HOXA9 and acute myeloid leukemia: PBX2, a well-known homeodomain protein whose abnormal expression enhances homeobox A9 (HOXA9)-dependent leukemogenesis, is a new let-7c target that may impact the AML phenotype, suggesting that that perturbation of the let-7c-PBX2 pathway may have a beneficial role in AML (44).