Efficient photodynamic therapy against drug-resistant prostate cancer using replication-deficient virus particles and talaporfin sodium.

To enhance the potency of photosensitizer, we developed a novel photosensitizer, Laserphyrin®-HVJ-E (L-HVJ-E), by incorporating talaporfin sodium (Laserphyrin®, Meiji Seika Pharma) into hemagglutinating virus of Japan envelope (HVJ-E). In this study, we examined the optimal Laserphyrin® concentration for preparation of Laserphyrin®-HVJ-E which had photocytotoxicity and maintained direct cytotoxicity derived from HVJ-E. Then, potency of Laserphyrin®-HVJ-E and Laserphyrin® were compared in vitro using castration-resistant prostate cancer cell line (PC-3). A laser diode (L660P120, Thorlabs, USA) with a wavelength of 664 nm was used for light activation of Laserphyrin®, which corresponds to an absorption peak of Laserphyrin® and provides a high therapeutic efficiency. The photocytotoxicity and direct cytotoxicity of Laserphyrin®-HVJ-E prepared using various Laserphyrin® concentrations were evaluated using PC-3 cell in vitro. We categorized the treatment groups as Group 1: 50 µL of D-MEM treatment group, Group 2: HVJ-E treatment group, Group 3: Laserphyrin®-HVJ-E treatment group, and Group 4: Laserphyrin® treatment group. Group 3 was subjected to different concentrations of Laserphyrin®-HVJ-E suspension, and all groups were subjected to different incubation periods (24, 48 h), (30 min, 1 h, or 3 h,) respectively, without and after PDT. Laserphyrin®-HVJ-E prepared using 15 mM Laserphyrin® had high photocytotoxicity and maintained HVJ-E's ability to induce direct cytotoxicity. Therapeutic effect of Laserphyrin®-HVJ-E was substantially equivalent to that of Laserphyrin® alone even at half Laserphyrin® concentration. By utilizing Laserphyrin®-HVJ-E, PDT could be performed with lower Laserphyrin® concentration. In addition, Laserphyrin®-HVJ-E showed higher potency than Laserphyrin® by combining cytotoxicities of HVJ-E and PDT.

Photodynamic therapy by lysosomal-targeted drug delivery using talaporfin sodium incorporated into inactivated virus particles.

BACKGROUND: Photodynamic therapy (PDT), a minimally invasive cancer treatment involving the activation of photosensitizer by a specific wavelength of light, is considered to be a promising treatment option for drug-resistant prostate cancer. Hemagglutinating virus of Japan envelope (HVJ-E) has the potential to serve as a highly effective cancer therapy through selective drug delivery and enhancement of the anti-tumor immune response. OBJECTIVES: To improve therapeutic efficacy and selective accumulation of photosensitizer into tumor cells, we developed a novel photosensitizer, Laserphyrin®-HVJ-E (L-HVJ-E), by incorporating talaporfin sodium (Laserphyrin®, Meiji Seika Pharma) into HVJ-E. MATERIALS AND METHODS: The therapeutic effect of PDT with Laserphyrin® or L-HVJ-E was evaluated in the human prostate cancer cell line PC-3 in vitro. The subcellular localizations of Laserphyrin® and L-HVJ-E were observed by confocal microscopy. Apoptosis or necrosis following PDT was detected by annexin V-fluorescein/propidium iodide double staining. RESULTS: The cytotoxic effect of Laserphyrin®- and L-HVJ-E-mediated PDT were determined by evaluating cell survival rate and production of reactive oxygen species. The cytotoxicity of L-HVJ-E-mediated PDT was dependent on drug concentration and light dose. Laserphyrin® and L-HVJ-E gradually entered cells as incubation time increased, and both agents tended to be distributed in lysosomes rather than mitochondria. Time and dose dependent increase in ROS production was observed, and induction of both apoptotic and necrotic cell death was confirmed. CONCLUSIONS: Laserphyrin® and L-HVJ-E were distributed mainly in lysosomes and induced cell death by both apoptosis and necrosis. Furthermore, L-HVJ-E-mediated PDT effectively killed cultured PC-3 cells and exerted higher photocytotoxicity than Laserphyrin®-mediated PDT.

Photodynamic therapy using a cytotoxic photosensitizer porphyrus envelope that targets the cell membrane.

BACKGROUND: Subcellular localization of a photosensitizer is known to determine the therapeutic efficacy of photodynamic therapy (PDT). Cell membrane is an optimal target that promises an effective treatment outcome. OBJECTIVES: We previously developed a novel photosensitizer named porphyrus envelope (PE) by combining hemagglutinating virus of Japan envelope (HVJ-E) with lipidated protoporphyrin IX (PpIX lipid). In the current study, the cellular localization of PE and its ability to induce multiple anti-tumor effect were characterized. MATERIALS AND METHODS: The localization and uptake of PpIX lipid in cells were evaluated with confocal laser scanning microscopy and a cell-based fluorescent assay, respectively. The ability of PE to suppress the migration and proliferation of cancer cells was assessed using a scratch-wound assay. The synergistic effect of PDT and HVJ-E treatment was evaluated using an in vitro experiment with PC-3 cells. RESULTS: PE localized along the cell membrane and PpIX lipid accumulated selectively in the prostate cancer cells within 10min. Also, PE maintained the ability to undergo fusion and induce cancer cell death even after light irradiation at the dose for PDT. Incubation with PE resulted in delayed migratory and proliferative activity of PC-3 cells. PE-mediated PDT was twice as effective when cells were further incubated with PE following PDT. CONCLUSIONS: PE allows rapid drug delivery targeting the cell membrane. Because the cytotoxicity of HVJ-E was maintained, synergistic effect of HVJ-E and the photochemical reactions resulted in highly effective killing of prostate cancer cells in vitro and thus represents a promising treatment for prostate cancer.