HIF1A and chronic obstructive pulmonary disease: As for COPD, KEGG pathway analyses of DEGs were significantly enriched for gap junction (P = 0.003734), metabolism of xenobiotics by cytochrome P450 (P = 0.002103), Hypoxia-inducible factor 1-alpha (HIF-1) signaling pathway (P = 0.008497), and Forkhead box O (FoxO) signaling pathway (P =0.02568) (Figure 1D).