CYP1B1 expression in ovarian cancer in the laying hen Gallusdomesticus.

OBJECTIVES: Ovarian carcinoma is the most lethal gynecological malignancy. The genetic and molecular mechanisms that cause it still remain largely unknown. CYP1B1 is a cytochrome P450 enzyme that catalyzes the conversion of estrogens to genotoxic catechol estrogens which may cause DNA mutations and initiate ovarian epithelial cancer. Our objectives were to evaluate CYP1B1 expression, distribution and localization in the hen ovary and to determine if there is an increased CYP1B1 expression associated with, and possibly involved in the initiation of ovarian cancer. METHODS: Two groups of hens were used: 1. young (50 weeks of age; devoid of cancer) and 2. old (165 weeks of age; divided into two groups: age-matched normal and ovarian cancer). CYP1B1 mRNA and protein expression were analyzed in cancerous ovaries, ovaries of age-matched normal and/or young hens by quantitative real-time PCR (qRT-PCR), in situ hybridization (ISH) and immunohistochemistry (IHC). RNA was extracted from tissue preserved in RNAlater for qRT-PCR. Tissue frozen in liquid nitrogen was used for ISH. Tissue fixed in neutral buffered formalin was subjected to IHC. RESULTS: Higher expression of CYP1B1 mRNA was observed in cancerous ovaries as compared to ovaries of young and age-matched normal hens by qRT-PCR. ISH and IHC confirmed that the expression of CYP1B1 was much higher in ovarian tumors compared to ovaries of age-matched normal hens. CYP1B1 mRNA and protein were distributed extensively throughout the carcinoma, while primarily localized to the granulosa layer surrounding the follicle in age-matched normal hens. IHC also showed nuclear localization of CYP1B1. Highly expressed CYP1B1 was found in POF-3 from young and age-matched normal hens as compared to POF-1 and POF-2 by qRT-PCR. No significant difference was found in the expression of CYP1B1 between the distal (site of rupture) and the proximal (site of attachment to the ovary) of POF-1 from young and age-matched normal hens. CONCLUSIONS: High expression of CYP1B1 in the hen ovary is associated with ovarian cancer and our data suggest that CYP1B1 may play an important role in the initiation of ovarian cancer and may prove to be a target for intervention. Moreover, the results of this study further confirm that the laying hen is a good model to study human ovarian cancer.

Cyclooxygenases expression and distribution in the normal ovary and their role in ovarian cancer in the domestic hen (Gallus domesticus).

Cyclooxygenase (COX) (PTGS) is the rate-limiting enzyme in the biosynthesis of prostaglandins. Two COX isoforms have been identified, COX-1 and COX-2, which show distinct cell-specific expression and regulation. Ovarian cancer is the most lethal gynecological malignancy and the disease is poorly understood due to the lack of suitable animal models. The laying hen spontaneously develops epithelial ovarian cancer with few or no symptoms until the cancer has progresses to a late stage, similar to the human disease. The purpose of this study was to examine the relative expression and distribution of COX-1 and COX-2 in the ovaries of normal hens and in hens with ovarian cancer. The results demonstrate that COX-1 was localized to the granulosa cell layer and cortical interstitium, ovarian surface epithelium (OSE) and postovulatory follicle (POF) of the normal ovary. In ovarian cancer, COX-1 mRNA was significantly increased and COX-1 protein was broadly distributed throughout the tumor stroma. COX-2 protein was localized to the granulosa cell layer in the follicle and the ovarian stroma. COX-2 mRNA expression did not change as a function of age or in ovarian cancer. There was significantly higher expression of COX-1 mRNA in the first POF (POF-1) compared to POF-2 and POF-3. COX-2 mRNA expression was not significantly different among POFs. There was no difference in COX-1 or COX-2 mRNA in the OSE isolated from individual follicles in the follicular hierarchy. The results confirm previous findings of the high expression of COX-1 in ovarian tumors further supporting the laying hen as a model for ovarian cancer, and demonstrate for the first time the high expression of COX-1 in POF-1 which is the source of prostaglandins needed for oviposition.