In keeping with a model whereby IRX3 misexpression in vivo blocks myeloid lineage differentiation, evaluation of the lineage composition of donor-derived cells in blood prior to development of AML demonstrated a significant proportional reduction in myeloid and a proportional increase in B-lineage differentiation at 4 and 12 weeks post-transplantation in Hoxa9/IRX3 versus Hoxa9/MTV recipients (Figures 3F and S3A). This evidence concerns the gene HOXA9 and acute myeloid leukemia.