On one hand, previous study has demonstrated that the expression of DNA methyltransferase 1 (DNMT1) in smokers was significantly higher than that of non-smokers in bladder cancer (26), and the levels of methylated metabolites, polycyclic aromatic hydrocarbons, DNA adducts, and DNA damage were elevated in smokers with bladder cancer. This evidence concerns the gene DNMT1 and urinary bladder carcinoma.