KRT5 and chronic obstructive pulmonary disease: As we analyzed the correlation between CK5 expression and age, cigarette smoke (pack/years) and lung function parameters in smokers with and without COPD separately, we found that the expression of this marker was negatively correlated with age (r = −0.334, p = 0.047), and positively associated with FVC (r = 0.335, p = 0.046) in only BEC cultures of COPD patients (Supplementary Figure S2).