Abstract B26: The natural history of ovarian high-grade serous carcinoma from time effects of ovulation inhibition and progesterone clearance of p53-defective lesions

Abstract

Abstract High-grade serous carcinoma (HGSC) is the most common and devastating type of ovarian cancer; its etiology, mechanism of malignant transformation, and origin remain controversial. Recent studies have identified secretory cells at the fimbria of the fallopian tube as the cell of origin of HGSC, initiating TP53 mutation, evolving to tubal precursor lesions, including “p53 signature” and serous tubal intraepithelial carcinoma (STIC), and metastasizing to the ovary as clinically evident ovarian cancer. The etiologic mechanisms associated with the known epidemiologic risk factors, i.e., ovulation and retrograde menstruation, have also been unveiled. Mutagens and transforming growth factors, such as reactive oxygen species and IGF axis proteins, as well as the apoptosis-rescuing protein hemoglobin are abundantly present in the ovulatory follicular fluid and peritoneum fluid, which bathes the fimbrial epithelium, and induces malignant transformation after repeated exposure. Meanwhile, in accordance with the proposed therapeutic effect of progesterone from studies on oral contraceptive (OC) use or term pregnancy, our recent study indicated that the p53-null tubal epithelial cells are selectively cleared by progesterone depending on its progesterone receptor (PR). In this report, by analyzing different time-effects of OC use or pregnancy in the prevention of ovarian cancer and by aligning them with the carcinogenic and therapeutic clearance concepts of ovulation and P4, as well as the fact of progressive loss of PR during tubal transformation, we deduced the natural history of ovarian HGSC. The natural history begins at the first ovulation and spans more than 30 years, taking 10 years from the normal tubal epithelium to the “p53 signature” status, another 15 years to PR(-) STIC, and a final 5+ years to HGSC. The estimated natural history may help understand the pathogenesis of HGSC and defines the window for early detection and chemoprevention. Citation Format: Tang-Yuan Chu, Na-Yi Yuan Wu, Jing Wang. The natural history of ovarian high-grade serous carcinoma from time effects of ovulation inhibition and progesterone clearance of p53-defective lesions [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr B26.