ERN1 and breast cancer: Similar to the situation in breast cancer cells 5, we found IRE1α branch was activated in lipin‐1‐deficient LUAD cells, indicated by increased phosphorylated IRE1α level, and dramatically upregulated sXBP1 (the spliced form of X‐box‐binding protein‐1; Fig. 5A), while the other indicators of ER stress were not changed (Fig. S3A).