In murine models of cigarette smoke-induced lung cancer, hypermethylation of the TSGs, death-associated protein kinase 1 (DAPK1) and the retinoic acid receptor beta (RARB), is seen at the earliest histological stage of adenocarcinoma development (Pulling et al, 2004; Vuillemenot et al, 2004). This evidence concerns the gene RARB and lung cancer.