Synergistic effect of GX15-070 and bortezomib in MCL cell lines. (A) Cells from 3 MCL cell lines were cotreated with 5 nM (UPN-1) or 10 nM (Jeko and Granta-519) bortezomib and increasing doses of GX15-070 (0.1-5 μM) for 18 hours. Cytotoxicity was evaluated by cytofluorimetric analysis of Annexin V–APC. *Doses needed to observe a synergistic effect between bortezomib and GX15-070. Results represent the mean ± SD of 3 independent experiments. (B) Mcl-1, Bak, and Noxa expression was analyzed by Western blot in 50 μg of total protein extracts from UPN-1, Jeko, and Granta-519 cells cotreated with GX15-070 and bortezomib for 18 hours. α-tubulin was also probed as an equal loading control. Western blot images are representative results from 3 independent experiments.