Treatment of human chronic lymphocytic leukemia cells with the proteasome inhibitor bortezomib promotes apoptosis.

New options are needed for the treatment of B-cell chronic lymphocytic leukemia (CLL). Proteasome inhibitors represent a potential therapeutic strategy. One such agent, bortezomib, was recently approved for the treatment of refractory multiple myeloma. In this study, lymphocytes were isolated from the blood of CLL patients, treated in vitro with bortezomib, and evaluated for apoptosis by flow cytometry. Bortezomib promoted apoptosis in CLL cells in a dose- and time-dependent manner. At 18 h incubation time, 10 nM bortezomib induced an average 4.27 fold (+/-2.57) increase in the percentage of apoptotic cells versus untreated controls. These data indicate that bortezomib has in vitro activity in CLL and support further investigations of this promising new drug.