TY - EJOU AU - Liu, Jin AU - Zhang, Xiu AU - Hu, Xiao AU - Yuan, Gaofeng AU - Chen, Kai TI - CLDN9 Levels Influence the Biological Activities of Cells in Gastric Cancer T2 - BIOCELL PY - 2025 VL - 49 IS - 4 SN - 1667-5746 AB - Objective: This study examines the significance and functions of CLDN9 in gastric cancer (GC), intending to identify novel targets for diagnosis and treatment. Methods: CLDN9 expression in GC tissues and cell lines was investigated in TCGA data, with analysis with Western blotting, qRT-PCR, and immunohistochemical analyses. Correlations between clinicopathological characteristics, progression-free survival (PFS), and overall survival (OS) were assessed with Cox regression. The effect of CLDN9 knockdown/overexpression on tumorigenic functions (proliferation, migration, and invasion) was assessed using CCK-8, colony formation, and Transwell assays. Tumor-bearing assays were performed to verify the impact of CLDN9 knockdown on the in vivo proliferation of GC cells. Results: Analysis of TCGA data, qRT-PCR, Western blotting, and immunohistochemistry indicated significantly elevated levels of CLDN9 in GC tissues and cell lines (p < 0.01). Compared to the group with high CLDN9 expression, PFS and OS were markedly longer in cases with low CLDN9 levels (p < 0.05). Multivariate regression indicated that CLDN9 levels were independently predictive of GC prognosis. CCK-8, Transwell, and colony formation tests showed that CLDN9 overexpression promoted GC cell proliferation, clonogenicity, and migratory/invasive capabilities, but CLDN9 knockdown markedly reduced these features. Experiments involving tumor-bearing models demonstrated that the suppression of CLDN9 inhibited the in vivo growth of GC cells. Conclusion: In conclusion, this study’s findings suggested that CLDN9 might be a valuable therapeutic target or diagnostic biomarker for GC. KW - Gastric cancer; CLDN9; cell proliferation; invasion; migration DO - 10.32604/biocell.2025.063296