Figure 2.

Inhibition of mTOR activity down-regulates xCT and suppresses glucose deprivation-induced cell death. A, immunoblot analysis of U251, T98G, and LN229 cells cultured at LD or HD for 48 h. ERK, extracellular signal-regulated kinase. B, immunoblot analysis of U251, T98G, and LN229 cells treated with Torin 1 (250 nm) at LD for 24 h. C, U251, T98G, and LN229 cells were cultured at LD with or without Torin 1 for 48 h and placed in medium with or without glucose (Glc, 5 mm) for 24 h. D, U251 cells cultured at LD or HD were replaced in fresh medium (FM) or conditioned medium (CM) collected from HD culture after 48 h. Cells were then placed in medium with or without glucose (5 mm) for 24 h. Cell death 24 h after medium change was quantified using an LDH release assay. Cells treated with 0.1% Tween 20 were used for calculating 100% cell death. Error bars represent S.D. (n = 3). ***, p < 0.001; **, p < 0.01; n.s., not significant; calculated by one-way ANOVA with Tukey's post hoc test.