Extrinsic factors, like the multipotent cytokine transforming growth factor β (TGF-β) stimulates EMT in breast cancers [39] and mechanistically, TGF-β stimulation is associated with upregulation of SNAIL, TWIST, ZEB1/2 in luminal A and B breast cancer cell lines [40,41,42]. This evidence concerns the gene SNAI1 and breast cancer.