Gene expression and clinical data of lung adenocarcinoma (LUAD) samples were extracted from The Cancer Genome Atlas (TCGA) and three Gene Expression Omnibus (GEO) datasets. 
The Cancer Genome Atlas (TCGA)
Gene expression and clinical data of lung adenocarcinoma (LUAD) samples were extracted from The Cancer Genome Atlas (TCGA) and three Gene Expression Omnibus (GEO) datasets. 
Gene Expression Omnibus (GEO)
A Cox regression model, integrating ERSS and the TNM stage, was developed to predict overall survival (OS) in TCGA cohort and was validated in GEO cohorts. 
Cox regression
Next, we identified 18 hub genes and constructed ERSS by LASSO regression. 
LASSO regression
Gene set enrichment analysis (GSEA), single-sample GSEA (ssGSEA), and gene mutation analyses were performed to further understand the molecular features of ERSS. 
Gene set enrichment analysis (GSEA)
Gene set enrichment analysis (GSEA), single-sample GSEA (ssGSEA), and gene mutation analyses were performed to further understand the molecular features of ERSS. 
single-sample GSEA (ssGSEA)
The tumor immune infiltration was evaluated by ESTIMATE, CIBERSORT, and xCell algorithms. 
ESTIMATE
The tumor immune infiltration was evaluated by ESTIMATE, CIBERSORT, and xCell algorithms. 
CIBERSORT
The tumor immune infiltration was evaluated by ESTIMATE, CIBERSORT, and xCell algorithms. 
xCell algorithms