Context: The epidermal growth factor receptor (EGFR), a transmembrane tyrosine kinase (TK) receptor that mediates proliferation and survival signaling, is expressed in a wide variety of normal and neoplastic tissues. EGFR inhibitors (EGFRIs) have produced objective responses in patients with non-small cell lung carcinomas harboring activating EGFR TK domain somatic mutations.

Objective/Methods: Because the EGFR pathway has been reported to be important for the pathophysiology of thyroid carcinoma, we investigated the expression and mutational status of EGFR in 14 thyroid carcinoma cell lines, as well as its functional role by evaluating their in vitro sensitivity to AEE788, a new dual family EGFR/ErbB2 and vascular endothelial growth factor receptor TK inhibitor (Novartis Pharma, Switzerland). We also evaluated the mutational status, mRNA and protein expression, as well as phosphorylation status of EGFR in a panel of thyroid carcinoma specimens.

Results: EGFR expression and phosphorylation in the thyroid carcinoma cell lines and tissue specimens was present, but not stronger than in noncancerous thyroid tissue. EGFR TK domain mutations were detected in 2/62 histological specimens (3.2%), but not in cell lines. All thyroid carcinoma cell lines were significantly less sensitive (IC₅₀ at least 25-fold higher) in vitro to AEE788 than a primary culture of EGFR-mutant lung carcinoma cells.

Conclusions: Thyroid carcinoma cells overall are poorly responsive to clinically relevant concentrations of AEE788 in vitro. The presence of EGFR activating TK domain mutations may identify a small minority of thyroid cancer patients that may benefit from EGFRIs, but additional preclinical evidence of efficacy is needed.