To further investigate whether the expression of HER3 alone is sufficient to mediate resistance to cetuximab, two HNSCC cell lines that are sensitive to cetuximab and express little or no endogenous HER3 were manipulated to overexpress HER3 and treated with cetuximab for cell proliferation analysis (Fig. 3). The gene discussed is ERBB3; the disease is head and neck squamous cell carcinoma.