Brusatol: A potential anti-tumor quassinoid from Brucea javanica

Brusatol improves the efficacy of an anti-mouse-PD-1 antibody via inhibiting programmed cell death 1 ligand 1 expression in a murine head and neck squamous cell carcinoma model

OBJECTIVE

Combing PD-1/PD-L1 immune checkpoint inhibitors with natural products has exhibited better efficacy than monotherapy. Hence, the purpose of this research was to examine the anti-cancer effects of brusatol, a natural quassinoid-terpenoid derived from Brucea javanica, when used in conjunction with an anti-mouse-PD-1 antibody in a murine head and neck squamous cell carcinoma (HNSCC) model and elucidate underlying mechanisms.

DESIGN

A murine HNSCC model and an SCC-15 cell xenograft nude mouse model were established to investigate the anti-cancer effects of brusatol and anti-PD-1 antibody. Mechanistic studies were performed using immunohistochemistry. Cell proliferation, migration, colony formation, and invasion were evaluated by MTT, migration, colony formation, and transwell invasion assays. PD-L1 levels in oral squamous cell carcinoma (OSCC) cells were assessed through qRT-PCR, flow cytometry, and western blotting assays. The impact of brusatol on Jurkat T cell function was assessed by an OSCC/Jurkat co-culture assay.

RESULTS

Brusatol improved tumor suppression by anti-PD-1 antibody in HNSCC mouse models. Mechanistic studies revealed brusatol inhibited tumor cell growth and angiogenesis, induced apoptosis, increased T lymphocyte infiltration, and reduced PD-L1 expression in tumors. Furthermore, in vitro assays confirmed brusatol inhibited PD-L1 expression in OSCC cells and suppressed cell migration, colony formation, and invasion. Co-culture assays indicated that brusatol's PD-L1 inhibition enhanced Jurkat T cell-mediated OSCC cell death and reversed the inhibitory effect induced by OSCC cells.

CONCLUSIONS

Brusatol improves anti-PD-1 antibody efficacy by targeting PD-L1, suggesting its potential as an adjuvant in anti-PD-1 immunotherapy.

Six undescribed guaianolide-type sesquiterpenes from the aerial parts of Daphne penicillata

Six undescribed guaianolide sesquiterpenes (1-6) were obtained from the aerial parts of Daphne penicillata. Their structures and absolute configuration were elucidated by HRESIMS, NMR analyses, ECD calculations and single-crystal X-ray diffraction analysis. Structurally, all compounds possess the typical 5,7-fused system of 8,12-guaianolides and this guaianolide-type was first reported to be isolated from Daphne penicillata. All compounds (1-6) were evaluated for anti-inflammatory and cytotoxic activity. Among them, compounds 1 and 5 showed moderate inhibitory effects on LPS-induced NO production in BV2 cells and 4 displayed potential inhibition against Hep3B cells with an IC50 value of 7.33 μM.

Prediction of network pharmacology, molecular docking-based strategy, and vitro assays to determine potential pharmacological mechanism of Dioscoreae bulbiferae and Bruceae fructus against laryngocarcinoma

BACKGROUND

Based on network pharmacology, molecular docking, and vitro assays, investigate the probable pharmacological mechanism of Dioscoreae bulbiferae and Bruceae fructus in the treatment of laryngocarcinoma.

METHODS

The active components and targets of Dioscoreae bulbiferae and Bruceae fructus were retrieved from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform database. Targets linked with laryngocarcinoma were gathered from the GeneCards, DisGeNET, and DrugBank databases. The String database was utilized to build a protein-protein interaction network of common medication and illness targets, after which the core targets were filtered out. The Metascape database served for gene ontology enrichment and Kyoto encyclopedia of genes and genomes pathway analysis of common targets. AutoDock then performed molecular docking between the essential component and the vital target. To investigate the biological effects of diosbulbin B, we assessed the viability of laryngocarcinoma cells after diosbulbin B therapy using the Mahalanobis Taguchi system technique. Following that, we looked at how diosbulbin B affected colony formation after 14 days of culture of treated cells. Flow cytometry was utilized to detect apoptosis in order to examine the influence of diosbulbin B on laryngocarcinoma cell apoptosis.

RESULTS

According to a study of the literature, the fundamental components of Dioscoreae bulbiferae and Bruceae fructus in the treatment of laryngocarcinoma include brusatol and diosbulbin B, which may operate on core targets such as cyclin D1, Cyclin Dependent Kinase Inhibitor 1A, and E2F Transcription Factor 1. The significant pathways discovered using Kyoto encyclopedia of genes and genomes enrichment analysis were the phosphoinositide 3-kinase-protein kinase B signaling route, the tumor necrosis factor signaling pathway, and so on. These pathways primarily influence the development and prognosis of laryngeal cancer by controlling cell growth, cell proliferation, angiogenesis, tumorigenesis, and metastasis. The molecular docking studies revealed that the affinity between the heart and crucial targets was robust. The results of vitro assays indicate that diosbulbin B suppressed Hep-2 cell activity in a concentration-dependent manner. Besides, diosbulbin B has powerful antiproliferative properties in Hep-2 cells. Flow cytometry results showed that diosbulbin B promoted laryngocarcinoma cell apoptosis in a concentration-dependent manner.

CONCLUSION

The article delivered a preliminary discussion of the probable mechanism of Dioscoreae bulbiferae and Bruceae fructus in the treatment of laryngocarcinoma, which can serve as a theoretical basis and evidence for subsequent experimental investigation.

Natural Nrf2 Inhibitors: A Review of Their Potential for Cancer Treatment

Nuclear factor erythroid 2-related factor 2 (Nrf2), a transcription factor that regulates redox homeostasis, plays a pivotal role in several cellular processes such as cell proliferation and survival, and has been found to be aberrantly activated in many cancers. As one of the key oncogenes, Nrf2 represents an important therapeutic target for cancer treatment. Research has unraveled the main mechanisms underlying the Nrf2 pathway regulation and the role of Nrf2 in promoting tumorigenesis. Many efforts have been made to develop potent Nrf2 inhibitors, and several clinical trials are being conducted on some of these inhibitors. Natural products are well-recognized as a valuable source for development of novel therapeutics for cancer. So far, a number of natural compounds have been identified as Nrf2 inhibitors, such as apigenin, luteolin, and quassinoids compounds including brusatol and brucein D. These Nrf2 inhibitors have been found to mediate an oxidant response and display therapeutic effects in different types of human cancers. In this article, we reviewed the structure and function of the Nrf2/Keap1 system and the development of natural Nrf2 inhibitors with an emphasis on their biological function on cancer. The current status regarding the Nrf2 as a potential therapeutic target for cancer treatment was also summarized. It is hoped that this review will stimulate research on naturally occurring Nrf2 inhibitors as therapeutic candidates for cancer treatment.

HOXB9 a miR-122-5p regulated gene, suppressed the anticancer effects of brassaol by upregulating SCD1 expression in melanoma

Brusatol (Bru), a Chinese medicine Brucea javanica extract, has a variety of antitumour effects. However, its role and underlying mechanism in melanoma have not been fully elucidated. In this study, we found that brusatol inhibited melanoma cell proliferation and migration and promoted cell apoptosis in vitro, in addition to suppressing melanoma cell tumorigenesis in vivo. Further studies on the mechanism revealed that brusatol significantly downregulated the expression of stearoyl-CoA desaturase 1 (SCD1). Increased SCD1 expression could impair the antitumour effects of brusatol on melanoma cells. Subsequently, we found that HOXB9, an important transcription factor, was directly bound to the promoter of SCD1, facilitating its transcription. Overexpression of HOXB9 inhibited brusatol-induced SCD1 reduction and promoted cell survival. Furthermore, our results revealed that miR-122-5p was significantly increased in response to brusatol treatment and led to a decrease in HOXB9 in melanoma. Collectively, our data suggested that the miR-122-5p/HOXB9/SCD1 axis might play an important role in the antitumour effects of brusatol and that brusatol might have potential clinical implications in melanoma therapy.

Combinatorial Implications of Nrf2 Inhibitors with FN3K Inhibitor: In vitro Breast Cancer Study

BACKGROUND

Platinum derivatives are chemotherapeutic agents preferred for the treatment of cancers including breast cancer. Oxaliplatin is an anticancer drug that is in phase II studies to treat metastatic breast cancer. However, its usage is constrained by chemoresistance and dose-related side effects.

OBJECTIVE

The objective of this study is to examine the combinatorial efficacy of brusatol, an Nrf2 blocker, with oxaliplatin (a proven FN3K blocker in our study) in mitigating breast cancer growth in vitro.

METHODS

We performed cytotoxicity assays, combination index (CI) analysis, colony formation assays, apoptosis assays, and Western blotting.

RESULTS

Results of our study described the chemosensitizing efficacy of brusatol in combination with lowdose oxaliplatin against breast cancer through synergistic effects in both BT-474 and T47D cells. A significant mitigation in the migration rate of these cancer cells was observed with the combination regimen, which is equivalent to the IC-50 dose of oxaliplatin (125 μM). Furthermore, ROS-mediated and apoptotic modes of cell death were observed with a combinatorial regimen. Colony formation of breast cancer cell lines was mitigated with a combinatorial regimen of bursatol and oxaliplatin than the individual treatment regimen. FN3K expression downregulated with oxaliplatin in T47D cells. The mitigation of FN3K protein expression with a combination regimen was not observed but the Nrf2 downstream antioxidant signaling proteins were significantly downregulated with a combination regimen similar to individual drug regimens.

CONCLUSION

Our study concluded the combination efficacy of phytochemicals like brusatol in combination with low-dose oxaliplatin (FN3K blocker), which could enhance the chemosensitizing effect in breast cancer and minimize the overall dose requirement of oxaliplatin.

Smart Fe3O4@ZnO Core-Shell Nanophotosensitizers Potential for Combined Chemo and Photodynamic Skin Cancer Therapy Controlled by UVA Radiation

Purpose

Photodynamic therapy (PDT) is a non-invasive therapeutic modality that is used for several types of cancer and involves three essential elements (light, photosensitizer (PS), and oxygen). However, clinical PS is limited by the low yield of reactive oxygen species (ROS) and a long retention time. Therefore, developing a low-cost PS that can significantly increase ROS yield in a short time is of utmost importance.

Methods

In this study, brusatol (Bru) was loaded on the surface of ultraviolet A (UVA)-responsive zinc oxide (ZnO)-coated magnetic nanoparticles (Fe₃O₄@ZnO-Bru). The PS was well characterized by transmission electron microscopy (TEM), Fourier Transform infrared spectroscopy (FTIR), a superconducting quantum interference device, and dynamic light scattering (DLS). 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) and Hoechst staining were used to determine the inhibitory effect of Fe₃O₄@ZnO-Bru on squamous cell carcinoma cells (SCC) with or without UVA radiation. Intracellular ROS levels and expression of the Nrf2 signaling pathway were also determined.

Results

FTIR showed that Bru was successfully loaded on Fe₃O₄@ZnO. Fe₃O₄@ZnO-Bru was superparamagnetic, and the zeta potential was 8.86 ± 0.77 mV. The Bru release behavior was controlled by UVA. Fe₃O₄@ZnO-Bru with UVA irradiation induced an increase of 48% ROS productivity compared to Fe₃O₄@ZnO-Bru without UVA irradiation, resulting in a strong inhibitory effect on SCC. Furthermore, Fe₃O₄@ZnO-Bru nanocomposites (Fe₃O₄@ZnO-Bru NCs) had nearly no toxic effect on healthy cells without UVA radiation. The released Bru could significantly inhibit the Nrf2 signaling pathway to reduce the activity of scavenging excess ROS in SCC.

Conclusion

In this study, Fe₃O₄@ZnO-Bru was successfully synthesized. PDT was combined with photochemotherapy, which exhibited a higher inhibitory effect on SCC. It can be inferred that Fe₃O₄@ZnO-Bru holds great potential for skin SCC therapy.

Potential cancer treatment effects of brusatol or eriodictyol combined with 5-fluorouracil (5-FU) in colorectal cancer cell

Colorectal cancer is among the most frequently diagnosed cancers in patients today. In the treatment of this disease, combination or multicomponent therapy has been identified as a potential method to improve patient response and delay side effects. The aim of this study was to determine the effects on cell viability of commercial Bru and Erio used together with the anticancer drug 5-FU in the human colorectal cancer (CRC) cell line (HT-29 cell line) for the first time, as far as can be determined from available literature at this time. Additionally, the research seeks to study any potential effects on apoptosis. For this purpose, the effects of independent and combined treatments of the aforementioned agents on cell viability were investigated through the MTT experiment. Apoptotic effects were determined by Annexin V/PI and real-time PCR methods. In addition, a cell cycle analysis was used to determine the distribution of cells in the cycle. Data from experiments for 48 h showed that Bru, alone or in combination with 5-FU, is capable of causing an increase in the percentage of apoptotic cells in HT-29 cells compared to those of Erio alone or in combination with 5-FU. A significant increase in the level of bax and caspase-3 apoptotic genes was also detected in combinations of IC₅₀ concentrations of Bru and 5-FU. These findings suggest that unlike Erio, Bru alone or in combination with 5-FU may be useful for increasing the effects of 5-FU used in the treatment of CRC and to provide data on alternative treatment approaches.

Role of Nrf2 Signaling Cascade in Breast Cancer: Strategies and Treatment

Breast cancer is the second leading cancer among all types of cancers. It accounts for 12% of the total cases of cancers. The complex and heterogeneous nature of breast cancer makes it difficult to treat in advanced stages. The expression of various enzymes and proteins is regulated by several molecular pathways. Oxidative stress plays a vital role in cellular events that are generally regulated by nuclear factor erythroid 2-related factor 2 (Nrf2). The exact mechanism of Nrf2 behind cytoprotective and antioxidative properties is still under investigation. In healthy cells, Nrf2 expression is lower, which maintains antioxidative stress; however, cancerous cells overexpress Nrf2, which is associated with various phenomena, such as the development of drug resistance, angiogenesis, development of cancer stem cells, and metastasis. Aberrant Nrf2 expression diminishes the toxicity and potency of therapeutic anticancer drugs and provides cytoprotection to cancerous cells. In this article, we have discussed the attributes associated with Nrf2 in the development of drug resistance, angiogenesis, cancer stem cell generation, and metastasis in the specific context of breast cancer. We also discussed the therapeutic strategies employed against breast cancer exploiting Nrf2 signaling cascades.

Cancer Chemopreventive Role of Dietary Terpenoids by Modulating Keap1-Nrf2-ARE Signaling System—A Comprehensive Update

ROS, RNS, and carcinogenic metabolites generate excessive oxidative stress, which changes the basal cellular status and leads to epigenetic modification, genomic instability, and initiation of cancer. Epigenetic modification may inhibit tumor-suppressor genes and activate oncogenes, enabling cells to have cancer promoting properties. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that in humans is encoded by the NFE2L2 gene, and is activated in response to cellular stress. It can regulate redox homoeostasis by expressing several cytoprotective enzymes, including NADPH quinine oxidoreductase, heme oxygenase-1, UDP-glucuronosyltransferase, glutathione peroxidase, glutathione-S-transferase, etc. There is accumulating evidence supporting the idea that dietary nutraceuticals derived from commonly used fruits, vegetables, and spices have the ability to produce cancer chemopreventive activity by inducing Nrf2-mediated detoxifying enzymes. In this review, we discuss the importance of these nutraceuticals in cancer chemoprevention and summarize the role of dietary terpenoids in this respect. This approach was taken to accumulate the mechanistic function of these terpenoids to develop a comprehensive understanding of their direct and indirect roles in modulating the Keap1-Nrf2-ARE signaling system.

Targeted Inhibition of Anti-Inflammatory Regulator Nrf2 Results in Breast Cancer Retardation In Vitro and In Vivo

Nuclear factor erythroid-2 related factor-2 (Nrf2) is an oxidative stress-response transcriptional activator that promotes carcinogenesis through metabolic reprogramming, tumor promoting inflammation, and therapeutic resistance. However, the extension of Nrf2 expression and its involvement in regulation of breast cancer (BC) responses to chemotherapy remain largely unclear. This study determined the expression of Nrf2 in BC tissues (n = 46) and cell lines (MDA-MB-453, MCF-7, MDA-MB-231, MDA-MB-468) with diverse phenotypes. Immunohistochemical (IHC)analysis indicated lower Nrf2 expression in normal breast tissues, compared to BC samples, although the difference was not found to be significant. However, pharmacological inhibition and siRNA-induced downregulation of Nrf2 were marked by decreased activity of NADPH quinone oxidoreductase 1 (NQO1), a direct target of Nrf2. Silenced or inhibited Nrf2 signaling resulted in reduced BC proliferation and migration, cell cycle arrest, activation of apoptosis, and sensitization of BC cells to cisplatin in vitro. Ehrlich Ascites Carcinoma (EAC) cells demonstrated elevated levels of Nrf2 and were further tested in experimental mouse models in vivo. Intraperitoneal administration of pharmacological Nrf2 inhibitor brusatol slowed tumor cell growth. Brusatol increased lymphocyte trafficking towards engrafted tumor tissue in vivo, suggesting activation of anti-cancer effects in tumor microenvironment. Further large-scale BC testing is needed to confirm Nrf2 marker and therapeutic capacities for chemo sensitization in drug resistant and advanced tumors.

The anti-hepatocellular carcinoma effect of Brucea javanica oil in ascitic tumor-bearing mice: The detection of brusatol and its role

Brucea javanica oil (BJO), one of the main products of Brucea javanica, has been widely used in treating different kinds of malignant tumors. Quassinoids are the major category of anticancer phytochemicals of B. javanica. However, current researches on the anti-cancer effect of BJO mainly focused on oleic acid and linoleic acid, the common major components of dietary edible oils, essential and characteristic components of B. javanica like quassinoids potentially involved remained unexplored. In the current investigation, we developed an efficient HPLC method to detect brusatol, a characteristic quassinoid, and comparatively scrutinized the anti-hepatocellular carcinoma (anti-HCC) effect of BJO, brusatol-free BJO (BF-BJO), and brusatol-enriched BJO (BE-BJO) against hepatoma 22 (H22) in mice. High-performance liquid chromatography (HPLC) was utilized to identify the components in BJO. BE-BJO was extracted with 95 % ethanol. The anti-tumor effect of BJO, BF-BJO and BE-BJO was comparatively investigated, and the potential underlying mechanism was explored in H22 ascites tumor-bearing mice. The results indicated that BJO and BE-BJO significantly prolonged the survival time of H22 ascites tumor-bearing mice, while BF-BJO exhibited no obvious effect. BJO and BE-BJO exhibited pronounced anti-HCC activity by suppressing the growth of implanted hepatoma H22 in mice, including ascending weight, abdominal circumference, ascites volume and cancer cell viability, with a relatively wide margin of safety. BJO and BE-BJO significantly induced H22 cell apoptosis by upregulating the miRNA-29b gene level and p53 expression. Furthermore, BJO and BE-BJO treatment substantially downregulated Bcl-2 and mitochondrial Cytochrome C protein expression, and upregulated expression levels of Bax, Bad, cytosol Cytochrome C, caspase-3 (cleaved), caspase‑9 (cleaved), PARP and PARP (cleaved) to induce H22 cells apoptosis. Brusatol was detected in BJO and found to be one of its major active anti-HCC components, rather than fatty acids including oleic acid and linoleic acid. The anti-HCC effect of BJO and BE-BJO was intimately associated with the activation of miRNA-29b, p53-associated apoptosis and mitochondrial-related pathways. Our study gained novel insight into the material basis of BJO in the treatment of HCC, and laid a foundation for a novel specific standard for the quality evaluation of BJO and its commercial products in terms of its anti-cancer application.

Medicinal Activities and Nanomedicine Delivery Strategies for Brucea javanica Oil and Its Molecular Components

Brucea javanica oil (BJO) is widely used in traditional Chinese medicine to treat various types of cancer and inflammatory diseases. There is significant interest in understanding the medicinal activities of BJO and its molecular components, especially quassinoids, and in exploring how they can be incorporated into nanomedicine delivery strategies for improved application prospects. Herein, we cover the latest progress in developing different classes of drug delivery vehicles, including nanoemulsions, liposomes, nanostructured lipid carriers, and spongosomes, to encapsulate BJO and purified quassinoids. An introduction to the composition and medicinal activities of BJO and its molecular components, including quassinoids and fatty acids, is first provided. Application examples involving each type of drug delivery vehicle are then critically presented. Future opportunities for nanomedicine delivery strategies in the field are also discussed and considered within the context of translational medicine needs and drug development processes.