INCREASED EXPRESSION OF CYCLOOXYGENASE-2 OCCURS FREQUENTLY IN HUMAN LUNG CANCERS, SPECIFICALLY IN ADENOCARCINOMAS

Cyclooxygenase (COX)-2 expression was immunohistochemically examined i n 59 human lung cancers as well as in normal and premalignant Lung spe cimens. In contrast to scattered weak reactivity seen in normal periph eral airway epithelial cells, markedly up-regulated COX-2 expression w as detected in about one-third of atypical adenomatous hyperplasias an d carcinoma in situ specimens, and a significant increase in COX-2 exp ression was observed in 70% of invasive adenocarcinoma cases. Interest ingly, the proportion of adenocarcinoma cells with marked COX-2 expres sion was much greater in lymph node metastases than in the correspondi ng primary tumors. In contrast, small cell carcinomas showed virtually negligible expression, and squamous cell carcinomas showed infrequent and low expression. These findings suggest that an increase in COX-2 expression may be associated with the development of adenocarcinomas a nd possibly with acquisition of an invasive and metastatic phenotype.