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.