PDCD1 and cancer: Results from GSEA-GOBP and GSEA-KEGG suggested that the functional enrichment of group A tended toward pathways for immunity and immunotherapy such as B cell mediated immunity, lymphocyte mediated immunity, immunoglobulin mediated immune response, PD-L1 expression, PD-1 checkpoint pathway in cancer, Th1 and Th2 cell differentiation, and Th17 cell differentiation (Additional file 1: Fig. S4A, B).