Crosstalk between oxidative stress-induced apoptotic and autophagic signaling pathways in Zn(II) phthalocyanine photodynamic therapy of melanoma

GARCÍA VIOR, MARÍA C.; ROGUIN, LEONOR P.; VALLI, FEDERICO; MARINO, JULIETA

FREE RADICAL BIOLOGY AND MEDICINE

ELSEVIER SCIENCE INC

Año: 2020 p. 743 - 754

0891-5849

Melanoma is the most aggressive type of skin cancer, highly resistant to conventional therapies. Photodynamic therapy (PDT) is a minimally invasive treatment modality that combines the use of a photosensitizer, visible light and molecular oxygen, leading to ROS generation in the specific site of irradiation. The cationic zinc(II) phthalocyanine Pc13 has shown to be a potent photosensitizer in different melanoma cell lines. In this study, we explored the intracellular signalling pathways triggered by Pc13 PDT and the role of these cascades in the phototoxic action of Pc13 in human melanoma A375 cells. ROS-dependent activation of MAPKs p38, ERK, JNK and PI3K-I/AKT was observed after treatment. Inhibition of p38 reduced Pc13 phototoxicity, whereas blockage of ERK did not affect this response. Conversely, JNK inhibition potentiated the effect of Pc13 PDT. Results obtained indicate that p38 is involved in the cleavage of PARP-1, an important mediator of apoptosis. On the other hand, Pc13 irradiation induced the activation of an autophagic program, as evidenced by enhanced levels of Beclin-1, LC3-II protein and GFP-LC3 punctate staining. We also demonstrated that this autophagic response is promoted by JNK and negatively regulated by PI3K-I/AKT pathway. The blockage of autophagy increased Pc13 phototoxicity and enhanced PARP-1 cleavage, revealing a protective role of this mechanism, which tends to prevent the apoptotic cell death. Furthermore, reduced susceptibility to treatment and increased activation of autophagy were detected in A375 cells submitted to repeated cycles of Pc13 PDT and indicated that autophagy could represent a mechanism of resistance to PDT. The efficacy of Pc13 PDT and improved phototoxic action in combination with chloroquine were also demonstrated in 3D tumor spheroids. In conclusion, we showed the interplay between apoptotic and autophagic signaling pathways triggered by Pc13 PDT-induced oxidative stress. Thus, autophagy modulation could be a promising therapeutic strategy to potentiate the efficacy of PDT on melanoma.