HOXA9 and leukemia: A subset of poor prognosis AML is characterized by aberrant expression of a group of HD proteins, including HoxB3, B4, A7–11, Cdx2, Cdx4 and Meis1.3, 4, 5, 38 This includes AML with MLL1 translocation or partial tandem duplication, but it also a poor prognosis subset with normal cytogenetics.3, 4, 38 We found that co-overexpression of HoxA9+HoxA10, or expression of a leukemia-associated Mll-fusion protein (Mll-Ell), facilitates HoxA10-dependent CDX4 transcription in myeloid progenitor cells.