PDCD1 and cancer: The results of KEGG analysis showed that intersection genes were enriched in Primary immunodeficiency, Hematopoietic cell lineage, PD-L1 expression and PD-1 checkpoint pathway in cancer, T cell receptor signaling pathway, PD-L1 expression and PD-1 checkpoint pathway in cancer, T cell receptor signaling pathway, and Cytokine-cytokine receptor interaction pathways (Figures 4B, C).