Tetsuya Tsukamoto

Peritoneal metastasis is the most lethal manifestation of gastric cancer, with a median survival of less than one year, highlighting the need for new therapeutic targets. Through an in vivo genome-wide CRISPR/Cas9 screen, we identified GRIA2, an AMPA-type glutamate receptor subunit, as a key driver of peritoneal metastasis. GRIA2 promotes gastric cancer cell migration, invasion, stemness, and adhesion to mesothelial cells in a glutamate-dependent manner. Mechanistically, glutamate activates GRIA2, enhancing its interaction with GSK-3β and inducing calcium influx, inhibiting GSK-3β kinase activity and stabilizing β-catenin, thereby activating the Wnt/β-catenin signaling pathway. Single-cell RNA sequencing revealed that cancer-associated fibroblasts are the primary source of glutamate in the peritoneal microenvironment, which establishes a paracrine axis that enhances GRIA2-driven metastasis. Pharmacological inhibition of AMPA receptors with NBQX and Selurampanel suppressed peritoneal metastasis in both cell line-derived and patient-derived organoid xenograft (PDOX) mouse models. In clinical analysis, GRIA2 expression in peritoneal metastases correlated with the levels of β-catenin and phosphorylated GSK-3β (serine 9), with high GRIA2 expression predicting poor prognosis. These findings suggest that GRIA2 is a novel therapeutic target, and AMPA receptor antagonists are promising agents for treating gastric cancer peritoneal metastasis.

BACKGROUND: Peritoneal metastasis (PM) is one of the most challenging clinical problems in gastric cancer (GC), largely due to its high recurrence rate and poor response to current therapies. Increasing evidence indicates that remodeling of the extracellular matrix (ECM) plays an important role in therapeutic failure. However, how specific stromal-immune interactions contribute to PM heterogeneity and immunotherapy resistance remains unclear. In this study, we investigated how ECM composition-particularly the accumulation of hyaluronic acid (HA)-influences the immune microenvironment and therapeutic responses in GC-associated PM. METHODS: We combined histopathological assessment, analyses of patient-derived specimens, single-cell transcriptomic profiling, and murine models of PM to delineate ECM remodeling patterns and immune cell dynamics in therapy-sensitive and therapy-resistant lesions. In addition, functional assays and pharmacological approaches were used to examine HA-CD44 signaling and its impact on CD4+ T cell differentiation and responsiveness to immune checkpoint blockade. RESULTS: Therapy-sensitive PM lesions were characterized by enrichment of elastic fibers, whereas therapy-resistant lesions showed collagen accumulation. Notably, HA deposition emerged as a key feature distinguishing these ECM states and was closely associated with differential therapeutic outcomes. Elevated HA levels activated CD44-dependent signaling in CD4+ T cells, driving regulatory T cell (Treg) differentiation through a CD44-IQGAP1-RAC1-SMAD3 signaling pathway and thereby establishing an immunosuppressive microenvironment. Importantly, pharmacological inhibition of CD44 reduced Treg expansion and markedly enhanced the antitumor efficacy of anti-PD-1 therapy in murine PM models. CONCLUSIONS: Our findings identify HA-CD44 signaling as a critical link between ECM remodeling and immune evasion in GC PM. Targeting ECM-driven immunosuppressive mechanisms may represent a promising strategy to overcome therapeutic resistance and improve the efficacy of immunotherapy in this aggressive disease.

Filamentous M13 phages are promising self-adjuvanting nanoparticles for cancer immunotherapy, but their efficacy remains limited by antigen versatility and immune targeting. Here, SCP is developed as an M13 phage-based vector that conjugates antigens via a SpyCatcher-SpyTag interface and presents dendritic cell (DC)-targeting peptides to enhance antigen uptake. SCP activates DCs in vitro, upregulating co-stimulatory markers and inflammatory gene signatures, which subsequently enhances T cell cytotoxicity. In vivo, SCP can be administered subcutaneously as a vaccine adjuvant or intratumourally as a therapy in multiple murine tumour models. SCP induces robust local inflammation, immunogenic cell death, and in situ tumour antigen release, driving tumour-specific cytotoxic T cell responses without requiring predefined neoantigens. Beyond promoting immune infiltration, SCP also reduces neovascularization, downregulates immune checkpoints, and elicits durable systemic immunity to prevent recurrence. Overall, SCP offers a scalable, cost-effective platform for enhancing tumour immunogenicity, bypassing the need for predefined neoantigen selection and exogenous vaccine production.

BACKGROUND: A fibrotic tumor microenvironment (TME) promotes tumor progression by the interactions between tumor cells and cancer-associated fibroblasts (CAFs) in the extracellular matrix (ECM), which enhance tumor cell survival and growth, and by suppressing antitumor immunity. However, how characteristic gene expression and amplification in cancer cells drive the formation of a fibrotic TME in patients with gastric cancer (GC) is unclear. METHODS: We performed genomic and transcriptomic analyses via datasets from The Cancer Genome Atlas and the Asian Cancer Research Group to identify amplified and overexpressed genes associated with the presence of a fibrotic TME in tumors. Syngeneic mouse models of GC and multiplexed immunohistochemistry (IHC) were used to validate the findings of the transcriptomic analysis and investigate the underlying mechanisms. RESULTS: The Frizzled class receptor 1 (FZD1) gene was frequently amplified and highly expressed in GC patients with fibrotic tumors, and FZD1 expression was related to a poor prognosis. The overexpression of Fzd1 in murine GC tumor cells was significantly associated with enhanced tumor fibrosis and growth and reduced infiltration of CD3+ lymphocytes and CD8+ T cells into tumors. SLIT2 secretion was increased in Fzd1-overexpressing tumor cells via the canonical WNT-β-catenin pathway, and SLIT2 activated CAFs to produce more ECM through the SLIT2‒ROBO1 axis. CONCLUSIONS: This study highlights the potential of FZD1 as a biomarker for predicting fibrotic status in patients with GC and the SLIT2‒ROBO1 axis as a therapeutic target to reverse a fibrotic and immunosuppressive TME.