CD34 and leukemia: Higher SDF‐1‐induced migration was observed in AML for CD34+ BM‐derived cells than in paired CD34+ peripheral blood (PB)‐derived cells, and a lower percentage of circulating leukaemia blasts in patients with a relatively high level of SDF‐1 induced migration indicated the role of CXCR4 in the anchoring of leukaemia cells in the BM.34