Strategies for Improving Photodynamic Therapy Through Pharmacological Modulation of the Immediate Early Stress Response

Participation of lipids in the tumor response to photodynamic therapy and its exploitation for therapeutic gain

Hydroperoxides of unsaturated membrane lipids (LOOHs) are the most abundant non-radical intermediates generated by photodynamic therapy (PDT) of soft tissues such as tumors and have far longer average lifetimes than singlet oxygen or oxygen radicals formed during initial photodynamic action. LOOH-initiated post-irradiation damage to remaining membrane lipids (chain peroxidation) or to membrane-associated proteins remains largely unrecognized. Such after-light processes could occur during clinical oncological PDT, but this is not well-perceived by practitioners of this therapy. In general, the pivotal influence of lipids in tumor responses to PDT needs to be better appreciated. Of related importance is the fact that most malignant tumors have dramatically different lipid metabolism compared with healthy tissues, and this too is often ignored. The response of tumors to PDT appears especially vulnerable to manipulations within the tumor lipid microenvironment. This can be exploited for therapeutic gain with PDT, as exemplified here by the combined treatment with the antitumor lipid edelfosine.

Comparative analysis of whole cell-derived vesicular delivery systems for photodynamic therapy of extrahepatic cholangiocarcinoma

This first-in-its-class proof-of-concept study explored the use of bionanovesicles for the delivery of photosensitizer into cultured cholangiocarcinoma cells and subsequent treatment by photodynamic therapy (PDT). Two types of bionanovesicles were prepared: cellular vesicles (CVs) were fabricated by sonication-mediated nanosizing of cholangiocarcinoma (TFK-1) cells, whereas cell membrane vesicles (CMVs) were produced by TFK-1 cell and organelle membrane isolation and subsequent nanovesicularization by sonication. The bionanovesicles were loaded with zinc phthalocyanine (ZnPC). The CVs and CMVs were characterized (size, polydispersity index, zeta potential, stability, ZnPC encapsulation efficiency, spectral properties) and assayed for tumor (TFK-1) cell association and uptake (flow cytometry, confocal microscopy), intracellular ZnPC distribution (confocal microscopy), dark toxicity (MTS assay), and PDT efficacy (MTS assay). The mean ± SD diameter, polydispersity index, and zeta potential were 134 ± 1 nm, -16.1 ± 0.9, and 0.220 ± 0.013, respectively, for CVs and 172 ± 3 nm, -16.4 ± 1.1, and 0.167 ± 0.022, respectively, for CMVs. Cold storage for 1 wk and incorporation of ZnPC increased bionanovesicular diameter slightly but size remained within the recommended range for in vivo application (136-220 nm). ZnPC was incorporated into CVs and CMVs at an optimal photosensitizer:lipid molar ratio of 0.006 and 0.01, respectively. Both bionanovesicles were avidly taken up by TFK-1 cells, resulting in homogenous intracellular ZnPC dispersion. Photosensitization of TFK-1 cells did not cause dark toxicity, while illumination at 671 nm (35.3 J/cm2) produced LC50 values of 1.11 μM (CVs) and 0.51 μM (CMVs) at 24 h post-PDT, which is superior to most LC50 values generated in tumor cells photosensitized with liposomal ZnPC. In conclusion, CVs and CMVs constitute a potent photosensitizer platform with no inherent cytotoxicity and high PDT efficacy in vitro.

Inhibition of Survival Mechanisms and Cell Death Induction in Melanoma Following Photodynamic Therapy Mediated by Meso-5,10,15,20-tetrakis-(4-hydroxyphenyl)-porphyrin

(1) Background: Photodynamic therapy (PDT) involves the selective killing of tumor cells by the generation of reactive oxygen species using a photosensitizer (PS) activated by irradiation. In melanoma, PDT efficiency is altered by several mechanisms, such as the presence of melanin and melanosomes and pro-survival pathways mediated by transcription factors such as: AP-1 (activator protein), MITF (microphthalmia inducible transcription factor), HIF1α (hypoxia inducible factor), and NF-kB (nuclear factor kappa B). The study aimed to investigate the anti-melanoma effects of PDT mediated by meso-5,10,15,20-tetrakis-(4-hydroxyphenyl)-porphyrin (THPP) as a photosensitizer. (2) Methods: Cocultures of melanoma, two human, WM35 and M1–15, and murine B16-F10, with endothelial cells, were used. Cytotoxicity, oxidative damage, angiogenesis markers, and melanogenesis were assessed using colorimetry, flowcytometry, confocal microscopy, spectrophotometry, ELISA, and Western blotting. (3) Results: The maximal killing efficiency of PDT was reached in WM35, followed by M1–15, and then B16-F10, and it occurred through both apoptosis and necrosis. Although constitutive pigmentation diminished the PDT efficiency, de novo melanogenesis exhibited no protection. PDT increased TNFα, and inhibited NFkB, MITF, HIF1α, and AP1, leading to inflammation and angiogenesis markers’ inhibition. (4) Conclusions: THPP-mediated PDT efficiently induced cell death through apoptosis, necrosis, and the inhibition of pro-survival pathways mediated by NFkB, AP1, HIF1α, and MITF in the melanoma coculture models.