Trisomy 21 leukemias: finding the hits that matter.

Down syndrome is associated with a markedly increased risk of childhood leukemias, and identification of chromosome 21 sequences that have a role in leukemogenesis may provide insights into critical pathways and suggest targets for therapy and prevention. A study in this issue of Oncogene, defines human chromosome 21 sequences that alter hematopoiesis and induce expression of leukemia-associated markers.