CD274 and familial pancreatic carcinoma: Interestingly, PD-L1 downregulation mediated by USP8 inhibition or depletion was restored after treatment with the proteasome inhibitor MG132 in pancreatic cancer cells, suggesting that USP8 regulates PD-L1 via the proteasome pathway (Fig. 4m, n; Fig. S7f, g).