Gastric Signet Ring Cell Carcinoma: Tumor Microenvironment Reprogramming and Novel Therapeutic Targets With Emphasis on <scp>GRIN2D</scp>

Gastric Signet Ring Cell Carcinoma (GSRCC) is an increasingly recognized subtype of gastric cancer, particularly prevalent in South Asian populations and regions within India. This carcinoma is distinguished by its abundant cytoplasmic mucinous cells and aggressive clinical behavior, often affecting younger individuals and leading to a poor prognosis due to its advanced-stage presentation and resistance to standard treatments. A critical factor in its progression is the tumor's uniquely immunosuppressive and stromal-rich microenvironment, characterized by dysfunctional immune infiltrates, activation of cancer-associated fibroblasts, extracellular matrix remodeling, and complement cascade dysfunction. Recent research has highlighted the significance of key biomarkers, including MSMB, AGR2, CLDN18.2, and notably GRIN2D, which play roles in tumor angiogenesis, immune evasion, and metabolic reprogramming. The interaction of these elements contributes to therapeutic resistance and immune escape, thereby reducing the effectiveness of chemotherapy and checkpoint inhibitor immunotherapies. Innovative strategies that integrate stromal-targeting agents, complement modulators, anti-CLDN18.2 antibodies, and novel GRIN2D-targeted therapies, along with precision molecular profiling, offer potential for enhancing patient outcomes. Tailored approaches that incorporate early detection and dynamic biomarker monitoring may ultimately transform GSRCC management toward personalized, evidence-based therapies and prevention.