Effect of pharmacologic inhibitors on osteoclastic differentiation. Adherent PBMCs (A) and RAW264.7 cells (B) were cultured in the absence of cytokines or with RANKL plus M-CSF with or without TRAIL. Cultures were preincubated with vehicle (0.1% DMSO), PD98059 (20 μM), SB203580 (10 μM) prior to the addition of cytokines. After 10 days, the number of viable cells and the number of TRAP-positive multinucleated cells were scored. Data represent the means ± SD of 4 different experiments (^*P < .05, inhibitor vs vehicle).