PDCD1 and cancer: KEGG analysis results showed that the DEGs were mainly enriched in several pathways, including “Th1 and Th2 cell differentiation”, “Cytokine-cytokine receptor interactions,” “Antigen processing and presentation,” “Osteoclast differentiation,” “PD-L1 expression and PD-1 checkpoint pathway in cancer”, and “NF-kappa B signaling pathway” (Figure 4).