Abstract 5329: Ovarian cancer predisposes neutrophils to form neutrophil extracellular traps(NETs)

Abstract Objective: Neutrophil extracellular trap (NETs) are neutrophil-derived extracellular DNA released in response to inflammation. In contrast to their primary host-defensive role, NETs have been recently reported to promote cancer progression. The aim of this study is to investigate the role of NETs in ovarian cancer progression. Method: The clinical data of ovarian cancer patients who underwent primary surgery at Osaka University Medical Hospital were retrospectively reviewed (n=340). The relationship between neutrophilia, peritoneal dissemination and prognosis were analyzed. Prior to initial treatment, peripheral blood was obtained from newly diagnosed ovarian cancer patients and examined for CBC and granulocyte-colony stimulating factor (G-CSF) concentration by ELISA. To evaluate NETs formation capacity, isolated neutrophils were stimulated with G-CSF and incubated in vitro to monitor NETs formation. The ascites was collected at the initial surgery and assessed for G-CSF concentration and for neutrophils population using flow cytometry. The omental tissues were pathologically examined for NETs using H&E-staining and immunostaining with anti-Citrullinated Histon3 (CitH3) antibody. To test NETs induction capacity, we treated human peripheral blood neutrophils with the conditioned media from 20 ovarian cancer cell lines and the serum from ovarian cancer patients. Then human ovarian cancer OVCAR8 cells were co-cultured with NETs to evaluate the effect of NETs on cancer cell adhesion. Results: Neutrophilia (neutrophils>7000/µl) was found in 39 patients (39/340,11.5%). Patients with neutrophilia were associated with advanced disease accompanied by peritoneal dissemination and compromised survival compared to patients without neutrophilia (5-year PFS 40.0 vs 59.9 %, p 0.0027). In these patients, serum G-CSF was upregulated. Neutrophils from ovarian cancer patients formed NETs significantly earlier than those from benign tumor patients. Ovarian cancer patients with neutrophilia showed elevated G-CSF concentration and increased neutrophils proportion in their ascites. Omental tissues from patients with neutrophilia showed NETs foci close to the disseminated lesions. G-CSF strongly induced neutrophils to form NETs in vitro, which was observed in some conditioned media from ovarian cancer cell lines and serum from ovarian cancer patients as well. The adhesion of ovarian cancer cell was increased by co-incubation with NETs. Conclusion: Neutrophilia is associated with peritoneal dissemination and poor prognosis in ovarian cancer. One of the underlying mechanism of neutrophilia is upregulated G-CSF, which stimulate neutrophils to form NETs. NETs may have a causative effect on ovarian cancer dissemination. Citation Format: Gaku Yamamoto, Mahiru Kawano, Michiko Bun, Koutaro Shimura, Aska Toda, Koji Nakamura, Yasuto Kinose, Michiko Kodama, Kae Hashimoto, Kenjiro Sawada, Tadashi Kimura. Ovarian cancer predisposes neutrophils to form neutrophil extracellular traps(NETs) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5329.