In Vivo CRISPR Screening Identifies the Glutamate Receptor GRIA2 as Promoting Peritoneal Metastasis of Gastric Cancer via Calcium‐Dependent β‐Catenin Activation

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.