MCL1 and B-cell chronic lymphocytic leukemia: This observation along with the evidence that the decrease in Mcl-1 levels induced by Notch silencing was observed in the vast majority of CLL cells with Notch-dependent viability (83.3%), but not in CLL cells whose viability was independent of Notch, suggest that Mcl-1 is important for Notch-mediated CLL cell survival.