The expression of PD-1 was upregulated in liver hepatocellular carcinoma (LIHC), pheochromocytoma and paraganglioma (PCPG), prostate adenocarcinoma (PRAD), breast invasive carcinoma (BRCA), kidney renal papillary cell carcinoma (KIRP), cholangiocarcinoma (CHOL), head and neck squamous cell carcinoma (HNSC), uterine corpus endometrial carcinoma (UCEC), kidney renal clear cell carcinoma (KIRC), lung squamous cell carcinoma (LUSC), and lung adenocarcinoma (LUAD), while it was downregulated in kidney chromophobe (KICH) and thyroid carcinoma (THCA) (P < 0.05). This evidence concerns the gene PDCD1 and head and neck squamous cell carcinoma.