CD274 and head and neck squamous cell carcinoma: Additionally, in a variety of solid tumors, including hepatocellular carcinoma, pancreatic cancer, gastric cancer, head and neck squamous cell carcinoma, and breast cancer, we observed a positive correlation between the EZH2 repression signature score and both PD‐L1 and USP22, suggesting that the regulatory effect of the EZH2‐USP22‐PD‐L1 axis may be widely present in solid tumors (Figure S7D, Supporting Information).