Tumor cells also regulate the ubiquitination of PD-L1, a PD-1 ligand, altering the expression of leucine-rich repeat kinase 2, ring finger protein 125, TRIM28, circ-0000512, USP22, OTUB1, etc. 82, 83, 84, 85, 86, 87 (Table 2). Here, USP22 is linked to neoplasm.