Proteasome inhibitors induce Mcl-1 accumulation in primary B-CLL cells. PBMCs were isolated from blood samples obtained from 2 patients with B-CLL. Leukemic cells, as detected by CD19 expression, represented 76.5% and 75% of the cell preparations obtained from patient 1 and patient 2, respectively. Cells (3 × 10⁶/well) were incubated in 24-well plates in the presence or absence of 0.5 μM MG132 or 5 ng/mL bortezomib for the indicated amounts of time. Thereafter, cells were harvested and washed, and protein lysates were prepared. Mcl-1 and γ-tubulin expression were detected by Western blotting.