Smokers, as well as the patients with COPD displayed higher KL-6 positive bronchiolar/alveolar epithelium (sum of the bronchiolar/alveolar epithelium; Epi) than non-smoker's lung (p = 0.006 and p < 0.001, respectively), and the epithelial positivity was more prominent in the COPD than in the smoker's lung (Figure 3D). This evidence concerns the gene MUC1 and chronic obstructive pulmonary disease.