['B-cell chronic lymphocytic leukemia (B-CLL) is a remarkably heterogeneous disorder. Some patients have an indolent disease whereas others undergo a more agressive presentation needing treatment. New therapeutics approaches are necessary for the treatment of B-CLL. Bortezomib (Btz), is a proteasome inhibitor, currently undergoing clinical trials whose function, at least in part, by stabilizing the IkappaBalpha protein and inhibiting NFkappaB activation.', 'The objective of this work was to study the effects of Btz on isolated human B-CLL cells, in vitro, and to correlate the differential rates of apoptosis induction with biological variables.', '31 B-CLL samples, from patients in stage A of Binet were used for this study, and the apoptotic effect of Btz on these cells was measured.', 'Our data show that Btz treatment of B-CLL cells induces apoptosis in a time and dose-dependent manner. The apoptosis induction is mediated in part by inhibition of NFkappaB and is dependent on caspases activation. Interesting, in IgVH mutated cells, Btz have statistically significant differences in their in vitro activity on B-CLL cells according to their BCL-6 mutational status.'] Does bortezomib induce different apoptotic rates in B-CLL cells according to IgVH and BCL-6 mutations?