Abstract PR03: Oxidants and antioxidants in the follicular fluid in initiation of fimbriae carcinogenesis

High grade serous carcinoma (HGSC) of the ovary constitutes the majority of incidence and death of ovarian cancer, mainly because of the elusive etiology and cell of origin. Ovulation has been regarded as a strong risk factor and use of oral contraceptives (OC) as a protective factor for ovarian cancer with obvious dose (the span of ovulation life and duration of OC use) effect, but the mechanism is unknown. Meanwhile, more and more evidences have indicated the fallopian tube fimbriae to be the tissue of origin of HGSC. We hypothesize that high level of reactive oxygen species (ROS), which is indispensible for ovulation, as well as abundant mitogens in the mature follicular fluid is responsible for the initiation (DNA double strand breaks, DSB) and promotion (proliferation) of carcinogenesis to the fallopian tube secretory cells. We first tested the scrapped cells of the human fallopian tube epithelium for the extending of DSB. By flow cytometry with gating for the secretory cell marker PAX8 and DSB marker γH2AX, we found the secretory cells in the fimbriae harbored significantly more DSB than the those in the proximal tube. In an immortalized cell line of the human fimbriae secretory cell (we named FE25), we tested the mutagenic and mitogenic effects of the ROS and antioxidant in human follicular fluids at ovulation (FF). We found a balanced activity of of ROS and antioxidants in the undiluted follicular fluid with the antioxidants to be limited, such that, upon serial dilution, the intracellular ROS level raised proportionally. This dilution-raised effect of ROS was able to induce γH2Ax accumulation in the FE25 cells. Upon treating with sub-nM level of melatonin, the most potent and major antioxidant in FF, the level of intracellular ROS and γH2Ax readily decreased. Temporally, we found a two-stage effect of FF on the survival and proliferation of FE25, with an early phase of cell death, which occurred within 12 hours after FF treatment, followed by a cell expansion phase occurring at day 2. We interpret this two-stage effect to be an immediate ROS-induced DSB and cell apoptosis followed by a mitogen-induced proliferation of the survived cells. These survived cells carried the DSB and may be clonally expanded and move on to the carcinogenic road. We conclude that an imbalance favoring the ROS activity in the FF, likely from a significant dilution of FF by an unknown pathological status (such as fimbriae inflammation or ascites), may induce an oxidative stress and DSB in the fallopian tube fimbriae. Cells that survive this stress with some carrying DSB are expanded by the rich mitogens in the same FF. When enough mutations of critical genes were accumulated in a stem cell in this secretory population, cancer lesion such as STIC can thus arise. This abstract is also presented as Poster B5. Citation Format: Hsuan-Shun Huang, Che-Fang Hsu, Taolan Zhang, Tang-Yuan Chu. Oxidants and antioxidants in the follicular fluid in initiation of fimbriae carcinogenesis. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr PR03.