Although the pronounced activation of UPR signaling in cancer has been reported mainly for extreme hypoxic conditions [65,146], numerous reports have indicated that particular aspects of this are triggered even in less oxygen-limiting conditions, including increased BIP expression [33,123,183,184,185,186,187] and PERK-related activity [73,184,188,189,190,191,192]. This evidence concerns the gene EIF2AK3 and cancer.