The incidence and mortality of epithelial ovarian cancer (EOC) are increasing in Taiwan and worldwide. The prognosis of this disease has improved little in the last few decades due to insufficient knowledge of the etiology. Previous studies on the role of ovulation in the development of EOC have unveiled IGF2, HGF, and other carcinogens in ovulatory follicular fluid (FF) that exert transformation activities on the exposed fallopian tube fimbria epithelium. However, an orthotopic proof in an animal model is lacking. By using the murine ID8 EOC cells and the syngenic transplantation model, this study explored the effect of FF on the oncogenesis of mouse ovarian cancer. We found FF promoted clonogenicity and anchorage-independent growth of ID8 cells, largely through the IGF-1R and cMET signaling. In contrast, FF modestly promoted cell proliferation independent of the two signals and did not affect cell migration and invasion. Transplantation of ID8 cells into the ovarian bursa of C57BL6/J mice orthotopically grew ovarian tumors and metastasized to the peritoneum with ascites formation. The tumorigenic rate and severity of the disease were positively correlated with the level of IGF-1R and cMET receptors on the cell surface. Our data demonstrated that ovulation, through the signaling of IGF/IGF-1R and HGF/cMET, promotes oncogenic phenotypes in a murine EOC model. The results provide further proof of the carcinogenic effect of ovulation in the development of EOC.
Keywords: Epithelial ovarian cancer (EOC); Follicular fluid (FF); HGF; ID8; IGF2; Ovulation.
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