Previous studies have linked COX-2 to the EMT process: COX-2 overexpression has been associated with upregulation of mesenchymal markers and downregulation of epithelial markers (41); and in breast cancer, COX-2 induced production of PGE2 inhibited Smad signalling thereby enhancing EMT progression and metastasis (42). Here, PTGS2 is linked to breast cancer.