PDCD1 and cancer: GSEA revealed that KLRB1 was implicated in mechanisms such as T cell receptor, B cell receptor, NK cell-mediated cytotoxicity, Toll-like receptor, chemokine, NF-kappa B, PD-L1 expression and PD-1 checkpoint pathway in cancer, cell adhesion molecules, JAK-STAT, TNF, necroptosis, cell cycle, and other pathways (Table S1).