Briefly, tumor cells were seeded 200 cells/wells and inoculated in six-well plates overnight. Then, the cells were treated with MF-438 (0.25 µM/ml), RSL3 (0.2 µM/ml), or Fer-1 (1 µM/ml) for 24 hours. Next, the TrueBeam SN1403 accelerator (Varian Medical Systems) was used to deliver RT with various doses (2, 4, 6, 8, 10, 12 Gy) to cancer cells. The medium was replaced and maintained for 14 days. After stained with crystal violet, tumor colony were calculated with microscope (Olympus Corporation) and Image J software (US National Institutes of Health, Bethesda). Survival fraction were estimated using linear quadratic model as we previously reported.27 (link) All the experiments were performed 3 times.