Because of the elevated DNMT1 protein level and hypermethylation of Bcl-2 in the lung tissue of emphysema subjects, we tested whether modulation of the DNMT1 protein level or activity ameliorates emphysema, pulmonary apoptosis and Bcl-2 promoter hypermethylation in mouse models. This evidence concerns the gene DNMT1 and pulmonary emphysema.