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ABSTRACT Background Gastric cancer (GC) is a major health concern worldwide. One important contributing factor is the presence of the Epstein‐Barr virus (EBV). However, the molecular pattern of how EBV participates in the malignant transition process remains unclear. Methods GC samples were stained by immunohistochemistry, fluorescent and EBV‐encoded small RNA in situ hybridization to identify CD8 expression, CDKN2A genomic alteration, and EBV existence. Functional potentials of EBV infection were predicted by bioinformatic enrichment analysis. Results CDKN2A genestayed intact in all EBV‐associated GC cases. Meanwhile, CDKN2A deletion (8.43% cases) was exclusive to EBV‐negative GC cases. Furthermore, EBV infection was positively correlated with CD8+T cell infiltration, and both of them predicted better prognosis. Conclusion This study highlighted the comprehensive impact of EBV infection in GC formation and proposed a thought‐provoking observation for further investigation into the roles of CDKN2A and EBV infection in gastric tumorigenesis.

Abstract Background Cancer‐associated fibroblasts (CAFs), integral to the tumour microenvironment, are pivotal in cancer progression, exhibiting either pro‐tumourigenic or anti‐tumourigenic functions. Their inherent phenotypic and functional diversity allows for the subdivision of CAFs into various subpopulations. While several classification systems have been suggested for different cancer types, a unified molecular classification of CAFs on a single‐cell pan‐cancer scale has yet to be established. Methods We employed a comprehensive single‐cell transcriptomic atlas encompassing 12 solid tumour types. Our objective was to establish a novel molecular classification and to elucidate the evolutionary trajectories of CAFs. We investigated the functional profiles of each CAF subtype using Single‐Cell Regulatory Network Inference and Clustering and single‐cell gene set enrichment analysis. The clinical relevance of these subtypes was assessed through survival curve analysis. Concurrently, we employed multiplex immunofluorescence staining on tumour tissues to determine the dynamic changes of CAF subtypes across different tumour stages. Additionally, we identified the small molecule procyanidin C1 (PCC1) as a target for matrix‐producing CAF (matCAF) using molecular docking techniques and further validated these findings through in vitro and in vivo experiments. Results In our investigation of solid tumours, we identified four molecular clusters of CAFs: progenitor CAF (proCAF), inflammatory CAF (iCAF), myofibroblastic CAF (myCAF) and matCAF, each characterised by distinct molecular traits. This classification was consistently applicable across all nine studied solid tumour types. These CAF subtypes displayed unique evolutionary pathways, functional roles and clinical relevance in various solid tumours. Notably, the matCAF subtype was associated with poorer prognoses in several cancer types. The targeting of matCAF using the identified small molecule, PCC1, demonstrated promising antitumour activity. Conclusions Collectively, the various subtypes of CAFs, particularly matCAF, are crucial in the initiation and progression of cancer. Focusing therapeutic strategies on targeting matCAF in solid tumours holds significant potential for cancer treatment.

Abstract Background Gastric cancer (GC) is one of the most common tumours in East Asia countries and is associated with Helicobacter pylori infection. H. pylori utilizes virulence factors, CagA and VacA, to up‐regulate pro‐inflammatory cytokines and activate NF‐κB signaling. Meanwhile, the PIEZO1 upregulation and cancer‐associated fibroblast (CAF) enrichment were found in GC progression. However, the mechanisms of PIEZO1 upregulation and its involvement in GC progression have not been fully elucidated. Methods The CAF enrichment and clinical significance were investigated in animal models and primary samples. The expression of NF‐κB and PIEZO1 in GC was confirmed by immunohistochemistry staining, and expression correlation was analysed in multiple GC datasets. GSEA and Western blot analysis revealed the YAP1‐CTGF axis regulation by PIEZO1. The stimulatory effects of CTGF on CAFs were validated by the co‐culture system and animal studies. Patient‐derived organoid and peritoneal dissemination models were employed to confirm the role of the PIEZO1‐YAP1‐CTGF cascade in GC. Results Both CAF signature and PIEZO1 were positively correlated with H. pylori infection. PIEZO1, a mechanosensor, was confirmed as a direct downstream of NF‐κB to promote the transformation from intestinal metaplasia to GC. Mechanistic studies revealed that PIEZO1 transduced the oncogenic signal from NF‐κB into YAP1 signaling, a well‐documented oncogenic pathway in GC progression. PIEZO1 expression was positively correlated with the YAP1 signature (CTGF, CYR61, and c‐Myc, etc.) in primary samples. The secreted CTGF by cancer cells stimulated the CAF infiltration to form a stiffened collagen‐enrichment microenvironment, thus activating PIEZO1 to form a positive feedback loop. Both PIEZO1 depletion by shRNA and CTGF inhibition by Procyanidin C1 enhanced the efficacy of 5‐FU in suppressing the GC cell peritoneal metastasis. Conclusion This study elucidates a novel driving PIEZO1‐YAP1‐CTGF force, which opens a novel therapeutic avenue to block the transformation from precancerous lesions to GC. H. pylori‐NF‐κB activates the PIEZO1‐YAP1‐CTGF axis to remodel the GC microenvironment by promoting CAF infiltration. Targeting PIEZO1‐YAP1‐CTGF plus chemotherapy might serve as a potential therapeutic option to block GC progression and peritoneal metastasis.