Abstract 5075: Transcriptomic landscape of tumor microenvironment in gastric cancer in treatment with different types of cancer drugs

Abstract Gastric cancer (GC) in the fifth-leading types of cancer and the third-leading cause of death from cancer. Characterization of tumor microenvironment (TME) in GC is important not only to comprehensively understand tumor biology in GC but also to develop a novel cancer therapeutics targeting TME. In this study, we conducted multi-omics analyses of single-cell RNA sequencing (scRNA-seq), bulk RNA sequencing (bulk RNA-seq), and whole exome sequencing (WES) using biopsied tumor samples through endoscopy from 23 GC patients: 3 treatment-naïve patients, 7 patients in treatment with chemotherapy (Chemo), 5 patients in combination treatment with chemotherapy and immune checkpoint blockade (Chemo+CPI), 3 patients in combination treatment with chemotherapy and Her2-antibody targeted therapy (Chemo+Her2i), and 5 patients in third-line or later treatment. We initially classified the GC samples into 4 molecular subtypes (CIN, GS, MSI, and EBV) using datasets of WES, bulk RNA-seq and scRNA-seq, showing that our samples were mainly composed of CIN (n=7) and GS (n=16) types. In scRNA-seq, we revealed that drug treatments profoundly modulated not only proportions of TME components but also their molecular characteristics. For instance, Chemo+CPI treated patients showed higher proportion of CD8+ cytotoxic T cells with activation and/or exhaustion markers. Combination treatments with Chemo+Her2i, in addition, resulted in higher Trail and Estrogen signaling pathways in epithelial cells of TME components. These findings suggest that interventions with certain cancer therapeutic drugs could substantially convert transcriptome landscape and reconstitute GC TME components. High-resolution of GC TME analyses should provide a clue for developing a next generation of cancer therapeutic drugs. Citation Format: Hiroki Yamashita, Jason Guoqiang Zhang, Chiaki Mashima, Ryo Kamata, Tomoko Yamamori, Izuma Nakayama, Akihito Kawazoe, Kohei Shitara, Tomonori Yano, Qunli Xu, Akihiro Ohashi, Takeshi Saito. Transcriptomic landscape of tumor microenvironment in gastric cancer in treatment with different types of cancer drugs [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 5075.