TMZ triggers ER stress to induce autophagy.

<p>(A and B) U87 MG cells were treated with 400 µM TMZ for the indicated time periods and then analyzed by immunoblotting with anti-GADD153, anti-GRP78, anti-GAPDH (A), and anti-caspase 12 (B) antibodies. (C) U87 MG cells were pretreated with 10 mM 4-PBA for 1 h, followed by treatment with TMZ for 36 h (for analysis of GRP78, GADD153, and LC3) or 72 h (for analysis of PARP, caspase 12, and caspase 3). Cell lysates were analyzed by immunoblotting. GAPDH was used as an internal control to normalize the amount of proteins applied in each lane. (D) U87 MG cells were treated as in (C) for 72 h to determine percentages of cells undergoing autophagy and apoptosis, as well as the cell viability (E) and percent of LDH release (F). (G) Long-term viability of cells after TMZ and 4-PBA co-treatment was measured by colony formation assay. Results are presented as the mean ± SD. **<i>p</i><0.01 vs. each respective control. ^##<i>p</i><0.01 vs. each respective TMZ group.