Abstract 1527: Intraperitoneal myeloid-derived suppressor cells in peritoneal dissemination mouse model

Abstract

Abstract Background: Myeroid-derived suppressor cells (MDSCs) are heterogeneous cell populations derived from bone marrow, and two subsets of M-MDSC and PMN-MDSC are known in mice. They accumulate in the tumor-bearing host, and suppresse cell-mediated immunity mainly on T cells, and inhibit anti-tumor immune responses. We have previously reported that (1) the increase of MDSCs in lung, peripheral blood, and spleen reflects the cancer progression, (2) MDSCs in peripheral blood would be useful as a marker of recurrence as it increases in recurrent cases after surgical resection. On the other hand, no detailed report on the dynamics of intraperitoneal MDSCs has been made. In this study, we made peritoneal dissemination mouse models and monitored intraperitoneal MDSCs, and investigated whether MDSCs are involved in the progression of peritoneal dissemination. Methods: MC38 colon cancer cell line was intraperitoneally injected to C57BL / 6J mice and the change in the number and ratio of immune cells (MDSC, Macrophage, T-cell, B-cell) in the spleen, peripheral blood and peritoneal cavity was monitored over time. We examined the correlation between transition of immune cells and cancer progression. Results: MDSCs increased with cancer progression in all spleen, peripheral blood, and intraperitoneal cavity. The proportion of PMN-MDSCs in MDSCs increased in peripheral blood. In contrast, the proportion of M-MDSCs increased initially, then the PMN-MDSCs increased in the abdominal cavity. Conclusion: Intraperitoneal MDSCs were thought to reflect the progression of peritoneal dissemination as well as spleen and peripheral blood. The proportion of M-MDSCs reflects the disease state in the microperitoneal dissemination with serous ascitic fluid, and ascites became bloody and the proportion of PMN-MDSCs increased with the progression of seeding. We are examining treatment for peritoneal dissemination with this feature in mind. Citation Format: Yutaka Sugita, Kimihiro Yamashita, Rishu Takimoto, Tomoko Tanaka, Akira Arimoto, Eiji Fukuoka, Tetsu Nakamura, Satoshi Suzuki, Yoshihiro Kakeji. Intraperitoneal myeloid-derived suppressor cells in peritoneal dissemination mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1527.