MCL1 and acute lymphoblastic leukemia: Initial studies with BH3 profiling predicted that ALL cells are dependent on BCL-2 and would be sensitive to its inhibition [22]; however, ALL cells display variability in their sensitivity to BCL-2 inhibition, suggesting other BCL-2 pro- and anti-apoptotic proteins (e.g., BCL-XL, MCL-1) as well as BH3-only proteins (BIM, BAD) modulate the response.