Expression of prostaglandin G/H synthase type 1, but not type 2, in human ovarian adenocarcinomas

Prostaglandin endoperoxide synthase (PGHS) is a key rate-limiting-enzyme in prostaglandin biosynthesis. PGHS has recently been shown to be expressed in human colorectal cancers and in experimental cutaneous papillomas and carcinomas. However, PGHS expression has not been investigated in ovarian cancers. The objectives of this study were to determine whether PGHS isoenzymes are expressed in human ovarian cancer and, if so, to identify which isoform is involved (PGHS-1 and/or PGHS-2) and to characterize its cellular localization. Sixteen human ovarian adenocarcinomas were studied by immunohistochemistry using specific antibodies recognizing PGHS-1 or PGHS-2. Results showed that all adenocarcinomas demonstrated the presence of tumor cells expressing PGHS-1 but not PGHS-2. Patterns of staining of tumor cells varied among different types of adenocarcinomas, with cells presenting either a mostly diffuse cytoplasmic immunoreactivity or, alternatively, a staining mainly concentrated around the nucleus. No correlation between the intensity of the immunostaining and the degree of malignancy of tumors could be established (r = -0.03; p>0.05). Immunoblot analysis with PGHS-1-selective antibodies of cell extracts from adenocarcinomas revealed the presence of a characteristic 72,000 M-r immunoreactive band. Therefore, these results show for the first time that PGHS-1 is expressed in human ovarian adenocarcinomas.