NR4A1/NR4A3 knock-out mice rapidly develop lethal acute myeloid leukemia (AML) (8, 9) and reduced dosage of these genes, in mice, leads to a phenotype that recapitulates myelodysplastic syndrome (MDS), a hematologic disorder with increased susceptibility to AML. Here, NR4A1 is linked to acute myeloid leukemia.