ATF4 and neoplasm: Throughout the various stages of tumor development influenced by ERS, it’s worth contemplating the cascading signals for tumor cell apoptosis elicited by ERS: (1) IRE1/TRAF2/ASK1/JNK pathway; (2) IRE1/TRAF2/caspase-12; (3) PERK/ATF4/CHOP; (4) IRE1–JNK–CHOP; (5) PERK/eIF2α/ATF4/CHOP/DR5; and (6) PERK/eIF2α/ATF4/CHOP/DR5 and other apoptotic pathways.