In normal hematopoiesis, CXCR4 is critical for homing and retention of hematopoietic stem cells (HSCs) in the bone marrow (Foudi et al., 2006; Sugiyama et al., 2006); however, it is unclear whether CXCR4 is involved in homing of AML cells to the bone marrow. The gene discussed is CXCR4; the disease is acute myeloid leukemia.