To test directly the contribution of blf-1 to apoptosis resistance in B-CLL we targeted bfl-1 expression by specific siRNA in fludarabine-resistant, bfl-1 high-expressing B-CLL cells (CLL-24, CLL-32, CLL-27 and CLL-33; Figure 4). This evidence concerns the gene BCL2A1 and B-cell chronic lymphocytic leukemia.