(A) Decreased MYB expression in early, short-term, mid-term, and long-term ALI culture in smokers and COPD AE, as compared with non-smokers. (B) In short- and long-term cultures, MYB mRNA levels down-regulation correlated moderately but significantly with the COPD severity, witnessed by the FEV1. Correlation graph includes only Smo and COPD samples to specifically assess the correlation with the disease severity. $, £, and § highlight significant decreases in Smo, COPD1-2, and COPD3-4 patients, respectively, as compared with NS. ** indicates P-values of less than 0.01. Bars indicate median ± interquartile range. AE, airway epithelium; ALI, air-liquid interface; COPD, chronic obstructive pulmonary disease; CT, control; FEV1, forced expired volume in 1 s; HKG, housekeeping genes; NS, non-smokers; Smo, smokers; y, years.