Applying univariate Cox regression analysis, 7 genes (LRRC31, HPGD, FCGBP, SPINK5, CYP24A1, S100P and FGG) out of the 20 differentially expressed smoking-related genes were significantly correlated with overall survival (OS) of NSCLC patients with smoking history in GSE50081, GSE68465 and GSE72094 cohort (Fig. 3A). This evidence concerns the gene CYP24A1 and non-small cell lung carcinoma.