CYP1A1 and non-small cell lung carcinoma: To our knowledge, we have first reported the interactions between smoking and polymorphisms of CYP1A1 and GSTM1 gene were significantly modified by hypermethylation of p16, DAPK or RARβ promoter in NSCLC, indicating the combined effects of smoking, CYP1A1, GSTM1, p16, DAPK and RARβ gene on development of NSCLC.