Proteasome inhibitor facilitates TRAIL-induced Bax activation and apoptosis. Fresh CLL cells were pretreated with 10 nM/L bortezomib for 1 hour and then incubated with or without 500 ng/mL TRAIL for 16 hours. (A) TRAIL ± bortezomib induced changes of Bax protein levels in 7 cases of CLL patients. (B) Association between Bax protein levels and Bax conformational change. CLL indicates the control; T, TRAIL-treated; B, bortezomib-treated; B + T, treated with bortezomib and TRAIL. The anti-Bax antibody 2D2 was used for Western blotting. The active Bax proteins were immunoprecipitated (IP) with 1 μg anti-Bax 6A7 antibody and detected by Western blotting using anti-Bax 2D2 antibody at 1:1000 dilution. (C) Apoptotic cell death was measured by DNA content assay. This is 1 of 3 separate experiments. Numbers shown in the flow cytometry profiles are percentages of apoptotic cells (sub-G0/G1 population).