Background and purpose: Insulin-like growth factor-1 (IGF-1) is a peptide that participates in many biological processes by stimulating the downstream signaling pathways through their interaction with IGF-1 receptor (IGF-1R) and insulin receptor (IR). Bone morphogenetic proteins (BMPs) are a group of functional proteins which participate in the biological processes of proliferation and migration in many kinds of cancers and have become a hot area of cancer research. The study aimed to investigate the effects of silencing IGF-1R gene on the expression level of BMP2 gene

and the cell proliferation and apoptosis of SMMC7721 cells. Methods: The RNAi plasmid targeting IGF-1R gene was constructed and transfected into SMMC7721 cells. Then the inhibition effect on the expression level of IGF-1R and BMP2 gene was detected by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. The SMMC7721 growth curve and cell apoptosis were detected by MTT assay and flow cytometry after they were transfected with RNAi plasmid. Results: The RNAi plasmid targeting IGF-1R gene was constructed successfully. The inhibition efficiencies at mRNA expression levels were 68.9% and 80.7% (IGF-1R gene)

79.5% and 83.3% (BMP2 gene)

respectively

after transfection with IGF-1R-siRNA-1 and IGF-1R-siRNA-2 plasmid (P0.05). The inhibition efficiencies at protein levels were 46.1% and 62.1% (IGF-1R gene

P0.05)

42.5% and 60.9% (BMP2 gene

P0.05)

respectively. The results of MTT growth curve showed that the proliferation rate in the transfected SMMC7721 cells was significantly slower than that in the control group (P0.05). The proportion of apoptotic cells in transfected groups was significantly higher than that in the control group (P0.05). Conclusion: Silencing IGF-1R gene can downregulate the expression of BMP2 gene at different levels that results in inhibition of cell proliferation and promotion of apoptosis in SMMC7721 cells.