BCL-2 protein expression was highest in MLLr RS4;11 and SEMK2 together with the pro-B ALL cell line REH; and BCL-2, but not MCL-1 or BCL-XL, expression correlated with sensitivity to ABT-199 (r = −0.82, p = 0.008) (Figures 5E and S4C). Here, MCL1 is linked to acute lymphoblastic leukemia.