Cdx expression in normal and malignant hematopoiesis. (A) Normal hematopoiesis.Cdx4 and HOX A and B cluster genes are expressed in normal stem and progenitor cells, whereas Cdx2 and Cdx1 remain silenced. (B) Malignant hematopoiesis. Ectopic expression of CDX2 at the level of stem or progenitor cells induces increased expression of Hox A and B cluster genes and leukemic transformation of hematopoietic cells. The proportion of patients with AML, which ectopically express CDX2 and overexpress HOX genes, is indicated. CDX4 is expressed only in a minority of patients, and CDX1 expression is not detectable in patients with leukemia.