Study of inflammatory signalling in epithelial ovarian cancer and the normal human mesothelium

Abstract

Epithelial Ovarian Cancer (EOC) kills more women annually in the United Kingdom than any other gynaecological cancer. Survival rates for women diagnosed with EOC have not improved over the past 30 years, due to the often advanced stage at presentation, where widespread intra-peritoneal dissemination has occurred. The natural history of the disease remains uncertain but the ovarian surface epithelium (OSE) is a strong candidate for the tissue of origin. The OSE undergoes cyclical damage and repair in women of reproductive age following ovulation, which can be considered an acute inflammatory event. Factors that prevent ovulation (pregnancy, breastfeeding and contraceptive pill use) also protect against the development of EOC. Previously published data show that the OSE is able to upregulate the enzyme 11-beta hydroxysteroid dehydrogenase type 1 (11βHSD1) in response to inflammation, the enzyme responsible for converting inactive cortisone to anti-inflammatory cortisol. This thesis hypothesises that 11βHSD isozymes are deregulated in ovarian cancer; that the peritoneal surface epithelium (PSE) is indistinguishable from the OSE in its response to inflammation and should be considered a potential source of some “ovarian cancers”; and finally that the expression of the tumour suppressor gene OPCML (OPioid binding Cell adhesion Molecule-Like) is altered by inflammation. These hypotheses were examined at three levels. Firstly, primary cultures of EOC were established, and glucocorticoid metabolism and the response to inflammation was compared to normal OSE. Results from these investigations reveal that the11βHSD1 response to IL-1α stimulation is impaired in EOC compared to normal OSE at the mRNA level but there is no significant difference when 11βHSD1 enzyme activity is measured in these tissues. When basal levels of 11βHSD1, 11βHSD2 and COX2 are compared amongst untreated samples of EOC and OSE, there was a significant correlation between 11βHSD1 and COX2 mRNA expression (P<0.001). 11βHSD2 mRNA expression was significantly higher in the EOC specimens compared to OSE (P<0.05). Secondly the response to inflammation was compared in primary cultures of human peritoneal surface epithelial (PSE) cells and OSE. The data suggest that the mRNA response to inflammation was similar in OSE and PSE, but that the 11βHSD1 enzyme activity was reduced in PSE (P<0.05), which may result in differences in tissue healing. Finally, the effect of inflammation on the expression of the ovarian cancer associated tumour suppressor gene (TSG), OPCML (OPioid binding Cell adhesion Molecule-Like) and the other members of the IgLON family, was examined in OSE. These results suggest that OPCML mRNA expression can be induced by IL-1α, an effect that is inhibited by cortisol.