Cdx4 Upregulates Hox Gene Expression and Generates Acute Myeloid Leukemia Alone and in Cooperation with Meis1a in a Murine Model.

HOX genes have emerged as critical effectors of leukemogenesis, but the mechanisms that regulate their expression in leukemia are not well understood. Recent data suggest that the caudal homeobox transcription factors CDX1, 2 and 4, developmental regulators of HOX gene expression, may contribute to HOX gene dysregulation in leukemia. We report here that CDX4 is normally expressed in early hematopoietic progenitors, and is aberrantly expressed in~25% of AML patient samples. Cdx4 regulates Hox gene expression in the adult murine hematopoietic system, and upregulates Hox genes that are implicated in leukemogenesis. Furthermore, bone marrow progenitors that are retrovirally engineered to express Cdx4 serially replate in methylcellulose cultures, grow in liquid culture and generate a partially penetrant, long-latency acute myeloid leukemia (AML) in bone marrow transplant recipients. Co-expression of the Hox co-factor Meis1a accelerates the Cdx4 AML phenotype and renders it fully penetrant. Structure -function analysis demonstrates that leukemic transformation requires intact Cdx4 transactivation and DNA-binding domains, but not the Pbx co-factor interaction motif. Taken together, these data indicate that Cdx4 regulates Hox gene expression in adult hematopoiesis and may serve as an upstream regulator of Hox gene expression in the induction of acute leukemia. Inasmuch as many human leukemias show dysregulated expression of a spectrum of HOX family members, these collective findings also suggest a central role for CDX4 expression in the genesis of acute leukemia.