Inhibition of CXCR7 exerts indirect inhibition of MM. (A) The expression of CXCR7 on the surface (upper panel) and intracellular (lower panel) of MM cell lines (MM1.S, OPM-1, OPM-2, H929, RPMI, U266, MM1R, and MOLP8). (B) The effect of a range of concentrations (0-500 nM) of POL9626 on proliferation of MM1.S, OPM-2, and HUVECs when each was cultured alone. (C) The effect of POL9626 (50 nM) on MM tumor proliferation induced by coculture with HUVECs.