Phosphorylated epidermal growth factor receptor and cyclooxygenase-2 expression in localized non-small cell lung cancer

Abstract

The prognostic significance of epidermal growth factor receptor (EGFR) and cyclooxygenase-2 (COX-2) expression remains unestablished, although EGFR and COX-2 are frequently overexpressed in non-small cell lung cancer (NSCLC). Considering the importance of EGFR activation after ligand binding, however, the expression of phosphorylated EGFR (p-EGFR) may have more significance in predicting tumor aggressiveness in NSCLC than either EGFR or COX-2 expression. We studied the relationships between p-EGFR, EGFR, and COX-2 overexpression and examined their association with prognosis in localized NSCLC. The expression of p-EGFR, EGFR, and COX-2 was studied by immunohistochemistry in 77 surgically-resected stage I/II NSCLC cases. EGFR mutational status was determined by sequencing exons 18-21. Correlation of expression with clinical outcome and other biomarkers, including Ki-67 and microvessel density (MVD), was also examined. Out of the 77 patients, EGFR overexpression was observed in 37 (48.1%), p-EGFR expression was found in 22 (28.6%), and COX-2 overexpression was seen in 45 (58.4%). Expression of p-EGFR was associated with COX-2 overexpression (P = 0.047), but not EGFR overexpression or high Ki-67 (P = 0.087 and P = 0.092, respectively). COX-2 overexpression was significantly associated with high Ki-67 (P = 0.011). Expression of p-EGFR correlated with lower disease-free survival (P = 0.045), but not overall survival. Neither EGFR nor COX-2 overexpression was associated with prognosis. p-EGFR appears to be a better indicator for lower disease-free survival than EGFR overexpression itself in localized NSCLC. Pathways other than EGFR activation may influence COX-2 overexpression.