Since DNMT3B is able to mediate de novo DNA methylation and has been shown to be over-expressed in numerous types of cancer[14,28-31], this methyltransferase has been postulated to be an important factor in cancer, and it has been shown that DNMT3B polymorphisms are in fact significantly associated with the risk of developing lung cancer[32,33]. The gene discussed is DNMT3B; the disease is lung carcinoma.