Figure 5.

Inhibition of lysosomal activity promotes glucose deprivation–induced cell death. A, U251 cells cultured at LD or HD for 48 h were placed in amino acid–free medium with or without cystine (0.2 mm) and glutamine (2 mm) for 4 h, and glutamate released into the medium was measured. B, U251 cells were cultured at HD with or without BafA1 (1 μm) for 48 h. The cells were placed in amino acid–free medium with or without cystine (0.2 mm) and glutamine (2 mm) for 4 h, and glutamate released into the medium was measured. C, U251 cells were cultured at LD or HD with or without BafA1 (1 μm) for 48 h and placed in medium with or without glucose (Glc, 5 mm) for 24 h. D, U251 cells expressing FLAG-tagged xCT were cultured at LD or HD for 48 h and 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. E, model of cell density–dependent glioblastoma cell death under glucose deprivation. Error bars represent S.D. (n = 3). ***, p < 0.001, calculated by one-way ANOVA with Tukey's post hoc test.