We found that when IRE1α was depleted in MDA-MB-231 triple-negative breast cancer cells, these cells became significantly more resistant to ferroptotic cell death induced by either erastin, an inhibitor of the cystine-glutamate antiporter SLC7A11, or cystine depletion (Fig. 1A and D; Supplementary Fig. 1A, C and D; Supplementary Fig. 3C; Supplementary Fig. 4E). Here, ERN1 is linked to triple-negative breast carcinoma.