Bcl-2 and apoptosis in chronic lymphocytic leukemia.

The Bcl-2 family of pro- and antiapoptotic proteins are key regulators of the apoptosis cascade and the mitochondrial-mediated pathway of caspase activation. Of this family, Bcl-2 was the first identified and remains the best characterized. Aberrant expression of Bcl-2 is common in chronic lymphocytic leukemia (CLL) and is associated with poor response to chemotherapy and decreased overall survival. Bcl-2 is an attractive target for novel therapeutic agents. Antisense oligonucleotides directed against Bcl-2 are effective in vitro and are being evaluated in clinical trials in CLL. Small molecule Bcl-2 inhibitors are in preclinical development and should be ready for clinical evaluation in the next few years. Strategies that induce apoptosis and bypass Bcl-2 may also be therapeutically useful in CLL. Thus, over the next decade, one can envision incorporating measurements of apoptotic proteins such as Bcl-2 into the risk assessment and treatment algorithms for individual patients. In addition, we anticipate that in the next decade, rationally designed therapies targeting specific molecular defects in the malignant CLL lymphocytes will be introduced into the clinic.