ATF4 and gastric cancer: A western blot analysis showed that the PF treatment upregulated the levels of CHOP, p-PERK, ATF4, p-eIF2α, and cleaved caspase-3, compared with the control groups; however, the PERK knockdown groups did not show an increase in the levels of CHOP, cleaved caspase-3, and p-PERK in PF-induced gastric cancer cell lines such as AGS and SNU-638 (Figure 5F).