To explore the underlying signaling pathways existing among the identified DEPs, KEGG pathway analyses were done to draw pathway maps.35 As shown in Figure 5A, the 78 identified DEPs were involved in 26 pathways, among which the top 5 involving more than three proteins were related to viral infectious diseases, signal transduction, immune system, digestive system and cancers. All the DEPs could be further classified into 6 KEGG pathway categories, including organismal systems, metabolism, human diseases, genetic information processing, environmental information processing, and cellular processes (Supplementary File S5). For the upregulated proteins, the top 20 relevant pathways were illustrated in Figure 5B and Supplementary File S6. The signaling pathways of interest included the RIG-I-like receptor signaling pathway, PI3K-AKT signaling pathway, endocytosis, pathways in cancer, etc. For the downregulated proteins, the top 20 relevant pathways were displayed in Figure 5C and Supplementary File S7. The signaling pathways of interest included the mTOR, MAPK, FoxO signaling pathways and so on. Interestingly, one upregulated protein (Secretagogin) and one downregulated protein (AKT2) were simultaneously involved in Fc gamma R-mediated phagocytosis. To further explore the possible involvement of the identified DEPs in the underlying signaling pathways, KEGG pathway enrichment analysis was performed. Our data demonstrated that the DEPs were primarily involved in the HIF-1 signaling pathway, HTLV-I infection, human papillomavirus infection, AGE-RAGE signaling pathway in diabetic complications, central carbon metabolism in cancer, influenza A, measles, Fc gamma R-mediated phagocytosis, small cell lung cancer, glycosaminoglycan biosynthesis, progesterone-mediated oocyte maturation, and relaxin signaling pathway (Figure 5D). These signaling pathways were mainly distributed in four distinct functional categories: environmental information processing, human diseases, metabolism, and organismal systems (Figure 5D).