CDX2 is a member of the caudal homeobox family of transcription factors that also includes the proteins CDX1 and CDX4. CDX2 is strongly expressed in the trophectoderm in the blastocyst with expression maintained within the proliferating extra-embryonic ectoderm during development. It is required for the repression of the transcription of the POU5F1/Oct4 and NANOG genes in the outer cells of the blastocyst and is thus essential for the segregation of the inner cell mass and trophectoderm at the blastocyst stage. Aberrant expression of CDX2 is associated with numerous types of carcinomas, including intestinal metaplasia, gastric carcinoma, and acute myeloid leukemia due to deregulated HOX gene expression.