In smokers without COPD, cigarette smoke (packs/year; r = −0.382, p = 0.028) was negatively correlated with CK14 expression, while FEV1/FVC (r = 0.405, p = 0.019) was positively correlated with the expression of this marker (Supplementary Figure S2). This evidence concerns the gene KRT14 and chronic obstructive pulmonary disease.