BHQ880 overcomes the growth promoting effect of BMSC on both IL-6-dependent and IL-6-independent MM cells. (A) INA-6 MM cells were cultured without and with BMSC in the presence of different doses of BHQ880 for 24 to 48 hours. Cell proliferation was assessed by [³H]thymidine uptake assay and is presented as percentage change from control. Data represent mean ± SD of 4 independent experiments performed in triplicates. (B) MM1S, OPM1, OPM2, U266, XG1 MM cell lines, and (C) primary cells from 5 MM patients were cultured without (−) and with (+) BMSC in the presence of BHQ880 for 48 hours. Cell proliferation was assessed by [³H]thymidine uptake assay and presented as change from control cells cultured in the absence of BMSC (−). Data represent mean ± SD of 4 independent experiments performed in triplicate.