Objectives: Cyclooxygenase-1 and 2 (COX-1 and COX-2) play important roles in normal physiology and are often dysregulated in neoplastic tissues. The present study determines whether COX-1 and COX-2 are expressed in ovarian cancers and whether the pattern of expression of these enzymes reveals clues to their roles in this cancer.
Methods: The expression of COX-1 and COX-2 proteins in 9 normal human ovaries, in 137 cases of ovarian cancers of epithelial origin (83 primary and 54 metastatic), and in 7 ovarian cancer cell lines was examined by immunohistochemistry and western analysis.
Results: COX-1 protein was present in 95/137 (69.3%) of the total cancers studied, with 55/83 (66.3%) of the primary cancers and 40/54 (74.1%) of the metastatic cancers positive for protein. COX-2 was present in 97/137 (70.8%) of all cancers studied, with 53/83 (63.9%) of the primary cancers and 44/54 (81.5%) of the metastatic cancers positive for protein. Notably, the quickscores for COX-2-positive staining were significantly higher in metastatic cancers. Moreover, COX-2 immunostaining was frequently found at the advancing margin of tumor invasion or in new metastatic loci. COX-1 protein expression was observed in the ovarian surface epithelial cells, especially that of the inclusion cysts. COX-1 was also detected by western blot in seven of nine ovarian cancer cell lines. However, no COX-2 was detected in either normal epithelium or cancer cell lines.
Conclusion: COX-1 and COX-2 were expressed in every type of ovarian epithelial cancer, suggesting that each may contribute to the cancer development or progression.