FIG. 6.
The phosphorylation of eIF2α, ATF4 expression, and system xc− activity are regulated by PI3Ks in human cancer stem cell-derived glioblastoma cells. Relative eIF2α phosphorylation and nuclear ATF4 levels in glioblastoma cells derived from G35 (A) and G38 (B) glioblastoma-initiating cancer stem cells treated with 10 μM LY for 2 h compared with vehicle (Veh) (left panels). Total eIF2α and actin served as loading controls. Relative system xc− activity in G35 and G38 glioblastoma cells treated with 10 μM LY (LY) for 24 h compared with vehicle (Veh). Graphs represent the mean±SEM of three [(A), left lower and right, (B), left upper and right panel] to four [(A), left upper, (B) left lower panel] independent experiments. Statistical analysis was performed by one-sample t tests, *p<0.05, **p<0.01, and ***p<0.001.