Mechanism Study Of Photodynamic Therapy-triggered Cell Death By A Novel Photosensitizer

Photodynamic therapy(PDT) is an efficient cancer treatment.PDT can induce various forms of cell death containing apoptosis,autophagy and necrosis.However,Early studies in our laboratory indicated that cervical cancer Hela cells showed characteristics that are inconsistent with these common types of cell death,after cells were incubated with TPCI(a novel photosensitizer)and irradiated with light.In this study,we compared the rescue effects of different inhibitors on Hela cell death induced by TPCI-、5-ALA-、RB-、MB-PDT.We used western blot to detect apoptotic signals.The results indicated that the cell death induced by TPCI-PDT is different from RB-,MB-and 5-ALA-PDT.In addition,inhibitors of oxidative stress-related proteins ACSL4 and ALOX12 have an inhibitory effect on TPCI-PDT-induced cell death.We knockdown the expression of ACSL4 and ALOX12 in Hela cells with RNA interference.And MTT results showed that down-regulating ACSL4 or ALOX12 can increase the resistance of Hela cells to TPCI-PDT.At the same time,the regulation of intracellular GPX4 level can affect the cellular sensitivity to TPCI-PDT.Besides,we selected four human tumor cell lines and used MTT method to evaluate the rescue effects of various inhibitors on TPCI-PDT-induced cells death.Current results showed TPCI-PDT can induce similar cell death in these 4 cell lines.Finally,flow cytometry was used to affirm that TPCI-PDT could induce decreased mitochondrial membrane potential.Mass spectrometry studies identitied that TPCI-PDT could induce soybean phosphatidylcholine(SPC)to directly generate lipid peroxides in vitro.This study has revealed the relationship between TPCI-PDT and ferroptosis,a new type of cell death reported rencently.Ferroptosis was reported to be iron-dependent,accompanied by lipid peroxidation.In this study,although ALOX12 and PDT could contribute to lipid peroxidation,TPCI-PDT-induced cell death did not show an obvious iron dependence.Therefore,to solve these problems and clarify TPCI-PDT-related pathways in cells,further research is needed.