Bronchial tissue was collected from patients undergoing lung resection. All specimens were procured at least 5 cm from bronchial sites affected by disease diagnoses, and analyses indicated that tissue was histologically normal. The UMCG cohort (table S2) included specimens analyzed in collaboration with the UMCG collected from four never smokers and four current smokers. Specimens were obtained from the tissue bank in the UMCG Department of Pathology. The study protocol was consistent with the Research Code of the UMCG and Dutch national ethical and professional guidelines (“Code of conduct; Dutch federation of biomedical scientific societies”; The UCL cohort (table S3) included specimens analyzed in collaboration with the UCL collected from five never smokers and five current smokers. Ethical approval was sought and obtained from the UCL Hospital Research Ethics Committee (REC reference 06/Q0505/12). This study was carried out in accordance with the Declaration of Helsinki (2000) of the World Medical Association.