CH25H and chronic obstructive pulmonary disease: To address the mechanism underlying the regional upregulation of CH25H predominantly localized to the airways in COPD patients and in particular that associated with emphysematous tissue, we first undertook gene set enrichment analysis (GSEA; Mootha et al, 2003; Subramanian et al, 2005) on the publically available transcriptomics dataset of small airway epithelial cells from COPD patients described above (Tilley et al, 2011).