TGFB1 and cancer: Several signaling pathways also participated in the regulation of MET and tumor cell the colonization.266,267 The TGF-β pathway, for example, can induce EMT in various cancer types but can also promote MET and colonization by activating the expression of p63 and other epithelial genes.268 Other signaling pathways, such as Notch, Hedgehog, and Wnt, have also been implicated in the regulation of MET and colonization in various cancer types.269,270 During metastasis, CTCs and the target organ microenvironment engage in a critical dialog that determines the fate of metastatic colonization.