PBX1 and leukemia: Orderly HOX gene activation is essential for normal hematopoiesis with HOX genes preferentially expressed in the hematopoietic stem cell compartment and then down-regulated following differentiation and maturation.[58] There is considerable evidence in the literature associating dysregulation of HOX/TALE genes in AML.[58] Constitutive expression of HOXA7, HOXA9, HOXA10, HOXB3, and HOXB8 in mice results in acute leukemia,[83], [84], [85], [86] and recurrent chromosomal translocations in humans involving HOXA9[87], PBX1[88], and HOX11[89] results in leukemia.