Systemic immune microenvironment and regulatory network analysis in patients with lung adenocarcinoma

This study applied a complex bioinformatics analysis to explore the hub regulators and immune network to further elucidate the molecular mechanisms of lung adenocarcinoma (LUAD) immune regulation.

LUAD immunological microenvironment features and microenvironment-related differential expression genes (DEGs) were identified by ESTIMATE algorithm and linear models for microarray analyses (LIMMA), respectively. CIBERSORT and Igraph algorithms were applied to construct the LUAD-related immunocyte infiltration and regulatory network. Kaplan-Meier survival analysis, and univariate and multivariate Cox analysis were used to predict independent risk factors and screen for the hub genes. In addition, hub genes-correlated gene set enrichment analysis (GSEA), tumor mutation burden (TMB), and clinic pathological relation analyses were also performed.

Stromal, immune, and microenvironment comprehensive features (ESTIMATE score) were associated with overall survival (OS) in LUAD patients (all, P<0.05). T-cell activation, chemokine activity, and immune effect or dysfunction gene ontology maps were associated with the LUAD immune microenvironment. The immune infiltration cell subtypes mast cells (masT-cells) resting [The Cancer Genome Atlas (TCGA): P=0.01; Gene Expression Omnibus (GEO): P=1.79e-05] and activated T-cells (CD4 memory) (TCGA: P<0.01; GEO: P=8.52e-05) were found to have an important role in the immune cell regulatory network. Finally, ITGAL [univariate hazard ratio (HR) =0.80, 95% confidence interval (CI): 0.69-0.93, P<0.01; multivariate HR =0.59, 95% CI: 0.40-0.86, P=0.01] and KLRB1 (univariate HR =0.78, 95% CI: 0.69-0.89, P<0.01; multivariate HR =0.72, 95% CI: 0.58-0.90, P<0.01) were correlated with the T-cell receptor signaling pathway and anaplastic lymphoma kinase (ALK) fusion (ITGAL: P=0.034; KLRB1: P=0.050), and were considered as candidate biomarkers. A significant relation between KLRB1 expression level and TMB (P=3.6e-05) was identified, while no relation was detected for ITGAL (P=0.11).

The T-cell activation and activated T-cell (CD4 memory) pathways were predominantly involved in LUAD immune microenvironment regulation. The expression levels of ITGAL and KLRB1 were significantly correlated with the T-cell receptor signaling pathway and LUAD TMB, and were independent risk factors for OS.