The inhibition of ATF4-activated autophagy significantly increases apoptosis and reduces cell viability in several hypoxic cancer cells.130 Another study carried out on other cancer cells, including U373 MG, a GBM cell line, the hypoxia-induced UPR activated PERK (protein kinase RNA-like ER kinase) in the ER. This evidence concerns the gene EIF2AK3 and cancer.