AREG and chronic obstructive pulmonary disease: We finally identified 11 genes (ADM, AREG, CXCR4, EFNA1, EGLN3, FBXO32, HILPDA, IGFBP3, SLC7A11, TXNIP, and WNT5A) as potential descriptive marker genes for smokers and 4 genes (AREG, DUSP6, EFNA1, and TXNIP) as potential descriptive marker genes for COPD subjects.