Effect of a selective cyclooxygenase-2 inhibitor, nimesulide, on the growth of lung tumors and their expression of cyclooxygenase-2 and peroxisome proliferator- activated receptor-gamma.

PURPOSE: The objectives of this study were to evaluate the effect of a cyclooxygenase (COX)-2 inhibitor, nimesulide, on the growth inhibition of s.c. human lung A549 adenocarcinoma tumors and to assess the effect of nimesulide on the expression of COX-2 and peroxisome proliferator-activated receptor (PPAR)-gamma in lung tumors harvested from mice. EXPERIMENTAL DESIGN: Female nu/nu mice were xenografted with s.c. A549 lung tumors, and 1 day after tumor implantation, the mice were fed with a diet containing nimesulide at 250-1500 ppm doses. Tumor dimensions were monitored twice weekly, and tumor samples isolated from mice were used to determine prostaglandin E(2) (PGE(2)) levels by enzyme immunoassay, expression of COX-2 and PPAR-gamma by Western blotting and immunohistochemistry. Furthermore, the induction of apoptosis in tumor specimens was determined by terminal deoxynucleotidyl transferase-mediated nick end labeling staining. RESULTS: Nimesulide treatment showed a dose-dependent growth-inhibitory effect of A549 tumors with a maximum of 77.7% inhibition at 1500 ppm of nimesulide. Western blotting experiments showed similar expression of COX-2 in both control and nimesulide (250-1500 ppm)-treated mice tumor tissues. PPAR-gamma was found to be overexpressed as a result of 1500 ppm nimesulide treatment and was not detected in tumors from control or 250-1000 ppm nimesulide-treated mice. Nimesulide (1500 ppm) significantly reduced intratumor PGE(2) levels (P < 0.001) and induced apoptosis in 25% of tumor cells as compared with control tumors. CONCLUSIONS: Nimesulide (1500 ppm) induced growth inhibition of A549 lung tumors is associated with the reduction of intratumor PGE(2) levels but without affecting the expression of COX-2. Nimesulide-induced enhancement of the expression of PPAR-gamma may also contribute to its antitumor effect, which needs to be further investigated.