Targeting MGST1 Makes Non-Small Cell Lung Cancer Cells Sensitive to Radiotherapy by Epigenetically Enhancing ALOX15-Mediated Ferroptosis

Background: Ferroptosis is closely related to radiotherapy resistance in multiple can-cers. Herein, the role of microsomal glutathione S-transferase 1 (MGST1) in regulating ferropto-sis and radiotherapy resistance in non-small cell lung cancer (NSCLC) was investigated. Methods: Radiation-resistant NSCLC cells (NCI-1299-IR and HCC827-IR cells) were estab-lished. After exposure to X-ray, cell proliferation and survival were assessed by colony formation assay and CCK-8 assay, and lipid ROS level was examined by the fluorophore BODIPY™ 581/591 C11. MDA, GSH, and Fe2+ levels were measured by ELISA kits. The molecular interac-tion was analyzed using ChIP and MSP assays. Results: Our results showed that RSL3 treatment greatly enhanced the radiotherapy sensitivity of NCI-1299-IR and HCC827-IR cells. It was subsequently revealed that MGST1 was highly ex-pressed in NCI-1299-IR and HCC827-IR cells than its parent cells, and silencing of MGST1 re-duced radioresistance of NCI-1299-IR and HCC827-IR cells by facilitating ferroptosis. Mechanis-tically, MGST1 knockdown greatly reduced HO-1 and DNMT1/3A protein levels, leading to re-duced DNA methylation on the ALOX15 promoter region, thereby epigenetically upregulating ALOX15 expression. As expected, the promoting effects of MGST1 silencing on radiosensitivity and ferroptosis in radiation-resistant NSCLC cells were strikingly eliminated by ALOX15 knock-down. Conclusion: MGST1 knockdown epigenetically enhanced radiotherapy sensitivity of NCSLC cells by promoting ALOX15-mediated ferroptosis through regulating the HO-1/DNMT1 pathway.