Role of epidermal growth factor receptor in feline oral squamous cell carcinoma

Abstract

Feline oral squamous cell carcinomas (FOSCCs) are locally aggressive tumours and a common cause of mortality and morbidity. Current treatment options are rarely successful and animals are frequently euthanised upon diagnosis due to their grave prognosis. Epidermal Growth Factor Receptor (EGFR) is a tyrosine kinase receptor which is frequently dysregulated in SCC of the head and neck (HNSCC) in man. Recent advances in human medicine have identified EGFR as a therapeutic target in HNSCC. In this study the role of EGFR in FOSCC was investigated. Sixty seven biopsy samples were immunohistochemically labelled for EGFR and Ki67, a proliferation marker. The tyrosine kinase region of feline EGFR was cloned and sequenced, and six small interfering RNAs (siRNAs) targeting the tyrosine kinase region were developed. The most effective siRNA as well as an EGFR specific tyrosine kinase inhibitor, gefitinib, was then used on a feline SCC cell line (SCCF1), and the effect of EGFR targeting alone, or in combination with irradiation, on the cell line was determined. The majority of the biopsy samples were labelled positively for EGFR and Ki67, and high proliferation corresponded with poor prognosis. The siRNA caused reduction in EGFR mRNA by Real-Time Polymerase Chain Reaction and protein levels as assessed by western blot analysis. Reduced cell proliferation and migration were also observed by proliferation assays and scratch assays respectively. Combining EGFR knockdown with irradiation caused an additive effect on the ability of the cell line to form colonies. These results support the role of EGFR as a potential therapeutic target in FOSCCs.