PDCD1 and cancer: KEGG signaling pathway enrichment analyses showed that the MAPK signal pathway was the top hit associated with MAPKAPK2. In addition, human immunodeficiency virus 1 infection, regulation of action cytoskeleton, focal adhesion, apoptosis, PD-L1 expression, PD-1 checkpoint pathway in cancer, etc., were enriched (Figures 5D, E).