MCL1 and B-cell chronic lymphocytic leukemia: The accumulation of the anti‐apoptotic BCL‐2 family proteins, such as BCL2, BCL‐xL, and MCL‐1, plays a role in the acquirement of resistance to spontaneous and drug‐induced apoptosis in CLL.41, 42, 43 We explored the effects of CUDC‐907 on these anti‐apoptotic proteins and found that it only affected their expression at the higher concentrations tested (Figure 2A and Figure S1), which suggests that it may not be an essential requirement for the induction of cell death here.