Lin et al identified that the tobacco-specific carcinogen nicotine-derived nitrosamine ketone (NNK) induces the accumulation of DNA methyltransferase 1 (DNMT1) and the promoter hypermethylation of tumor suppressor genes, such as FHIT, p16INK4a, and RARB, in lung cancer patients [9]. This evidence concerns the gene DNMT1 and lung carcinoma.