S100A12 and chronic obstructive pulmonary disease: The PPI network of proteins encoded by DEGs identified 14 Hub DEGs associated with COPD, including CX3CR1, PPBP, PTGS2, FPR1, FPR2, VCAM1, S100A12, ARG1, EGR1, CD163, FGG, ORM1, S100A8 and S100A9. All of these Hub genes were involved in the most important two BPs, two MFs or five CCs revealed by GO analysis, and were mainly implicated in multiple pathways identified by KEGG analysis in this study.