HGF and head and neck squamous cell carcinoma: For example, a number of studies reported that VEGF [189], Receptor for Advanced Glycation End products (RAGE) [190], Platelet-derived Growth Factor Receptor PDGFR) [191], Hepatocyte growth factor/c-met (HGF/HGFR) signaling [192,193,194], Tumor Growth Factor 1(TGF-1)-Throbospondin-1(THBS-1) axis [195], Notch signaling [196] and Wnt signaling [197] molecules serve as tumor stroma specific factors and have a great impact in regulating the HNSCC malignancy.