HGF and cancer: A plethora of heterotypic signals is able to induce EMT in cancer cells, including transforming growth factor-β1 (TGF-β1), epidermal growth factor (EGF), fibroblast growth factor (FGF), hepatocyte growth factor (HGF), insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF), as well as prostaglandin E2 (PGE2), cytokines, and morphogens such as Wnt, Notch, and Sonic hedgehog (Shh).