For example, upregulation of miR-15b and downregulation of its target SMAD7, which is an inhibitory SMAD in TGF-β signaling, is reported in lung tissues of COPD patients compared with smokers without obstruction, and thereby regulates TGF-β signaling pathway and pathogenesis of COPD (Ezzie et al., 2012). This evidence concerns the gene SMAD7 and chronic obstructive pulmonary disease.