Activation of TGF-β1 Pathway by SCUBE3 Regulates TWIST1 Expression and Promotes Breast Cancer Progression

Background: Recently, signal peptide-CUB-EGF-like domain containing protein 3 (SCUBE3) has been found to be associated with the development of several cancers. However, the biological role of SCUBE3 in breast cancer progression has not been reported. Materials and Methods: Western blotting and quantitative real-time polymerase chain reaction were used to measure the expressions of SCUBE3, TGF-β (transforming growth factor-β) signaling pathway markers, and epithelial-mesenchymal transition markers. The influence of SCUBE3 on the breast cancer cell proliferation, invasion, and migration was detected using methyl thiazolyl tetrazolium, wound healing, colony formation, and transwell assay. The role of SCUBE3 in vivo was confirmed using tumor xenograft experiment. Results: SCUBE3 expression was markedly increased in breast cancer cells and tissues. Knockdown of SCUBE3 suppressed cell growth, invasion, and migration, while SCUBE3 overexpression promoted cell growth, invasion, and migration in breast cancer cells. In addition, TGF-β1 and its downstream proteins were positively regulated by SCUBE3, and the promotion effect on TWIST1 expression induced by pcDNA3.1-SCUBE3 can be reversed by TGF-β1 inhibitor in breast cancer cell lines. Moreover, silencing of SCUBE3 suppressed breast cancer cell growth and tumorigenesis through reducing TGF-β1 in vivo. Conclusion: Knockdown of SCUBE3 downregulated TGF-β1 and TWIST1 expression, thereby inhibiting breast cancer cell growth and tumorigenesis.