RNAi-mediated knockdown of relaxin decreases in vitro proliferation and invasiveness of osteosarcoma MG-63 cells by inhibition of MMP-9.

PURPOSE The purpose of this study is to determine the role of relaxin knowdown by siRNA transfection in cellular growth and invasion of osteosarcoma MG-63 cells, and discusses the molecular mechanisms of this action. MATERIALS AND METHODS The expression of relaxin in MG-63 cell was examined by western blot or RT-PCR. To evaluate the biological role of relaxin, proliferation assay (MTT) and invasion assay (BD Matrigel™), apoptosis assay (TUNEL and ELISA) and cell cycle analysis (flow cytometer) were performed after silencing relaxin using siRNA. MMP-9 expressions were analyzed using RT-PCR, western blot and zymography after silencing relaxin. RESULTS Results showed that the downregulation of relaxin expression by siRNA in human osteosarcoma MG-63 cells significantly inhibited cell proliferation and invasion in vitro. Furthermore, relaxin knockdown led to cell arrest in the G1/G0 phase of the cell cycle, and eventual apoptosis enhancement in MG-63 cells. We provide evidence in our cell model that the relaxin siRNA down-regulated the expression of MMP-9 and the MMP-9 activity, suggesting that relaxin may promote the proliferation, invasion and metastasis of osteosarcoma cells by regulating the expression of MMP-9 and facilitating ECM degradation. CONCLUSIONS Therefore, siRNA-directed knockdown of relaxin may represent a viable clinical therapy for osteosarcoma.