Abstract: Background and purpose: More and more evidence has showed that Grb2 binding protein-2 (Gab2) is associated with tumor invasion and metastasis. However, the relationship between Gab2 and epithelialmesenchymal transition (EMT) in breast cancer is not clear. The aim of this study is to investigate the effect of Gab2 on EMT markers and the mechanism of Gab2 on breast cancer invasion and metastasis. Methods: Immunohistochemical methods were used to detect the expressions of Gab2, E-cadherin and vimentin in 80 cases of breast cancer tissues, and the correlations between them were analyzed. Western blot was used to detect the expression of Gab2 in breast tissues. After MDA-MB-231 cells were transfected with siRNA plasmid, wound healing assay was used to detect the invasive ability of transfected cells induced by epithelial growth factor (EGF) in vitro. Then Western blot was used to analyze the protein expressions of E-cadherin, vimentin, phosphorylated GSK-3β (p-GSK-3β) and nuclear Snail. Results: Gab2 was negatively correlated with the expression of E-cadherin and positively correlated with the expression of vimentin in breast cancer tissues (P<0.05). The expression of Gab2 in breast cancer tissues was higher than that in normal breast tissues adjacent to breast cancer. In vitro, Gab2 expression was significantly knocked down in MDA-MB-231 cells transfected with Gab2 siRNA plasmid (SiGab2/MDA-MB-231cells). Meanwhile, the invasive ability of SiGab2/MDAMB-231cells was decreased with EGF stimulation. The expression of E-cadherin was increased in SiGab2/MDA-MB-231cells. However, the expressions of vimentin, p-GSK-3β and nuclear Snail were decreased in SiGab2/MDA-MB- 231cells. Conclusion: Gab2 can promote the invasion and metastasis of breast cancer by EMT through GSK-3β/Snail signaling pathway.

Key words: Breast cancer, Invasion, Grb2 binding protein-2, Epithelial-mesenchymal transition, Signaling pathway