MCL1 and B-cell chronic lymphocytic leukemia: The targets are mostly Bcl-2 family proteins; this may involve either downregulation of the family's prosurvival members (mainly Bcl-2 and Mcl-1), which are crucial players in the impaired apoptosis in CLL, or upregulation the BH3-only proteins (Bim, Puma, Noxa), which are functional antagonists of the prosurvival members.