Increased protein expression of both inducible nitric oxide synthase and cyclooxygenase-2 in human colon cancers.

The present study was conducted to investigate protein levels of inducible NO synthase (iNOS) and cayclooxygenase-2 (COX-2) in human colon cancer tissues. Significant increase of iNOS and COX-2 levels in tumors as compared to paired normal tissue was observed in 15 and 28, respectively, of 29 cases investigated. No correlation was observed between the two enzymes, and immunohistochemically demonstrated iNOS expression was mainly observed in tumor epithelial cells and was higher in well-differentiated than moderately-differentiated adenocarcinomas, while COX-2 expression was mainly detected in stromal cells and higher in Dukes' C and D than Dukes' A and B cases. These results suggest that iNOS and COX-2 have separate roles in colon carcinogenesis, and might both be usefully targeted by chemoprevention.