For instance, the m6A score or m6A-related high/low-risk subgroup, based on the expression of m6A methylation-related genes, was characterized by differential expression of several immune checkpoints, including PD-1, PD-L1, and CTLA-4 in head and neck squamous cell carcinoma (141), bladder cancer (142–144), lung adenocarcinoma (145), clear cell renal cell carcinoma (146, 147), glioblastoma multiforme (148), HCC (149), gastric cancer (150), and small cell lung cancer (151). Here, PDCD1 is linked to lung adenocarcinoma.