KEGG pathway analysis further indicated significant enrichment of COPD-related genes in pathways including arachidonic acid metabolism, IL-17 signaling, TNF signaling, cell adhesion molecules, retinol metabolism, cytochrome P450 metabolism, and mucin-type O-glycan biosynthesis (Figure 2E; Supplementary Table 3). This evidence concerns the gene TNF and chronic obstructive pulmonary disease.