Regulation of the Hox cluster target genes, including Hoxa9 and Meis1, previously emerged as a hallmark of MLL translocation leukemia, and the combined expression of Hoxa9 and Meis1 was sufficient for initiating a leukemogenic progenitor self-renewal program (Armstrong et al, 2002; Ayton &, Cleary, 2003; Ferrando et al, 2003; Huang et al, 2012; De Braekeleer et al, 2014; Garcia-Cuellar et al, 2016; Collins & Hess, 2016a). This evidence concerns the gene HOXA9 and leukemia.