Difference in expression of EGFR, pAkt, and PTEN between oropharyngeal and oral cavity squamous cell carcinoma

Abstract

The aims of this study were to evaluate the expression of EGFR, PI3K, Akt, mTOR, and PTEN in the oral cavity and oropharyngeal cancers, and to investigate their clinical significance as prognostic markers. One hundred twenty-one patients who underwent curative surgery for oral cavity or oropharyngeal squamous cell carcinoma in Seoul St. Mary's Hospital between January 1995 and September 2009 were evaluated. The level of protein expression of EGFR, PIK3CA, pAkt, mTOR, and PTEN was assessed by immunohistochemistry. In situ hybridization was used to detect the existence of human papillomavirus (HPV). Nineteen of 61 patients with oropharyngeal cancer showed HPV-positive tumors, and two of 60 patients with oral cavity cancer showed HPV-positive tumors. EGFR and pAkt expression was significantly higher in oral cavity cancers than in oropharyngeal cancers. Loss of PTEN occurred significantly more frequently in oral cavity cancers than in oropharyngeal cancers. The expression levels of PIK3CA, mTOR, and p53 did not differ significantly between the two cancers. Overexpression of EGFR and pAkt and loss of PTEN were observed more frequently in HPV-negative tumors. Multivariate Cox regression analysis showed that pAkt expression had a significantly unfavorable impact on relapse-free survival in oropharyngeal cancer. We conclude that the expression levels of EGFR, pAkt, and PTEN differ between oropharyngeal and oral cavity cancer and it may be attributed to HPV-related molecular pathogenesis. The expression of pAkt might be an unfavorable prognostic marker for relapse-free survival in oropharyngeal cancer.