HOXA9 and acute myeloid leukemia: Correspondingly, a 4-gene signature consisting of PBX3, HOXA7, HOXA9, and HOXA11 has been shown to be an independent predictor of poor survival in patients with cytogenetically abnormal AML (CA-AML), and that PBX3 (but not PBX1 or PBX2) is frequently co-expressed with HOXA9 in various subtypes of CA-AML, particularly MLL-rearranged AML, and may thus be a potential pathologic cofactor of HOXA9.