Indeed, cells with compromised PERK-eIF2α-ATF4 signaling are more sensitive to hypoxic stress in vitro and they form slower growing tumors in vivo, indicating that the PERK-eIF2α-ATF4 pathway confers a survival advantage for tumor cells under hypoxia (Fels and Koumenis, 2006). Here, ATF4 is linked to neoplasm.