Comprehensive bioinformatics analysis and experimental validation revealed that high-expression ARHGAP9 affected the progression of gastric cancer

Background: Gastric cancer is characterized by poor prognosis due to late diagnosis and therapeutic resistance. ARHGAP9, a Rho GTPase-activating protein, regulates cytoskeletal dynamics and MAPK signaling, but its role in gastric cancer progression remains unclear. Methods: Multi-omics data from TCGA, GEO, and cBioPortal were integrated to analyze ARHGAP9 expression, genetic alterations, and immune correlations in gastric cancer. Enrichment analysis, ceRNA network construction, PPI network analysis, immune infiltration assessment (ESTIMATE, CIBERSORT, ssGSEA), and drug sensitivity evaluation (GDSC, CTRP) were performed to elucidate ARHGAP9's role in gastric cancer. In vitro experiments (qRT-PCR, CCK-8, Transwell) with ARHGAP9 knockdown were conducted in gastric adenocarcinoma cell lines (SGC-7901, MGC-803) for functional validation. Results: ARHGAP9 was significantly upregulated in Gastric cancer samples (P < 0.05), correlating with advanced T stage, histological grade, and poor prognosis. Differentially expressed genes between high and low ARHGAP9 groups were enriched in immune-related pathways (BCR signaling). High ARHGAP9 expression was associated with increased CD8 + T cell infiltration and positive correlation with immune checkpoints (PD-1, CTLA4; P < 0.001). Low ARHGAP9 expression enhanced sensitivity to PD-1 inhibitors and chemotherapeutic agents (docetaxel, ribociclib). In vitro knockdown of ARHGAP9 inhibited gastric adenocarcinoma cell proliferation, migration, and invasion (P < 0.05). Conclusion: ARHGAP9 drives gastric cancer progression through immune regulation and serves as a prognostic biomarker. Targeting ARHGAP9 may improve therapeutic response in gastric cancer, particularly in patients resistant to immunotherapy.