While the EGFR specific TK inhibitor erlotinib and the RAS inhibitor zoledronic acid significantly decreased in vitro proliferation of the two HNSCC cell lines both in serum-containing and serum-free media (Figures 2A,B), interestingly, the therapeutic anti-EGFR antibody cetuximab showed no effect on cancer cell proliferation either in the case of the PE/CA-PJ15 cell line harboring the R521K EGFR polymorphism or in the homozygous wild type PE/CA-PJ41 cells. This evidence concerns the gene TKT and head and neck squamous cell carcinoma.