KEGG analysis suggested that metabolism of xenobiotics by cytochrome P450 (CYP1B1, CYP1A1 and ALDH3A1), an important signalling pathway that influences the xenobiotic metabolizing capability of the lung and the risk of developing of lung diseases,22 was associated with COPD. The gene discussed is ALDH3A1; the disease is chronic obstructive pulmonary disease.