As well as the strong association of IRX3 with HOX gene expression in acute leukemias of multiple lineages, there was also high-level expression of IRX3 in ∼90% of cases of APML and in ∼75% of cases of t(12;21) B-ALL, leukemias that do not express HOX genes. This evidence concerns the gene IRX3 and acute promyelocytic leukemia.