CYP1A1 and chronic obstructive pulmonary disease: KEGG analysis for 26 COPD key genes indicated that metabolism of xenobiotics by cytochrome P450 (CYP1B1/CYP1A1/ALDH3A1/ADH7), Chemical carcinogenesis—DNA adductsand (CYP1B1/CYP1A1/EGF) and chemical carcinogenesis—receptor activation (CYP1B1/CYP1A1/EGF) were related to COPD.