SDF-1 responsiveness, measured by CFU-GM, is reduced in CML patient samples. Chemotaxis assays were performed with mononuclear cells isolated from normal BM, BM from CML patients, and from peripheral blood samples from CML patients. CFU-GM are plotted as: (total number of colonies and clusters obtained with the migratory population)/(the number of colonies and clusters obtained with the input population) × 100 (see Materials and Methods). The stippled and solid bars represent CFU-GM formed by cells migrating to UltraCULTURE alone (control) or to 100 ng/mL of SDF-1, respectively.