Erlotinib reduces RA synovial fibroblasts proliferation and cytokine production. A, RA synovial fibroblasts were stimulated with EGF (1 ng/ml) and PDGFbb (10 ng/ml) and concurrently treated with erlotinib (0.5 μM) or PD153035 (0.5 μM). After 48 hours of incubation, proliferation was analyzed by BrdU incorporation. B-E, RA synovial fibroblasts were stimulated with increasing concentrations of EGF and concurrently treated with erlotinib (5 μM). After 48 hours of incubation, the concentrations of (B) VEGF, (C) IL-8, (D) MCP-1 and (E) MMP-3 were determined by ELISA. Data represent one experiment of at least three independent experiments (*P < 0.05; **P < 0.01; *** P < 0.001). Error bars indicate ± SEM. E, To examine EGFR signaling in the cells, cells were pretreated with erlotinib (5 μM) or PD153035 (5 μM) for 30 minutes, stimulated with EGF (50 ng/ml) for 5 minutes, and cell lysates were examined via western blotting. Data represent one experiment of at least three independent experiments. PD = PD153035.