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 PD-L1 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 tumor-infiltrating 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 acid 76 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.

BackgroundProgrammed death-ligand 1 (PD-L1) is a T-cell inhibitory checkpoint molecule that suppresses antitumor immunity. Anti-PD-L1 antibodies have shown remarkable promise in treating tumors, but the patient response rate is low. Therefore, small-molecule checkpoint inhibitors blocking PD-L1 function are urgently needed.MethodsChanges of protein expression and phosphorylation levels were determined by immunoblotting. The level of Membrane PD-L1 was examined by flow cytometer. Cytotoxicity of T cells and NK cells toward tumor cells were detected using LDH and cell index assays. Lysosome function was investigated by NAG assay. Changes in lysosomal-related genes were measured by RT-PCR. In vivo anti-NSCLC cancer effects were assessed using C57BL/6 mice bearing Lewis tumor xenografts.FindingsWe identified SA-49 as a new regulator of PD-L1 expression from a series of novel aloperine derivatives. SA-49 decreased the expression of PD-L1 in NSCLC cells and enhanced the cytotoxicity of co-cultured T and NK cells toward tumor cells. Importantly, lysosomal pathway contributed to SA-49-mediated down-regulation of PD-L1. SA-49 increased the biogenesis of lysosome and promoted translocation of PD-L1 to lysosome for proteolysis, which was associated with nuclear translocation of MITF. SA-49-induced MITF translocation acted through activation of PKCα and subsequently suppression of GSK3β activity. Furthermore, SA-49 suppressed Lewis tumor xenograft growth by activating immune microenvironment in C57BL/6 mice.InterpretationOur data demonstrate that SA-49 can be used to regulate PD-L1 in cancer cells and trigger its degradation by activating lysosome function.

Programmed cell death ligand 1 (PD-L1)/programmed cell death protein 1 (PD-1) cascade is an effective therapeutic target for immune checkpoint blockade (ICB) therapy. Targeting PD-L1/PD-1 axis by small-molecule drug is an attractive approach to enhance antitumor immunity. Using flow cytometry-based assay, we identify tubeimoside-1 (TBM-1) as a promising antitumor immune modulator that negatively regulates PD-L1 level. TBM-1 disrupts PD-1/PD-L1 interaction and enhances the cytotoxicity of T cells toward cancer cells through decreasing the abundance of PD-L1. Furthermore, TBM-1 exerts its antitumor effect in mice bearing Lewis lung carcinoma (LLC) and B16 melanoma tumor xenograft via activating tumor-infiltrating T-cell immunity. Mechanistically, TBM-1 triggers PD-L1 lysosomal degradation in a TFEB-dependent, autophagy-independent pathway. TBM-1 selectively binds to the mammalian target of rapamycin (mTOR) kinase and suppresses the activation of mTORC1, leading to the nuclear translocation of TFEB and lysosome biogenesis. Moreover, the combination of TBM-1 and anti-CTLA-4 effectively enhances antitumor T-cell immunity and reduces immunosuppressive infiltration of myeloid-derived suppressor cells (MDSCs) and regulatory T (Treg) cells. Our findings reveal a previously unrecognized antitumor mechanism of TBM-1 and represent an alternative ICB therapeutic strategy to enhance the efficacy of cancer immunotherapy.

The optimal combination of antiepileptic drugs (AEDs) for the treatment of refractory partial-onset epilepsy is a perpetual point of debate. While several network meta-analyses (NMAs) have been published, conclusions remain controversial, especially since newer AEDs have been introduced. In our review, we included the newer AEDs to evaluate the comparative efficacy and safety of AEDs for the treatment of refractory partial-onset epilepsy. We searched PubMed, Embase, and the Cochrane Central Register of Controlled Trials (Cochrane Library 2017, Issue 1) from their inception to February 18, 2017. The risk of bias in the included randomized controlled trials (RCTs) was evaluated according to the Cochrane Collaboration's risk of bias tool. An NMA was performed with a Bayesian random-effects model, and we used the surface under the cumulative ranking curve to detect the optimal AEDs. Seventy-six RCTs with 17 AEDs and 20,711 patients were included in the NMAs, which showed that Brivaracetam (BRV), Levetiracetam (LEV), Oxcarbazepine (OXC), Topiramate, Vigabatrin (VGB), and Valproate (VPA) had a greater likelihood of allowing patients to achieve seizure freedom. We also found that LEV was associated with a lower withdrawal rate due to adverse effects than Lacosamide, Eslicarbazepine acetate, OXC, Pregabalin, and Retigabine. LEV, VGB, VPA, and BRV emerged as the agents with the best combination of properties when considering the efficacy and safety outcomes based on the full double-blind treatment period. However, it is critical to perform RCTs and to obtain prospective data from representative cohort studies.

Blocking the PD-1/PD-L1 interaction has become an important strategy for tumor therapy, which has shown outstanding therapeutic effects in clinical settings. However, unsatisfactory response rates and immune-related adverse effects limit the use of anti-PD1/PD-L1 antibodies. Here, we report the discovery and identification of S4-1, an innovative small-molecule inhibitor of PD-L1. In vitro, S4-1 effectively altered the PD-L1/PD-1 interaction, induced PD-L1 dimerization and internalization, improved its localization to endoplasmic reticulum, and thus enhanced the cytotoxicity of peripheral blood mononuclear cells toward tumor cells. In vivo, S4-1 significantly inhibited tumor growth in both lung and colorectal cancer models, particularly in colorectal cancer, where it led to complete clearance of a portion of the tumor cells. Furthermore, S4-1 induced T-cell activation and inversed the inhibitory tumor microenvironment, consistent with the PD-L1/PD-1 pathway blockade. These data support the continued evaluation of S4-1 as an alternative ICB therapeutic strategy.