Inhibition of CXCR7 disrupts the homing of AMCs to MM-enriched BM niches. (A) The effect of increasing concentrations (0-500 nM) of the CXCR7 inhibitor POL6926 on migration of HUVECs to CM from MM1.S cells (24 hours incubation), normalized to the migration to non-CM as counted by flow cytometry. (B) Representative images of the effect of POL6926 (50 nM) on migration of AMCs to conditioned MM1.S media as detected by fluorescent microscopy. (C) The effect of POL6926 (50 nM) on migration of HUVECs to BM supernatant from 3 MM patients, counted by flow cytometry and normalized to migration of nontreated HUVECs in each. (D) A schematic description of the procedure. (E) The MM tumor burden of the 2 groups of MM-bearing mice. (F) The effect of CXCR7 on the homing of HUVECs, after IV injection to the BM of mice with established xenografts of MM1.S cells.