OPN and IL-6 cooperatively acted to enhance MM cell growth. U266 cells (2 × 105/mL) were cultured in alpha-MEM containing 1% FBS in the presence (▪) or absence (□) of PBMC-OCs (1 × 104/mL) in 24-well culture plates in quadruplicate. Neutralizing antibodies against OPN and IL-6 alone or in combination, or control IgG were added at 20 μg/mL to the indicated wells (A). U266 cells were resuspended at 2 × 105/mL in alpha-MEM containing 1% FBS and cultured in wells coated with either rhOPN or human serum albumin in 24-well culture plates. rhIL-6 (10 ng/mL) was added to the indicated wells (B). Viable cell number was counted by trypan blue staining at day 4. The data are expressed as means ± SD. *Significantly different by one-way ANOVA with Scheffe post hoc tests, P < .05.
