Sirtuin-2 activity is required for glioma stem cell proliferation arrest but not necrosis induced by resveratrol

Sirtuins Affect Cancer Stem Cells via Epigenetic Regulation of Autophagy

Sirtuins (SIRTs) are stress-responsive proteins that regulate several post-translational modifications, partly by acetylation, deacetylation, and affecting DNA methylation. As a result, they significantly regulate several cellular processes. In essence, they prolong lifespan and control the occurrence of spontaneous tumor growth. Members of the SIRT family have the ability to govern embryonic, hematopoietic, and other adult stem cells in certain tissues and cell types in distinct ways. Likewise, they can have both pro-tumor and anti-tumor effects on cancer stem cells, contingent upon the specific tissue from which they originate. The impact of autophagy on cancer stem cells, which varies depending on the specific circumstances, is a very intricate phenomenon that has significant significance for clinical and therapeutic purposes. SIRTs exert an impact on the autophagy process, whereas autophagy reciprocally affects the activity of certain SIRTs. The mechanism behind this connection in cancer stem cells remains poorly understood. This review presents the latest findings that position SIRTs at the point where cancer cells and autophagy interact. Our objective is to highlight the various roles of distinct SIRTs in cancer stem cell-related functions through autophagy. This would demonstrate their significance in the genesis and recurrence of cancer and offer a more precise understanding of their treatment possibilities in relation to autophagy.

Resveratrol as an antitumor agent for glioblastoma multiforme: Targeting resistance and promoting apoptotic cell deaths

Glioblastoma multiforme (GBM) is one of the most aggressive brain and spinal cord tumors. Despite the significant development in application of antitumor drugs, no significant increases have been observed in the survival rates of patients with GBM, as GBM cells acquire resistance to conventional anticancer therapeutic agents. Multiple studies have revealed that PI3K/Akt, MAPK, Nanog, STAT 3, and Wnt signaling pathways are involved in GBM progression and invasion. Besides, biological processes such as anti-apoptosis, autophagy, angiogenesis, and stemness promote GBM malignancy. Resveratrol (RESV) is a non-flavonoid polyphenol with high antitumor activity, the potential of which, regulating signaling pathways involved in cancer malignancy, have been demonstrated by many studies. Herein, we present the potential of RESV in both single and combination therapy- targeting various signaling pathways- which induce apoptotic cell death, re-sensitize cancer cells to radiotherapy, and induce chemo-sensitizing effects to eventually inhibit GBM progression.

Sirtuins, resveratrol and the intertwining cellular pathways connecting them

Sirtuins are a family of NAD+-dependent deacylases with numerous physiological and pathological implications, which lately became an attractive therapeutic target. Sirtuin-activating compounds (STACs) could be useful in disease prevention and treatment. Despite its bioavailability issues, resveratrol exerts a myriad of beneficial effects, known as the "resveratrol paradox". Modulation of sirtuins' expression and activity may, in fact, underlie many of resveratrol revered actions; however, the cellular pathways affected by modulating the activity of each sirtuin isoform, in different physio-pathological conditions, are not fully known. The purpose of this review was to summarize recent reports concerning the effects of resveratrol on the activity of sirtuins in different experimental settings, focusing on in vitro and in vivo preclinical studies. Most reports concern SIRT1, however recent studies dive into the effects initiated via other isoforms. Numerous cellular signaling pathways were reported to be modulated by resveratrol in a sirtuin-dependent manner (increased phosphorylation of MAPKs, AKT, AMPK, RhoA, BDNF, decreased activation of NLRP3 inflammasome, NF-κB, STAT3, upregulation of SIRT1/SREBP1c pathway, reduced β-amyloid via SIRT1-NF-κB-BACE1 signaling and counteracting mitochondrial damage by deacetylating PGC-1α). Thus, resveratrol may be the ideal candidate in the search for STACs as a tool for preventing and treating inflammatory and neurodegenerative diseases.

The Role of NAD+, SIRTs Interactions in Stimulating and Counteracting Carcinogenesis

The World Health Organization has identified oncological diseases as one of the most serious health concerns of the current century. Current research on oncogenesis is focused on the molecular mechanisms of energy-biochemical reprogramming in cancer cell metabolism, including processes contributing to the Warburg effect and the pro-oncogenic and anti-oncogenic roles of sirtuins (SIRTs) and poly-(ADP-ribose) polymerases (PARPs). However, a clear understanding of the interaction between NAD⁺, SIRTs in cancer development, as well as their effects on carcinogenesis, has not been established, and literature data vary greatly. This work aims to provide a summary and structure of the available information on NAD⁺, SIRTs interactions in both stimulating and countering carcinogenesis, and to discuss potential approaches for pharmacological modulation of these interactions to achieve an anticancer effect.

The function of histone methylation and acetylation regulators in GBM pathophysiology

Glioblastoma (GBM) is the most common and lethal primary brain malignancy and is characterized by a high degree of intra and intertumor cellular heterogeneity, a starkly immunosuppressive tumor microenvironment, and nearly universal recurrence. The application of various genomic approaches has allowed us to understand the core molecular signatures, transcriptional states, and DNA methylation patterns that define GBM. Histone posttranslational modifications (PTMs) have been shown to influence oncogenesis in a variety of malignancies, including other forms of glioma, yet comparatively less effort has been placed on understanding the transcriptional impact and regulation of histone PTMs in the context of GBM. In this review we discuss work that investigates the role of histone acetylating and methylating enzymes in GBM pathogenesis, as well as the effects of targeted inhibition of these enzymes. We then synthesize broader genomic and epigenomic approaches to understand the influence of histone PTMs on chromatin architecture and transcription within GBM and finally, explore the limitations of current research in this field before proposing future directions for this area of research.

Glioblastoma: Current Status, Emerging Targets, and Recent Advances

Glioblastoma (GBM) is a highly malignant brain tumor characterized by a heterogeneous population of genetically unstable and highly infiltrative cells that are resistant to chemotherapy. Although substantial efforts have been invested in the field of anti-GBM drug discovery in the past decade, success has primarily been confined to the preclinical level, and clinical studies have often been hampered due to efficacy-, selectivity-, or physicochemical property-related issues. Thus, expansion of the list of molecular targets coupled with a pragmatic design of new small-molecule inhibitors with central nervous system (CNS)-penetrating ability is required to steer the wheels of anti-GBM drug discovery endeavors. This Perspective presents various aspects of drug discovery (challenges in GBM drug discovery and delivery, therapeutic targets, and agents under clinical investigation). The comprehensively covered sections include the recent medicinal chemistry campaigns embarked upon to validate the potential of numerous enzymes/proteins/receptors as therapeutic targets in GBM.

Flavonoids as Sirtuin Modulators

Sirtuins (SIRTs) are described as NAD+-dependent deacetylases, also known as class III histone deacetylases. So far, seven sirtuin genes (SIRTS 1-7) have been identified and characterized in mammals and also known to occur in bacteria and eukaryotes. SIRTs are involved in various biological processes including endocrine system, apoptosis, aging and longevity, diabetes, rheumatoid arthritis, obesity, inflammation, etc. Among them, the best characterized one is SIRT1. Actually, small molecules seem to be the most effective SIRT modulators. Flavonoids have been reported to possess many positive effects favrable for human health, while a relatively less research has been reported so far on their funcions as SIRT modulation mechanisms. In this regard, we herein aimed to focus on modulatory effects of flavonoids on SIRTs as the most common secondary metabolites in natural products. Our literature survey covering the years of 2006-2021 pointed out that flavonoids frequently interact with SIRT1 and SIRT3 followed by SIRT6. It can be also concluded that some popular flavonoid derivatives, e.g. resveratrol, quercetin, and catechin derivatives came forward in terms of SIRT modulation.

Natural Compounds as Promising Adjuvant Agents in The Treatment of Gliomas

In humans, glioblastoma is the most prevalent primary malignant brain tumor. Usually, glioblastoma has specific characteristics, such as aggressive cell proliferation and rapid invasion of surrounding brain tissue, leading to a poor patient prognosis. The current therapy-which provides a multidisciplinary approach with surgery followed by radiotherapy and chemotherapy with temozolomide-is not very efficient since it faces clinical challenges such as tumor heterogeneity, invasiveness, and chemoresistance. In this respect, natural substances in the diet, integral components in the lifestyle medicine approach, can be seen as potential chemotherapeutics. There are several epidemiological studies that have shown the chemopreventive role of natural dietary compounds in cancer progression and development. These heterogeneous compounds can produce anti-glioblastoma effects through upregulation of apoptosis and autophagy; allowing the promotion of cell cycle arrest; interfering with tumor metabolism; and permitting proliferation, neuroinflammation, chemoresistance, angiogenesis, and metastasis inhibition. Although these beneficial effects are promising, the efficacy of natural compounds in glioblastoma is limited due to their bioavailability and blood-brain barrier permeability. Thereby, further clinical trials are necessary to confirm the in vitro and in vivo anticancer properties of natural compounds. In this article, we overview the role of several natural substances in the treatment of glioblastoma by considering the challenges to be overcome and future prospects.

Targeting of cancer cell death mechanisms by resveratrol: a review

Cancer cell death is the utmost aim in cancer therapy. Anti-cancer agents can induce apoptosis, mitotic catastrophe, senescence, or autophagy through the production of free radicals and induction of DNA damage. However, cancer cells can acquire some new properties to adapt to anti-cancer agents. An increase in the incidence of apoptosis, mitotic catastrophe, senescence, and necrosis is in favor of overcoming tumor resistance to therapy. Although an increase in the autophagy process may help the survival of cancer cells, some studies indicated that stimulation of autophagy cell death may be useful for cancer therapy. Using some low toxic agents to amplify cancer cell death is interesting for the eradication of clonogenic cancer cells. Resveratrol (a polyphenol agent) may affect various signaling pathways related to cell death. It can induce death signals and also downregulate the expression of anti-apoptotic genes. Resveratrol has also been shown to modulate autophagy and induce mitotic catastrophe and senescence in some cancer cells. This review focuses on the important targets and mechanisms for the modulation of cancer cell death by resveratrol.

The Aneugenicity of Ketone Bodies in Colon Epithelial Cells Is Mediated by Microtubule Hyperacetylation and Is Blocked by Resveratrol

Diabetes mellitus (DM) is considered to be associated with an increased risk of colorectal cancer. Recent studies have also revealed that tubulin hyperacetylation is caused by a diabetic status and we have reported previously that, under microtubule hyperacetylation, a microtubule severing protein, katanin-like (KL) 1, is upregulated and contributes to tumorigenesis. To further explore this phenomenon, we tested the effects of the ketone bodies, acetoacetate and β-hydroxybutyrate, in colon and fibroblast cells. Both induced microtubule hyperacetylation that responded differently to a histone deacetylase 3 knockdown. These two ketone bodies also generated intracellular reactive oxygen species (ROS) and hyperacetylation was commonly inhibited by ROS inhibitors. In a human fibroblast-based microtubule sensitivity test, only the KL1 human katanin family member showed activation by both ketone bodies. In primary cultured colon epithelial cells, these ketone bodies reduced the tau protein level and induced KL1- and α-tubulin acetyltransferase 1 (ATAT1)-dependent micronucleation. Resveratrol, known for its tumor preventive and tubulin deacetylation effects, inhibited this micronucleation. Our current data thus suggest that the microtubule hyperacetylation induced by ketone bodies may be a causal factor linking DM to colorectal carcinogenesis and may also represent an adverse effect of them that needs to be controlled if they are used as therapeutics.

Therapeutic potentials of resveratrol in combination with radiotherapy and chemotherapy during glioblastoma treatment: a mechanistic review

Glioblastoma, WHO grade IV astrocytoma, is the most aggressive type of brain tumors. These cancerous cells have a rapid growth rate, tendency to penetrate vital brain structures, molecular heterogeneity, etc. and this cancer is associated with a poor prognosis and low survival rate. Due to the resistance of glioblastoma cells to conventional therapeutic modalities (such as radiation therapy and chemotherapy) as well as the adverse effects of these modalities, the researchers have attempted to discover an appropriate alternative or adjuvant treatment for glioblastoma. Resveratrol, as an herbal and natural polyphenolic compound, has anti-tumoral property and has shown to be effective in GBM treatment. Resveratrol exerts its anti-tumoral effect through various mechanisms such as regulation of cell cycle progression and cell proliferation, autophagy, oxidant system, apoptosis pathways, and so on. Resveratrol in combination with radiation therapy and chemotherapy has also been used. In the present study, we summarized the current findings on therapeutic potentials of resveratrol in glioblastoma radiotherapy and chemotherapy.

Targeting cancer stem cells by nutraceuticals for cancer therapy

Accumulating evidence has demonstrated that cancer stem cells (CSCs) play an essential role in tumor progression and reoccurrence and drug resistance. Multiple signaling pathways have been revealed to be critically participated in CSC development and maintenance. Emerging evidence indicates that numerous chemopreventive compounds, also known as nutraceuticals, could eliminate CSCs in part via regulating several signaling pathways. Therefore, in this review, we will describe the some natural chemopreventive agents that target CSCs in a variety of human malignancies, including soy isoflavone, curcumin, resveratrol, tea polyphenols, sulforaphane, quercetin, indole-3-carbinol, 3,3'-diindolylmethane, withaferin A, apigenin, etc. Moreover, we discuss that eliminating CSCs by nutraceuticals might be a promising strategy for treating human cancer via overcoming drug resistance and reducing tumor reoccurrence.

Sirtuin 2 (SIRT2): Confusing Roles in the Pathophysiology of Neurological Disorders

As a type of nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylases, sirtuin 2 (SIRT2) is predominantly found in the cytoplasm of cells in the central nervous system (CNS), suggesting its potential role in neurological disorders. Though SIRT2 is generally acknowledged to accelerate the development of neurological pathologies, it protects the brain from deterioration in certain circumstances. This review summarized the complex roles SIRT2 plays in the pathophysiology of diverse neurological disorders, compared and analyzed the discrete roles of SIRT2 in different conditions, and provided possible explanations for its paradoxical functions. In the future, the rapid growth in SIRT2 research may clarify its impacts on neurological disorders and develop therapeutic strategies targeting this protein.

Resveratrol, cancer and cancer stem cells: A review on past to future

Cancer remains to be an unresolved medical challenge despite of tremendous advancement in basic science research and clinical medicine. One of the major limitations is due to the side effects of chemotherapy which remains to be palliative without offering any permanent cure for cancer. Cancer stem cells (CSCs) are the subpopulation of cells in tumors that remain viable even after surgery, chemo- and radio-therapy that eventually responsible for tumor relapse. Hence, by eliminating non-stem cancer cells and cancer stem cells from the patient, permanent cure is expected. Phytochemicals have been under the intensive study to target these CSCs effectively and permanently as they do not cause any side effects. Resveratrol (RSV) is one such compound attaining lot of interest in recent days to target CSCs either alone or in combination. RSV has been used by several researchers to target cancer cells in a variety of disease models, however its CSC targeting abilities are under intensive study at present. This review is to summarize the effects of RSV under in vitro and in vivo conditions along with advantages and disadvantages of its uses against cancer cells and cancer stem cells. From the first reports on phytochemical applications against cancer and cancer stem cells in 1997 and 2002 respectively followed by later reports, up to date observations and developments are enlisted from PubMed in this comprehensive review. RSV is shown to be a potential compound having impact on altering the signal transduction pathways in cancer cells. However, the effects are variable under in vitro and in vivo conditions, and also with its use alone or in combination with other small molecules. Past research on RSV is emphasizing the importance of in vivo experimental models and clinical trials with different prospective combinations, is a hope for future promising treatment regimen.

The uses of resveratrol for neurological diseases treatment and insights for nanotechnology based-drug delivery systems

Neurological disorders have been growing in recent years and are highly prevalent globally. Resveratrol (RES) is a natural product from plant sources such as grape skins. This compound has shown biological activity in many diseases, in particular, those that act on the central nervous system. The mechanism of action and the key points in neurological disorders were described and show the targeted mechanism of action. Due to the insolubility of this compound; the use of nanotechnology-based systems has been proposed for the incorporation of RES and RES-loaded nanocarriers have been designed for intranasal administration, oral or parenteral routes to deliver it to the brain. In general, these nanosystems have shown to be effective in many studies, pharmacological and pharmacokinetic assays, as well as some cell studies. The outcomes show that RES has been reported in human clinical trials for some neurological diseases, although no studies were performed in humans using nanocarriers, animal and/or cellular models have been reported to show good results regarding therapeutics on neurological diseases. Thus, the use of this nutraceutical has shown true for neurological diseases and its loading into nanocarriers displaying good results on the stability, delivery and targeting to the brain.

Advances in histone deacetylase inhibitors in targeting glioblastoma stem cells

Glioblastoma multiforme (GBM) is a lethal grade IV glioma (WHO classification) and widely prevalent primary brain tumor in adults. GBM tumors harbor cellular heterogeneity with the presence of a small subpopulation of tumor cells, described as GBM cancer stem cells (CSCs) that pose resistance to standard anticancer regimens and eventually mediate aggressive relapse or intractable progressive GBM. Existing conventional anticancer therapies for GBM do not target GBM stem cells and are mostly palliative; therefore, exploration of new strategies to target stem cells of GBM has to be prioritized for the development of effective GBM therapy. Recent developments in the understanding of GBM pathophysiology demonstrated dysregulation of epigenetic mechanisms along with the genetic changes in GBM CSCs. Altered expression/activity of key epigenetic regulators, especially histone deacetylases (HDACs) in GBM stem cells has been associated with poor prognosis; inhibiting the activity of HDACs using histone deacetylase inhibitors (HDACi) has been promising as mono-therapeutic in targeting GBM and in sensitizing GBM stem cells to an existing anticancer regimen. Here, we review the development of pan/selective HDACi as potential anticancer agents in targeting the stem cells of glioblastoma as a mono or combination therapy.

Resveratrol Inhibition of Renal Cancer Stem Cell Characteristics and Modulation of the Sonic Hedgehog Pathway

AIMS

Renal cell cancers typically exhibit high metastasis and recurrence, and this is thought to be due to renal cancer stem cells (CSCs). Meanwhile, aberrant activation of Sonic hedgehog (Shh) signaling is linked with CSCs. Resveratrol has direct or indirect impacts on the pathological activities of CSCs. However, the effects of resveratrol on renal CSCs remain to be elucidated.

METHODS

We cultured renal CSCs in serum-free medium. Western blotting was used to analyze the expression levels of related proteins. The mRNA changes were detected by qRT-PCR after resveratrol treatment. The CD133⁺ cells were quantified by flow cytometry analysis. Immunofluorescence staining images showed the changes in CD44 and Smoothened expression in the cell spheres.

RESULTS

Renal CSCs were enriched by tumorsphere formation assays of ACHN and 786-O cells. Resveratrol treatments markedly decreased the size and number of cell spheres and downregulated the expression of the Shh pathway-related proteins and CSCs markers. Moreover, we observed that resveratrol inhibited cell proliferation and induced cell apoptosis, while purmorphamine upregulated the Shh pathway and weakened the effects of resveratrol on renal CSCs.

CONCLUSIONS

These results suggested that resveratrol is a potential novel therapeutic agent that targets inactivation of renal CSCs by affecting the function of the Shh pathway.

The role of SIRT2 in cancer: A novel therapeutic target

Sirtuin 2 (SIRT2) belongs to the sirtuins family. It exists in many tissues and organs of the human body and regulates a wide range of biological functions. Studies have found that the abnormal expression of SIRT2 was associated with a variety of malignant tumors. SIRT2 possesses an important role in tumorigenesis, with both tumor-promoting and tumor-suppressing function. However, the mechanisms in which SIRT2 plays the roles in cancer are still controversial. This article reviews the role and molecular mechanism of SIRT2 in tumor evolution, and provides ideas for future research in this field, to guide the targeted therapy and drug development of related malignancies.

The Plant-Derived Compound Resveratrol in Brain Cancer: A Review

Despite intensive research, malignant brain tumors are among the most difficult to treat due to high resistance to conventional therapeutic approaches. High-grade malignant gliomas, including glioblastoma and anaplastic astrocytoma, are among the most devastating and rapidly growing cancers. Despite the ability of standard treatment agents to achieve therapeutic concentrations in the brain, malignant gliomas are often resistant to alkylating agents. Resveratrol is a plant polyphenol occurring in nuts, berries, grapes, and red wine. Resveratrol crosses the blood‒brain barrier and may influence the central nervous system. Moreover, it influences the enzyme isocitrate dehydrogenase and, more importantly, the resistance to standard treatment via various mechanisms, such as O6-methylguanine methyltransferase. This review summarizes the anticancer effects of resveratrol in various types of brain cancer. Several in vitro and in vivo studies have presented promising results; however, further clinical research is necessary to prove the therapeutic efficacy of resveratrol in brain cancer treatment.

SIRT5 downregulation is associated with poor prognosis in glioblastoma

OBJECTIVE

Sirtuins (SIRT) are NAD+-dependent protein deacetylases that are involved in the regulation of cancer-associated pathways. However, the biological role of these deacetylases remains elusive in glioblastoma (GBM). Here, we evaluated the effects of 7 sirtuins regarding their occurrence and prognostic value for GBM.

METHODS

In this research, the effects of SIRT5 on the occurrence and prognosis of GBM were evaluated using integrative bioinformatics analyses.

RESULTS

Based on comprehensive analyses of data obtained from web-based bioinformatics platforms, the data demonstrate that only SIRT5 expression is statistically decreased in GBM tissues. The clinical relevance analysis shows that downregulation of SIRT5 is significantly correlated with a shorter survival time. Moreover, the expression levels of SIRT5 were confirmed to be negatively associated with DNA methylation status. In addition, a protein-protein interaction network was constructed to determine the relationship of genes coexpressed with SIRT5. Functional enrichment analysis revealed that SIRT5 was potentially involved in epithelial-mesenchymal transition and in regulating cell communications.

CONCLUSIONS

Collectively, our results indicate that SIRT5 acts as a potential suppresser during tumorigenesis, and suggest that SIRT5 may be a promising prognostic biomarker of GBM.

Resveratrol Action on Lipid Metabolism in Cancer

Cancer diseases have the leading position in human mortality nowadays. The age of oncologic patients is still decreasing, and the entire scientific society is eager for new ways to fight against cancer. One of the most discussed issues is prevention by means of natural substances. Resveratrol is a naturally occurring plant polyphenol with proven antioxidant, anti-inflammatory, and anticancer effects. Tumor cells display specific changes in the metabolism of various lipids. Resveratrol alters lipid metabolism in cancer, thereby affecting storage of energy, cell signaling, proliferation, progression, and invasiveness of cancer cells. At the whole organism level, it contributes to the optimal metabolism extent with respect to the demands of the organism. Thus, resveratrol could be used as a preventive and anticancer agent. In this review, we focus on some of the plethora of lipid pathways and signal molecules which are affected by resveratrol during carcinogenesis.

NAMPT as a Dedifferentiation-Inducer Gene: NAD+ as Core Axis for Glioma Cancer Stem-Like Cells Maintenance

Glioma Cancer Stem-Like Cells (GSCs) are a small subset of CD133⁺ cells with self-renewal properties and capable of initiating new tumors contributing to Glioma progression, maintenance, hierarchy, and complexity. GSCs are highly resistant to chemo and radiotherapy. These cells are believed to be responsible for tumor relapses and patients' fatal outcome after developing a recurrent Glioblastoma (GBM) or High Grade Glioma (HGG). GSCs are cells under replicative stress with high demands on NAD⁺ supply to repair DNA, maintain self-renewal capacity and to induce tumor plasticity. NAD⁺ feeds Poly-ADP polymerases (PARP) and NAD⁺-dependent deacetylases (SIRTUINS) contributing to GSC phenotype. This energetic core axis is mainly controlled by the rate-limiting enzyme nicotinamide phosphoribosyltransferase (NAMPT), an important oncogene contributing to tumor dedifferentiation. Targeting GSCs depicts a new frontier in Glioma therapy; hence NAMPT could represent a key regulator for GSCs maintenance. Its inhibition may attenuate GSCs properties by decreasing NAD⁺ supply, consequently contributing to a better outcome together with current therapies for Glioma control.

Activation of KRas-ERK1/2 signaling drives the initiation and progression of glioma by suppressing the acetylation of histone H4 at lysine 16

BACKGROUND/AIMS

Acetylation of H4 at lysine 16 (H4K16ac) has been well-characterized as an acetylated mark, and the expression of which is closely associated with the tumorigenesis of human cancers. This study aimed to reveal whether KRas mutation drives the initiation and progression of glioma via modulation of H4 acetylation.

METHODS

Changes of H4K16 acetylation in human glioblastoma A172 cells following transfection with a plasmid for expression of mutant KRas were tested by western blot analysis. MTT assay, transwell assay, soft-agar colony formation assay, RT-PCR and chromatin immunoprecipitation were carried out to evaluate the effect of H4K16ac on A172 cells growth and migration. Furthermore, the enzymes participating in the deacetylation of H4K16ac were studied by using RT-PCR and western blot analysis.

RESULTS

H4K16ac was found to be deacetylated by KRas-ERK1/2 activation. H4K16Q (a plasmid for mimicking H4K16ac) repressed A172 cells viability, colony formation, and migratory capacity. Besides, H4K16ac was capable of regulating the transcription of several ERK1/2 pathway downstream genes. KRas-ERK1/2 signaling repressed H4 acetylation at K16 via modulation of a histone deacetylase Sirt2, as well as a histone acetyl-transferase TIP60. Moreover, KRas-ERK1/2 inhibited TIP60 via an MDM2-dependnet fashion.

CONCLUSION

Our results suggest that activation of KRas-ERK1/2 signaling participates in the onset and progression of glioma at least partially through modulating acetylation of H4 at K16. KRas-ERK1/2 signaling mediates the acetylation of H4K16 via Sirt2 and MDM2-dependnet degeneration of TIP60.

Early Protection by Resveratrol in Rat Lung Transplantation

BACKGROUND Resveratrol is a multifunctional bioactive substance that has effects in anti-inflammation and prevention of ischemia-reperfusion injury. This study compared the inflammation and expression of related proteins during the early stages after transplantation to explore the effects and mechanisms of resveratrol on transplanted lung. MATERIAL AND METHODS Sprague-Dawley rats were randomized to receive pretreatment of resveratrol suspension (60 mg/kg; RES group), dexamethasone (1 mg/kg; DEM group), or normal saline solution (2 mL/kg; control group) 1 h before lung transplantation. The cytokine concentration in the serum and bronchoalveolar lavage fluid (BALF) of the recipients was determined 24 h after transplantation. Histopathologic evaluation, including lung injury score, and the expression of necroptosis-associated proteins was assessed. RESULTS Histopathologic evaluation showed pneumocyte damage and endothelialitis associated with hemorrhage in the alveoli in the control group, the severity of which was greater than that in the other 2 groups. The levels of interleukin-6 and tumor necrosis factor-a in the serum and BALF of the RES and DEM groups were lower than those in the control group. The expression of necroptosis-associated proteins in the RES group was lower than that in the control group, and was inversely proportional to lung injury. CONCLUSIONS Pretreatment with resveratrol protected rat lung in the early stages after transplantation. We determined a relationship between necroptosis-associated proteins and transplanted lung injury, which suggests that the mechanism of lung transplantation-associated ischemia-reperfusion injury may be related to necroptosis.

Targeting cancer stem cells with dietary phytochemical - Repositioned drug combinations

The tumor microenvironment is complex with the cancer stem cell (CSC) as a member within its community. This population possesses the capacity to self-renew and to cause cellular heterogeneity of the tumor. CSCs are resistant to conventional anti-proliferative drugs. In order to be curative, it is imperative that CSCs must be eliminated by cancer therapy. A variety of dietary phytochemicals and repositioned drugs can act synergistically with conventional anti-cancer agents. In this review, we advocate the development of a novel approach, namely combination therapy by incorporating both phytochemicals and repositioned drugs to target CSCs. We cover select dietary phytochemicals (curcumin, resveratrol, EGCG, genistein) and repurposed drugs (metformin, niclosamide, thioridazine, chloroquine). Five of the eight (curcumin, resveratrol, EGCG, genistein, metformin) are listed in “The Halifax Project”, that explores “the concept of a low-toxicity ‘broad-spectrum’ therapeutic approach that could simultaneously target many key pathways and mechanisms” [1]. For these compounds, we discuss their mechanisms of action, in which models their anti-CSC activities were identified, as well as advantages, challenges and potentials of combination therapy.

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Cancer stem cells (CSCs) are the culprits for cancer drug resistance and cancer relapse.

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Dietary phytochemicals (curcumin, resveratrol, epigallocatechin gallate) target CSCs.

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Repositioned drugs (metformin, niclosamide, thioridazine) target CSCs.

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Phytochemical-drug combinations targeting CSCs may exhibit synergistic effects.

Emerging role of lipid metabolism alterations in Cancer stem cells

BACKGROUND

Cancer stem cells (CSCs) or tumor-initiating cells (TICs) represent a small population of cancer cells with self-renewal and tumor-initiating properties. Unlike the bulk of tumor cells, CSCs or TICs are refractory to traditional therapy and are responsible for relapse or disease recurrence in cancer patients. Stem cells have distinct metabolic properties compared to differentiated cells, and metabolic rewiring contributes to self-renewal and stemness maintenance in CSCs.

MAIN BODY

Recent advances in metabolomic detection, particularly in hyperspectral-stimulated raman scattering microscopy, have expanded our knowledge of the contribution of lipid metabolism to the generation and maintenance of CSCs. Alterations in lipid uptake, de novo lipogenesis, lipid droplets, lipid desaturation, and fatty acid oxidation are all clearly implicated in CSCs regulation. Alterations on lipid metabolism not only satisfies the energy demands and biomass production of CSCs, but also contributes to the activation of several important oncogenic signaling pathways, including Wnt/β-catenin and Hippo/YAP signaling. In this review, we summarize the current progress in this attractive field and describe some recent therapeutic agents specifically targeting CSCs based on their modulation of lipid metabolism.

CONCLUSION

Increased reliance on lipid metabolism makes it a promising therapeutic strategy to eliminate CSCs. Targeting key players of fatty acids metabolism shows promising to anti-CSCs and tumor prevention effects.

Under explored epigenetic modulators: role in glioma chemotherapy

Patients with somatic mutations of epigenetic regulators are characterized by aberrant chromatin modification patterns. Recent mechanistic studies pairing chemical tool compounds and deep-sequencing technology have greatly broadened our understanding of epigenetic regulation in glioma progression and underpinned alternative treatment of epigenetic inhibitors. However, the effect of most inhibitors is condition-dependent, and the overall results of clinical trials still have not been applied to patients. There is an intense need to develop more potent and specific compounds as well as identify the population who may achieve clinical benefits. Besides, combination therapy with conventional therapeutics is another alternative strategy. In this review, we summarize well-characterized chemical probes in glioma research and clinical translation. We also discuss the target population and combination of therapy regimens of various agents. In a holistic sense, we try to provide guidance for selecting targeted chemical probes and pave the way for personalized rational therapy.

Effects of resveratrol, curcumin, berberine and other nutraceuticals on aging, cancer development, cancer stem cells and microRNAs

Natural products or nutraceuticals have been shown to elicit anti-aging, anti-cancer and other health-enhancing effects. A key target of the effects of natural products may be the regulation of microRNA (miR) expression which results in cell death or prevents aging, diabetes, cardiovascular and other diseases. This review will focus on a few natural products, especially on resveratrol (RES), curcumin (CUR) and berberine (BBR). RES is obtained from the skins of grapes and other fruits and berries. RES may extend human lifespan by activating the sirtuins and SIRT1 molecules. CUR is isolated from the root of turmeric (Curcuma longa). CUR is currently used in the treatment of many disorders, especially in those involving an inflammatory process. CUR and modified derivatives have been shown to have potent anti-cancer effects, especially on cancer stem cells (CSC). BBR is also isolated from various plants (e.g., Coptis chinensis) and has been used for centuries in traditional medicine to treat diseases such as adult- onset diabetes. Understanding the benefits of these and other nutraceuticals may result in approaches to improve human health.

Targeting cancer stem cells and signaling pathways by resveratrol and pterostilbene

In past decades, increasing evidence regarding cancer stem cells (CSCs) may account for carcinogenesis, tumor drug-resistant, and metastasis. CSCs are even considered as the root causes of tumor recurrence and metastases. Targeting CSCs may provide a new clue to cure cancer. Epidemiological and clinical studies have suggested that intake of dietary natural products may bring health benefits including lowering risk of cancer incidence. In this review, we have particularly focused on targeting signaling pathways of CSCs by natural resveratrol and its dimethylated derivative pterostilbene. © 2017 BioFactors, 44(1):61-68, 2018.

Sirtuins at the crossroads of stemness, aging, and cancer

Sirtuins are stress‐responsive proteins that direct various post‐translational modifications (PTMs) and as a result, are considered to be master regulators of several cellular processes. They are known to both extend lifespan and regulate spontaneous tumor development. As both aging and cancer are associated with altered stem cell function, the possibility that the involvement of sirtuins in these events is mediated by their roles in stem cells is worthy of investigation. Research to date suggests that the individual sirtuin family members can differentially regulate embryonic, hematopoietic as well as other adult stem cells in a tissue‐ and cell type‐specific context. Sirtuin‐driven regulation of both cell differentiation and signaling pathways previously involved in stem cell maintenance has been described where downstream effectors involved determine the biological outcome. Similarly, diverse roles have been reported in cancer stem cells (CSCs), depending on the tissue of origin. This review highlights the current knowledge which places sirtuins at the intersection of stem cells, aging, and cancer. By outlining the plethora of stem cell‐related roles for individual sirtuins in various contexts, our purpose was to provide an indication of their significance in relation to cancer and aging, as well as to generate a clearer picture of their therapeutic potential. Finally, we propose future directions which will contribute to the better understanding of sirtuins, thereby further unraveling the full repertoire of sirtuin functions in both normal stem cells and CSCs.

Discovery and Characterization of R/S-N-3-Cyanophenyl-N'-(6-tert-butoxycarbonylamino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-yl)urea, a New Histone Deacetylase Class III Inhibitor Exerting Antiproliferative Activity against Cancer Cell Lines

A new series of N-aryl-N'-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-yl)ureas bearing an alkoxycarbonylamino group at the 6-position were synthesized and examined as putative anticancer agents targeting sirtuins in glioma cells. On the basis of computational docking combined to in vitro sirtuin 1/2 inhibition assays, we selected compound 18 [R/S-N-3-cyanophenyl-N'-(6-tert-butoxycarbonylamino-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-yl)urea] which displays a potent antiproliferative activity on various glioma cell types, assessed by quantitative videomicroscopy, eventually triggering senescence. The impact on normal glial cells was lower with a selectivity index of >10. Furthermore, human U373 and Hs683 glioblastoma cell lines served to demonstrate the inhibitory activity of 18 against histone deacetylase (HDAC) class III sirtuins 1 and 2 (SIRT1/2) by quantifying acetylation levels of histone and non-histone proteins. The translational potential of 18 was validated by an NCI-60 cell line screen and validation of growth inhibition of drug resistant cancer cell models. Eventually, the anticancer potential of 18 was validated in 3D glioblastoma spheroids and in vivo by zebrafish xenografts. In summary, compound 18 is the first representative of a new class of SIRT inhibitors opening new perspectives in the medicinal chemistry of HDAC inhibitors.

Dose-dependent short- and long-term effects of ionizing irradiation on neural stem cells in murine hippocampal tissue cultures: neuroprotective potential of resveratrol

INTRODUCTION

Radiation therapy plays an essential role in the treatment of brain tumors, but neurocognitive deficits remain a significant risk, especially in pediatric patients. In recent trials, hippocampal sparing techniques are applied to reduce these adverse effects. Here, we investigate dose-dependent effects of ionizing radiation (IR) on juvenile hippocampal neurogenesis. Additionally, we evaluate the radioprotective potential of resveratrol, a plant polyphenol recognized for its bifunctional tumor-preventive and anticancer effects.

METHODS

Organotypic entorhinal-hippocampal slice cultures from transgenic nestin-CFPnuc C57BL/J6 mice, postnatal days 3-6, were irradiated on a X-ray machine (4.5, 8, 12, and 16 Gy, single doses) after about 2 weeks. Nestin-positive neural stem cells were counted at a confocal live imaging microscope 0, 2, 4, 14, 25, and 42 days after IR. Resveratrol (15 μmol/L) was added 2 hr before and 24 hr after IR. Proliferation and cell death were assessed by BrdU pulse label, 48 hr after and by propidium iodide staining 96 hr after IR. GFAP- and NeuN-positive cells were counted 42 days after IR in cryosectioned immunofluorescence-stained slices.

RESULTS

The observed age-related changes of nestin-positive stem cells in the organotypic slice culture model resembled the reduction of neural stem cells in vivo. IR (4.5-16 Gy) led to a dose-dependent damage of the neural stem cell pool in the dentate gyrus. No recovery was seen within 42 days after doses from 4.5 Gy onward. The decline of nestin-positive cells was paralleled by increased cell death and decreased proliferation. The number of GFAP-positive cells was significantly enhanced. No significant change was detected in the overall NeuN-positive cell population, whereas the number of newborn, NeuN/BrdU double-positive neurons was reduced. Resveratrol treatment reversed the irradiation-induced decline of neural stem cells.

CONCLUSION

The neuroprotective action of resveratrol on irradiated hippocampal tissue warrants further investigation as a possible supplement to hippocampal sparing procedures.

SIRT2 mediates NADH-induced increases in Nrf2, GCL, and glutathione by modulating Akt phosphorylation in PC12 cells

SIRT2 plays important roles in multiple biological processes. It is unclear whether SIRT2 affects antioxidant capacity by modulating Nrf2, a key transcription factor for multiple antioxidant genes. By studying NADH-treated differentiated PC12 cells, we found that NADH induced a significant increase in the nuclear Nrf2, which was prevented by both SIRT2 siRNA and SIRT2 inhibitor, AGK2. SIRT2 siRNA also blocked the NADH-induced increases in glutamate cysteine ligase (GCL) and glutathione. Moreover, SIRT2 siRNA and AGK2 blocked NADH-induced Akt phosphorylation, and inhibition of Akt phosphorylation prevented NADH-induced increases in the nuclear Nrf2 and glutathione. Collectively, our study shows that SIRT2 regulates nuclear Nrf2 levels by modulating Akt phosphorylation, thus modulating the levels of GCL and total glutathione.

Histone deacetylase inhibitors for the treatment of cancer stem cells

HDAC inhibitors are a promising group of epigenetic drugs that show the ability to induce apoptosis in cancer stem cells.

The expression levels of the sirtuins in patients with BCC

Basal cell carcinoma (BCC) is the most common tumor in humans. Reduced expression of sirtuins interferes with DNA repair, which may cause mutations and genomic instability, and eventually leads to tumor development. In the present study, we investigate the expression levels of SIRT genes in non-tumoral and tumor tissues of patients with BCC. A total of 27 patients (16 males, 11 females) with BCC were included in the study; the mean age was 65.40 ± 10.74 years and mean follow-up was 2.5 ± 0.5 years. There were multiple synchronous lesions in six patients, and the remaining 21 patients had a single lesion. Tumor and non-tumoral tissue samples were collected from all patients, and mRNA expression levels of SIRT1-7 (Sirt1.1, Sirt1.2, Sirt2, Sirt3, Sirt4, Sirt5, Sirt6, and Sirt7) were examined by real-time PCR. The results showed that expressions of SIRT1.1, SIRT1.2, SIRT4, SIRT5, SIRT6, and SIRT7 mRNAs were unchanged in tumor tissues of BCC patients compared with non-tumoral tissue samples. Importantly, the expressions of SIRT2 and SIRT3 mRNAs were significantly reduced in tumor tissue samples from BCC patients compared with non-tumoral tissues (P = 0.02 and P = 0.03, respectively). In light of the previous reports that have demonstrated a link between SIRT proteins and cancer, our findings suggest that SIRT2 and SIRT3 may plan important roles in BCC pathogenesis and could be candidate prognostic biomarkers for BCC.

Gene expression mapping of histone deacetylases and co-factors, and correlation with survival time and 1H-HRMAS metabolomic profile in human gliomas

Primary brain tumors are presently classified based on imaging and histopathological techniques, which remains unsatisfaying. We profiled here by quantitative real time PCR (qRT-PCR) the transcripts of eighteen histone deacetylases (HDACs) and a subset of transcriptional co-factors in non-tumoral brain samples from 15 patients operated for epilepsia and in brain tumor samples from 50 patients diagnosed with grade II oligodendrogliomas (ODII, n = 9), grade III oligodendrogliomas (ODIII, n = 22) and glioblastomas (GL, n = 19). Co-factor transcripts were significantly different in tumors as compared to non-tumoral samples and distinguished different molecular subgroups of brain tumors, regardless of tumor grade. Among all patients studied, the expression of HDAC1 and HDAC3 was inversely correlated with survival, whereas the expression of HDAC4, HDAC5, HDAC6, HDAC11 and SIRT1 was significantly and positively correlated with survival time of patients with gliomas. ¹H-HRMAS technology revealed metabolomically distinct groups according to the expression of HDAC1, HDAC4 and SIRT1, suggesting that these genes may play an important role in regulating brain tumorigenesis and cancer progression. Our study hence identified different molecular fingerprints for subgroups of histopathologically similar brain tumors that may enable the prediction of outcome based on the expression level of co-factor genes and could allow customization of treatment.

Dysfunctional high-density lipoproteins in children with chronic kidney disease

OBJECTIVES

Our aim was to determine if chronic kidney disease (CKD) occurring in childhood impairs the normally vasoprotective functions of high-density lipoproteins (HDLs).

MATERIALS AND METHODS

HDLs were isolated from children with end-stage renal disease on dialysis (ESRD), children with moderate CKD and controls with normal kidney function. Macrophage response to HDLs was studied as expression of inflammatory markers (MCP-1, TNF-α, IL-1β) and chemotaxis. Human umbilical vein endothelial cells were used for expression of adhesion molecules (ICAM-1, VCAM-1, E-selectin) and adhesion. Cellular proliferation, apoptosis, and necrosis of endothelial cells were measured by MTS/PMS reagent-based assay, flow cytometry, and ELISA. Cholesterol efflux was assessed by gas chromatographic measurements of cholesterol in macrophages exposed to HDLs.

RESULTS

Compared with HDL(Control), HDL(CKD) and HDL(ESRD) heightened the cytokine response and disrupted macrophage chemotaxis. HDL(Control) reduced endothelial expression of ICAM-1, VCAM-1, E-selectin, whereas HDL(CKD) and HDL(ESRD) were less effective and showed reduced capacity to protect endothelial cells against monocyte adhesion. Compared with a dramatically enhanced endothelial proliferation following injurious stimulus by HDL(Control), neither HDL(CKD) nor HDL(ESRD) caused proliferative effects. HDLs of all three groups were equally protective against apoptosis assessed by flow cytometry and cleaved caspase-3 activity. Compared to HDL(Control), HDL(CKD) and HDL(ESRD) trended toward reduced capacity as cholesterol acceptors.

CONCLUSION

CKD in children impairs HDL function. Even in the absence of long-standing and concomitant risk factors, CKD alters specific HDL functions linked to control of inflammation and endothelial responses.

[SIRT2, a multi-talented deacetylase]

Sirtuin 2 (SIRT2) is an NAD(+) (nicotinamide adenine dinucleotide)-dependent deacetylase. Studies of this protein have often been divergent, highlighting the dependence of pleiotropic effects of SIRT2 on cellular context. The natural polyphenol resveratrol is known to exert opposite actions on neural cells according to their normal or cancerous status. We have recently shown the involvement of SIRT2 in the antiproliferative effects of resveratrol on primary cultures of human glioblastoma stem cells. SIRT2 could become a new therapeutic target.