Objective:To investigate the synoviolin expression in breast cancer tissues and its effects on the proliferation and migration of breast cancer cell line MCF-7. Methods:The expression of synoviolin in breast cancer tissues was detected by Western blotting and immunohistochemical staining. The proliferation and migration of MCF-7 cells were detected by CCK-8 kit assay, wound healing assay,and Transwell migration assay. The overexpression of synoviolin in MCF-7 cells was performed by adenoviral vector transfection. Results:The expression of synoviolin in breast cancer tissue was decreased than that of the corresponding peritumoral tissues;Overexpression of synoviolin inhibited the proliferation and migration as well as epithelial-mesenchymal transition (EMT) of the MCF-7 breast cancer cells. Conclusion:Down-regulation of synoviolin in patients with breast cancer may play a critical role in the proliferation and migration of breast cancer.