Abstract
BACKGROUND: 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. CONCLUSIONS: 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.