Mechanisms of cell killing in photodynamic therapy using a novel in vivo drug/in vitro light culture system

Antitumor effects evaluation of a novel porphyrin derivative in photodynamic therapy

In this paper, the antitumor activity of a novel porphyrin-based photosensitizer 5,10,15,20-tetrakis[(5-diethylamino)pentyl] porphyrin (TDPP) was reported in vitro and in vivo. The photophysical and cellular properties of TDPP were investigated. The singlet oxygen generation quantum yield of TDPP was detected; it showed a high singlet oxygen quantum yield of 0.52. The intracellular distribution of photosensitizer was detected with laser scanning confocal microscopy. The efficiency of TDPP-photodynamic therapy (PDT) in vitro was analyzed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay and in situ trypan blue exclusion test. Treated with a 630-nm laser, TDPP can kill cultured human esophageal cancer cell line (Eca-109) cells and reduce the growth of Eca-109 xenograft tumors significantly in BABL/c nude mice. And histopathological study was also used to confirm the antitumor effect. It has the perspective to be developed as a new antitumor drug in photodynamic therapy and deserves further investigation.

Evaluation of a bacteriochlorin-based photosensitizer's anti-tumor effect in vitro and in vivo

PURPOSE

Bacteriochlorin derivatives are promising photosensitive agents for photodynamic therapy (PDT) of tumors. In the current study, the photodynamic activity of a novel bacteriochlorin derivative, cis-2, 3, 12, 13-tetracarboxymethyl-5, 10, 15, 20-tetraphenyl bacteriochlorin (TCTB), was evaluated both in vitro and in vivo.

METHODS

Physicochemical characteristics of the novel photosensitizer were measured. The efficiency of TCTB-PDT in vitro was analyzed by MTT assay, clonogenic assay and in situ trypan blue exclusion test. The intracellular distribution of photosensitizer was detected with laser scanning confocal microscopy. The accumulation of TCTB in human malignant tumor cells was measured by fluorescence spectrometer, and the pathway of cell death was analyzed by flow cytometry. S180 tumor model was used to evaluate the anti-tumor effects of TCTB-PDT. And histopathological study was also used to confirm the anti-tumor effect.

RESULTS

TCTB shows a singlet oxygen quantum yield of 0.56 and displays a characteristic long wavelength absorption peak at 732 nm. The accumulation of TCTB increased in time-dependent manner, and it was found in cytoplasm and nuclear membranes. In vitro PDT using TCTB and Nd:YAG laser showed drug concentration-, laser dose-dependent cytotoxicity to human esophageal cancer Eca-109 cells. In mice bearing osteosarcoma S180 tumors, the combined use of 10 mg/kg TCTB and 120 J/cm(2) showed superior anti-tumor activity. Histology examination of tumor tissues revealed that PDT using TCTB and the Nd:YAG laser induced tumor cells shrunken and necrotic.

CONCLUSION

In in vitro and in vivo studies, we found that TCTB has excellent anti-tumor effect. It suggests that TCTB is a potential photosensitizer of PDT for cancer.

Photodynamic therapy may be useful in debulking cutaneous lymphoma prior to radiotherapy

Photodynamic therapy (PDT) with topical 5-aminolaevulinic acid (5-ALA) is a promising new treatment for superficial malignant nonmelanoma tumours, including cutaneous malignant lymphoma. Here, we report a case of cutaneous anaplastic large cell lymphoma effectively treated by PDT with topical 5-ALA in combination with radiotherapy.

In vitro photodynamic therapy of nasopharyngeal carcinoma using 5-aminolevulinic acid

The purpose of this study was to investigate the potential use of 5-aminolevulinic acid (5-ALA, 5-amino-4-oxovaleric acid) induced protoporphyrin IX (PPIX) for photodynamic therapy (PDT) of nasopharyngeal carcinoma (NPC) and its related mechanisms of inducing cell death. PPIX biosynthesis at I to 8 h after incubation of a cultured NPC cell line (HNE1) with 5-ALA (10-5,000 microg ml(-1)) was determined via fluorescence analysis HNEI cells were irradiated at 4 h after incubation with 5-ALA (10-200 microg ml(-1)) by diode laser (lambda = 630 nm) at various energy levels (1-50 J cm(-2)). The survival rates at 6, 12, 24 and 48 h after PDT were determined by MTT assay. Mechanisms of PDT-induced cell death were investigated via Anncxin-V/propidium iodide staining and DNA electrophoresis After incubation with 5-ALA, a time- and dose-dependent increase of cellular PPIX-fluorescence was recorded up to a threshold concentration of 1,000 microg ml(-1) 5-ALA, above which a decline of fluorescence intensities occurred. Similar values of PPIX-fluorescence were found at 100-1,000 microg ml(-1) of 5-ALA. Unlike sole incubation with 5-ALA or sole laser irradiation, the combination of both factors lead to a significant, concentration-, energy- and time-dependent increase of cell death (p < 0.01). At 100 microg ml(-1) ALA and 10 J cm 2 laser irradiation, cellular survival was <5% after 48 h. More than 80% of induced cell deaths thereby occurred via apoptosis within the first 12 h following irradiation; necrosis was accountable for less than 20%. High level induction of apoptosis by 5-ALA-PDT was confirmed by DNA electrophoresis. Our investigations show promising results of 5-ALA based PDT of nasopharyngeal carcinoma in vitro and set the basis for future studies in tumor models or humans, respectively.

Effect of photodynamic therapy (PDT) on the expression of pro-apoptotic protein Bak in nasopharyngeal carcinoma (NPC)

BACKGROUND AND OBJECTIVE

To investigate the effect of photodynamic therapy (PDT) on expression of the pro-apoptotic gene Bak in nasopharyngeal carcinoma (NPC).

STUDY DESIGN/MATERIALS AND METHODS

Apoptosis and expression of the pro-apoptotic gene Bak on the tumor tissues from both pre- and post-PDT were determined using the in situ end labeling (ISEL), standard immunohistochemistry technique and western blot, respectively, in 24 patients with either persistent or recurrent NPC after radiotherapy.

RESULTS

Before PDT, apoptotic index (AI) in tumor tissue was 1.2 +/- 0.6. At 6, 12, 24 and 48 hours after PDT, AI were 6.5 +/- 3.1, 23.6 +/- 8.3, 67.2 +/- 14.2 and 89.3 +/- 8.1, respectively. PDT caused apoptosis in a time-dependent fashion. Immunohistochemical assay indicated that 75% (18/24) of the patients had an upgrade expression of Bak protein in their tumor tissues after PDT. Increases in expression of Bak from PDT were also confirmed by western blot analysis.

CONCLUSIONS

PDT probably causes NPC cell apoptosis through an upregulation of the pro-apoptotic protein Bak expression.

Inhibitory effect of hemin on mutagenicity of the electrophilic sulfuric acid ester of 6-hydroxymethylbenzo[a]pyrene

In the present study, we examined the effects of hemin on the mutagenicity of 6-sulfooxymethylbenzo[a]pyrene (SMBP) in Salmonella typhimurium TA98 and Chinese hamster lung fibroblast (V79) cells. The compound was tested for the possible chemoprotective activity against mutagenesis induced by SMBP and its precursor, 6-hydroxymethylbenzo[a]pyrene (HMBP), activated by hepatic cytosol and PAPS in S. typhimurium TA98. Hemin not only inhibited the mutagenic activity of SMBP in V79 cells but repressed the cytotoxicity induced by this reactive ester as demonstrated by increased cell growth. The intracellular accumulation of radioactivity in V79 cells exposed to [3H]SMBP was reduced by approximately 50% when hemin (10 microM) was added to the medium. Likewise, the formation of SMBP-DNA adducts in these cells was significantly attenuated by treatment with hemin. The covalent complex formation of hemin with SMBP was confirmed by solvent extraction and reverse-phase HPLC.

Photophysical and photobiological processes in the photodynamic therapy of tumours

Photodynamic therapy (PDT) is an innovative and attractive modality for the treatment of small and superficial tumours. PDT, as a multimodality treatment procedure, requires both a selective photosensitizer and a powerful light source which matches the absorption spectrum of the photosensitizer. Quadra Logic's Photofrin, a purified haematoporphyrin derivative, is so far the only sensitizer approved for phase III and IV clinical trials. The major drawbacks of this product are the lack of chemical homogeneity and stability, skin phototoxicity, unfavourable physicochemical properties and low selectivity with regard to uptake and retention by tumour vs. normal cells. Second-generation photosensitizers, including the phthalocyanines, show an increased photodynamic efficiency in the treatment of animal tumours and reduced phototoxic side effects. At the time of writing of this article, there were more than half a dozen new sensitizers in or about to start clinical trials. Most available data suggest a common mechanism of action. Following excitation of photosensitizers to long-lived excited singlet and/ or triplet states, the tumour is destroyed either by reactive singlet oxygen species (type II mechanism) and/or radical products (type I mechanism) generated in an energy transfer reaction. The major biological targets of the radicals produced and of singlet oxygen are well known today. Nucleic acids, enzymes and cellular membranes are rapidly attacked and cause the release of a wide variety of pathophysiologically highly reactive products, such as prostaglandins, thromboxanes and leukotrienes. Activation of the complement system and infiltration of immunologically active blood cells into the tumorous region enhance the damaging effect of these aggressive intermediates and ultimately initiate tumour necrosis. The purpose of this review article is to summarize the up-to-date knowledge on the mechanisms responsible for the induction of tumour necrotic reactions.

Determination of Photosan III in human plasma

In order to develop an accurate and quick method for the determination of Photosan III in human plasma, we used statistically planned experiments with an aim to identify the factors that can influence the analysis. Through a series of 20 experiments based on acid extraction of the porphyrin from the plasma and subsequent fluorescence analysis a calibration was obtained between 0 and 3.3 x 10(-5) M. The deviation of the parameters around the regression line is 3.02%, the coefficient of variation 3.55%.

Correlation of subcellular and intratumoral photosensitizer localization with ultrastructural features after photodynamic therapy

Photodynamic therapy (PDT) of cancer typically involves systemic administration of tumor-localizing photosensitizers followed 48-72 h later by exposure to light of appropriate wavelengths. Knowledge about the distribution of photosensitizers in tissues is still fragmentary. In particular, little is known as to the detailed localization patterns of photosensitizers in neoplastic and normal tissues as well as the relationship between such patterns and the actual targets for the photosensitizing effect. This review focuses on ultrastructural features seen in treated cells and tumors. An attempt is made to correlate these findings with the subcellular/intratumoral localization pattern of the photosensitizers in tumor cell lines in vitro and in tumor models in vivo. Several subcellular sites are main targets of PDT with different sulfonated aluminum phthalocyanines (AIPcSn) in the human tumor cell line LOX. Nuclei are not among the primary targets. Overall, the ultrastructural changes correlate well with the data about the subcellular localization patterns for each analogue of AIPcSn in the same cell line. Similar findings are also obtained for the family of sulfonated mesotetraphenylporphines (TPPSn) in the NHIK 3025 cell line. The mechanisms involved in the killing of tumors by PDT seem to be a complex interplay between direct and indirect (via vascular damage) effects on neoplastic cells according to the intratumoral localization pattern of the applied dye. Several factors can affect the localization pattern of a drug, such as its chemical character, the mode of drug delivery, the time interval between drug administration and light exposure, and tumor type. Furthermore, whether local immune reactions (such as macrophages) and apoptosis (programmed cell death) are involved in the destruction of neoplastic cells by PDT in vivo is still an enigma. A general model for PDT-induced tumor destruction is suggested.

Effect of haematoporphyrin-induced photosensitization on lipid membranes

In vitro cultured mouse myeloma (Sp-2/0-Ag14) cells and phosphatidylcholine liposomes were used to study the membrane effects of photosensitization with an He-Ne laser activated haematoporphyrin (HP). Lipophilic HP molecules, intercalated between the membrane lipid molecules, caused morphological changes of cell membranes on light activation. Steady state and time-resolved fluorescence spectroscopic studies of membrane-bound HP molecules provide information about the change in membrane lipid dynamics (fluidity). Increased HP fluorescence anisotropy was found after laser irradiation in the case of cell membrane. This finding can be related either to the increased rotation correlation time of the rotating fluorophore (HP) (decreased membrane fluidity) or to the decrease in the angular range of molecular rotation, which corresponds to an increased lipid order after photosensitization. Changes in the ratio of saturated:unsaturated fatty acid content of membrane lipids or other chemical events such as cross-linking of membrane components during the photosensitization process can also account for the observed effects.

Photofrin-induced fluorescence in progressive and regressive murine colonic cancer cells: correlation with cell photosensitivity

Microspectrofluorometry and fluorescence imaging were used to investigate the intracellular fluorescence of two murine colonic cancer cell lines--a progressive cell line (PROb) and a regressive cell line (REGb)--incubated with Photofrin. These two cell lines, which were initially cloned from the same chemically induced colonic murine cancer, differ in their metastatic properties and have been considered as models to mimic the tumoral cell heterogeneity. The fluorescence from cytoplasmic area of cells incubated with Photofrin appeared as a complex emission, with two maxima at 632 and 695 nm assigned to monomer species, and a poorly resolved band around 665 nm assigned to aggregates. The spectral distribution was shown to depend on the incubation time, with an aggregate contribution increasing for extended periods. The amount of Photofrin uptake, as determined from the total fluorescence intensity, was found for PROb to be twice that for REGb. However, the phototoxicities were quite similar for both cell lines, suggesting that drug concentration may not be the only determining factor in photobiological efficiency.

Photodynamic therapy with photofrin II induces programmed cell death in carcinoma cell lines

The mode of cell death following photodynamic therapy was investigated from the perspective of programmed cell death or apoptosis. Human prostate carcinoma cells (PC3), human non-small cell lung carcinoma (H322a) and rat mammary carcinoma (MTF7) were treated by photodynamic therapy. An examination of extracted cellular DNA by gel electrophoresis showed the characteristic DNA ladder indicative of internucleosomal cleavage of DNA during apoptosis. The magnitude of the response and the photodynamic therapy dosage required to induce DNA fragmentation were different in PC3 and MTF7. The MTF7 cells responded with rapid apoptosis at the dose of light and drug that yielded 50% cell death (LD50). In contrast, PC3 showed only marginal response at the LD50 but had a marked response at the LD85. Thus, apoptosis did not ensue as quickly in PC3 as in MTF7. The H322a cells were killed by photodynamic therapy but failed to exhibit any apoptotic response. The results also suggested that apoptosis in these cell lines has a minor requirement for de novo protein synthesis and no requirement for de novo RNA synthesis. This study indicates that although apoptosis can occur during photodynamic therapy-induced cell death, this response is not universal for all cancer cell lines.

Photosensitization with etiobenzochlorins and octaethylbenzochlorins

The photophysical and photobiological properties of a series of etiobenzochlorins were evaluated in cell culture using murine leukemia L1210 cells. In the series of agents tested, the chlorin-(mono)sulfonate was the most efficacious, the tin chlorin somewhat less so and the tin chlorin-sulfonate much less active. The parent chlorin was essentially inactive at the limit of solubility. Photodamage was assessed by measuring alterations in surface hydrophobicity (via a two-phase partitioning procedure), amino acid transport and membrane potential. Additional information was provided from fluorescence microscopy, which was used to identify sites of sensitizer binding and effects of photodamage on the binding patterns of fluorescent probes specific for mitochondria, lysosomes and plasma membranes. Effects of photodamage on fluorescence lifetime distribution of the membrane probe trimethylaminodiphenyl hexatriene were examined. The data obtained were consistent with localization of the parnet etiobenzochlorin and tin derivative at lysosomal loci, the chlorin-sulfonate at plasma and mitochondrial membranes and tin-sulfonate at the cell surface.

Photodynamic action of endogenously synthesized porphyrins from aminolevulinic acid, using a new model for assaying the effectiveness of tumoral cell killing

1. The effectiveness of the photodynamic action of porphyrins, was studied by means of the tissue explant culture technique. A murine tumor tissue explant was incubated in a medium containing 0.6 mM of ALA for periods of 1 and 2 hr; total porphyrins synthesized under these conditions were of the same level as those found in our previous in vivo experiments. The explants were then irradiated for 30 min with He-Ne laser of 3.5 mW output power placed at a distance of 10 cm. Controls of non-irradiated tumor tissue slices incubated with and without ALA were performed. Immediately after irradiation, inocula of exactly 1 mm3 of the irradiated and non-irradiated tissue were subcutaneously injected under the right and left flanks of the same animal, respectively. The growth of the tumor was measured 15, 20 and 25 days after implantation. 2. Results obtained showed that the explants that were incubated for 1 hr with ALA and irradiated, reaching a concentration of 2.8 micrograms porphyrins/g tissue, produced a reduction of 50-70% of tumor size as compared with the non-irradiated controls incubated with ALA. Explants incubated for 2 hr, reaching a concentration of 4.6 micrograms porphyrins/g tissue, produced from 60% to complete lack of tumor growth. The effectiveness index (EI) of photoirradiation was calculated on the basis of the tumor growth in irradiated and non-irradiated tumors. EI was nearly 100% showing almost complete tumor cell destruction for tumor irradiated for 2 hr with 0.6 mM ALA.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of thromboxane inhibitors on the microvascular and tumor response to photodynamic therapy

Vascular stasis and tissue ischemia are known to cause tumor cell death in several experimental models after photodynamic therapy (PDT); however, the mechanisms leading to this damage remain unclear. Because previous studies indicated that thromboxane release is implicated in vessel damage, we further examined the role of thromboxane in PDT. Rats bearing chondrosarcoma were injected with 25 mg/kg Photofrin (intravenously) 24 h before treatment. Light (135 J/cm2, 630 nm) was delivered to the tumor area after injection of one of the following inhibitors: (1) R68070: a thromboxane synthetase inhibitor; (2) SQ-29548: a thromboxane receptor antagonist; and (3) Flunarizine: an inhibitor of platelet shape change. Systemic thromboxane levels were determined. Vessel constriction and leakage were evaluated by intravital microscopy. Tumor response was assessed after treatment. Thromboxane levels were decreased more than 50% with SQ-29548 as compared to controls. Thromboxane levels in animals given R68070 and Flunarizine remained at baseline levels. SQ-29548 and R68070 reduced vessel constriction compared to controls, while Flunarizine totally prevented vessel constriction. R68070 and SQ-29548 inhibited vessel permeability compared to PDT controls; Flunarizine did not. Animals given these inhibitors showed markedly reduced tumor cure. These results indicate that the release of thromboxane is linked to the vascular response in PDT.