SA-49, a novel aloperine derivative, induces MITF-dependent lysosomal degradation of PD-L1

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

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.

PD-L1 degradation pathway and immunotherapy for cancer

Programmed death ligand 1 (PD-L1, CD274) is an essential immune checkpoint protein that binds to programmed death 1 (PD-1) on T-lymphocytes. T cell plays a critical role in killing cancer cells while the cancer cell exhibits immune escape by the expression of PD-L1. The binding of PD-L1 to PD-1 inhibits T cell proliferation and activity, leading to tumor immunosuppression. Increasing evidence shows that PD-L1 protein undergoes degradation in proteasomes or lysosomes by multiple pathways, leading to enhanced immunotherapy for cancer. Although some specific drugs induce PD-L1 degradation and increase antitumor activity, the combination of these drugs with PD-L1/PD-1 blockade significantly enhances cancer immunotherapy. In this review, we have discussed the interaction of PD-L1 degradation with cancer immunotherapy.

An iRGD peptide fused superantigen mutant induced tumor-targeting and T lymphocyte infiltrating in cancer immunotherapy

Solid tumors are intrinsically resistant to immunotherapy because of the major challenges including the immunosuppression and poor penetration of drugs and lymphocytes into solid tumors due to the complicated tumor microenvironment (TME). Our previous study has created a novel superantigen mutant ST-4 to efficiently active the T lymphocytes and alleviate immune suppression. In the present study, to accumulate ST-4 into the TME, we constructed a recombinant protein, ST-4-iRGD, by fusing ST-4 to a tumor-homing peptide, iRGD. We hypothesized that ST-4-iRGD could internalize into the TME through iRGD-mediated tumor targeting and tumor tissue penetrating to activate the regional immunoreaction. The results of in vitro studies showed that ST-4-iRGD achieved improved tumor targeting and cytotoxicity in mouse B16F10 melanoma cells. The iRGD-mediated tumor tissue penetration was further confirmed by imaging and immunofluorescence studies in vivo, wherein higher distribution of ST-4-iRGD was observed in the mouse 4T1 breast tumor model. Moreover, ST-4-iRGD exhibited enhanced anti-solid tumor characteristics and induced improved lymphocyte infiltration in the B16F10 and 4T1 models. In conclusion, using iRGD to facilitate better dissemination of the therapeutic agent ST-4 throughout a solid tumor mass is feasible, and ST-4-iRGD may be a potential candidate for efficient cancer immunotherapy in the future.

Research Progress on Anti-Inflammatory Effects and Mechanisms of Alkaloids from Chinese Medical Herbs

As the spectrum of diseases keeps changing and life pace keeps going faster, the probability and frequency of diseases caused by human inflammatory reactions also keep increasing. How to develop effective anti-inflammatory drugs has become the hotspot of researches. It has been found that alkaloids from Chinese medical herbs have anti-inflammatory, analgesic, antitumor, anticonvulsant, diuretic, and antiarrhythmic effects, among which the anti-inflammatory effect is very prominent and commonly used in the treatment of rheumatoid arthritis, ankylosing spondylitis, and other rheumatic immune diseases, but its mechanism of action has not been well explained. Based on this, this paper will classify alkaloids according to structural types and review the plant sources, applicable diseases, and anti-inflammatory mechanisms of 16 kinds of alkaloids commonly used in clinical treatment, such as berberine, tetrandrine, and stephanine, with the aim of providing a reference for drug researches and clinical applications.

Lysosome as the Black Hole for Checkpoint Molecules

Lysosomes, as digestive organelles full of hydrolases, have complex functions and play an important role in cellular physiological and pathological processes. In normal physiological conditions, lysosomes can sense the nutritional state and be responsible for recycling raw materials to provide nutrients, affecting cell signaling pathways and regulating cell proliferation. Lysosomes are related to many diseases and associated with metastasis and drug resistance of tumors. In recent years, much attention has been paid to the tumor immunotherapy especially immune checkpoint blockade therapy. Accumulating data suggest that lysosomes may serve as a major destruction for immune checkpoint molecules, and secretory lysosomes can temporarily store immune checkpoint proteins. Once activated, the compounds contained in secretory lysosomes are released to the surface of cell membrane rapidly. Inhibitions of lysosomes can overcome the chemoresistance of some tumors and enhance the efficacy of immunotherapy.

Proteasomal and lysosomal degradation for specific and durable suppression of immunotherapeutic targets

Cancer immunotherapy harness the body’s immune system to eliminate cancer, by using a broad panel of soluble and membrane proteins as therapeutic targets. Immunosuppression signaling mediated by ligand-receptor interaction may be blocked by monoclonal antibodies, but because of repopulation of the membrane via intracellular organelles, targets must be eliminated in whole cells. Targeted protein degradation, as exemplified in proteolysis targeting chimera (PROTAC) studies, is a promising strategy for selective inhibition of target proteins. The recently reported use of lysosomal targeting molecules to eliminate immune checkpoint proteins has paved the way for targeted degradation of membrane proteins as crucial anti-cancer targets. Further studies on these molecules’ modes of action, target-binding “warheads”, lysosomal sorting signals, and linker design should facilitate their rational design. Modifications and derivatives may improve their cell-penetrating ability and the in vivo stability of these pro-drugs. These studies suggest the promise of alternative strategies for cancer immunotherapy, with the aim of achieving more potent and durable suppression of tumor growth. Here, the successes and limitations of antibody inhibitors in cancer immunotherapy, as well as research progress on PROTAC- and lysosomal-dependent degradation of target proteins, are reviewed.

Quinolizidine alkaloids derivatives from Sophora alopecuroides Linn: Bioactivities, structure-activity relationships and preliminary molecular mechanisms

Quinolizidine alkaloids, as essential active ingredients extracted from Sophora alopecuroides Linn, have been well concerned in the past several decades owing to the unique structural features and numerous pharmacological activities. Quinolizidine alkaloids consist of matrine, oxymatrine, sophoridine, sophocarpine and aloperine etc. Additionally, quinolizidine alkaloids exert various excellent activities, including anti-cancer, anti-inflammation, anti-fibrosis, anti-virus and anti-arrhythmia regulations. In this review, we comprehensively clarify the pharmacological activities of quinolizidine alkaloids, as well as the relationship between biological function and structure-activity of substituted quinolizidine alkaloids. We believe that biological agents based on the pharmacological functions of quinolizidine alkaloids could be well applied in clinical practice.

Autophagy Modulation in Human Thyroid Cancer Cells following Aloperine Treatment

Aloperine, an alkaloid isolated from Sophoraalopecuroides, exhibits multiple pharmacological activities including anti-inflammatory, antioxidant, antiallergic, antinociceptive, antipathogenic, and antitumor effects. Furthermore, it exerts protective effects against renal and neuronal injuries. Several studies have reported antitumor effects of aloperine against various human cancers, including multiple myeloma; colon, breast, and prostate cancers; and osteosarcoma. Cell cycle arrest, apoptosis induction, and tumorigenesis suppression have been demonstrated following aloperine treatment. In a previous study, we demonstrated antitumor effects of aloperine on human thyroid cancer cells through anti-tumorigenesis and caspase-dependent apoptosis induction via the Akt signaling pathway. In the present study, we demonstrated the modulation of the autophagy mechanism following the incubation of multidrug-resistant papillary and anaplastic human thyroid cancer cells with aloperine; we also illustrate the underlying mechanisms, including AMPK, Erk, JNK, p38, and Akt signaling pathways. Further investigation revealed the involvement of the Akt signaling pathway in aloperine-modulated autophagy in human thyroid cancer cells. These results indicate a previously unappreciated function of aloperine in autophagy modulation in human thyroid cancer cells.

Identification of Aloperine as an anti-apoptotic Bcl2 protein inhibitor in glioma cells

Objective

Aloperine (ALO), an alkaloid isolated from the leaves of Sophora alopecuroides, has been suggested to exhibit anti-inflammatory and anti-tumor properties and is traditionally used to treat various human diseases, including cancer. However, limited information is available about the mechanisms that determine the anti-tumor activities of ALO.

Methods

Herein, through comprehensive bioinformatics methods and in vitro functional analyses, we evaluated the detailed anti-tumor mechanisms of ALO.

Results

Using the databases Bioinformatics analysis tool for molecular mechanism of traditional Chinese medicine and PubChem Project, we identified the potential targets of ALO. A protein–protein interaction network was constructed to determine the relationship among these probable targets. Functional enrichment analysis revealed that ALO is potentially involved in the induction of apoptosis. In addition, molecular docking demonstrated that ALO expectedly docks into the active pocket of the Bcl2 protein, suggesting Bcl2 as a direct target of ALO. Moreover, western blot and qPCR analysis showed that ALO downregulated Bcl2 expression in human glioma cell lines, SK-N-AS and U118. Using flow cytometry methods, we further confirmed that ALO significantly promotes apoptosis in SK-N-AS and U118 cell lines, similar to the effect induced by ABT-737, a well-known Bcl2 inhibitor. In addition, Bcl-2 overexpression could rescue ALO-induced Bcl-2 inhibition and suppress pro-apoptotic effects in glioma cells.

Conclusion

Taken together, these findings suggest that the natural agent ALO effectively enhances apoptosis by acting as a potential Bcl2 inhibitor in human glioma cells.