Epithelial mesenchymal transition (EMT) is the process by which cancer cells from primary tumors pass through a phenotypic conversion to invade and migrate, generating metastases in distant organs or tissues. EMT can be induced by growth factors such as transforming growth factor beta (TGF-β), responsible for the regulation of differentiation, cell migration, proliferation and apoptosis. Metformin has been considered an inhibitory agent of EMT for supplying the expression of transcription factors in breast cancer cells. Metformin is a hypoglycemic agent used in the treatment of type 2 diabetes, and the use of this drug has been associated with lower incidence of breast cancer.

The aim of this study was to induce, characterize and inhibit the process of EMT by TGF-β in vitro using metformin and identifying molecular markers in the process of metastasis of breast cancer. Three-dimensional cultures of canine mammary tumor cell lines CMT-U229 and CF-41 were treated with different concentrations of metformin associated with TGF-β1 for 48 hours. Western blotting and immunofluorescence techniques were used to analyze the expression of EMT markers E-cadherin, N-cadherin and the tight junction molecule claudin-7. Treatment with metformin 1 mM inhibited the expression of N-cadherin induced by TGF-β1 and increased expression of E-cadherin and claudin-7 in cell lines. Thus it was concluded that the downregulation of N-cadherin, and upregulation of E-cadherin and claudin-7 can be an important contributor to the antimetastatic effect of metformin on breast cancer. Experiments including additional EMT markers and cell lines are underway to confirm these preliminary findings.