MMP9 and breast cancer: The PI3K/AKT is one of the most important signaling pathways that mediates the process of EMT through (i) direct activation of transcription factors (twist 1, 2) which increases the expression of mesenchymal markers (N-cadherin), decreases the expression of epithelial markers (E-cadherin, claudin, occluding) and upregulates AKT gene, which is involved in drug resistance in breast cancer, (ii) increased activity of integrin-linked kinase (which downregulates E-cadherin) and (iii) activation of matrix-degrading proteases (MMP2, MMP9) [55,174].