基于TCGA数据库分析CLDN9在胃癌中的预后价值及与免疫浸润的相关性

Prognostic value of CLDN9 in gastric cancer based on TCGA database and its correlation with immune infiltration

摘要

目的：分析连接蛋白CLDN9与胃癌预后的关系并进一步探索其与免疫浸润的相关性。方法：利用癌症基因组图谱（TCGA）数据库获取胃癌的CLDN9基因表达量及相应的临床特征。通过Mann-Whitney U及Wilcoxon符号秩和检验分析胃癌组织与正常组织间CLDN9基因差异表达及其与临床特征的关系，进一步单因素、多因素Cox及Kaplan-Meier方法探索CLDN9与预后的相关性，利用ROC曲线获取最佳截断值。通过STRING构建蛋白质-蛋白质相互作用网络并进一步行基因本体（GO）及京都基因百科全书和基因组（KEGG）的功能注释。通过肿瘤免疫估计资源分析CLDN9与免疫细胞浸润丰度的关系。结果：CLDN9基因在胃癌组织中表达上调，且男性CLDN9高表达，而G ₃期胃癌组织中的CLDN9低表达（均P<0.05）。CLDN9基因高表达组总生存期（OS）明显小于低表达组（20.6个月比58.2个月，HR=1.694，95% CI：1.214～2.365，P=0.002），在各亚组中（年龄＞65岁、T _1~2、N _1~3、M ₀、Ⅲ~Ⅳ期、G ₃、R ₀残留肿瘤、无Barretts食管、无反流史、未抗反流治疗及无Hp感染）CLDN9高表达组OS都小于低表达组（均P<0.05）。CLDN9区分胃癌组织与正常组织的最佳截断值为0.426，其敏感度和特异度分别为78.1%和73.6%。通过GO及KEGG进行功能注释发现，CLDN9可能参与细胞紧密连接及细胞-细胞黏附信号通路。CLDN9表达与CD8 ⁺ T细胞（r=-0.276）、中性粒细胞（r=-0.192）及树突状细胞（r=-0.213）的浸润丰度具有负相关性（P<0.001）。结论：CLDN9基因在胃癌中高表达，且高表达的CLDN9与免疫抑制及不良预后相关，可作为潜在预后预测指标及治疗靶点。

Abstract

Objective: To analyze the relationship between connexin CLDN9 and the prognosis of gastric cancer and explore its correlation with immune infiltration based on TCGA database. Methods: The CLDN9 gene expression and corresponding clinical characteristics of gastric cancer were obtained from TCGA. The Mann-Whitney U and Wilcoxon signed-rank sum tests were used to analyze the differential expression of CLDN9 gene between gastric cancer tissue and normal tissue and its relationship with clinical characteristics, Univariate and multivariate COX and Kaplan-Meier methods were used to explore the correlation between CLDN9 and patient prognosis. Receiver operating characteristic (ROC) curve was used to obtain the optimal cutoff value. The protein-protein interaction network was constructed by STRING and further functional annotation was performed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). The relationship between CLDN9 and immune cell infiltration abundance was analyzed by the Tumor Immunity Estimation Resource （TIMER）. Results: CLDN9 gene was up-regulated in gastric cancer tissues, and CLDN9 was highly expressed in male gastric cancer tissues, while CLDN9 was found to be low expressed in G3 gastric cancer tissues (all P<0.05). The OS of patients in the high expression group of CLDN9 gene was significantly shorter than that in the low expression group (20.6 months vs. 58.2 months, HR=1.694, 95% CI: 1.214-2.365, P=0.002). Subgroup data analysis such as age > 65 years old, T _1-2, N _1-3, M ₀, Ⅲ- Ⅳ stage, G ₃, R ₀ residual tumors, no Barretts esophagus, no history of reflux, no anti-reflux treatment and no Hp infection also revealed that the OS of the high CLDN9 expression group was shorter. The optimal cut-off value of CLDN9 to distinguish gastric cancer tissue from normal tissue was 0.426, and its sensitivity and specificity were 78.1% and 73.6%, respectively. Through functional annotations in GO and KEGG, it was found that CLDN9 may be involved in cell tight junctions and cell-cell adhesion signaling pathways. CLDN9 expression was negatively correlated with the infiltrating abundance of CD8 ⁺ T cells (r=-0.276), neutrophils (r=-0.192) and dendritic cells (r=-0.213, P<0.001). Conclusion: CLDN9 gene is highly expressed in gastric cancer, and the high expression of CLDN9 is associated with immunosuppression and poor prognosis, and can be used as a potential prognostic predictor and therapeutic target.

关键词

连接蛋白CLDN9 / 胃肿瘤 / 预后 / 免疫浸润

Key words

CLDN9 / Stomach neoplasms / Prognosis / Immune infiltration

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基金资助

孝感市自然科学计划项目(XGKJ2024010020)