COX-2 expression during early lung squamous cell carcinoma oncogenesis.

Cyclooxygenase (COX)-2 is implicated in the oncogenesis of many cancers, and COX-2 inhibitors are effective in preventing the development of tumours, such as in colon cancer. Its expression is increased in nonsmall cell lung cancer and is associated with poor prognosis. The present study assessed COX-2 expression in normal bronchial epithelium, as well as in all the putative precursors of squamous cell carcinomas. COX-2 expression was studied by immunohistochemistry in 106 biopsies collected during autofluorescence bronchoscopy in consecutive patients at high-risk for lung cancer. All biopsies corresponding to normal epithelium or low-grade lesions (lesions up to moderate dysplasia) did not show increased COX-2 expression. Lesions were positive for COX-2 in eight out of 14 severe dysplasia patients, eight out of 14 in situ carcinomas and five out of eight invasive carcinomas. A strong statistically significant difference in COX-2 expression was found between normal epithelium or low-grade lesions and high-grade lesions (severe dysplasia or worse). The positive and negative predictive values of COX-2 expression for high-grade lesion were 100% and 82.35%, respectively. In conclusion, bronchial precursors of squamous cell carcinoma showed increased cyclooxygenase-2 expression and were segregated into low- versus high-grade with a high positive predictive value. Thus, cyclooxygenase-2 appears as a potential early marker of squamous cell carcinoma.