Increased RTK activity can be also induced in melanoma cells by aberrant autocrine or stromal secretion of RTK ligands, such as VEGF, FGF, hepatocyte growth factor (HGF) and insulin-like growth factor-1 (IGF-1) (29,94,95); interestingly, increased VEGF, FGF or HGF concentration in patients’ sera or neoplastic tissue correlated with poor prognosis (29,94). Here, HGF is linked to melanoma.