Objectives: The "incessant ovulation" hypothesis links increased risk for tubo-ovarian high-grade serous carcinoma (HGSC) due to more ovulations and reduced risk conferred by pre-menopausal exposures like oral contraceptive use, multiparity, and breastfeeding. However, most women diagnosed with HGSC are postmenopausal, implying age is a major risk factor for HGSC. Our mouse model for HGSC, based on tamoxifen (TAM)-induced somatic inactivation of the Brca1, Trp53, Rb1, and Nf1 (BPRN) tumor suppressor genes in oviductal epithelium, recapitulates key genetic, histopathologic, and biological features of human HGSCs. We aimed to credential the model for future efforts to define biological and risk modification factors in HGSC pathogenesis.
Methods: BPRN mice were treated with TAM to induce tumors at defined ages and parity status.
Results: BPRN mice aged 9-months prior to tumor induction had markedly shorter survival than 6-8 week old mice induced to form tumors (median 46.5 weeks versus 61.5 weeks, log-rank test P = 0.0006). No significant differences in cancer phenotypes were observed between multiparous versus nulliparous BPRN mice. However, using a modified tumor model with one wild-type Nf1 allele (BPRNfl/+), nulliparous mice had more advanced tumors than multiparous mice (Mantel-Haenszel Chi-square test of association, P = 0.01).
Conclusions: Our findings show aging is associated with significantly shortened survival post tumor induction in the BRPN model and multiparity delays development and/or progression of HGSC in certain genetic contexts. The findings support relevance of our mouse model to gain mechanistic insights into how known factors exert their protective effects and to test novel approaches for HGSC prevention.
Keywords: Genetically engineered mouse model; High-grade serous carcinoma; Incessant ovulation hypothesis; Ovarian cancer.
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