BCL2 and B-cell chronic lymphocytic leukemia: For example, the overexpression Bcl-XL protects murine pro-lymphocytic cells from a wide variety of apoptotic stimuli and confers a multidrug resistance phenotype [58], and drug-induced apoptosis in B-CLL cells cultured in vitro is inversely related to Bcl-2/Bax ratios [52].