PDCD1 and cancer: In addition, KEGG pathway terms including cell cycle, hepatitis B, PD-L1 expression and PD-1 checkpoint pathway in cancer, T cell receptor signaling pathway, VEGF signaling pathway, HIF-1 signaling pathway, EGFR tyrosine kinase inhibitor resistance and hepatocellular carcinoma were significantly enriched by KEGG analysis (Additional file 6: Fig. S3B, D).