Hsuan-Shun Huang

Ovulation releases G-CSF to induce peritoneal neutrophil influx and netosis, facilitating peritoneal seeding of high-grade serous carcinoma

High-grade serous ovarian cancer (HGSC), the most lethal subtype of epithelial ovarian cancer (EOC), often originates from serous tubal intraepithelial carcinoma (STIC) and is typically diagnosed at advanced stages. However, the mechanisms underlying the dissemination of STIC cells into the peritoneal cavity remain poorly understood. This study aims to clarify whether the immune microenvironment triggered by physiological ovulation contributes to this early metastatic process. We investigated the link between ovulation-induced peritoneal neutrophil extracellular trap (NET) formation, NETosis, and cancer cell seeding. Peritoneal fluid from humans and mice at various ovulatory stages was analyzed for immune cell composition. NETosis was assessed by neutrophil DNA staining and detection of PAD4 and citrullinated histone H3 (CitH3). STIC-mimicking and HGSC cells were used with or without NET inhibition to evaluate effects on early metastatic seeding. Ovulatory follicular fluid (FF) robustly induced peritoneal neutrophil recruitment and rapid NET formation via a G-CSF-mediated, ROS/NOX/PAD4-dependent mechanism. NETs promoted cell clustering and anchorage-independent growth through extracellular DNA, while NET-derived soluble factors enhanced cell adhesion and invasion. In vivo, exposure to FF enhanced early intraperitoneal tumor cell seeding, which was significantly reduced by PAD4 inhibition. Physiological ovulation induces neutrophil influx and NETosis, creating a pro-metastatic peritoneal niche that facilitates both the dissemination and transformation of STIC cells. These findings reveal a novel mechanism linking ovulation to HGSC progression and suggest NETosis as a potential target for early intervention.

Ovulation-derived extracellular vesicles exhibit sustained oncogenic influence on the exposed fallopian tube fimbrial cells after drainage into peritoneal cavity

Ovulation is known to damage fallopian tube epithelial (FTE) cells, promote cellular transformation, and contribute to the development of high-grade serous ovarian carcinoma (HGSC). While ovulatory follicular fluid-derived extracellular vesicles (EVs) have been shown to possess cell-transforming activity, it remains unclear whether these EVs persist in the peritoneal cavity after ovulation, potentially prolonging their exposure and enhancing their transformative effects on fallopian tube epithelial (FTE) cells. In this study, we collected follicular fluid (FF) and peritoneal fluid (PF) from women before and after ovulation, and investigated the oncogenic potential of ovulation-derived EVs on FTE cells using an anchorage-independent colony growth assay. We found that post-ovulatory PF exhibits significantly higher cell transformation activity compared to pre-ovulatory PF. This heightened activity correlates with an increased concentration of EVs and protein content in post-ovulatory PF. FF samples obtained from different ovulatory follicles of the same patient demonstrated consistent transformation activity, and FF- or post-ovulatory PF derived EVs retained this transforming capacity across FTE cells at varying stages of transformation. Our study reveals a novel mechanism by which ovulation may contribute to FTE transformation through the persistent oncogenic effects of EVs released into the peritoneal microenvironment. This finding provides new perspectives and directions for future cancer prevention, treatment, and potential diagnostic biomarker research.