Radiotherapy and 2-DG cotreatment potentiates UPR and leads to dose-dependent loss of cell viability and apoptosis. (A) Proliferation assay of Glio9, Glio11, and Glio14 treated with increasing doses of 2-DG with or without 8 Gy radiation for 72 h. Viability is reported as mean ± SEM. Data represent average values of at least three independent experiments. * p < 0.05, ** p < 0.01, *** p < 0.001. Mann-Whitney Test. (B) Western blot analysis for ER stress markers GRP78 and CCAAT-enhancer-binding-protein homologous protein (CHOP) after treatment using increasing doses of 2-DG with or without 8 Gy radiation. Cells were analyzed at early (8 h) and late (48 h) time points. (C) Lactate dehydrogenase assay to determine cytotoxicity of Glio9 (white), Glio11 (blue), and Glio14 (red) treated with 2-DG. Cytotoxicity is reported as mean ± SEM. Data represent average values of at least three independent experiments. (D) Western blot analysis of apoptosis markers, cleaved-PARP and caspase-7, after 48 h treatment of GSCs using 2-DG with or without 8 Gy radiation. (E) Western blot of full-PARP and cleaved-PARP in Glio9 to confirm presence of full PARP and lack of PARP cleavage despite combination therapy.