HGF and cancer: EMT-inducing signals from the tumor-associated stroma such as hepatocyte growth factor (HGF), epidermal growth factor (EGF), placental-derived growth factor (PDGF) and transforming growth factor-beta (TGF-beta) appear to be responsible for the induction or functional activation in cancer cells of a series of EMT-inducing transcription factors such as Snail, Slug, ZEB1, Twist, Goosecoid and FoxC2 [21,28-31].