Abstract 1561: Identification of tumor-associated macrophages promoting early-stage metastasis during peritoneal dissemination in gastric cancer

Abstract Peritoneal dissemination (PD) is the most frequent metastasis pattern in gastric cancer (GC) and is a significant predictor of poor prognosis. However, the mechanisms underlying PD formation remain unclear, and a PD-specific signature has not been identified. PD development is thought to be influenced by various changes occurring in GC tumor cells and immune cells present in the peritoneal cavity. We previously performed RNA-seq analysis of cell components in cytology-positive (CY1) gastric cancer ascites. The results suggested that tumor-associated macrophages (TAMs) infiltrate the abdominal cavity together with GC tumor cells and might be involved in PD development. In this study, we aimed to identify the specific TAMs responsible for promoting metastasis during the early stage of PD in GC. We demonstrated the abundant presence of TAMs in CY1 GC ascites using flow cytometry analysis and identified several genes that were significantly expressed in CY1 TAMs using single-cell RNA-seq analysis. Furthermore, we evaluated the potential of these genes to serve as therapeutic targets for the treatment of PD in GC. Citation Format: Wataru Kawase, Yukihiko Hiroshima, Itaru Hashimoto, Shizune Onuma, Mitsuhiro Furuta, Nozomu Machida, Takashi Oshima, Yohei Miyagi. Identification of tumor-associated macrophages promoting early-stage metastasis during peritoneal dissemination in gastric cancer [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 1561.