MCL1 and acute myeloid leukemia: Given that 20(S)-PPD-induced apoptosis involves the intrinsic/mitochondrial pathway, we examined the levels of the anti-apoptotic proteins Bcl-2, Bcl-XL, and MCL-1 and the pro-apoptotic proteins Bax, Bak, and Bim using Western blotting in AML cells following increasing concentrations of 20(S)-PPD for 8 h.