MLL-rearranged (MLLr) leukemia is one of the most aggressive blood tumors, generally characterized by chromosomal translocations of MLL gene, located on chromosome 11q23 (Ziemin-Van Der Poel et al., 1991; Djabali et al., 1992; Krivtsov and Armstrong, 2007). The gene discussed is KMT2A; the disease is leukemia.