BHQ880 inhibits IL-6 production and MM cell adhesion to BMSC from MM patients. (A) Both BMSC from MM patient alone and cocultured with INA-6 cells were treated with isotype control antibody (□) or 1 μg/mL BHQ880 (■) for 24 hours. Culture supernatant was then analyzed for huIL-6 level by ELISA. (B) INA-6 and MM1S MM cells were cultured in the presence of BMSC and increasing concentrations of rIL-6 (0, 0.5, and 1 ng/mL) with and without BHQ880 for 24 hours. Cell proliferation was assessed by [³H]thymidine uptake assay and is presented as percentage change from control. (C) Serum-starved MM cell lines and CD138⁺ patient MM cells were labeled with calcein AM, washed, and added to BMSC-coated plates for 4 hours with isotype control or increasing amounts of BHQ880 (0.1 and 1 μg/mL). Adhesion was evaluated by measuring the absorbance using 492/520 nm filter set with a fluorescence plate reader. Data represent mean ± SD of 4 independent experiments performed in triplicate.