Abstract 5200: Extracellular vesicles in the ascites from gastric cancer patients play critical roles to promote peritoneal dissemination in the intraperitoneal cancer microenvironment

Abstract

Abstract Although gastric cancer often develops peritoneal dissemination, the underlying mechanism of peritoneal metastasis is still unclear. Extracellular vesicles (EVs) are known to play roles in cell-cell communication. Here, we investigated the existence of EVs in peritoneal ascites of gastric cancer patients and explored their roles in the intraperitoneal cancer microenvironment. We found that EVs actually existed in peritoneal ascites of advanced gastric cancer patients. On the other hand, immune-fluorescent assay of the ascites by using antibodies against CD14 (Monocytes) and CD45 (Leukocytes) revealed that many macrophages existed along with the cancer cells in the peritoneal cavity. EVs purified from peritoneal ascites with cancer dissemination made peripheral blood mononuclear cells-derived macrophages M2-like phenotype which was confirmed by their morphology and expression of CD163/206 (M2 marker). Next, we purified EVs from the culture medium of gastric cancer cell lines. Gastric cancer-derived EVs induced the M2- differentiation in macrophages and the differentiated macrophages promoted migration ability of gastric cancer cells. Finally, we observed that gastric cancer-derived EVs induced apoptosis of cultured mesothelial cells in vitro. These results suggested that EVs in the ascites of gastric cancer patients are possibly derived from gastric cancer and play critical roles in the intraperitoneal cancer microenvironment by affecting the macrophages phenotype and inducing apoptosis in the mesothelial cells, which would be in part the underlying mechanism of peritoneal metastasis. Citation Format: Atene Ito, shunsuke kagawa, Shuichi Sakamoto, Kazuya Kuwada, Satoru Kikuchi, Shinji Kuroda, Ryuichi Yoshida, Hiroshi Tazawa, Toshiyoshi Fujiwara. Extracellular vesicles in the ascites from gastric cancer patients play critical roles to promote peritoneal dissemination in the intraperitoneal cancer microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5200.