Several E3 ligase (Cullin3-SPOP, c‐Cbl, and β-TrCP) and deubiquitinases (CSN5, USP9X, USP21, OTUB1, and USP22) have been reported to regulate PD-L1 protein degradation in cancer cells [14–16, 23–25], indicating posttranslational modification plays an important roles in regulation of PD-L1 stability. The gene discussed is USP21; the disease is cancer.