HGF and head and neck squamous cell carcinoma: Transcriptome analysis in HNSCC xenografts and TCGA dataset revealed a significant positive correlation between MET transcript levels and ETS-1 suggesting a possible auto-regulatory loop that may lead to intrinsic MET activation by G-protein-coupled receptors (GPCRs) or other mechanisms independently of HGF such as TGF-β, Src, or MAPK pathways.