Inhibitory effect of bone morphogenetic protein-2 on the proliferation of giant cell tumor of bone stromal cells in vitro

The inhibitory effect of bone morphogenetic protein-2 (BMP-2) on the proliferation of giant cell tumor of bone stromal cells (GCTSCs) has not been fully elucidated. Therefore, the aim of this study was to evaluate the role of recombinant human BMP-2 (rhBMP-2) in the growth of GCTSCs. The effects of exposure to different concentrations of rhBMP-2 (0, 10, 100 and 300 ng/ml) for 1, 3, 5 and 7 days on GCTSC proliferation were examined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In addition, the effect of treatment with rhBMP-2 (0 or 10 ng/ml) for 48 h on the cell cycle pattern of GCTSCs was examined by flow cytometry. The apoptosis-inducing effect of rhBMP-2 (0 or 10 ng/ml) in GCTSCs was also determined by flow cytometry after 48 and 72 h. In addition, western blot assays were conducted to determine whether rhBMP-2 acts on non-Smad mitogen-activated protein kinase (MAPK) signaling pathways, namely extracellular signal-regulated kinase (ERK1/2), p38 and c-jun-N-terminal kinase (JNK) pathways. The proliferation of GCTSCs treated with rhBMP-2 (10, 100 or 300 ng/ml) for 5 or 7 days was significantly inhibited in a non dose-dependent and non-time-dependent manner (P<0.05). The treatment of GCTSCs with rhBMP-2 (10 ng/ml) for 48 h had no effect on cell cycle distribution. The apoptosis of GCTSCs induced by exposure to rhBMP-2 (10 ng/ml) for 48 or 72 h was significant (P<0.05). Expression levels of phospho-ERK1/2, phospho-p38 and phospho-JNK increased significantly when GCTSCs were treated with rhBMP-2 (10 ng/ml) for 72 h (P<0.05). The results indicate that rhBMP-2 has no stimulatory effect on GCTSC growth. However, it may lead to the apoptosis of GCTSCs by non-Smad MAPK signaling pathways.