Riluzole enhances the antitumor effects of temozolomide via suppression of MGMT expression in glioblastoma

Current State of Melanoma Therapy and Next Steps: Battling Therapeutic Resistance

Melanoma is the most aggressive and deadly form of skin cancer due to its high propensity to metastasize to distant organs. Significant progress has been made in the last few decades in melanoma therapeutics, most notably in targeted therapy and immunotherapy. These approaches have greatly improved treatment response outcomes; however, they remain limited in their abilities to hinder disease progression due, in part, to the onset of acquired resistance. In parallel, intrinsic resistance to therapy remains an issue to be resolved. In this review, we summarize currently available therapeutic options for melanoma treatment and focus on possible mechanisms that drive therapeutic resistance. A better understanding of therapy resistance will provide improved rational strategies to overcome these obstacles.

The dark side of mRNA translation and the translation machinery in glioblastoma

Among the different types of cancer affecting the central nervous system (CNS), glioblastoma (GB) is classified by the World Health Organization (WHO) as the most common and aggressive CNS cancer in adults. GB incidence is more frequent among persons aged 45–55 years old. GB treatments are based on tumor resection, radiation, and chemotherapies. The current development of novel molecular biomarkers (MB) has led to a more accurate prediction of GB progression. Moreover, clinical, epidemiological, and experimental studies have established genetic variants consistently associated with the risk of suffering GB. However, despite the advances in these fields, the survival expectancy of GB patients is still shorter than 2 years. Thus, fundamental processes inducing tumor onset and progression remain to be elucidated. In recent years, mRNA translation has been in the spotlight, as its dysregulation is emerging as a key cause of GB. In particular, the initiation phase of translation is most involved in this process. Among the crucial events, the machinery performing this phase undergoes a reconfiguration under the hypoxic conditions in the tumor microenvironment. In addition, ribosomal proteins (RPs) have been reported to play translation-independent roles in GB development. This review focuses on the research elucidating the tight relationship between translation initiation, the translation machinery, and GB. We also summarize the state-of-the-art drugs targeting the translation machinery to improve patients’ survival. Overall, the recent advances in this field are shedding new light on the dark side of translation in GB.

Canagliflozin Inhibits Glioblastoma Growth and Proliferation by Activating AMPK

Sodium-glucose transporter 2 (SGLT2) inhibitors are antidiabetic drugs affecting SGLT2. Recent studies have shown various cancers expressing SGLT2, and SGLT2 inhibitors attenuating tumor proliferation. We evaluated the antitumor activities of canagliflozin, a SGLT2 inhibitor, on glioblastoma (GBM). Three GBM cell lines, U251MG (human), U87MG (human), and GL261 (murine), were used. We assessed the expression of SGLT2 of GBM through immunoblotting, specimen-use, cell viability assays, and glucose uptake assay with canagliflozin. Then, we assessed phosphorylation of AMP-activated protein kinase (AMPK), p70 S6 kinase, and S6 ribosomal protein by immunoblotting. Concentrations of 5, 10, 20, and 40 μM canagliflozin were used in these tests. We also evaluated cell viability and immunoblotting using U251MG with siRNA knockdown of SGLT2. Furthermore, we divided the mice into vehicle group and canagliflozin group. The canagliflozin group was administrated with 100 mg/kg of canagliflozin orally for 10 days starting from the third days post-GBM transplant. The brains were removed and the tumor volume was evaluated using sections. SGLT2 was expressed in GBM cell and GBM allograft mouse. Canagliflozin administration at 40 μM significantly inhibited cell proliferation and glucose uptake into the cell. Additionally, canagliflozin at 40 μM significantly increased the phosphorylation of AMPK and suppressed that of p70 S6 kinase and S6 ribosomal protein. Similar results of cell viability assays and immunoblotting were obtained using siRNA SGLT2. Furthermore, although less effective than in vitro, the canagliflozin group significantly suppressed tumor growth in GBM-transplanted mice. This suggests that canagliflozin can be used as a potential treatment for GBM.

Implications of a Neuronal Receptor Family, Metabotropic Glutamate Receptors, in Cancer Development and Progression

Cancer is the second leading cause of death, and incidences are increasing globally. Simply defined, cancer is the uncontrolled proliferation of a cell, and depending on the tissue of origin, the cancer etiology, biology, progression, prognosis, and treatment will differ. Carcinogenesis and its progression are associated with genetic factors that can either be inherited and/or acquired and are classified as an oncogene or tumor suppressor. Many of these genetic factors converge on common signaling pathway(s), such as the MAPK and PI3K/AKT pathways. In this review, we will focus on the metabotropic glutamate receptor (mGluR) family, an upstream protein that transmits extracellular signals into the cell and has been shown to regulate many aspects of tumor development and progression. We explore the involvement of members of this receptor family in various cancers that include breast cancer, colorectal cancer, glioma, kidney cancer, melanoma, oral cancer, osteosarcoma, pancreatic cancer, prostate cancer, and T-cell cancers. Intriguingly, depending on the member, mGluRs can either be classified as oncogenes or tumor suppressors, although in general most act as an oncogene. The extensive work done to elucidate the role of mGluRs in various cancers suggests that it might be a viable strategy to therapeutically target glutamatergic signaling.

Neurotransmitters: Potential Targets in Glioblastoma

Simple Summary

Aiming to discover potential treatments for GBM, this review connects emerging research on the roles of neurotransmitters in the normal neural and the GBM microenvironments and sheds light on the prospects of their application in the neuropharmacology of GBM. Conventional therapy is blamed for its poor effect, especially in inhibiting tumor recurrence and invasion. Facing this dilemma, we focus on neurotransmitters that modulate GBM initiation, progression and invasion, hoping to provide novel therapy targeting GBM. By analyzing research concerning GBM therapy systematically and scientifically, we discover increasing insights into the regulatory effects of neurotransmitters, some of which have already shown great potential in research in vivo or in vitro. After that, we further summarize the potential drugs in correlation with previously published research. In summary, it is worth expecting that targeting neurotransmitters could be a promising novel pharmacological approach for GBM treatment.

Abstract

For decades, glioblastoma multiforme (GBM), a type of the most lethal brain tumor, has remained a formidable challenge in terms of its treatment. Recently, many novel discoveries have underlined the regulatory roles of neurotransmitters in the microenvironment both physiologically and pathologically. By targeting the receptors synaptically or non-synaptically, neurotransmitters activate multiple signaling pathways. Significantly, many ligands acting on neurotransmitter receptors have shown great potential for inhibiting GBM growth and development, requiring further research. Here, we provide an overview of the most novel advances concerning the role of neurotransmitters in the normal neural and the GBM microenvironments, and discuss potential targeted drugs used for GBM treatment.

Recurrent Glioblastoma Treatment: State of the Art and Future Perspectives in the Precision Medicine Era

Current treatment guidelines for the management of recurrent glioblastoma (rGBM) are far from definitive, and the prognosis remains dismal. Despite recent advancements in the pharmacological and surgical fields, numerous doubts persist concerning the optimal strategy that clinicians should adopt for patients who fail the first lines of treatment and present signs of progressive disease. With most recurrences being located within the margins of the previously resected lesion, a comprehensive molecular and genetic profiling of rGBM revealed substantial differences compared with newly diagnosed disease. In the present comprehensive review, we sought to examine the current treatment guidelines and the new perspectives that polarize the field of neuro-oncology, strictly focusing on progressive disease. For this purpose, updated PRISMA guidelines were followed to search for pivotal studies and clinical trials published in the last five years. A total of 125 articles discussing locoregional management, radiotherapy, chemotherapy, and immunotherapy strategies were included in our analysis, and salient findings were critically summarized. In addition, an in-depth description of the molecular profile of rGBM and its distinctive characteristics is provided. Finally, we integrate the above-mentioned evidence with the current guidelines published by international societies, including AANS/CNS, EANO, AIOM, and NCCN.

Research progress of anti-glioma chemotherapeutic drugs (Review)

Glioma is the most common primary intracranial malignancy in the central nervous system. At present, the most important treatment option is surgical resection of the tumor combined with radiotherapy and chemotherapy. The principle of operation is to remove the tumor to the maximal extent on the basis of preserving brain function. However, prominent invasive and infiltrative proliferation of glioma tumor cells into the surrounding normal tissues frequently reduces the efficacy of treatment. This in turn worsens the prognosis, because the tumor cannot be completely removed, which can readily relapse. Chemotherapeutic agents when applied individually have demonstrated limited efficacy for the treatment of glioma. However, multiple different chemotherapeutic agents can be used in combination with other treatment modalities to improve the efficacy while circumventing systemic toxicity and drug resistance. Therefore, it is pivotal to unravel the inhibitory mechanism mediated by the different chemotherapeutic drugs on glioma cells in preclinical studies. The aim of the present review is to provide a summary for understanding the effects of different chemotherapeutic drugs in glioma, in addition to providing a reference for the preclinical research into novel chemotherapeutic agents for future clinical application.

Antitumor Effect of Traditional Drugs for Neurological Disorders: Preliminary Studies in Neural Tumor Cell Lines

Glioblastoma multiforme is the most common malignant primary brain tumor in adults. Despite new treatments developed including immunomodulation using vaccines and cell therapies, mortality remains high due to the resistance mechanisms presented by these tumor cells and the function of the blood-brain barrier that prevents the entry of most drugs. In this context of searching for new glioblastoma therapies, the study of the existing drugs to treat neurological disorder is gaining great relevance. The aim of this study was to determine, through a preliminary in vitro study on human glioblastoma (A172, LN229), anaplastic glioma (SF268) and neuroblastoma (SK-N-SH) cell lines, the possible antitumor activity of the active principles of several drugs (levomepromazine, haloperidol, lacosamide, valproic acid, levetiracetam, glatiramer acetate, fingolimod, biperiden and dextromethorphan) with the ability to cross the blood-brain barrier and that are commonly used in neurological disorders. Results showed that levetiracetam, valproic acid, and haloperidol were able to induce a relevant synergistic antitumor effect when associated with the chemotherapy currently used in clinic (temozolomide). Regarding the mechanism of action, haloperidol, valproic acid and levomepromazine caused cell death by apoptosis, while biperiden and dextromethorphan induced autophagy. Fingolimod appeared to have anoikis-related cell death. Thus, the assayed drugs which are able to cross the blood-brain barrier could represent a possibility to improve the treatment of neural tumors, though future in vivo studies and clinical trials will be necessary to validate it.

Endothelial cell-specific reduction of heparan sulfate suppresses glioma growth in mice

PURPOSE

Heparan sulfate (HS) is one of the factors that has been suggested to be associated with angiogenesis and invasion of glioblastoma (GBM), an aggressive and fast-growing brain tumor. However, it remains unclear how HS of endothelial cells is involved in angiogenesis in glioblastoma and its prognosis. Thus, we investigated the effect of endothelial cell HS on GBM development.

METHODS

We generated endothelial cell-specific knockout of Ext1, a gene encoding a glycosyltransferase and essential for HS synthesis, and murine GL261 glioblastoma cells were orthotopically transplanted. Two weeks after transplantation, we examined the tumor progression and underlying mechanisms.

RESULTS

The endothelial cell-specific Ext1 knockout (Ext1 CKO ) mice exhibited reduced HS expression specifically in the vascular endothelium of the brain capillaries compared with the control wild-type (WT) mice. GBM growth was significantly suppressed in Ext1 CKO mice compared with that in WT mice. After GBM transplantation, the survival rate was significantly higher in Ext1 CKO mice than in WT mice. We investigated how the effect of fibroblast growth factor 2 (FGF2), which is known as an angiogenesis-promoting factor, differs between Ext1 CKO and WT mice by using an in vivo Matrigel assay and demonstrated that endothelial cell-specific HS reduction attenuated the effect of FGF2 on angiogenesis.

CONCLUSIONS

HS reduction in the vascular endothelium of the brain suppressed GBM growth and neovascularization in mice.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12672-021-00444-3.

Riluzole: A neuroprotective drug with potential as a novel anti‑cancer agent (Review)

Riluzole, a glutamate release inhibitor, has been in use for the treatment of amyotrophic lateral sclerosis for over two decades since its approval by the Food and Drug Administration. Recently, riluzole has been evaluated in cancer cells and indicated to block cell proliferation and/or induce cell death. Riluzole has been proven effective as an anti-neoplastic drug in cancers of various tissue origins, including the skin, breast, pancreas, colon, liver, bone, brain, lung and nasopharynx. While cancer cells expressing glutamate receptors frequently respond to riluzole treatment, numerous types of cancer cell lacking glutamate receptors unexpectedly responded to riluzole treatment as well. Riluzole was demonstrated to interfere with glutamate secretion, growth signaling pathways, Ca²⁺ homeostasis, glutathione synthesis, reactive oxygen species generation and integrity of DNA, as well as autophagic and apoptotic pathways. Of note, riluzole is highly effective in inducing cell death in cisplatin-resistant lung cancer cells. Furthermore, riluzole pretreatment sensitizes glioma and melanoma to radiation therapy. In addition, in triple-negative breast cancer, colorectal cancer, melanoma and glioblastoma, riluzole has synergistic effects in combination with select drugs. In an effort to highlight the therapeutic potential of riluzole, the current study reviewed the effect and outcome of riluzole treatment on numerous cancer types investigated thus far. The mechanism of action and the various molecular pathways affected by riluzole are discussed.

Combined Therapy With Avastin, a PAF Receptor Antagonist and a Lipid Mediator Inhibited Glioblastoma Tumor Growth

Glioblastoma multiforme (GBM) is an aggressive, highly proliferative, invasive brain tumor with a poor prognosis and low survival rate. The current standard of care for GBM is chemotherapy combined with radiation following surgical intervention, altogether with limited efficacy, since survival averages 18 months. Improvement in treatment outcomes for patients with GBM requires a multifaceted approach due to the dysregulation of numerous signaling pathways. Recently emerging therapies to precisely modulate tumor angiogenesis, inflammation, and oxidative stress are gaining attention as potential options to combat GBM. Using a mouse model of GBM, this study aims to investigate Avastin (suppressor of vascular endothelial growth factor and anti-angiogenetic treatment), LAU-0901 (a platelet-activating factor receptor antagonist that blocks pro-inflammatory signaling), Elovanoid; ELV, a novel pro-homeostatic lipid mediator that protects neural cell integrity and their combination as an alternative treatment for GBM. Female athymic nude mice were anesthetized with ketamine/xylazine, and luciferase-modified U87MG tumor cells were stereotactically injected into the right striatum. On post-implantation day 13, mice received one of the following: LAU-0901, ELV, Avastin, and all three compounds in combination. Bioluminescent imaging (BLI) was performed on days 13, 20, and 30 post-implantation. Mice were perfused for ex vivo MRI on day 30. Bioluminescent intracranial tumor growth percentage was reduced by treatments with LAU-0901 (43%), Avastin (77%), or ELV (86%), individually, by day 30 compared to saline treatment. In combination, LAU-0901/Avastin, ELV/LAU-0901, or ELV/Avastin had a synergistic effect in decreasing tumor growth by 72, 92, and 96%, respectively. Additionally, tumor reduction was confirmed by MRI on day 30, which shows a decrease in tumor volume by treatments with LAU-0901 (37%), Avastin (67%), or ELV (81.5%), individually, by day 30 compared to saline treatment. In combination, LAU-0901/Avastin, ELV/LAU-0901, or ELV/Avastin had a synergistic effect in decreasing tumor growth by 69, 78.7, and 88.6%, respectively. We concluded that LAU-0901 and ELV combined with Avastin exert a better inhibitive effect in GBM progression than monotherapy. To our knowledge, this is the first study that demonstrates the efficacy of these novel therapeutic regimens in a model of GBM and may provide the basis for future therapeutics in GBM patients.

Ion Channels as Therapeutic Targets in High Grade Gliomas

Simple Summary

Glioblastoma multiforme is an aggressive grade IV lethal brain tumour with a median survival of 14 months. Despite surgery to remove the tumour, and subsequent concurrent chemotherapy and radiotherapy, there is little in terms of effective treatment options. Because of this, exploring new treatment avenues is vital. Brain tumours are intrinsically electrically active; expressing unique patterns of ion channels, and this is a characteristic we can exploit. Ion channels are specialised proteins in the cell’s membrane that allow for the passage of positive and negatively charged ions in and out of the cell, controlling membrane potential. Membrane potential is a crucial biophysical signal in normal and cancerous cells. Research has identified that specific classes of ion channels not only move the cell through its cell cycle, thus encouraging growth and proliferation, but may also be essential in the development of brain tumours. Inhibition of sodium, potassium, calcium, and chloride channels has been shown to reduce the capacity of glioblastoma cells to grow and invade. Therefore, we propose that targeting ion channels and repurposing commercially available ion channel inhibitors may hold the key to new therapeutic avenues in high grade gliomas.

Abstract

Glioblastoma multiforme (GBM) is a lethal brain cancer with an average survival of 14–15 months even with exhaustive treatment. High grade gliomas (HGG) represent the leading cause of CNS cancer-related death in children and adults due to the aggressive nature of the tumour and limited treatment options. The scarcity of treatment available for GBM has opened the field to new modalities such as electrotherapy. Previous studies have identified the clinical benefit of electrotherapy in combination with chemotherapeutics, however the mechanistic action is unclear. Increasing evidence indicates that not only are ion channels key in regulating electrical signaling and membrane potential of excitable cells, they perform a crucial role in the development and neoplastic progression of brain tumours. Unlike other tissue types, neural tissue is intrinsically electrically active and reliant on ion channels and their function. Ion channels are essential in cell cycle control, invasion and migration of cancer cells and therefore present as valuable therapeutic targets. This review aims to discuss the role that ion channels hold in gliomagenesis and whether we can target and exploit these channels to provide new therapeutic targets and whether ion channels hold the mechanistic key to the newfound success of electrotherapies.