Protein p53 modulation of autophagic cell death induced by photodynamic therapy

Abstract

Photodynamic Therapy (PDT) is an alternative treatment modality for cancer. PDT involves the activation of a photosensitizer (FS) using visible light and molecular oxygen to induce tumor cell killing, vascular destruction and immune system activation. PDT may induce either non-programmed cell death (necrosis) or programmed cell death type 1 (apoptosis) and type 2 (autophagic cell death). The autophagy itself is a eukaryotic pathway through which cell degrades and recycles damaged macromolecules and organelles. In a recent research performed in the Laboratório de Processos Fotoinduzidos e Interfaces, IQ-USP, it has been identified that the interruption of autophagic flux, as a result of oxidative damage in mitochondria and lysosomes by PDT, drives cell death with autophagic characteristics. This is interesting because tumor cells often have defects in the apoptosis pathway. The tumor suppressor protein p53 is involved in countless number of cellular processes, including apoptosis and autophagy. We believe that the p53 expression level must perform an important role in cell response to PDT. Thereby, the present project aims find out if the p53 protein modulates the autophagic cell death induced by PDT, and also identify potential targets involved in the death process. For this, we will use cell lines HEK293 with gene silencing of p53 (about 50-90%) and the respective cell control; the FS methylene blue and 1,9-dimethyl-methylene blue, and red LED light (630 nm). After PDT in vitro, we will evaluate the photocytotoxicity, the photoactivated cell death mechanisms, the cell redox balance and some protein level changes in autophagic flux; trying to relate the PDT efficiency to the type of cell death triggered and the expression level of p53. (AU)