C-X-C chemokine receptor 7 (CXCR7) does not affect migration, serum-deprivation-induced apoptosis, or spontaneous proliferation of acute myeloid leukemia (AML) cells. Using small interfering RNA (siRNA) technology, CXCR4 and CXCR7 were knocked down in MO7e and U937 cells and subsequent biological alterations occurring in the cells were evaluated. (A, B) Transmembrane migration of the cells. Data are expressed as mean±SD of the percentages of migrated cells. (C, D) Data are expressed as mean±SD of the Annexin V-positive apoptotic cells analyzed using flow cytometry. (E, F) Data are expressed as mean±SD of the relative proliferation index at indicated time. All data are from 3 independent experiments.