ATF4 and cancer: Triggering cancer cell apoptosis is a function of multiple pathways, including adenosine monophosphate‐activated protein kinase (AMPK), Bcl‐2 associated protein X (Bax), Caspase‐3, ‐7, ‐8, ‐9, H2A histone family member X (H2AX), and protein kinase R (PKR)‐like endoplasmic reticulum kinase (PERK)/Eukaryotic Initiation Factor 2α (eIF2α)/activating transcriptional factor 4 (ATF4)/CCAAT‐enhancer‐binding protein homologous protein (CHOP) [60, 61, 63, 64, 65].