富亮氨酸α2糖蛋白1在乳腺癌中的表达及其功能的生物信息学分析

Bioinformatics analysis of expression of leucine-rich α 2 glycoprotein 1 in breast cancer and its function

摘要:

背景与目的 富亮氨酸α2糖蛋白1（LRG1）是富亮氨酸重复序列（LRR）家族蛋白成员，近些年研究显示LRG1在恶性肿瘤的发生、上皮间质转化、侵袭转移、异常血管生成、预后预测中发挥重要作用。然而LRG1在乳腺癌中的表达、预后、功能和潜在机制方面尚待阐明。本研究旨在通过生物信息学方法系统分析LRG1在乳腺癌中的表达及意义。方法 使用TCGA、Breast Cancer Gene-Expression Miner、UALCAN、Kaplan-Meier Plotter、GeneMANIA、DAVID等多个数据库对LRG1在乳腺癌中的表达与临床病理特征关系、预后价值、相互蛋白作用网络及功能富集进行综合分析。结果 TCGA数据库分析显示，LRG1 mRNA在乳腺浸润癌中的表达量明显高于正常组织（23.461 vs. 8.357，P<0.001）。在不同分子亚型中，luminal型乳腺癌中LRG1 mRNA表达量为37.462（9.930~74.197），高于HER-2阳性型乳腺癌和三阴性乳腺癌（TNBC）（均P<0.01）；I、II、III期乳腺癌中LRG1 mRNA的表达水平均高于正常乳腺组织（均P<0.05）。Breast Cancer Gene-Expression Miner数据库分析显示，雌激素受体（ER）和（或）孕激素受体（PR）阳性乳腺癌中LRG1 mRNA的表达水平高于ER和（或）PR阴性乳腺癌，HER-2阴性乳腺癌中LRG1 mRNA表达高于HER-2阳性型乳腺癌（均P<0.05）；淋巴结阳性乳腺癌LRG1 mRNA表达量高于淋巴结阴性乳腺癌（P<0.000 1）。用GEPIA在线平台对TCGA数据库中乳腺癌数据进行生存分析发现，LRG1高表达患者总生存率（OS）及无复发生存率（RFS）均低于低表达患者，但差异无统计学意义（HR=0.81，P=0.200；HR=0.70，P=0.064）；用Kaplan-Meier plotter对TCGA中乳腺癌数据进行生存分析发现，LRG1的表达与luminal A型、luminal B型、HER-2阳性型乳腺癌的OS无明显关系（均P>0.05），但在basal-like亚型中，LRG1低表达患者OS明显优于LRG1高表达患者（HR=3.12，95% CI=1.54~6.29，P<0.001）。使用GeneMANIA数据库进行分析，共筛选出20个与LRG1相互作用蛋白质，GO富集分析显示，LRG1及与其共表达相关的20个蛋白富集于细胞胞外区，外泌体，血液微粒，受体复合物等结构中，参与细胞的血管生成调控、上皮间充质的转化、缺氧反应等相关生物学过程。结论 LRG1在乳腺癌组织中表达上调，并可预测部分不良乳腺癌亚型的预后，LRG1可能为乳腺癌治疗提供新的靶点。

Abstract:

Background and Aims Leucine-rich α 2 glycoprotein 1 (LRG1) is a member of the leucine-rich repeat (LRR) protein family. Recent studies have shown that LRG1 plays an important role in the occurrence, epithelial-mesenchymal transformation, invasion and metastasis, abnormal angiogenesis and prognosis of malignant tumors. However, the research on the expression, prognosis, function and potential mechanism of LRG1 in breast cancer remains to be elucidated. The purpose of this study was to systematically analyze the LRG1 expression in breast cancer and its significance based on bioinformatics approaches.Methods The expression of LRG1 in breast cancer and its relationship with clinicopathologic characteristics, prognostic value, interacting protein networks and functional enrichment were systematically analyzed by using the TCGA, Breast Cancer Gene-Expression Miner, UALCAN, Kaplan-Meier Plotter, GeneMANIA, DAVID and other databases.Results TCGA database analysis showed that the mRNA expression of LRG1 in breast invasive carcinoma was significantly higher than normal tissues (23.461 vs. 8.357, P<0.001). Among different molecular subtypes, LRG1 mRNA expression level in luminal subtype breast cancer was 37.462 (9.930-74.197), which was higher than that in HER-2 positive subtype and triple-negative subtype (both P<0.01); the LRG1 mRNA expression levels in stage I, II and III breast cancer were all higher than that in normal breast tissue (all P<0.05). Breast Cancer Gene-Expression Miner database analysis showed that the LRG1 mRNA expression levels in estrogen receptor (ER) and (or) progesterone receptor (PR) positive breast cancer were higher than those in ER and (or) PR negative breast cancer, and the LRG1 mRNA expression level in HER-2 negative breast cancer was higher than that in HER-2 positive breast cancer (all P<0.05); the LRG1 mRNA expression level in lymph node-positive breast cancer was higher than that in lymph node-negative breast cancer (P<0.000 1). Analysis of the TCGA survival data using the GEPIA online platform showed that both the overall survival (OS) and recurrence-free survival (RFS) rates in patients with high LRG1 expression were lower than those in patients with low LRG1 expression, but the differences did not reach a statistical significance (HR=0.81, P=0.200; HR=0.70, P=0.064); analysis of the TCGA survival data using Kaplan-Meier plotter revealed that LRG1 expression was not significantly correlated with the OS in luminal A, luminal B, and HER-2 positive subtypes (all P>0.05), but in the basal-like subtype breast cancer, the OS in patients with low LRG1 expression was better than that in patients with high LRG1 expression (HR=3.12, 95% CI=1.54-6.29, P<0.001). Using the GeneMANIA database for analysis, a total of 20 proteins interacting with LRG1 were screened. GO enrichment analysis showed that the LRG1 and the 20 its co-expression associated proteins were enriched in the extracellular regions, exosomes, blood particles, receptor complexes and other structures, and were involved in cell angiogenesis regulation, epithelial-mesenchymal transformation, hypoxia response and other relevant biological processes.Conclusion LRG1 expression is upregulated in breast invasive carcinoma and can predict the prognosis of some unfavorable subtypes of breast cancer. LRG1 may provide a new target for breast cancer treatment.