Berberine diminishes cancer cell PD-L1 expression and facilitates antitumor immunity via inhibiting the deubiquitination activity of CSN5

摘要

Programmed cell death-1(PD-1)/programmed cell death ligand-1(PD-L1)blocking therapy has become a major pillar of cancer immunotherapy.Compared with antibodies targeting,small-molecule checkpoint inhibitors which have favorable pharmacokinetics are urgently needed.Here we identified berberine(BBR),a proven anti-inflammation drug,as a negative regulator of PDL1 from a set of traditional Chinese medicine(TCM)chemical monomers.BBR enhanced the sensitivity of tumour cells to co-cultured T-cells by decreasing the level of PD-L1 in cancer cells.In addition,BBR exerted its antitumor effect in Lewis tumor xenograft mice through enhancing tumorinfiltrating T-cell immunity and attenuating the activation of immunosuppressive myeloid-derived suppressor cells(MDSCs)and regulatory T-cells(Tregs).BBR triggered PD-L1 degradation through ubiquitin(Ub)/proteasome-dependent pathway.Remarkably,BBR selectively bound to the glutamic acid76 of constitutive photomorphogenic-9 signalosome 5(CSN5)and inhibited PD-1/PD-L1 axis through its deubiquitination activity,resulting in ubiquitination and degradation of PD-L1.Our data reveals a previously unrecognized antitumor mechanism of BBR,suggesting BBR is small-molecule immune checkpoint inhibitor for cancer treatment.