EIF2A and neoplasm: However, according to another study by Mounir et al., PI3/AKT activation leads to Thr-799 phosphorylation-mediated inactivation of PERK and downstream eIF2α in glioblastoma U87 cells, human breast cancer SkBr3 cells, and spontaneously immortalized mouse embryonic fibroblasts (MEFs), thereby inhibiting their protective effect to tumor cells [54].