. By now many applications of liposomal formulations have been tested and overall indicated reasonable utility. For example, studies with feline SCC indicated a 2-4 times better bioavailability, a shorter distribution half-life, and good selectivity compared to mTHPC (291). Detailed studies on the exact physicochemical composition of such systems are still rare (499). Fluorescence lifetime measurements indicate that Foslip and Foscan are taken up in a similar manner, but might be located in different intracellular sites (103). Incorporation into liposomes clearly changes the properties of Temoporfin (500). For example, a comparison of three chlorins, including mTHPC, in solution and incorporated in dioleoyl-sn-phosphatidylcholine liposomes showed that the three PS had a similar propensity to generate singlet oxygen in solution. However, incorporation into liposomes gave a higher efficacy for mTHPC. This was attributed to the relative distance of the PS to the water-lipid interface (501). The spectral properties significantly depend on the liposomal composition. Fluorescence measurements in DPPC liposomes with different DPPC:mTHPC ratios demonstrated a dramatic decrease in fluorescence anisotropy with increasing local drug concentration. This indicates significant interactions between the PS molecules in the lipid bulk medium. Illumination with small light doses resulted in a drop in fluorescence which could be restored through addition of Triton X-100. This photoinduced fluorescence quenching depended on the DPPC/PS ratio. Likewise, addition of plasma protein to liposomal solutions resulted in a slow redistribution of the drug to proteins (502). Thus any Foslip biodistribution analysis must take this effect into account.
Tests with mouse mammary carcinoma showed that Foslip is taken up over the course of about 1 day. Optimum but partial cure rates were observed 24 h postinjection. Fluorescence was weak and inhomogenous during the initial times and became maximal at 24 h. This might be an indication that during the initial times the fluorescence is quenched (as the drug is still in the liposomes) and that a slow release to membranes occurs. The total amount of drug present was lower compared to systemic administration, probably due to reabsorption into the blood (503). Biliary cancer cell lines reacted similarly to Foscan and Foslip, both gave excellent phototoxicity (232). Taking the water solubility and thus easier administration of Foslip into account this indicates the utility of the latter. Foslip was first tested in an animal model in 2007. Pharmacokinetic studies with a HT29 mice model showed rapid take up and good selectivity for tumor/muscle, slightly higher than that for Foscan (504). The tumor/muscle selectivity was not time dependent; however, the tumor/internal organ selectivity increased at later times. The plasma concentration was low and did not change much after PS injection. Thus, Foslip undergoes a rapid biodistribution and clearance (505). Studies in EMT6 xenografted nude mice indicated the highest tumor to muscle ratios to be reached at 6 and 15 h postadministration. The best tumor response was obtained for a drug-light interval of 6 h. At that time the drug was present in both endothelial and parenchyma cells. Nevertheless, the tumor and plasma concentrations were much lower than the maximal values (506).
A detailed analysis of the preparation of liposomal mTHPC formulations incorporated into liposomes indicated that Foslip shows promise for the treatment of age-related macular degeneration (287). Foslip has also undergone initial tests for veterinary applications in cat SCC (292). A liposomal preparation of Foscan has also been used for the treatment of cellulitis. It was applied using a mesotherapy gun-followed illumination with visible laser light with a wavelength of 652 nm and at a light dose of 10 J cm-2. Improvements of the skin thermographic pattern, of the superficial capillary net and of clinical aspects of the skin cutaneous surface were noted. However, the mechanism of action was attributed to a purely thermal effect (507). Another means to increase the uptake of Temoporfin formulations is the use of liposomes containing ethanol. Liposomes containing 20% ethanol were shown to exhibit increased skin penetration (508). Another study of liposomal systems was performed by Molinari et al. (509). Cationic liposomes with cationic Gemini 1 surfactant were found to transfer mTHPC more effectively into glioblastoma cells (510), increased its photocytotoxic effect and appeared to work in an early phase of the interaction with cells. For a general review on the current use of Gemini surfactants see Bombelli et al. (511).
Topical applications became quickly a focus of attention as well (512). A topical application of liposomal Temoporfin formulations has been tested with nonpigmented skin malignancies in humans, too. It exhibited high tumor selectivity and gave indication of a photometabolization process with a delay time of ca 30 min. No pain occurred and no swollen tissue or skin reddening (as often with ALA) was observed (513). Recently attention has focused on liposomal hydrogel formulations. A gel containing 0.75% (wt/wt) carbomer and lecithin with high phosphatidylcholine content was considered to be the optimal formulation. It delivered high amounts of mTHPC to the stratum corneum and deeper skin layers, and possessed desirable rheological properties (514). Such hydrogels were shown to exhibit good stability over a period of 6 months (515).
Another new development is the use of so-called invasosomes (516). These are phospholipid vesicles which contain a mixture of terpenes (e.g. cineole, citral or d-limone) as penetration enhancers. A first study for the use of such systems for the topical treatment of HT29 tumors in mice showed a slowed tumor growth in the treated animals (517). Initial tests showed enhanced deposition in human skin with these formulations (518,519). Flexosomes is another name recently coined for a special type of liposomes. It refers to flexible liposomes which are constructed using phosphatidylcholine plus polysorbate 20 (neutral), or dicetyl phosphate (anionic) or stearylamine (cationic) (520). Human abdominal skin was mounted in a Franz diffusion cell as a model for percutaneous penetration and treated with the respective mTHPC liposomal (or flexosomal) formulation. The anionic flexosomes were found to show insufficient long-term stability. Both neutral and cationic were stable over 9 months and the cationic flexosomes showed the highest penetration enhancing ability.
mTHPC nanoparticles. Other attempts to prepare mTHPC containing nanoparticles focused mainly on biodegradable systems (521). A study of mTHPC encapsulated in poly(D,L lactic acid) or grafted with polyethylene glycol showed a reduced cellular uptake in HT29 tumor cells. However, the PDT effect was affected much less and the localization pattern was different to standard use (488). Other modifications resulted in significant modifications of the biodistribution and tumor retention and reduced liver uptake (481). Similar studies have been performed for related porphyrin systems (522,523). For example, a study of mTHPP encapsulated into polymeric biodegradable poly(D,L-lactide-co-glycolide) nanoparticles enhanced its photodynamic activity against mammary tumor cells when compared to the free drug (524). A recent study investigated the effect of loading mTHPP or mTHPC onto human serum albumin nanoparticles (525). Both the singlet oxygen production and the phototoxicity of the nanoformulation were increased compared to the free drugs (526).
Other possibilities are the use of quantum dots to increasing the PDT efficiency through electron transfer (527). Silica nanoparticles have been employed as well. To highlight a possible way to circumvent its low water solubility and the problems of localization, Yan et al. chemisorbed mTHPC onto nanoparticle platforms of silica as a potential drug delivery technique (528). According to singlet oxygen studies, the 1 O2 production of mTHPC embedded on silica nanoparticles was higher than that of free mTHPC. But "nano" is not necessarily better. For example, mTHPC entrapped in organic-modified silica nanoparticles showed 50% less cellular uptake than the "free" drug (529). The nanoparticles underwent aggregation under high salt conditions, which could be prevented by BSA. Fluorescence resonance energy transfer experiments in esophageal cancer cells showed that the drug is transferred from the NP to serum proteins and is then internalized by the cells as a protein complex.
Micellar systems have been employed as well. For example, the water solubility of the hydrophobic 5,10,15,20-tetrakis (4-hydroxyphenyl)porphyrin could be increased by a factor of 200 through incorporation into micelles formed from hexyl-substituted polylactides in combination with PEG to give amphiphilic block copolymers PEG-hexPLA (530). Another study investigated the uptake of mTHPC loaded micelles of mPEG750-b-oligo(e-caprolactone)5 (mPEG750-b-OCL5) with a hydroxyl, benzoyl or naphthoyl end groups (531). Micelles with benzoyl and naphthoyl end groups had the highest loading capacity. However, while they were taken up no PDT effect was observed in H&N SCC cells. Cellular uptake and photocytotoxicity was observed only in the presence of lipases, which catalyze micelle degradation. This suggests that intact micelles are not taken up by the cells. Micelles formed from poly(2-ethyl-2-oxazoline)-b-poly(D,L-lactide) (PEOz-b-PLA) diblock copolymer and loaded with Temoporfin gave a similar PDT effect in HT29 mice but resulted in less skin phototoxicity (532). Similarly, mTHPP filled PEG-PLA micelles were photoactive against H&N cells (533).
An example for a pH sensitive nanosystem was given by Peng et al. (534). They prepared Temoporfin loaded polyethylene glycol) methacrylate-co-2-(diisopropylamino)ethyl methacrylate (PEGMA-co-DPA) nanoparticles (89% encapsulation efficiency) and showed a faster release at pH 5 in HT29 cells compared to pH 7. Other applications used Temoporfin loaded calcium phosphate nanoparticles for antibacterial studies (535). Another possibility is the use of magnetic nanoparticles. This allows the combination of PDT with magnetic hypothermia therapy. The preparation of a magnetic nanoemulsion of Foscan showed improved skin permeability and longer skin retention times in pig ears compared to standard formulations (464). Gold nanoparticles have been loaded with three layers of mTHPP indicating the high loading capacity of such systems (536). Nevertheless, the biological utility of such systems remains unclear. Despite the current interest in nanoparticles for PDT drug delivery it is often difficult to predict the drug release from the nanoparticles in vitro or in vivo. Here, mTHPC was used to develop a flow cytometry method that allows an investigation of the transfer of dyes from donor particles to acceptor emulsion droplets (537).
CONCLUSIONS AND OUTLOOK
Comparison with other PS
Surely the questions arises how mTHPC and its formulations and developments relate to other PS. However, a simple, clear cut answer is not possible. Drug development is driven by individual groups and companies, each of which may focus on different disease types, cell lines, animal models and so forth. Even at the in vitro level only few studies compare all the currently used PS (538). One example of such a study was recently presented by Berlanda et al. (539). A comparison of the six most widely used PS clearly showed the utility of both Foscan and Fospeg. Both exhibited the lowest LD50 values; however, the respective IC50 values were higher than those of the other PS. Overall, significant differences were found between the various PS. Clearly this indicates the problem involved in choosing the right (or best) PS for a given clinical application and the need for more comparative analyses at all levels. Another problem is that the patient numbers in clinical trials are still very limited in PDT and that in most cases a clinical trial focuses on one drug and not a comparison of different PS (540). Probably, a critical meta-analysis of the various PS is needed from the clinical community. Foscan's simple preparation and purity probably makes it a better choice than the first-generation PS Photofrin. Within the range of second-generation PS questions such as type of cancer, possibility of topical application, formulations, etc., need to be taken into account.
From a chemical viewpoint, the substitution pattern of hydroxyphenyl groups seems to be important for the exceptional photoactivity, but the molecule has an overall symmetric structure which is to some extent an antagonism to the known potential of amphilicity within PS. Unsymmetrically substituted drugs are believed to possess enhanced abilities toward the hydrophilic/hydrophobic interfaces of membranes and proteins and thus appear to be of greater photodynamic importance (541,542). Hence, a concept to screen for improved drugs is to synthetically achieve a clearly laid out library of related unsymmetrical tetrapyrroles substituted with the crucial hydroxyphenyl- or related hydrophilic groups and various hydrophobic groups, e.g. based on the ABCD-type derivatives, which are now synthetically possible (543,544). Clearly formulation studies will feature prominently in new advances and offer cheaper developmental pathways for the pharmaceutical industry. Thus, it might be worthwhile to study Temoporfin formulations with respect to delivery advances made for other PS. One example is the recent report on the use of micelle encapsulated Hp as a pulmonary delivery platform (545).
Different excitation methods can also enhance the PS effectivity. An initial study has shown that it is possible to use two-photon absorption for mTHPC PDT (546). Here, significant potential exists for the construction of appropriately designed "Temoporfin-based" two-photon absorbers (547). Possibilities also exist to improve PDT in general through different light administration (136), e.g. through saturation of the PS triplet state (548). Likewise significant potential for cost savings and safety exist through novel light sources (549). Thus, light emitting diodes have been tested in conjunction with Foscan and showed similar PDT effects in cell tests and rat liver necrosis (550,551). Optimized analysis for PDT requires multivariant analysis and not only checking on light dose, dark-light interval, and so on (552). Likewise, improvements in in vivo quantification are necessary (553). An integrated approach using real-time dosimetry and treatment planning is required and needs to be combined with multimodality imaging and PS development (554).
Many new concepts for PS delivery and action have been developed in recent years. One example is photochemical internalization (PCI) (555,556). This technique utilizes the accumulation of a drug in endocytotic vesicles which, upon light exposure, release the PS into the cytosol in active form. With regards to PS, the best candidates appear to be amphiphilic ones, and most of the initial studies focused on anionic PS. For example, the related mTHPP did not show any PCI effect (557). Still, appropriate functionalization of the mTHPC framework is chemically possible and might lead to new candidates. Not everything that is described as a new concept or has been given a catchy new name is really novel. Biological photoinactivation is one of the oldest concepts in photomedicine and thus has led the groundwork for many areas of research that currently attract interest. For example, theranostics has been coined as a term for the combined use of therapy and diagnostics in personalized medicine (558). Clearly PDT and PDD are classic examples for this, especially when combined with the need for individualized dosimetry.
Many areas of PDT have only just begun to show its potential. For example, immunostimulation offers significant potential but lacks large scale studies (208). For example, it is yet unclear whether a PDT treatment protocol to elicit local tumor control is different from that for immune stimulation. Translation studies in the latter area are clearly needed to test the utility (or lack thereof) of PDT-induced antitumor immunity. In the context of hydrophobic PS such as Foscan this also requires addressing the intracellular bioavailability of the PS (160). Still, many of the currently investigated "new" applications might look very old and go back to the beginning of photomedicine (559). Due to the high costs of drug development companies and researcher might focus more on infection, sterilization, where regulatory approval might be easier.
Several of these topics listed above are now actively investigated for various third-generation PS (560). The future will show what this ongoing process is able to deliver for the patients. At present, despite the many advances made in research and preclinical studies the translational status of PDT remains disappointing. After 40 years of studies its full clinical potential as an alternative or adjuvant therapy next to chemo and radiotherapy and surgery has not been realized. In 2006 only six PDT drugs were marketed for various indications, all with clear cost efficiency compared to classical procedures (561). The technique is easily handled, requires only minimum investments and can be performed in simple medical settings allowing use in developing countries. Many general practitioners remain unaware of this technique. Marketing appears to be especially poor and, outside of dedicated PDT centers, this modality often has the status of a niche development in oncology. In a sense its development is reminiscent of the early decades of radiotherapy development (562).
The one drawback of PDT, photosensitivity, is much relieved with newer drugs, yet more approvals are not forthcoming. There also seems to be an overemphasis on photosensitivity. Compared to other techniques this is a small price to pay for a potential cancer cure. An obvious problem with Foscan is that, while approval was granted in the EU none was given by the FDA for the United States which limits further research (563). Large scale follow-up studies remain few and most clinical uses still utilize Photofrin despite some of its drawbacks. To date the field is dominated by very few relatively small pharmaceutical companies and is driven forward mainly by dedicated clinicians and research scientists with limited financial resources. Within their hands lies the potential to use the lessons learned from second-generation PS such as mTHPC and to develop photoactive drugs that will find more general acceptance and use. While the future might not necessarily be in Foscan or its follow-ups, the use of PDT and PD in oncology has to be considered as one of the more fundamentally new treatment options in past decades (294,564).
Acknowledgement-This work was supported by grants from Science Foundation Ireland (SFI Research Professorship 04/RP1/B482. P.I. 09/IN.1/B2650) and the Health Research Board (HRB Translational Research Award 2007 TRA/2007/11).
1. Raab, O. (1900) Über die Wirkung fluoreszierender Stoffe auf Infusorien. Z. Biologie (Munich) 39, 524-546.
2. Mathews. M. M. (1964) Protective effect of beta-carotene against lethal photosensitization by haematoporphyrin. Nature 203, 1092.
3. Bonnett, R. (2000) Chemical Aspects of Photodynamic Therapy. Gordon & Breach Publ., Amsterdam.
4. Dougherty, T. J. (1993) Photodynamic therapy. Photochem. Photobiol. 58, 895-900.
5. Stewart, J. C. M. (1993) Photosensitizers for photodynamic therapy. Curr. Opin. Invest. Drugs 2, 1279-1289.
6. Senge, M. O. (1992) The conformational flexibility of tetrapyrroles - Current model studies and photobiological implications. J. Photochem. Photobiol. B: Biol. 16, 3-36.
7. Kessel, D. and T. J. Dougherty (1999) Agents used in photodynamic therapy. Rev. Contemp. Pharmacother. 10, 19-24.
8. Ash, D. V. and S. B. Brown (1993) New drugs and future developments in photodynamic therapy. Eur. J. Cancer 29A, 1781-1783.
9. Moore, C. M., I. M. Hoh, S. G. Bown and M. Emberton (2005) Does photodynamic therapy have the necessary attributes to become a future treatment for organ-confined prostate cancer? BJU Int. 96, 754-758.
10. Wagnieres. G. A., W. M. Star and B. C. Wilson (1998) In vivo fluorescence spectroscopy and imaging for oncological applications. Photochem. Photobiol. 68, 603-632.
11. Bonnett. R. (1995) Photosensitizers of the porphyrin and phthalocyanine series for photodynamic therapy. Chem Soc. Rev. 24, 19-33.
12. Boyle, R. W. and D. Dolphin (1996) Structure and biodistribution relationships of photodynamic sensitizers. Photochem. Photobiol. 64, 469-485.
13. Pandey, R. K. and G. Zheng (2000) Porphyrins as photosensitizers in photodynamic therapy. In The Porphyrin Handbook. (Edited by K. M. Kadish, R. Guilard and K. M. Smith) Vol. 6, pp. 157-230. Academic Press, New York.
14. Sternberg. E. D., D. Dolphin and C. Brückner (1998) Porphyrinbased photosensitizers for use in photodynamic therapy. Tetrahedron 54, 4151-4202.
15. Sternberg, E. and D. Dolphin (1996) Pyrrolic photosensitizers. Curr. Med. Chem. 3, 239-272.
16. Nyman, E. S. and P. H. Hynninen (2004) Research advances in the use of tetrapyrrolic photosensitizers for photodynamic therapy. J. Photochem. Photobiol. B: Biol. 73, 1-28.
17. Kudinova, N. V. and T. T. Berezov (2010) Photodynamic therapy of cancer: Search for ideal photosensitizer. Biochem. (Moscow) Suppl. Ser. B: Biomed. Chem. 4, 95-103.
18. Kessel, D. (2004) Photodynamic therapy: From the beginning. Photodiagn. Photodyn. Ther. 1, 3-7.
19. Ackroyd, R., C. Kelty, N. Brown and M. Reed (2001) The history of photodetection and photodynamic therapy. Photochem. Photobiol. 74, 656-669.
20. Moan, J. and Q. Peng (2003) An outline of the hundred-year history of PDT. Anticancer Res. 23, 3591-3600.
21. Bonnett, R. (1999) Photodynamic therapy in historical perspective. Rev. Contemp. Pharmacother. 10, 1-17.
22. MacDonald, I. J. and T. J. Dougherty (2001) Basic principles of photodynamic therapy. J. Porphyrins Phthalocyanines 5, 105-129.
23. Henderson, B. W. and T. J. Dougherty (1992) How does photodynamic therapy work. Photochem. Photobiol. 55, 145-157.
24. Henderson, B. W. and T. J. Dougherty, Eds. (1992) Photodynamic Therapy: Basic Principles and Clinical Applications. CRC Press, Boca Raton, FL.
25. Ali, H. and J. E. van Lier (1999) Metal complexes as photo- and radiosensitizers. Chem. Rev. 99, 2379-2450.
26. Castano, A. P., T. N. Demidova and M. R. Hamblin (2004) Mechnisms in photodynamic therapy: Part one - Photosensitizers, photochemistry and cellular localization. Photodiagn. Photodyn. Ther. 1, 279-293.
27. Castano, A. P., T. N. Demidova and M. R. Hamblin (2004) Mechnisms in photodynamic therapy: Part two - Cellular signaling, cell metabolism and modes of cell death. Photodiagn. Photodyn. Ther. 2, 1-23.
28. Castano, A. P., T. N. Demidova and M. R. Hamblin (2004) Mechnisms in photodynamic therapy: Part three - Photosensitizer pharmacokinetics, biodistribution, tumor localization and modes of tumor destruction. Photodiagn. Photodyn. Ther. 2, 91-106.
29. Bonnett, R., R. D. White, U. J. Winfield and M. C. Berenbaum (1989) Hydroporphyrins of the meso-tetra(hydroxyphenyl)porphyrin series as tumor photosensitizers. Biochem. J. 261, 277-280.
30. Berenbaum, M. C., S. L. Akande, R. Bonnett, H. Kaur, S. Ioannou, R. D. White and U. J. Winfield (1986) meso-Tetra(hydroxyphenyl)porphyrins, a new class of potent tumor photosensistizers with favorable selectivity. Br. J. Cancer 54, 717-725.
31. Qian, P., J. F. Evensen, C. Rimington and J. Moan (1987) A comparison of different photosensitizing dyes with respect to uptake C3H-tumors and tissues of mice. Cancer Lett. 36, 1-10.
32. Chevretton, E. B., M. C. Berenbaum and R. Bonnett (1992) The effect of photodynamic therapy on normal skeletal muscle in an animal model. Lasers Med. Sci. 7, 103-110.
33. Ringel, I., V. Gottfried, L. Levdansky, J. W. Winkelman and S. Kimel (1996) Photodynamic activity of porphines on tubulin assembly. Proc. SPIE Int. Soc. Opt. Eng. 2625, 156-163.
34. Peng, Q., J. Moan, J. Farrants, H. E. Danielsen and C. Rimington (1990) Localization of potent photosensitizers in human tumor LOX by means of laser scanning microscopy. Cancer Lett. 53, 129-139.
35. Peng, Q., J. Moan, J. M. Nesland, J. F. Evensen, M. Kongshaug and C. Rimington (1990) Localizing and photosensitizing mechanism by tetra(3-hydroxyphenyl)porphin in vivo on human malignant melanoma xenografts in athymic nude mice. Lasers Med. Sci. 5, 399-409.
36. Lindsay, E. A., M. C. Berenbaum, R. Bonnett and D. G. T. Thomas (1991) Photodynamic therapy of a mouse glioma: Intracranial tumours are resistant while subcutaneous tumours are sensitive. Br. J. Cancer 63, 242-246.
37. Peng, Q., J. Moan, G. Farrants, H. E. Danielsen and C. Rimington (1991) Localization of potent photosensitizers in human tumor LOX by means of laser scanning microscopy. Cancer Lett. 58, 17-27.
38. Lowe, K. C., S. L. Akande, R. Bonnett, R. D. While and M. C. Berenbaum (1992) Protective effects of a novel perfluorochemical emulsion in photodynamic therapy. Biomater. Artif. Cells Immobilization Biotechnol. 20, 925-927.
39. Berg, K. and J. Moan (1992) Mitotic inhibition by phenylporphines and tetrasulfonated aluminium phthalocyanine in combination with light. Photochem. Photobiol. 56, 333-339.
40. Ziolkowski, P., J. Milach, K. Symonowicz, P. Chielewski, L. Latos-Grazynski and E. Marcinkowska (1995) 5,20-bis(4-sulphophenyl)-10,15-bis(2-methoxy-4-sulphophenyl)-21-thiaporphyrin as a new potent sensitizer in photodynamic therapy. Tumori 81, 364-369.
41. Zenkevich, E., E. Sagun, V. Knyukshto, A. Shulga, A. Mironov, O. Efremova, R. Bonnett, S. P. Songca and M. Kassem (1996) Photophysical and photochemical properties of potential porphyrin and chlorin photosensitizers for PDT. J. Photochem. Photobiol. B: Biol. 33, 171-180.
42. Bonnett, R. and M. C. Berenbaum (Efamol Holdings plc., UK) (1989) Preparation of dihydro and tetrahydro derivatives of porphyrins for cancer phototherapy. Eur. Pat. Appl. 1989, EP 337601 A1 19891018.
43. Mitra, S. and T. H. Foster (2005) Photophysical parameters. photosensitizer retention and tissue optical properties completely account for the higher photodynamic efficacy of meso-tetrahydroxyphenyl-chlorin vs photofrin. Photochem. Photobiol. 81, 849-859.
44. Bonnett, R. (1995) Studies on 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin, mTHPC (Temoporfin). Proc. SPIE Int. Soc. Opt. Eng. 2371, 31-38.
45. Abulafi, A. M., M. L. DeJode, J. T. Allardice, J. K. Ansell and N. S. Williams (1997) Adjuvant intraoperative photodynamic therapy in experimental colorectal cancer using a new photosensitizer. Br. J. Surg. 84, 368-371.
46. Bonnett, R., B. D. Djelal, G. E. Hawkes, P. Haycock and F. Pont (1994) Fine-structure of 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (m-THPC) - A H-1, C- 13 and N-15 NMR study. J. Chem. Soc. Perkin Trans. 2, 1839-1843.
47. Jones, R. M., J. H. Lamb and C. K. Lim (1995) 5,10,15,20-mesoTetra(hydroxyphenyl)chlorin as a matrix for the analysis of low molecular weight compounds by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Rapid Commun. Mass Spectrom. 9, 968-969.
48. Kriska, T., L. Korecz, I. Nemes and D. Gal (1995) Physicochemical modeling of the role of free radicals in photodynamic therapy. III. Interactions of stable free radicals with excited photosensitisers studied by kinetic ESR spectroscopy. Biochem. Biophys. Res. Commun. 215, 192-198.
49. Bonnett, R., D. J. McGarvey, A. Harriman, E. J. Land, T. G. Truscott and U. J. Winfield (1988) Photophysical properties of meso-tetraphenylporphyrin and some meso-tetra(hydroxyphenyl)porphyrins. Photochem. Photobiol. 48, 271-276.
50. Bonnett, R., P. Charlesworth, B. D. Djelal, S. Foley, D. J. McGarvey and T. G. Truscott (1999) Photophysical properties of 5,10,15,20-tetrakis(m-hydroxyphenyl)porphyrin-(m-THPP), 5,10, 15,20-tetrakis(m-hydroxyphenyl)chlorin (m-THPC) and 5,10,15, 20-tetrakis(m-hydroxyphenyl)bacteriochlorin (m-THPBC): A comparative study. J. Chem. Soc. Perkin Trans. 2, 325-328.
51. Cunderlikova, B., E. G. Bjorklund, E. O. Pettersen and J. Moan (2001) pH-dependent spectral properties of Hp1X, TPPS2a, mTHPP and mTHPC. Photochem. Photobiol. 74, 246252.
52. Zimmermann, A., M. Ritsch-Marte and H. Kostron (2002) In vitro investigation on the pH dependence of the absorption and fluorescence properties of the photosensitizer mTHPC. Photochem. Photobiol. 75, 335-338.
53. Howe, L., A. Sucheta, O. Einarsdottir and J. Z. Zhang (1999) Time-resolved studies of the excited-state dynamics of mesotetra(hydroxylphenyl)chlorin in solution. Photochem. Photobiol. 69, 617-623.
54. Kress, M., T. Meier, R. Steiner, F. Dolp, R. Erdmann, U. Ortmann and A. Ruck (2003) Time-resolved microspectrofluorometry and fluorescence lifetime imaging of photosensitizers using picosecond pulsed diode lasers in laser scanning microscopes. J. Biomed. Opt. 8, 26-32.
55. Kruijt, B., A. Van Der Ploeg-Van Den Heuvel, H. S. De Bruijn, H. J. C. M. Sterenbourg, A. Amelink and D. J. Robinson (2009) Monitoring interstitial m-THPC-PDT in vivo using fluorescence and reflectance spectroscopy. Lasers Surg. Med. 41, 653-664.
56. Tikhomirov, A. M., T. A. Shmigol', E. A. Kozhinova, A. A. Kiagova, L. N. Bezdetnaia and A. I. Potapenko (2009) Investigation of aggregates of dyes by the method of resonance light scattering: Correction of spectra. Biofizika 54, 824-830.
57. Bonnett, R., B. D. Djelal and A. Nguyen (2001) Physical and chemical studies related to the development of m-THPC (FOSCAN®) for the photodynamic therapy (PDT) of tumours. J. Porphyrins Phthalocyanines 5, 652-661.
58. Cunderlikova, B., O. Kaalhus, R. Cunderlik, A. Mateasik, J. Moan and M. Kongshaug (2004) pH-dependent modification of lipophilicity of porphyrin-type photosensitizers. Photochem. Photobiol. 79, 242-247.
59. Wang, Q., H.-B. Ris, H. J. Altermatt, B. Reynolds, J. C. M. Stewart, R. Bonnett and C. K. Lim (1993) Determination of 5,10,15,20-tetra-(m-hydroxyphenyl)chlorin in human plasma by high-performance liquid-chromatography. Biomed. Chromatogr. 7, 45-47.
60. Wang, Q., H. J. Altermatt, H.-B. Ris, B. E. Reynolds, J. C. M. Stewart, R. Bonnett and C. K. Lim (1993) Determination of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin in tissues by high-performance liquid-chromatography. Biomed. Chromatogr. 7, 155-157.
61. Barberi-Heyob, M., H. Rezzoug, J. L. Merlin and F. Guillemin (1997) Sensitive isocratic liquid chromatographic assay for the determination of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin in plasma and tissue with electrochemical detection. J. Chromatogr. B 688, 331-338.
62. Desroches, M.-C., O. Bourdon, Y. Marokro, P. Chaminade, J. Blais, P. Progron and A. Kasselouri (2001) Importance of the ionization states of m-THPC for its HPLC fluorescence detection. Luminescence 16, 173-178.
63. Demore, D., A. Kasselouri, O. Bourdon, J. Blais, G. Mahuzier and G. Prognon (1999) Enhancement of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin fluorescence emission by inclusion in natural and modified cyclodextrins. Appl. Spectrosc. 53, 523-527.
64. Desroches, M. C., A. Kasselouri, O. Bourdon, P. Chaminade, J. Blais and P. Prognon (2001) A direct sensitized fluorimetric determination of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin [m-THPC (Foscan)®] in human plasma using a cyclodextrin inclusion complex. Analyst 126, 923-927.
65. Guo, X., W. An. S. Shuang, F. Cheng and C. Dong (2005) Study on spectroscopic characterization of meso-tetrakis (4-hydroxyphenyl) porphyrin (THPP) in ß-cyclodextrin and its derivatives. J. Photochem. Photobiol. A: Chem. 173, 258-263.
66. Zhan, Q., P. Voumard and R. Zenobi (1994) Chemical analysis of cancer therapy photosensitizers by 2-step laser mass spectrometry. Anal. Chem. 66, 3259-3266.
67. DaCosta, R. S., H. Andersson and B. C. Wilson (2003) Molecular fluorescence excitation-emission matrices relevant to tissue spectroscopy. Photochem. Photobiol. 78, 384-392.
68. Da Silva, F. A. M. and E. L. Newman (1993) Dynamic capillaroscopy: A minimally invasive technique for assessing photodynamic effects in vivo. Photochem. Photobiol. 58, 884-889.
69. Da Silva, F. A. M. and E. L. Newman (1995) Time-dependent photodynamic damage to blood vessels: Correlation with serum photosensitizer levels. Photochem. Photobiol. 61, 414-416.
70. Bonnett, R., B. D. Djelal, P. A. Hamilton, G. Martinez and F. Wierrani (1999) Photobleaching of 5,10,15,20-tetrakis (m-hydroxyphenyl) porphyrin (m-THPP) and the corresponding rin (m-THPC) and bacteriochlorin (m-THPBC). A comparative study. J. Photochem. Photobiol. B: Biol. 53, 136-143.
71. Bonnett, R. and G. Martinez (2002) Photobleaching of compounds of the 5,10,15,20-tetrakis(m-hydroxyphenyl)-porphyrin series (m-THPP, m-THPC, and m-THPBC). Org. Lett. 4, 20132016.
72. Lassalle, H.-P., N. Lourette, B. Maunit, J.-F. Muller, F. Guillemin and L. Bezdetnaya-Bolotine (2005) MALDI-TOF mass spectrometric analysis for the characterization of the 5,10,15,20tetrakis(m-hydroxyphenyl)bacteriochlorin (m-THPBC) photoproducts in biological environment. J. Mass Spectrom. 40, 11491156.
73. Jones, R. M., Q. Wang, J. H. Lamb, B. D. Djelal, R. Bonnett and C. K. Lim (1996) Identification of photochemical oxidation products of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin by on-line high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. J. Chromatogr. A 722, 257-265.
74. Angotti, M., B. Maunit, J.-F. Muller, L. Bezdetnaya and F. Guillemin (1999) Matrix-assisted laser desorption/ionization coupled to Fourier transform ion cyclotron resonance mass spectrometry: A method to characterize temoporpfin photoproducts. Rapid Commun. Mass Spectrom. 13, 597-603.
75. Angotti, M., B. Maunit, J.-F. Muller, L. Bezdetnaya and F. Guillemin (2001) Characterization by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry of the major photoproducts of temoporfin (mTHPC) and bacteriochlorin (m-THPBC). J. Mass Spectrom. 36, 825-831.
76. Kasselouri, A., O. Bourdon, D. Demore, J. C. Blais, P. Prognon, G. Bourg-Heckly and J. Blais (1999) Fluorescence and mass spectrometry studies of meta-tetra(hydroxyphenyl)chlorin photoproducts. Photochem. Photobiol. 70, 275-279.
77. Lourette, N., B. Maunit, L. Bezdetnaya, H.-P. Lassalle, F. Guillemin and J.-F. Muller (2005) Characterization of photoproducts of m-THPP in aqueous solution. Photochem. Photobiol. 81, 691-696.
78. Chen, Y., L. Li, M. Zhang and T. Shen (2001) An explanation to the high efficiency of m-THPC (temporfin) used in photodynamic therapy. Chin. Sci. Bull. 46, 823-827.
79. Chen, Y., S. Xu, L. Li, M. Zhang, J. Shen and T. Shen (2001) Active oxygen generation and photo-oxygenation involving temporfin (m-THPC). Dyes Pigments 51, 63-69.
80. Ma, L. W., J. Moan and K. Berg (1994) Comparison of the photobleaching effect of three photosensitizing agents: Meso-tetra (m-hydroxyphenyl)chlorin, meso-tetra(m-hydroxyphenyl) porphyrin and photofrin during photodynamic therapy. Lasers Med. Sci. 9, 127-132.
81. Hadjur, C., N. Lange, J. Rebstein, P. Mounier, H. van den Bergh and G. Wagnieres (1998) Spectroscopic studies of photobleaching and photoproduct formation of meta(tetrahydroxyphenyl)chlorin (m-THPC) used in photodynamic therapy. The production of singlet oxygen by m-THPC. J. Photochem. Photobiol. B: Biol. 45, 170-178.
82. McIlroy, B. W., T. S. Mann, J. S. Dysart and B. C. Wilson (2002) The effects of oxygenation and photosensitizer substrate binding on the use of fluorescence photobleaching as a dose metric for photodynamic therapy. Vib. Spectrosc. 28, 25-35.
83. Dysart, J. S., G. Singh and M. S. Patterson (2005) Calculation of singlet oxygen dose from photosensitizer fluorescence and photobleaching during mTHPC photodynamic therapy of MLL cells. Photochem. Photobiol. 81, 196-205.
84. Atif, M., M. R. Stringer, J. E. Cruse-Sawyer, P. E. Dyer and S. B. Brown (2005) The influence of intracellular mTHPC concentration upon photobleaching dynamics. Photodiagn. Photodyn. Ther. 2, 235-238.
85. Dysart. J. S., M. S. Patterson, T. J. Farrell and G. Singh (2002) Relationship between mTHPC fluorescence photobleaching and cell viability during in vitro photodynamic treatment of DP16 cells. Photochem. Photobiol. 75, 289-295.
86. Atif, M., M. R. Stringer, J. E. Cruse-Sawyer and S. B. Brown (2004) Fluence-rate effects upon m-THPC photobleaching in a formalin-fixed cell system. Photodiagn. Photodyn. Ther. 1, 173180.
87. Bonnett, R. and G. Martinez (2001) Photobleaching of sensitisers used in photodynamic therapy. Tetrahedron 57, 9513-9547.
88. Belitchenko, J., V. Melnikova, L. Bezdetnaya, H. Rezzoug, J. L. Merlin, A. Potapenko and F. Guillemin (1998) Characterization of photodegradation of meta-tetra(hydroxyphenyl)chlorin (mTHPC) in solution: Biological consequences in human tumor cells. Photochem. Photobiol. 67, 584-590.
89. Moan, J., V. Iani, L.-W. Ma and Q. Peng (1996) Photodegradation of sensitizers in mouse skin during PCT. Proc. SPIE Int. Soc. Opt. Eng. 2625, 187-193.
90. Kunz, L. and A. J. MacRobert (2002) Intracellular photobleaching of 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (Foscan®) exhibits a complex dependence on oxygen level and fluence rate. Photochem. Photobiol. 75, 28-35.
91. Finlay, J. C., S. Mitra and T. H. Foster (2002) In vivo mTHPC photobleaching in normal rat skin exhibits unique irradiance-dependent features. Photochem. Photobiol. 75, 282-288.
92. Uzdensky, A. B., V. Iani, L.-W. Ma and J. Moan (2002) Photobleaching of hypericin bound to human serium albumin, cultured adenocarcinoma cells and nude mice skin. Photochem. Photobiol. 76, 320-328.
93. Ferreira, J., P. F. C. Menezes, C. Kurachi, C. Sibata, R. R. Allison and V. S. Bagnato (2008) Photostability of different chlorine photosensitizers. Laser Phys. Lett. 5, 156-161.
94. Ma, L. W., E. Bjørklund and J. Moan (1999) Photochemotherapy of tumours with mesotetrahydroxylphenyl chlorin is pH dependent. Cancer Lett. 138, 197-201.
95. Friberg, E. G., B. Cunderlikova, E. O. Pettersen and J. Moan (2003) pH effects on the cellular uptake of four photosensitizing drugs evaluated for use in photodynamic therapy of cancer. Cancer Lett. 195, 73-80.
96. Moan, J., L. W. Ma and E. Bjørklund (1999) The effect of glucose and temperature on the in vivo efficiency of photochemotherapy with meso-tetra-hydroxyphenyl-chlorin. J. Photochem. Photobiol. B: Biol. 50, 94-98.
97. Kessel, D. (1999) Transport and localization of m-THPC in vitro. Int. J. Clin. Pract. 53, 263-267.
98. Michael-Titus, A. T., R. Whelpton and Z. Yaqub (1995) Binding of Temoporfin to the lipoprotein fractions of human serum. Br. J. Clin. Pharmacol. 40, 594-597.
99. An, W., Y. Jiao, C. Dong, C. Yang, Y. Inoue and S. Shuang (2009) Spectroscopic and molecular modeling of the binding of meso-tetrakis(4-hydroxypheny))porphyrin to human serum albumin. Dyes Pigments 81, 1-9.
100. Rezzoug, H., L. Bezdetnaya, O. A'amar, J. L. Merlin and F. Guillemin (1998) Parameters affecting photodynamic activity of Foscan® or meta-tetra(hydroxyphenyl)chlorin (mTHPC) in vitro and in vivo. Lasers Med. Sci. 13, 119-125.
101. Ball, D. J., D. I. Vernon and S. B. Brown (1999) The high photoactivity of m-THPC in photodynamic therapy. Unusually strong retention of m-THPC by RIF-1 cells in culture. Photochem. Photobiol. 69, 360-363.
102. Sasnouski, S., V. Zorin, I. Khludeyev, M. A. D'Hallewin, F. Guillemin and L. Bezdetnaya (2005) Investigation of Foscan® interactions with plasma proteins. Biochim. Biophys. Acta 1725. 394-402.
103. Lassalle, H.-P., M. Wagner, L. Bezdetnaya, F. Guillemin and H. Schneckenburger (2008) Fluorescence imaging of Foscan® and Foslip in the plasma membrane and in whole cells. J. Photochem. Photobiol. B: Biol 92, 47-53.
104. Sasnouski, S., D. Kachatkou, V. Zorin, F. Guillemin and L. Bezdetnaya (2006) Redistribution of Foscan® from plasma proteins to model membranes. Photochem. Photobiol. Sci. 5, 770777.
105. Hanisch, F. D., H. B. Steen and J. Moan (1996) Flow cytometric studies of cellular uptake of PII, m-THPP and m-THPC: Kinetics and cell density dependence. Proc. SPIE Int. Soc. Opt. Eng. 2624,
106. Veenuizen, R., H. Oppelaar, M. Ruevekamp, J. Schellens, O. Dalesio and F. Stewart (1997) Does tumour uptake of Foscan determine PDT efficacy? Int. J. Cancer 73, 236-239.
107. Triesscheijn, M., M. Ruevekamp, R. Out, T. J. C. Van Berkel, J. Schellens, P. Baas and F. A. Stewart (2007) The pharmacokinetic behavior of the photosensitizer meso-tetra-hydroxyphenyl-chlorin in mice and men. Cancer Chemother. Pharmacol 60, 113-122.
108. Hudson, R. and R. W. Boyle (2004) Strategies for selective delivery of photodynamic sensitisers to biological targets. J. Porphyrins Phthalocyanines 8, 954-975.
109. Berg, K., K. Madslien, J. C. Bommer, R. Oftebro, J. W. Winkelman and J. Moan (1991) Light induced relocalization of sulfonated meso-tetraphenylporphines in NHIK 3025 cells and effects of dose fractionation. Photochem. Photobiol. 53, 203-210.
110. Kessel, D., M. Antolovich and K. M. Smith (2001) The role of the peripheral benzodiazepine receptor in the apoptotic response to photodynamic therapy. Photochem. Photobiol. 74, 346-349.
111. Mojzisova, H., S. Bonneau and D. Brault (2007) Structural and physico-chemical determinants of the interactions of macrocyclic photosensitizers with cells. Eur. Biophys. J. 36, 943-953.
112. Melnikova, V. O., L. N. Bezdetnaya, C. Bour, E. Festor, M. Gramain, J. L. Merlin, A. Y. Potapenko and F. Guillemin (1999) Subcellular localization of meta-tetra(hydroxyphenyl) chlorin in human tumor cells subjected to photodynamic treatment. J. Photochem. Photobiol. B: Biol. 49, 96-103.
113. Ma, L., J. Moan and K. Berg (1994) Evaluation of a new photosensitizers, meso-tetra-hydroxyphenyl-chlorin, for use in photodynamic therapy: A comparison of its photobiological properties with those of two other photosensitizers. Int. J. Cancer 57, 883-888.
114. Connelly, J. P., S. W. Botchway, L. Kunz, D. Pattison, A. W. Parker and A. J. MacRobert (2001) Time-resolved fluorescence imaging of photosensitiser distribution in mammalian cells using a picosecond laser line-scanning microscope. J. Photochem. Photobiol. A: Chem. 142, 169-175.
115. Foster, T. H., B. D. Pearson, S. Mitra and C. E. Bigelow (2005) Fluorescence anisotropy imaging reveals localization of meso-tetrahydroxyphenyl chlorin in the nuclear envelope. Photochem. Photobiol. 81, 1544-1547.
116. Leung, W. N., X. Sun, N. K. Mak and C. M. N. Yow (2002) Photodynamic effects of mTHPC on human colon adenocarcinoma cells: Photocytotoxicity, subcellular localization and apoptosis. Photochem. Photobiol. 75, 406-411.
117. Teiten, M.-H., L. Bezdetnaya, P. Morliere, R. Santus and F. Guillemin (2003) Endoplasmatic reticulum and Golgi apparatus are the preferential sites of Foscan® localisation in cultured tumour cells. Br. J. Cancer 88, 146-152.
118. Teiten, M.-H., S. Marchal, M. A. D'Hallewin, F. Guillemin and L. Bezdetnaya (2003) Primary photodamage sites and mitochondrial events after Foscan® photosensitization of MCF-7 human breast cancer cells. Photochem. Photobiol. 78, 9-14.
119. Tsuchida, M., Y. Emi, Y. Kida and M. Sakaguchi (2008) Human ABC transporter isoform B6 (ABCB6) localizes primarily in the Golgi apparatus. Biochem. Biophys. Res. Commun. 369, 369-375.
120. Peng, Q., J. Moan, L.-W. Ma and J. M. Nesland (1995) Uptake, localization, and photodynamic effect of meso-tetra(hydroxyphenyl)porphine and its corresponding chlorin in normal and tumor tissues of mice bearing mammary carcinoma. Cancer Res. 55, 2620-2626.
121. Andrejevic, S., J. F. Savary, P. Monnier, C. Fontolliet, D. Braichotte, G. Wagnieres and H. van den Bergh (1996) Measurements by fluorescence microscopy of the time-dependent distribution of meso-tetra-hydroxyphenylchlorin in healthy tissues and chemically induced "early" squamous cell carcinoma of the Syrian hamster cheek pouch. J. Photochem. Photobiol B: Biol. 36, 143-151.
122. Mitra, S., E. Maugain, L. Bolotine, F. Guillemin and T. H. Foster (2005) Temporally and spatially heterogenous distribution of mTHPC in a murine tumor observed by two-color confocal fluorescence imaging and spectroscopy in a whole-mount model. Photochem. Photobiol. 81, 1123-1130.
123. Cai, H., Q. Wang, L. Luo and C. K. Lim (1999) In vitro and in vivo metabolism of 5,10,15,20-tetra(m-hydroxyphenyl)chlorin in rats and humans. Biomed. Chromatogr. 13, 184-186.
124. Cai, H., Q. Wang, L. Luo and C. K. Lim (1999) Study of temoporfin metabolism by HPLC and electrospray mass spectrometry. Biomed. Chromatogr. 13, 354-359.
125. Hopkinson, H. J., D. I. Vernon and S. B. Brown (1999) Identification and partial characterization of an unusual distribution of the photosensitizer meta-tetrahydroxyphenyl chlorin (temoporfin) in human plasma. Photochem. Photobiol. 69, 482-488.
126. Whelpton, R., A. T. Michael-Titus, R. P. Jamdar, K. Abdillahl and M. F. Grahn (1996) Distribution and excretion of radiolabeled Temoporfin in a murine tumor model. Photochem. Photobiol. 63, 885-891.
127. Andrejevic-Blant, S., C. Hadjur, J.-P. Ballini, G. Wagnieres, C. Fontolliet, H. van den Bergh and P. Monnier (1997) Photodynamic therapy of early squamous cell carcinoma with tetra(m-hydroxyphenyl)chlorin: Optimal drug-light interval. Br. J. Cancer 76, 1021-1028.
128. Kascáková, S., B. Kruijt, H. S. de Bruijn, A. van der Ploeg-van den Heuvel, D. J. Robinson, H. J. C. M. Sterenborg and A. Amelink (2008) Ex vivo quantification of mTHPC concentration in tissue: Influence of chemical extraction on the optical properties. J. Photochem. Photobiol B: Biol. 91, 99-107.
129. Moore, J. V., C. M. West and C. Whitehurst (1997) The biology of photodynamic therapy. Phys. Med. Biol. 42, 913-935.
130. Ronn, A. M., M. Nouri, L. A. Lofgren, B. M. Steinberg, A. Westerborn, T. Windahl, M. J. Shikowitz and A. L. Abramson (1996) Human tissue levels and plasma pharmacokinetics of temoporfin (Foscan®, mTHPC). Laser Med Sci. 11, 267-272.
131. Glanzmann, T., C. Hadjur, M. Zellweger, P. Grosjean, M. Forrer, J.-P. Ballini, P. Monnier, H. Van Den Bergh, C. K. Lim and G. Wagnieres (1998) Pharmacokinetics of tetra(m-hydroxy- phenyl)chlorin in human plasma and individualized light dosimetry in photodynamic therapy. Photochem. Photobiol. 67, 596-602.
132. Wagnieres, G., C. Hadjur, P. Grosjean, D. Braichotte, J.-F. Savary, P. Monnier and H. Van Den Bergh (1998) Clinical evaluation of the cutaneous phototoxicity of 5,10,15,20-tetra (m-hydroxyphenyl)chlorin. Photochem. Photobiol. 68, 382-387.
133. Ronn, A. M. (1999) Pharmacokinetics in photodynamic therapy. Rev. Contemp. Pharmacother. 10, 39-46.
134. Whelpton, R., A. T. Michael-Titus, S. S. Basra and M. Grahn (1995) Distribution of temoporfin, a new photosensitizers for the photodynamic therapy of cancer, in a murine tumor model. Photochem. Photobiol. 61, 397-401.
135. Garrier, J., A. Bressenot, S. Gräfe, S. Marchal, S. Mitra, T. H. Foster, F. Guillemin and L. Bezdetnaya (2010) Compartmental targeting for mTHPC-based photodynamic treatment in vivo: Correlation of efficiency, pharmacokinetics, and regional distribution of apoptosis. Int. J. Radiation Oncology Biol. Phys. 78, 563-571.
136. Mang, T. S. (2008) Dosimetric concepts for PDT. Photodiagn. Photodyn. Ther. 5, 217-223.
137. Ronn, A. M., J. Batti, C. J. Lee, D. Yoo, M. E. Siegel, M. Nouri, L. A. Lofgren and B. M. Steinberg (1997) Comparative biodistribution of meta-tetra(hydroxyphenyl) chlorin in multiple species: Clinical implications for photodynamic therapy. Laser Surg. Med. 20, 437-442.
138. Grahn, M. F., M. L. De Jode, M. G. Dilkes, J. K. Ansell, D. Onwu, J. Maudsley and N. S. Williams (1997) Tissue photosensitizer detection by low-power remittance fluorescence. Lasers Med. Sci. 12, 245-252.
139. Bourré, L., S. Thibaut, A. Briffaud, N. Rousset, S. Eléouet, Y. Lajat and T. Patrice (2002) Indirect detection of photosensitizer ex vivo. J. Photochem. Photobiol. B:Biol. 67, 23-31.
140. Drakaki, E., M. Makropoulou, E. Mallas and A. A. Serafetinides (1999) Dosimetry in photodynamic therapy and laser induced fluorescence spectroscopy. Proc. SPIE Int. Soc. Opt. Eng. 3571, 392-396.
141. Wang, K. K.-H., S. Mitra and T. H. Foster (2008) Photodynamic dose does not correlate with long-term tumor response to mTHPC-PDT performed at several drug-light intervals. Med. Phys. 35, 3518-3526.
142. Stewart, F., P. Baas and W. Star (1998) What does photodynamic therapy have to offer radiation oncologists (or their cancer patients)? Radiother. Oncol. 48, 233-248.
143. Konan, Y. N., R. Gurny and E. Allemann (2002) State of the art in the delivery of photosensitizers for photodynamic therapy. J. Photochem. Photobiol. B.Biol. 66, 89-106.
144. Turchiello, R. F., F. C. B. Vena, P. Maillard, C. S. Souza, M. V. B. L. Bentley and A. C. Tedesco (2003) Cubic phase gel as a drug delivery system for topical application of 5-ALA, its ester derivatives and m-THPC in photodynamic therapy (PDT). J. Photochem. Photobiol. B.Biol. 70, 1-6.
145. Fiedler, D. M., F. Wierrani, G. Schnitzhofer, J. C. M. Stewart, K. Gharehbaghi. W. Grünberger and B. Kammer (1997) Does the in-vitro efficiency of meso-tetrahydroxy-phenyl-chlorin depend on pre-treatment of sensitizer? J. Photochem. Photobiol. B: Biol. 38, 241-244.
146. Chatterjee, D. K., L. S. Fong and Y. Zhang (2008) Nanoparticles in photodynamic therapy: An emerging paradigm. Adv. Drug Deliv. Rev. 60, 1627-1637.
147. Paszko, E., C. Ehrhard, M. O. Senge, D. P. Kelleher and J. V. Reynolds (2011) Nanodrug applications in photodynamic therapy. Photodiagn. Photodyn. Ther. 8, 224-231.
148. Ris, H.-B., H. J. Altermatt, B. Nachbur, J. C. M. Stewart, Q. Wang, C. K. Lim, R. Bonnett and U. Althaus (1993) Effect of drug-light interval on photodynamic therapy with meta-tetrahydroxyphenylchlorin in malignant mesothelioma. Int. J. Cancer 53, 141-146.
149. Ris, H.-B., H. J. Altermatt, C. M. Stewart, T. Schaffner, Q. Wang, C. K. Lim, R. Bonnett and U. Althaus (1993) Photodynamic therapy with m-tetrahydroxyphenylchlorin in vivo: Optimization of the therapeutic index. Int. J. Cancer 55, 245-249.
150. Veenhuizen, R. B., M. C. Ruevekamp-Helmers, T. J. M. Helmerhorst, P. Kenemans, W. J. Mooi, J. P. A. Marunissen and F. A. Stewart (1994) Intraperitoneal photodynamic therapy in the rat: Comparison of toxicity profiles for Photofrin and MTHPC. Int. J. Cancer 59, 830-836.
151. Veenhuizen, R. B., M. C. Ruevekamp, H. Oppelaar, B. Ransforp, M. van de Vijver, T. J. M. Heimerhorst, P. Kenemans and F. A. Stewart (1997) Intraperitoneal photodynamic therapy: Comparison of red and green light distribution and toxicity. Photochem. Photobiol. 66, 389-395.
152. van Geet, I. P. J., H. Oppelaar, J. P. A. Marijnissen and F. A. Stewart (1996) Influence of fractionation and fluence rate in photodynamic therapy with Photofrin of mTHPC. Radial. Res. 145, 602-609.
153. Müller, S., H. Wall, D. Dobler-Girdziunaite, D. Fiedler and U. Haller (1998) Enhanced photodynamic effects using fractionated laser light. J. Photochem. Photobiol B: Biol. 42, 67-70.
154. Fiedler, D. M., G. Schnitzhofer, H. Wall. D. Dobler-Girdziunaite and B. Krammer (2000) Photodynamic cytotoxicity enhancement by pulsed diode laser irradiation. Laser. Med. 15, 107-114.
155. Blant, S. A., A. Woodtli, G. Wagnieres, C. Fontolliet, H. van den Bergh and P. Monnier (1996) In vivo fluence rate effect in photodynamic therapy of early cancers with tetra(m-hydroxyphenyl)chlorin. Photochem. Photobiol. 64, 963-968.
156. Tsutsui, H., A. J. MacRobert, A. Curnow, A. Rogowska, G. Buonaccorsi, H. Kato and S. G. Bown (2002) Optimisation of illumination for photodynamic therapy with mTHPC on normal colon and a transplantable tumour in rats. Lasers Med. Sci. 17, 101-109.
157. Coutier, S., L. N. Bezdetnaya, T. H. Foster, R.-M. Paraché and F. Guillemin (2002) Effect of irradiation fluence rate on the efficacy of photodynamic therapy and tumor oxygenation in meta-tetra (hydroxyphenyl) chlorin (mTHPC)-sensitized HT29 xenografts in nude mice. Radiat. Res. 158, 339-345.
158. Melnikova, V. O., L. N. Bezdetnaya, A. Y. Potapenko and F. Guillemin (1999) Photodynamic properties of meta-tetra(hydroxyphenyl)chlorin in human tumor cells. Radiat. Res. 152, 428-435.
159. Almeida, R. D., B. J. Manadas, A. P. Carvalho and C. B. Duarte (2004) Intracellular signaling mechanisms in photodynamic therapy. Biochim. Biophys. Acta 1704, 59-86.
160. Nowis, D., T. Skoklosa, M. Legat, T. Issat, M. Jakobisiak and J. Golab (2005) The influence of photodynamic therapy on the immune response. Photodiagn. Photodyn. Ther. 2, 283-298.
161. Breitenbach, T., M. K. Kuimova, P. Gbur, S. Hatz, N. B. Schack, B. W. Pedersen, J. D. C. Lambert, L. Poulsen and P. R. Ogilby (2009) Photosensitized production of singlet oxygen: Spatially-resolved optical studies in single cells. Photochem. Photobiol. Sci. 8, 442-452.
162. Buyaert, E., M. Dewaele and P. Agostinis (2007) Molecular effectors of multiple cell death pathways initiated by photodynamic therapy. Biochim. Biophys. Acta 1776, 86-107.
163. Reeves, K. J., M. W. R. Reed and N. J. Brown (2009) Is nitric oxide important in photodynamic therapy. J. Photochem. Photobiol. B:Biol. 95, 141-147.
164. Chen, J. Y., N. K. Mak, C. M. N. Yow, M. C, Fung, L. C. Chiu, W. N. Leung and N. H. Cheung (2000) The binding characteristics and intracellular localization of temoporfin (mTHPC) in myeloid leukemia cells: Phototoxicity and mitochondrial damage. Photochem. Photobiol. 72, 541-547.
165. Marchal, S., L. Bezdetnaya and F. Guillemin (2004) Modality of cell death induced by Foscan®-based photodynamic treatment in human colon adenocarcinoma cell line HT29. Biochem. (Moscow) 69, 45-49 [Biokhimiya (2004) 69, 57-63].
166. Yow, C. M. N., J. Y. Chen, N. K. Mak, N. H. Cheung and A. W. N. Leung (2000) Cellular uptake, subcellular localization and photodamaging effect of Temoporfin (mTHPC) in nasopharyngeal carcinoma cells: Comparison with hematoporphyrin derivative. Cancer Lett. 157, 123-131.
167. Marchal, S., A. Fadloun, E. Maugain, M.-A. D'Hallewin, F. Guillemin and L. Bezdetnaya (2005) Necrotic and apoptotic features of cell death in response to Foscan® photo sensitization of HT29 monolayer and multicell spheroids. Biochem. Pharmacol. 69, 1167-1176.
168. Melnikova, V., L. Bezdetnaya, I. Belitchenko, A. Potapenko, J.-L. Merlin and F. Guillemin (1999) Meta-tetra(hydroxyphenyl)chlorin-sensitized photodynamic damage of cultured tumor and normal cells in the presence of high concentrations of a-tocopherol. Cancer Lett. 139, 89-95.
169. Korbelik, M., V. R. Naraparaju and N. Yamamoto (1998) The value of serum a-N-acetylglactosaminidase measurement for the assessment of tumour response to radio- and photodynamic therapy. Br. J. Cancer 77, 1009-1014.
170. Korbelik, M., J. Sun and P. W. Payne (2003) Activation of poly(adenosine diphosphate-ribose) polymerase in mouse tumors treated by photodynamic therapy. Photochem. Photobiol, 78, 400-406.
171. Klein, S. D., H. Walt and C. Richter (1997) Photosensitization of isolated rat liver mitochondria by tetra(m-hydroxyphenyl)chlorin. Arch. Biochem. Biophys. 348, 313-319.
172. Ball, D. J., S. Mayhew, D. I. Vernon. M. Griffin and S. B. Brown (2001) Decreased efficiency of trypsinization of cells following photodynamic therapy: Evaluation of a role for tissue transglutaminase. Photochem. Photobiol. 73, 47-53.
173. Verrico, A. K. and J. V. Moore (1997) Expression of the collagenrelated heat shock protein HSP47 in fibroblasts treated with hypothermia or photodynamic therapy. Br. J. Cancer 16. 719-724.
174. Verrico, A. K., A. K. Haylett and J. V. Moore (2001) In vivo expression of the collagen-related heat shock protein HSP47, following hyperthermia or photodynamic therapy. Lasers Med. Surg. 16, 192-198.
175. Mitra, S., E. M. Goren, J. G. Freilinger and T. H. Foster (2003) Activation of heat shock protein 70 promoter with meso-tetrahydroxyphenyl chlorin photodynamic therapy reported by green fluorescent protein in vitro and in vivo. Photochem. Photobiol. 78. 615-622.
176. Sasnauskiene, A., J. Kadziauskas, N. Vezelyte, V. Jonusiene and V. Kirveliene (2009) Apoptosis, autophagy and cell cycle arrest following photodamage to mitochondrial interior. Apoptosis 14.
177. Oleinick, N. L., R. L. Morris and I. Belichenko (2002) The role of apoptosis in response to photodynamic therapy: What, where, why, and how. Photochem. Photobiol. Sci. 1, 1-21.
178. Uzdensky, A. B. (2008) Signal transduction and photodynamic therapy. Curr. Signal Transduct. Ther. 3, 55-74.
179. Dewaele, M., H. Maes and P. Agostinis (2010) ROS-mediated mechanisms of autophagy stimulation and their relevance in cancer therapy. Autophagy 6, 838-854.
180. Kirveliene, V., L. Prasmickaite. J. Kadziauskas, R. Bonnett, B. D. Djelal and B. Juodka (1997) Post-exposure processes in Temoporfin-photosensitized cell in vitro: Reliance on energy metabolism. J. Phoiochem. Photobiol. B: Biol. 41. 173-180.
181. Kirveliene. V., A. Sadauskaite, J. Kadziauskas, S. Sasnauskiene and B. Jodka (2003) Correlation of death modes of photosensitized cells with intracellular ATP concentration. FEBS Lett. 553, 167-172.
182. Bourré, L., N. Rousset, S. Thibaut, S. Eléouet. Y. Lajat and T. Patrice (2002) PDT effects of m-THPC and ALA, phototoxicity and apoptosis. Apoptosis 7, 221-230.
183. Thibaut, S., L. Bourré. D. Hernot, N. Rousset, Y. Lajat and T. Patrice (2002) Effects of BAPTA-AM, Forskokin, DSF and Z.VAD.fmk on PDT-induced apoptosis and m-THPC phototoxicity on B16 cells. Apoptosis 7, 99-106.
184. Heinzelmann-Schwarz, V., A. Fedier, R. Hornung, H. Walt. U. Haller and D. Fink (2003) Role of p53 and ATM in photodynamic therapy-induced apoptosis. Lasers Surg. Med. 33, 182-189.
185. Bressenot, A., S. Marchai, L. Bezdetnaya, J. Garner, F. Guillemin and F. Plénat (2009) Assessment of apoptosis by immunohistochemisiry to active caspase-3, active caspase-7, or cleaved PARP in monolayer cells and spheroid and subcutaneous xenografts of human carcinoma. J. Histochem. Cytochem. 57, 289-300.
186. Chen, J. Y., N. K. Mak, J. M. Wen, W. N. Leung, S. C. Chen, M. C. Fung and N. H. Cheung (1998) A comparison of the photodynamic effects of temoporfin (mTHPC) and MC540 on leukemia cells: Efficacy and apoptosis. Photochem. Photobiol. 68, 545-554.
187. Lilge, L., M. Portnoy and B. C. Wilson (2000) Apoptosis induced in vivo by photodynamic therapy in normal brain and intracranial tumour tissue. Br. J. Cancer 83, 1110-1117.
188. Klein, S. D., H. Walt, S. Rocha, P. Ghafourifar, M. Pruschy, K. H. Winterhalter and C. Richter (2001) Overexpression of Bcl-2 enhances sensitivity of L929 cells to a lipophilic cationic photosensitizer. Cell Death Different. 8, 204-206.
189. Kessel, D. and M. Castelli (2001) Evidence that bcl-2 is the target of three photosensitizers that induce a rapid apoptotic response. Photochem. Photobiol. 74, 318-322.
190. Marchal, S., A. François, D. Dumas, F. Guillemin and L. Bezdetnaya (2007) Relationship between subcellular localisation of Foscan® and caspase activation in photosensitised MCF-7 cells. Br. J. Cancer 96, 944-951.
191. Pittet, O., D. Petermann, D. Michod, T. Krueger, C. Cheng, H.B. Ris and C. Widmann (2007) Effect of the TAT-RasGAP317326 peptide on apoptosis of human malignant mesothelioma cells and fibroblasts exposed to meso-tetra-hydroxyphenyl-chlorin and light, J. Photochem. Photobiol. B:Biol. 88, 29-35.
192. Dahle, J., O. Kaalhus, J. Moan and H. B. Steen (1997) Cooperative effects of photodynamic treatment of cells in microcolonies. Proc. Natl Acad. Sci. USA 94, 1773-1778.
193. Dahle, J., E. Angell-Petersen, H. B. Steen and J. Moan (2001) Bystander elTects in cell death induced by photodynamic treatment, UVA radiation and inhibitors of ATP synthesis. Photochem. Photobiol. 73, 378-387.
194. Oleinick, N. L. and H. H. Evans (1998) The photobiology of photodynamic therapy: Cellular targets and mechanisms. Radiat. Res. 150, S146-S156.
195. Evans. H. H., M. F. Horng, M. Rcanati, J. T. Deahl and N. L. Oleinick (1997) Mutagenicity of photodynamic therapy as compared to UVC and ionizing radiation in human and murine lymphoblast cell lines. Photochem. Photobiol. 66, 690-696.
196. Schweizer, P. M., H. Walt, M. Fehr and U. Haller (1997) Basic research on the biology of meta-tetra(hydroxyphenyl) chlorin for photodynamic therapy in gynaecology: Somatic genotoxicity assayed with Drosophila melanogaster. Lasers Med. Sci. 12, 280284.
197. McNair, F. I., B. Marples, C. M. L. West and J. V. Moore (1997) A comet assay of DNA damage and repair in K652 cells after photodynamic therapy using haematoporphyrin derivative, methylene blue and meso-tetrahydroxyphenylchlorin. Br. J. Cancer 75, 1721-1729.
198. Rousset, N., E. Kerninon. S. Eléouet. T. L. Néel. J.-L. Auget, V. Vonarx. J. Carré, Y. Lajat and T. Patrice (2000) Use of alkaline Comet assay to assess DNA repair after m-THPC-PDT. J. Photochem. Photobiol. B:Biol. 56, 118-131.
199. Triesscheijn, M., M. Ruevekamp, M. Aalders, P. Baas and F. A. Stewart (2004) Comparative sensitivity of microvascular endothelial cells, fibroblasts and tumor cells after in vitro photodynamic therapy with meso-tetra-hydroxyphenyl-chlorin. Photochem. Photobiol. 80, 236-241.
200. Hornung, R., H. Walt, N. E. A. Crompton, K. A. Keefe, B. Jentsch, G. Perewusnyk, U. Haller and O. R. Köchli (1998) m-THPC-mediated photodynamic therapy (PDT) does not induce resistance to chemotherapy, radiotherapy or PDT on human cancer cells in vitro. Phoiochem. Photobiol. 68, 569-574.
201. Schwarz, V. A., R. Hornung, A. Fedier, M. K. Fehr, H. Walt, U. Haller and D. Fink (2002) Photodynamic therapy of DNA mismatch repair-deficient and -proficient tumour cells. Br. J. Cancer 86, 1130-1135.
202. van Geel, I. P. J., H. Oppelaar, Y. G. Oussoren, J. J. Schuitmaker and F. A. Stewart (1995) Mechanism for optimising photodynamic therapy - Second generation photosensitisers in combination with mitomycin C. Br. J. Cancer 72, 344-350.
203. Nelson, J. S., L.-H. Liaw, A. Orenstein, W. G. Roberts and M. W. Berns (1988) Mechanism of tumor destruction following photodynamic therapy will hematoporphyrin derivative, chlorin and phthalocyanine. J. Natl Cancer Inst. 80. 1599-1605.
204. Jones, H. J., D. I. Vernon and S. B. Brown (2003) Photodynamic therapy effect of m-THPC (Foscan®) in vivo: Correlation with pharmacokinetics. Br. J. Cancer 89, 398-404.
205. Maugain, E., S. Sasnouski, V. Zorin, J.-L. Merlin, F. Guillemin and L. Bezdetnaya (2004) Foscan®-based photodynamic treatment in vivo: Correlation between efficacy and Foscan accumulation in tumor, plasma and leukocytes. Oncol. Rep. 12, 639-645.
206. Triesscheijn, M., M. Ruevekamp, M. Aalders, P. Baas and F. A. Stewart (2005) Outcome of mTHPC mediated photodynamic therapy is primarily determined by the vascular response. Photochem. Photobiol. 81, 1161-1167.
207. Golinick. S. O., L. Vaughan and B. W. Henderson (2002) Generation of effective antitumor vaccines using photodynamic therapy. Cancer Res. 62, 1604-1608.
208. Castano, A. P., P. Mroz and M. R. Hamblin (2006) Photodynamic therapy and anti-tumour immunity. Nature Rev. Cancer 6, 535-545.
209. Dougherty, T. J., C. J. Gomer, B. W. Henderson, G. Jori, D. Kessel, M. Korbelik, J. Moan and Q. Peng (1998) Photodynamic therapy, J. Natl Cancer Inst. 90, 889-905.
210. Korbelik, M. and I. Cecic (1998) Enhancement of tumour response to photodynamic therapy by adjuvant mycobacterium cell-wall treatment. J. Photochem. Photobiol. B:Biol. 44. (51-158.
211. Cecic, I., C. S. Parkins and M. Korbelik (2001) Induction of systemic neutrophil response in mice by photodynamic therapy of solid tumors. Photochem. Photobiol. 74, 712-720.
212. Sun, J., I. Cecic, C. S. Parkins and M. Korbelik (2002) Neutrophils as in inflammatory and immune effectors in photodynamic therapy-treated mouse SCCVII tumours. Photochem. Photobiol. Sci. 1, 690-695.
213. Coutier, S., L. Bezdetnaya, S. Marchal, V. Melnikova, I. Belitchenko. J. L. Merlin and F. Guillemin ( 1999) Foscan® (mTHPC) photosensitized macrophage activation: Enhancement of phagocytosis, nitric oxide release and tumor necrosis factor-a-mediated cytolytic activity. Br. J. Cancer 81, 37-42.
214. van Duijnhoven, F. H., R. I. J. M. Aalbers. J. P. Rovers, O. T. Terpstra and P. J. K. Kuppen (2003) Immunological aspects of photodynamic therapy of liver tumors in a rat model for colorectal cancer. Photochem. Photobiol. 78, 235-240.
215. Berenbaum, M. C., R. Bonnett, E. B. Chevretton. S. L. AkandeAdebakin and M. Ruston (1993) Selectivity of meso-tetra(hydroxyphenyl)porphyrins and chlorins and of photofrin II in causing photodamage in tumour, skin, muscle and bladder. The concept of cost-benefit in analysing the results. Lasers Med. Sci. 8.
216. Vonarx-Coinsmann, V., M. T. Foultier, N. Cempel, L. Morlet, A. Combre and T. Patrice (1994) In vitro and in vivo photodynamic effects of a new photosensitizer: Tetra(m-hydroxyphenyl)chlorin. Lasers Med. Sci. 9, 173-181.
217. Koechli, O. R., G. N. Schaer, V. Schenk, U. Haller and H. Walt (1995) Assessment of effect of photosensitizers on cytotoxicity of photodynamic therapy in human breast cancer cell cultures. Arch. Gynecol. Obstet. 256, 167-176.
218. Coutier, S., S. Mitra, L. N. Bedzdetnaya, R. M. Parache, I. Georgakoudi, T. H. Foster and F. Guillemin (2001) Effects of fluence rate on cell survival and photobleaching in meta-tetra(hydroxyphenyl)chlorin-photosensitized Colo 26 multicell tumor spheroids. Photochem. Photobiol. 73, 297-303.
219. Morlet, L.,V. Vonarx-Coinsmann, P. Lenz, M.-T. Foultier, L. X. de Brito, C. Stewart and T. Patrice (1995) Correlation between meta(tetrahydroxyphenyl)chlorin (m-THPC) biodistribution and photodynamic effects in mice. J. Photochem. Photobiol. B:Biol. 28, 25-32.
220. Morlet, L., V. Vonarx-Coinsmann, M.-T. Foultier and T. Patrice (1995) Meso-tetrahydroxyphenylchlorin (mTHPC) fluorescence kinetics in mice. Proc. SPIE Int. Soc. Opt. Eng. 2371, 501-505.
221. Sasnouski, S., E. Pic, D. Dumas, V. Zorin, M.-A. D'Hallewin. F. Guillemin and L. Bezdetnaya (2007) Influence of incubation time and sensitizer localization on meta-tetra(hydroxyphenyl)chlorin (mTHPC)-induced photoinactivation of cells. Radiat. Res. 168, 209-217.
222. Rezzoug, H., M. Barberi-Heyob, J. L. Merlin, L. Bolotine, D. Lignon and F. Guillemin (1996) Comparaison in vitro de l'activité photodynamique de la meso-tétra (m-hydroxyphenyl) chlorine et de l'hématoporphyrine derivée. Bull. Cancer 83, 816822.
223. Hornung, R., B. Jentsch, N. E. Crompton, U. Haller and H. Walt (1997) In vitro effects and localisation of the photosensitizers mTHPC and m-THPC MD on carcinoma cells of the human breast (MCF-7) and Chinese hamster fibroblasts (V-79). Lasers Surg. Med. 20, 443-450.
224. Gharehbaghi, K., A. Kubin, M. Grusch, E. Gharehbaghi-Schnell, F. Wierrani, H. N. Jayaram, W. Grunberger and T. Szekeres (2000) Photodynamic action of meta-tetrahydroxyphenylchlorin (mTHPC) on an ovarian cancer cell line. Anticancer Res. 20, 2647-2652.
225. Yow, C. M. N., N. K. Mak, S. Szeta, J. Y. Chen, Y. L. Lee, N. H. Cheung, D. P. Huang and A. W. N. Leung (2000) Photocytotoxic and DNA damaging effect of Temoporfin (mTHPC) and merocyanine 540 (MC540) on nasopharyngeal cell. Toxicol. Lett. 115, 53-61.
226. Fischer, F., W. Maier-Borst and W.-J. Lorenz (1998) Photodynamic therapy as a tool for suppressing the haematogenous dissemination of tumour cells. J. Photochem. Photobiol. B:Biol. 43, 27-33.
227. Yow, C. M. N., N. K. Mak, A. W. N. Leung and Z. Huang (2009) induction of early apoptosis in human nasopharyngeal carcinoma cells by mTHPC-mediated photocytotoxicity. Photodiagn. Photodyn. Ther. 6, 122-127.
228. Ball, D. J., S. R. Wood, D. I. Vernon, J. Griffiths, T. M. A. R. Dubbelman and S. B. Brown (1998) The characterisation of three substituted zinc phthalocyanines of differing charge for use in photodynamic therapy. A comparative study of their aggregation and photosensitising ability in relation to mTHPC and polyhaematoporphyrin. J. Photochem. Photobiol. B:Biol. 45, 28-35.
229. Teiten, M.-H., L. Bezdetnaya, J.-L. Merlin, C. Bour-Dill, M. E. Pauly, M. Dicato and F. Guillemin (2001) Effect of metatetra(hydroxyphenyl)chlorin (mTHPC)-mediated photodynamic therapy on sensitive and multidrug-resistant human breast cancer cells. J. Photochem. Photobiol. B:Biol. 62, 146-152.
230. Teiten, M.-H., P. Even, P. Burgos, C. Frochot. S. Aubert, M.-C. Carré, L. Bolotine, J.-L. Merlin, F. Guillemin and M.-L. Viriot (2002) Specific fluorescent traces. Imaging and applications for photodynamic therapy. C. R. Biologies 325, 487-493.
231. Schlosser, V., O. R. Koechli, R. Cattaneo, B. Jenisch. U. Haller and H. Walt (1999) Photodynamic effects in vitro in fresh gynecologic tumors analyzed with a bioluminescence model. Clin. Chem. Lab. Med. 37, 115-120.
232. Kiesslich, T., J. Berlanda, K. Plaetzer, B. Krammer and F. Berr (2007) Comparative characterization of the efficiency and cellular pharmacokinetics of Foscan®- and Foslip®-based photodynamic treatment in human biliary tract cancer cell lines. Photochem. Photobiol. Sci. 6, 619-627.
233. Kiesslich, T., G. Wolkersdörfer, D. Neureiter, H. Salmhofer and F. Berr (2009) Photodynamic therapy for non-resectable perihilar cholangiocarcinoma. Photochem. Photobiol. Sci. 8, 23-30.
234. Dobler-Girdziunaite, D., W. Burkhard, U. Haller, B. Larsson and H. Wall (1995) Kombinierte Anwendung der photodynamischen Therapie mit ionisierenden Strahlen bein Mamakarzinomzellen in vitro. Strahlenther, Onkol. 171, 622-629.
235. Mayhew, S., D. I. Vernon, J. Schofield, J. Griffiths and S. B. Brown (2001) Investigation of cross-resistance to a range of photosensitizers, hyperthermia and UV light in two radiationinduced fibrosarcoma cell strains resistant to photodynamic therapy in vitro. Photochem. Photobiol. 73, 39-46.
236. Wright, K. E., E. Liniker, M. Loizidou, C. Moore, A. J. MacRobert and J. B. Phillips (2009) Peripheral neural cell sensitivity to mTHPC-mediated photodynamic therapy in a 3D in vitro model. Br. J. Cancer 101, 658-665.
237. Uzdensky, A. B., O. Y. Dergacheva, A. A. Zhavoronkova, A. V. Reshetnikov and G. V. Ponomarev (2004) Photodynamic effect of novel chlorin e0 derivatives on a single nerve cell. Life Sci. 74, 2185-2197.
238. Kiesslich, T., D. Neureiter, B. A linger, G. L. Jansky, J. Berlanda, V. Mkrtchyan, M. Ocker, K. Plaetzer and F. Berr (2010) Uptake and phototoxicity of meso-tetrahydroxyphenyl chlorine are highly variable in human biliary tract cancer cell lines and correlate with markers of differentiation and proliferation. Photoclient. Photobiol. Sci. 9, 734-743.
239. Ronn, A. M.,. L. A. M. D. Lofgren and A. Westerborn (1996) Interspecies pharmacokinetics as applied to the hard drug photosensitizing agent meta(tetrahydroxphenyl)chlorin. Proc. SPIE Int. Soc. Opt. Eng. 2625, 118-123.
240. Glanzmann, T., M. Forrer S. Andrejevic Blant, A. Woodtli, P. Grosjean, D. Braichotte, H. van den Bergh, P. Monnier and G. Wanieres (2000) Pharmacokinetics and pharmacodynamics of tetra(m-hydroxyphenyl)chlorin in the hamster cheek pouch tumor model: Comparison with clinical measurements. J. Photochem. Photobiol. B:Biol. 57, 22-32.
241. Ris. H.-B., L. Quang, T. Krueger, C. K. Lim, B. Reynolds, U. Althaus and H.-H. Altermatt (1998) Photosensitizing effects of m-tetrahydroxyphenylchlorin on human tumor xenografts: Correlation with sensitizer uptake, tumor doubling time and tumor histology. Int. J. Cancer 76, 872-874.
242. D'Hallewin, M.-A., S. Berrahmoune, L. Bezdetnaya, H.-P. Lassalle and F. Guillemin (2007) Orthotopic animal models for oncologic photodynamic therapy and photodiagnosis. Photodiagn. Photodyn. Ther. 4, 230-236.
243. Andrejevic-Blant, S., J.-F. Theumann, M. Forrer, G. Wagnieres, H. van den Bergh and P. Monnier (1997) Wavelength-dependent effect of tetra(m-hydroxyphenyl)chlorin for photodynamic therapy in an "early" squamous cell carcinoma model. Lasers Med. Sci. 12, 269-273.
244. Andrejevic-Blant, S., A. Woodtli, G. Wagnieres, C. Fontolliet, H. van den Bergh and P. Monnier (1998) Interstitial photodynamic therapy with tetra(m-hydroxyphenyl)chlorin: Tumor versus striated muscle damage. Int. J. Radiat. Oncol. Biol. Phys. 42, 403-412.
245. Andrejevic Blant, S., J.-P. Ballini, H. van den Bergh, C. Fontolliet, G. Wagnieres and P. Monnier (2000) Time-dependent biodistribution of tetra(m-hydroxyphenyl)chlorin and benzoporphyrin derivative monoacid ring A in the hamster model: Comparative fluorescence microscopy study. Photochem. Photobiol. 71, 333-340.
246. Andrejevic Blant, S., T. M. Glanzmann, J.-P. Ballini, G. Wagnieres, H. van den Bergh and P. Monnier (2002) Uptake and localization of mTHPC (Foscan®) and its 14 C-labeled form in normal and tumour tissue of the hamster sqaumous cell carcinoma model: A comparative study. Br. J. Cancer 87, 1470-1478.
247. Alexandratou, E., M. Kyriazi, D. Yova. S. Gräfe, T. Trebst, A. Johansson, J. Svensson, K. Svanberg, N. Bendsoe and S. Anderson-Engels (2006) Distribution studies of m-THPC after topical application of m-THPC thermogel in a murine non-melanoma side cancer tumor model by fluorescence spectroscopic and imaging techniques. Proc. SPIE Int. Soc. Opt. Eng. 6139, 61390G.
248. Johansson, A., J. Svensson, S. Andersson-Engels, N. Bendsoe, K. Svanberg, I. Bigio, E. Alexandratou, M. Kyriazi, D. Yova, S. Gräfe and T. Trebst (2006) mTHPC pharmacokinetics following topical administration. Proc. SPIE Int. Soc. Opt. Eng. 6094, 60940C.
249. Bossu, E., O. A'Amar, R. M. Parache, D. Notter, P. Labrude, C. Vigneron and F. Guillemin (1997) Determination of the maximal tumor/normal skin ratio after HpD or m-THPC administration in hairless mouse (SKh-I) by fluorescence spectroscopy-a non-invasive method. Anticancer Drugs 8, 67-72.
250. Bossu, E., J.-J. Padilla-Ybarra, D. Notter, C. Vigneron and F. Guillemin (2000) Determination of the maximal carcinoma/skin ratio after HpD or m-THPC administration in hairless mice (SKH-I) by fluorescence spectroscopy. Anticancer Drugs 11, 8591.
251. Reuther, T., A. C. Kübler, U. Zillmann, C. Flechtenmacher and H. Sinn (2001 ) Comparison of the in vivo efficiency of photofrin II-, mTHPC-, mTHPC-PEG- and mTHPCnPEG-medtated PDT in a human xenografted head and neck carcinoma. Lasers Surg. Med. 29, 314-322.
252. Kübler, A. C., T. Reuther, C. Staff, T. Haase, C. Flechtenmacher, A. Benner, M. Scheer and U. Zillmann (2001) Klinische Wirksamkeit von/mTHPC-PEG in einem neuen xenogenen Tumortiermodell für humane Plattenepithelkarzinome. Mund Klefer Gesichtschir, 5, 105-113.
253. Sharwani, A., W. Jerjes, C. Hopper, M. P. Lewis, M. El-Maaytah, H. S. M. Khalil, A. J. MacRobert, T. Upile and V. Salih (2006) Photodynamic therapy down-regulates the invasion promoting factors in human oral cancer. Arch. Oral Biol. 51, 11041111.
254. Ohlerth, S., D. Laluhová, J. Buchholz, M. Roos, H. Walt and B. Kaser-Hotz (2006) Changes in vascularity and blood volume as a result of photodynamic therapy can be assessed with power Doppler ultrasonography. Lasers Surg. Med. 38, 229-234.
255. van Geel, I. P. J., H. Oppelaar, Y. G. Oussoren, M. A. van der Valk and F. A. Stewart (1995) Photosensitizing efficacy of MTHPC-PDT compared to Photofrin-PDT in the Rifi mouse tumor and normal skin. Int. J. Cancer 60, 388-394.
256. Korbelik, M., J. Sun and J. J. Posakony (2001) Interaction between photodynamic therapy and BCG immunotherapy responsible for the reduced recurrence of treated mouse tumors. Photochem. Photobiol. 73, 403-409.
257. Ris. H.-B., A. Giger. V. I. Hof, D. Mettler, J. C. M. Stewart, U. Althaus and H. J. Altermatt (1997) Experimental assessment of photodynamic therapy with chlorins for malignant mesothelioma. Eur. J. Cardio. Surg. 12, 542-548.
258. Cramers, P., M. Ruevekamp, H. Oppelaar, O. Dalesio, P. Baas and F. A. Stewart (2003) Foscan® uptake and tissue distribution in relation to photodynamic therapy. Br. J. Cancer 88, 283-290.
259. Schouwink, H., M. Ruevekamp, H. Oppelaar, R. Van Veen, P. Baas and F. A. Stewart (2001) Photodynamic therapy for malignant mesothelioma: Preclinical studies for optimization of treatment protocols. Photochem. Photobiol. 73, 410-417.
260. Fielding, D. L. G. A. Buonaccorsi, A. J. MacRobert, A. M. Hanby, M. R. Hetzel and S. G. Bown (1999) Fine-needle interstitial photodynamic therapy of the lung parenchyma. Chest 115, 502-510.
261. Murrer, L. H. P., K. M. Hebeda, J. P. A. Marijnissen and W. M. Star (1999) Short- and long-term normal tissue damage with pholodynamic therapy in pig trachea: A fluence-response pilot study comparing Photofrin and mTHPC. Br. J. Cancer 80, 744-755.
262. Fielding, D. L. G. Buonaccorsi. G. Cowley, A. M. Johnston, G. Hughes, M. R. Hetzel and S. G. Bown (2001) Interstitial laser photocoagulation and interstitial photodynamic therapy of normal lung parenchyma in the pig. Lasers Med. Sci. 16, 26-33.
263. Krueger, T., Y. Pan, N. Tran, H.-J. Altermatt, I. Opitz and H.-B. Ris (2005) Intraoperative photodynamic therapy of the chest cavity in malignant pleural mesothelioma bearing rats. Lasers Surg. Med. 37, 271-277.
264. Opitz, I. T. Krueger, Y. Pan. H.-J. Altermatt, G. Wagnieres and H.-B. Ris (2006) Preclinical comparison of mTHPC and verteporfin for intracavitary photodynamic therapy of malignant pleural mesothelioma. Eur. Surg. Res. 38, 333-339.
265. Lofgren, L. A., A. M. Ronn, A. L. Abramson, M. J. Shikowitz, M. Nouri, C. J. Lee, J. Batti and B. M. Steinberg (1994) Photodynamic therapy using m-tetra(hydroxyphenyl) chlorin. Arch. Otolaryngol. Head Neck Surg. 120, 1355-1362.
266. Veenbuzen, R. B., M. C. Ruevekamp, H. Oppelaar, T. J. Helmerhorst, P. Kenemans and F. A. Stewart (1997) Foscan-mediated photodynamic therapy for a peritoneal-cancer model: Drug distribution and efficacy studies, int. J. Cancer 73, 230-235.
267. Alian. W., S. Andersson-Engels, K. Svanberg and S. Svanberg (1994) Laser-induced fluorescence studies of meso-tetra(hydroxyphenyl)chlorin in malignant and normal tissues in rats. Br. J. Cancer 70, 880-885.
268. Dabkeviciene, D., V. Stankevicius, G. Grazeliene, A. Markuckas, J. Didziapetriene and V. Kirveliene (2010) mTHPC-mediated photodynamic treatment of Lewis lung carcinoma in vitro and in vivo. Medicina (Kaunas) 46, 345-350.
269. Gahlen, J., S. Winkler, R. L. Prost, M. Rheinwald, T. Haase and C. Herfarth (2000) Adjuvante intraoperative Photodynamische Therapie (PDT) nach Photosensibilisierung mit mTHPC im CC531 Kolonkarzinom Model der Nacktmaus, Chirug. For. 29, 139-142.
270. Rovers, J. P., A. E. Saarnak, A. Molina, J. J. Sehultmaker, H. J. C. M. Sterenborg and O. T. Tepstra (1999) Effective treatment of liver metastases with photodynamic therapy, using the second-generation photosensitizer meta-tetra(hydroxyphenyl)chlorin (mTHPC), in a rat model. Br. J. Cancer 81, 600608.
271. Ansell, J. K., M. L. de Jode and M. F. Grahn (1997) Characterization of a murine model for the rapid assessment of acute photodynamic response in tumour and muscle. Lasers Med. Sci. 12, 336-341.
272. Mlkvy, P., H. Messmann, M. Pauer, J. C. M. Stewart, C. E. Millson, A. J. MacRobert and S. G. Bown (1996) Distribution and photodynamic effects of meso-tetrahydroxyphenylchlorin (mTHPC) in the pancreas and adjacent tissues in the Syrian golden hamster. Br. J. Cancer 73, 1473-1479.
273. Post, J. G., J. A. M. te Poele. J. J. Schultmaker and F. A. Stewart (1996) A comparison of functional bladder damage after intravesical photodynamic therapy with three different photosensitizes. Photochem. Photobiol. 63, 314-321.
274. Mikvy, P., H. Messman, A. J. MacRobert, M. Pauer, V. R. Sams, C. L. Davies, J. C. M. Stewart and S. G. Bown (1997) Photodynamic therapy of a transplanted pancreatic cancer model using meta-tetraphydroxyphenylchlorin (mTHPC). Br. J. Cancer 76, 713-718.
275. Radu, A., P. Grosjean, Y. Jaquet, R. Pilloud, G. Wagnieres, H. van den Bergh and P. Monnier (2005) Photodynamic therapy and endoscopic mucosal resection as minimally invasive approaches for the treatment of early esophageal tumors: Pre-clinical and clinical experience in Lausanne. Photodiagn. Photodyn. Ther. 2, 35-44.
276. Radu, A., R. Conde, C. Fontolliet, G. Wagnieres. H. Van den Bergh and P. Monnier (2003) Mucosal ablation with photodynamic therapy in the esophagus: Optimization of light dosimetry in the sheep model. Gasirointest. Endosc. 57, 897-905.
277. Glanzmann, T. M., M. P. E. Zellweger, F. Borle, R. Conde, A. Radu, J.-P. Ballini, Y. Jaquet, R. Pilloud, H. Van Den Bergh, P. Monnier, S. Andrejevic-Blant and G. A. Wagnières (2009) Assessment of a sheep animal model to optimize photodynamic therapy in the oesophagus. Lasers Surg. Med. 41, 643-652.
278. Perry, Y., M. W. Epperly, H. C. Fernando, E. Klein, S. Finkelstein, J. S. Greenberger and J. D. Luketich (2005) Photodynamic therapy induced esophageal stricture - an animal model: From mouse to pig. J. Surg. Res. 123, 67-74.
279. Hornung, R., D. Fink, D. Dobler-Girdzjunaite. T. Stallmach, U. Haller and H. Walt (1999) Photodynamic therapy for the hypercalcemic type of the small cell carcinoma of the ovary in a mouse xenograft model. Gynecol. Oncol. 75, 447-452.
280. Hornung, R., M. K. Fehr, J. Monti-Frayne, T. B. Krasieva, B. J. Tromberg, M. W. Berns and Y. Tadir (1999) Highly selective targeting of ovarian cancer with the photosensitizer PEG-m-THPC in a rat model. Photochem. Photobiol. 70, 624-629.
281. Obwegeser, A., R. Jakober and H. Kostron (1998) Uptake and kinetics of 14 C-labelled meta-tetrahydroxyphenylchlorin and 5-aminolaevulinic acid in the C6 rat glioma model. Br. J. Cancer 78, 733-738.
282. Mannino, S., A. Molinari, G. Sabatino, S. A. Ciafrè, M. Colone, G. Maira, C. Anile, G. Arancia and A. Mangiola (2008) Intratumoral vs systemic administration of meta-tetrahydroxyphenylchlorin for photodynamic therapy of malignant gliomas: Assessment of uptake and spatial distribution in C6 rat glioma model. Int. J. Immunopathol. Pharmacol. 21, 227-231.
283. Colombo-Benkmann, M., M. Muhm, J. Gahlen, C. Heym and N. Senninger (1997) Photosensitizer induced fluorescence of the rat adrenal gland and rat pheochromocytoma cells (PC 12) by mesotetra(hydroxyphenyl)chlorin (mTHPC). Proc. SPIE Int. Soc. Opt. Eng. 3197, 234-240.
284. Colombo-Benkmann, M., M. Muhm, J. Gahlen, M.-S. Vry, H. Deubzer, A. Holloschi, M. Hafner, C. Heym and N. Senninger (1998) Selective accumulation of meso-tetra(hydroxyphenyl)chlorin in steroidsynthesizing cells of the rat adrenal gland. Proc. SPIE Int. Soc. Opt. Eng. 3260, 136-140.
285. Chang, S-C., G. Buonaccorsi, A. MacRobert and S. G. Bown (1996) Interstitial and transurethral photodynamic therapy of the canine prostate using meso-tetra-(m-hydroxyphenyl) chlorin. Int. J. Cancer 67, 555-562.
286. Chang, S. C., I. F. Chern and Y. H. Hsu (1999) Biological responses of dog prostate and adjacent structures after mesotetra-(m-hydroxyphenyl) chlorin and aluminum disulfonated phthalocyanine based photodynamic therapy. Proc. Natl Sci. Counc. Repub. China B, Life Sci. 23, 158-166.
287. Pegaz, B., E. Debefve, J. P. Ballini, G. Wagnieres, S. Spaniol, V. Albrecht, D. V. Scheglmann, N. E. Nifantiev, H. van den Bergh and Y. N. Konan-Kouakou (2006) Photothrombic activity of m-THPC-loaded liposomal formulations: Pre-clinical assessment on chick chorioallantoic membrane model. Eur. J. Pharm. Sci. 28, 134-140.
288. Kübler, A. C., W, Stenzel, M. Rühling, B. Meul and J.-H. Fischer (2003) Experimental evaluation of possible side effects of intraoperative photodynamic therapy on rabbit blood vessels and nerves. Lasers Surg. Med. 33, 247-255.
289. Campbell, G. A., K. E. Bartels, C. Arnold, T. Healey, R. L. Cowell, M. D. Lucroy and A. M. Ronn (2002) Tissue levels, histologic changes and plasma pharmacokinetics of meta-tetra (hydroxyphenvl) chlorin (mTHPC) in the cat. Lasers Med. Sci. 17, 79-85.
290. Rhoades, S. J. IV, J. P. Wicksted, A. Y. Hamad, A. M. Ronn, G. A. Campbell, C. S. Arnold and K. E. Bartels (2000) Fluorescence spectroscopy of Foscan induced feline tissues. Proc. SPIE Int. Soc. Opt. Eng. 3907, 510-518.
291. Buchholz, J., B. Kaser-Hotz, T. Khan, C. R. Bley, K. Melzer, R. A. Schwendener, M. Roos and H. Walt (2005) Optimizing photodynamic therapy: In vivo pharmacokinetics of liposomal meta-(tetrahydroxyphenyl)chlorin in feline squamous cell carcinoma. Clin. Cancer Res. 11, 7538-7544.
292. Buchholz, J., M. Wergin, H. Walt, S. Gräfe, C. R. Bley and B. Kaser-Hotz (2007) Photodynamic therapy of feline cutaneous squamous cell carcinoma using a newly developed liposomal photosensitizes: Preliminary results concerning drug safety and efficacy. J. Vet. Intern. Med. 21, 770-775.
293. Khan, T., M. Unternährer, J. Buchholz, B. Kaser-Hotz, B. Selm. M. Rothmaier and H. Walt (2006) Performance of a contact textile-based light diffuser for photodynamic therapy. Photodiagn. Photodyn. Ther. 3, 51-60.
294. Brown, J. E., S. B. Brown and D. I. Vernon (1999) Photosensitising drugs - Their potential in oncology. Exp. Opin. Invest. Drugs 8, 1967-1979.
295. Fenton, C. and C. M. Perry (2006) Verteporfin - A review of its use in the management of subfoveal choroidal neovascularisation. Drugs Aging 23, 421-445.
296. Schmidt-Erfurth, U. and T. Hasan (2000) Mechanisms of action of photodynamic therapy with verteporfin for the treatment of age-related macular degeneration. Surv. Ophthalmol. 45, 195-214.
297. Brown, S. B., E. A. Brown and I. Walker (2004) The present and future role of photodynamic therapy in cancer treatment. Lancet Oncol. 5, 497-508.
298. Allison, R. R., G. H. Downie, R. Cuenca. X.-H. Hu, C. J. H. Childs and C. H. Sibata (2004) Photosensitizers in clinical PDT. Photodiagn. Photodyn. Ther. 1, 27-42.
299. O'Connor, A. E., W. M. Gallagher and A. T. Byrne (2009) Porphyrin and nonporphyrin photosensitizers in oncology: Preclinical and clinical advances in photodynamic therapy. Photochem. Photobiol. 85, 1053-1074.
300. Allison, R. R. and C. H. Sibata (2010) Oncologic photodynamic therapy photosensitizers: A clinical review. Photodiagn. Photodyn. Ther. 7, 61-75.
301. Allison, R. R., R. Cuenca, G. H. Downie, M. E. Randall, V. S. Bagnato and C. H. Sibata (2005) PD/PDT for gynecological disease: A clinical review. Photodiagn. Photodyn. Ther. 2, 51-63.
302. Dilkes, M. G., G. Alusi and B. J. Djaezeri (1999) The treatment of head and neck cancer with photodynamic therapy: Clinical experience. Rev. Contemp. Pharmacother. 10, 47-57.
303. Kübler, A. C. (2005) Photodynamic therapy. Med. Laser Appl. 20, 37-45.
304. Morton, C. A. (2001) Treating basal cell carcinoma: Has photodynamic therapy come of age? Br. J. Dermatol. 145, 1-2.
305. Gahlen, J., R. L. Prosst and J. Stern (2002) Photodynamische Therapie im Gastrointestinaltrakt. Möglichkeiten und Grenzen. Chirurg 73, 122-131.
306. Mitton, D. and R. Ackroyd (2004) Photodynamic therapy in oesophageal carcinoma: An overview. Photochem. Photobiol. Sci. 3, 839-850.
307. Wolfsen, H. C. (2005) Uses of photodynamic therapy in premalignant and malignant lesions of the gastrointestinal tract beyond the esophagus. J. Clin. Gastroenterol. 39, 653-664.
308. Wolfsen. H. C. (2005) Present status of photodynamic therapy for high-grade dysplasia in Barrett's esophagus. J. Clin. Gastroenterol. 39, 189-202.
309. Eljamel, M. S. (2004) Brain PDD and PDT unlocking the mystery of malignant gliomas. Photodiagn. Photodyn. Ther. 1, 303-310.
310. Martin, N. E. and S. M. Hahn (2004) Interstitial photodynamic therapy for prostate cancer: A developing modality. Photodiagn. Photodyn. Ther. 1, 123-136.
311. Ayaru, L., S. G. Bown and S. P. Pereira (2004) Photodynamic therapy for pancreatic carcinoma: Experimental and clinical studies. Photodiagn. Photodyn. Ther. 1, 145-155.
312. Allison, R. R,. C. Sibata, T. S. Mang, V. S. Bagnalo, G. H. Downie, X. H. Hu and R. Cuenca (2004) Photodynamic therapy for chest wall recurrence from breast cancer. Photodiagn. Photodyn. Ther. 1, 157-171.
313. Pinthus, J. H., A. Bogaards, R. Weersink, B. C. Wilson and J. Trachtenberg (2006) Photodynamic therapy for urological malignancies: Past to current approaches. J. Urol. 175, 1201-1207.
314. Ahmed, H. U., C. Moore and M. Emberton (2009) Minimally-invasive technologies in uro-oncology: The role of cryotherapy. HIFU and photodynamic therapy in whole gland and focal therapy o flocalised prostate cancer. Surg. Oncol. 18, 219-232.
315. Eggener, S. E., P. T. Scardino, P. R. Carroll, M. J. Zelefsky, O. Sartor, H. Hricak, T. M. Wheeler, S. W. Fine, J. Trachtenberg, M. A. Rubin, M. Ohori, K. Kuroiwa, M. Rossignol and L. Abenhaim (2007) Focal therapy for localized prostate cancer: A critical appraisal of rationale and modalities. J. Urol. 178, 2260-2267.
316. Hillemanns, P., P. Soergel and M. Löning. (2009) Fluorescence diagnosis and photodynamic therapy for lower genital tract diseases - A review. Med. Laser Appl. 24, 10-17.
317. Fayter, D., M. Corbett, M. Heirs, D. Fox and A. Eastwood (2010) A systematic review of photodynamic therapy in the treatment of precancerous skin conditions. Barrett's oesophagus and cancers of the biliary tract, brain, head and neck, lung, oesophagus and skin. Health Technol. Assessm. 14, 1-129.
318. Radu, A., M. Zellweger, P. Grosjean and P. Monier (1999) Pulse oximeter as a cause of skin burn during photodynamic therapy. Endoscopy 31, 831-833.
319. Schwarz, V. A., S. D. Klein, R. Hornung, R. Knochenmuss, P. Wyss, D. Fink, U. Hallen and H. Walt (2001) Skin protection for photosensitized patients. Lasers Surg. Med. 29, 252-259.
320. Epstein, J. B., S. Emerton, D. A. Kolbinson, N. D. Le, N. Phillips, P. Stevenson-Moore and D. Osoba (1999) Quality of life and oral function in patients treated with radiation therapy for head and neck cancer. Head Neck 21, 1-11.
321. Poate, T. W., M. G. Dilkes and G. S. Kenyon (1996) Use of photodynamic therapy for the treatment of squamous cell carcinoma of the soft palate. Br. J. Oral Max. Surg. 34, 66-68.
322. Van Dongen, G. A. M. S. and G. B. Snow (1997) Prospects for future studies in head and neck cancer. Eur. J. Surg. Oncol. 23, 486-491.
323. Goepfert, H. and J. N. Myers (1997) Multidisciplinary head and neck cancer care. Curr. Opin. Otolaryngol. Head Neck Surg. 5, 93-98.
324. Nyst, H. J., I. B. Tan, F. A. Stewart and A. J. M. Balm (2009) Is photodynamic therapy a good alternative to surgery and radiotherapy in the treatment, of head and neck cancer? Photodiagn. Pholodyn. Ther. 6, 3-11.
325. Bredell, M. G., E. Besic, C. Maake and H. Walt (2010) The application and challenges of clinical PD-PDT in the head and neck region: A short review. J. Photochem. Photobiol. B: Biol. 101, 185-190.
326. Allison, R. R., R. E. Cuenca, G. H. Downie, P. Camnitz, B. Brodish and C. H. Sibata (2005) Clinical photodynamic therapy of head and neck cancers - A review of applications and outcomes. Photodiagn. Photodyn. Ther. 2, 205-222.
327. Biel, M. A. (1998) Phoiodynamic therapy using Photofrin and Foscan and the treatment of malignancies of the head and neck. Proc. SPIE Int. Soc. Opt. Eng. 3247, 25-30.
328. Kostron, H., A. Zimmermann and A. Obwegeser (1998) mTHPC-mediated-photodynamic detection for fluorescence guided resection of brain tumors. Prot: SPIE Int. Soc. Opt. Eng. 3262. 259-264.
329. Tan, I. B., H. Oppelaar, M. C. Ruevekamp, R. B. Veenhuizen, A. Timmers and F. A. Stewart (1999) The importance of in situ light dosimetry for photodynamic therapy of oral cavity tumors. Head Neck 21, 434-441.
330. Dilkes, M. G., M. L. DeJode, Q. Gardiner, G. S. Kenyon and P. McKelvie (1995) Treatment of head and neck cancer with photodynamic therapy - Results after one year. J. Laryngol. Otol. 109, 1072-1076.
331. Dilkes, M. G., M. L. DeJode, A. Rowntree-Taylor, J. A. McGilligan, G. S. Kenyon and P. McKelvie (1996) m-THPC photodynamic therapy for head and neck cancer. Lasers Med. Sci. 11, 23-29.
332. Braichotte, D., J.-F. Savary, T. Glanzmann, P. Westermann. S. Folli, G. Wagnieres, P. Monnier and H. Van den Bergh (1995) Clinical pharmacokinetic studies of tetra(meta-hydroxyphenyl)chlorin in squanous-cell carcinoma by fluorescence spectroscopy at 2 wavelengths. Int. J. Cancer 63, 198-204.
333. Copper, M. P., I. B. Tan, H. Oppelaar, M. C. Ruevekamp and F. A. Stewart (2003) Meta-tetra(hydroxyphenyl)chlorin photodynamic therapy in early-stage squamous cell carcinoma of the head and neck. Arch. Otolaryngol. Head Neck Surg. 129, 709-711.
334. Hopper, C., A. Kübler, H. Lewis, I. B. Tan and G. Putnam (2004) mTHPC-mediated phoiodynamic therapy for early oral squamous cell carcinoma. Int. J. Cancer 111, 138-146. 335.
335. Kübler, A. C., T. Haase, C. Staff, B. Kahle, M. Rheinwald and J. Mühling (1999) Photodynamic therapy of primary nonmelanomatous skin tumours of the head and neck. Lasers Surg. Med. 25, 60-68.
336. Fan, K. F. M., C. Hopper, P. M. Speight, G. A. Buonaccorsi and S. G. Bown (1997) Photodynamic therapy using mTHPC for malignant disease in the oral cavity. Int. J. Cancer 73, 25-32.
337. Kübler, A. C., J. de Carpentier, C. Hopper, A. G. Leonard and G. Putnam (2001) Treatment of squamous cell carcinoma of the lip using Foscan-mediated photodynamic therapy. Int. J. Oral Maxillofac. Surg. 30, 504-509.
338. Zimmermann, A., M. Ritsch-Marte and H. Kostron (2001) mTHPC-mediated photodynamic diagnosis of malignant brain tumors. Photochem. Photobiol. 74, 611-616.
339. El Far, M., A. Setate and M. El-Maadawy (1995) Photodynamic therapy with aminolevulinic acid and meso-telrahydroxyphenylchlorin: First initial clinical experience in Egypt. Proc. SPIE Int. Soc. Opt. Eng. 2371, 236-242.
340. El-Far, M., A. Setate and M. El-Maadawy (1998) First initial clinical application of phoiodynamic therapy (PDT) in Egypt: Two case reports. Lasers Life Sci. 8, 27-35.
341. D'Cruz, A. K., M. H. Robinson and M. A. Biel (2004) mTHPC-mediated photodynamiec therapy in patients with advanced, incurable head and neck cancer: A multicenier study of 128 patients. Head Neck 26, 232-240.
342. Lorenz. K. J. and H. Maier (2008) Plattenepithelkarzinome im Kopf-Hals-Bereich: Photodynamische Therapie mit Fosean®. HNO 56, 402 409.
343. Lorenz, K. J. and H. Maier (2009) Photodynamic therapy with meta-tetrahydroxyphenylchlorin (Foscan ®) in the management of squamous cell carcinoma of the head and neck: Experience with 35 patients. Eur. Arch. Otorhinolaryngol. 266, 1937-1944.
344. Dilkes, M. G., E. Benjamin, S. Ovaisi and A. S. Banerjee (2003) Treatment of primary mucosal head and neck squamous cell carcinoma using photodynamic therapy: Results after 25 treated cases. J. Laryngol. Otol. 117, 713-717.
345. Betz, C. S., W. Rauschning, E. P. Stranadko, M. V. Riaboc. V. Albrecht, N. E. Nifantiev and C. Hopper (2008) Optimization of treatment parameters for Foscan®-PDT of basal cell carcinomas. Lasers Surg. Med. 40, 300-311.
346. Naim, R. (2008) Photodynamische Therapie mit m-THPC (Fosean®): Behandlung von Plattenepithelkarzinomen im Kopf-Hals-Bereich. HNO 56. 490-492.
347. Betz, C. S., H. R. Jäger. J. A. S. Brookes, P. Richards, A. Leunig and C. Hopper (2007) Interstitial photodynamic therapy for a symptom-targeted treatment of complex vascular malformations in the head and neck region. Lasers Surg. Med. 39, 571-582.
348. van Veen, R. L. P., H. Nyst, S. Rai Indrasari, M. Adham Yudharto, D. J. Robinson, I. B. Tan, C. Meewis. R. Peters, S. Spaniol, F. A. Stewart, P. C. Levendag and H. J. C. M. Sterenborg (2006) In vivo fluence rale measurements during Foscan®-medialed photodynamic lherapy of persistent and recurrent nasopharyngeal carcinomas using a dedicated light applicator. J. Biomed. Opt. 11, 041107.
349. Nyst, H. J., R. L. P. Van Veen, I. B. Tan, R. Peters, S. Spaniol, D. J. Robinson, F. A. Stewart, P. C. Levendag and H. J. C. M. Sterenborg (2007) Performance of a dedicated light delivery and dosimetry device for photodynamic therapy of nasopharyngeal carcinoma: Phantom and volunteer experiments. Lasers Surg. Med. 39, 647-653.
350. Karakullukcu, B., K. van Oudenaarde, M. P. Copper, W. M. C. Klop, R. van Veen, M. Wildeman and I. B. Tan (2011) Photodynamic therapy of early stage oral cavity and oropharynx neoplasms: An outcome analysis of 170 patients. Eur. Arch. Otorhinolaryngol. 268, 281-288.
351. Tan, I. B., G. Dolivet, P. Ceruse, V. V. Poorten, G. Roest and W. Rauschning (2010) Temoporfin-mediated photodynamic therapy in patients with advanced, incurable head and neck cancer: A multicenter study. Head Neck 32, 1597-1604.
352. Biel, M. (2006) Advances in photodynamic therapy for the treatment of head and neck cancers. Lasers Surg. Med. 38, 349-355.
353. Lou, P. J., H. R. Jaeger. L. Jones, T. Theodossy, S. G. Bown and C Hopper (2004) Interstitial photodynamic therapy as salvage treatment for recurrent head and neck cancer. Br. J. Cancer 91, 441-446.
354. Vogl, T. J., K. Eichler, M. G. Mack. S. Zangos, C. Herzog. A. Thalhammer and K. Engelmann (2004) Interstitial photodynamic laser therapy in interventional oncology. Eur. Radiol. 14, 1063-1073.
355. Jerjes, W., T. Upile, Z. Hamdoon, F. Nhembe, R. Bhandari, S. Mackay, P. Shah, C. A. Mosse, J. A. S. Morley and C. Hopper (2009) Ultrasound-guided photodynamic therapy for deep seated pathologies: Prospective study. Lasers Surg. Med. 41, 612-621.
356. Robinson, D. J., M. B. Karakullukçu, B. Kruijt, S. C. Kanick, R. P. L. Van Veen, A. Amelink, J. J. C. M. Sterenbourg, M. J. H. Witjes and T. I. Bing (2010) Optical spectroscopy to guide photodynamic therapy of head and neck tumors. IEEE J. Sel. Top. Quant. Electr. 16, 854-862.
357. Jerjes, W., T. Upile. S. Akram and C. Hopper (2010) The surgical palliation of advanced head and neck cancer using photodynamic therapy. Clin. Oncol. 22, 785-791.
358. Hamdoon, Z., W. Jerjes, T. Upile, S. Akram and C. Hopper (2010) Cystic hygroma treated with ultrasound guided interstitial photodynamic therapy: Case study. Photodiagn. Photodyn. Ther. 7, 179-382.
359. Hamdoon, Z., W. Jerjes, T. Upile, P. Hoonjan and C. Hopper (2010) Endoluminal carotid stenting prior to photodynamic therapy to pericarotid malignant disease: Technical advance. Photodiagn. Photodyn. Ther. 7, 126-128.
360. Nhembe, F., W. Jerjes, T. Upile, Z. Hamdoon and C. Hopper (2009) Chondrosarcoma of the hyoid treated with interstitial photodynamic therapy: Case study. Photodiagn. Photodyn. Ther. 6, 235-237.
361. Hopper, C., C. Niziol and M. Sidhu (2004) The cost-effectiveness of Fosean mediated photodynamic therapy (Foscan-PDT) compared with extensive palliative surgery and palliative chemotherapy for patients with advanced head and neck cancer in the UK, Oral Oncol. 40, 372-382.
362. Kubier, A., C. Niziol, M. Sidhu, A. Dünne and J. A. Werner (2005) Eine kosten-effektivitäts-analyse der photodynamischen therapie mit Foscan® (Foscan®-PDT) im vergleich zu einer palliativen chemotherapie bei patienten mit fortgeschrittenen kopf-halstumoren in Deutschland. Laryn. Rhin. Otol. 84, 725-732.
363. Allison, R. R., C. H. Sibata, G. H. Downie and R. E. Cuenca (2006) A clinical review of PDT for cutaneous malignancies. Photodiagn. Photodyn. Ther. 3, 214-226.
364. Gupta, G., C. A. Morton, C. Whitehurst, J. V. Moore and R. M. MacKie (1999) Photodynamic therapy with mesotetra(hydroxyphenyl)chlorin in the topical treatment of Bowen's disease and basal cell carcinoma. Br. J. Dermatol. 141, 385-386.
365. Baas, P., A. E. Saarnak, H. Oppelaar, H. Neering and F. A. Stewart (2001) Photodynamic therapy with meta-tetrahydroxy-phenylchlorin for basal cell carcinoma: A phase I/II study. Br. J. Dermatol. 145, 75-78.
366. Triesscheijn, M., M. Ruevekamp, N. Antonini, H. Neering. F. A. Stewart and P. Baas (2006) Optimizing meso-tetra-hydroxyphenyl-chlorin-mediated photodynamic therapy for basal cell carcinoma. Photochem. Photobiol. 82, 1686-1690.
367. Hamdoon, Z., W. Jerjes, T. Upile and C. Hopper (2011) Optical coherence tomography-guided photodynamic therapy for skin cancer: Case study. Photodiagn. Photodyn. Ther. 8, 49-52.
368. Sidoroff, A. and P. Thaler (2010) Taking treatment decisions in non-melanoma skin cancer - The place for topical photodynamic therapy (PDT). Photodiagn. Photodyn. Ther. 7, 24-32.
369. Gray, J. and G. Fullarton (2007) The current role of photodynamic therapy in oesophageal dysplasia and cancer. Photodiagn. Photodyn. Ther. 4, 151-159.
370. Barr, H. (1998) Gastrointestinal tumours: Let there be light. Lancet 352, 1242-1244.
371. Radu, A., G. Wagnieres, H. van den Bergh and P. Monnier (2000) Photodynamic therapy of early squamous cell cancers of the esophagus. Gasirointest. Endosc. Clin. N. Am. 10, 439-460.
372. Gossner, L. and C. Ell (2000) Photodynamic therapy of gastric cancer. Gastrointest. Endosc. Clin. N. Am. 10, 461-480.
373. Grosjean, P., J.-F. Savary, G. Wagnières, J. Mizeret, A. Woodtli, J.-F. Theumann, C. Fontolliet, H. Bergh and P. Monnier (1996) Tetra(m-hydroxyphenyl)chlorin clinical photodynamic therapy of early bronchial and oesophageal cancers. Lasers Med. Sci. 11, 227-235.
374. Radu, A., P. Grosjean, C. Fontolliet, G. Wagnieres, A. Woodtli, H. Van den Bergh and P. Monnier (1999) Photodynamic therapy for 101 early cancers of the upper aerodigestive tract, the esophagus, and the bronchi: A single-institution experience. Diagn. Ther. Endoscop. 5, 145-154.
375. Savary, J. F., P. Monnier, C. Fontolliet, J. Mizeret, G. Wagnieres, D. Braichotte and H. van den Bergh (1997) Photodynamic therapy for early squamous cell carcinomas of the esophagus, bronchi, and mouth with m-tetra(hydroxyphenyl) chlorin. Arch. Otolaryngol. Head Neck Surg. 123, 162-168.
376. Savary, J.-F., P. Grosjean, P. Monnier, C. Fontolliet, G. Wagnieres, D. Braichotte and H. van den Bergh (1998) Photodynamic therapy of early squamous cell carcinomas of the esophagus: A review of 31 cases. Endoscopy 30, 258-265.
377. Braichotte, D. R., J. F. Savary, P. Monnier and H. van den Bergh (1996) Optimizing light dosimetry in photodynamic therapy of early stage carcinomas of the esophagus using fluorescence spectroscopy. Lasers Surg. Med. 19, 340-346.
378. Braichotte, D., J. F. Savary, T. Glanzmann, P. Monnier, G. Wagnières and H. van den Bergh (1996) Optimizing light dosimetry in photodynamic therapy of the bronchi by fluorescence spectroscopy. Lasers Med. Sci. 11, 247-254.
379. Zellweger, M., P. Grosjean, P. Monnier, H. van den Bergh and G. Wagnieres (1999) Stability of the fluorescence measurement of Fosean® in the normal human oral cavity as an indicator of its content in early cancers of the esophagus and the bronchi. Photochem. Photobiol. 69, 605-610.
380. Bays, R., G. Wagnieres, D. Robert, D. Braichotte, J.-F. Savary, P. Monnier and H. van den Bergh (1997) Light dosimetry for photodynamic therapy in the esophagus. Lasers Surg. Med. 20, 290-303.
381. Gossner, L., A. May, R. Sroka and C. Ell (1999) A new long-range through-the-scope balloon applicator for photodynamic therapy in the esophagus and cardia. Endoscopy 31, 370-376.
382. Grosjean, P., J.-F. Savary, J. Mizeret, G. Wagnieres, A. Woodtli, J.-F. Theumann, C. Fontolliet, H. van den Bergh and P. Monnier (1996) Photodynamic therapy for cancer of the upper aerodigestive tract using tetra(m-hydroxyphenyl)chlorin. J. Clin. Lasers Med. Surg. 14, 281-287.
383. Blant, S., P. Grosjean, J. P. Ballini, G. Wagnieres, H. van den Bergh, C. Fontolliet and P. Monnier (2001) Localization of tetra(m-hydroxyphenyl)chlorin (Fosean) in human healthy tissues and squamous cell carcinomas of the upper aero-digestive tract, the esophagus and the bronchi: A fluorescence microscopy study. J. Photochem. Photobiol., B: Biol. 61, 1-9.
384. Javaid, B., P. Watt and N. Krasner (2002) Photodynamic therapy (PDT) for oesophageal dysplasia and early carcinoma with mTHPC (m-tetrahydroxyphenyl chlorin): A preliminary study. Lasers Med. Sci. 17, 51-56.
385. Mitton, D., P. Claydon and R. Ackroyd (2004) Photodynamic therapy and photodiagnosis for Barrett's oesophagus and early oesophageal carcinoma. Photodiagn. Photodyn. Ther. 1, 319-334.
386. Etienne, J., N. Dorme, G. Bourg-Heckly, P. Raimbert and J. F. Flijou Jean (2004) Photodynamic therapy with green light and m-tetrahydroxyphenyl chlorin for intramucosal adenocarcinoma and high-grade dysplasia in Barrett's esophagus. Gastrointest. Endosc. 59, 880-889.
387. Lovat, L. B., N. F. Jamieson, M. R. Novelli, C. A. Mosse, C. Selvasekar, G. D. Mackenzie, S. M. Thorpe and S. G. Bown (2005) Photodynamic therapy with m-tetrahydrox y phenyl chlorin for high-grade dysplasia and early cancer in Barrett's columnar lined esophagus. Gastrointest. Endosc. 62, 617-623.
388. Barr, H. (2004) Photodynamic therapy for dysplastic Barrett's oesophagus and early cancer. Photodiagn. Photodyn. Ther. 1, 195-201.
389. Gross, S. A. and H. C. Wolfsen (2010) The role of photodynamic therapy in the esophagus. Gastrotntest. Endosc. Clin. North Am. 20, 35-53.
390. Ris, H.-B., H. J. Altermatt, R. Inderbitzi, R. Hess, B. Nachbur, J. C. Stewart, Q. Wang, C. K. Lim, R. Bonnett and M. C. Berenbaum (1991) Photodynamic therapy with chlorins of diffuse malignant mesothelioma: Initial clinical results. Br. J. Cancer 64, 1116-1120.
391. Friedberg, J. S. (2009) Photodynamic therapy as an innovative treatment for malignant pleural mesothelioma. Semin. Thorac. Cardiovasc. Surg. 21, 177-187.
392. Baldini, E. H., A. Recht, G. M. Strauss, M. M. DeCamp Jr, S. J. Swanson, M. J. Liptay, S. J. Mentzer and D. J. Sugarbaker (1997) Patterns of failure after trimodality therapy for malignant pleural mesothelioma. Ann. Thorac. Surg. 63, 334-338.
393. Lindenmann, J., V. Matzi, N. Neuböck, A. Maier and F.-M. Smolle-Jüttner (2010) The clinical impact of photodynamic therapy in thoracic surgery. Eur. Surg. 42, 220-228.
394. Yarmus, L., A. Ernst and D. Feller-Kopman (2010) Emerging technologies for the thorax: Indications, management and complications: Invited review series: Complications in lung procedures. Respirology 15, 208-219.
395. Vergnon, J.-M., R. M. Huber and K. Moghissi (2006) Place of cryotherapy, brachytherapy and photodynamic therapy in therapeutic bronchoscopy of lung cancers. Eur. Resp. J. 28, 200-218.
396. Schouwink, H., H. Oppelaar, M. Ruevekamp, M. van der Valk, G. hart, P. Rijken, P. Baas and F. A. Stewart (2003) Oxygen depletion during and after mTHPC-mediated photodynamic therapy in RIFI and H-MESO1 tumors. Radiât. Res. 159, 190-198.
397. Ris, H.-B., H. J. Altermatt, B. Nachbur, J. C. M. Stewart, Q. Wang, C. K. Lim, R. Bonnett and U. Althaus (1996) Intraoperative photodynamic therapy with m-tetrahydroxyphenylchlorin for chest malignancies. Lasers Surg. Med. 18, 39-45.
398. Ris, H.-B. (2005) Photodynamic therapy as an adjunct to surgery for malignant pleural mesothelioma. Lung Cancer 49, S65-S68.
399. Baas, P., L. Murrer, F. A. Zoetmulder, F. A. Stewart, H. B. Ris, N. van Zandwijk, J. L. Peterse and E. J. Rutgers (1997) Photodynamic therapy as adjuvant therapy in surgically treated pleural malignancies. Br. J. Cancer 76, 819-826.
400. Friedberg, J. S., R. Mick, J. Stevenson, J. Metz, T. Zhu, J. Buyske, D. H. Sterman, H. I. Pass, E. Glatstein and S. M. Hahn (2003) A phase I study of Foscan-mediated photodynamic therapy and surgery in patients with mesothelioma. Ann. Thorac. Surg. 75, 952-959.
401. Schouwink, H., E. T. Rutgers, J. van der Sijp. H. Oppelaar, N. van Zandwijk, R. van Veen, S. Burgers, F. A. Stewart, F. Zoetmulder and P. Baas (2001) Intraoperative photodynamic therapy after pleuropneumonectomy in patients with malignant pleural mesothelioma - Dose finding and toxicity results. Chest 120, 1167-1174.
402. Yom, S. S., T. M. Busch, J. S. Friedberg, E. P. Wileyto, D. Smith, E. Glatstein and S. M. Hahn (2003) Elevated serum cytokine levels in mesothelioma patients who have undergone pleurectomy or extrapleural pneumonectomy and adjuvant intraoperative photodynamic therapy. Photochem. Photobiol. 78, 75-81.
403. Schouwink, H. and P. Baas (2004) Foscan-mediated photodynamic therapy and operation for malignant pleural mesothelioma. Ann. Thorac. Surg. 78, 388.
404. Friedberg, J. S. and S. M. Hahn (2004) A phase I study of Foscan-mediated photodynamic therapy and operation for malignant pleural mesothelioma. Ann. Thorac. Surg. 78, 952-959.
405. Moghissi, K. and K. Dixon (2005) Photodynamic Therapy in the management of malignant pleural mesothelioma: A review. Photodiagn. Photodyn. Ther. 2, 135-147.
406. Allison, R. R., C. Sibata, G. H. Downie and R. E. Cuenca (2006) Photodynamic therapy of the intact breast. Photodiagn. Photodyn. Ther. 3, 139-146.
407. Wyss, P., V. Schwarz, G. Dobler-Girdziunaite, R. Hornung, H. Walt, A. Degen and M. K. Fehr (2001) Photodynamic therapy of locoregional breast cancer recurrences using a chlorin-type photosensitizer. Int. J. Cancer 93, 720-724.
408. Gannon, M. J. and S. B. Brown (1999) Photodynamic therapy and its applications in gynaecology. Br. J. Obstetr. Gynaecol. 106, 1246-1254.
409. Wierrani, F., D. Fiedler, W. Grin, M. Henry, E. Dienes, K. Gharehbaghi, B. Krammer and W. Grunberger (1997) Clinical effect of meso-tetrahydroxyphenylchlorine based photodynamic therapy in recurrent carcinoma of the ovary: Preliminary results. Br. J. Obstet. Gynaec. 104, 376-378.
410. Wierrani, F., D. Fiedler, W. Grin, M. Henry, B. Krammer and W. Grünberger (1997) Intraoperative meso-tetrahydroxyphenylchlorin-based photodynamic therapy in metastatic gynecologic cancer tissue: Initial results. J. Gynecol. Surg. 13, 23-29.
411. Wierrani, F. (1999) Experimentelle Untersuchung und klinische Verwendung von photodynamischer Therapie (PDT) im Rudolfstiftung Hospital. Gynäkol. Geburts. Rundsch. 39, 217-225.
412. Krimbacher, E., A. G. Zeimet, C. Marth and H. Kostron (1999) Photodynamic therapy for recurrent gynecologic malignancy: A report on 4 cases. Arch. Gynecol. Obstet. 262, 193-197.
413. Campbell, S. M., D. J. Gould, L. Salter, T. Clifford and A. Curnow (2004) Photodynamic therapy using meta-tetrahydroxyphenylchlorin (Foscan®) for the treatment of vulval intraepithelial neoplasia. Br. J. Dermatol. 151, 1076-1080.
414. Campbell, S. M. and A. Curnow (2008) Extensive vulval intraepithelial neoplasia treated with a new regime of systemic photodynamic therapy using meta-tetrahydroxychlorin (Fosean®). J. Eur. Acad. Dermatol. Venerol. 22, 502-503.
415. Soergel, P. and P. Hillemanns (2010) Photodynamic therapy for intraepithelial neoplasia of the lower genital tract. Photodiagn. Photodyn. Ther. 7, 10-14.
416. Eljamel, M. S. (2008) Brain photodiagnosis (PD), fluorescence guided resection (FGR) and photodynamic therapy (PDT): Past, present and future. Photodiagn. Photodyn. Ther. 5, 29-35.
417. Eljamel, S, (2010) Photodynamic applications in brain tumors: A comprehensive review of the literature. Photodiagn. Photodyn. Ther. 7, 76-85.
418. Kostron, H., A. Obwegeser, R. Jakober, A. Zimmermann and A. Rueck (1998) Experimental and clinical results of mTHPC (Foscan®)-mediated photodynamic therapy for malignant brain tumors. Proc: SPIE Int. Soc. Opt. Eng. 3247, 40-45.
419. Kostron, H., T. Fiegele and E. Akatuna (2006) Combination of FOSCAN® mediated fluorescence guided resection and photodynamic treatment as new therapeutic concept for malignant brain tumors. Med. Laser Appl. 21, 285-290.
420. Ell, C., L. Gossner, A. May, H. T. Schneider, E. G. Hahn, M. Stolte and R. Sroka (1998) Photodynamic ablation of early cancers of the stomach by means of mTHPC and laser irradiation: Preliminary clinical experience. Gut 43, 345-349.
421. Gossner, L., A. May, H. T. Schneider, E. G. Hahn, M. Stolte, R. Sroka and C. Ell (1998) Photodynamische Therapie von frühem Magenkrebs mit mTHPC und Laserbestrahlung. Leber Magen Darm 28, 209.
422. Mlkvy, P., H. Messmann, J. C. Stewart, M. Pauer, C. E. Millson, A. J. McRobert and S. G. Bown (1995) Distribution and photodynamic effect of meta-tetrahydroxyphenylchlorin (mTHPC) in the pancreas and adjacent tissues in Syrian golden hamsters. Proc. SPIE Int. Soc. Opt. Eng. 2371, 268-273.
423. Bown, S. G., A. Z. Rogowska, D. E. Whitelaw, W. R. Lees, L. B. Lovat, P. Ripley, L. Jones, P. Wyld, A. Gillams and A. W. R. Hatfield (2002) Photodynamic therapy for cancer of the pancreas. Gut 50, 549-557.
424. Nathan, T. R., D. E. Whitelaw, S. C. Chang, W. R. Lees, P. M. Ripley, H. Payne, L. Jones, M. C. Parkinson, M. Emberton, A. R. Gillams, A. R. Mundy and S. G. Bown (2002) Photodynamic therapy for prostate cancer recurrence after radiotherapy: A phase I study. J. Urol. 168, 1427-1432.
425. Ayaru, L., J. Wittmann, A. J. MacRobert, M. Novelli, S. G. Bown and S. P. Pereira (2007) Photodynamic therapy using verteporfin photosensitization in the pancreas and surrounding tissues in the Syrian golden hamster. Pancreatol. 7, 20-27.
426. Waidelich, R. (2010) Laser-induced lithotripsy and photodynamic therapy in urology - A short introduction to current laser applications. Med. Laser Appl. 25, 14-19.
427. Moore, C. M., T. R. Nathan, W. R. Lees, C. A. Mosse, A. Freeman, M. Emberton and S. G. Bown (2006) Photodynamic therapy using meso tetra hydroxy phenyl chlorin (mTHPC) in early prostate cancer. Lasers Surg. Med. 38, 356-363.
428. Zhu, T. C. and J. C. Finlay (2006) Prostate PDT dosimetry. Photodiagn. Photodyn. Ther. 3, 234-246.
429. Johansson, A., J. Axelsson, S. Andersson-Engels and J. Swartling (2007) Realtime light dosimetry software tools for interstitial photodynamic therapy of the human prostate. Med. Phys. 34, 4309-4321.
430. Axelsson, J., J. Swartling and S. Andersson-Engels (2009) In vivo photosensitizer tomography inside the human prostate. Opt. Lett. 34, 232-234.
431. Wiedmann, M., J. Hauss, H. Witzigmann and J. MÖssner (2006) Stellenwert spezieller palliativer Therapieverfahren beim extrahepatischen Gallengangskarzinom: Gallengangsstents, photodynamische Therapie, operative Umgehungsanastomosen. Onkologe 12, 1237-1248.
432. Kiesslich, T., D. Neureiter, G. W. Wolkerdörfer, K. Plaetzer and F. Berr (2010) Advances in photodynamic therapy for the treatment of hilar biliary tract cancer. Future Oncol. 6, 1925-1936.
433. Pereira, S. P., L. Ayaru, A. Rogowska, A. Mosse, A. R. W. Hatfield and S. G. Bown (2007) Photodynamic therapy of malignant biliary strictures using meso-tetrahydroxyphenylchlorin. Eur. J. Gastroenterol. Hepatol. 19, 479-485.
434. Zöpf, T. and J. F. Riemann (2000) Therapie von Pankreas- und Gallenwegstumoren: Stellenwert der Strahlentherpie und photodynamischen Therapie. Schw. Rd. Med. 89, 1293-1298.
435. Wolkersdörfer, G. W., T. Kiesslich, D. Neureiter and F. Berr (2010) Gallengangskarzinom: Stellenwert der photodynamischen Therapie. Viszeralmedizin 26, 194-198.
436. Allison, R. R., E. Zervos and C. H. Sibata (2009) Cholangiocarcinoma: An emerging indication for photodynamic therapy. Photodiagn. Photodyn. Ther. 6, 84-92.
437. Shikowitz, M. J., A. L. Abramson, B. M. Steinberg, J. DeVoti, V. R. Bonagura, V. Mullooly, M. Nouri. A. M. Ronn, A. Inglis, J. McClay and K. Freeman (2005) Clinical trial of photodynamic therapy with meso-tetra (hydroxyphenyl) chlorin for respiratory papillomatosis. Arch. Otolaryngol. Head Neck Surg. 131, 99-105.
438. Aerts, I., P. Leuraud, J. Blais, A.-1. Pouliquen, P. Maillard, C. Houdaver, J. Couturier, X. Sastre-Garau, D. Grierson, F. Doz and M. F. Poupon (2010) In vivo efficacy of photodynamic therapy in three new xenograft models of human retinoblastoma Photodiagn. Photodyn. Ther. 7, 275-283.
439. Kruijt, B., E. M. van der Snoek, H. J. C. M. Sterenborg, A. Amelink and D. J. Robinson (2010) A dedicated applicator for light delivery and monitoring of PDT of intra-anal intraepithelial neoplasia. Photodiagn. Photodyn. Ther. 7, 3-9.
440. Van Der Snoek, E. M., A. Amelink, M. E. Van Der Ende, J. C. Den Hollander, J. G. Den Hollander, F. P. Kroon, R. Vriesendorp, H. A. M. Neumann and D. J. Robinson (2009) Photodynamic therapy with topical metatetrahydroxychlorin (Fosgel) is ineffective for the treatment of anal intraepithelial neoplasia, grade III. J. Acquir. Immune. Defic. Syndr. 52, 141-143.
441. Taylor, N. M. and M. L. Gonzalez (2009) The practicalities of photodynamic therapy in acne vulgaris. Br. J. Dermatol. 160, 1140-1148.
442. Meisel, P. and T. Kocher (2005) Photodynamic therapy for periodontal diseases: State of the art. J. Photochem. Photobiol. B: Biol. 79, 159-170.
443. Akilov, O. E., K. O'Riordan, S. Kosaka and T. Hasan (2006) Photodynamic therapy against intracellular pathogens: Problems and potentials. Med. Laser Appl. 21, 251-260.
444. Donnelly, R. F., P. A. McCarron and M. M. Tunney (2008) Antifungal photodynamic therapy. Microbiol. Rev. 163, 1-12.
445. Hansch, A., O. Frey, M. Gajda, G. Susanna, J. Boettcher, R. Bräuer and W. A. Kaiser (2008) Photodynamic treatment as a novel approach in the therapy of arthritic joints. Lasers Surg. Med. 40, 265-272.
446. Van den Bergh, H. (2001) Photodynamic therapy of age-related macular degeneration: History and principles. Sem. Ophthalmol. 16, 181-200.
447. Zuluaga, M.-F., C. Mailhos, G. Robinson, D. T. Shima, R. Gurny and N. Lange (2007) Synergies of VEGF inhibition and photodynamic therapy in the treatment of age-related macular degeneration. Invest. Ophthalmol. Vis. Sci. 48, 1767-1772.
448. Nitzan, T., R. Dror, H. Ladan, Z. Malik, S. Kimel and V. Gottfried (1995) Structure-activity relationship of porphines for photoinactivation of bacteria. Photochem. Photobiol. 62, 342-347.
449. Bombelli, C. F. Bordi, S. Ferro, L. Giansanti, G. Jori, G. Mancini, C. Mazzuca, D. Monti, F. Ricchelli, S. Sennato and M. Venanzi (2008) New cationic liposomes as vehicles of m-tetrahydroxyphenylchlorin in photodynamic therapy of infectious diseases. Mol. Pharmaceut. 5, 672-679.
450. Klesing, J., A. Wiehe, B, Gitter, S. Gräfe and M. Epple (2010) Positively charged calcium phosphate/polymer nanoparticles for photodynamic therapy. J. Mater. Sci. Mater. Med. 21, 887-892.
451. Schwiertz, J., A. Wiehe, S. Gräfe, B. Gitter and M. Epple (2009) Calcium phosphate nanoparticles as efficient carriers for photodynamic therapy against cells and bacteria. Biomaterials 30, 3324-3331.
452. Lüthi, M., E. Besic Gyenge, M. Engstrüm, M. Bredell, K. Grätz, H. Walt, R. Gmür and C. Maake (2009) Hypericin- and mTHPC-mediated photodynamic therapy for the treatment of cariogenic bacteria. Med. Laser Appl. 24, 227-236.
453. Engelhardt, V., B. Krammer and K. Plaetzer (2010) Antibacterial photodynamic therapy using water-soluble formulations of hypericin or mTHPC is effective in inactivation of Staphylococcus aureus. Photochem. Photobiol. Sci. 9, 365-369.
454. Melnikova, V. O., L. N. Bezdetnaya, D. Brault, A. Y. Potapenko and F. Guillemin (2000) Enhancement of meta-tetrahydroxyphenylchlorin-sensitized photodynamic treatment on human tumor xenografts using a water-soluble vitamin E analogue, Trolox. Int. J. Cancer 88, 798-803.
455. Korbelik, M. and J. Sun (2001) Cancer treatment by photodynamic therapy combined with adoptive immunotherapy using genetically altered natural killer cell line. Int. J. Cancer 93, 269-274.
456. Korbelik, M., J. Sun, I. Cecic and K. Serrano (2004) Adjuvant treatment for complement activation increases the effectiveness of photodynamic therapy of solid tumors. Photochem. Photobiol. Sci. 3, 812-816.
457. Chen, W. R., M. Korbelik, K. E. Bartels, H. Liu, J. Sun and R. E. Nordquist (2005) Enhancement of laser cancer treatment by a chitosan-derived immunoadjuvant. Photochem. Photobiol. 81, 190-195.
458. Separovic, D., J. Bielawski, J. S. Pierce, S, Merchant, A. L. Tarca, G. Bhatti, B. Ogretmen and M. Korbelik (2011) Enhanced tumor cures after Foscan photodynamic therapy combined with the ceramide analog LCL29. Evidence from mouse squamous cell carcinomas for sphingolipids as biomarkers of treatment response. Int. J. Oncol. 38, 521-527.
459. Zimmermann, A., H. Wall, U. Haller, P. Baas and S. D. Klein (2003) Effects of chlorin-mediated photodynamic therapy combined with fluoropyrimidines in vitro and in a patient. Cancer Chemother. Pharmacol. 51, 147-154.
460. Mickuviene, I., V. Kirveliene and B. Juodka (2004) Experimental survey of non-clonogenic viability assays for adherent cells in vitro. Toxicol. Vitro 18, 639-648.
461. Kirveliene, V., G. Grazeliene, D. Dabkeviciene, I. Micke, D. Kirvelis, B. Juodka and J. Didzipetriene (2006) Schedule-dependent interaction between doxorubicin and mTHPC-mediated photodynamic therapy in murine hepatoma in vitro and in vivo. Cancer Chemother. Pharmacol. 57, 65-72.
462. Canti, G., A. Calastretti, A. Bevilacqua, E. Reddi, G. Palumbo and A. Nicolin (2010) Combination of photodynamic therapy + immunotherapy + chemotherapy in murine leukemia. Neoplasma 57, 184-188.
463. Mallas, E., G. Karamanolis, M. Zissis, E. Karvouni, G. Kostopanagiotou, M. Macropoulou, A. A. Serafetinidis, S. Ladas and S. A. Raptis (2004) Photodynamic therapy in normal pig stomach: Protective effect of octreotide. Endoscopy 36, 893-4197.
464. Primo, F. L., L. Michieleto, M. A. M. Rodrigues. P. P. Macaroff, P. C. Morais, Z. G. M. Lacava, M. V. L. B. Bentley and A. C. Tedesco (2007) Magnetic nanoemulsions as drug delivery system for Foscan®: Skin permeation and retention in vitro assays for topical application in photodynamic therapy (PDT) of skin cancer. J. Magn. Magn. Maler, 311, 354-357.
465. Kreitner, M., K.-H. Wagner, G. Alth, R. Ebermann, H. Foiby and I. Elmadfa (2003) Haematoporphyrin- and sodium chlorophyllin-induced phototoxicity towards bacteria and yeasts - A new approach for safe foods. Forum Nutr. 56, 367-369.
466. Bonnett, R., M. A. Krysteva, I. G. Lalov and S. V. Artarsky (2006) Water disinfection using photosensitizers immobilized on chitosan. Water Res. 40, 1269-1275.
467. Westermann, P., T. Glanzmann, S. Folli, D. Braichotte, M. Forrer, S. Andrejevic, J. P. Mach. P. Monnier and H. van den Bergh (1995) Comparison of the influence of a water-soluble polymer carrier on the tumor localization and biodistribution of mesotetrametahydroxyphenylchlorin (mTHPC) in two animal models. Proc. SPIE Int. Soc. Opt. Eng. 2371, 45-50.
468. Cai, H. and C. K. Lim (1998) Comparison of HPLC, capillary electrophoretic and direct spectrofluorimetric methods for the determination of temoporfin poly(ethylene glycol) conjugates in plasma. Analyst, 123, 2243-2245.
469. Grahn, M. F., A. McGuinness, M. L. De Jode, A. Giger, A. S. Dhiman, C.-M. Cheung, S. Pavitt, R. Benzie and N. S. Williams (1997) In vivo photodynamic activity of mTHPC poly(ethylene glycol) conjugates (SC102). Proc. SPIE Int. Soc. Opt. Eng. 3191, 180-186.
470. Morlet, L., V. Vonarx, M.-T. Foultier, A. Gouyette, C. Stewart, P. Lenz and T. Patrice (1997) In vitro and in vivo spectrofluorometry of a water-soluble meta-(tetrahydroxyphenyl)chlorin (m-THPC) derivative. J. Photochem. Photobiol., B: Biol. 39, 249-257.
471. Ris, H.-B., V. I. Hof, C. M. Stewart, D. Mettler and H. J. Altermatt (1998) Endobronchial photodynamic therapy: Comparison of mTHPC and polyethylene glycol-derived mTHPC on human tumor xenografts and tumor-free bronchi of minipigs. Lasers Surg. Med. 23, 25-32.
472. Westennann, P., T. Glanzmann, S. Andrejevic, D. R. Braichotte, M. Forrer, G. A. Wagnieres, P. Monnier, H. Van Den Bergh, J.-P. Mach and S. Folli (1998) Long circulating half-life and high tumor selectivity of the photosensitizer meta-tetrahydroxyphenylchlorin conjugated to polyethylene glycol in nude mice grafted with a human colon carcinoma. Int. J. Cancer 76, 842-850.
473. Grahn, M. F., A. Giger, A. McGuinness, M. L. de Jode, J. C. M. Stewart, H.-B. Ris, H. J. Altermatt and N. S. Williams (1999) mTHPC polymer conjugates: The in vivo photodynamic activity of four candidate compounds. Lasers Med. Sci. 14, 40-46.
474. Hornung, R., M. K. Fehr, J. Monti-Frayne, B. J. Tromberg, M. W. Berns and Y. Tadir (1999) Minimally-invasive debulking of ovarian cancer in the rat pelvis by means of photodynamic therapy using the pegylated photosensitizer PEG-m-THPC. Br. J. Cancer 81, 631-637.
475. Ris, H.-B., T. Krueger, A. Giger, C. K. Lim, J. C. M. Stewart, U. Althaus and H. J. Altermatt (1999) Photodynamic therapy with mTHPC and polyethylene glycol-derived mTHPC: A comparative study on human tumour xenografts. Br. J. Cancer 79, 1061-1066.
476. Hornung, R., M. K. Fehr, H. Walt, P. Wyss, M. W. Berns and Y. Tadir (2000) PEG-m-THPC-mediated photodynamic effects on normal rat tissues. Photochem. Photobiol. 72, 696-700.
477. Rheinwald, M., U. Bauder-Wuest, H.-J. Sinn, H.-H. Schrenk and T. Haase (2000) Intracellular PDT activity of a pegylated form of meso-tetra-(hydroxy-phenyl)-chlorin (mTHPC). Proc. SPIE Int. Soc. Opt. Eng. 3909, 53-59.
478. Rovers, J. P., A. E. Saarnak, M. De Jode, H. J. C. M. Sterenborg, O. T. Terpstra and M. F. Grahn (2000) Biodistribution and bioactivity of tetra-pegylated meta-tetra(hydroxyphenyl)chlorin compared to native meta-tetra(hydroxyphenyl)chlorin in a rat liver tumor model. Photochem. Photobiol. 71, 210-217.
479. Schneider, M., G. Graschew, T. A. Roelofs, E. Balanos, S, Rakowsky, H.-J. Sinn and P. M. Schlag (2000) Multiphoton excitation and photodynamic activity of macromolecular derivatized mTHPC. Proc. SPIE Int. Soc. Opt. Eng. 3909, 60-65.
480. Roelofs, T. A., G. Graschew, M. Schneider, S. Rakowsky, H.-J. Sinn and P. M. Schlag (2001) Multiphoton versus single photon excitation of photosensitizers for laser-induced fluorescence diagnosis and photodynamic therapy of cancer cells. Proc. SPIE Int. Soc. Opt. Eng. 4262, 259-262.
481. Bourdon, O., I. Laville, D. Carrez, A. Croisy, P. Fedel, A. Kasselouri, P. Prognon, P. Legrand and J. Blais (2002) Biodistribution of meta-tetra(hydroxyphenyl)chlorin incorporated into surface-modified nanocapsules in tumor-bearing mice. Photochem. Photobiol. Sci. 1, 709-714.
482. Krueger, T., H. J. Altermatt, D. Mettler, B. Scholl, L. Magnusson and H.-B. Ris (2003) Experimental photodynamic therapy for malignant pleural mesothelioma with pegylated mTHPC. Lasers Surg. Med. 32, 61-68.
483. Lord, G. A., H. Cai, J. L. Luo and C. K. Lim (2000) HPLC-electrospray mass spectrometry for the analysis of temoporfinpoly(ethylene glycol) conjugates. Analyst 125, 605-608.
484. Petri, A., M. Kyriazi, E. Alexandratou, M. Rallis, S. Gräfe and D. Yova (2009) Evaluation of the PDT effect of Foscan® and Fospeg® in the LNCaP human prostate cancer cell line. Proc. SPIE 7373, 737311.
485. Ronn, A. M., M. Nouri, A. L. Abramson and F. Pecci (1999) Evaluation of the third generation photosensittser SC102 in two animal models. Lasers Med. Sci. 14, 307-318.
486. Tran, N., T. Krueger, Y. Pan, H. Yan, C. Cheng, H.-J. Altermatt, J.-P. Ballini, F. Borle, H.-B. Ris and S. Andrejevic-Blant (2007) Correlation of photodynamic activity and fluorescence signaling for free and pegylated mTHPC in mesothelioma xenografts. Lasers Surg. Med. 39, 237-244.
487. Mosqueira, V. C. F., P. Legrand, A. Gulik, O. Bourdon, R. Gref, D. Labarre and G. Barrati (2001) Relationship between complement activation, cellular uptake and surface physicochemical aspects of novel PEG-modified nanocapsules. Biomaterials 22, 2967-2979.
488. Bourdon, O., V. Mosqueira, P. Legrand and J. Blais (2000) A comparative study of the cellular uptake, localization and phototoxicity of meta-tetra(hydroxyphenyl) chlorin encapsulated in surface-modified submicronic oil/water carriers in HT29 tumor cells. J. Photochem. Photobiol., B: Biol. 55, 164-171.
489. Walt, H., M. Nap, A. M. Dorward, M. P. G. Leers, B. J. Tennent, Z. Varga, T. Stallmach and W. G. Beamer (2006) Early apoptotic responses in transgenic mouse mammary carcinoma for photodynamic therapy. Photodiagn. Photodyn. Ther. 3, 227-233.
490. Rovers, J. P., M. L. de Jode, H. Rezzoug and M. F. Grahn (2000) In vivo photodynamic characteristics of the near-infrared photosensitizer 5,10,15,20-tetrakis(M-hydroxyphenyl) bacteriochlorin. Photochem. Photobiol. 72, 358-364.
491. Lassalle, H.-P., L. Bezdetnaya, V. Iani, A. Juzeniene, F. Guillemin and J. Moan (2004) Photodegradation and phototransformation of 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorin (m-THPBC). Photochem. Photobiol. Sci. 3, 999-1005.
492. Grahn, M. F., A. McGuinness, R. Benzie, R. Boyle, M. L. de Jode, M. D. Dilkes, B. Abbas and N. S. Williams (1997) Intracellular uptake, absorption spectrum and stability of the bacteriochlorins photosensitizer 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorins (mTHPBC). Comparison with 5,10,15,20-tetrakis(m-hydroxyphenyl)chlorin (mTHPC). J. Photochem. Photobiol. B: Biol. 37, 261-266.
493. Rovers, J. P., M. L. de Jode and M. F. Grahn (2000) Significantly increased lesion size by using the near-infrared photosensitizer 5,10,15,20-tetrakis(m-hydroxyphenyl)bacteriochlorins in interstitial photodynamic therapy of normal rat liver tissue. Lasers Surg. Med. 27, 235-240.
494 Liu, D. and N. Zhang (2010) Cancer chemotherapy with lipid-based nanocarriers. Crit. Rev. Therap. Drug Car. Syst. 27, 371-417.
495 Juzenas, P., W. Chen, Y.-P. Sun, M. A. N. Coelho, R. Generalov, N. Generalova and I. L. Christensen (2008) Quantum dots and nanoparticles for photodynamic and radiation therapies of cancer. Adv. Drug Deliv. Rev. 60, 1600-1614.
496 Chen, B., B. W. Pogue and T. Hasan (2005) Liposomal delivery of photosensitizing agents. Expert Opin. Drug Deliv. 2, 477-487.
497 Cevc, G. and U. Vierl (2010) Nanotechnology and the transdermal route. A state of the art review and critical appraisal. J. Control. Release 141, 277-299.
498 Nishiyama, N., Y. Morímoto, W.-D. Jang and K. Kataoka (2009) Design and development of dendrimer photosensitizer-incorporated polymeric micelles for enhanced photodynamic therapy. Adv. Drug Deliv. Rev. 61, 327-338.
499 Bombelli, C., G. Caracciolo, P. Di Profio, M. Diociaiuti, P. Luciani, G. Mancini, C. Mazzuca, M. Marra, A. Molinari, D. Monti, L. Toccacieli and M. Venanzi (2005) Inclusion of a photosensitizer in liposomes formed by DMPC/gemini surfactant: Correlation between physicochemical and biological features of the complexes. J. Med. Chem. 48, 4882-4891.
500 Kuntsche, J., I. Freisleben, F. Steiniger and A. Fahr (2010) Temoporfin-loaded liposomes: Physicochemical characterization. Eur. J. Pharmaceut. Sci. 40, 305-315.
501 Mojzisova, H., S. Bonneau, P. Maillard, K. Berg and D. Brault (2009) Photosensitizing properties of chlorins in solution and in membrane-mimicking systems. Photochem. Photobiol. Sci. 8, 778-787.
502 Kachatkou, D., S. Sasnouski, V. Zorin, T. Zorina, M.-A. D'Hallewin, F. Guillemin and L. Bezdetnaya (2009) Unusual photoinduced response of mTHPC liposomal formulation (foslip). Photochem. Photobiol. 85, 719-724.
503 D'Hallewin, M. A., D. Kochetkov, Y. Viry-Babel, A. Leroux, E. Werkmeister, D. Dumas, S. Gräfe, V. Zorin, F. Guillemin and L. Bezdetnaya (2008) Photodynamic therapy with intratumoral administration of lipid-based mTHPC in a model of breast cancer recurrence. Lasers Surg. Med. 40, 543-549.
504 Svensson, J., A. Johannson, N. Bendsoe, S. Gräfe, T. Trebst, S. Andersson-Engels and K. Svanberg (2007) Pharmacokinetic study of a systemically administered novel liposomal Temoporfin formulation in an animal tumor model. Proc. SPIE Int. Soc. Opt. Eng. 6427, 64270T.
505 Svensson, J., A. Johansson, S. Gräfe, B. Gitter, T. Trebst, N. Bendsoe, S. Andersson-Engels and K. Svanberg (2007) Tumor selectivity at short times following systemic administration of a liposomal temoporfin formulation in a murine tumor model. Photochem. Photobiol. 83, 1211-1219.
506 Lasalle, H.-P., D. Dumas, S. Gräfe, M.-A. D'Hallewin, F. Guillemin and L. Bezdetnaya (2009) Correlation between in vivo pharmacokinetics, intratumoral distribution and photodynamic efficiency of liposomal mTHPC. J. Control. Release 134, 118-124.
507 Castro, D., M. Castro, M. Villafãne, R. M. Gobbi and P. Cazzola (2009) Temoporfin liposomal formulation: A medical device to improve skin structure. J. Plast. Dermatol. 5, 169-172.
508 Dragicevic-Curic, N., D. Scheglmann, V. Albrecht and A. Fahr (2009) Development of liposomes containing ethanol for skin delivery of temoporfin: Characterization and in vitro penetration studies. Coll. Surf. B Biointerf. 74, 114-122.
509 Molinari, A., C. Bombelli, S. Marinino, A. Stringaro, L. Toccacieli, A. Calcabrini, M. Colone, A. Mangiola, G, Maira, P. Luciani, G. Mancini and G. Arancia (2007) m-THPC-mediated photodynamic therapy of malignant gliomas: Assessment of a new transfection strategy. Int. J. Cancer 121, 1149-1155.
510 Molinari, A., M. Colone, A. Calcabrini, A. Stringaro, L. Toccacieli, G. Arancia, S. Mannino, A. Mangiola, G. Maira, C. Bombelli and G. Mancini (2007) Cationic liposomes, loaded with m-THPC, in photodynamic therapy for malignant glioma. Toxicol. Vitro 21, 230-234.
511 Bombelli, C., L. Giansanti, P. Luciani and G. Mancini (2009) Gemini surfactant based carriers in gene and drug delivery. Curr. Med. Chem. 16, 171-183.
512 Johansson, A., J. Svensson, N. Bendsoe, K. Svanberg, E. Alexandratou, M. Kyriazi, D. Yova, S. Gräfe, T. Trebst and S. Andersson-Engels (2007) Fluorescence and absorption assessment of a lipid mTHPC formulation following topical application in a non-melanotic skin tumor model. J. Biomed. Opt. 12, 034026.
513 Bendsoe, N., L. Persson, A. Johansson, J. Axelsson, J. Svensson, S. Gräfe, T. Trebst, S. Andersson-Engels, S. Svanberg and K. Svanberg (2007) Fluorescence monitoring of a topically applied liposomal temoporfin formulation and photodynamic therapy of nonpigmented skin malignancies. J. Environm. Pathol. Toxicol. Oncol. 26, 117-126.
514 Dragicevic-Curic, N., S. Winter, M. Stupar, J. Milic, D. Krajisnik, B. Gitter and A. Fahr (2009) Temoporfin-loaded liposomal gels: Viscoelastic properties and in vitro skin penetration. Int. J. Pharmaceut. 373, 77-84.
515 Dragicevic-Curic, N., S. Winter, D. Krajisnik, M. Stupar, J. Milic, S. Graefe and A. Fahr (2010) Stability evaluation of temoporfin-loaded liposomal gels for topical application. J. Liposome Res. 20, 38-48.
516 Dragicevic-Curic, N., D. Schlegelmann, V. Albrecht and A. Fahr (2009) Development of different temoporfin-loaded invasomes-novel nanocarriers of temoporfin: Characterization, stability and in vitro skin penetration studies. Coll. Surf. B:Biointerf. 70, 198-206.
517 Dragicevic-Curic, N., S. Gräfe, V. Albrecht and A. Fahr (2008) Topical application of temoporfin-loaded invasomes for photodynamic therapy of subcutaneously implanted tumours in mice: A pilot study. J. Photochem. Photobiol. B: Biol. 91, 41-50.
518 Dragicevic-Curic, N., D. Scheglmann, V. Albrecht and A. Fahr (2008) Temoporfin-loaded invasomes: Development, characterization and in vitro skin penetration studies. J. Control. Release 127, 59-69.
519 Dragicevic-Curic, N., S. Gräfe, B. Gitter and A. Fahr (2010) Efficacy of temoporfin-loaded invasomes in the photodynamic therapy in human epidermoid and colorectal tumour cell lines. J. Photochem. Photobiol. B: Biol. 101, 238-250.
520 Dragicevic-Curic, N., S. Gräfe, B. Gitter, S. Winter and A. Fahr (2010) Surface charged temoporfin-loaded flexible vesicles: In vitro skin penetration studies and stability. Int. J. Pharmaceutics 384, 100-108.
521 Primo, F. L., M. V. L. B. Bentley and A. C. Tedesco (2008) Photophysical studies and in vitro skin permeation/retention of Foscan®/nanoemulsion (NE) applicable to photodynamic therapy skin cancer treatment. J. Nanosci. Nanotechnol. 8, 340-347.
522 Konan, Y. N., J. Chevallier, R. Gurny and E. Allémann (2003) Encapsulation of p-THPP into nanoparticles: Cellular uptake, subcellular localization and effect of serum on photodynamic activity. Photochem. Photobiol. 77, 638-644.
523 Konan, Y. N., M. Berton, R. Gurny and E. Allémann (2003) Enhanced photodynamic activity of meso-tetra(4-hydroxyphenyl)porphyrin by incorporation into sub-200 nm nanoparticles. Eur. J. Pharm. Sci. 18, 241-249.
524 Vargas, A., B. Pegaz, E. Debefve, Y. Konan-Kouakou, N. Lange, J.-P. Ballini, H. Van Den Bergh, R. Gurny and F. Delie (2004) Improved photodynamic activity of porphyrin loaded into nanoparticles: An in vivo evaluation using chick embryos. Int. J. Pharmaceut. 286, 131-145.
525 Wacker, M., K. Chen, A. Preuss, K. Possemeyer, B. Röder and K. Langer (2010) Photosensitizer loaded HSA nanoparticles. I: Preparation and photophysical properties. Int. J. Pharmaceut. 393, 253-262.
526 Preuß, A., K. Chen, S. Hackbarth, M. Wacker, K. Langer and B. Röder (2011) Photosensitizer loaded HSA nanoparticles II: In vitro investigations. Int. J. Pharmaceut. 404, 308-316.
527 Bakalova, R., H. Ohba, Z. Zhelev, M. Ishikawa and Y. Baba (2004) Quantum dots as photosensitizers? Nature Biotechnol. 22, 1360-1361.
528 Yan, F. and R. Kopelman (2003) The embedding of metatetra(hydroxyphenyl)-chlorin into silica nanoparticle platforms for photodynamic therapy and their singlet oxygen production and pH-dependent optical properties. Photochem. Photobiol. 78, 587-591.
529 Compagnin, C. L. Ba, M. Mognato, L. Celotti, G. Miotto, M. Arduini, F. Morel, C. Fede, F. Selvestrel, I. M. R. Echevarria, F. Mancin and E. Reddi (2009) The cellular uptake of metatetra(hydroxyphenyl)chlorin entrapped in organically modified silica nanoparticles is mediated by serum proteins. Nanotechnology 20, 345101.
530 Mondon, K., R. Gurny and M. Möller (2008) Colloidal drug delivery systems - Recent advances with polymeric micelles. Chimia 62, 832-840.
531 Hofman, L-W., M. G. Carstens, F. Van Zeeland, C. Helwig, F. M. Flesch, W. E. Hennink and C. F. Van Nostrum (2008) Photocytotoxicity of mTHPC (temoporfin) loaded polymeric micelles mediated by lipase catalyzed degradation. Pharmaceut. Res. 25, 2065-2073.
532 Shieh, M.-L. C.-L. Peng, W.-L. Chiang, C.-H. Wang, C.-Y. Hsu, S.-J. J. Wang and P.-S. Lai (2010) Reduced skin photosensitivity with meta-tetra(hydroxyphenyl)chlorin-loaded micelles based on a poly(2-ethyl-2-oxazoline)- b -poly(d. I -lactide) diblock copolymer in vivo. Mol. Pharmaceutics 7, 1244-1253.
533 Cohen, E. M., H. Ding, C. W. Kessinger, C. Kehmtong, J. Gao and B. D. Sumer (2010) Polymeric micelle nanoparticles for photodynamic treatment of head and neck cancer cells. Otolaryngol. Head Neck Surg. 143, 109-115.
534 Peng, C.-L., L.-Y. Yang, T.-Y. Luo, P.-S. Lai, S.-J. Yang, W.-J, Lin and M.-J. Shieh (2010) Development of pH sensitive 2-(thisopropylamino)ethyl methacrylate based nanoparticles for photodynamic therapy. Nanatechnology 21, art. no. 155103.
535 Epple, M., K. Ganesan, R. Heumann, J. Klesing, A. Kovtun, S. Neumann and V. Sokolova (2010) Application of calcium phosphate nanoparticles in biomedici ne J. Maier. Client. 20, 18-23.
536 Reum, N., C. Fink-Straube, T. Klein, R. W. Hartmann, C.-M. Lehr and M. Schneider (2010) Multilayer coating of gold nanoparticles with drug-polymer coadsorbates. Langmuir 26, 16901-16908.
537 Petersen, S., A. Fahr and H. Bunjes (2010) Flow cytometry as a new approach to investigate drug transfer between lipid particles. Mol. Pharmaceutics 7, 350-363.
538 Ball, D. J., S. Mayhew. S. R. Wood. J. Griffiths, D. I. Vernon and S. B. Brown (1999) A comparative study of the cellular uptake and photodynamic efficacy of three novel zinc pht-halocyanines of differing charge. Photochem. Photobiol. 69, 390-396.
539 Berlanda, J., T. Kiesslich, V. Engelhardt, B. Krammer and K. Plaetzer (2010) Comparative in vitro study on the characteristics of different photosensitizers employed in PDT. J. Photochem. Photobiol. B: Biol. 100, 173-180.
540 Calzavara-Pinton, P. G., M. Venturini and R. Sala (2007) Photodynamic therapy: update 2006. Part 2: Clinical results. J. Eur. Acad. Dermatol. Venerol. 21, 439-451.
541 Wiehe, A., E. J. Simonenko, M. O. Senge and B. Roder (2001) Hydrophilicity versus hydrophobicity - Varying the amphophilic structure of porphyrins related to the photosensitizer m-THPC. J. Porphyrins Phthalocyanines 5, 758-761.
542 Ben-Dror, S., I. Bronshtein, A. Wiehe, B. Röder, M. O. Senge and B. Ehrenberg (2006) On the correlation between hydrophobicity, liposome binding and cellular uptake of porphyrin sensitizers. Photochem. Photobiol. 82, 695-701.
543 Senge, M. O., Y. M. Shaker, M. Pintea. C. Ryppa, S. S. Hatscher, A. Ryan and Y. Sergeeva (2010) Synthesis of meso-substituted ABCD-type porphyrins via functionalization reactions. Eur. J. Org. Chem, 237-258.
544 Wiehe, A., Y. M. Shaker, J. C. Brandt, S. Mebs and M. O. Senge (2005) Lead structures for applications in photodynamic therapy. Part 1: Synthesis and variation of m-THPC (Temoporfin) related amphiphilic A2BC-type porphyrins. Tetrahedron 61, 5535-5564.
545 Yang, Y.-T., C.-T. Chen, J.-C. Yang and T. Tsai (2010) Spray-dried microparticles containing polymeric micelles, encapsulating hematoporphyrin. AAPS J. 12, 138-146.
546 Atif, M., P. E. Dyer, T. A. Paget, H. V. Snelling and M. R. Stringer (2007) Two-photon excitation studies of m-THPC photosensitizer and photodynamic activity in an epithelial cell line. Photodiagn. Photodyn. Ther. 4, 106-111.
547 Pawlicki, M., H. A. Collins, R. G. Denning and H. L. Anderson (2009) Two-photon absorption and the design of two-photon dyes. Angew. Chem. Int. Ed. Engl. 48, 3244-3266.
548 Kogan, B. Y. (2004) Nonlinear photodynamic therapy. Photochemical dose leveling within a tumor by saturating a photosensitizer's triplet states. Photochem. Photobiol. Sci. 3, 360-365.
549 Mang, T. S. (2004) Lasers and light sources for PDT: Past, present and future. Photodiagn. Photodyn. Ther. 1, 43-48.
550 Jode, M. L., M. G. Dilkes, M. F. Grahn, P. B. Hart and A. L. Raven (1996) New LED source for photodynamic therapy: Preclinical study. Proc. SPIE Int. Soc. Opt. Eng. 2629, 299-305.
551 De Jode, M. L., J. A. Mcgilligan, M. G. Dilkes. I. Cameron, M. F. Grahn and N. S. Williams (1996) An in vivo comparison of the photodynamic action of a new diode laser and a copper vapour dye laser at 652 nm. Lasers Med. Sci. 11, 117-121.
552 Tirand, L., T. Bastogne, D. Bechet, M. Linder, N. Thomas, C. Frochot, F. Guillemin and M. Barberi-Heyob (2009) Response surface methodology: An extensive potential to optimize in vivo photodynamic therapy conditions. Int. J. Radiation Oncology Biol. Phys. 75, 244-252.
553 Kruijt, B., S. Kascakova, H. S. de Bruijn, A. van der Ploeg-van den Heuvel, H. J. Sterenbourg, D. J. Robinson and A. Amelink (2009) In vivo quantification of chromophore concentration using fluorescence differential path length spectroscopy. J. Biomed. Opt. 14, 034022.
554 Zhu, T. C. and J. C. Finlay (2008) The role of photodynamic therapy (PDT) physics. Med. Phys. 35, 3127-3136.
555 Berg, K., P. K. Selbo, A. Weyergang, A. Dietze, L. Prasmickaite, A. Bonsted. B. Ø. Engesaeter, E. Angell-Petersen, T. Warloe and A. Høgset (2005) Porphyrin-related photosensitizers for cancer imaging and therapeutic applications. J. Microsc. 218, 133-147.
556 Norum, O.-J., P. K. Selbo, A. Weyergang, K.-E. Giercksky and K. Berg (2009) Photochemical internalization (PCI) in cancer therapy: From bench towards bedside medicine. J. Photochem. Photobiol. B: Biol. 96, 83-92.
557 Selbo, P. K., A. Weyergang, A. Høgset, O. J. Norum, M. B. Berstad, M. Vikdal and K. Berg (2010) Photochemical internalization provides time- and space-controlled endolysosomal escape of therapeutic molecules. J. Control, Release 148, 2-12.
558 Rai, P., S. Mallidi, X, Zheng, R. Rahmanzadeh, Y. Mir, S. Elrington, A. Khurshid and T. Hasan (2010) Development and applications of photo-triggered theranostic agents. Adv. Drug Deliv. Rev. 62, 1094-1124.
559 Allison, R. R., V. S. Bagnato, R. Cuenca, G. H. Downie and C. H. Sibata (2006) The future of photodynamic therapy in oncology. Future Oncol. 2006. 2, 53-71.
560 Josefsen, L. B. and R. W. Boyle (2008) Photodynamic therapy: Novel third-generation photosensitizers one step closer? Br. J. Pharmacol. 154, 1-3.
561 Patrice, T., D. Olivier and L. Bourre (2006) PDT in clinics: Indications, results, and markets. J. Environm. Pathol. Toxicol. Oncol. 25, 467-485.
562 Pervaiz, S. and M. Olivo (2006) Art and science of photodynamic therapy. Clin. Exp. Pharmacol. Physiol. 33, 551-556.
563 Allison, R. R., H. C. Moata and C. H. Sibata (2004) Clinical PD/PDT in North America: An historical review. Photodiagn. Photodyn. Ther. 1, 263-277.
564 Hopper, C. (2000) Photodynamic therapy: A clinical reality in the treatment of cancer. Lancet Oncol. 1, 212-219.
565 Cunderlikova, B., J. Moan and I. Sjaastad (2005) pH dependent uptake of porphyrin-type photosensitizers by solid tumor cells in vitro is not induced by modification of transmembrane potential. Cancer Lett. 222, 39-47.
566 Kessel, D. and E. Sykes (1999) Transport, localization and phototoxicity of m-THPC Proc. SPIE Int. Soc. Opt. Eng. 3592, 37-42.
567 Glanzmann, T., J.-F. Theumann, D. Barichotte, M, Forrer, G. Wagnieres, H. Berg, S. Andrejevic and P. Monnier (1995) Pharmacokinetics of meso-(tetrahydroxyphenyl)chlorin (m-THPC) studied by fluorescence spectroscopy on early cancer of the cheek pouch mucosa of Golden Syrian hamsters. Proc. SPIE Int. Soc. Opt. Eng. 2324, 89-96.
568 Mlkvy, P., H. Messmann, J. Regula, M. Conio, M. Pauer, C. E. Millson, A. J. MacRobert and S. B. Bown (1998) Photodynamic therapy for gastrointestinal tumors using three photosensitizers-ALA induced PPIX, photofrin® and MTPHC. A pilot study. Neoplasma 45, 157-161.
569 Bown, S. G. (2003) Photodynamic therapy for cancer of the pancreas | [Traitement photodynamique du cancer du pancréas]. Acta Endosc. 33, 531-538.
570 Bombelli, C., A. Stringaro, S. Borocci, G. Bozzato, M. Colone, L. Giansanti, R. Sgambato, L. Toccaceli, G. Mancini and A. Molinari (2010) Efficiency of liposomes in the delivery of a photosensitizer controlled by the stereochemistry of a gemini surfactant component. Mol. Pharmaceutics 7, 130-137.
Mathias O. Senge*1,2 and Johan C. Brandt2
1 Medicinal Chemistry, Institute of Molecular Medicine, Trinity Centre for Health Sciences, Trinity College
Dublin, St. James's Hospital, Dublin 8, Ireland
2 SFI Tetrapyrrole Laboratory, School of Chemistry, Trinity College Dublin, Dublin 2, Ireland
Received 27 May 2011, accepted 5 August 2011, DOI: 10.1111/j.1751-1097.2011.00986.x
[dagger] Lead Structures for Applications in Photodynamic Therapy. Pari 3.
[double dagger] Dedicated to Professor Ray Bonnett.
* Corresponding author email: firstname.lastname@example.org (M. O. Senge)
© 2001 The Authors
Photochemistry and Photobiology © 2011 The American Society of Photobiology 0031-8655/11
Mathias O. Senge, born in Silbach, Germany (1961), studied chemistry and biochemistry in Freiburg, Amherst, Marburg and Lincoln and graduated as Diplom-Chemiker from the Philipps Universität Marburg in 1986. After a Ph.D. thesis in plant biochemistry with Prof. Horst Senger in Marburg (1989) and a postdoctoral fellowship with Prof. Kevin M. Smith at UC Davis, he moved to the Freie Universität Berlin and received his habilitation in Organic Chemistry in 1996. From 1996 on he was a Heisenberg fellow at the Freie Universität Berlin and UC Davis and held visiting professorships in Greifswald and Potsdam. In 2002 he was appointed Professor of Organic Chemistry at the Universität Potsdam and since 2005 holds the Chair of Organic Chemistry at Trinity College Dublin. He was the recipient of fellowships from the Studienstiftung des Deutschen Volkes and the Deutsche Forschungsgemeinschaft; from 2005 to 2009 he was a Science Foundation Ireland Research Professor. His main interests are synthetic organic chemistry, the chemistry and biochemistry of tetrapyrroles, photosynthesis and global photobiology, the application and history of photomedicine, crystallography and structural chemistry and medicinal and bioorganic chemistry.
Johan Brandt was born in Berlin, Germany. He attended the Free University Berlin and received his degree in organic and analytical chemistry in 2004 under the guidance of Professor G. Buntkowsky. In 2005, he worked with Prof. Mathias Senge in the SFI Tetrapyrrole Laboratory at Trinity College Dublin on the development of unsymmetrical, water-soluble photosensitizers. From 2006 to 2010 he was a postgraduate student in Professor Thomas Wirth's group at Cardiff University. Here his research interests were focussed on enabling dangerous reaction protocols in microflow systems. Since 2010 he has been pursuing an industrial career in the field of medical information.