A striking finding was that the interactions between smoking and polymorphism of CYP1A1 or GSTM1 gene increased significantly greater risk of NSCLC with hypermethylation of p16, DAPK or RARβ promoter, suggesting complex pathogenesis of NSCLC should be given top priority in future research. The gene discussed is RARB; the disease is non-small cell lung carcinoma.