Prognostic impact of COX-2 in non-small cell lung cancer: a comprehensive compartment-specific evaluation of tumor and stromal cell expression.

Cyclooxygenase-2 (COX-2) is an enzyme that has been extensively investigated as a prognostic marker in cancer. In non-small cell lung cancer (NSCLC) previous results regarding the prognostic impact of COX-2 expression are inconsistent. Therefore we evaluated the association between transcript levels and overall survival in nine publicly available gene expression data sets (total n = 1337) and determined in situ compartment-specific tumor and stromal cell protein expression in two independent cohorts (n = 616). Gene expression did not show any correlation with clinical parameters or with overall survival. Protein expression in tumor and stromal cells did not correlate with any clinical parameter or with overall survival in one of the analyzed cohorts, while a significant association of high stromal expression with longer survival was observed in both univariate and multivariate analysis in the other cohort. Stromal expression of COX-2 has not been separately evaluated in NSCLC previously and may be a subject of further investigation, whereas the presented findings from this comprehensive compartment specific evaluation clearly reject the hypothesis of COX-2 tumor cell expression having a prognostic value in NSCLC.