ATF4 and cancer: Interestingly, obtained results have shown a significant increase in the mRNA expression level of the ATF4, DDIT3, and BAX pro-apoptotic genes, as well as a significant decrease in the level of anti-apoptotic gene Bcl-2 in cancer A549 cells treated with 50 μM of the NCI 159456 PERK inhibitor compared to that in the negative control cells.