ObjectiveTo establish MCF-7 cell lines with different ERα/ERβ expression level and observe their biological behaviors. MethodsERα or ERβ gene were silenced by RNA interference, and the cell lines with different ERα or ERβ expression level were obtained in MCF cell lines. MTT assay, flow cytometry, RT-PCR, double layer softagar clony formation test, and Matrigel adhesion assay were used to detect the abilities of cell proliferation, apoptosis, tumorigenesis, and adhesion. ResultsThe stable expression cell lines with ERαlow/ERβhigh or ERαhigh/ERβlow were established successfully. After ERα gene knockdown, MCF-7 grew slowly and was arrested at phase G0-G1. Apoptosis of MCF-7 was induced and the capacity of tumorigenesis and adhesion in vitro were weakened. However, the characteristics mentioned above except for adhesion changed to the opposite sides after ERβ gene knockdown. ConclusionsThe ERα gene silence can inhibit the formation of tumor, however the ERβ gene silence can promote tumor growth, invasion, and metastasis. Therefore, may be a useful approach on the breast cancer therapy.