PEX5 deficiency enhances radiosensitivity via MGST1-GSH detoxifying function and promotes ferroptosis in liver cancer

Recent research underscores a growing connection between liver cancer irradiation resistance and ferroptosis, with glutathione (GSH) serving as a pivotal factor in this resistance by mitigating oxidative stress. Despite the crucial role of peroxisomes in modulating this redox balance, the influence of peroxisome biogenesis gene 5 (PEX5), a highly expressed gene in liver cancer cells that regulates peroxisome formation, on GSH-mediated resistance to radiation-induced ferroptosis remains poorly understood. We employed targeted metabolomics, RNA sequencing, and Raman spectroscopy, in radioresistant liver tumor cell models, human liver cancer organoids, and mouse model to investigate the phenomenon and potential mechanisms. Our findings revealed that combining ferroptosis inducers and radiotherapy (IR) effectively overcame radioresistance in both radioresistant liver tumor cells (IRR) and human liver cancer organoids. Notably, we observed a correlation between increased levels of amino acids involved in GSH synthesis and IR-induced ferroptosis resistance in IRR cells, indicating that GSH plays a significant protective role against ferroptosis in these cells. Furthermore, exogenous GSH supplementation was found to potentiate resistance to IR-induced ferroptosis, further confirming the protective role of GSH. However, suppression of PEX5, a previously identified radiosensitivity regulator, reversed GSH-mediated IR-ferroptosis resistance. Specifically, PEX5 suppression enhanced ferroptosis activation and radiation damage by impairing GSH function. Mechanistically, PEX5 binds to the transmembrane domain of MGST1, a crucial regulator for GSH detoxification. By inhibiting PEX5, we disrupted MGST1 functionality, resulting in the attenuation of radioresistance and the enhancement of ferroptosis, as MGST1's role in GSH detoxification was impaired, thereby increasing vulnerability to radiation-induced cellular ferroptosis. PEX5 deficiency induces ferroptosis by impairing the MGST1-GSH detoxification pathway, thereby enhancing radiation-induced damage via the regulation of redox balance. This novel function of PEX5 offers new insight in ferroptosis mediated by peroxisome and provides the potential novel therapeutic strategy to enhance the anti-tumor effects of radiation.