Rearrangements of the human Histone-lysine N-methyltransferase 2A or myeloid/lymphoid/mixed lineage leukemia genes (KMT2A/MLL) are associated with a subtype of de novo and therapy-related acute myeloid and lymphoblastic leukemia (AML; ALL) [1] and result in a particularly poor prognosis in the majority of patients [2,3]. Here, KMT2A is linked to acute lymphoblastic leukemia.