LAUSR

Background: Gastric cancer (GC) is one of the leading causes of death in the world. Evidence has shown over the past decade that cancer-associated​ fibroblasts (CAFs) play essential roles in various types of cancers, including GC, such as tumorigenesis, therapy resistance, and immunosuppression, which contribute to the progress of tumors. Although GC tumors are known to be enriched with stroma, the molecular mechanisms of how GC tumors foster the fibrotic milieu is still largely unknown. Here we analyzed a large-scale genomic and transcriptomic dataset of GC to identify GC tumor cell-intrinsic factors for developing fibroblast-rich microenvironments​. Methods: We analyzed GC patient samples with gene expression data and copy number variation profiles from the Asian Cancer Research Group (ACRG) (N = 271). The microenvironment cell populations-counter (MCP-counter) method was used for transcriptome deconvolution to estimate the population of fibroblasts and immune cells in GC tumors. Genes with q value < 0.05 and fold change > 1.5 were defined as differentially expressed genes (DEGs) and identified using the Subio Platform. The copy number amplified genes found in more than 3% of the samples were selected as amplified genes. Pathway and process enrichment analysis and protein-protein interaction analysis were performed using Metascape. Results: We analyzed MCP-counter outputs and observed a fibroblast-enriched population with few infiltrations of anti-tumor immune cells, such as CD8 T cells and cytotoxic T cells in GC patients, suggesting the immunosuppressive role of CAFs in the GC tumor. By analyzing 933 DEGs upregulated in fibroblast-high patients, we found 96 genes with frequent copy number amplification that were not listed on the curated stroma and extracellular matrix-related genes and thus potentially tumor cell-intrinsic genes correlated with the abundance of the stroma. Pathway and protein-interaction analyses revealed that G protein-coupled receptor (GPCR) signaling pathway was enriched in these genes, including HTR2A, AGTR1, FZD1, CALCRL, and NBEA with strong correlations between fibroblast score (Spearman's r > 0.55), implying that these signaling in GC tumor cells contribute to promoting fibroblast-enriched microenvironment. Conclusions: Bioinformatic analyses of a publicly available genomic and transcriptomic dataset revealed a fibroblast-rich and immune-excluded population in GC patients. Several GPCR signaling in tumor cells were strongly correlated with fibroblast abundance in tumors, and these signaling pathways have potential roles in promoting the stroma-rich GC microenvironment. Citation Format: Takashi Semba, Yiling Tong, Feng Wei, Atsuko Yonemura, Tadahito Yasuda, Tomoyuki Uchihara, Huaito Wang, Hideo Baba, Takatsugu Ishimoto. Tumor cell-intrinsic factors promoting fibrotic tumor microenvironment in gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5861.