Preclinical examination of first and second generation photosensitizers used in photodynamic therapy.

fliorochemkrry mid fhorohidogy Vol. 54, No. 6 , pp. 109>1107, 1991 Printed in Great Britain. All rights reserved

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YEARLY REVIEW

PRECLINICAL EXAMINATION OF FIRST AND SECOND GENERATION PHOTOSENSITIZERS USED IN PHOTODYNAMIC THERAPY Introduction Clinical applications of photodynamic therapy (PDT)" are largely responsible for tlhe escalating number of preclinical investigations involving determinants of photosensitization. Five multi-center Phase I11 clinical trials, designed to determine the efficacy of Photofrin I1 mediated PDT for tumors of the bronchus, esophagus and bladder, are currently in progress (Dougherty, 1989; Gomer, 1989; Henderson, 1989; Marcus, 1990). Individual investigator initiated clinical studies involving PDT for treating tumors of the head and neck, chest wall, cervix, peritoneal and pleural cavities, skin, and brain are also being performed. In addition, preclinical results continue to suggest possible applications of PDT for inactivating infectious organisms (Sieber et al., 1989; Neyndorff et al., 1990; Bedwell et a / . , 1990; Malik et al., 1990). This review will highlight preclinical and basic PDT investigations published during the past 24 years. The majority of these studies have focused on: (a) synthesis and initial evaluation of new photosensitizers; (b) identification of subcellular targets involved in PDT cytotoxicity; (c) evaluation and comparison of photosensitizer localiza1.ion and cytotoxicity for normal and malignant cells,; (d) defining in vivo treatment parameters associated with PDT toxicity; (e) determining normal tissue responses following PDT; and (f) documenting in vivo targets and systemic responses associated with PDT. For a comprehensive background on various PDT topics examined over the past 8-10 years, the reader may wish to scan previous Yearly Reviews written by Kessel (1984), Moan (1986), Spikes (1986), Dougherty (1987), Sieber (1987), Girotti (1990) and Rosenthal (1991). Additional background material on PDT can also be obtained from s,pecific books edited by Kessel and Dougherty (1'983), Doiron and Gomer (1984), Andreoni and Cubeddu (1984), Kessel (1985), Jori and Perria (1985), Gomer

*Abbreviations: BPD, benzoporphyrin derivative; ET2, etiopurpurin; HP, hematoporphyrin; HPD, hematoporphyrin derivative; H S V , Herpessimplex virus; LDL, low density lipoprotein; MC-540, merocyaniine 540; NMR, nuclear magnetic resonance; NPe6, mono-I-aspartyl chlorin e6; NT2, octaethylpurpurin; O,, singlet oxygen; PC, phthalocyanine; PDT, photodynami'c therapy; RIF, radiation induced fibrosarcoma.

(1987), Kessel (1990), Gomer (1990), and Morstyn and Kaye (1990).

Photosensitizer Synthesis and Evaluation The synthesis and evaluation of new photosensitizers for the treatment of malignant and infectious disorders continues to be an active area of investigation. A number of unique porphyrin dimers with ether linkages have recently been evaluated for tumor and normal skin phototoxicity (Pandey et al., 1990). Interestingly, the newly synthesized dimers have an improved therapeutic ratio when compared to Photofrin I1 in short term tumor and skin photosensitization assays using DBA mice. Synthetic diporphyrins and dichlorins were examined in order to obtain structureifunction relationships pertaining to the in vitro and ~n vivo localization of photosensitizers (Kessel et a / ., 1991b). The relative hydrophobicity of the different photosensitizers was found to be an important determinant for in vitro accumulation but not for in vivo effectiveness. Kessel et al. (1991a) also assessed the spectra properties of several diporphyrin ethers in different solvents and after accumulation in leukemic L-1210 cells. The joining of hematoporphyrin molecules by an ether linkage promoted drug accumulation in L-1210 cells while accumulation of mesoporphyrin or protoporphyrin molecules was decreased after similar chemical treatment. Increased photosensitizing activity is reported for hydroporphyrins such as chlorins and bacteriochlorins of the tetra(hydroxypheny1)porphyrin series (Bonnett et al., 1989). The chlorin and bacteriochlorin derivatives have red shifted absorption spectra (compared to HPD) as well as enhanced in vivo photosensitizing properties (measured by depth of tumor necrosis) when compared directly to the corresponding tetra(hydroxypheny1)porphyrins. Amphiphilic mixed acenannellated metallotetraazaporphyrins have been synthesized with the goal of improving intracellular localization (Gaspard et al., 1990). These compounds possess absorption spectra similar to phthalocyanines and have efficient in vitro photosensitizing properties which justify additional in vivo analysis. Several 0-substituted tetraphenyl porphyrins (picket fence porphyrins) have undergone extensive in vitro and in vivo evaluation (Barber et a / ., 1991). Solubility properties effected mitochondria1 uptake and photosensitivity. How-

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ever, the 3,l-meso tetrakis (0-propionamido phenyl) porphyrin was effective in both in vivolin vitro assays and in tumor regrowth experiments. Verdins, which are similar to chlorins in structure, continue to show promise due to efficient photochemical properties and an absorption peak at 700 nm. In vivo experiments demonstrate efficient photosensitizer mediated tumor regression when verdins are used to treat a squamous cell carcinoma growing in the hamster cheek pouch (Hayden et al., 1990). Purpurins are hydrophobic photosensitizers and metal derivatives of the free base purpurins have been synthesized and shown to cause in vivo tumor necrosis in transplanted tumors exposed to visible light (Morgan et al., 1990a). Tin and zinc derivatives of octaethylpurpurin (NT2) and etiopurpurin (ET2) were evaluated. The order of effectiveness is: SnET2 > SnNT2 > ZnET2 > ZnNT2. The tin derivative (SnNT2) mediates photodamage at sites of membrane transport while the metal free NT2 inhibits biosynthesis of DNA (Kessel, 1989~). Chlorins are reduced porphyrins which typically absorb strongly in the red region of the visible light spectrum (Spikes, 1990). These compounds (which also include purpurins) have large extinction coefficients at wavelengths above 650 nm, suggesting improved light transmission through tissue as well as greater photon efficiency when compared to porphyrins. Interestingly, highly absorbing photosensitizers have recently been suggested to have potential drawbacks related to light attenuation in tissue (Dougherty and Potter, 1991). The mono-laspartyl derivative of chlorin e6 (abbreviated MACE or NPe6) enters cells via endocytosis and partitions to a cytoplasmic lysosomal location (Roberts and Berns, 1989; Kessel, 1989a). In vivo analysis of NPe6 indicates efficient photodynamic action towards transplanted mouse mammary carcinomas and pharmacokinetic properties which suggest a major vascular component involved in the tumoricidal action of this photosensitizer (Gomer and Ferrario, 1990). Benzoporphyrin derivatives have significant extinction coefficients at around 690 nm and appear to have low density lipoprotein mediated localization parameters similar to those observed with HPD (Kessel, 1989b). Initial biodistribution data for the raaiolabeled benzoporphyrin monoacid derivative in mouse tumor models (Richter et al., 1990) are also similar to previously published results for HPD and Photofrin I1 (Bellnier et al., 1989~). The in vivo characteristics of 4 analogs of BPD have been investigated by Richter el al. (1991). Extensive biodistribution and clearance studies show that the pharmacological properties of all benzoporphyrin derivatives are similar in the DBA mouse-rhabdomyosarcoma tumor model. However, the monoacid forms of BPD have considerably more photodynamic activity than the corresponding diacid analogs. Tetracyanoethylene adducts of benzopor-

phyrin exhibited poor in vivo photosensitizing efficiency in a transplanted AY-27 rat bladder tumor while the dimethyl acetylenedicarboxylate adducts of benzoporphyrin were more effective than HPD and comparable to metallopurpurins (Morgan et al., 1990b). Pharmacological andlor physiological mechanisms for the differences in tumor response for the various Diels-Adler adducts has not been determined. The monoacid ring “a” derivative of benzoporphyrin has also been shown to effectively photosensitize viral contaminants (Neyndorff et al., 1990). In these studies, whole blood spiked with vesicular stomatitis virus was treated with the photosensitizer. Benzoporphyrin concentrations of 2-4 pglmL in whole blood could inactivate up to lo7 viruses when exposed to light. In other studies, the Friend virus complex was used as a model to study MC540 photosensitization of envelop virus (Sieber et al., 1989). High sensitivity to MC540 mediated photosensitization was observed for cell free virus, cell associated virus and virus transformed cells. The Gramnegative bacteria E . coli is insensitive to the photosensitizing action of both water soluble and lipid soluble zinc PC unless the outer membrane is altered (Bertoloni et al., 1990). When the outer membrane is altered there is selective photosensitization of the cytoplasmic membrane with no observable damage to DNA. The kinetics of HP photosensitization of Herpes simplex virus type I (HSV1) growing in either diploid and heteroploid cells has been studied by Pompei et al. (1989). The inactivation of HSV-1 was both drug dose and light dose dependent, and the viruses grown in heteroploid cells were more sensitive to inhibition than viruses grown in diploid cells. The degree of sulfonation of aluminum PC has major effects on in vitro photosensitizing efficiency (Berg et al., 1989). Aggregation of sulfonated AlPc increases with decreasing number of sulfonated groups. The disulfonated (AIPcS2) derivative is suggested to be the most promising candidate for PDT due to its high efficiency of in vitro photosensitization and low tendency to aggregate in cells. Chan et al. (1990) evaluated in vitro and in vivo pharmacokinetics of various sulfonated derivatives of aluminum PC using murine Colo 26 cells. These studies indicate an inverse correlation between the degree of sulfonation and in vitro photosensitizer retention. However, in vivo photosensitizer accumulation using the Colo 26 tumor growing in BALBIc mice was greatest with the tetrasulfonated derivative and least with the monosulfonated derivative. It is clear that the complexity of in vivo distribution patterns of sulfonated PC cannot be adequately predicted by in vitro analysis. Sulfonated aluminum naphthalocyanines are able to generate ‘02 at levels similar to that observed for corresponding PC but are unable to elicit significant photosensitivity toward V-79 Chinese hamster cells when

Yearly Review

compared to P C (Paquette et al., 1990). The inefficiency of sulfonated aluminum naphthalocyanines as in vitro photosensitizers may result from drug localization within non-vital cell constituents or formation of photoinactive adducts and aggregates. Slightly different results are observed for zinc naphthalocyanines. The least sulfonated (derivative of zinc naphthalocyanine exhibited some photosensitivity but increased sulfonation was associated with self-aggregation within cells and a concomitant decrease in photosensitization (Yates et al., 1990). Active chemotherapeutic agents such as anthracenediones, anthrapyrazoles and aminoanthraquinone derivatives exhibit both direct cytotoxicity and photosensitizing activity against human leukemia cells when wavelengths of light >475 nm are used (Reszka et al., 1990; Hartley et al., 1990). Significant oxygen consumption and formation of reactive oxygen species are observed upon light exposure. D N A strand breakage occurs following photosensitization of the anteracenedione agents but there was no evidence of photo-induced membrane damage. Phenoxazine dyes, including several Nile blue derivatives, localize selectively in animal tumors (Lin et al., 1991). Structural modifications produced compounds with substantially higher '02yields than the parent derivatives. In vitro photosensitization correlated with '02yields for these compounds. The preparation and purification of chalcogenapyrylium dyes have been described and efficient photodynamic action of the cationic selena and tellurapyrylium derivatives are observed in isolated mitochondria (Detty et al., 1990). Mitochondria1 damage is also observed when human U251 glioma cells are incubated with these compounds and exposed to light. These photosensitizers absorb light in the near infrared (700-800 nm) and have low lo2quantum yields compared to most porphyrins. Powers et al. (1989) have observed that several cationic chalcogenapyrylium dyes exhibit differential toxicity (dark and light) to glioma cells when compared directly to normal skin fibroblasts. The synthesis and in vitro phototoxicity of new ringsubstituted cationic PC have been reported by Leznoff et al. (1989). The water soluble PC was produced in an attempt to exploit the reported specificity of cationic photosensitizers for mitochondria of carcinoma cells. Initial in vitro photosensitizing efficiency of the cationic PC is low and in vivo specificity has not been determined. A novel method of converting fluorescein isothiocyanate-conjugated antibodies to efficient photodynamic sensitizers via iodination has been reported by Devanathan et al. (1990). Mild chemical iodination did not destroy the specificity or activity of antibody. Fluorescein-labeled anti-Escherichia coli antibody was converted into a photodynamic sensitizer that selectively kills E. coli while sparing closely related species. Potential applications of this procedure include blood product eradication of PAP 54:6-0

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viruses and bone marrow purging of tumor cells. Spin trapping analysis following photoexcitation of pheophorbide a , H P and protoporphyrin in ethanol indicate the production of reactive oxygen species including superoxide and secondary radicals (Haseloff and Ebert, 1989). Action spectra and quantum yields for '02generation by MC540 in liposomes and in isolated erythrocyte membranes were obtained using electron spin resonance techniques (Singh et al., 1991). The action spectra of '02generation following MC540 photosensitization overlapped the absorption spectra of the monomeric form of the drug. The quantum yield for MCS40 generated lo2 was about one tenth the value obtained for Rose Bengal. Cellular Targets and Biochemical Responses of PDT Damage to the endoplasmic reticulum of SV-40 transformed human fibroblasts (Wi26-VA4) is observed following light exposure when cells are incubated with low density lipoprotein loaded with Photofrin I1 (Candide et al., 1989). These experiments suggest that injury to the endoplasmic reticulum (documented by decreased activity of acyl-coenzyme A:cholesterol-0-acyltransferase) may be an important target in PDT. Membrane damage in the form of lipid peroxidation has also been documented to play a major role in photosensitizer mediated cytotoxicity (Girotti, 1990; Thomas et al., 1989). The use of selenium depleted cells has provided a novel method of identifying glutathione peroxidase as a natural protectant against photosensitization (Thomas and Girotti, 1989a). Studies measuring alterations in the plasma membrane potential of mouse myeloma cells treated with a mixture of mono and disulfonated zinc PC and light demonstrate that membrane depolarization is an early event following photosensitization (Specht and Rodgers, 1990). Membrane depolarization exhibits both photosensitizer concentration and light dose dependency. Potentiation of in vitro photosensitization has been observed when V-79 Chinese hamster cells are treated with the K '/Hi ionophore nigericin and chloroaluminium PC (Varnes et al., 1990). Incubation with the ionophore did not affect cellular uptake of the PC. Nigericin appears to potentiate photosensitization by perturbing ion transport across mitochondria1 and/or plasma membranes. Membrane damage induced by porphyrin mediated P D T also appears to be responsible for release of prostaglandin E2 from murine tumor cells and macrophages (Henderson and Donovan, 1989). Agents which inhibit phospholipase and cylcooxygenase activity (such as indomethacin, meclofenamate and dexamethasone) inhibited PGE2 release. Interestingly, there appears to be sufficient release of intracellular calcium stores following P D T to acti-

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vate phospholipase even when external calcium is removed. The inflammatory and immunosuppressive responses observed during in vivo PDT (Reed et al., 1989~;Ferrario and Gomer, 1990; Fingar et af., 1990) may be associated with prostaglandin andlor thromboxane release. Selective photooxidative damage to lysosomes in cultured mouse macrophages has been reported following light activation of acridine orange (Zdolsek et af., 1990). Peroxidative injury to lysosomal membranes appears to be involved in the observed cytotoxicity and cell survival following acridine orange photosensitization can be increased by inhibiting lysosoma1 proteases. Photosensitization of both human and murine mast cells with porphyrins induces histamine release (Glover et al., 1990). The mast cell activation is associated with loss of membrane integrity and can be inhibited by catalase. Interestly, histamine release is independent of extracellular calcium in rodent mast cells, but is markedly reduced in the absence of calcium in human cells. Histamine release is also observed following in vivo porphyrin photosensitization (He et al., 1989). The in vivo data suggest that mast cells participate in the late phase of HpD-induced phototoxicity in mice. Sites of cellular damage have been investigated following MC540 photosensitization of L1210 cells (Gaffney and Sieber, 1990). Plasma membrane bound enzyme activities (Na+/K+ ATPase, Mg2+ ATPase, 5'-nucleotidase) are significantly reduced following MC540 photosensitization but cytosolic enzymes (lactate dehydrogenase and malate dehydrogenase) remain intact. The data support the hypothesis that the plasma membrane is the major target of MC.540 photosensitization. Bachowski et af. (1991) documented that MC540 sensitized plasma membranes accumulate lipid hydroperoxides and that this process is most probably mediated by a Type I1 photochemical reaction. Interestingly, the presence of additional iron and ascorbate resulted in an enhanced burst of lipid peroxidation. The amplification of MC540 induced peroxidation by ironlascorbate may be useful in enhancing the therapeutic effect of this photodynamic treatment. MC540 photosensitization also induces greater than 5 logs of kill for Burkitt's lymphoma cells and HL60 leukemia cells while producing minimal cytotoxicity to normal precursor cells (Gulliya and Pervaiz, 1989). Experiments related to MC540 photosensitization of L1210 leukemia cells also demonstrate an oxygen dependent process using unsaturated plasma membrane lipids as substrates (Gaffney et al., 1990). Interestingly, these studies also indicate that trypan blue exclusion assays can greatly underestimate the cytotoxic effects of MC540 photocytotoxicity. Several immunological reactions are associated with photodynamic action. Mitogenic stimulation of human peripheral blood lymphocytes is inhibited by PC mediated photosensitization (Kol et af., 1989)

and this response may involve both membrane alteration and signal transduction modifications. Porphyrin mediated photosensitization inhibits binding of mouse IgG2a antibodies to the ligand binding site of 72 kDa high affinity receptors (FcFI) on human peripheral blood monocytes (Krutman et af., 1989). The inhibition appears to be highly specific with structural alteration rather than loss of the receptor molecule from the cell surface. Interestingly, a possible role of superoxide anion in this PDT response was observed. Thioglycollate elicited murine macrophages treated with Photofrin I1 mediated PDT exhibit a dose dependent production of tumor necrosis factor suggesting that this cytokine may be involved in the vascular changes induced by PDT (Evans et af., 1990). Photooxidative damage to proteins (glyceraldehyde 3 phosphate dehydrogenase, alcohol dehydrogenase and myoglobin) have been biochemically analyzed following exposure to '02or hydroxyl radicals (Prinsze et al., 1990). Singlet oxygen (induced by illumination of protein solutions to HPD) produced crosslinked aggregates while hydroxyl radicals (induced with a hypoxanthinelxanthineoxidasel Fe3+-EDTA reaction) produced both crosslinked aggregates and fragmentation. Damaged proteins were more susceptible to proteolysis than undamaged proteins. These results suggest that limited protein oxidation may have a pronounced influence on protein structure and that protein alterations will vary with the type of oxidant exposure. In vitro porphyrin photosensitivity has been examined in cell lines resistant to hyperthermia (Gomer et al., 1990). Cross resistance between hyperthermia and PDT is not observed, which suggests that mechanism(s) of cytotoxicity are different for PDT and hyperthermia even though subcellular targets (such as the plasma membrane) and types of damage (protein denaturation) may be similar for the two treatment modalities. Studies by Boegheim et al. (1989b) indicate that membrane transport systems (such as the 2-aminoisobutyric acid transport system) as well as generalized protein synthesis are sensitive to PDT. However, the inhibition of these systems does not appear to play a crucial role in loss of clonigenicity in L-929 fibroblasts. Membrane transport has also been examined by Boegheim et af. (1989a) following the combination of PDT and hyperthermia. Mitochondria1 targeting and damage analysis have been reviewed in the context of photosensitization (Salet and Moreno, 1990). Impairment of ATP synthesis is one of the major factors involved in cell death following porphyrin photosensitization. Mechanistic studies involving the photosensitizing action of Victoria blue and chalcogenapyrylium dyes were performed in isolated rat liver mitochondria (Modica-Napolitano et al., 1990). Victoria blue mediated photosensitization produced selective inhibition of mitochondria1 respiratory Complex I

Yearly Review

while chalcogenapyrylium photosensitization inhibited both Complex I and Complex 11. The chalcogenapyrylium dye also inhibits membrane bound enzymes but not mitochondrial matrix enzymes. Biochemical analysis of P D T induced damage to transplanted R3230AC mammary carcinomas in rats has been investigated by Gibson et ul. (1989b). Maximal inhibition of mitochondrial enzymes is observed 24 h after treatment while no inhibition of a cytosolic enzyme (i.e. pyruvate kinase) is observed during an extended 168 h evaluation period. Mitochondrial enzyme inhibition is both drug dose and light dose dependent. The order of in vivo mitochondrial enzyme photosensitivity is: cytochrome c oxidase > FoFl ATPase > succinate dehydrogenase > N A D H dehydrogenase. Two strains of mouse lymphoma L5178Y cells, LY-R and LY-S, have been found to differ in sensitivity to chloroaluminum PC mediated photosensitization (Ramakrishana et al., 1989). The LYR strain was more photosensitive than the LY-S strain. Both strains exhibit similar levels of P D T induced D N A single strand breaks but the LY-R strain has more DNA-protein crosslinks as well as more rapid and extensive D N A degradation. Interestingly, both strains have similar photosensitizer uptake properties. Strains of LS178Y mouse lymphoma cells differing in D N A repair capacities have also provided novel information regarding cytotoxicity and mutagenic properties of ehloroaluminum PC mediated photosensitization (Evans et al., 1989). PC plus light is mutagenic at the heterozygous thymidine kinase (tk) locus in strain LYS1 cells. This study suggests that cytotoxic and mutagenic lesions induced by P C mediated photosensitization may be different. Porphyrin mediated photosensitization can enhance the transcription and translation of several oxidative stress genes (Gomer et al., 1989). Enhanced expression of the gene encoding for heme oxygenase is observed following Photofrin I1 incubation as well as following Rose Bengal or Photofrin I1 mediated photosensitization (Gomer et al., 1991). Increased expression of heme oxygenase mRNA is accompanied by a concomitant increase in the synthesis of the heme oxygenase protein. The significance of heme oxygenase induction following P D T is not known; however, it is feasible that this enzyme may have a role in antioxidant defenses. Clonogenic procedures are frequently used to evaluate in vitro survival parameters following photosensitization (Gomer, 1989, 1990). However, the trypan blue exclusion assay is considerably less sensitive at estimating P D T mediated cytotoxicity. Croisy et al. (1990) report that trypan blue dye exclusion does not consistently agree with clonigenic assay results following H p D photosensitization. Similar results have been observed by Gaffney et al. (1990) using MCS40. Photosensitization using Photofrin I1 and various second generation com-

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pounds continues to be effective at inactivating most cell types examined, including: human mesothelioma cells (Keller et al., 1990); human lung adenocarcinoma cells (Matthews et al., 1989a; Perry et al., 1990); murine pancreatic carcinoma cells (Matthews and Cui, 1990); human and rat retinoblastoma cells (Ohnishi et al., 1990; Winther, 1989a, b); Herpes simplex virus (Pompei et ul., 1989); human bladder carcinoma cells (Pope et al., 1990; Shea et al., 1990); human endometrium and ovarian carcinoma cells (Raab et al., 1990); human leukemic cells (Jamieson et al., 1990; Malik et al., 1989); Friend erythroleukemia virus and Friend virus transfected cells (Sieber et ul., 1989); murine myeloma cells (Specht and Rodgers, 1990); murine neuroblastoma cells (Rogers et al., 1991); human colon adenocarcinoma cells (West, 1989; West and Moore, 1989); bovine endothelial cells (West et al., 1990); human keratinocytes (Artuc et al., 1989) and murine macrophages (Zdolsek et al., 1990). Photofrin I1 induced photosensitivity of six human lung cancer cell lines and one normal lung fibroblast line has been reported by Perry et al. (1990). Inherent differences in cell survival were observed following PDT but there was no clear correlation between sensitivity and photosensitizer levels in the various lung tumor cells. Korbelik et al. (1991) have shown that murine peritoneal macrophages accumulate more Photofrin I1 than a murine squamous carcinoma cell line and uptake of Photofrin I1 by macrophages is dominated by phagocytosis. Differential sensitivity of various cell types to P D T continues to be an area of active investigation. Increased sensitivity of human smooth muscle cells derived from atherosclerotic plaques to Photofrin I1 mediated P D T was observed when compared to smooth muscle cells obtained from non-atherosclerotic arteries (Dartsch et al., 1990). However, it is unclear whether the differential photosensitization is due to porphyrin levels in the cells. Similarly, H P D mediated photosensitization is increased for murine L1210 leukemia cells compared to normal hematopoietic progenitor cells, but in vitro drug levels have not been determined for the various cell lines (Foultier et al., 1989). Human and murine bladder cancer cell lines as well as normal fibroblast cells have been used by Yu et al. (1990) as targets of methylene blue mediated photosensitization. Significant methylene blue induced photoinactivation of both tumor cells and fibroblasts is observed. Continued evidence for a vascular role in P D T mediated toxicity comes from the report that bovine endothelial cells are more sensitive to H P D plus light than a human colon adenocarcinoma cell line (West et al., 1990). Increased drug uptake is also observed in the endothelial cells. Additional experiments showed that exponentially growing cells were more sensitive to P D T than plateau-phase cells and this may also be related to intracellular levels of photosensitizer. Aluminum PC tetrasulfonated pref-

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erentially photosensitizes a human fibrosarcoma cell line (HT-1080) compared to normal human skin fibroblasts when DNA synthesis, protein synthesis and the M l T assay (an indirect index of mitochondrial activity) are used (Glassberg et a[., 1990). Differential sensitivity is most pronounced when either an 8 or 24 h efflux period in photosensitizer free medium occurs prior to light exposure. Antibody targeted photosensitization has been investigated for several years and may still prove to be a selective means of enhancing PDT. A dextran carrier has been used for the covalent binding of Sn(1V) chlorin-e6 to an anti-melanoma antibody (Rakestraw et al., 1990). Competitive inhibition radioassays indicate that these conjugates exhibit excellent retention of antigen binding activity. Selective in vitro photolysis of SK-MEL-2 human melanoma cells is obtained only for conjugates which have significant cellular attachment. Bachor et al. (1991) have shown that chlorin-e6 covalently bound to polystyrene microspheres is efficiently taken up by human bladder carcinoma cells. The chlorin conjugate is localized within the lysosomes following uptake via phagocytosis. Alterations in photosensitizer incubation parameters can modulate in vitro responses to PDT including the targets involved in cytotoxicity. Liposome bound porphyrins (HP or hematoporphyrin dimethylester) are taken up and retained by HeLa cells to a greater extent than HP dissolved in aqueous solution (Milanesi et al., 1989). In addition, subcellular damage sites associated with photosensitization are also different for the two incubation protocols. Liposomal porphyrin conditions are associated with extensive cytoplasmic and mitochondrial damage while aqueous porphyrin conditions result in plasma membrane damage. Incubation of Photofrin I1 in various components of plasma have been shown by Korbelik and Hung (1991) to modulate the uptake of the photosensitizer in cultured cells. The best retention of Photofrin I1 in cells is obtained when the photosensitizer is associated with globulins while inhibition of Photofrin I1 uptake occurs when the photosensitizer is bound to albumin. Studies with Zn-PC demonstrate that the distribution of this hydrophobic photosensitizer among serum proteins can be modulated to some extent by the nature of the liposomal vesicle used in drug delivery (Ginevra et al., 1990). The presence of cholesterol in DPPC liposomes optimizes the accumulation of the photosensitizer in LDL. Translocation of fluorescent components of HPD has been examined in human bladder tumor cells by Shulok et al. (1990). HPD uptake into the cell membrane was rapid, while subsequent localization was observed to be of a diffuse cytomembrane nature without discreet organelle retention. Multicellular spheroids derived from human colon adenocarcinoma cells exhibit a size dependent decrease in Photofrin I1 mediated photosensitization

when compared to monolayer cultures (West, 1989). Cell contact effects, drug heterogeneity between cells, hypoxia and problems in drug penetration are suggested as possible reasons for the resistance of large spheroids to PDT. The significance of dose (fluence) rate of delivered light during PDT remains an important issue in regards to potential thermal effects and cellular PDT repair mechanisms. Recent in vitro experiments demonstrate an increase in cell survival when the dose rate of delivered light is reduced to less than 0.3 mW/cm2 (Matthews et al., 1989b). These results suggest that cellular repair is operational at decreased fluence rates in a manner analogous to that observed for mammalian cells exposed to ionizing radiation. In vivo Pharmacology and Toxicology of Photosensitizers Multiple processes appear to be involved in PDT mediated tumor necrosis. Pharmacologic and photosensitizing responses associated with PDT on neoplastic cells, microvasculature, non-vascular stroma and on circulating components of the blood have been reviewed by Jori (1990), and Zhou (1989). Second generation photosensitizers offer potential advantages over Photofrin I1 including chemical purity and a major absorption band at wavelengths greater than 650 nm. The in vivo pharmacological properties of NPe6 have been documented and the photosensitizing potential of the dye has been directly compared to Photofrin I1 for both tumor and normal skin response (Gomer and Ferrario, 1990). Pharmacological properties of NPe6 are similar to published reports for most porphyrin photosensitizers. Interestingly, NPe6 is ineffective at inducing tumor cures when a 24 h time interval between drug administration and light treatment is used. However, PDT induced tumor cures (transplanted BA mammary carcinoma in C3H mice) are obtained when NPe6 is administered 4-6 h prior to light exposure, and the NPe6-PDT treatment parameters are as effective as standard PhotofrinI1 mediated PDT. The data suggest that plasma concentrations of NPe6 may be a more important predictive factor than tumor tissue levels of the photosensitizer for production of PDT-mediated tumor cures. The murine radiation induced fibrosarcoma (RIF) tumor model (with in vitro, in vivo and in vivolin vitro survival assays) has proven to be extremely valuable in distinguishing between vascular and direct tumor cell damage associated with PDT. Recent experiments by Henderson and Fingar (1989) have used the RIF tumor model to compare in vivo levels of 14C-Photofrin I1 to in vitro and in vivo photodynamic cell inactivation. In vivo porphyrin uptake in tumor tissue was linear over a 10-100 mg/kg range of doses. In addition, in vivolin vitro studies demonstrated that the przrequisites for

Yearly Review

tumor destruction via direct photodynamic tumor cell inactivation include high tumor drug concentrations and insensitivity of the tumor vasculature to PDT. Interestingly, tumor cell destruction can still occur as a consequence of PDT induced ischemia under conditions where the tumor bed is sensitive to PDT. This investigation also demonstrates that direct in vivo photodynamic cytotoxicity can be severely limited by PDT induced hypoxia. A n in vivoiin v i m retinoblastoma-like tumor model growing in the eye of F-344 rats exhibits biphasic cell inactivation following Photofrin-I1 mediated P D T (Winther, 1989b). The results suggest that both direct and indirect tumor destruction occur after PDT. This intraocular rat tumor has also been used to investigate the toxic effects of P D T on tumor and normal ocular tissue (Winther and Overgard, 1989). A reciprocal relationship between light energy doses and Photofrin I1 doses is observed for both curability and for normal tissue damage. Changes in tissue and cellular p H can have significant effects on porphyrin biodistribution (Pottier and Kennedy, 1990). Barrett et al. (1990) propose a p H sensitive mechanism for selective uptake of porphyrin compounds which involves both tissue distribution and cell membrane penetr,ation. Modulation of in vivo HPD pharmacology as well as photosensitizer treatment effectiveness has been reported by Thomas and Girotti (1989b). Rhabdomyosarcoma tumors in rats made hyperglycemic by multiple injections of glucose exhibit a transient decrease in pH and an increased retention of HPD. P D T treatment of tumors in glucoseiHPD administered animals resulted in enhanced cytotoxicity compared to galactoseiHPD treated controls. Photofrin I1 labeled with indium-11 I was used in biodistribution studies designed to evaluate porphyrin localization in papillomavirus induced cutaneous papillomas in rabbits (Shikowitz et al., 1989). A t 50 h post injection the papillomas retained approximately 5 times as much "'In-Photofrin I1 as adjacent normal skin. The papillomas also retained approximately twice as much photosensitizer as normal larynx. Laryngeal papillomas and carcinomas of the larynx are usually thin and assessable by laser generated light delivered through fibers. Toxicology studies performed by Abramson (1990) show that normal canine larynx is relatively resistant to Photofrin I1 mediated P D T using clinically relevant treatment doses (3 mgikg Photofrin 11, 100 J/cm2). Visual observations following laryngeal PDT indicate that only mild edema and erythema are induced by doses which would be expected to produce significant tumoricidal action. Pharmacokinetics of Zn-PC in a mouse fibrosarcoma tumor model have been examined using dipalmitoyl-phosphatidylcholine(DPPC) liposomes and LDL as drug carriers (Reddi et a / . , 1990). Increased Zn-PC tumor uptake and improved selectivity was obtained with the LDL carrier. Interest-

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ingly, the amount of Zn-PC in the tumor decreases very slowly as a function of time following administration. Ultrastructural analysis of Zn-PC mediated photosensitization in this tumor model shows an early (3 h) component of photodamage to malignant cells (corresponding to mitochondria1 and endoplasmic reticulum injury) while capillary damage occurring later (15 h) (Milanesi et al., 1990). These results support the hypothesis that LDL plays a major role in the delivery of Zn-PC directly to tumor tissue. This tumor model has also been used to document the pharmacokinetic behavior and phototherapeutic effectiveness of bis(di-isobutyloctadecylsiloxy)-2,3naphthalocyanatosilicon (iso-BOSiNc) incorporated into DPPC liposomes (Cuomo et al., 1990). IsoBOSiNc has an extensive absorption peak at -780 nm and the initial data indicate that this drug is a highly effective tumor photosensitizer. Peng et al. (1990) have utilized laser scanning fluorescence microscopy to analyze intratumor localization patterns of lipophilic and hydrophilic photosensitizers. Lipophilic compounds such as Photofrin I1 and monosulphonated PC localize within tumor cells. The hydrophilic dyes such as the tri and tetra sulphonated PC localize primarily in extracellular stroma of the tumor. Experiments designed to monitor fluorescence of aluminum PC tetrasulphonate in a human melanoma transplanted into nude mice demonstrate a transient decrease in fluorescence during light exposure (Moan et al., 1990). These observations suggest that the PC is at an extracellular location in the tumor since the fluorescence intensity of this photosensitizer increases during light exposure of cells in culture. Type I1 photochemical generation of '02has long been implied as the major reactive oxygen specie involved in tissue damage following porphyrin mediated P D T (Gomer, 1989). However, superoxide anions and other reactive oxygen intermediates may be generated via an hypoxanthineixanthine oxidase reaction in skin following initial P D T exposure (Athar et al., 1989). P D T damage to mitochondria can initiate catabolism of high-energy phosphates and the formation of hypoxanthine. P D T induced increases in intracellular calcium may activate calcium dependent proteases which can then convert xanthine dehydrogenase to xanthine oxidase. The hypoxanthineixanthine oxidase pathway can then lead to the oxygen dependent generation of numerous strong oxidants capable to damaging tissues. Agarwal et al. (1991) have utilized an in v i m rat epidermal microsome system to demonstrate that chloro-aluminum P C tetrasulfonate mediates photodestruction primarily by a Type I1 '02photochemical pathway. Cutaneous porphyrin photosensitization has been examined in albino mice administered Photofrin-I1 (Bellnier and Dougherty, 1989b). A direct correlation is observed between ear swelling response and the concentration of Photofrin I1 in the blood

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at the time of light exposure. Interestingly, there is no correlation between ear swelling response and levels of Photofrin I1 in the ear tissue of exsanguinated mice. This study suggests that ear response analysis following PDT may not provide a true estimate of potential skin damage following photosensitizer administration. Thiol containing compounds, including WR-2721, were compared as photoprotectors by Bellnier and Dougherty (1989a). WR-2721 provided statistically significant protection against porphyrin induced murine foot photosensitization but the compound also protected against PDT induced phototoxicity in a transplanted mammary tumor in the same mouse model. These studies suggest that there may not be a therapeutic advantage to using WR-2721 during PDT. The degree of skin photosensitivity has been evaluated for both mice and guinea pigs administered either Photofrin 11, chloroaluminum sulfonated PC, or NPe6 (Roberts et al., 1989). Major skin damage is produced in animals injected with Photofrin I1 but not with either of the second generation photosensitizers when light treatments were administered 24 h after drug injection. Prior photodegradation (photobleaching) of Photofrin I1 had little influence on subsequent induction of skin photosensitization. Skin photosensitivity reactions in albino mice also have been compared for Photofrin I1 and aluminum sulfonated PC (having an average of 3 sulphonic acid groups) as a function of (i) the time course of skin reactions; (ii) effect of time intervals between photosensitizer administration and light treatment and (iii) quantitative dose responses (Tralau et al., 1989). A xenon arc lamp (mimicking solar sun light) was used in all experiments. Photofrin I1 reactions were always more severe than reactions observed with the PC and the responses induced with the porphyrin persisted for longer time periods. Direct intratumor injection of Photofrin I1 has been compared to intraperitoneal drug administration for rats with transplanted mammary adenocarcinomas (Gibson et al., 1990) and for hamsters with human choriocarcinoma transplanted in the cheek pouch (Brand et al., 1989, 1990). The studies indicate that intratumor injection of Photofrin II can enhance the efficacy of PDT therapy. Continued evidence that vascular injury is a primary in vivo site of PDT damage has led to an investigation of vasoactive drugs in combination with PDT by Cowled and Forbes (1989). Noradrenaline, propranonol, hydralazine and phenoxybenzamine inhibited tumoricidal effects of PDT by reducing porphyrin uptake in tumors. Verapamil, on the other hand, enhanced PDT mediated tumor destruction and the enhancement was associated with increased porphyrin uptake and possible inhibition of capillary ingrowth. Blood flow analysis using the microsphere technique following Sn ET2 photosensitization demonstrates a rapid decrease in blood

flow which is not inhibited by systemic heparinization (Selman et al., 1990). Thromboxane release and resulting vascular stasis are specific in vivo responses following porphyrin mediated PDT (Fingar et al., 1990). Indomethacin has been shown to suppress the PDT induced release of thromboxane in Sprague-Dawley rats with transplanted chondrosarcomas. Interestingly, the porphyrin and light doses required to induce thromboxane release into serum were also required to evoke vascular stasis and tumor destruction. Nuclear magnetic resonance imaging has been shown to be useful in monitoring the in vivo effects of PDT (Dodd et al., 1989; Moore et al., 1989). NMR spectroscopy (31Pand 2H) has also been used to examine tumor metabolism and blood flow in the RIF-1 tumor model following porphyrin mediated PDT (Mattiello et al., 1990). In situ fluorine NMR indicates that damage to the tumor vasculature following PDT occurs prior to the development of tumor necrosis (Ceckler et al., 1990). Metabolic responses of a transplanted mammary carcinoma in C3H mice (using 3'P-NMR and pH electrodes) indicate that early changes (i.e. 4 h) in tumors following porphyrin mediated PDT are dose dependent and may predict biological outcome (Chopp et al., 1990b). Exposure of normal mouse brain to HPD mediated PDT via non-surgical transscalp illumination induces damage in the form of edema, ischemia and coagulative necrosis is produced (Stroop et al., 1989). The authors suggest that the initial brain damage induced by PDT is associated with the vascular endothelial cell since porphyrins do not readily cross the intact blood-brain barrier. However, slightly different conclusions were obtained when metabolic responses of normal rat brains exposed to PDT were studied by in vivo 31PNMR spectroscopy (Chopp et al., 1990a). Alterations in nucleotide triphosphate to inorganic phosphate ratios as well as changes in pH could be detected. The 31P-NMRdata suggest that PDT damage to brain is not solely the result of microvasculature occlusion and ischemic necrosis. Similar 31PNMR data has been reported in the R3230AC rat mammary carcinoma at 24 h following Photofrin I1 mediated PDT (Gibson et al., 1989a). Interestingly, intracranial and subcutaneously growing tumors in mice respond differently to tetrahydroxyphenyl porphyrin mediated PDT (Lindsay et al., 1991). Subcutaneous lesions are sensitive to PDT while the intracranial lesions of the same tumor are resistant. The resistance is not associated with tumor drug levels but enhanced intracranial PDT responses are observed when animals breathed 100% oxygen. Simultaneous treatment of murine tumors to PDT and hyperthermia has been reported using a continuous wave Nd:YAG laser emitting light at 1060 nm as the source of hyperthermia and an argon ion pumped dye laser as the source of 630 nm light (Mang, 1990). Mammary carcinomas transplanted

Yearly Review

in D B A mice were treated with either PDT alone ( 5 mg/kg Photofrin 11, 135 Jicm'), hyperthermia alone (44SoC, 30 min), or a combination of both modalities. A synergistic response is observed when the two treatments are delivered simultaneously. Interestingly, light used to active the photosensitizer (630 nm) and light used to produce in vivo hyperthermia (1060 nm) can be delivered through the same quartz fiber. The combination of P D T and microwave generated hyperthermia has also been shown to be effective in a mouse tumor model (Matsumoto et al., 1990). In vivo interactions of combined modality therapy using interstitial applications of ionizing radiation, hyperthermia and P D T has been examined by Levendag et al. (1989). A rat tumor model system has been described in which quantititative tumor measurements can be analyzed after the various interstitial treatments. The effect of combined ionizing radiation and meso-tetra-sulphonatophenyl porphine mediated photosensitization has been examined using a mouse tail necrosis assay (Benstead and Moore, 1990). A small tolerance dose of either P D T or ionizing radiation produced an increase in the necrosis rate to the other modality. The potential usefulness of Photofrin I1 mediated PDT for the treatment of endometrial disorders was evaluated by autotransplantation of endometrial tissue in rabbits (Manyak et al., 1989). Complete endometrial epithelial destruction (evaluated histopathologically) was observed in a large percentage of animals treated with clinically relevant doses of PDT. Photofrin I1 induced photosensitization has also been evaluated by Chazen et al. (1991) following treatment of the abdomen of Fischer rats. Differential sensitivity was observed for lesions induced in the gut, skin and abdominal wall. Gut lesions are consistently more severe than either skin and abdominal wall injuries with the gut producing transmural hemorrhagic necrosis while only edema is observed in comparably treated skin and abdominal wall. Colorectal malignancies are theoretically ideal candidates for PDT. Preclinical analysis using aluminium sulfonated P C photosensitization demonstrate selective destruction of malignant tissue while sparing normal colon damage (Barr et al., 1989, 1990a, b). The use of two photosensitizers (Photofrin I1 and meso-tetra-4-sulfonatophenyl-porphine)have been shown to enhance tumoricidal action when compared to the use of individual photosensitizers (Nelson et al., 1990). Pathologic evidence suggested primary damage to the tumor vasculature for all combinations of treatments and therefore the synergistic action obtained for the two photosensitizers and two wavelengths of delivered light is not the result of different mechanisms of action. Chloroaluminum sulfonated PC has been used in the treatment of experimental intraocular Greene's melanoma transplanted to the iris of New Zealand

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albino rabbits (Panagopoulos et al., 1989). Vascular occlusion was produced in a well circumscribed area of laser illumination and the PC mediated photosensitization induced a strong toxic effect on both tumor and normal ocular tissue. Bacteriochlorin A has an absorption band at 760 nm and this compound has preferential retention in anterior chamber Greene's melanoma grown in the rabbit eye (Schuitmaker et al., 1990). Fluorescein angiography performed following tumor treatment demonstrated non-perfusion of treated tumor. Roberts et al. (1991) have utilized chloro-aluminum sulfonated P C to treat spontaneously arising tumors in pets. The positive initial tumor response rates together with the lack of skin photosensitivity are encouragements for additional veterinary studies and future human evaluation. Attempts have been made to measure '02luminescence during Photofrin I1 and chloroaluminum sulfonated PC mediated P D T in cell suspensions and in mouse tumors (Patterson et al., 1990a). Unfortunately, '02luminescence emission could not be detected under conditions in which PDT mediated cell killing and tumor necrosis were produced. The reduction in the lifetime of lo2in the cellular environment (estimated to be less than 0.5 ys) may contribute to the negative results. Photodegradation of porphyrins in cells was used to estimate the life time of '02(Moan and Berg, 1991). The diffusion distance of singlet oxygen was estimated to be 0.01-0.02 y m which corresponded to a '02life time in cells of 0.01-0.04 ys. The diffusion length of singlet oxygen in cells and tissues generated by porphyrin mediated photodynamic action has been estimated to be equal to o r less than 0.07 p m (Moan, 1990). Since the radius of a mammalian cell nucleus is approx. 5 p m , it is unlikely that photosensitizers located in the cytosol or in the plasma membrane will initiate nuclear damage via a '02mechanism. The continued need for information related to P D T dosimetry has led Patterson et al. (1990b) to examine the concept of a PDT threshold dose. I n vivo analysis of the threshold for aluminum chlorosulphonated PC induced P D T in liver tissue was defined by the product of photon fluence, photosensitizer concentration and specific absorption coefficient. The extent of liver tissue necrosis caused by PDT was found to follow the threshold model. Recent P D T dosimetric studies have tested unique multiple cylindrical light sources in both postmortem and in vivo samples (Arnfield et al., 1990). Penetration depths for 630 nm light in the R3227AT rat prostate tumor range from 1.7 to 2.3 mm and the values change during light exposure. Significant variations in light penetration depths in tumors were also observed for 630 nm light during interstitial P D T using cylindrical diffusing fiber tips (Arnfield et al., 1989). A modified cytoscope emitting isotropic light has also been described for in

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vivo monitoring and control of light during bladder PDT (Marynissen et al., 1989). The partial pressure of oxygen has been measured in a transplantable rat chondrosarcoma as a function of time after Photofrin I1 mediated PDT (Reed et al., 1989a). The tumor POz was significantly reduced following PDT and the decrease was greatest in the superficial layer of the tumor. The gradient in POz appears to reflect alterations in blood flow and the data imply that PDT effectiveness in producing tumor hypoxia is dependent on damage to the microcirculation in the peripheral areas of the tumor and not in the tumor interior. I n vivo television microscopy of normal urinary bladder microcirculation following Photofrin I1 mediated PDT indicates that normal rat bladder tissue treated more than 48 h after drug adminisration is due to direct effects on the smooth muscle layer of the bladder rather than on effects to the microcirculation (Reed et al., 1989b). The reduction in blood flow that is observed following PDT can be inhibited by indomethacin and acetyl salicyclic acid, suggesting a possible role of cyclooxygenase products such as prostaglandins andlor thromboxane A2 (Reed et al., 1989~).Interestingly, vascular effects of PDT to normal rat cremaster muscle and transplanted chondrosarcoma were similar (Reed et al., 1989d). Photodynamic action of HPD and chloroaluminum sulfonated PC on the functional capacities of macrophages and natural killer cells has been evaluated by Marshall et al. (1989). The activity of macrophages remained normal even though they accumulated significant quantities of photosensitizer. However, PC mediated photodynamic action did decrease natural killer cell activity. Photofrin I1 mediated PDT response of subcutaneously transplanted mouse mammary tumors was enhanced by administration of recombinant human tumor necrosis factor (Bellnier, 1991). Interestingly, administration of tumor necrosis factor did not significantly potentiate the cutaneous phototoxicity induced by PDT. Cytokines such as gamma interferon, interleukin, interleukin 2 and tumor necrosis factor were assayed in the urine of patients undergoing PDT for bladder cancer (Nseyo et al., 1990). Quantifiable levels of all cytokines except gamma interferon were found in patients receiving the highest PDT doses but not in control patients or those receiving the lowest doses of PDT. HPD mediated PDT combined with Corynebacterium parvum (CP) immunotherapy has been examined in a mouse tumor model by Myers et al. (1989). Low dose intratumor CP (25 pg) stimulates immune cells such as phagocytes and natural killer cells and enhances the effect of PDT in a transitional cell carcinoma subcutaneously transplanted in C3H mice. Summary Numerous photosensitizers with absorption peaks spanning the 600-800 nm “therapeutic window”

have been and continue to be synthesized. Structural modifications of the dyes can then be made in order to improve tumor deliverability and retention. Chemical alterations can also enhance the yields of light generated reactive oxygen species. Utilization of lipoproteins, emulsions and antibody conjugates can enhance the selectivity of drug localization. Most cell types and subcellular structures are highly photosensitive and biochemical analysis indicates that cellular target sites associated with PDT correlate with photosensitizer location. In vivo data suggest that vascular and direct tumor cell damage as well as systemic and local immunological reactions are involved in PDT responsiveness. Additional mechanistic, synthetic and developmental studies are required in order to fully appreciate the potentials of PDT. However, continued enthusiasm and support for basic PDT research (as observed during the past 8 years) will depend to a large extent on the outcome of the current clinical trials. Acknowledgements-Support during the preparation of this review has been provided in part by USPHS Grants R37-CA-31230 and R01-CA-52997 awarded by the National Cancer Institute, Department of Health and Human Resources.

CHARLES J. GOMER Clayton Ocular Oncology Center Childrens Hospital of Los Angeles; and Departments of Pediatrics, Radiation Oncology, and Molecular Pharmacology & Toxicology University of Southern California Los Angeles, C A 90027 USA REFERENCES

Abramson, A. L. A. (1990) Vapor laser photodynamic therapy on the larynx. Arch. Otularyngol. Head Neck Surg. 116, 687-691. Agarwal, R., M. Athar, S. A. Urban, D. R. Bickers and H. Mukhtar (1991) Involvement of singlet oxygen in chloroaluminum phthalocyanine tetrasulfonate mediated photoenhancement of lipid peroxidation in rat epidermal microsomes. Cancer Lett. 56, 125-129. Andreoni, A. and R . Cubeddu (Eds) (1984) Porphyrins in Tumor Photutherapy. Plenum Press, New York. Arnfield, M. R., J . Tulip, M. Chetner and M. S. McPhee (1989) Optical dosimetry for interstitial photodynamic therapy. Med. Phys. 16, 602-608. Amfield, M. R., J. Tulip and M. S. McPhee (1990) Photodynamic therapy dosimetry in postmortem and in vivo rat tumors and an optical phantom. Photochem. Photobid. 51, 667-674. Artuc, M., M. Ramshad and H. Kappus (1989) Studies on acute toxic effects to keratinocytes induced by hematoporphyrin derivatives and laser light. Arch. Dermatol. Res. 281, 491-494. Athar, M., C. A. Elmets, D. R. Bickers and H. Mukhtar (1989) A novel mechanism for the generation of superoxide anions in hematoporphyrin derivative-mediated cutaneous photosensitization. Activation of the Xanthine Oxidase Pathway. J. Clin. Invest. 83, 1137-1143. Bachor, R., C. R. Shea, R. Gillies and T. Hasan (1991) Photosensitized destruction of human bladder carcinoma cells treated with chlorin e6 conjugated micro-

Yearly Review spheres. Proc. Natl. Acad. Sci. USA 88, 1580-1584. Backowski, G. J., T. J. Pintar and A. W. Girotti (1991) Photosensitized lipid peroxidation and enzyme inactivation by membrane-bound merocyanine 540: reaction mechanisms in the absence and presence of ascorbate. Photochem. Photobiol. 53, 481-491. Barber, D . C., K. R. van der Meid, S. L. Gibson, R. Hilf and D. G . Whitten (1991) Photosensitizing activities of picket fence porphyrins in vitro and in vivo. Cancer Res. 51, 1836-1845. Barr, H., S. G . Bown, N. Krasner and P. B. Boulos (1989) Photodynamic therapy for colorectal disease. Int. J . Colorect. Dis. 4, 15-19. Barr, H., N. Krasner, P. B. Boulos, P. Chatlani and S. G. Bown (19YOa) Photodynamic therapy for colorectal cancer: a quantitative pilot study. Br. J . Surg. 77,93-96. Barr, H., C . J. Tralau, P. B. Boulos, A. J. MacRobert, N. Krasner, D . Phillips and S. G. Bown (1990b) Selective necrosis in dimethylhydrazine-induced rat colon tumors using phthalocyaninc photodynamic therapy. Gastroenferology 98, 1532-1537. Barrett, A. J . , J . C. Kennedy, R. A. Jones, P. Nadeau and R. H. Pottier (1990) The effect of tissue and cellular pH on the selective biodistribution of porphyrin-type photochemotherapeutic agents: A volumetric titration study. J . Photochem. Photobiol. 6 , 309-323. Bedwell, J., J . Holton, D. Vaira, A. J. MacRobert and S. G. Bown (1990) In vitro killing of Helicobacteria pylori with photodynamic therapy [letter]. Lancet 335, 1287. Bellnier, D. A. (1991) Potentiation of photodynamic therapy in mice with recombinant human tumor necrosis factor-alpha. J . Phofochem. Photobiol. 8, 203-210. Bellnier, D. A . and T. J . Dougherty (1989a) Protection of murine foot tissue and transplantable tumor against Photofrin-11-mediated photodynamic sensitization with WR-2721. J . Photochem. Photobiol. 4, :219-225. Bellnier, D. A. and T. J. Dougherty (1989b) The time course of cutaneous porphyrin photosensitization in the murine ear. Photochem. Photobid. 49, 221-228. Bellnier, D. A , , Y-K. Ho, R. K. Pandey, J. R. Missert and T. J . Dougherty (1989~)Distribution and elimination of Photofrin I1 in mice. Photochem. Photobiol. 50, 221-228. Benstead, K. and J. V. Moore (1990) The effect of combined modality treatment with ionizing radiation and TPPS-mediated photodynamic therapy on murine tail skin. Br. J . Cancer 62, 48-53, Berg, K., J . C. Bommer and J . Moan (1989) Evaluation of sulfonated aluminum phthalocyanines for use in photochemotherapy. A study on the relative efficiencies of photoinactivation. Photochem. Photobiol. 49, 587-594. Bertoloni, G . , F. Rossi, G. Valduga, G. Jori and J. van Lier (1990) Photosensitizing activity of water and lipid soluble phthalocyanines on E coli. FE'MS Microbiol. Lett. 71, 149-156. Boegheim, J. P. J . , J . W. M. Lagerberg, T. M. A. R. Dubbelman and J. Van Steveninck (1989a) Damaging action of photodynamic treatment in combination with hyperthermia on transmembrane transport in murine L929 fibroblasts. Biochim. Biophys. Acta 979, 215-220. Boegheim, J . P., J . W. Lagerberg, K. Tijssen, T. M. Dubbelman and J. van Steveninck (1989b) Preferential uptake of cytotoxic porphyrins from hematoporphyrin derivative in murine L929 fibroblasts and Chinese hamster ovary K1 epithelial cells. Biochim. Biophys. Acta 1012, 237-242. Bonnett, R., R. D. White, U-J. Winfield and M. C. Berenbaum (1989) Hydroporphyrins of the mesotetra(hydroxypheny1)porphyrin series as tumor photosensitizers. Biochem. J . 261, 277-280. Brand, E., H-S. Choi, G. D. Braunstein, IN. S. Grundfest

1103

and L. D. Lagasse (1989) Photodynamic therapy of human choriocarcinoma transplanted to the hamster cheek pouch. Cynecol. Oncol. 34, 289-293. Brand, E., H . S . Choi, K. Karalis, T. Papaioannou, M. C. Fishbein, G. Braunstein, M. E . Wade, L. D. Lagasse and W. S. Grundfest (1990) Photodynamic therapy of choriocarcinoma transplanted to the hamster cheek pouch. I. Intraperitoneal photosensitization. Cynecol. Oncol. 36, 200-206. Candide, C., J. C. Maziere, R. Santus, C. Maziere, P. Morliere, J . P. Reyftmann, S. Goldstein and L. Dubertret (1989) Photosensitization of Wi26-VA4 transformed human fibroblasts by low density lipoprotein loaded with the anticancer porphyrin mixture Photofrin 11: evidence for endoplasmic reticulum alteration. Cancer Lett. 44, 157-161. Ceckler, T. L., S. L. Gibson, R. Hilf and R. G. Bryant (1990) In situ assessment of tumor vascularity using fluorine NMR imaging. Magn. Reson. Med. 13, 416-433. Chan, W-S, J. F. Marshall, R. Svensen, J . Bedwell and I. R. Hart (1990) Effect of sulfonation on the cell and tissue distribution of the photosensitizer aluminum phthalocyanine. Cancer Res 50, 4533-4538. Chazen, M. D., R. B. Baggs, S. L. Gibson, M. S . Albert and R. Hilf (1991) Gross and microscopic changes in the viscera induced by photodynamic therapy applied to the lower abdomen of intact rats. Laser Surg. Med. 11, 43-50. Chopp, M., C-Q. Dereski and H. W. Hetzel (1990a) Chronic metabolic measurements of normal brain tissue response to photodynamic therapy. Photochem. Photobiol. 52, 1033-1036. Chopp, M., F. W. Hetzel and Q. Jiang (1990b) Dosedependent metabolic response of mammary carcinoma to photodynamic therapy. Radiat. Re.?. 121, 288-294. Cowled, P. A . and I. J. Forbes (1989) Modification by vasoactive drugs of tumor destruction by photodynamic therapy with hematoporphyrin derivative. Br. J . Cancer 59, 904-909. Croisy, A,, D . Carrez and D. Zilberfarb (1990) A practical test for in vitro evaluation of photosensitization: Assessment with hematoporphyrin derivative (HPD). Cytotechnology 3, 171-178. Cuomo, V., G. Jori, B. Rihter, M. E. Kenney and M. A. J. Rodgers (1990) Liposome delivered Si(1V) naphthalocyanine as a photodynamic sensitizer for experimental tumors: pharmacokinetic and phototherapeutic studies. Br. J . Cancer 62, 966-970. Dartsch, P. C., T. Ischinger and E . Betz (1990) Responses of cultured smooth muscle cells from human nonatherosclerotic arteries and primary stenosing lesions after photoradiation: Implications for photodynamic therapy of vascular stenosis. J . A m . Coll. Cardiol. 15, 1545-1550. Dereski, M. O . , M. Chopp, Q. Chen and F. W. Hetzel (1989) Normal brain tissue response to photodynamic therapy: histology, vascular permeability and specific gravity. Photochem. Photobiol. 50, 653-657. Detty, M. R . , P. B. Merkel, R. Hilf. S. L. Gibson and S. K. Powers (1990) Chalcogenapyrylium dyes as photochemotherapeutic agents. 2. Tumor uptake, mitochondrial targeting, and singlet-oxygen-induced inhibition of cytochrome c oxidase. J . Med. Chem. 33, 1101(-1116. Devanathan, S., T. A. Dahl, W. R. Midden and D. C. Neckers (1990) Readily available fluorescein isothiocyanate-conjugated antibodies can be easily converted into targeted phototoxic agents for antibacterial, antiviral, and anticancer therapy. Proc. Natl. Acud. Sci. USA 87, 2980-2984. Dodd, N . J. F., J. V. Moore, D. G. Poppitt and B. Wood (1989) In vivo magnetic resonance imaging of the effects of photodynamic therapy. Br. J . Cuncer 60, 164-167.

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CHARLES J. GOMER

Doiron, D. R. and C. J. Gomer (Eds) (1984) Porphyrin Localization and Treatment of Tumors. Alan R. Liss, New York. Dougherty, T. J . (1987) Photosensitizers: therapy and detection of malignant tumors. Photochem. Photobiol. 45, 879-889. Dougherty, T. J. (1989) Photodynamic therapy-New approaches. Semin. Surg. Oncol. 5 , 6 1 6 . Dougherty, T. J. and W. R. Potter (1991) Of what value is a highly absorbing photosensitizer in PDT? J . Photochem. Photobiol. 8, 223-225. Evans, S., W. Matthews, R. Perry, D. Fraker, J . Norton and H. I. Pass (1990) Effect of photodynamic therapy on tumor necrosis factor production by murine macrophages. J . Nail. Cancer Inst. 82, 34-39. Evans, H. H., R. M. Rerko, J . Mencl, M. E . Clay, A. R. Antunez and N. L. Oleinick (1989) Cytotoxic and mutagenic effects of the photodynamic action of chloroaluminum phthalocyanine and visible light in L5178Y cells. Photochem. Photobiol. 49, 43-47. Ferrario, A. and C. J . Gomer (1990) Systemic toxicity in mice induced by localized porphyrin photodynamic therapy. Cancer Res. 50, 539543. Fingar, V. H., T. J. Wieman and K. W. Doak (1990) Role of thromboxane and prostacyclin release on photodynamic therapy-induced tumor destruction. Cancer Res. 50, 25992603. Foultier, M-T., T. Patrice. V. Praloran, N. Robillard and L. Le Bodic (1989) Influence of hematoporphyrin derivative concentration, incubation time, temperature during incubation and laser dose fractionation on photosensitivity of normal hematopoietic progenitors or leukemia cells. Biochimie 71, 819-825. Gaffney, D. K., S. L. Schober and F. Sieber (1990) Merocyanine 540-sensitized photoinactivation of leukemia cells: Role of oxygen and effects on plasma membrane integrity and mitochondria1 respiration. Exp. Hematol. 18, 23-26. Gaffney, D. K. and F. Sieber (1990) Merocyanine 540sensitized photoinactivation of soluble and membranebound enzymes in L1210 leukemia cells. Cancer Res. 50, 11657769. Gaspard, S., P. Margaron. C. Tempete and T. H. T. Thi (1990) Mixed acenannellated metallotetraazaporphins: a new class of amphiphilic photosensitizers for the photodynamic therapy of cancer. J . Photochem. Photobiol. 4, 419-423. Gibson, S. L., T. L. Ceckler, T. G. Bryant and R. Hilf (1989a) Effects of laser photodynamic therapy on tumor phosphate levels and pH assessed by 31P-NMR spectroscopy. Cancer Biochem. Biophys. 10, 319-328. Gibson, S. L., R. S. Murant, M. D. Chazen, M. E. Kelly and R. Hilf (1989b) In vitro photosensitization of tumor cell enzymes by Photofrin 11 administered in vivo. Br. J . Cancer 59, 41-53. Gibson, S. L., K. R . Van Der Meid, R. S. Murant and R. Hilf (1990) Increased efficacy of photodynamic therapy of R3230AC mammary adenocarcinoma by intratumor injection of Photofrin 11. Br. J . Cancer 61, 553-557. Ginevra, F., S. Biffanti, A. Pagnan, R. Biolo, E. Reddi and G. Jori (1990) Delivery of the tumor photosensitizer zinc (11) phthalocyanine to serum proteins by different liposomes: studies in-vitro and in-vivo. Cancer Lett. 49, 59-65. Girotti, A. W. (1990) Photodynamic lipid peroxidation in biological systems. Photochem. Photobiol. 51, 497-509. Glassberg, E. , L. Lewandowski, G. Lask and J. Uitto (1990) Laser-induced photodynamic therapy with aluminium phthalocyanine tetrasulfonated as the photosensitizer: differential phototoxicity and malignant human cells in vitro. J . Invest. Dermatol. 94, 604-610. Glover, R. A,, C. S. Bailey, K. E. Barrett, S. I . Wasser-

man and I. Gigli (1990) Histamine release from rodent and human mast cells induced by protoporphyrin and ultraviolet light: studies of the mechanism of mast-cell activation in erythropoietic protoporphyria. Br. J . Dermatol. 122, 501-512. Gomer, C. J . (Ed.) (1987) Photodynamic Therapy. Pergamon Press, New York. Gomer, C. J. (1989) Photodynamic therapy in the treatment of malignancies. Semin Hematol. 26, 27-34. Gomer, C. J. (Ed.) (1990) New Directions in Photodynamic Therapy. SPIE Press, Bellingham, WA. Gomer, C. J. and A. Ferrario (1990) Tissue distribution and photosensitizing properties in mono-1-aspartyl chlorin e6 in a mouse tumor model. Cancer Res. 50, 3985-3990. Gomer, C. J., M. Luna, A. Ferrario and N. Rucker (1991) Increased transcription and translation of heme oxygenase in Chinese hamster fibroblasts following photodynamic stress or Photofrin I1 incubation. Photochem. Photobiol. 53, 275-219. Gomer, C. J., N. Rucker, A . Ferrario and S. Wong (1989) Properties and applications of photodynamic therapy. Radiat. Res. 120, 1-18. Gomer, C. J., N. Rucker and S. Wong (1990) Porphyrin photosensitivity in cell lines expressing a heat-resistant phenotype. Cancer Res. 50, 5365-5368. Gulliya, K. S. and S. Pervaiz (1989) Elimination of clonogenic tumor cells from HL-60, daudi, and U-931 cell lines by laser photoradiation therapy: implications for autologous bone marrow purging. Blood 73, 1059-1065. Hartley, J . A , , S. M. Forrow, R. L. Souhami, K. Reszka and J . W. Lown (1990) Photosensitization of human leukemic cells by anthracenedione antitumor agents. Cancer Res. 50, 19361940. Haseloff, R. F. and B. Ebert (1989) Generation of free radicals by photoexcitation of pheophorbide a, hematoporphyrin and protoporphyrin. J . Photochem. Photobiol. 3, 593-602. Hayden, R. E., P. W. McLear, A. R. Morgan and J. K. Bischoff (1990) Verdins in photodynamic therapy of squamous cell carcinoma. A m . J . Otolaryngol. 11, 125-130. He, D., N. A. Soter and H. W. Lim (1989) The late phase of hematoporphyrin derivative-induced phototoxicity in mice: release of histamine and histologic changes. Photochem. Photobiol. 50, 91-95. Henderson, B. W. (1989) Photodynamic therapy--coming of age. Photodermatology 6, 200-211. Henderson, B. W. and J . M. Donovan (1989) Release of prostaglandin E, from cells by photodynamic treatment in vitro. Cancer Res. 49, 68964900. Henderson, B. W. and V. H . Fingar (1989) Oxygen limitation of direct tumor cell kill during photodynamic treatment of a murine tumor model. Photochem. Photobid. 49, 299-304. Jamieson, C. H., W. N. McDonald and J. G. Levy (1990) Preferential uptake of benzoporphyrin derivative by leukemia versus normal cells. Leuk. Res. 14, 209219. Jori, G. (1990) Photosensitized processes in-vivo: proposed phototherapeutic applications. Photochem. Photobiol. 52, 439-443. Jori, G. and C. Perria (Eds.) (1985) Photodynamic Therapy of Tumor and Other Diseases. Edizioni Libreria Progetto, Padova. Keller, S. M., D. D. Taylor and J. L. Wecse (1990) In vitro killing of human malignant mesothelioma by photodynamic therapy. J . Surg. Res. 48, 337-340. Kessel, D. (1984) Hematoporphyrin and HPD: photophysics, photochemistry and phototherapy. Photochem. Photobiol. 39, 851-859. Kessel, D. (Ed.) (1985) Methods in Porphyrin Photosensitization. Plenum Press, New York. Kessel, D. (1989a) Determinants of photosensitization by

Yearly Review mono-I-aspartyl chlorin e6. Photochem. Photobiol. 49, 447- 452. Kessel, D. (1989b) In vitro photosensitization with a benzoporphyrin derivative. Photochem. Photobiol. 49, 579-582. Kessel, D. (1989~)Determinants of photosensitization by purpurins. Photochem. Photobiol. 50, 169-174. Kessel, D. (Ed.) (1990) Photodynamic Therapy of Neoplastic Disease, Vols. I & 11. CRC Press, Boston, MA. Kessel, D., C. J. Byrne and A. D . Ward (1991a) Photophysical and photobiological properties of diporphyrin ethers. Photochem. Photobiol. 53, 469-474. Kessel, D. and J. Dougherty (Eds) (1983) Porphyrin Photosensitization. Plenum Press, New York. Kessel, D., T. J. Dougherty and C. K. Chang (1991b) Photosensitization by synthetic diporphyrins and dichlorins in-vivo and in-vitro. Photochem. Photobiol. 53, 475-479. Kol, R., E. Ben-Hur, R. Marko and I. Rosenthal (1989) Inhibition of human lymphocyte stimulation by visible light and phthalocyanine photosensitization: mitogen and wavelength dependency. lnt. J . Radiat. Biol. 55, 1015-1022. Korbelik, M. and J. Hung (1991) Cellular delivery and retention of Photofrin 11: the effects of interaction with human plasma proteins. Photochem. Photobiol. 53, 501-510. Korbelik, M., G. Krosl and D. J. Chaplin (1991) Photofrin uptake by murine macrophages. Cancer Res. 51, 2251-2255. Krutmann, J., M. Athar, D. B. Mendel, I. U. Khan, P. M. Guyre, H . Mukhtar and C. A. Elmets (1989) Inhibition of the high affinity Fc receptor (Fc: RI) on human monocytes by porphyrin photosensitization is highly specific and mediated by the generation of superoxide radicals. J . Biol. Chem. 264, 11407-11413. Levendag, P. C., A. C. C. Ruifrok, J. P. ,4. Marijnissen, W. L. J. van Putten and A. G. Visser (1989) Preliminary experience with interstitial radiation, interstitial hyperthermia and interstitial photodynamic therapy in a simple animal model. Sirahlenther. Onkol. 165, 56-60. Leznoff, C. C., S. Vigh, P. I. Svirskaya, S. Greenberg, D. M. Drew, E . Ben-Hur and I. Rosenthal (1989) Synthesis and photosensitivity of some new substituted phthalocyanines. Photochem. Photobiol. 49, 279-284. Lin, C. W . , J. R. Shulok, Y . K. Wong, C. F. Schanbacher and L. Cincotta (1991) Photosensitization, uptake, and retention of phenoxazine Nile blue derivatives in human bladder carcinoma cells. Cancer Res. 51, 1109-1116. Lindsay, E. A,, M. C. Berenbaum, R. Bonnett and D. G. Thomas (1991) Photodynamic therapy of a mouse glioma: intracranial tumours resistant while subcutaneous tumours are sensitive. Br. J . Cancer 63, 242-246. Malik, Z . , B. Ehrenberg and A. Faraggi (1989) Inactivation of erythrocytic, lymphocytic and myelocytic leukemic cells by photoexcitation of endogenous porphyrins. J . Photochem. Photobiol. 4, 195-205. Malik, Z . , J. Hanania and Y. Nitzan (1990) Bactericidal effects of photoactivated porphyrins--an alternative approach to antimicrobial drugs. J . Photochem. Photobiol. 5, 281-293. Mang, T. S. (1990) Combination studies of hyperthermia induced by neodymium: yttrium-aluminum-garnet (Nd: YAG) laser as an adjuvant to photodynamic therapy. Lasers Surg. Med. 10, 173-178. Manyak, M. J., L. M. Nelson, D . Solomon, A. Russo, G . F. Thomas and R. J. Stillman (1989) Photodynamic therapy of rabbit endometrial transplants: a model for treatment of endometriosis. Fer. Steril. 52, 14G145. Marcus, S. (1990) Photodynamic therapy of human cancer; clinical status, potential and needs. In Future Directions and Applications in Photodynamic Therapy (Edited by

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C. Gomer), pp. 5-56. SPIE Press, Bellingham, WA. Marshall, J . F., W-S. Chan and I. R. Hart (19x9) Effect of photodynamic therapy on anti-tumor immune defenses: Comparison of the photosensitizers hematoporphyrin derivative and chloroaluminum sulfonated phthalocyanine. Photochem. Photobiol. 49, 627-632. Marynissen, J . P., H . Jansen and W. M. Star (1989) Treatment system for whole bladder wall photodynamic therapy with in vivo monitoring and control of light dose rate and dose. J . Urol. 142, 1351-1355. Matsumoto, N., H. Saito, N. Miyoshi, K. Nakanishi and M. Fukuda (1990) Combination effect of hyperthermia and photodynamic therapy on carcinoma. Arch. Otolaryngol. Head Neck Surg. 116, 824-829. Matthews, E . K. and Z . J. Cui (1990) Photodynamic action of sulfonated aluminum phthalocyanine (SALPC) on AR4-2J cells, a carcinoma cell line of rat exocrine pancreas. Br. J . Cancer 61, 695-701. Matthews, W., J . Cook, J. B. Mitchell, R. R. Perry, S. Evans and H. I. Pass (1989b) In vitro photodynamic therapy of human lung cancer: Investigation of doserate effects. Cancer Res. 49, 1718-1721. Matthews, W., W. Rizzoni, J. Mitchell, A. Russo and H. Pass (1989a) In vitro photodynamic therapy of human lung cancer. J . Surg. Res. 47, 176-281. Mattiello, J., J. L. Evelhoch, E. Brown, A. P. Schaap and F. W. Hetzel(1990) Effect of photodynamic therapy on RIF-1 tumor metabolism and blood flow examined by 31P and 2H NMR spectroscopy. NMR Biomed. 3, 64-70. Milanesi, C., F. Sorgato and G. Jori (1989) Photokinetic and ultrastructural studies on porphyrin photosensitization of HeLa cells. lnt. J . Radiat. Biol. 55. 59-69. Milanesi, C., C. Zhou, R. Biolo and G. Jori (1990) Zn(1I)phthalocyanine as a photodynamic agent for tumors. 11. Studies on the mechanism of photosensitized tumor necrosis. Br. J . Cancer 61, 84G350. Moan, J. (1986) Porphyrin photosensitization and phototherapy. Photochem. Photobiol. 43, 681-690. Moan, J. (1990) On the diffusion length of singlet oxygen in cells and tissues. J . Photochem. Photobiol. 6, 343-347. Moan, J., H. Anholt and Q. Peng (1990) A transient reduction of the fluorescene of aluminum phthalocyanine tetrasulphonate in tumors during photodynamic therapy. J . Photochem. Photobiol. 5, 115-1 19. Moan, J. and K. Berg (1991) The photodegradation of porphyrins in cells can be used to estimate the lifetime of singlet oxygen. Photochem. Photobiol. 53, 549-SS3. Modica-Napolitano, J. S . , J. L. Joyal, G. Ara, A. R. Oseroff and J . R. Aprille (1990) Mitochondria1 toxicity of cationic photosensitizers for photochemotherapy. Cancer Res. 50, 78767881. Moore, J. V., N. J. F. Dodd and B. Wood (1989) Proton nuclear magnetic resonance imaging as a predictor of the outcome of photodynamic therapy of tumors. Br. J . Radiol. 62, 869-870. Morgan, A . R., G . M. Garbo, R. W. Keck, L. D. Eriksen and S. H. Selman (1990a) Metallopurpurins and light: effect on transplantable rat bladder tumors and niurine skin. Photochem. Photobiol. 51, 589-592. Morgan, A. R., G. M. Garbo, R. W. Keck, R . A . Miller, S. H . Selman and D. Skalkos (1990b) Diels-Adler adducts of vinyl porphyrins: synthesis and in vivo photodynamic effect against a rat bladder tumor. J . Med. Chem. 33, 1258-1262. Morstyn, G. and A. H. Kaye (Eds.) (1990) Phototherapy of Cancer. Harwood Academic Publishers, New York. Myers, R. C., B. H . S. Lau, D . Y. Kunihira, R. R. Torrey, J . L. Woolley and J. Tosk (1989) Modulation of hematoporphyrin derivative-sensitized phototherapy with corynebacterium parvum in murine transitional cell

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carcinoma. Urology 33, 230-235. Nelson, J. S., L-H. L. Liaw, R. A. Lahlum, P. L. Cooper and M. W. Berns (1990) Use of multiple photosensitizers and wavelengths during photodynamic therapy: A new approach to enhance tumor eradication. J . Natl. Cancer Inst. 82, 868-873. Neyndorff, H. C., D . L. Bartel, F. Tufaro and J . G . Levy (1990) Development of a model to demonstrate photosensitizer-mediated viral inactivation in blood. Transfusion 30, 485-490. Nseyo, U . O., R. K. Whalen, M. R. Duncan, B. Berman and S. L. Lundahl (1990) Urinary cytokinase following photodynamic therapy for bladder cancer. A preliminary report. Urology 36, 167-171. Ohnishi, Y., M. Murakami and H. Wakeyama (1990) Effects of hematoporphyrin derivative and light on Y79 retinoblastoma cells in vitro. Invest. Opktkalmol. Vis. Sci. 31, 792-797. Panagopoulos, J. A,, P. P. Svitra, C. A. Puliafito and E. S. Gragoudas (1989) Photodynamic therapy for experimental intraocular melanoma using chloroaluminum sulfonated phthalocyanine. Arch. Optkalmol. 107, 886890. Pandey, R. K., K. M. Smith and T. J. Dougherty (1990) Porphyrin dimers as photosensitizers in photodynamic therapy. J . Med. Ckem. 33, 2032-2038. Paquette, B., H. Ali, R. Langlois and J. E. van Lier (1990) Biological activities of phthalocyanines-XI. Phototoxicity of sulfonated aluminum naphthalocyanines towards V-79 Chinese hamster cells. Pkotockem. Pkotobiol. 51, 313-317. Patterson, M. S . , S. J. Madsen and B. C. Wilson (1990a) Experimental tests of the feasibility of singlet oxygen luminescence monitoring in vivo during photodynamic therapy. J . Pkotockem. Pkotobiol. 5 , 69-84, Patterson, M. S., B. C . Wilson and R. Graff (1990b) In vivo tests of the concept of photodynamic threshold dose in normal rat liver photosensitized by aluminum chlorosulphonated phthalocyanine. Pkotockem. Pkotobiol. 51, 343-349. Peng, Q., J. Moan, G. 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. Perry, R. R., W. Matthews, J. B. Mitchell, A. Russo, S. Evans and H. I. Pass (1990) Sensitivity of different human lung cancer histologies to photodynamic therapy. Cancer Res. 50, 4272-4276. Pompei, R., G. Cisani, G. Foddis and M. A . Marcialis (1989) Kinetics of herpes simplex virus photoinhibition by hematoporphyrin in both diploid and heteroploid cells. Microbios. 58, 101-1 11. Pope, A . J., J . R. W. Masters and A. J . MacRobert (1990) The photodynamic effect of a pulsed dye laser on human bladder carcinoma cells in vitro. Urol. Res. 18,267-270. Pottier, R. and J . C. Kennedy (1990) The possible role of ionic species in selective biodistribution of photochemotherapeutic agents toward neoplastic tissue. J . Pkotockem. Pkotobiol. 8, 1-16. Powers, S. K., D. L. Walstad, J. T. Brown, M. Detty and P. J. Watkins (1989) Photosensitization of human glioma cells by chalcogenapyrylium dyes. J. Neuro. Oncol. 7, 179-188. Prinsze, C., T. M. A. R. Dubbelman and J . Van Steveninck (1990) Protein damage, induced by small amounts of photodynamically generated singlet oxygen or hydroxyl radicals. Biockim. Biopkys. Acta 1038, 152-157. Raab, G. H., A . F. Schneider, W. Eiermann, H. H. Deponte-Gottschalk, R . Baumgartner and W. Beyer (1990) Response of human endometrium and ovarian carcinoma cell-lines to photodynamic therapy. Arch. Gynecol. Obstet. 248, 13-20.

Rakestraw, S. L., R. G . Tompkins and M. L. Yarmush (1990) Antibody-targeted photolysis: In vitro studies with Sn(1V) chlorin e6 covalently bound to monoclonal antibodies using a modified dextran carrier. Proc. Natl. Acad. Sci. USA 87, 4217-4221. Ramakrishnan, N., N. L. Oleinick, M. E. Clay, M-F. Horng, A. R. Antunez and H. H. Evans (1989) DNA lesions and DNA degradation in mouse lymphoma L5178Y cells after photodynamic treatment sensitized by chloroaluminum phthalocyanine. Pko$ockem. Photobiol. 50, 373-378. Reddi, E., C. Zhou, R. Biolo, E. Menegaldo and G . Jori (1990) Liposome- or LDL-administered Zn (11)phthalocyanine as a photodynamic agent for tumors. I. Pharmacokinetic properties and phototherapeutic efficiency. Br. J . Cancer 61, 407-411. Reed, M. W. R., A . P. Mullins, G. L. Anderson, F. N. Miller and T. J. Wieman (1989a) The effect of photodynamic therapy on tumor oxygenation. Surgery 106, 94-99. Reed, M. W. R . , D . A. Schuschke, D. M. Ackermann, J. I. Harty, T. Jeffrey Wieman and F. N. Miller (1989b) The response of the rate urinary bladder microcirculation to photodynamic therapy. J. Urol. 142, 865-868. Reed, M. W. R., T. J . Wieman, K. W. Doak, C. G. Pietsch and D. A. Schuschke (1989~)The microvascular effects of photodynamic therapy: Evidence for a possible role of cyclooxygenase products. Pkotockem. Pkotobiol. 50, 419-423. Reed, M. W. R., T. J . Wieman, D. A. Schuschke, M. T. Tseng and F. N. Miller (1989d) A comparison of the effects of photodynamic therapy on normal and tumor blood vessels in the rat microcirculation. Radiat. Res. 119, 542-552. Reszka, K., J. A . Hartley and J. W. Lown (1990) Photosensitization by selected anticancer agents. Biopkys. Ckem. 35, 313-323. Richter, A. M., S. Cerruti-Sola, E. D. Sternberg, D. Dolphin and J. G . Levy (1990) Biodistribution of tritiated benzoporphyrin derivative ('H-BPD-MA), a new potent photosensitizer in normal and tumor-bearing mice. J. Pkotockem. Pkotobiol. 5 , 231-244. Richter, A. M., E. Waterfield, A. K. Jain, B. Allison, E. D. Sternberg, D. Dolphin and J . G. Levy (1991) Photosensitizing potency of structural analogues of benzoporphyrin derivative (BPD) in a mouse tumor model. Br. J. Cancer 63, 87-93. Roberts, W. G. and M. W. Berns (1989) In vitro photosensitization I. Cellular uptake and subcellular localization of mono-I-aspartyl chlorin e6, chloroaluminum sulfonated phthalocyanine, and Photofrin 11. Lasers Surg. Med. 9, 90-101. Roberts, W. G.. M. K. Klein, M. Loomis, S. Weldy and M. W. Berns (1991) Photodynamic therapy of spontaneous cancers in felines, canines, and snakes with chloro-aluminum sulfonated phthalocyanine. J . Natl. Inst. Cancer 83, 18-23. Roberts, W. G., K. M. Smith, J. L. McCullough and M. W. Berns (1989) Skin photosensitivity and photodestruction of several potential photodynamic sensitizers. Pkotockem. Pkotobiol. 49, 431-438. Rogers, D. W.. R. J. Lanzafame and J. R. Hinshaw (1991) Effect of argon laser and Photofrin I1 on murine neuroblastoma cells. J . Surg. Res. 50, 266271, Rosenthal, I. (1991) Phthalocyanines as photodynamic sensitizers. Pkotockem. Pkotobiol. 53, 859-870. Salet, C . and G. Moreno (1990) New trends in photobiology: Photosensitization of mitochondria. Molecular and cellular aspects. J . Pkotockem. Pkotobiol. 5 , 133-150. Schuitmaker, J. J., J. A. van Best, J. L. van Delft, T. M. Dubbelman, J. A. Oosterhuis and R. D. deWolff (1990) Bacteriochlorin a, a new photosensitizer in photo-

Yearly Review dynamic therapy. In vivo results. Invesl. Ophthalmol. Vis. Sci. 31, 1444-1450. Selman, S. H . , B. S. Qin, H. R. James, R. W. Keck, G. M. Garbo and A. R. Morgan (1990) Hemodynamic effect of the metallopurpurin SnET2 and light on transplantable FANFT induced bladder tumor. J . Urol. 143, 63(&633. Shea, C. R., Y. Hefetz, R. Gillies, J . Wimberly, G. Dalickas and T. Hasan (1990) Mechanistic investigation of doxycycline photosensitization by picosecond-pulsed and continuous wave laser irradiation of cells in culture. J . Biol. Chem. 265, 5977-5982. Shikowitz, M. J . , R. Galli, D. Bandyopadhyay and S. Hoory (1989) Biodistribution of Indium 111-labeled dihematoporphyrin ether in papillomas and body tissues. Arch. Otoluryrigol. Head Neck Surg. 115,845-847. Shulok, J . R., M. H. Wade and C. W. Lin (1990) Subcellular localization of hematoporphyrin derivative in bladder tumor cells. Photochem. Photobiol. 51, 451-457. Sieber, F. (1987) Merocyanine. Photochem. Photobiol. 46, 1035-1 042. Sieber, F., G . J. Krueger, J . M. O’Brien, S. L. Schober, L. L. Sensenbrenner and S. J . Sharkis (1989) Inactivation of Friend erythroleukemia virus and friend virustransformed cells by merocyanine 540-mediated photosensitization. Blood 73, 345-350. Singh, R. J., J. B. Feix, T. J. Pintar, A. W. Girotti and B. Kalyanaraman (1991) Photodynamic action of merocyanine 540 in artificial bilayers and natural membranes: action spectra and quantum yields. Photochem. Photobiol. 53, 493-450. Specht, K. G. and M. A. J. Rodgers (1990) Depolarization of mouse myeloma cell membranes during photodynamic action. Photochem. Photobiol. 51, 319-324. Spikes, J. D . (1986) Phthalocyanines as photosensitizers in biological systems and for photodynamic therapy of tumors. Photochem. Photobiol. 43, 691-700. Spikes, J . D. (1990) New trends in photobiology (invited review) chlorins as photosensitizers in biology and medicine. J . Photochem. Photobiol. 6, 259-2:74. Stroop, W. G., E-J. M. M. Battles, J . J. Townsend, D. C. Schaefer, J. R. Baringer and R. C. Straight (1989) Porphyrin-laser photodynamic introduction of focal brain necrosis. J . Neuropathol. Exp. Neurol. 48, 548-559. Thomas, J . P., P. G. Geiger, D. K. Gaffney and A . W. Girotti (1989) Photooxidation of membrane phospholipids and cholesterol in merocyanine 540-sensitized leukemia cells. Photochem. Photobiol. 49, 68-74. Thomas, J . P. and A. W. Girotti (1989a) Role of lipid peroxidation in hematoporphyrin derivative-sensitized photokilling of tumors cells: protective effects of glutathione peroxidase. Cancer Rex 49, 168:!-1686. Thomas, J. P. and A. W. Girotti (1989b) Glucose adminis-

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tration augments in vivo uptake and phototoxicity of the tumor-localizing fraction of hematoporphyrin derivative. Photochem. Photobiol. 49, 241-247. Tralau, C. J . , A. R. Young, N. P. J . Walker, D. I. Vernon, A. J. MacRobert, S. B. Brown and S . G . Bown (1989) Mouse skin photosensitivity with dihematoporphyrin ether (DHE) and aluminum sulfonated phthalocyanine (AISPc): a comparative study. Phorochem. Photobiol. 49, 305-312. Varnes, M. E., M. E. Clay, K. Freeman, A. R. Antunez and N. L. Oleinick (1990) Enhancement of photodynamic cell killing (with chloroaluminum phthalocyanine by treatment of V79 cells with the ionophore nigericin. Cuncer Res. 50, 1620-1625. West, C. M. L. (1989) Size-dependent resistance of human tumor spheroids to photodynamic treatment. Br. J . Cuncer 59, 510-514. West, C. M. L. and J. V. Moore (1989) The photodynamic effects of Photofrin 11, hematoporphyrin derivative, hematoporphyrin, and tetrasodium-mesotetra(4-sulfonatopheny1)porphine in vifro: clonogenic cell survival and drug uptake studies. Photochem. Photobiol. 49, 169-1 74. West, C . M. L., D. C. West, S. Kumar and J . V. Moore (1990) A comparison of the sensitivity to photodynamic treatment of endothelial and tumor cells in different proliferative states. Int. J . Radiaf. Biol. 58, 145-156. Winther, J . (1989a) Effect of Photofrin I1 and light energy on retinoblastoma-like cells in vitro. J . Cancer Res. Clin. Oncol. 115, 73-78. Winther, J. (1989b) Photodynamic therapy effect in an intraocular retinoblastoma-like tumor assessed by an in vivo to in vitro colony forming assay. Br. J . Cancer 59, 869-872. Winther, J . and J . Overgard (1989) Photodynamic therapy of experimental intraocular retinoblastomadoseresponse relationships to light energy and Photofrin 11. Acta Ophthalmol. 67, 44-50. Yates, N. C., J. Moan and A. Western (1990) Waterphotosoluble metal naphthalocyanines-near-IR sensitizers: cellular uptake, toxicity and photosensitizing properties in NHIK 3025 human cancer cells. J . Photochem. Photobiol. 4, 379-390. Yu, D-S., S-Y. Chang and C-P. Ma (1990) Photoinactivation of bladder tumor cells by methylene blue: Study of a variety of tumor and normal cells. J . Urol. 144, 164- 168. Zdolsek, J . M., G. M. Olsson and U . T. Brunk (1990) Photooxidative damage to lysosomes of cultured macrophages by acridine orange. Photochem. Photobiol. 51, 67-76. Zhou, C. (1989) Mechanisms of tumor necrosis induced by photodynamic therapy. J . Photochem. Photobiol. 3, 299-318.

New photodynamic therapy with next-generation photosensitizers.

New photosensitizers for photodynamic therapy.

Porphyrin dimers as photosensitizers in photodynamic therapy.

Research and development of photodynamic therapy photosensitizers in China.

Research and development of photodynamic therapy photosensitizers in China.

Photodynamic therapy using a second generation photosensitizer, Talaporfin.

Physicochemical properties of potential porphyrin photosensitizers for photodynamic therapy.

Fullerene Nanoparticle Photosensitizers.

Comparison of photosensitizers in saline and liposomes for tumor photodynamic therapy and skin phototoxicity.

Effect of photosensitizers in chemical and biological processes: the MTO mechanism in photodynamic therapy.

Hiporfin-mediated photodynamic therapy in preclinical treatment of osteosarcoma.

Divergent effects of first-generation and second-generation antipsychotics on cortical thickness in first-episode psychosis.

Water-soluble benzylidene cyclopentanone based photosensitizers for in vitro and in vivo antimicrobial photodynamic therapy.

Synthesis and characterization of novel purpurinimides as photosensitizers for photodynamic therapy.

Effect of chirality on cellular uptake, imaging and photodynamic therapy of photosensitizers derived from chlorophyll-a.

Amphiphilic zinc phthalocyanine photosensitizers: synthesis, photophysicochemical properties and in vitro studies for photodynamic therapy.

Synthesis, characterization, and biological evaluation of new Ru(II) polypyridyl photosensitizers for photodynamic therapy.

The origin and meaning of the term "photodynamic" (as used in "photodynamic therapy", for example).

Mechanisms in photodynamic therapy: part one-photosensitizers, photochemistry and cellular localization.

Gold nanorod enhanced two-photon excitation fluorescence of photosensitizers for two-photon imaging and photodynamic therapy.

Folic acid conjugates with photosensitizers for cancer targeting in photodynamic therapy: Synthesis and photophysical properties.

Evaluation of vascular effect of Photodynamic Therapy in chorioallantoic membrane using different photosensitizers.

In vivo studies of nanostructure-based photosensitizers for photodynamic cancer therapy.

DNA intercalating Ru(II) polypyridyl complexes as effective photosensitizers in photodynamic therapy.