The RSK-3 inhibitor BI-D1870 suppresses 4-aminobiphenyl (4-ABP)-enhanced cartilage-derived-stem/progenitor cell (CSPC) proliferation. (A-D) CSPC from C57BL/6J mice were treated with vehicle, 4-ABP (10 μM), 4-ABP (10 μM) plus BI-D1870 (10 μM) or BI-D1870 (10 μM) alone. (A) Cell proliferative ability of CSPC was monitored 0-3 days after treatment, by CCK-8 method. a1p < 0.05 4-ABP versus vehicle; b1p < 0.05 4-ABP+BI-D1870 versus vehicle; c1p < 0.05, c2p < 0.01 BI-D1870 versus vehicle. n = 8 per group. (B) p-RSK-3 protein expression after chemical treatment for 3 days. (C) Relative p-RSK3 expression to total RSK3 is shown. **p < 0.01 versus vehicle, n = 3. (D) Ki67 (red) and p-RSK-3 (green) protein expression in CSPC after BI-D1870 and 4-ABP treatment. Nuclei are counterstained with DAPI. n = 3.