Objectives: The efficacy of immunotherapy for lung cancer is closely related to immune cell infiltration. Arachidonic acid 5-lipoxygenase (ALOX5) can activate inflammatory responses and trigger various cell death patterns; however, the relevance of ALOX5 to immune cell infiltration in lung cancer is unclear. The expression of ALOX5 in non-small cell lung cancer (NSCLC) is analyzed using an online database to explore the correlation between ALOX5 and immune cell infiltration in NSCLC and its relationship with prognosis.
Methods: Differences in ALOX5 expression in NSCLC and normal lung tissues were analyzed by online databases such as TIMER, GEPIA and HPA; the UALCAN database was used to reveal the relationship between ALOX5 and clinical features; Kaplan-Meier database was applied to explore the prognostic value of ALOX5; GeneMANIA and String Website was used to explore genes and proteins associated with ALOX5 expression, respectively; the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used to analyze ALOX5 differential genes which were picked up through the TCGA database; GSEA software was applied to predict the signal pathways that ALOX5 may be involved in; and the TIMER database was used to analyze the effect of ALOX5 expression on the level of immune cell infiltration.
Results: Compared with the normal lung tissues, the ALOX5 expression was low in NSCLC tissues (P<0.05), and which affected the prognosis of lung cancer patients. The expression level of ALOX5 was related to clinical features such as sex, age, metastasis, and pathological staging in NSCLC patients (all P<0.05). The gene interaction network analysis found that the genes interacting with ALOX5 mainly included the genes related to lipid oxidation and pro-inflammatory mediators such as coactosin like protein 1 (COTL1), leukotriene C4 synthase (LTC4S), and prostaglandin endoperoxide synthase 2 (PTGS2), and the protein-protein interaction analysis results were consistent. GO and KEGG analysis found that ALOX5 was involved in the biological process of activation of immune cell function and was involved in immune response function pathways. The GSEA analysis showed that ALOX5 may activate immune responses and mediate immune-related prognosis by affecting the cytokine-cytokine receptor interactions, natural killer-mediated cytotoxicity, and T cell receptor signaling pathways. The ALOX5 mRNA expressions in lung adenocarcinoma and lung squamous cell carcinoma were positively correlated with the tumor infiltration immune cells (B cells, CD8+ T cells, CD4+ T cells, etc.) (all P<0.05), and the ALOX5 mRNA expression was positively correlated with the expression of classic T cell immune checkpoint inhibitor genes (P<0.001).
Conclusions: The ALOX5 gene expression in NSCLC is significantly downregulated, and which can affect NSCLC prognosis and immune cell infiltration levels. ALOX5 gene may be a potential biomarker of NSCLC prognosis associated with immune cell infiltration.
目的: 肺癌免疫治疗疗效与免疫细胞浸润密切相关。花生四烯酸5-脂氧合酶5(arachidonic acid 5-lipoxygenase，ALOX5)可激活炎症反应并触发各种细胞死亡模式；然而，ALOX5与肺癌免疫细胞浸润的相关性尚不清楚。本研究利用在线数据库分析ALOX5在非小细胞肺癌(non-small cell lung cancer，NSCLC)中的表达，探讨其与NSCLC免疫细胞浸润的相关性及其与预后的关系。方法: 分析TIMER、GEPIA和UALCAN等在线数据库中NSCLC和正常组织ALOX5 mRNA和蛋白表达的差异；应用Kaplan-Meier数据库探讨ALOX5的预后价值，GeneMANIA和String网站探索与ALOX5基因表达相关联的基因及蛋白质；对TCGA数据库挖掘出的差异基因进行基因本体(Gene Ontology，GO)和京都基因与基因组百科全书(Kyoto Encyclopedia of Genes and Genomes，KEGG)富集分析；应用基因集富集分析(gene set enrichment analysis，GSEA)软件预测ALOX5可能参与的信号通路，TIMER数据库分析ALOX5对免疫细胞浸润水平的影响。结果: 与正常肺组织相比，ALOX5在NSCLC组织中呈低表达(P<0.05)，且影响NSCLC患者预后。基因互作网络分析发现：与ALOX5基因相互作用的基因主要有毛状样蛋白(coactosin like protein 1，COTL1)、白三烯C4合酶(leukotriene C4 synthase，LTC4S)和环加氧酶2(prostaglandin endoperoxide synthase 2，PTGS2)等脂质氧化和促炎介质生成的相关基因，蛋白质-蛋白质相互作用(protein-protein interaction，PPI)网络分析结果与之一致。GO、KEGG富集分析发现：ALOX5基因参与多种免疫细胞功能活化的生物过程，并参与免疫反应功能通路。GSEA结果显示ALOX5可能通过影响细胞因子与细胞因子受体的相互作用、自然杀伤细胞介导的细胞毒性和T细胞受体等信号通路，从而激活免疫反应，介导与免疫相关的预后。肺腺癌及肺鳞状细胞癌中ALOX5 mRNA表达与肿瘤浸润性免疫细胞(B细胞、CD8+T细胞、CD4+T细胞等)浸润水平均呈正相关(均P<0.05)，并且与经典的T细胞免疫检查点抑制剂基因标志物呈正相关(P<0.001)。结论: ALOX5基因在NSCLC中表达显著下调，可影响NSCLC预后和肿瘤免疫细胞浸润水平。ALOX5基因可能是潜在的与免疫细胞浸润相关的NSCLC预后生物标志物。.
Keywords: arachidonic acid 5-lipoxygenase; immune cell infiltration level; non-small cell lung cancer; prognostic biomarkers.