基于TCGA数据库的 EGFR突变型与野生型肺腺癌患者免疫微环境的差异性分析 Translated title: Immune Microenvironment Comparation Study between EGFR Mutant and EGFR Wild Type Lung Adenocarcinoma Patients Based on TCGA Database

Abstract

背景与目的

肺癌是一种具有高发病率与高死亡率的恶性肿瘤，腺癌是其中一个重要的组织亚型。表皮生长因子受体（epidermal growth factor receptor, EGFR）突变是肺腺癌患者重要的驱动基因。EGFR-酪氨酸激酶抑制剂（tyrosine kinase inhibitor, TKI）对 EGFR敏感突变的患者疗效显著。而免疫治疗作为新兴的治疗却不能使 EGFR突变患者获益，其中的机制研究尚不明确，并集中于EGFR与程序性死亡受体-配体1（programmed cell death-ligand 1, PD-L1）表达之上，而我们推测与两类患者不同的免疫微环境有关。

方法

从癌症基因组图谱（The Cancer Genome Atlas, TCGA）数据库收集肺腺癌数据集，下载临床信息资料及基因表达谱资料。通过TIMER2.0计算TCGA数据库中免疫相关淋巴细胞浸润情况。并对 EGFR突变型与野生型患者进行基因集富集分析。

结果

临床特征分析显示 EGFR突变更频繁发生于女性以及未吸烟患者中。免疫浸润分析显示 EGFR突变患者通常具有更高的肿瘤相关成纤维细胞、普通髓系祖细胞、造血干细胞、效应CD4 ⁺ T细胞、自然杀伤T细胞浸润；具有更低的记忆B细胞、初始B细胞、浆细胞、浆细胞样树突状细胞、记忆CD4 ⁺ T细胞、CD4 ⁺辅助性T细胞2、CD8 ⁺ T细胞、中心记忆CD8 ⁺ T细胞、初始CD8 ⁺ T细胞浸润。我们发现CD8 ⁺ T细胞、自然杀伤T细胞、记忆B细胞和造血干细胞在肿瘤中浸润的程度越高则患者预后越好（ Log-rank检验， P=0.017、0.009, 3、0.018和0.016）。同时CD4 ⁺辅助性T细胞2在肿瘤中浸润的程度越高则患者预后越差（ Log-rank检验， P=0.016）。基因集富集分析的结果显示，相比较EGFR野生型肺腺癌患者而言， EGFR突变患者的自然杀伤细胞介导的对肿瘤细胞的免疫应答的正调控、自然杀伤细胞激活参与免疫反应、在自然杀伤细胞介导的对肿瘤细胞的免疫应答这三条与自然杀伤细胞有关的通路上均处于下调状态，而参与免疫应答的细胞因子分泌的正调节这条通路为上调。

结论

EGFR突变患者肿瘤微环境缺乏有效的杀伤肿瘤的效应细胞并出现了效应细胞功能失调。这可能是 EGFR突变患者免疫治疗疗效差的潜在原因。

Translated abstract

Background and objective

Lung cancer is a malignant with high incidence and mortality and adenocarcinoma is among the most popular subtypes. Epidermal growth factor receptor ( EGFR) mutation is one of the most important driver mutations for lung adenocarcinoma and EGFR-tyrosine kinase inhibitor (TKI) will benefit those patients with sensitive EGFR mutations. Recently, immune checkpoint inhibitor (ICI) therapy, provide a new breakthrough treatment for lung cancer patients. Whereas immunotherapy as an emerging treatment does not benefit patients with EGFR mutations, for which mechanistic studies are poorly defined and focused on the link of EGFR mutations and programmed cell death-ligand 1 (PD-L1) expression, we speculate that the different immune microenvironment associated with the two classes of patients.

Methods

Lung adenocarcinoma datasets were collected from the Cancer Genome Atlas (TCGA) database, and clinical information and gene expression profiles were downloaded. The immune related lymphocyte infiltration in TCGA database were generated through timer 2.0 GSEA was used to analyze the difference of pathway expression between EGFR mutant patients and wild type patients.

Results

EGFR mutation was more frequently among women and never smokers. Immunoinfiltration analysis showed that patients with EGFR mutation tends to have more tumor associated fibroblasts, common myeloid progenitor cells, hematopoietic stem cells, effector CD4 ⁺ T cells and natural killer T cells infiltration, and less memory B cells, naïve B cells, plasma B cells, plasmacytoid dendritic cells, memory CD4 ⁺ T cells, CD4 ⁺ helper T cells 2, naive CD8 ⁺ T cells, CD8 ⁺ T cells and central memory CD8 ⁺ T cells infiltration. Moreover, patients with more infiltration of CD8 ⁺ T cells, natural killer T cells, memory B cells and hematopoietic stem cells, tends have better prognosis ( Log-rank test, P=0.017, 0.0093, 0.018, 0.016). However, the patients with more CD4 ⁺ T th2 infiltration in the tumor tends to have worse prognosis ( Log-rank test, P=0.016). Furthermore, the results of gene set enrichment analysis showed that compared with the lung adenocarcinoma patients with EGFR wild type, the three pathways positive regulation of natural killer (NK) cell-mediated immune response to tumor cells, NK cell activation involved in immune response, and NK cell-mediated immune response to tumor cells related to natural killer cells in patients with EGFR mutation were down regulated, while the pathway the positive regulation of cytokine secretion involved in immune response was up-regulated in EGFR mutation patients.

Conclusion

The tumour microenvironment of patients with EGFR mutations lacks potent tumour killing effector cells and appears dysfunctional with effector cells. This may be a potential reason for the poor efficacy of immunotherapy in patients with EGFR mutations.