Dasatinib reduces MM cell growth and survival by targeting VEGF₁₆₅ and PDGF-BB downstream signaling. (A) Proliferation of human MM cell lines treated with dasatinib for 48 hours. Data indicate the percentage of growth inhibition (± SD) of triplicate experiments. (B) Western blotting analysis of PDGF-BB, PDGFRβ, and pp60c-Src expression/activation status in the indicated MM cell lines. Vertical lines have been inserted to indicate a repositioned gel lane. (C) Antiproliferative effect of dasatinib in control BMMCs (CTR1 and CTR2) and plasma cells isolated from one representative patient with MM at diagnosis (MM-PC, D), relapse (MM-PC, R), or leukemic progression (L). (D) Antiproliferative effect of dasatinib in representative MM cases staged as indicated. (E) MM plasma cells were serum-starved (SFM) for 16 hours and then incubated with VEGF₁₆₅ and PDGF-BB in the presence of DMSO or dasatinib for 48 hours. Survival and cell- cycle distribution were assessed by propidium iodide staining and FACS analysis. (F) Adhesion cocultures of confluent MM patient-derived ECs (MMECs, 10⁶) and CSFE-prelabeled RPMI 8226 or MM plasma cells from patients (2 × 10⁶) incubated with or without dasatinib for 24 hours. Values represent the mean ratios of adherent MM plasma cells over MMECs from 3 independent experiments (P = .001). (G) Growth factor-deprived MM plasma cells were pretreated with or without dasatinib for 30 minutes, plated on a fibronectin-coated polycarbonate membrane in a Boyden chamber, and exposed to 10 ng/mL VEGF₁₆₅ or PDGF-BB for 6 hours. Data are means (± SD) of migrated cells in 5 fields (original magnification ×400). (H) Serum-starved MM plasma cells (−) pretreated with 50 nM of dasatinib (30 minutes) were stimulated with 10 ng/mL VEGF₁₆₅ or PDGF-BB for 15 minutes. VEGFR1 (IP: αVEGFR1) immunoprecipitates and total cell lysates were immunoblotted as indicated.