LTBP4 and chronic obstructive pulmonary disease: However, as expected because of the minority representation of BC in the complete airway epithelium, of the 4 smoking BC dysregulated genes localized to 19q13.2 that have been identified as a COPD or smoking-related genes (either GWAS or candidate; NFKBIB, LTBP4, EGLN2, TGFB1), none were significantly different between nonsmokers and smokers.