By performing flow cytometric analysis with anti-Bax (clone 6A7) and anti-Bak (clone NT) antibodies that recognize the active form of Bax and Bak proteins, respectively (41–43), we detected near-complete inhibition of Bax and Bak activation as well as subsequent post-mitochondrial steps (cleavage of caspase 9, caspase 3, and PARP) in CLL cells treated with proapoptotic drugs in the presence of an agonist mix ex vivo (Supplemental Figure 1, E–H; data not shown for chemotherapy agents). Here, CASP9 is linked to B-cell chronic lymphocytic leukemia.