EGFR and head and neck squamous cell carcinoma: Cell culture/Cell viability assay/WB/Co-immunoprecipitation assay/Flow cytometry/Glucose measurement assay/ATP measurement assay/Live cell imaging/siRNA knockdown analysis/IHC staining and the scoring of p-AMPK and EGFR from HNSCC specimens/Subcutaneous ectopic xenograft tumor model