Quercetin promotes degradation of survivin and thereby enhances death-receptor-mediated apoptosis in glioma cells

The entrancing role of dietary polyphenols against the most frequent aging-associated diseases

Aging, a fundamental physiological process influenced by innumerable biological and genetic pathways, is an important driving factor for several aging-associated disorders like diabetes mellitus, osteoporosis, cancer, and neurodegenerative diseases including Alzheimer's and Parkinson's diseases. In the modern era, the several mechanisms associated with aging have been deeply studied. Treatment and therapeutics for age-related diseases have also made considerable advances; however, for the effective and long-lasting treatment, nutritional therapy particularly including dietary polyphenols from the natural origin are endorsed. These dietary polyphenols (e.g., apigenin, baicalin, curcumin, epigallocatechin gallate, kaempferol, quercetin, resveratrol, and theaflavin), and many other phytochemicals target certain molecular, genetic mechanisms. The most common pathways of age-associated diseases are mitogen-activated protein kinase, reactive oxygen species production, nuclear factor kappa light chain enhancer of activated B cells signaling pathways, metal chelation, c-Jun N-terminal kinase, and inflammation. Polyphenols slow down the course of aging and help in combatting age-linked disorders. This exemplified in the form of clinical trials on specific dietary polyphenols in various aging-associated diseases. With this context in mind, this review reveals the new insights to slow down the aging process, and consequently reduce some classic diseases associated with age such as aforementioned, and targeting age-associated diseases by the activities of dietary polyphenols of natural origin.

Nano Drug Delivery Strategies for an Oral Bioenhanced Quercetin Formulation

Quercetin, a naturally occurring flavonoid, has been credited with a wide spectrum of therapeutic properties. However, the oral use of quercetin is limited due to its poor water solubility, low bioavailability, rapid metabolism, and rapid plasma clearance. Quercetin has been studied extensively when used with various nanodelivery systems for enhancing quercetin bioavailability. To enhance its oral bioavailability and efficacy, various quercetin-loaded nanosystems such as nanosuspensions, polymer nanoparticles, metal nanoparticles, emulsions, liposomes or phytosomes, micelles, solid lipid nanoparticles, and other lipid-based nanoparticles have been investigated in in-vitro cells, in-vivo animal models, and humans. Among the aforementioned nanosystems, quercetin phytosomes are attracting more interest and are available on the market. The present review covers insights into the possibilities of harnessing quercetin for several therapeutic applications and a special focus on anticancer applications and the clinical benefits of nanoquercetin formulations.

Modulation of the ubiquitin-proteasome system by phytochemicals: Therapeutic implications in malignancies with an emphasis on brain tumors

Regarding the multimechanistic nature of cancers, current chemo- or radiotherapies often fail to eradicate disease pathology, and frequent relapses or resistance to therapies occur. Brain malignancies, particularly glioblastomas, are difficult-to-treat cancers due to their highly malignant and multidimensional biology. Unfortunately, patients suffering from malignant tumors often experience poor prognoses and short survival periods. Thus far, significant efforts have been conducted to discover novel and more effective modalities. To that end, modulation of the ubiquitin-proteasome system (UPS) has attracted tremendous interest since it affects the homeostasis of proteins critically engaged in various cell functions, for example, cell metabolism, survival, proliferation, and differentiation. With their safe and multimodal actions, phytochemicals are among the promising therapeutic tools capable of turning the operation of various UPS elements. The present review, along with an updated outline of the role of UPS dysregulation in multiple cancers, provided a detailed discussion on the impact of phytochemicals on the UPS function in malignancies, especially brain tumors.

Insight into the transcription factors regulating Ischemic Stroke and Glioma in Response to Shared Stimuli

Cerebral ischemic stroke and glioma are the two leading causes of patient mortality globally. Despite physiological variations, 1 in 10 people who have an ischemic stroke go on to develop brain cancer, most notably gliomas. In addition, glioma treatments have also been shown to increase the risk of ischemic strokes. Stroke occurs more frequently in cancer patients than in the general population, according to traditional literature. Unbelievably, these events share multiple pathways, but the precise mechanism underlying their co-occurrence remains unknown. Transcription factors (TFs), the main components of gene expression programmes, finally determine the fate of cells and homeostasis. Both ischemic stroke and glioma exhibit aberrant expression of a large number of TFs, which are strongly linked to the pathophysiology and progression of both diseases. The precise genomic binding locations of TFs and how TF binding ultimately relates to transcriptional regulation remain elusive despite a strong interest in understanding how TFs regulate gene expression in both stroke and glioma. As a result, the importance of continuing efforts to understand TF-mediated gene regulation is highlighted in this review, along with some of the primary shared events in stroke and glioma.

Matteucinol combined with temozolomide inhibits glioblastoma proliferation, invasion, and progression: an in vitro, in silico, and in vivo study

Glioblastoma is the most prevalent and malignant brain tumor identified in adults. Surgical resection followed by radiotherapy and chemotherapy, mainly with temozolomide (TMZ), is the chosen treatment for this type of tumor. However, the average survival of patients is around 15 months. Novel approaches to glioblastoma treatment are greatly needed. Here, we aimed to investigate the anti-glioblastoma effect of the combination of matteucinol (Mat) (dihydroxyflavanone derived from Miconia chamissois Naudin) with the chemotherapeutic TMZ in vitro using tumor (U-251MG) and normal astrocyte (NHA) cell lines and in vivo using the chick embryo chorioallantoic membrane (CAM) assay. The combination was cytotoxic and selective for tumor cells (28 μg/mL Mat and 9.71 μg/mL TMZ). Additionally, the combination did not alter cell adhesion but caused morphological changes characteristic of apoptosis in vitro. Notably, the combination was also able to reduce tumor growth in the chick embryo model (CAM assay). The docking results showed that Mat was the best ligand to the cell death membrane receptor TNFR1 and to TNFR1/TMZ complex, suggesting that these two molecules may be working together increasing their potential. In conclusion, Mat-TMZ can be a good candidate for pharmacokinetic studies in view of clinical use for the treatment of glioblastoma.

A miR-137-XIAP axis contributes to the sensitivity of TRAIL-induced cell death in glioblastoma

Glioblastoma (GBM) is the most lethal primary brain tumor in the central nervous system with limited therapeutic strategies to prolong the survival rate in clinic. TNF-related apoptosis-inducing ligand (TRAIL)-based strategy has been demonstrated to induce cell death in an extensive spectrum of tumor cells, including GBM, while a considerable proportion of malignant cells are resistant to TRAIL-induced apoptosis. MiR-137 is highly expressed in the brain, but significantly decreases with advanced progression of GBM. However, the functional link between miR-137 and TRAIL-induced apoptosis in GBM cells has not been established. Here, GBM cells were transfected with miR-137, and gene expression levels were examined by qRT-PCR and western blot. Apoptotic cells were measured by Annexin-V staining and TUNEL assay. Our data showed that miR-137 sensitizes GBM cells to the TRAIL-mediated apoptosis. Mechanistically, we identified that XIAP is a bona fide target of miR-137, which is essential for miR-137-regulated sensitivity of TRAIL-induced cell death in GBM cells. Finally, in a xenograft model, combined utilization of miR-137 and TRAIL potently suppresses tumor growth in vivo. Collectively, we demonstrate that a miR-137-XIAP axis is required for the sensitivity of TRAIL-induced cell death and shed a light on the avenue for the treatment of GBM.

An organoid model of colorectal circulating tumor cells with stem cell features, hybrid EMT state and distinctive therapy response profile

Background

Circulating tumor cells (CTCs) are responsible for the metastatic dissemination of colorectal cancer (CRC) to the liver, lungs and lymph nodes. CTCs rarity and heterogeneity strongly limit the elucidation of their biological features, as well as preclinical drug sensitivity studies aimed at metastasis prevention.

Methods

We generated organoids from CTCs isolated from an orthotopic CRC xenograft model. CTCs-derived organoids (CTCDOs) were characterized through proteome profiling, immunohistochemistry, immunofluorescence, flow cytometry, tumor-forming capacity and drug screening assays. The expression of intra- and extracellular markers found in CTCDOs was validated on CTCs isolated from the peripheral blood of CRC patients.

Results

CTCDOs exhibited a hybrid epithelial-mesenchymal transition (EMT) state and an increased expression of stemness-associated markers including the two homeobox transcription factors Goosecoid and Pancreatic Duodenal Homeobox Gene-1 (PDX1), which were also detected in CTCs from CRC patients. Functionally, CTCDOs showed a higher migratory/invasive ability and a different response to pathway-targeted drugs as compared to xenograft-derived organoids (XDOs). Specifically, CTCDOs were more sensitive than XDOs to drugs affecting the Survivin pathway, which decreased the levels of Survivin and X-Linked Inhibitor of Apoptosis Protein (XIAP) inducing CTCDOs death.

Conclusions

These results indicate that CTCDOs recapitulate several features of colorectal CTCs and may be used to investigate the features of metastatic CRC cells, to identify new prognostic biomarkers and to devise new potential strategies for metastasis prevention.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02263-y.

Quercetin and Glioma: Which signaling pathways are involved?

Abstract:

Gliomas are the most common brain tumors. These tumors commonly exhibit continuous growth without invading surrounding brain tissues. Dominant remedial approaches suffer limited therapy and survival rates. Although some progress has been made in conventional glioma treatments, these breakthroughs have not yet proven sufficient for treating this malignancy. The remedial options are limited given gliomas' aggressive metastasis and drug resistance. Quercetin, a flavonoid, is an anti-oxidative, anti-allergic, antiviral, anti-inflammatory, and anticancer compound. Multiple lines of evidence have shown that Quercetin has anti-tumor effects, documenting this natural compound exerts its pharmacological effects by targeting a variety of cellular and molecular processes, i.e., apoptosis, metastasis, and autophagy. Herein, we summarize various cellular and molecular pathways that are affected by Quercetin in gliomas.

A Preliminary Study of the Effect of Quercetin on Cytotoxicity, Apoptosis, and Stress Responses in Glioblastoma Cell Lines

A growing body of evidence indicates that dietary polyphenols show protective effects against various cancers. However, little is known yet about their activity in brain tumors. Here we investigated the interaction of dietary flavonoid quercetin (QCT) with the human glioblastoma A172 and LBC3 cell lines. We demonstrated that QCT evoked cytotoxic effect in both tested cell lines. Microscopic observations, Annexin V-FITC/PI staining, and elevated expression and activity of caspase 3/7 showed that QCT caused predominantly apoptotic death of A172 cells. Further analyses confirmed enhanced ROS generation, deregulated expression of SOD1 and SOD2, depletion of ATP levels, and an overexpression of CHOP, suggesting the activation of oxidative stress and ER stress upon QCT exposure. Finally, elevated expression and activity of caspase 9, indicative of a mitochondrial pathway of apoptosis, was detected. Conversely, in LBC3 cells the pro-apoptotic effect was observed only after 24 h incubation with QCT, and a shift towards necrotic cell death was observed after 48 h of treatment. Altogether, our data indicate that exposure to QCT evoked cell death via activation of intrinsic pathway of apoptosis in A172 cells. These findings suggest that QCT is worth further investigation as a potential pharmacological agent in therapy of brain tumors.

Quercetin-biapigenin nanoparticles are effective to penetrate the blood-brain barrier

Search for efficient therapeutic agents for central nervous system (CNS) disorders has been extensive. Nevertheless, blood-brain barrier (BBB) is an obstacle that prevents the majority of compounds to act in these diseases. It is, thus, of extreme relevance the BBB overcome, in order to deliver a drugs therapeutically active concentration to the action site, with the least losses and interaction with other organs, tissues, or cells. The present study aimed to investigate the potential protective effect of quercetin-biapigenin encapsulated into poly(Ɛ-polycaprolactone) (PCL) nanoparticles against t-BOOH-induced oxidative stress in several brain cell lines, as well as evaluate the permeability of those active molecules through an in vitro BBB model. The three cell lines under study (BV-2, hcmec/D3, and U87) presented different reactions to t-BOOH. In general, quercetin-biapigenin PCL-loaded nanoparticles were able to minimize compound toxicity they convey, regardless the cell line. Quercetin-biapigenin PCL-loaded nanoparticles (Papp of approximately 80 × 10-6 cm/s) revealed to be more permeable than free compounds (Papp of approximately 50 × 10-6 cm/s). As of our knowledge, this is the first report of quercetin-biapigenin PCL-loaded nanoparticle activity in brain cells. It is also the first determining its permeability through BBB, as an effective nanocarrier for brain delivery.

Quercetin against MCF7 and CAL51 breast cancer cell lines: apoptosis, gene expression and cytotoxicity of nano-quercetin

Aims: To evaluate the anti breast-cancer activity, biocompatibility and toxicity of poly(d,l)-lactic-co-glycolic acid (PLGA)-encapsulated quercetin nanoparticles (Q-PLGA-NPs). Materials & methods: Quercetin was nano-encapsulated by an emulsion-diffusion process, and the nanoparticles were fully characterized through Fourier transform infrared spectroscopy, x-ray diffractions, FESEM and zeta-sizer analysis. Activity against CAL51 and MCF7 cell lines were assessed by DNA fragmentation assays, fluorescence microscopy, and acridine-orange, and propidium-iodide double-stainings. Biocompatibility towards red blood cells and toxicity towards mice were also explored. Results: The Q-PLGA-NPs exhibited apoptotic activity against the cell lines. The murine in vivo studies showed no significant alterations in the liver and kidney's functional biomarkers, and no apparent abnormalities, or tissue damages were observed in the histological images of the liver, spleen, lungs, heart and kidneys. Conclusion: The study established the preliminary in vitro efficacy and in vivo safety of Q-PLGA-NPs as a potential anti-breast cancer formulation.

The Promoting Effect of Traumatic Brain Injury on the Incidence and Progression of Glioma: A Review of Clinical and Experimental Research

The role of traumatic brain injury in the development of glioma is highly controversial since first presented. This is not unexpected because traumatic brain injuries are overwhelmingly more common than glioma. However, the causes of post-traumatic glioma have been long discussed and still warrant further research. In this review, we have presented an overview of previous cohort studies and case–control studies. We have summarized the roles of microglial cells, macrophages, astrocytes, and stem cells in post-traumatic glioma formation and development, and reviewed various carcinogenic factors involved during traumatic brain injury, especially those reported in experimental studies indicating a relationship with glioma progression. Besides, traumatic brain injury and glioma share several common pathways, including inflammation and oxidative stress; however, the exact mechanism underlying this co-occurrence is yet to be discovered. In this review, we have summarized current epidemiological studies, clinical reports, pathophysiological research, as well as investigations evaluating the probable causes of co-occurrence and treatment possibilities. More efforts should be directed toward elucidating the relationship between traumatic brain injury and glioma, which could likely lead to promising pharmacological interventions towards designing therapeutic strategies.

Current Perspective on the Natural Compounds and Drug Delivery Techniques in Glioblastoma Multiforme

Simple Summary

Glioblastoma multiforme (GBM) is one of the belligerent neoplasia that metastasize to other brain regions and invade nearby healthy tissues. However, the treatments available are associated with some limitations, such as high variations in solid tumors and deregulation of multiple cellular pathways. The heterogeneity of the GBM tumor and its aggressive infiltration into the nearby tissues makes it difficult to treat. Hence, the development of multimodality therapy that can be more effective, novel, with fewer side effects, improving the prognosis for GBM is highly desired. This review evaluated the use of natural phytoconstituents as an alternative for the development of a new therapeutic strategy. The key aspects of GBM and the potential of drug delivery techniques were also assessed, for tumor site delivery with limited side-effects. These efforts will help to provide better therapeutic options to combat GBM in future.

Abstract

Glioblastoma multiforme (GBM) is one of the debilitating brain tumors, being associated with extremely poor prognosis and short median patient survival. GBM is associated with complex pathogenesis with alterations in various cellular signaling events, that participate in cell proliferation and survival. The impairment in cellular redox pathways leads to tumorigenesis. The current standard pharmacological regimen available for glioblastomas, such as radiotherapy and surgical resection following treatment with chemotherapeutic drug temozolomide, remains fatal, due to drug resistance, metastasis and tumor recurrence. Thus, the demand for an effective therapeutic strategy for GBM remains elusive. Hopefully, novel products from natural compounds are suggested as possible solutions. They protect glial cells by reducing oxidative stress and neuroinflammation, inhibiting proliferation, inducing apoptosis, inhibiting pro-oncogene events and intensifying the potent anti-tumor therapies. Targeting aberrant cellular pathways in the amelioration of GBM could promote the development of new therapeutic options that improve patient quality of life and extend survival. Consequently, our review emphasizes several natural compounds in GBM treatment. We also assessed the potential of drug delivery techniques such as nanoparticles, Gliadel wafers and drug delivery using cellular carriers which could lead to a novel path for the obliteration of GBM.

Potential Therapeutic Targets of Quercetin, a Plant Flavonol, and Its Role in the Therapy of Various Types of Cancer through the Modulation of Various Cell Signaling Pathways

Polyphenolic flavonoids are considered natural, non-toxic chemopreventers, which are most commonly derived from plants, fruits, and vegetables. Most of these polyphenolics exhibit remarkable antioxidant, anti-inflammatory, and anticancer properties. Quercetin (Qu) is a chief representative of these polyphenolic compounds, which exhibits excellent antioxidant and anticancer potential, and has attracted the attention of researchers working in the area of cancer biology. Qu can regulate numerous tumor-related activities, such as oxidative stress, angiogenesis, cell cycle, tumor necrosis factor, proliferation, apoptosis, and metastasis. The anticancer properties of Qu mainly occur through the modulation of vascular endothelial growth factor (VEGF), apoptosis, phosphatidyl inositol-3-kinase (P13K)/Akt (proteinase-kinase B)/mTOR (mammalian target of rapamycin), MAPK (mitogen activated protein kinase)/ERK1/2 (extracellular signal-regulated kinase 1/2), and Wnt/β-catenin signaling pathways. The anticancer potential of Qu is documented in numerous in vivo and in vitro studies, involving several animal models and cell lines. Remarkably, this phytochemical possesses toxic activities against cancerous cells only, with limited toxic effects on normal cells. In this review, we present extensive research investigations aimed to discuss the therapeutic potential of Qu in the management of different types of cancers. The anticancer potential of Qu is specifically discussed by focusing its ability to target specific molecular signaling, such as p53, epidermal growth factor receptor (EGFR), VEGF, signal transducer and activator of transcription (STAT), PI3K/Akt, and nuclear factor kappa B (NF-κB) pathways. The anticancer potential of Qu has gained remarkable interest, but the exact mechanism of its action remains unclear. However, this natural compound has great pharmacological potential; it is now believed to be a complementary—or alternative—medicine for the prevention and treatment of different cancers.

Compounds with Antiviral, Anti-Inflammatory and Anticancer Activity Identified in Wine from Hungary's Tokaj Region via High Resolution Mass Spectrometry and Bioinformatics Analyses

(1) Background: Wine contains a variety of molecules with potential beneficial effects on human health. Our aim was to examine the wine components with high-resolution mass spectrometry including high-resolution tandem mass spectrometry in two wine types made from grapes with or without the fungus Botrytis cinerea, or "noble rot". (2) For LC-MS/MS analysis, 12 wine samples (7 without and 5 with noble rotting) from 4 different wineries were used and wine components were identified and quantified. (3) Results: 288 molecules were identified in the wines and the amount of 169 molecules was statistically significantly different between the two wine types. A database search was carried out to find the molecules, which were examined in functional studies so far, with high emphasis on molecules with antiviral, anti-inflammatory and anticancer activities. (4) Conclusions: A comprehensive functional dataset related to identified wine components is also provided highlighting the importance of components with potential health benefits.

Quercetin as an innovative therapeutic tool for cancer chemoprevention: Molecular mechanisms and implications in human health

Cancer is a life-threatening disease afflicting human health worldwide. Recent advances in drug discovery infrastructure and molecular approaches have helped a lot in identifying the novel drug targets for therapeutic intervention. Nevertheless, the morbidity and mortality rates because of this disease keep on rising at an alarming rate. Recently, the use of natural and synthetic molecules as innovative therapeutic tools for cancer prevention has lead to the development of cancer chemoprevention. Cancer chemoprevention is a prophylactic strategy that involves the chronic administration of one or more natural or synthetic agents to block, to inhibit, or to suppress the process of cancer development before it becomes an invasive disease. Quercetin, a dietary bioflavonoid, can specifically retard the growth of cancer cells and behaves as a potent cancer chemopreventive agent. Quercetin has multiple intracellular targets in a cancer cell. Therefore, many mechanisms have been postulated to explain its chemopreventive action. The chemopreventive effects elicited by this natural molecule in different model systems are believed to include antioxidant/pro-oxidant action, regulation of redox homeostasis, apoptosis, cell cycle arrest, anti-inflammatory action, modulation of drug metabolizing enzymes, alterations in gene expression patterns, inhibition of Ras gene expression, and modulation of signal transduction pathways. However, cell signaling networks have recently garnered attention as common molecular target for various chemopreventive effects of quercetin. In this review, we made an attempt to critically summarize the emerging knowledge on the role of quercetin in cancer chemoprevention and the underlying molecular mechanisms implicated in its chemopreventive and therapeutic effects.

Metabolomics and Pharmacological Screening of Aspergillus versicolor Isolated from Hyrtios erectus Red Sea Sponge; Egypt

Background:

Aspergillus Versicolor is a marine-derived fungus isolated from Hyrtios Erectus Red Sea sponge.

Methods:

The aim of this study was to carry out a pharmacological screening and investigation for the in vitro biological activity (antioxidant, cholinergic, antidiabetic and anticancer) of Aspergillus Versicolor crude extract’s active compounds by using different qualitative and quantitative methods.

Results:

The present study results showed that Aspergillus Versicolor crude extracts contain 0.6 mg total phenolic/mg crude extract. Aspergillus Versicolor also showed a potent antioxidative capacity by decreasing the oxidation of ABTS. The anticancer and inhibitory effects of Aspergillus Versicolor crude extracts on PTK and SHKI were found to be 75.29 % and 80.76%; respectively. The AChE inhibitory assay revealed that Aspergillus Versicolor extracts had an inhibitory percentage of 86.67%. Furthermore, the anti-inflammatory activity using COX1, COX2, TNF, and IL6 was 77.32, 85.21 %, 59.83%, and 56.15%; respectively. Additionally, the anti-viral effect using reverse transcriptase enzyme showed high antiviral activity with 92.10 %.

Conclusion:

The current study confirmed that the Aspergillus versicolor crude extract and its active constituents showed strong effects on diminishing the oxidative stress, neurodegenerative damage, antiinflammatory, anti-cancer and anti-viral, suggesting their beneficial role as a promising fermented product in the treatment of cancer, oxidative stress, Alzheimer's, anti-inflammatory and anti-viral diseases.

Anti-neoplastic Potential of Flavonoids and Polysaccharide Phytochemicals in Glioblastoma

Clinically, gliomas are classified into four grades, with grade IV glioblastoma multiforme being the most malignant and deadly, which accounts for 50% of all gliomas. Characteristically, glioblastoma involves the aggressive proliferation of cells and invasion of normal brain tissue, outcomes as poor patient prognosis. With the current standard therapy of glioblastoma; surgical resection and radiotherapy followed by adjuvant chemotherapy with temozolomide, it remains fatal, because of the development of drug resistance, tumor recurrence, and metastasis. Therefore, the need for the effective therapeutic option for glioblastoma remains elusive. Previous studies have demonstrated the chemopreventive role of naturally occurring pharmacological agents through preventing or reversing the initiation phase of carcinogenesis or arresting the cancer progression phase. In this review, we discuss the role of natural phytochemicals in the amelioration of glioblastoma, with the aim to improve therapeutic outcomes, and minimize the adverse side effects to improve patient's prognosis and enhancing their quality of life.

DRAQ7 as an Alternative to MTT Assay for Measuring Viability of Glioma Cells Treated With Polyphenols

BACKGROUND/AIM

The tetrazolium-based MTT cytotoxicity assay is well established for screening putative anti-cancer agents. However, it has limitations including lack of reproducibility with glioma cells treated with polyphenols. The aim of this study was to evaluate whether a flow cytometric assay with the anthraquinone, DRAQ7, was a better alternative than the colorimetric MTT assay for measuring cell viability.

MATERIALS AND METHODS

Two glioma cell lines (IPSB-18, U373) and 1 pancreatic cancer cell line (AsPC-1) were treated with 4 polyphenols, namely red grape seed extract, red clover extract, anthocyanin-rich extract and curcumin. Cell viability was assessed using MTT assay and DRAQ7 staining.

RESULTS

Limitations of MTT assay included lack of sensitivity and interference with the structure and absorbance spectra of polyphenols. Also, DMSO was toxic to glioma cells. Microscopic observations of cells treated with polyphenols confirmed the range of IC₅₀ values evaluated by DRAQ7, but not by the MTT assay.

CONCLUSION

DRAQ7 is a better alternative than MTT for measuring viability of glioma cells treated with brightly coloured polyphenols.

Hispidulin: A novel natural compound with therapeutic potential against human cancers

Cancer is one of the most devastating disease and leading cause of death worldwide. The conventional anticancer drugs are monotarget, toxic, expensive and suffer from drug resistance. Development of multi-targeted drugs from natural products has emerged as a new paradigm to overcome aforementioned conventionally encountered obstacles. Hispidulin (HIS), is a biologically active natural flavone with versatile biological and pharmacological activities. The anticancer, antimutagenic, antioxidative and anti-inflammatory properties of HIS have been reported. The aim of this review is to summarize the findings of several studies over the last few decades on the anticancer activity of HIS published in various databases including PubMed, Google Scholar, and Scopus. HIS has been shown to reduce the growth of cancer cells by inducing apoptosis, arresting cell cycle, inhibiting angiogenesis, invasion and metastasis via modulating multiple signaling pathways implicated in cancer initiation and progression. Multitargeted anticancer activity of HIS remains the strongest point for developing it into potential anticancer drug. We also highlighted the natural sources, anticancer mechanism, cellular targets, and chemo-sensitizing potential of HIS. This review will provide bases for design and conduct of further pre-clinical and clinical trials to develop HIS into a lead structure for future anticancer therapy.

NCBP3/SNHG6 inhibits GBX2 transcription in a histone modification manner to facilitate the malignant biological behaviour of glioma cells

RNA-binding proteins (RBPs) are significantly dysregulated in glioma. In this study, we demonstrated the upregulation of Nuclear cap-binding subunit 3 (NCBP3) in glioma tissues and cells. Further, knockdown of NCBP3 inhibited the malignant progression of glioma. NCBP3 directly bound to small nucleolar RNA host gene 6 (SNHG6) and stabilized SNHG6 expression. In contrast, the gastrulation brain homeobox 2 (GBX2) transcription factor was downregulated in glioma tissues and cells. SNHG6 inhibited GBX2 transcription by mediating the H3K27me3 modification induced by polycomb repressive complex 2 (PRC2). Moreover, GBX2 decreased the promoter activities and downregulated the expression of the flotillin protein family 1 (FLOT1) oncogene. In conclusion, NCBP3/SNHG6 inhibits GBX2 transcription in a PRC2-dependent manner to facilitate the malignant progression of gliomas.

Quercetin: A promising phytochemical for the treatment of glioblastoma multiforme

Quercetin, a plant-derived flavonoid, is known for its antitumor and antiproliferative activities. Glioblastoma multiforme (GBM), as a highly aggressive cerebrum tumor, has a poor prognosis that is approximately 12 months despite standard therapy. Therefore, because of the low effectiveness of the current therapeutic strategies, additional medications in combination with chemotherapy and radiotherapy are needed, which could improve the prognosis of GBM patients. Multiple lines of evidence have shown that quercetin regulates many proteins involved in the cellular signal transduction in GBM. In this review, recent findings on the targeting of particular signaling pathways by quercetin and the subsequent effect on the pathogenesis of GBM are presented and discussed.

Pharmacological basis and new insights of quercetin action in respect to its anti-cancer effects

Quercetin is a kind of flavonoid compounds that comes from nature and is widely existed in the daily diet. Previous studies have found that quercetin has many effects such as anti-inflammatory, anti-oxidation and anti-cancer. Both in vivo and in vitro experiments have demonstrated that quercetin can exert anti-tumor effects by altering cell cycle progression, inhibiting cell proliferation, promoting apoptosis, inhibiting angiogenesis and metastasis progression, and affecting autophagy. This review summarizes the evidence for the pharmacological potential and inhibition of quercetin on cancers, supporting the viewpoint that quercetin should be adequately considered as a therapeutic agent against various cancers.

The interrelationship between cerebral ischemic stroke and glioma: a comprehensive study of recent reports

Glioma and cerebral ischemic stroke are two major events that lead to patient death worldwide. Although these conditions have different physiological incidences, ~10% of ischemic stroke patients develop cerebral cancer, especially glioma, in the postischemic stages. Additionally, the high proliferation, venous thrombosis and hypercoagulability of the glioma mass increase the significant risk of thromboembolism, including ischemic stroke. Surprisingly, these events share several common pathways, viz. hypoxia, cerebral inflammation, angiogenesis, etc., but the proper mechanism behind this co-occurrence has yet to be discovered. The hypercoagulability and presence of the D-dimer level in stroke are different in cancer patients than in the noncancerous population. Other factors such as atherosclerosis and coagulopathy involved in the pathogenesis of stroke are partially responsible for cancer, and the reverse is also partially true. Based on clinical and neurosurgical experience, the neuronal structures and functions in the brain and spine are observed to change after a progressive attack of ischemia that leads to hypoxia and atrophy. The major population of cancer cells cannot survive in an adverse ischemic environment that excludes cancer stem cells (CSCs). Cancer cells in stroke patients have already metastasized, but early-stage cancer patients also suffer stroke for multiple reasons. Therefore, stroke is an early manifestation of cancer. Stroke and cancer share many factors that result in an increased risk of stroke in cancer patients, and vice-versa. The intricate mechanisms for stroke with and without cancer are different. This review summarizes the current clinical reports, pathophysiology, probable causes of co-occurrence, prognoses, and treatment possibilities.

Quercetin Enhances the Anti-Tumor Effects of BET Inhibitors by Suppressing hnRNPA1

Bromodomain and extraterminal domain (BET) proteins, which are important epigenetic readers, are often dysregulated in cancer. While a number of BET inhibitors are currently in early phase clinical trials, BET inhibitors show limited single-agent activity. The purpose of this study is to determine if Quercetin, a naturally occurring polyphenolic flavonoid often found abundant in fruits and vegetables, can enhance the anti-tumor effects of BET inhibitors. The efficacy of the combination was evaluated in vitro and in a xenograft model of pancreatic cancer. Co-treatment with BET inhibitors and Quercetin promoted apoptosis, decreased sphere-forming ability by cancer cells, and decreased cell proliferation. We found that hnRNPA1, a nuclear protein known to control mRNA export and mRNA translation of anti-apoptotic proteins, mediates some anti-tumor effects by Quercetin. Additionally, we show that combining BET inhibitors with Quercetin or hnRNPA1 knockdown decreased the anti-apoptotic protein Survivin. Significantly, Quercetin decreased hnRNPA1 in vivo and enhanced the effects of BET inhibitors at suppressing tumor growth. Together, these results demonstrate that Quercetin enhances the efficacy of BET inhibitors by suppressing hnRNPA1, and identify combination therapy with Quercetin and BET inhibitors for the treatment of cancer patients.

Quercetin: a natural compound for ovarian cancer treatment

Ovarian cancer is the main cause of death among all reproductive cancers in females. In 2018, ovarian cancer was the seventh most common cancer of women entire the world. A wide variety of molecular and genetic alterations as well as different response to therapies in the different types of ovarian cancer lead to problems in design a common therapeutic strategy. Besides, ovarian cancer cells have tendency to acquire resistance to common cancer treatments through multiple mechanisms. Various factors, including cytokines, growth factors, proteases, adhesion molecules, coagulation factors, hormones and apoptotic agents have been examined to find effective cancer treatment. Phytochemicals have been indicated to have great potential anti-cancer properties against various types of cancers. Quercetin is one of the phytochemicals that exists extensively in daily foods. Wide evidences revealed that quercetin is able to inhibit various types of cancers including breast, lung, nasopharyngeal, kidney, colorectal, prostate, pancreatic, and ovarian cancer. Several in vitro and in vivo studied conducted to evaluate cytotoxic effects of quercetin on ovarian cancer. Since quercetin does not harm healthy cells and it is cytotoxic to cancer cells via various mechanisms, researchers suggest that it could be an ideal agent for ovarian cancer treatment or an adjuvant agent in combination with other anti-cancer drugs. Thus, in this review, we focused on chemo-preventive and curative attitude of quercetin for ovarian cancer and summarize some of the most recent findings which regard the possible molecular mechanisms by which this natural compound inhibits this cancer.

Quercetin sensitizes human myeloid leukemia KG-1 cells against TRAIL-induced apoptosis

INTRODUCTION

Acute myeloid leukemia (AML) is the most common acute leukemia in adults. Conventional treatments are associated with cytotoxicity and systemic side effects. Hence, efforts in the field of cancer treatment are focused on finding the strategies which can specifically target the tumor cells without affecting the normal cells. TNF-related apoptosis-inducing ligand (TRAIL) is a biological cytokine which has the mentioned specificity, but the resistance of some cancer cells limits its use as a therapeutic strategy. Recent studies have shown that quercetin (QUR) can be used as a sensitizing agent alongside with TRAIL. The present study showed that QUR can increase the effect of TRAIL-induced cytotoxicity in KG-1 cells.

MATERIALS AND METHODS

In this descriptive study, the IC50 dose for QUR in the KG-1 cell line was first determined by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay. Then, the cells were treated with TRAIL and QUR for 12, 24, and 48 hr. The rate of apoptosis was measured by Annexin V/propidium iodide assay. Also, the molecular evaluation of candidate genes was accomplished before and after the treatment.

RESULTS

The results indicated that QUR could sensitize the KG-1 cells against the TRAIL-induced apoptosis. This outcome is achieved by increasing the messenger RNA expression levels of the death receptor genes and reducing the expression of antiapoptotic proteins, as well as decreasing the expression of the NF-κB subunit.

CONCLUSION

Our findings suggest that QUR can sensitize the acute myeloid KG-1 cells against TRAIL. Moreover, the combinational therapy of these agents might promisingly improve the clinical efficacy of TRAIL in patients with AML.

Sensitization of recombinant human tumor necrosis factor-related apoptosis-inducing ligand-resistant malignant melanomas by quercetin

Malignant melanoma is the most commonly diagnosed skin cancer associated with a high rate of metastasis. Low-stage melanoma is easily treated, but metastatic malignant melanoma is an extremely treatment-resistant malignancy with low survival rates. The application of recombinant human tumor necrosis factor-related apoptosis-inducing ligand (rhTRAIL) for the treatment of metastatic malignant melanoma holds considerable promise because of its selective proapoptotic activity towards cancer cells and not nontransformed cells. Unfortunately, the clinical utilization of rhTRAIL has been terminated due to the resistance of many cancer cells to undergo apoptosis in response to rhTRAIL. However, rhTRAIL-resistance can be abrogated through the cotreatment with compounds derived from 'Mother Nature' such as quercetin that can modulate cellular components responsible for rhTRAIL-resistance. Here, we show that rhTRAIL-resistant malignant melanomas are sensitized by quercetin. Quercetin action is manifested by the upregulation of rhTRAIL-binding receptors DR4 and DR5 on the surface of cancer cells and by increased rate of the proteasome-mediated degradation of the antiapoptotic protein FLIP. Our data provide for a new efficient and nontoxic treatment of malignant melanoma.

The effect of quercetin on the electrical properties of model lipid membranes and human glioblastoma cells

Quercetin is a naturally-occurring flavonoid claimed to exert many beneficial health effects. In this report, the influence of quercetin on the surface charge of phosphatidylcholine liposomes and human glioblastoma LN-229 and LN-18 cells was studied using microelectrophoretic mobility measurements. The effect of quercetin on the electrical resistance and capacitance of bilayer lipid membranes was analyzed via electrochemical impedance spectroscopy. The results showed that after flavonoid treatment, the cell lines demonstrated changes in surface charge only in alkaline pH solutions, whereas there were no significant alterations in quercetin-treated vs. control cells in acidic pH solutions. The same tendency was found for liposomal membranes proving that quercetin insertion into membranes is strongly pH-dependent. Capacitance and resistance measurements conducted in acidic electrolyte solutions demonstrated an increase in both electrical parameters, indicating an increased amount of quercetin inserted into the bilayers. Moreover, the cytotoxic effect of quercetin confirms that the flavonoid enters the cells and perturbs the proliferation of LN-229 and LN-18 glioblastoma cell lines. As such, our results indicate that the specific localization of quercetin, membrane-bound or cell-entering, might be crucial for its pharmacological activity. However, further studies are necessary prior to applying these physicochemical measurements as standard methods of evaluating drug activity.

Quercetin: A functional dietary flavonoid with potential chemo-preventive properties in colorectal cancer

Recently, an intense attention has been paid to the application of natural compounds as a novel therapeutic strategy for cancer treatment. Quercetin, a natural flavonol present in many commonly consumed food items, is widely demonstrated to exert inhibitory effects on cancer progression through various mechanisms. Since there is a strong association with diets containing abundant vegetables, fruits, and grains, and significant decline in the risk of colon cancer, accumulation studies have focused on the anticancer potential of quercetin in colorectal cancer. Cell cycle arrest, increase in apoptosis, antioxidant replication, modulation of estrogen receptors, regulation of signaling pathways, inhibition of and metastasis and angiogenesis are among various mechanisms underlying the chemo-preventive effects of quercetin in colorectal cancer. This review covers various therapeutic interactions of Quercetin as to how targets cellular involved in cancer treatment.

Activation of CECR1 in M2-like TAMs promotes paracrine stimulation-mediated glial tumor progression

Background

The majority of glioma-associated microglia/macrophages have been identified as M2-type macrophages with immune suppressive and tumor supportive action. Recently, the extracellular adenosine deaminase protein Cat Eye Syndrome Critical Region Protein 1 (CECR1) was shown to regulate macrophage maturation. In this study, we investigate the role of CECR1 in the regulation of the glioma-associated macrophage response.

Methods

Expression of CECR1 was assessed in human glioma samples. CECR1-mediated macrophage response was studied in vitro, using donor derived CD14+ monocytes and the THP-1 monocytic cell line. The response of the human glioma cell line U87 to conditioned medium of macrophages preconditioned with recombinant human CECR1 or CECR1 silencing was also assessed.

Results

CECR1 was strongly expressed in high-grade gliomas (P < .001) and correlated positively with the M2 phenotype markers in tumor-associated microglia/macrophages (TAMs) (overall, P < .05). In vitro studies confirmed the presence of a significantly higher level of CECR1 expression in M2-like macrophages exposed to U87 conditioned medium (P < .001). CECR1 knockdown or stimulation of macrophages affected differentiation toward the M2-like phenotype. Stimulation of U87 cells with conditioned medium of CECR1 knockdown or stimulated macrophages affected tumor cell proliferation and migration, coinciding with altered intracellular signaling of mitogen-activated protein kinase (MAPK). In glioma tissue samples, CECR1 expression correlated with Ki67 and MAPK signaling protein.

Conclusions

CECR1 is a potent regulator of TAM polarization and is consistently highly expressed by M2-type TAMs, particularly in high-grade glioma. Paracrine effects induced by CECR1 in M2-like TAMs activate MAPK signaling and stimulate the proliferation and migration of glioma cells.

Inhibition of never in mitosis A (NIMA)-related kinase-4 reduces survivin expression and sensitizes cancer cells to TRAIL-induced cell death

The tumor necrosis factor-related apoptosis inducing ligand (TRAIL) preferentially induces apoptosis in cancer cells. However, many tumors are resistant to TRAIL-induced apoptosis, and resistance mechanisms are not fully understood. To identify novel regulatory molecules of TRAIL resistance, we screened a siRNA library targeting the human kinome, and NEK4 (NIMA-related kinase-4) was identified. Knockdown of NEK4 sensitized TRAIL-resistant cancer cells and in vivo xenografts to cell death. In contrast, over expression of NEK4 suppressed TRAIL-induced cell death in TRAIL-sensitive cancer cells. In addition, loss of NEK4 resulted in decrease of the anti-apoptotic protein survivin, but an increase in apoptotic cell death. Interestingly, NEK4 was highly upregulated in tumor tissues derived from patients with lung cancer and colon cancer. These results suggest that inhibition of NEK4 sensitizes cancer cells to TRAIL-induced apoptosis by regulation of survivin expression.

Inhibition of deubiquitinases primes glioblastoma cells to apoptosis in vitro and in vivo

It remains a challenge in oncology to identify novel drug regimens to efficiently tackle glioblastoma, the most common primary brain tumor in adults. Here, we target deubiquitinases for glioblastoma therapy by utilizing the small-molecule inhibitor WP1130 which has been characterized as a deubiquitinase inhibitor that interferes with the function of Usp9X. Expression analysis data confirm that Usp9X expression is increased in glioblastoma compared to normal brain tissue indicating its potential as a therapeutic. Consistently, increasing concentrations of WP1130 decrease the cellular viability of established, patient-derived xenograft (PDX) and stem cell-like glioblastoma cells. Specific down-regulation of Usp9X reduces viability in glioblastoma cells mimicking the effects of WP1130. Mechanistically, WP1130 elicits apoptosis and increases activation of caspases. Moreover, WP1130 and siRNAs targeting Usp9X reduce the expression of anti-apoptotic Bcl-2 family members and Inhibitor of Apoptosis Proteins, XIAP and Survivin. Pharmacological and genetic interference with Usp9X efficiently sensitized glioblastoma cells to intrinsic and extrinsic apoptotic stimuli. In addition, single treatment with WP1130 elicited anti-glioma activity in an orthotopic proneural murine model of glioblastoma. Finally, the combination treatment of WP1130 and ABT263 inhibited tumor growth more efficiently than each reagent by its own in vivo without detectable side effects or organ toxicity. Taken together, these results suggest that targeting deubiquitinases for glioma therapy is feasible and effective.

Quercetin Remodels the Tumor Microenvironment To Improve the Permeation, Retention, and Antitumor Effects of Nanoparticles

Our previous work demonstrated that Wnt16 expression in cisplatin-damaged tumor-associated fibroblasts is a key factor contributing to cisplatin resistance in malignancies. Natural antifibrotic compounds with low toxicities are promising candidates to downregulate Wnt16 expression, improving the antitumor effect of cisplatin nanoparticles. Upon screening several natural chemicals, we found that a dietary flavonoid, quercetin, significantly suppresses Wnt16 expression in activated fibroblasts. To facilitate drug delivery, we have prepared a targeted lipid/calcium/phosphate nanoparticle formulation consisting of a prodrug of quercetin, i.e., quercetin phosphate, with a high loading efficiency (26.6% w/w). This quercetin nanoparticle with a particle size of around 35 nm significantly improved the bioavailability and metabolic stability of the parent quercetin. Quercetin phosphate is released from the nanoparticles and converted back to the parent quercetin under physiological conditions. Following systemic administration of quercetin phosphate nanoparticles, a significant downregulation in Wnt16 expression was observed and further yielded a synergistic antitumor effect with cisplatin nanoparticles in a stroma-rich bladder carcinoma model. The α-SMA-positive fibroblast and collagen within the tumor decreased significantly after combination treatment. This suggests that the remodeling of the tumor microenvironment induced by quercetin plays a critical role in promoting the synergy. Indeed, our data further confirmed that quercetin phosphate alone significantly remodeled the tumor microenvironment and increased the penetration of second-wave nanoparticles into the tumor nests. Collectively, quercetin phosphate nanoparticles may be a safe and effective way to improve therapeutic treatment for desmoplastic tumors.

Enhancing Tumor Cell Response to Multidrug Resistance with pH-Sensitive Quercetin and Doxorubicin Conjugated Multifunctional Nanoparticles

Classical chemotherapy uses chemotherapeutic agents as a mainstay of anticancer treatment. However, the development of multidrug resistance to chemotherapy limits the effectiveness of current cancer treatment. Nanosized bioconjugates combining a chemotherapeutic agent with a pharmacological approach may improve the curative effect of chemotherapeutic agents. Herein I addressed this issue by describing the synthesis, and testing of, pH-responsive Fe3O4@SiO2(FITC)-BTN/QUR/DOX multifunctional nanoparticles. The particles were designed to modulate resistance-mediating factors and to potentiate the efficacy of DOX against chemoresistance. The physicochemical properties of the nanoparticles were characterized based on the combination of several techniques: dynamic light scattering (DLS), zeta-potential measurement, Fourier transform infrared spectroscopy (FTIR), electron microscopy techniques (SEM and STEM with EDX) and an in vitro pH-dependent release study. Cellular uptake and cytotoxicity experiments demonstrated enhanced intracellular delivery and retention of nanoparticles in the cytoplasm and efficient reduction of cancer cell viability in drug-resistant lung carcinoma A549/DOX cell lines. This did not affect internalization and viability of an immortalized human lung epithelial cell line BEAS-2B. Moreover, proapoptotic and antiproliferative studies showed that Fe3O4@SiO2(FITC)-BTN/QUR/DOX nanoparticles can promote apoptosis, inhibit tumor cell proliferation, and enhance the chemotherapeutic effects of DOX against multidrug resistance. These results confirm that this multifunctional platform possesses significant synergy between QUR and DOX and is promising for development as an antitumor treatment in cancer therapy.

Blocking COX-2 induces apoptosis and inhibits cell proliferation via the Akt/survivin- and Akt/ID3 pathway in low-grade-glioma

Approximately half of surgically-treated patients with low-grade-glioma (LGG) suffer recurrence or metastasis. Currently there is no effective drug treatment. While the selective COX-2 inhibitor celecoxib showed anti-neoplastic activity against several malignant tumors, its effects against LGG remain to be elucidated. Ours is the first report that the expression level of COX-2 in brain tissue samples from patients with LGG and in LGG cell lines is higher than in the non-neoplastic region and in normal brain cells. We found that celecoxib attenuated LGG cell proliferation in a dose-dependent manner. It inhibited the generation of prostaglandin E2 and induced apoptosis and cell-cycle arrest. We also show that celecoxib hampered the activation of the Akt/survivin- and the Akt/ID3 pathway in LGGs. These findings suggest that celecoxib may have a promising therapeutic potential and that the early treatment of LGG patients with the drug may be beneficial.

Inhibition of cell survival and proliferation by nimbolide in human androgen-independent prostate cancer (PC-3) cells: involvement of the PI3K/Akt pathway

Prostate cancer is most common malignancy among men in the world. PI3K-Akt signaling appears to be critical to prostate cancer cell proliferation and survival. Our earlier study reveals that nimbolide (2 µM) prevents cell survival via IGF signaling pathway through PI3K/Akt and induces apoptosis in PC-3 cell line. Akt mediates the phosphorylation and activation of mTOR that plays a critical role in the regulation of protein translation and synthesis, angiogenesis, and cell cycle progression. The present study was aimed to investigate the effect of nimbolide on tPI3K, tAkt, pAkt, tmTOR, GSK3β, pGSK3β, PCNA, c-Myc, Cyclin D1, and Survivin protein levels by western blot analysis. Apoptosis was visualized by Ao/EtBr dual staining (20×), and protein expression of PCNA by immunocytochemistry was performed. Molecular docking was performed to understand the possible interaction between nimbolide and Akt, PCNA, and Cyclin D1. Nimbolide altered the PI3K-Akt-mediated cell survival and proliferative molecules. Thus, nimbolide exerted anticancer effects in vitro by representing the PI3K-Akt-mTOR pathway in PC-3 cells. Thereby, it acts as a potent anticancer drug for prostate cancer.

Natural Compounds as Occult Ototoxins? Ginkgo biloba Flavonoids Moderately Damage Lateral Line Hair Cells

Several drugs, including aminoglycosides and platinum-based chemotherapy agents, are well known for their ototoxic properties. However, FDA-approved drugs are not routinely tested for ototoxicity, so their potential to affect hearing often goes unrecognized. This issue is further compounded for natural products, where there is a lack of FDA oversight and the manufacturer is solely responsible for ensuring the safety of their products. Natural products such as herbal supplements are easily accessible and commonly used in the practice of traditional eastern and alternative medicine. Using the zebrafish lateral line, we screened a natural products library to identify potential ototoxins. We found that the flavonoids quercetin and kaempferol, both from the Gingko biloba plant, demonstrated significant ototoxicity, killing up to 30 % of lateral line hair cells. We then examined a third Ginkgo flavonoid, isorhamnetin, and found similar levels of ototoxicity. After flavonoid treatment, surviving hair cells demonstrated reduced uptake of the vital dye FM 1-43FX, suggesting that the health of the remaining hair cells was compromised. We then asked if these flavonoids enter hair cells through the mechanotransduction channel, which is the site of entry for many known ototoxins. High extracellular calcium or the quinoline derivative E6 berbamine significantly protected hair cells from flavonoid damage, implicating the transduction channel as a site of flavonoid uptake. Since known ototoxins activate cellular stress responses, we asked if reactive oxygen species were necessary for flavonoid ototoxicity. Co-treatment with the antioxidant D-methionine significantly protected hair cells from each flavonoid, suggesting that antioxidant therapy could prevent hair cell loss. How these products affect mammalian hair cells is still an open question and will be the target of future experiments. However, this research demonstrates the potential for ototoxic damage caused by unregulated herbal supplements and suggests that further supplement characterization is warranted.

Cytotoxic potential of selected medicinal plants in northeast Brazil

BACKGROUND

Great biodiversity is a highlight of Brazilian flora. In contrast, the therapeutic potentialities of most species used in folk medicine remain unknown. Several of these species are commonly used to treat cancer. In this study, we investigated the cytotoxic activity of 18 plants from 16 families that are found in the northeast region of Brazil.

METHODS

The following species were studied: Byrsonima sericea DC. (Malpighiaceae), Cupania impressinervia Acev. Rodr. var. (revoluta) Radlk (Sapindaceae), Duranta repens Linn. (Verbenaceae), Helicostylis tomentosa (Poepp. & Endl) Rusby (Moraceae), Himatanthus bracteatus (A.DC.) Woodson (Apocynaceae), Ipomoea purga (Wender.) Hayne (Convolvulaceae), Ixora coccinea Linn. (Rubiaceae), Mabea piriri Aubl. (Euphorbiaceae), Miconia minutiflora (Melastomataceae), Momordica charantia L. (Cucurbitaceae), Ocotea glomerata (Nees) Mez (Lauraceae), Ocotea longifolia Kunth (Oreodaphne opifera Mart. Nees) (Lauraceae), Pavonia fruticosa (Mill.) Fawc. & Rendle (Malvaceae), Psychotria capitata Ruiz & Pav. (Rubiaceae), Schefflera morototoni (Aubl.) Maguire, Steyerm. & Frodin (Araliaceae), Solanum paludosum Moric. (Solanaceae), Xylopia frutescens Aubl. (Annonaceae) and Zanthoxylum rhoifolium Lam. (Rutaceae). Their dried leaves, stems, flowers or fruits were submitted to different solvent extractions, resulting in 55 extracts. After incubating for 72 h, the cytotoxicity of each extract was tested against tumor cell lines using the alamar blue assay.

RESULTS

The B. sericea, D. repens, H. bracteatus, I. purga, I. coccinea, M. piriri, O. longifolia and P. capitata extracts demonstrated the most potent cytotoxic activity. The chloroform soluble fractions of D. repens flowers and the hexane extract of I. coccinea flowers led to the isolation of quercetin and a mixture of α- and β-amyrin, respectively, and quercetin showed moderate cytotoxic activity.

CONCLUSION

The B. sericea, D. repens, H. bracteatus, I. purga, I. coccinea, M. piriri, O. longifolia and P. capitata plants were identified as having potent cytotoxic effects. Further investigations are required to determine the mechanisms of cytotoxicity exhibited and their in vivo activities. This work reinforces the need to understand the therapeutics potentialities of Brazilian medicinal plants.

Quercetin-loaded freeze-dried nanomicelles: Improving absorption and anti-glioma efficiency in vitro and in vivo

To improve its poor aqueous solubility and stability, the potential chemopreventive agent quercetin was encapsulated in freeze-dried polymeric micelles by a thin film hydration and vacuum freeze-drying process before being used for glioma chemotherapy. The micelle characteristics, release profile, cellular uptake, intracellular drug concentration, transport across the blood-brain barrier, and antitumor efficiency in vivo were investigated. Results showed that the particle size of quercetin-loaded freeze-dried nanomicelles (QUE-FD-NMs) ranged from 20 to 80nm, with an efficiently sustained release profile. Increased intracellular uptake into Caco-2 cells with low cytotoxicity, efficient penetration of BBB, and powerful cytotoxicity on C6 glioma cells were observed. QUE-FD-NMs accumulated in tumor-bearing brain tissues and exhibited significant antitumor effects in vivo, which significantly benefited the survival of glioma-bearing mice. These findings suggest that freeze-drying micelles loaded with quercetin is a promising drug delivery method for glioma therapy.

Pharmacokinetics and antitumor efficacy of DSPE-PEG2000 polymeric liposomes loaded with quercetin and temozolomide: Analysis of their effectiveness in enhancing the chemosensitization of drug-resistant glioma cells

In the present study, a new type of DSPE-PEG2000 polymeric liposome for the brain-targeted delivery of poorly water-soluble anticancer drugs was successfully prepared and characterized. The nanoparticles were formed by the self-assembly of an amphiphilic polymer consisting of hydrophilic 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE‑PEG2000). These nanoliposomes served as a safe delivery platform for the simultaneous delivery of quercetin (QUE) and temozolomide (TMZ) to rat brains. The 2-in-1 PEG2000‑DSPE nanoliposomes containing QUE and TMZ (QUE/TMZ-NLs) were rapidly taken up by the U87 glioma cells in vitro, whereas at the same concentrations, the amounts of the free drugs taken up were minimal. The QUE/TMZ-NLs showed an enhanced potency in the U87 cells and the TMZ-resistant U87 cells (U87/TR cells), possibly due to the high intracellular drug concentration and the subsequent drug release. In vivo biodistribution experiments revealed a significant accumulation of QUE/TMZ-NLs in the brain, with significantly increased plasma concentrations of QUE and TMZ, as well as delayed clearance in our rat model of glioma. The results were not so significant for the QUE-loaded nanoliposomes (QUE-NLs) and free TMZ. The findings of our study establish the DSPE‑PEG2000 polymeric liposome as a novel and effective nanocarrier for enhancing drug delivery to brain tumors.

Effects of Flavonoids from Food and Dietary Supplements on Glial and Glioblastoma Multiforme Cells

Quercetin, catechins and proanthocyanidins are flavonoids that are prominently featured in foodstuffs and dietary supplements, and may possess anti-carcinogenic activity. Glioblastoma multiforme is the most dangerous form of glioma, a malignancy of the brain connective tissue. This review assesses molecular structures of these flavonoids, their importance as components of diet and dietary supplements, their bioavailability and ability to cross the blood-brain barrier, their reported beneficial health effects, and their effects on non-malignant glial as well as glioblastoma tumor cells. The reviewed flavonoids appear to protect glial cells via reduction of oxidative stress, while some also attenuate glutamate-induced excitotoxicity and reduce neuroinflammation. Most of the reviewed flavonoids inhibit proliferation of glioblastoma cells and induce their death. Moreover, some of them inhibit pro-oncogene signaling pathways and intensify the effect of conventional anti-cancer therapies. However, most of these anti-glioblastoma effects have only been observed in vitro or in animal models. Due to limited ability of the reviewed flavonoids to access the brain, their normal dietary intake is likely insufficient to produce significant anti-cancer effects in this organ, and supplementation is needed.

Inhibition of autophagy induced by quercetin at a late stage enhances cytotoxic effects on glioma cells

Glioma is the most common primary brain tumor in the central nervous system (CNS) with high morbidity and mortality in adults. Although standardized comprehensive therapy has been adapted, the prognosis of glioma patients is still frustrating and thus novel therapeutic strategies are urgently in need. Quercetin (Quer), an important flavonoid compound found in many herbs, is shown to be effective in some tumor models including glioma. Recently, it is reported that adequate regulation of autophagy can strengthen cytotoxic effect of anticancer drugs. However, it is not yet fully clear how we should modulate autophagy to achieve a satisfactory therapeutic effect. 3-Methyladenine (3-MA) and Beclin1 short hairpin RNA (shRNA) were used to inhibit the early stage of autophage while chloroquine (CQ) to inhibit the late stage. MTT assay was implemented to determine cell viability. Transmission electron microscopy, western blot, and immunohistochemistry were adopted to evaluate autophagy. Western blot, flow cytometry, and immunohistochemistry were used to detect apoptosis. C6 glioma xenograft models were established to assess the therapeutic effect (the body weight change, the median survival time, and tumor volume) in vivo. Quercetin can inhibit cell viability and induce autophagy of U87 and U251 glioma cells in a dose-dependent manner. Inhibition of early-stage autophagy by 3-MA or shRNA against Beclin1 attenuated the quercetin-induced cytotoxicity. In contrast, suppression of autophagy at a late stage by CQ enhanced the anti-glioma efficiency of quercetin. Therapeutic effect of quercetin for malignant glioma can be strengthened by inhibition of autophagy at a late stage, not initial stage, which may provide a novel opportunity for glioma therapy.