Psoralen at 40 μM promoted apoptosis in liver cancer SMMC7721 cells by enhancing GRP78 and GRP94 protein expression, activating the IRE1 and ATF6 pathways, and improving the gene expression of DDIT3, resulting in disruption of endoplasmic reticulum Ca2+ homeostasis and downregulating the expression of Bcl-2 (Wang et al., 2019). Here, ATF6 is linked to liver cancer.