In Vivo Antitumor Effects of MK615 Led by PD-L1 Downregulation

Cordycepin inhibits glioma growth by downregulating PD-L1 expression via the NOD-like receptor/NFKB1/STAT1 axis

Glioma is a serious primary malignant tumor of the human central nervous system with a poor prognosis and a high recurrence rate; however, inhibition of immune checkpoints can greatly improve the survival rate of patients. The purpose of this study was to investigate the regulation of PD-L1 by cordycepin and the mechanism of its anti-tumor action. The results of previous studies indicate that cordycepin has good anti-proliferative and anti-migratory activities and can induce apoptosis in U251 and T98G cells in vitro. Here, transcriptome sequencing showed that cordycepin may exert anti-tumor effects through the NOD-like receptor signaling pathway. Further intervention with BMS-1, a small molecule inhibitor of PD-L1, was used to explore whether inhibition of PD-L1 affected the regulation of the NOD-like receptor signaling pathway by cordycepin. Mechanistically, on the one hand, cordycepin regulated the expression of NFKB1 and STAT1 through the NOD-like receptor signaling pathway, thereby inhibiting the expression of PD-L1. In addition, inhibition of PD-L1 enhanced the regulation by cordycepin of the NOD-like receptor signaling pathway. On the other hand, cordycepin directly upregulated expression of STAT1 and downregulated that of PD-L1. In vivo studies further showed that cordycepin could downregulate expression of PD-L1 and NFKB1 and upregulate that of STAT1 in glioma xenograft tumor tissues, consistent with the results of in vitro studies. The results suggest that cordycepin may down-regulate the expression of PD-L1 through NOD-like receptor signaling pathway and NFKB signaling pathway, thereby inhibiting the immune escape of glioma, and can be developed as a PD-L1 inhibitor. Our results therefore provide a theoretical foundation for the use of cordycepin in treatment of glioma and enrich our understanding of its pharmacological mechanism.

Harnessing the capacity of phytochemicals to enhance immune checkpoint inhibitor therapy of cancers: A focus on brain malignancies

Brain cancers, particularly glioblastoma multiforme (GBM), are challenging health issues with frequent unmet aspects. Today, discovering safe and effective therapeutic modalities for brain tumors is among the top research interests. Immunotherapy is an emerging area of investigation in cancer treatment. Since immune checkpoints play fundamental roles in repressing anti-cancer immunity, diverse immune checkpoint inhibitors (ICIs) have been developed, and some monoclonal antibodies have been approved clinically for particular cancers; nevertheless, there are significant concerns regarding their efficacy and safety in brain tumors. Among the various tools to modify the immune checkpoints, phytochemicals show good effectiveness and excellent safety, making them suitable candidates for developing better ICIs. Phytochemicals regulate multiple immunological checkpoint-related signaling pathways in cancer biology; however, their efficacy for clinical cancer immunotherapy remains to be established. Here, we discussed the involvement of immune checkpoints in cancer pathology and summarized recent advancements in applying phytochemicals in modulating immune checkpoints in brain tumors to highlight the state-of-the-art and give constructive prospects for future research.

Polyphenols from Prunus mume: extraction, purification, and anticancer activity

Prunus mume is an ancient medicinal herb and food that are commonly used in Asian countries with high nutritional ingredients and biological activities. Polyphenols are important functional components in Prunus mume. To obtain a more efficient extraction process of Prunus mume polyphenols, a single-factor test and response surface method were used. After extraction and purification, the final polyphenol content of Prunus mume (L¹) was up to 90%. Biological experiments showed that L¹ had high anticancer activity against HeLa (125.28 μg mL^-1), HepG2 (117.24 μg mL^-1), MCF-7 (170.19 μg mL^-1), and A549 (121.78 μg mL^-1) in vitro by MTT assay. The combination of DDP and DOX significantly enhanced the anticancer activity of the four cell lines, especially L¹-DOX had the smallest IC₅₀ value of 0.04 μg mL^-1 against HepG2 cells, indicating the combination of drugs had synergistic effects. It is further demonstrated that L¹ could inhibit cell proliferation by inducing apoptosis with ROS detection and confocal fluorescence images. The relative tumor proliferation rate (T/C) was 40.6%, and the tumor inhibition rate was 57.9%, indicating L¹ to have no significant toxicity but high anti-HepG2 activity in vivo. Although the study is very limited, it is anticipated to provide a reference for further exploration of the functionality of the plant.

Novel extracellular role of REIC/Dkk-3 protein in PD-L1 regulation in cancer cells

The adenovirus-REIC/Dkk-3 expression vector (Ad-REIC) has been the focus of numerous clinical studies due to its potential for the quenching of cancers. The cancer-suppressing mechanisms of the REIC/DKK-3 gene depend on multiple pathways that exert both direct and indirect effects on cancers. The direct effect is triggered by REIC/Dkk-3-mediated ER stress that causes cancer-selective apoptosis, and the indirect effect can be classified in two ways: (i) induction, by Ad-REIC-mis-infected cancer-associated fibroblasts, of the production of IL-7, an important activator of T cells and NK cells, and (ii) promotion, by the secretory REIC/Dkk-3 protein, of dendritic cell polarization from monocytes. These unique features allow Ad-REIC to exert effective and selective cancer-preventative effects in the manner of an anticancer vaccine. However, the question of how the REIC/Dkk-3 protein leverages anticancer immunity has remained to be answered. We herein report a novel function of the extracellular REIC/Dkk-3-namely, regulation of an immune checkpoint via modulation of PD-L1 on the cancer-cell surface. First, we identified novel interactions of REIC/Dkk-3 with the membrane proteins C5aR, CXCR2, CXCR6, and CMTM6. These proteins all functioned to stabilize PD-L1 on the cell surface. Due to the dominant expression of CMTM6 among the proteins in cancer cells, we next focused on CMTM6 and observed that REIC/Dkk-3 competed with CMTM6 for PD-L1, thereby liberating PD-L1 from its complexation with CMTM6. The released PD-L1 immediately underwent endocytosis-mediated degradation. These results will enhance our understanding of not only the physiological nature of the extracellular REIC/Dkk-3 protein but also the Ad-REIC-mediated anticancer effects. KEY MESSAGES: • REIC/Dkk-3 protein effectively suppresses breast cancer progression through an acceleration of PD-L1 degradation. • PD-L1 stability on the cancer cell membrane is kept high by binding with mainly CMTM6. • Competitive binding of REIC/Dkk-3 protein with CMTM6 liberates PD-L1, leading to PD-L1 degradation.

Pivotal role of PD-1/PD-L1 immune checkpoints in immune escape and cancer progression: Their interplay with platelets and FOXP3+Tregs related molecules, clinical implications and combinational potential with phytochemicals

Immune checkpoint proteins including programmed cell death protein 1 (PD-1), its ligand PD-L1 and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) are involved in proliferation, angiogenesis, metastasis, chemoresistance via immune escape and immune tolerance by disturbing cytotoxic T cell activation. Though many clinical trials have been completed in several cancers by using immune checkpoint inhibitors alone or in combination with other agents to date, recently multi-target therapy is considered more attractive than monotherapy, since immune checkpoint proteins work with other components such as surrounding blood vessels, dendritic cells, fibroblasts, macrophages, platelets and extracellular matrix within tumor microenvironment. Thus, in the current review, we look back on research history of immune checkpoint proteins and discuss their associations with platelets or tumor cell induced platelet aggregation (TCIPA) and FOXP3+ regulatory T cells (Tregs) related molecules involved in immune evasion and tumor progression, clinical implications of completed trial results and signaling networks by phytochemicals for combination therapy with immune checkpoint inhibitors and suggest future research perspectives.

Current and potential trends in the bioactive properties and health benefits of Prunus mume Sieb. Et Zucc: a comprehensive review for value maximization

Prunus mume Sieb. Et Zucc (P. mume) is an acidic fruit native to China (named Chinese Mei or greengage plum). It is currently cultivated in several Asian countries, including Japan ("Ume"), Korea (Maesil), and Vietnam (Mai or Mo). Due to its myriad nutritional and functional properties, it is accepted in different countries, and its characteristics account for its commercialization. In this review, we summarize the information on the bioactive compounds from the fruit of P. mume and their structure-activity relationships (SAR); the pulp has the highest enrichment of bioactive chemicals. The nutritional properties of P. mume and the numerous uses of its by-products make it a potential functional food. P. mume extracts exhibit antioxidant, anticancer, antimicrobial, and anti-hyperuricaemic properties, cardiovascular protective effects, and hormone regulatory properties in various in vitro and in vivo assays. SAR shows that the water solubility, molecular weight, and chemical conformation of P. mume extracts are closely related to their biological activity. However, further studies are needed to evaluate the fruit's potential nutritional and functional therapeutic mechanisms. The industrial process of large-scale production of P. mume and its extracts as functional foods or nutraceuticals needs to be further optimized.

Phytochemicals in Cancer Immune Checkpoint Inhibitor Therapy

The interaction of immune checkpoint molecules in the tumor microenvironment reduces the anti-tumor immune response by suppressing the recognition of T cells to tumor cells. Immune checkpoint inhibitor (ICI) therapy is emerging as a promising therapeutic option for cancer treatment. However, modulating the immune system with ICIs still faces obstacles with severe immunogenic side effects and a lack of response against many cancer types. Plant-derived natural compounds offer regulation on various signaling cascades and have been applied for the treatment of multiple diseases, including cancer. Accumulated evidence provides the possibility of efficacy of phytochemicals in combinational with other therapeutic agents of ICIs, effectively modulating immune checkpoint-related signaling molecules. Recently, several phytochemicals have been reported to show the modulatory effects of immune checkpoints in various cancers in in vivo or in vitro models. This review summarizes druggable immune checkpoints and their regulatory factors. In addition, phytochemicals that are capable of suppressing PD-1/PD-L1 binding, the best-studied target of ICI therapy, were comprehensively summarized and classified according to chemical structure subgroups. It may help extend further research on phytochemicals as candidates of combinational adjuvants. Future clinical trials may validate the synergetic effects of preclinically investigated phytochemicals with ICI therapy.

Comprehensive Review of Phytochemical Constituents, Pharmacological Properties, and Clinical Applications of Prunus mume

Prunus mume is one of the most ancient medicinal herbs and health foods commonly used in Asian countries. It is widely used as a constituent of many medicinal preparations and as a food ingredient for its beneficial health effects. In this review, we retrieved reports from PubMed, embase, Scopus, and SciFinder databases, to collect extensive scientific evidence on the phytochemical constituents, pharmacological properties, and clinical applications of Prunus mume. The literature review revealed that approximately 192 compounds have been isolated from different parts of the plant, and their molecular structures have been identified. The pharmacological properties of the plant, including anti-diabetic, liver-protective, antitumor, antimicrobial, antioxidant, and anti-inflammatory activities, as well as their underlying mechanisms, have been clarified by in vitro and in vivo studies. Clinical studies, although very limited, have been highlighted in this review to provide a reference for further exploration on therapeutic applications of the plant.

Treatment of lymphomas via regulating the Signal transduction pathways by natural therapeutic approaches: A review

Lymphoma is a heterogeneous group of malignancies, which comprises 4.2 % of all new cancer cases and 3.3 % of all cancer deaths in 2019, globally. The dysregulation of immune system, certain bacterial or viral infections, autoimmune diseases, and immune suppression are associated with a high risk of lymphoma. Although several conventional strategies have improved during the past few decades, but their detrimental impacts remain an obstacle to be resolved. However, natural compounds are considered a good option in the treatment of lymphomas because of their easy accessibility, specific mode of action, high biodegradability, and cost-effectiveness. Vegetables, fruits, and beverages are the primary sources of natural active compounds. The present review investigated the activities of different natural medicinal compounds including curcumin, MK615, resveratrol, bromelain, EGCG, and Annonaceous acetogenins to treat lymphomas. Moreover, in vitro and in vivo studies, classification, risk factors, and diagnosis of lymphoma are also discussed in the present review. The accumulated data proposed that natural compounds regulate the signaling pathways at the level of cell proliferation, apoptosis, and cell cycle to exhibit anti-lymphoma activities both in-vivo and in-vitro studies and suggested that these active compounds could be a good therapeutic option in the treatment of different types of lymphomas.

Detection of PD-L1 Expression and Its Clinical Significance in Circulating Tumor Cells from Patients with Non-Small-Cell Lung Cancer

Background

The expression of programmed cell death ligand 1(PD-L1) is related to the efficacy of immune checkpoint inhibitors on patients with non-small cell lung cancer (NSCLC), but tumor tissue (TT) samples are difficult to obtain, and initial TT samples are difficult to reflect the spatial-temporal heterogeneity. Therefore, we explored the feasibility of separating circulating tumor cells (CTCs) and detecting PD-L1 expression on CTCs.

Patients and Methods

Peripheral blood specimens were sampled from 66 NSCLC patients, and CTCs were separated by membrane filtration based on size. For 59 patients with paired TT specimens, the expression of PD-L1 in their CTCs and TTs was determined using the immunohistochemistry and immunocytochemistry based on 28–8 antibody, respectively. The PD-L1 expression in TTs was set as a gold standard for calculation of sensitivity, specificity, consistency, positive predictive value (PPV), and negative predictive value (NPV), and the Cohen kappa coefficient for CTCs and paired TTs was calculated. In addition, the T-test, Chi-square test, and Mann–Whitney U-test were adopted to analyze the correlation of clinical pathological features and prognosis with PD-L1 expression.

Results

Sensitivity, specificity, concordance, PPV and NPV of detecting PD-L1 in CTCs of the 41 initial treated patients were 88.89%, 73.91%, 80%, 72.73% and 89.47%, respectively, and the Cohen kappa coefficient of CTC and paired TTs was 0.613. The univariate analysis of survival showed that the progression-free survival time of initial treated patients with positive PD-L1 expression was shorter than that of those with negative PD-L1 expression in CTCs or TTs (P>0.05), and the positive PD-L1 expression in CTCs or TTs had nothing to do with age, sex, smoking status, histological type, and stage (P > 0.05).

Conclusion

The study confirms the feasibility of CTC PD-L1 detection in peripheral blood and lays a foundation for exploring real-time and individualized immunotherapy molecular biomarkers.

Anticancer properties of Prunus mume extracts (Chinese plum, Japanese apricot)

ETHNOPHARMACOLOGICAL RELEVANCE

Extracts of the fruit of Prunus mume (Rosaceae) have been used for a long time in Eastern Asia, in many culinary and medicinal preparations. The plant originates from the south of mainland China (named méi) and was introduced later in Japan (ume), Korea (maesil) and Vietnam (mai or mo). Extracts of the fruits (Chinese plum or Japanese apricot, 'Nanko' mume cultivar of Prunus mume Sieb. et Zucc.) are used in traditional Chinese and Japanese medicine, and various Korean medical preparations, for more than 2000 years. The medicinal use of the flesh of the fruits is cited in ancient Japanese monographies (such as Shokokukodenhiho published in 1817).

AIM OF THE STUDY

To analyze the anticancer activities of P. mume extracts and their potential use to prevent or treat cancers. The use of P. mume extracts to alleviate the side effects of chemotherapy, notably drug-induced gastro-intestinal toxicities, is also reviewed.

METHODS

Extensive database retrieval, such as SciFinder and PubMed, was performed by using keywords such as "Prunus mume", "Chinese plum", "Japanese apricot", and "cancer". In addition, relevant textbooks, patents, reviews, and digital documents (in English) were consulted to collate all available scientific literature and to provide a complete science-based survey of the topic.

RESULTS

P. mume extracts display hepatoprotective, anti-inflammatory, antioxidative and antibacterial effects, as well as anticancer properties. A survey of the antitumor activities of MK615 and other P. mume extracts is provided here, with information about the natural products found in the extracts (such as ursolic acid and oleanic acid) and the mechanisms of action of these extracts. MK615 inhibits proliferation and induces apoptotic death of different types of cancer cells from both solid and hematological tumors.

CONCLUSION

The pool of in vitro data and signs of anticancer activities in mice models and in Human, although very limited, support the use of this extract to treat cancer, notably gastro-intestinal tumors. However, more robust evidence of anticancer activity in Human are awaited. Beyond cancer treatment, the use of P. mume extracts to prevent or to treat mucositis and other gastro-intestinal damages induced by anticancer drugs is underlined. The woody plant Prunus mume, a member of the Rosaceae family, has a long plantation history in China, and has widely been planted in Asia due to its high ornamental value (colorful corollas, pleasant fragrance, weeping trait) and the culinary, nutritional and medicinal potential of the fruits from the specie Prunus mume Sieb. et Zucc (Mei). Over the past 20 years the therapeutic potential of the extract of Japanese apricot "Ume" has been regularly reported. Anti-bacterial, anti-oxidative, anti-inflammatory and anti-cancer properties have been described. A complete analysis of the published scientific literature on Ume and cancer is presented here.