Leukocytosis became apparent earlier and was more severe in the BCL-2tg/MLL-AF9 and Mcl-1tg/MLL-AF9 mice (Fig. 1) and the AML phenotype was more differentiated, as were MLL-AF9 AMLs lacking the pro-apoptotic BH3-only protein BIM [22] (Fig. 2 and Supplementary Figure S4, S5). This evidence concerns the gene PROS1 and acute myeloid leukemia.