KRAS and head and neck squamous cell carcinoma: The following known hallmarks of HNSCC have been described: TP53, EGFR and K-ras mutations; TGF-α, VEGF, PDGF, FGF-1, PI3K, AKT and MDM2 protein overexpression; and PTEN, pRb and NOTCH-1 downregulation [42,43,44].