Herein we present data supporting the conclusion that HoxA9 directly binds and inhibits the activity of the Cebpa +8 kb enhancer, strengthening the idea that HoxA9 impairs myeloid differentiation via repression of Cebpa gene expression in normal hematopoietic stem and progenitor cells and in poor-risk AML cases. This evidence concerns the gene HOXA9 and acute myeloid leukemia.