DNMT1 expression is increased in early stage lung cancer and is implicated in its pathogenesis through the silencing of such genes as RASSF1A and CDKN2A. CDKN2A was not only the first tumor suppressor gene to be found inactivated in lung cancer, but it shows promoter methylation in almost all cancers [24,65,88]. The gene discussed is CDKN2A; the disease is lung cancer.