The PD-1/PD-L1 group covered a broader range of malignancies, including metastatic melanoma, non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), renal cell carcinoma, bladder cancer, hepatocellular carcinoma (HCC), oesophageal cancer, colorectal cancer, gastric cancer, nasopharyngeal carcinoma, intrahepatic cholangiocarcinoma, breast cancer, cervical cancer, ovarian cancer, cutaneous T-cell lymphoma, and head and neck squamous cell carcinoma (HNSCC)(Table 2). Here, PDCD1 is linked to head and neck squamous cell carcinoma.