Fig. 1: IRE1α determines sensitivity to ferroptosis.

A Viabilities of control (non-targeting) and IRE1α-null MDA-MB-231 human triple-negative breast cancer cells upon treatment with erastin (2.5 μM, left) or cystine depletion (right). 24 h after erastin treatment or cystine withdrawal, cell viability was measured by CCK8 assay. Viability was set as 100% with 0 μM erastin (DMSO only) or 200 μM cystine. The same measurements were made with Panc-1 human pancreatic adenocarcinoma cells in (B) (2.5 μM erastin) and mouse embryonic fibroblasts (MEFs) in (C) (0.25–1 μM erastin). D Non-targeting and IRE1α-null MDA-MB-231 cells were subjected to IncuCyte Cytotox Red staining & imaging upon treatment with 10 μM erastin. Representative phase+red fluorescence channel images from 0 and 12 h are shown on the left and quantitation on the right. E Non-targeting and IRE1α-null MDA-MB-231 cells overexpressing firefly luciferase (Luc), wild-type IRE1α (WT) or the K907A mutant IRE1α were subjected to 2.5 μM erastin treatment (left) or cystine depletion (right) and CCK8 assay was performed after 24 h. Viability was set as 100% with 0 μM erastin (DMSO only) or 200 μM cystine. F Cells used in (A) and (E) were subjected to 2.5 μM erastin treatment for 18 h, then C11-BODIPY 581/591 staining and flow cytometry analysis were performed to measure lipid peroxidation. G Non-targeting and IRE1α-null MDA-MB-231 cells overexpressing Luc, spliced/activated XBP1 (XBP1s), or unspliceable XBP1 (XBP1u) were subjected to 5 μM erastin treatment and CCK8 assay was performed after 24 h. Viability was set as 100% with 0 μM erastin (DMSO only). Data are presented as mean ± s.d. in all panels except (F). n = 6 in all panels except (F) and (D). n indicates independent repeats. In (D), quantification is based on n = 36 images in each group. Unpaired, two-tailed Student’s t tests were performed to calculate the P values for all the statistical analyses. N.S. not significant. Source data are provided as a Source Data file.