Epidermal Growth Factor Receptor Tissue Expression Level as a Predictor for the Aggressiveness of HPV-associated Laryngeal Carcinoma

Abstract

This study was designed to evaluate the frequency of human papilloma virus (HPV) infection in patients with laryngeal squameous cell carcinoma (LSCC) through identification of the viral DNA using PCR analysis and to determine the tissue levels of epidermal growth factor receptor (EGFR) as a trial tofind a relation between HPV infection, EGFR expression and clinicopathological findings in patients with LSCC. The study comprised 32 patients with suspected LSCC; 25 males and 7 females; with mean age 53.3±12.2; range: 25-72 years. All females and 5 males were non-smokers; while 20 males were smokers. Patients were subjected to full history taking and clinical examination. Direct laryngoscopy was performed under light general anesthesia in the operating room for evaluation of the larynx and the entire upper aerodigestive tract for accurate clinical staging according to TNM classification, to determine the full extent of the local spread of the tumor and to obtain tissue biopsy. Fresh tumor tissue specimens were divided into two parts, the first was studied and graded pathologically according to World Health Organization (WHO) classification and the second was stored at -70oC untilprocessed and examined by PCR technique for the presence of HPV-DNA and analyzedfor EGFR expression expressed as femto-mol/mg (fM/mg) protein. Squameous cell carcinoma was detected in 29 cases (90.6%) and 3 cases were excluded off the study; 21 patients (72.4%) had lesions clinically staged as stage I, while 3 (10.3%) and 5 (17.3%) had lesions of stages II and III, respectively. Patients had Stage I lesions were significantly (p<0.05) younger than patients with stage II and III lesions and 9 lesions were detected in non-smokers. Laryngoscopy defined 23 (79.3%) glottic lesions, 2 (6.9%) supraglottic and 3 (10.3%) subglottic lesions and one case (3.4%) had an extensive squamous cell carcinoma of the larynx involving the subglottic region,the glottis and the supraglottic areas. There were 21 (72.4%) polypoid lesions and 8 (27.6%) ulcerative lesions. According to WHO classification, 14 specimens were type 1, 9 specimens type 2 and 6 specimens were type 3. PCR could detect HPV-DNA in 16 (55.2%) specimens (viral specimens) and could not be detected in the other 13 specimens (non-viral cases). Four specimens of WHO type 1, 6 specimens ofWHO type 2 and 6 specimens of WHO type 3 were viral specimens. Mean tissue expression level of EGFR was 37.7±32.2 fM/mg protein and was significantly higher in viral (54.7±27.8 fM/mg protein) compared to non-viral cases (16.8±24.6 fM/mg protein) and in specimens of WHO type 2 and 3 compared to those of type 1. Moreover, there was a positive significant correlation between the pathological WHO types and presence of viral infection, (r=0.568, p=0.001) and the tissue expression levels of EGFR, (r=0.720, p<0.001) and a positive significant correlation between tissue expression of EGFR and the presence of viral infection, (r=0.595, P=0.001). Using the receiver operating characteristic (ROC) curve analysis judged by the area under the curve (AUC) to determine the specificity of the presence of HPV infection and tissue expression of EGFR as a predictor of cancer aggressiveness manifested as WHO pathological stage revealed that tissue expression of EGFR is more specific (AUC=0.731) than the presence of viral infection (AUC=0.583). It could be concluded that laryngeal infection with HPV may predispose to carcinogenesis through activation of certain growth factors as EGF and both were found significantly correlated with the aggressiveness of LSCC with the level of tissue expression of EGFR being a specific determinant of tumor aggressiveness manifested as pathologic stage.