Abstract 572: Identifying potential therapeutic targets through gene expression analysis of peritoneal cavity cells in gastric cancer with peritoneal dissemination

Abstract Background: Peritoneal dissemination (PD) is the primary mode of metastasis in gastric cancer (GC) and is strongly associated with a poor prognosis. However, the mechanisms underlying PD formation in GC remain largely unknown.Methods and Results: In this study, we collected peritoneal washings from three cytology-positive (CY1) and five cytology-negative (CY0) gastric cancer patients undergoing laparotomy. We performed RNA sequencing on cell components in the peritoneal washings and identified 13 genes that were differentially expressed and upregulated in the CY1 group. Among these genes, we focused on thrombospondin 1 (THBS1) and 2 (THBS2). We evaluated their expression levels in 317 patients with gastric or gastroesophageal junction cancer who underwent primary curative resection at the Kanagawa Cancer Center between January 2002 and December 2012. Patients were stratified into two groups based on the median expression values of these genes, and Kaplan-Meier analysis was conducted. THBS2 expression was found to be inversely associated with disease-free survival (DFS) (p = 0.041), peritoneal dissemination-specific DFS (p = 0.041), and overall survival (OS) (p = 0.041) in the study cohort. In contrast, THBS1 expression did not exhibit a significant association with any of the aforementioned outcomes.Conclusion: Our results suggest that THBS2 expression in gastric cancer tissues may serve as a useful independent prognostic factor for patients, potentially playing a crucial role in the formation of PD. Citation Format: Yukihiko Hiroshima, Wataru Kawase, Itaru Hashimoto, Shizune Onuma, Hayato Watanabe, Mitsuhiro Furuta, Takashi Oshima, Yohei Miyagi. Identifying potential therapeutic targets through gene expression analysis of peritoneal cavity cells in gastric cancer with peritoneal dissemination [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 572.