Abstract

Background Gastric cancer (GC) is a highly prevalent gastrointestinal malignancy with poor prognosis worldwide, and its initiation and progression are closely associated with tumor immune escape. Polygonum cuspidatum , a traditional Chinese medicine, exerts certain anti-tumor activity. However, its key active components and the underlying molecular mechanisms by which they regulate GC immune microenvironment remain to be systematically elucidated. Methods Bioinformatics analysis was performed based on the TCGA and TCMSP databases to screen potential targets of quercetin, an active component of Polygonum cuspidatum . Direct interactions between quercetin and key target proteins were verified by molecular docking, cellular thermal shift assay (CETSA), and drug affinity responsive target stability (DARTS) assay. CCK-8, colony formation, wound healing, Transwell, and flow cytometry were used to evaluate the effects of quercetin and COL3A1 expression on the proliferation, migration, invasion, and apoptosis of GC cells. A direct co-culture system of GC cells and CD8⁺ T cells was established, and the degree of exhaustion and cytotoxic function of CD8⁺ T cells were assessed by flow cytometry, ELISA, and LDH assay. Finally, a mouse allograft tumor model was constructed to verify the anti-tumor effect of quercetin in vivo . Results COL3A1 was identified as a core target gene of quercetin in GC and was highly expressed in GC cells. Quercetin could directly bind to COL3A1, significantly inhibit the proliferation, migration and invasion of GC cells, and promote apoptosis. Mechanistically, COL3A1 upregulated PD-L1 expression by activating the NF-κB signaling pathway, thereby attenuating the anti-tumor function of CD8⁺ T cells. Quercetin reversed COL3A1-mediated NF-κB activation and PD-L1 upregulation, restoring the cytotoxicity of CD8⁺ T cells against GC cells. Conclusion This study reveals the molecular mechanism by which quercetin directly targets COL3A1 and inhibits the CO