Immunoblotting showed that DNMT1 expression in lung tissue from non-COPD smokers and COPD patients was higher than that in lung tissue from nonsmokers (0.44 ± 0.12 and 0.73 ± 0.06 vs. 0.29 ± 0.11, P < 0.01 by one-way ANOVA and LSD test, Fig. 3c, d). The gene discussed is DNMT1; the disease is chronic obstructive pulmonary disease.