After the interaction of those epithelial breast cancer cells with MDA-ECM for 72 h, we observed a decrease in E-cadherin expression and an increase in N-cadherin and other mesenchymal markers, such as α-SMA, vimentin, fibronectin, and TWIST. These molecular changes were accompanied by loss of cell-cell contacts and increasing migratory capacity of MCF-7 cells. This evidence concerns the gene ACTA1 and breast carcinoma.