Inhibition of TFEB oligomerization by co-treatment of melatonin with vorinostat promotes the therapeutic sensitivity in glioblastoma and glioma stem cells

Melatonin-vorinostat hybrid ligands show higher histone deacetylase and cancer cell growth inhibition than vorinostat

Anticancer drug conjugates are an emerging approach for future cancer treatment. Here, we report a series of hybrid ligands merging the neurohormone melatonin with the approved histone deacetylase (HDAC) inhibitor vorinostat, using melatonin's amide side chain (3a-e), its indolic nitrogen (5a-d), and its ether oxygen (7a-d) as attachment points. Several hybrid ligands showed higher potency thanvorinostat in both HDAC inhibition and cellular assays on different cultured cancer cell lines. In the most potent HDAC1 and HDAC6 inhibitors, 3e, 5c, and 7c, the hydroxamic acid moiety of vorinostat is linked to melatonin through a hexamethylene spacer. Hybrid ligands 5c and 7c were also found to be potent growth inhibitors of MCF-7, PC-3M-Luc, and HL-60 cancer cell lines. As these compounds showed only weak agonist activity at melatonin MT1 receptors, the findings indicate that their anticancer actions are driven by HDAC inhibition.

EGR1 drives cell proliferation by directly stimulating TFEB transcription in response to starvation

The stress-responsive transcription factor EB (TFEB) is a master controller of lysosomal biogenesis and autophagy and plays a major role in several cancer-associated diseases. TFEB is regulated at the posttranslational level by the nutrient-sensitive kinase complex mTORC1. However, little is known about the regulation of TFEB transcription. Here, through integrative genomic approaches, we identify the immediate-early gene EGR1 as a positive transcriptional regulator of TFEB expression in human cells and demonstrate that, in the absence of EGR1, TFEB-mediated transcriptional response to starvation is impaired. Remarkably, both genetic and pharmacological inhibition of EGR1, using the MEK1/2 inhibitor Trametinib, significantly reduced the proliferation of 2D and 3D cultures of cells displaying constitutive activation of TFEB, including those from a patient with Birt-Hogg-Dubé (BHD) syndrome, a TFEB-driven inherited cancer condition. Overall, we uncover an additional layer of TFEB regulation consisting in modulating its transcription via EGR1 and propose that interfering with the EGR1-TFEB axis may represent a therapeutic strategy to counteract constitutive TFEB activation in cancer-associated conditions.

ZBTB7A suppresses glioblastoma tumorigenesis through the transcriptional repression of EPB41L5

Glioblastoma multiforme (GBM), the most aggressive and malignant glioma, has a poor prognosis. Although patients with GBM are treated with surgery, chemotherapy, and radiation therapy, GBM is highly resistant to treatment, making it difficult and expensive to treat. In this study, we analyzed the Gene Expression Profiling Interactive Analysis dataset, the Cancer Genome Atlas dataset, and Gene Expression Omnibus array data. ZBTB7A (also called FBI1/POKEMON/LRF) was found to be highly expressed in low-grade glioma but significantly downregulated in patients with GBM. ZBTB7A is a transcription factor that plays an important role in many developmental stages, including cell proliferation. The activation of epithelial-mesenchymal transition (EMT) is a key process in cancer progression and metastasis. Erythrocyte membrane protein band 4.1 like 5 (EPB41L5) is an essential protein for EMT progression and metastasis in various types of cancer. We found that ZBTB7A depletion in U87 cells induced GBM progression and metastasis. Based on RNA sequencing data, ZBTB7A directly binds to the promoter of the EPB41L5 gene, reducing its expression and inhibiting GBM progression. We demonstrated that ZBTB7A dramatically inhibits GBM tumor growth through transcriptional repression of EPB41L5. Thus, both ZBTB7A and EPB41L5 may be potential biomarkers and novel therapeutic targets for GBM treatment. Overall, we discovered the role of a novel tumor suppressor that directly inhibits GBM progression (ZBTB7A) and identified EPB41L5 as a therapeutic target protein for patients with GBM.

Graphene oxide induced dynamic changes of autophagy-lysosome pathway and cell apoptosis via TFEB dysregulation in F98 cells

The extensive application of graphene oxide (GO) nanomaterials increases the risk of their release into the environment, thus posing a threat to the human body. Multiple studies indicate that GO could lead to neurotoxicity, while the intricate biological effects of GO in astrocytes remain unclear. The autophagic disorder was considered an important part of the exposure risk of GO in the application of neuromedicine. This study explored the key regulators mediating the autophagic process in rat astroglioma-derived F98 cells caused by GO, especially the dynamic changes in the cellular physiological state over time. We identified transcription factor EB (TFEB), a critical regulator of the autophagy-lysosome pathway (ALP), as a crucial factor in GO-induced autophagy flux blockade and cell apoptosis. Specifically, the prolonged exposure to GO increased the amount of its cellular internalization, which gradually prevented TFEB from entering the nucleus, thereby leading to the subsequent ALP dysfunction and excessive cell apoptosis. Furthermore, STIP1 homology and U-Box containing protein 1 (STUB1), an E3 ubiquitin ligase, was responsible for GO-triggered TFEB dysregulation, and overexpression of STUB1 helped alleviate GO cytotoxicity. Our study highlights that impaired TFEB activity underlies compromised autophagy flux in GO-induced apoptosis and opens up new avenues for the application of GO-based nanotherapeutics with specific autophagy-regulating properties in the central nervous system.

Small Molecule Inhibitors in Adult High-Grade Glioma: From the Past to the Future

Glioblastoma is the most common primary malignant tumor in the brain and has a dismal prognosis despite patients accepting standard therapies. Alternation of genes and deregulation of proteins, such as receptor tyrosine kinase, PI3K/Akt, PKC, Ras/Raf/MEK, histone deacetylases, poly (ADP-ribose) polymerase (PARP), CDK4/6, branched-chain amino acid transaminase 1 (BCAT1), and Isocitrate dehydrogenase (IDH), play pivotal roles in the pathogenesis and progression of glioma. Simultaneously, the abnormalities change the cellular biological behavior and microenvironment of tumor cells. The differences between tumor cells and normal tissue become the vulnerability of tumor, which can be taken advantage of using targeted therapies. Small molecule inhibitors, as an important part of modern treatment for cancers, have shown significant efficacy in hematologic cancers and some solid tumors. To date, in glioblastoma, there have been more than 200 clinical trials completed or ongoing in which trial designers used small molecules as monotherapy or combination regimens to correct the abnormalities. In this review, we summarize the dysfunctional molecular mechanisms and highlight the outcomes of relevant clinical trials associated with small-molecule targeted therapies. Based on the outcomes, the main findings were that small-molecule inhibitors did not bring more benefit to newly diagnosed glioblastoma, but the clinical studies involving progressive glioblastoma usually claimed “noninferiority” compared with historical results. However, as to the clinical inferiority trial, similar dosing regimens should be avoided in future clinical trials.

miR-3189-targeted GLUT3 repression by HDAC2 knockdown inhibits glioblastoma tumorigenesis through regulating glucose metabolism and proliferation

BACKGROUND

Epigenetic regulations frequently appear in Glioblastoma (GBM) and are highly associated with metabolic alterations. Especially, Histone deacetylases (HDACs) correlates with the regulation of tumorigenesis and cell metabolism in GBM progression, and HDAC inhibitors report to have therapeutic efficacy in GBM and other neurological diseases; however, GBM prevention and therapy by HDAC inhibition lacks a mechanism in the focus of metabolic reprogramming.

METHODS

HDAC2 highly express in GBM and is analyzed in TCGA/GEPIA databases. Therefore, HDAC2 knockdown affects GBM cell death. Analysis of RNA sequencing and qRT-PCR reveals that miR-3189 increases and GLUT3 decreases by HDAC2 knockdown. GBM tumorigenesis also examines by using in vivo orthotopic xenograft tumor models. The metabolism change in HDAC2 knockdown GBM cells measures by glucose uptake, lactate production, and OCR/ECAR analysis, indicating that HDAC2 knockdown induces GBM cell death by inhibiting GLUT3.

RESULTS

Notably, GLUT3 was suppressed by increasing miR-3189, demonstrating that miR-3189-mediated GLUT3 inhibition shows an anti-tumorigenic effect and cell death by regulating glucose metabolism in HDAC2 knockdown GBM.

CONCLUSIONS

Our findings will demonstrate the central role of HDAC2 in GBM tumorigenesis through the reprogramming of glucose metabolism by controlling miR-3189-inhibited GLUT3 expression, providing a potential new therapeutic strategy for GBM treatment.

Lysosomes at the Crossroads of Cell Metabolism, Cell Cycle, and Stemness

Initially described as lytic bodies due to their degradative and recycling functions, lysosomes play a critical role in metabolic adaptation to nutrient availability. More recently, the contribution of lysosomal proteins to cell signaling has been established, and lysosomes have emerged as signaling hubs that regulate diverse cellular processes, including cell proliferation and cell fate. Deciphering these signaling pathways has revealed an extensive crosstalk between the lysosomal and cell cycle machineries that is only beginning to be understood. Recent studies also indicate that a number of lysosomal proteins are involved in the regulation of embryonic and adult stem cell fate and identity. In this review, we will focus on the role of the lysosome as a signaling platform with an emphasis on its function in integrating nutrient sensing with proliferation and cell cycle progression, as well as in stemness-related features, such as self-renewal and quiescence.

The Role and Regulatory Mechanism of Transcription Factor EB in Health and Diseases

Transcription factor EB (TFEB) is a member of the microphthalmia-associated transcription factor/transcription factor E (MiTF/TFE) family and critically involved in the maintenance of structural integrity and functional balance of multiple cells. In this review, we described the effects of post-transcriptional modifications, including phosphorylation, acetylation, SUMOylation, and ubiquitination, on the subcellular localization and activation of TFEB. The activated TFEB enters into the nucleus and induces the expressions of targeted genes. We then presented the role of TFEB in the biosynthesis of multiple organelles, completion of lysosome-autophagy pathway, metabolism regulation, immune, and inflammatory responses. This review compiles existing knowledge in the understanding of TFEB regulation and function, covering its essential role in response to cellular stress. We further elaborated the involvement of TFEB dysregulation in the pathophysiological process of various diseases, such as the catabolic hyperactivity in tumors, the accumulation of abnormal aggregates in neurodegenerative diseases, and the aberrant host responses in inflammatory diseases. In this review, multiple drugs have also been introduced, which enable regulating the translocation and activation of TFEB, showing beneficial effects in mitigating various disease models. Therefore, TFEB might serve as a potential therapeutic target for human diseases. The limitation of this review is that the mechanism of TFEB-related human diseases mainly focuses on its association with lysosome and autophagy, which needs deep description of other mechanism in diseases progression after getting more advanced information.

Epigenetic modulators for brain cancer stem cells: Implications for anticancer treatment

Primary malignant brain tumors are a major cause of morbidity and mortality in both adults and children, with a dismal prognosis despite multimodal therapeutic approaches. In the last years, a specific subpopulation of cells within the tumor bulk, named cancer stem cells (CSCs) or tumor-initiating cells, have been identified in brain tumors as responsible for cancer growth and disease progression. Stemness features of tumor cells strongly affect treatment response, leading to the escape from conventional therapeutic approaches and subsequently causing tumor relapse. Recent research efforts have focused at identifying new therapeutic strategies capable of specifically targeting CSCs in cancers by taking into consideration their complex nature. Aberrant epigenetic machinery plays a key role in the genesis and progression of brain tumors as well as inducing CSC reprogramming and preserving CSC characteristics. Thus, reverting the cancer epigenome can be considered a promising therapeutic strategy. Three main epigenetic mechanisms have been described: DNA methylation, histone modifications, and non-coding RNA, particularly microRNAs. Each of these mechanisms has been proven to be targetable by chemical compounds, known as epigenetic-based drugs or epidrugs, that specifically target epigenetic marks. We review here recent advances in the study of epigenetic modulators promoting and sustaining brain tumor stem-like cells. We focus on their potential role in cancer therapy.

Melatonin in Cancer Treatment: Current Knowledge and Future Opportunities

Melatonin is a pleotropic molecule with numerous biological activities. Epidemiological and experimental studies have documented that melatonin could inhibit different types of cancer in vitro and in vivo. Results showed the involvement of melatonin in different anticancer mechanisms including apoptosis induction, cell proliferation inhibition, reduction in tumor growth and metastases, reduction in the side effects associated with chemotherapy and radiotherapy, decreasing drug resistance in cancer therapy, and augmentation of the therapeutic effects of conventional anticancer therapies. Clinical trials revealed that melatonin is an effective adjuvant drug to all conventional therapies. This review summarized melatonin biosynthesis, availability from natural sources, metabolism, bioavailability, anticancer mechanisms of melatonin, its use in clinical trials, and pharmaceutical formulation. Studies discussed in this review will provide a solid foundation for researchers and physicians to design and develop new therapies to treat and prevent cancer using melatonin.

Role of glioblastoma stem cells in cancer therapeutic resistance: a perspective on antineoplastic agents from natural sources and chemical derivatives

Glioblastoma (GBM) is the highest-grade form of glioma, as well as one of the most aggressive types of cancer, exhibiting rapid cellular growth and highly invasive behavior. Despite significant advances in diagnosis and therapy in recent decades, the outcomes for high-grade gliomas (WHO grades III-IV) remain unfavorable, with a median overall survival time of 15–18 months. The concept of cancer stem cells (CSCs) has emerged and provided new insight into GBM resistance and management. CSCs can self-renew and initiate tumor growth and are also responsible for tumor cell heterogeneity and the induction of systemic immunosuppression. The idea that GBM resistance could be dependent on innate differences in the sensitivity of clonogenic glial stem cells (GSCs) to chemotherapeutic drugs/radiation prompted the scientific community to rethink the understanding of GBM growth and therapies directed at eliminating these cells or modulating their stemness. This review aims to describe major intrinsic and extrinsic mechanisms that mediate chemoradioresistant GSCs and therapies based on antineoplastic agents from natural sources, derivatives, and synthetics used alone or in synergistic combination with conventional treatment. We will also address ongoing clinical trials focused on these promising targets. Although the development of effective therapy for GBM remains a major challenge in molecular oncology, GSC knowledge can offer new directions for a promising future.

TFEB Promotes Prostate Cancer Progression via Regulating ABCA2-Dependent Lysosomal Biogenesis

Transcription factor EB (TFEB), a member of the MiT family, is dysregulated in different cancers and exerts specific biological functions within the tumor microenvironment. Downregulation of TFEB induces macrophage polarization in the TME and promotes tumor progression. However, the biological role and clinical significance of TFEB in prostate cancer (PCa) remain unknown. This study aimed to identify the role of TFEB in PCa and its potential clinical value. We explored TFEB expression in PCa using public databases and verified its prognostic value using immunohistochemistry in PCa tissue samples. The results revealed that TFEB expression was up-regulated in PCa tissues and was associated with cancer metastasis. Next, overexpression of TFEB promoted PCa cell malignant behavior in in vivo and in vitro experiments. RNA-sequencing and bioinformatics analysis showed high expression of TFEB promoted lysosomal biogenesis and knockdown of TFEB expression decreased the number of lysosomes. Furthermore, the ATP-binding cassette transporter A2 (ABCA2) was identified as a target gene of TFEB, which was verified using the cleavage under targets and release using nuclease (CUT&RUN) assay and qRT-PCR. Silencing of ABCA2 reduced lysosomal biogenesis and decreased matrix metalloproteinases expression, which reduced PCa cell invasion and migration in the tumor microenvironment. Our study suggests that TFEB promotes PCa progression by regulating ABCA2 through lysosomal biogenesis and may serve as a prognostic factor or as a potential therapeutic target of PCa.

The Effect of Melatonin Modulation of Non-coding RNAs on Central Nervous System Disorders: An Updated Review

Melatonin is a hormone produced in and secreted by the pineal gland. Besides its role in regulating circadian rhythms, melatonin has a wide range of protective functions in the central nervous system (CNS) disorders. The mechanisms underlying this protective function are associated with the regulatory effects of melatonin on related genes and proteins. In addition to messenger ribonucleic acid (RNA) that can be translated into protein, an increasing number of non-coding RNAs in the human body are proven to participate in many diseases. This review discusses the current progress of research on the effects of melatonin modulation of non-coding RNAs (ncRNAs), including microRNA, long ncRNA, and circular RNA. The role of melatonin in regulating common pathological mechanisms through these ncRNAs is also summarized. Furthermore, the ncRNAs, currently shown to be involved in melatonin signaling in CNS diseases, are discussed. The information compiled in this review will open new avenues for future research into melatonin mechanisms and provide a further understanding of ncRNAs in the CNS.

Melatonin and gastrointestinal cancers: Current evidence based on underlying signaling pathways

Gastrointestinal (GI) cancers, leading causes of cancer-related deaths, have been serious challenging human diseases up to now. Because of high rates of mortality, late-stage diagnosis, metastasis to distant locations, and low effectiveness and adverse events of routine standard therapies, the quality of life and survival time are low in patients with GI cancers. Hence, many efforts need to be done to explore and find novel efficient treatments. Beneficial effects of melatonin have been reported in a wide variety of human diseases. Melatonin has antioxidant, anti-inflammatory, antimicrobial, and anticancer effects. Various studies have showed the regulatory effects of melatonin on apoptotsis, autophagy and angiogenesis; these properties result in the inhibition of invasion, migration, and proliferation of GI cancer cells in vivo and in vitro. Together, this review suggests that melatonin in combination with anticancer agents may improve the efficacy of routine medicine and survival rate of patients with cancer.

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.

Melatonin inhibits Warburg-dependent cancer by redirecting glucose oxidation to the mitochondria: a mechanistic hypothesis

Melatonin has the ability to intervene in the initiation, progression and metastasis of some experimental cancers. A large variety of potential mechanisms have been advanced to describe the metabolic and molecular events associated with melatonin's interactions with cancer cells. There is one metabolic perturbation that is common to a large number of solid tumors and accounts for the ability of cancer cells to actively proliferate, avoid apoptosis, and readily metastasize, i.e., they use cytosolic aerobic glycolysis (the Warburg effect) to rapidly generate the necessary ATP required for the high metabolic demands of the cancer cells. There are several drugs, referred to as glycolytic agents, that cause cancer cells to abandon aerobic glycolysis and shift to the more conventional mitochondrial oxidative phosphorylation for ATP synthesis as in normal cells. In doing so, glycolytic agents also inhibit cancer growth. Herein, we hypothesize that melatonin also functions as an inhibitor of cytosolic glycolysis in cancer cells using mechanisms, i.e., downregulation of the enzyme (pyruvate dehydrogenase kinase) that interferes with the conversion of pyruvate to acetyl CoA in the mitochondria, as do other glycolytic drugs. In doing so, melatonin halts the proliferative activity of cancer cells, reduces their metastatic potential and causes them to more readily undergo apoptosis. This hypothesis is discussed in relation to the previously published reports. Whereas melatonin is synthesized in the mitochondria of normal cells, we hypothesize that this synthetic capability is not present in cancer cell mitochondria because of the depressed acetyl CoA; acetyl CoA is necessary for the rate limiting enzyme in melatonin synthesis, arylalkylamine-N-acetyltransferase. Finally, the ability of melatonin to switch glucose oxidation from the cytosol to the mitochondria also explains how tumors that become resistant to conventional chemotherapies are re-sensitized to the same treatment when melatonin is applied.

Glioblastoma chemoresistance: roles of the mitochondrial melatonergic pathway

Treatment-resistance is common in glioblastoma (GBM) and the glioblastoma stem-like cells (GSC) from which they arise. Current treatment options are generally regarded as very poor and this arises from a poor conceptualization of the biological underpinnings of GBM/GSC and of the plasticity that these cells are capable of utilizing in response to different treatments. A number of studies indicate melatonin to have utility in the management of GBM/GSC, both per se and when adjunctive to chemotherapy. Recent work shows melatonin to be produced in mitochondria, with the mitochondrial melatonergic pathway proposed to be a crucial factor in driving the wide array of changes in intra- and inter-cellular processes, as well as receptors that can be evident in the cells of the GBM/GSC microenvironment. Variations in the enzymatic conversion of N-acetylserotonin (NAS) to melatonin may be especially important in GSC, as NAS can activate the tyrosine receptor kinase B to increase GSC survival and proliferation. Consequently, variations in the NAS/melatonin ratio may have contrasting effects on GBM/GSC survival. It is proposed that mitochondrial communication across cell types in the tumour microenvironment is strongly driven by the need to carefully control the mitochondrial melatonergic pathways across cell types, with a number of intra- and inter-cellular processes occurring as a consequence of the need to carefully regulate the NAS/melatonin ratio. This better integrates previously disparate data on GBM/GSC as well as providing clear future research and treatment options.

Role and Therapeutic Potential of Melatonin in the Central Nervous System and Cancers

Melatonin (MLT) is a powerful chronobiotic hormone that controls a multitude of circadian rhythms at several levels and, in recent times, has garnered considerable attention both from academia and industry. In several studies, MLT has been discussed as a potent neuroprotectant, anti-apoptotic, anti-inflammatory, and antioxidative agent with no serious undesired side effects. These characteristics raise hopes that it could be used in humans for central nervous system (CNS)-related disorders. MLT is mainly secreted in the mammalian pineal gland during the dark phase, and it is associated with circadian rhythms. However, the production of MLT is not only restricted to the pineal gland; it also occurs in the retina, Harderian glands, gut, ovary, testes, bone marrow, and lens. Although most studies are limited to investigating the role of MLT in the CNS and related disorders, we explored a considerable amount of the existing literature. The objectives of this comprehensive review were to evaluate the impact of MLT on the CNS from the published literature, specifically to address the biological functions and potential mechanism of action of MLT in the CNS. We document the effectiveness of MLT in various animal models of brain injury and its curative effects in humans. Furthermore, this review discusses the synthesis, biology, function, and role of MLT in brain damage, and as a neuroprotective, antioxidative, anti-inflammatory, and anticancer agent through a collection of experimental evidence. Finally, it focuses on the effect of MLT on several neurological diseases, particularly CNS-related injuries.

Exendin-4 attenuates inflammation-mediated endothelial cell apoptosis in varicose veins through inhibiting the MAPK-JNK signaling pathway

Context: Inflammation response has been found to be associated with endothelial cell death in the progression of varicose veins. Exendin-4 is able to reduce inflammation and thus attenuate cell apoptosis.Aim: The aim of our study is to explore the influence of Exendin-4 on LPS-treated endothelial cells.Methods: Cells were treated with LPS. Exendin-4 was added into the medium of cells. Western blots, qPCR, and ELISA were used to analyze the role of Exendin-4 in LPS-mediated cell death.Results: We found that LPS treatment caused significantly cell death. Whereas this trend could be attenuated by Exendin-4. After treatment with Exendin-4, inflammation factors upregulation and oxidative stress activation were significantly repressed, an effect that was followed by a drop in the levels of glucose production and lactic acid generation. At the molecular levels, Exendin-4 treatment inhibited the activity of MAPK-JNK signaling pathway in the presence of LPS treatment.Conclusions: LPS causes cell apoptosis through inducing inflammation response, oxidative stress and energy stress. Exendin-4 treatment enhances cell survival, reduces inflammation, and improves energy stress through inhibiting the MAPK-JNK signaling pathway.

Targeting cancer stem cells by melatonin: Effective therapy for cancer treatment

Melatonin is a physiological hormone produced by the pineal gland. In recent decades, enormous investigations showed that melatonin can prompt apoptosis in cancer cells and inhibit tumor metastasis and angiogenesis in variety of malignancies such as ovarian, melanoma, colon, and breast cancer; therefore, its possible therapeutic usage in cancer treatment was confirmed. CSCs, which has received much attention from researchers in past decades, are major challenges in the treatment of cancer. Because CSCs are resistant to chemotherapeutic drugs and cause recurrence of cancer and also have the ability to be regenerated; they can cause serious problems in the treatment of various cancers. For these reasons, the researchers are trying to find a solution to destroy these cells within the tumor mass. In recent years, the effect of melatonin on CSCs has been investigated in some cancers. Given the importance of CSCs in the process of cancer treatment, this article reviewed the studies conducted on the effect of melatonin on CSCs as a solution to the problems caused by CSCs in the treatment of various cancers.

Melatonin's Antineoplastic Potential Against Glioblastoma

Glioblastoma (GBM) is one of the most intransigent and aggressive brain tumors, and its treatment is extremely challenging and ineffective. To improve patients’ expectancy and quality of life, new therapeutic approaches were investigated. Melatonin is an endogenous indoleamine with an incredible variety of properties. Due to evidence demonstrating melatonin’s activity against several cancer hallmarks, there is growing interest in its use for preventing and treating cancer. In this review, we report on the potential effects of melatonin, alone or in combination with anticancer drugs, against GBM. We also summarize melatonin targets and/or the intracellular pathways involved. Moreover, we describe melatonin’s epigenetic activity responsible for its antineoplastic effects. To date, there are too few clinical studies (involving a small number of patients) investigating the antineoplastic effects of melatonin against GBM. Nevertheless, these studies described improvement of GBM patients’ quality of life and did not show significant adverse effects. In this review, we also report on studies regarding melatonin-like molecules with the tumor-suppressive properties of melatonin together with implemented pharmacokinetics. Melatonin effects and mechanisms of action against GBM require more research attention due to the unquestionably high potential of this multitasking indoleamine in clinical practice.

Sphingosine kinase 1 promotes cerebral ischemia-reperfusion injury through inducing ER stress and activating the NF-κB signaling pathway

Endoplasm reticulum stress and inflammation response have been found to be linked to cerebral ischemia-reperfusion (IR) injury. Sphingosine kinase 1 (SPHK1) has been reported to be a novel endoplasm reticulum regulator. The aim of our study is to figure out the role of SPHK1 in cerebral IR injury and verify whether it has an ability to regulate inflammation and endoplasm reticulum stress. Hydrogen peroxide was used to induce cerebral IR injury. Enzyme-linked immunosorbent assay, quantitative polymerase chain reaction, western blots, and immunofluorescence were used to measure the alterations of cell viability, inflammation response, and endoplasm reticulum stress. The results demonstrated that after exposure to hydrogen peroxide, cell viability was reduced whereas SPHK1 expression was significantly elevated. Knockdown of SPHK1 attenuated hydrogen peroxide-mediated cell death and reversed cell viability. Our data also demonstrated that SPHK1 deletion reduced endoplasm reticulum stress and alleviated inflammation response in hydrogen peroxide-treated cells. In addition, we also found that SHPK1 modulated endoplasm reticulum stress and inflammation response to through the NF-κB signaling pathway. Inhibition of NF-κB signaling pathway has similar results when compared with the cells with SPHK1 deletion. Altogether, our results demonstrated that SPHK1 upregulation, induced by hydrogen peroxide, is responsible for cerebral IR injury through inducing endoplasm reticulum stress and inflammation response in a manner working through the NF-κB signaling pathway. This finding provides new insight into the molecular mechanism to explain the neuron death induced by cerebral IR injury.

Antioxidants and Neuron-Astrocyte Interplay in Brain Physiology: Melatonin, a Neighbor to Rely on

This manuscript is a review focused onto the role of astrocytes in the protection of neurons against oxidative stress and how melatonin can contribute to the maintenance of brain homeostasis. The first part of the review is dedicated to the dependence of neurons on astrocytes by terms of survival under oxidative stress conditions. Additionally, the effects of melatonin against oxidative stress in the brain and its putative role in the protection against diseases affecting the brain are highlighted. The effects of melatonin on the physiology of neurons and astrocytes also are reviewed.

The effects of melatonin on signaling pathways and molecules involved in glioma

Glioblastoma is one of the most common brain tumors with high invasion and malignancy. Despite extensive research in this area and the use of new and advanced therapies, the survival rate in this disease is very low. In addition, resistance to treatment has also been observed in this disease. One of the reasons for rapid progression and failure in treatment for this disease is the presence of a class of cells with high proliferation and high differentiation, a class called glioblastoma stem-like cells shown as being the source of glioblastoma tumors. It has been reported that several oncogenes are expressed in this disease. One important issue in recognizing the pathogenesis of this disease, and which could improve the treatment process, is the identification of involved oncogenes as well as molecules that affect the reduction of the expression of these oncogenes. Melatonin regulates the biological rhythm and inhibits the proliferation of malignant glioma cells due to antioxidant and anti-apoptotic effects. Melatonin has been considered in biological processes and in signaling pathways involved in the development of glioma. The aim of this review is to investigate the effects of melatonin on signaling pathways and molecules involved in the progression of glioma.