Background: Reticulosome family gene 1 (RTN1) is a reticulosome-encoding gene associated with the endoplasmic reticulum. RTN1 plays a key role in membrane trafficking or neuroendocrine secretion of neuroendocrine cells, while RTN1 serves as a potential diagnostic/therapeutic marker for neurological diseases and cancer. However, the expression of RTN1 and its effect on the immune microenvironment in patients with lung adenocarcinoma have not been reported. In this study, we aimed to investigate the expression of RTN1 in lung adenocarcinoma and its correlation with immune infiltration and survival in lung adenocarcinoma using public databases and bioinformatics network tools.
Methods: Expression levels of RTN1 mRNA in tumor and normal tissues were analyzed using Tumor Immune Estimation Resource 2.0 (TIMER 2.0) and Gene Expression Profiling Interactive Analysis 2 (GEPIA 2). RTN1 protein expression was examined using the Human Protein Atlas. The clinical prognostic significance of RTN1 was analyzed using the GEPIA2 plotter database. To further confirm the potential function of RTN1, the data were analyzed using gene set enrichment analysis. In addition, We performed dimensionality-reduced clustering analysis at the single-cell sequencing level on two datasets from the Tumor Immune Single-cell Hub (TISCH) database to observe the cellular clustering of RTN1 in different types of immune cells. Using the TIMER online tool to analyze and predict the infiltration abundance of different types of immune cells in the immune microenvironment of lung adenocarcinoma patients in the TCGA cohort; TIMER and CIBERSORT were used to study the relationship between genes co-expressed with RTN1 and its associated tumor-infiltrating immune cells; finally, TIMER was used to analyze the relationship between RTN1 and immune correlations between immune checkpoints.
Results: We found that RTN1 expression was decreased in patients with lung adenocarcinoma and was closely related to patient prognosis. RTN1 is involved in the process of phagosome formation, hematopoietic cell formation and cell adhesion, and plays an important role in T cell activation. Using cBioPortal and TCGA data to analyze, it is found that RTN1 is significantly associated with BTK, CD4, ECSF1R, MNDA, NCKAP1L and SNX20. High expression of the above genes may cause significant upregulation of CD4+ T cells, mast cells, monocytes, myeloid dendritic cells and M1 macrophages. The expression of RTN1 is closely related to the common immune checkpoints CD274, CTLA4, HAVCR2, LAG3, PDCD1, PDCD1LG2, TIGIT and SIGLEC15 immune checkpoints.
Conclusions: RTN1 may act as a tumor suppressor gene and indicate better prognosis. Furthermore, RTN1 is associated with immune infiltration that may be involved in the immunotherapy response in LUAD. However, the related mechanism needs further research.
【中文题目：RTN1在肺腺癌中表达及 对免疫微环境的影响】 【中文摘要：背景与目的 网状体家族基因 1（Reticulon family gene 1, RTN1）是一种与内质网相关的网状体编码基因。RTN1在神经内分泌细胞的膜运输或神经内分泌分泌中起关键作用，同时RTN1可作为有神经内分泌成分的恶性肿瘤的潜在诊断/治疗标志物。然而在肺腺癌（lung adenocarcinoma, LUAD）患者中RTN1的表达情况及其对免疫微环境影响均未有报道。本研究旨在使用公共数据库和生物信息学网络工具研究RTN1在肺腺癌中的表达及其与肺腺癌中免疫浸润和存活的相关性。方法 使用Tumor Immune Estimation Resource 2.0（TIMER 2.0）和Gene Expression Profiling Interactive Analysis 2（GEPIA 2）分析肿瘤和正常组织中RTN1 mRNA的表达水平。使用人类蛋白质图谱检查RTN1蛋白质表达。利用GEPIA2在线工具分析癌症基因组图谱（The Cancer Genome Atlas, TCGA）中RTN1的临床预后意义。为了进一步确认RTN1的潜在功能，使用基因集富集分析对数据进行了分析。此外，我们对来自肿瘤免疫单细胞中心（Tumor Immune Single-cell Hub, TISCH）数据库的两个数据集在单细胞测序水平上进行降维聚类分析，观察RTN1在不同种类免疫细胞的细胞聚类。使用TIMER在线工具分析预测TCGA队列肺腺癌患者免疫微环境中不同种类免疫细胞浸润丰度；使用TIMER和CIBERSORT研究与RTN1共表达基因和其相关肿瘤浸润免疫细胞之间的关系；最后，使用TIMER分析RTN1与免疫检查点之间的相关性。结果 我们发现LUAD患者的RTN1表达降低，且与患者的预后密切相关。RTN1参与吞噬体的形成、造血细胞形成和细胞黏附的过程，对T细胞活化起着重要作用，使用cBioPortal与TCGA数据来分析，发现RTN1与BTK、CD4、ECSF1R、MNDA、NCKAP1L和SNX20显著相关。以上基因高表达可能会引起CD4+ T细胞、肥大细胞、单核细胞、髓样树突状细胞和M1型巨噬细胞显著上调。并且，RTN1表达与常见免疫检查点CD274、CTLA4、HAVCR2、LAG3、PDCD1、PDCD1LG2、TIGIT、SIGLEC15密切相关。结论 RTN1作为一种肿瘤抑制基因并可能与更好的预后相关。此外，RTN1与可能参与免疫治疗反应的免疫浸润有关。但与其相关的机制需要进一步的研究。 】 【中文关键词：肺腺癌；免疫治疗；RTN1；预后；免疫微环境】.
Keywords: Immune microenvironment; Immunotherapy; Lung adenocarcinoma; Prognosis; RTN1.