Bortezomib-induced Bax protein accumulation in DHL-4 cells. DHL-4 cells were treated with 100 nM/L bortezomib for 24 hours. Cells were collected for protein and mRNA extraction. (A) Bax protein expression was determined with Western blotting. Anti-Bax antibody 2D2 was used at 1:1000 dilution. Anti–β-actin antibody was used at 1:10 000 dilution. (B) Bax or actin mRNA was determined by RT-PCR. (C) TRAIL and bortezomib-induced apoptosis in the DHL-4 cell line. After DHL-4 cells were incubated with or without 100 nM/L bortezomib for 24 hours, cells were incubated with (B + T) or without 500 ng/mL TRAIL (Borte) for another 24 hours. Significantly increased sensitivity (P < .0001; t test) of cells treated with bortezomib and TRAIL was seen compared with cells treated with bortezomib or TRAIL alone. B + T indicates bortezomib plus TRAIL; and error bars, SD.