Necroptosis as a consequence of photodynamic therapy in tumor cells

Photodynamic therapy (PDT) is an alternative to cancer treatment, demonstrating selectivity and significant cytotoxicity on malignant tissues. Such therapy involves two nontoxic components: photosensitizer (PS) and non-ionizing radiation. In optimal dosage combinations, PDT causes cellular and tissue effects by oxygen-dependent processes, leading tumor cells to regulated cell death pathways. Regulated necrosis, called necroptosis, can be triggered by PDT and is characterized by caspase-8 inhibition and RIPK1, RIPK3, and MLKL activities, leading to plasma membrane pores formation with subsequent cellular content release into the extracellular space. For this review, studies accessed by PubMed describing the relation between necroptosis and PDT were summarized. The results showed that PDT can trigger necroptosis mechanisms in different tumor cells. Moreover, a mix of different cell death types can co-occur. It is also important to highlight that necroptosis triggered by PDT is related to damage-associated molecular patterns (DAMPs) release, involving immunogenic cell death and vaccination. The cell death response is directly related to the photosensitizer chemical characteristics, concentration, incubation time, cellular location, and irradiation parameters. The synergism among all cell death types is an excellent advantage for avowing tumor resistance mechanisms and developing new solutions.