Expression of glutamate receptor subunits in human cancers

A glutamatergic biomarker panel enables differentiating Grade 4 gliomas/astrocytomas from brain metastases

Background

The differentiation of high-grade glioma and brain tumors of an extracranial origin is eminent for the decision on subsequent treatment regimens. While in high-grade glioma, a surgical resection of the tumor mass is a fundamental part of current standard regimens, in brain metastasis, the burden of the primary tumor must be considered. However, without a cancer history, the differentiation remains challenging in the imaging. Hence, biopsies are common that may help to identify the tumor origin. An additional tool to support the differentiation may be of great help. For this purpose, we aimed to identify a biomarker panel based on the expression analysis of a small sample of tissue to support the pathological analysis of surgery resection specimens. Given that an aberrant glutamate signaling was identified to drive glioblastoma progression, we focused on glutamate receptors and key players of glutamate homeostasis.

Methods

Based on surgically resected samples from 55 brain tumors, the expression of ionotropic and metabotropic glutamate receptors and key players of glutamate homeostasis were analyzed by RT-PCR. Subsequently, a receiver operating characteristic (ROC) analysis was performed to identify genes whose expression levels may be associated with either glioblastoma or brain metastasis.

Results

Out of a total of 29 glutamatergic genes analyzed, nine genes presented a significantly different expression level between high-grade gliomas and brain metastases. Of those, seven were identified as potential biomarker candidates including genes encoding for AMPA receptors GRIA1, GRIA2, kainate receptors GRIK1 and GRIK4, metabotropic receptor GRM3, transaminase BCAT1 and the glutamine synthetase (encoded by GLUL). Overall, the biomarker panel achieved an accuracy of 88% (95% CI: 87.1, 90.8) in predicting the tumor entity. Gene expression data, however, could not discriminate between patients with seizures from those without.

Conclusion

We have identified a panel of seven genes whose expression may serve as a biomarker panel to discriminate glioblastomas and brain metastases at the molecular level. After further validation, our biomarker signatures could be of great use in the decision making on subsequent treatment regimens after diagnosis.

Cisplatin induces BDNF downregulation in middle-aged female rat model while BDNF enhancement attenuates cisplatin neurotoxicity

Cancer-related cognitive impairments (CRCI) are neurological complications associated with cancer treatment, and greatly affect cancer survivors' quality of life. Brain-derived neurotrophic factor (BDNF) plays an essential role in neurogenesis, learning and memory. The reduction of BDNF is associated with the decrease in cognitive function in various neurological disorders. Few pre-clinical studies have reported on the effects of chemotherapy and medical stress on BDNF levels and cognition. The present study aimed to compare the effects of medical stress and cisplatin on serum BDNF levels and cognitive function in 9-month-old female Sprague Dawley rats to age-matched controls. Serum BDNF levels were collected longitudinally during cisplatin treatment, and cognitive function was assessed by novel object recognition (NOR) 14 weeks post-cisplatin initiation. Terminal BDNF levels were collected 24 weeks after cisplatin initiation. In cultured hippocampal neurons, we screened three neuroprotective agents, riluzole (an approved treatment for amyotrophic lateral sclerosis), as well as the ampakines CX546 and CX1739. We assessed dendritic arborization by Sholl analysis and dendritic spine density by quantifying postsynaptic density-95 (PSD-95) puncta. Cisplatin and exposure to medical stress reduced serum BDNF levels and impaired object discrimination in NOR compared to age-matched controls. Pharmacological BDNF augmentation protected neurons against cisplatin-induced reductions in dendritic branching and PSD-95. Ampakines (CX546 and CX1739) and riluzole did not affect the antitumor efficacy of cisplatin in vitro. In conclusion, we established the first middle-aged rat model of cisplatin-induced CRCI, assessing the contribution of medical stress and longitudinal changes in BDNF levels on cognitive function, although future studies are warranted to assess the efficacy of BDNF enhancement in vivo on synaptic plasticity. Collectively, our results indicate that cancer treatment exerts long-lasting changes in BDNF levels, and support BDNF enhancement as a potential preventative approach to target CRCI with therapeutics that are FDA approved and/or in clinical study for other indications.

spatialHeatmap: visualizing spatial bulk and single-cell assays in anatomical images

Visualizing spatial assay data in anatomical images is vital for understanding biological processes in cell, tissue, and organ organizations. Technologies requiring this functionality include traditional one-at-a-time assays, and bulk and single-cell omics experiments, including RNA-seq and proteomics. The spatialHeatmap software provides a series of powerful new methods for these needs, and allows users to work with adequately formatted anatomical images from public collections or custom images. It colors the spatial features (e.g. tissues) annotated in the images according to the measured or predicted abundance levels of biomolecules (e.g. mRNAs) using a color key. This core functionality of the package is called a spatial heatmap plot. Single-cell data can be co-visualized in composite plots that combine spatial heatmaps with embedding plots of high-dimensional data. The resulting spatial context information is essential for gaining insights into the tissue-level organization of single-cell data, or vice versa. Additional core functionalities include the automated identification of biomolecules with spatially selective abundance patterns and clusters of biomolecules sharing similar abundance profiles. To appeal to both non-expert and computational users, spatialHeatmap provides a graphical and a command-line interface, respectively. It is distributed as a free, open-source Bioconductor package (https://bioconductor.org/packages/spatialHeatmap) that users can install on personal computers, shared servers, or cloud systems.

Ion Channels and Ionotropic Receptors in Astrocytes: Physiological Functions and Alterations in Alzheimer's Disease and Glioblastoma

The human brain is composed of nearly one hundred billion neurons and an equal number of glial cells, including macroglia, i.e., astrocytes and oligodendrocytes, and microglia, the resident immune cells of the brain. In the last few decades, compelling evidence has revealed that glial cells are far more active and complex than previously thought. In particular, astrocytes, the most abundant glial cell population, not only take part in brain development, metabolism, and defense against pathogens and insults, but they also affect sensory, motor, and cognitive functions by constantly modulating synaptic activity. Not surprisingly, astrocytes are actively involved in neurodegenerative diseases (NDs) and other neurological disorders like brain tumors, in which they rapidly become reactive and mediate neuroinflammation. Reactive astrocytes acquire or lose specific functions that differently modulate disease progression and symptoms, including cognitive impairments. Astrocytes express several types of ion channels, including K+, Na+, and Ca2+ channels, transient receptor potential channels (TRP), aquaporins, mechanoreceptors, and anion channels, whose properties and functions are only partially understood, particularly in small processes that contact synapses. In addition, astrocytes express ionotropic receptors for several neurotransmitters. Here, we provide an extensive and up-to-date review of the roles of ion channels and ionotropic receptors in astrocyte physiology and pathology. As examples of two different brain pathologies, we focus on Alzheimer's disease (AD), one of the most diffuse neurodegenerative disorders, and glioblastoma (GBM), the most common brain tumor. Understanding how ion channels and ionotropic receptors in astrocytes participate in NDs and tumors is necessary for developing new therapeutic tools for these increasingly common neurological conditions.

Genomics and transcriptomic alterations of the glutamate receptors in acute myeloid leukemia

Glutamine and glutamate have been widely explored as potential therapeutic targets in acute myeloid leukemia (AML). In addition to its bioenergetic role in leukemia cell proliferation, L-glutamate is a neurotransmitter that acts on glutamate receptors. However, the role of glutamate receptors in AML is largely understudied. Here, we comprehensively analyze the genomic and transcriptomic alterations of glutamate receptor genes in AML using publicly available data. We investigated the frequency of mutations in the glutamate receptor genes and whether an association exist between the presence of these mutations and clinical and molecular characteristics or patient's clinical outcome. We also assessed the dysregulation of glutamate receptor gene expression in AML with and without mutations and whether gene dysregulation is associated with clinical outcomes. We found that 29 (14.5%) of 200 patients with AML had a mutation in at least one glutamate receptor gene. The DNMT3A mutations were significantly more frequent in patients with mutations in at least one glutamate receptor gene compared with patients without mutations (13 of 29 [44.8%] vs. 41 of 171 [23.9%], p value: 0.02). Notably, patients with mutations in at least one glutamate receptor gene survived shorter than patients without mutations; however, the results did not reach statistical significance (overall survival: 15.5 vs. 19.0 months; p value: 0.10). Mutations in the glutamate receptor genes were not associated with changes in gene expression and the transcriptomic levels of glutamate receptor genes were not associated with clinical outcome.

Ligand-Gated Ion Channels: Prognostic and Therapeutic Implications for Gliomas

Gliomas are common primary brain malignancies that remain difficult to treat due to their overall aggressiveness and heterogeneity. Although a variety of therapeutic strategies have been employed for the treatment of gliomas, there is increasing evidence that suggests ligand-gated ion channels (LGICs) can serve as a valuable biomarker and diagnostic tool in the pathogenesis of gliomas. Various LGICs, including P2X, SYT16, and PANX2, have the potential to become altered in the pathogenesis of glioma, which can disrupt the homeostatic activity of neurons, microglia, and astrocytes, further exacerbating the symptoms and progression of glioma. Consequently, LGICs, including purinoceptors, glutamate-gated receptors, and Cys-loop receptors, have been targeted in clinical trials for their potential therapeutic benefit in the diagnosis and treatment of gliomas. In this review, we discuss the role of LGICs in the pathogenesis of glioma, including genetic factors and the effect of altered LGIC activity on the biological functioning of neuronal cells. Additionally, we discuss current and emerging investigations regarding the use of LGICs as a clinical target and potential therapeutic for gliomas.

Acai Berry (Euterpe sp.) Extracts Are Neuroprotective against L-Glutamate-Induced Toxicity by Limiting Mitochondrial Dysfunction and Cellular Redox Stress

Aberrant accumulation of the neurotransmitter L-glutamate (L-Glu) has been implicated as a mechanism of neurodegeneration, and the release of L-Glu after stroke onset leads to a toxicity cascade that results in neuronal death. The acai berry (Euterpe oleracea) is a potential dietary nutraceutical. The aim of this research was to investigate the neuroprotective effects of acai berry aqueous and ethanolic extracts to reduce the neurotoxicity to neuronal cells triggered by L-Glu application. L-Glu and acai berry effects on cell viability were quantified using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays, and effects on cellular bioenergetics were assessed via quantitation of the levels of cellular ATP, mitochondrial membrane potential (MMP), and production of reactive oxygen species (ROS) in neuroblastoma cells. Cell viability was also evaluated in human cortical neuronal progenitor cell culture after L-Glu or/and acai berry application. In isolated cells, activated currents using patch-clamping were employed to determine whether L-Glu neurotoxicity was mediated by ionotropic L-Glu-receptors (iGluRs). L-Glu caused a significant reduction in cell viability, ATP, and MMP levels and increased ROS production. The co-application of both acai berry extracts with L-Glu provided neuroprotection against L-Glu with sustained cell viability, decreased LDH production, restored ATP and MMP levels, and reduced ROS levels. Whole-cell patch-clamp recordings showed that L-Glu toxicity is not mediated by the activation of iGluRs in neuroblastoma cells. Fractionation and analysis of acai berry extracts with liquid chromatography-mass spectrometry identified several phytochemical antioxidants that may have provided neuroprotective effects. In summary, the acai berry contains nutraceuticals with antioxidant activity that may be a beneficial dietary component to limit pathological deficits triggered by excessive L-Glu accumulations.

A phase I trial of riluzole and sorafenib in patients with advanced solid tumors: CTEP #8850

BACKGROUND

Overexpression of metabotropic glutamate receptor 1 (GRM1) has been implicated in the pathogenesis of multiple cancers. Riluzole, an inhibitor of glutamate release, showed synergistic antitumor activity in combination with the multi-kinase inhibitor sorafenib in preclinical models. This phase I trial identified the toxicity profile, dose-limiting toxicities, maximum tolerated dose (MTD), and pharmacokinetic and pharmacodynamic properties of riluzole combined with sorafenib in patients with advanced cancers.

PATIENTS AND METHODS

Patients with refractory solid tumors were enrolled utilizing a 3+3 dose-escalation design. Riluzole was given at 100 mg PO BID in combination with sorafenib, beginning at 200 mg PO daily and escalating in 200 mg increments per level in 28-day cycles. Restaging evaluations were performed every 2 cycles.

RESULTS

35 patients were enrolled over 4 dose levels. The MTD was declared at dose level 3 (riluzole: 100 mg PO BID; sorafenib: 400 mg AM/200 mg PM). Pharmacokinetic analyses did not reveal definitive evidence of drug-drug interactions. Consistent decreases in phospho-forms of ERK and AKT in tumor tissue analyses with accompanying decrease in GRM1 expression and increase in pro-apoptotic BIM suggest target engagement by the combination. Best responses included a partial response in 1 (2.9%) patient with pancreatic acinar cell carcinoma with a KANK4-RAF1 fusion, and stable disease in 11 (36%) patients.

CONCLUSION

Combination therapy with riluzole and sorafenib was safe and tolerable in patients with advanced solid tumors. The partial response in a patient with a RAF1 fusion suggests that further exploration in a genomically selected cohort may be warranted.

D-Amino Acids and Cancer: Friends or Foes?

α-amino acids exist in two configurations, named D-(dextro) and L-(levo) enantiomers. L-amino acids are used in protein synthesis and play a central role in cell metabolism. The effects of the L-amino acid composition of foods and the dietary modifications of this composition on the efficacy of cancer therapies have been widely investigated in relation to the growth and reproduction of cancerous cells. However, less is known about the involvement of D-amino acids. In recent decades, D-amino acids have been identified as natural biomolecules that play interesting and specific roles as common components of the human diet. Here, we focus on recent investigations showing altered D-amino acid levels in specific cancer types and on the various roles proposed for these biomolecules related to cancer cell proliferation, cell protection during therapy, and as putative, innovative biomarkers. Notwithstanding recent progress, the relationship between the presence of D-amino acids, their nutritional value, and cancer cell proliferation and survival represents an underrated scientific issue. Few studies on human samples have been reported to date, suggesting a need for routine analysis of D-amino acid content and an evaluation of the enzymes involved in regulating their levels in clinical samples in the near future.

The role of glutamate receptors in the regulation of the tumor microenvironment

Glutamate, as one of the most important carbon sources in the TCA cycle, is central in metabolic processes that will subsequently influence tumor progression. Several factors can affect the expression of glutamate receptors, playing either a tumor-promoting or tumor-suppressor role in cancer. Thus, the activation of glutamate receptors by the ligand could play a role in tumor development as ample studies have demonstrated the expression of glutamate receptors in a broad range of tumor cells. Glutamate and its receptors are involved in the regulation of different immune cells' development and function, as suggested by the receptor expression in immune cells. The activation of glutamate receptors can enhance the effectiveness of the effector's T cells, or decrease the cytokine production in immunosuppressive myeloid-derived suppressor cells, increasing the antitumor immune response. These receptors are essential for the interaction between tumor and immune cells within the tumor microenvironment (TME) and the regulation of antitumor immune responses. Although the role of glutamate in the TCA cycle has been well studied, few studies have deeply investigated the role of glutamate receptors in the regulation of cancer and immune cells within the TME. Here, by a systematic review of the available data, we will critically assess the physiopathological relevance of glutamate receptors in the regulation of cancer and immune cells in the TME and provide some unifying hypotheses for futures research on the role of glutamate receptors in the immune modulation of the tumor.

Role of N-methyl-d-aspartate receptors in anxiety disorder with thyroid lesions

OBJECTIVE

Patients with anxiety disorder (AD) often have structural and functional abnormalities of the thyroid gland, but their specific causes remain unclear. N-methyl- d-aspartate receptors (NMDARs) play an important role in many psychosomatic diseases and tumorigenesis, but there are few reports on the role of NMDARs in AD with thyroid lesions, especially thyroid nodules (TNs).

METHODS

A cross-sectional study was conducted on patients admitted to the hospital with AD (n = 71) as the main diagnosis from April to October 2021. Meanwhile, patients with TNs with no AD (NAD-TN group, n = 20) and healthy subjects (HS group, n = 37) with matched age, sex, and education were randomly collected as controls. Patients with AD were sub-grouped into the AD with TNs (AD-TN group, n = 41) and the AD with no TNs (AD-NTN group, n = 30). The thyroid ultrasound reports, Hamilton Anxiety Scale (HAMA) scores, and the expression of NMDARs and their subunits (NR1, NR2A, and NR2B) and hypothalamic-pituitary-thyroid (HPT) axis-related hormones were analyzed in all subjects. Some patients with TNs underwent surgery and postoperative pathological examination.

RESULTS

Patients with AD showed a lower level of free triiodothyronine (FT3) and higher levels of thyrotropin-releasing hormone (TRH) and NMDARs and their subunits compared to the healthy controls. The expression of the NR2A subunit was higher in the AD-TN group than that in other three groups (AD-NTN, NAD-TN, and HS groups, F = 13.650, p < 0.001). Regression analysis showed that the level of NMDARs was positively correlated with the HAMA scores (B = 1.622, p = 0.029) and the maximum diameter of TNs (B = 3.836, p = 0.005). Immunohistochemical results showed that the NR2A subunit was widely expressed in multinodular goiter (MNG) and papillary thyroid carcinoma (PTC) tissues, while the expression of the NR2B subunit was lower in PTC adjacent and MNG tissues and almost absent in PTC tissues.

CONCLUSION

In a sample of mostly women hospitalized with generalized anxiety disorder (GAD) or panic disorder, abnormal expression of NMDARs is closely related to AD with thyroid lesions, NMDAR subunits may have various activities and exert diverse effects in TNs, and the NR2A subunit may be an important regulator in AD with TNs.

Establishment and validation of individualized clinical prognostic markers for LUAD patients based on autophagy-related genes

There is considerable heterogeneity in the genomic drivers of lung adenocarcinoma, which has a dismal prognosis. Bioinformatics analysis was performed on lung adenocarcinoma (LUAD) datasets to establish a multi-autophagy gene model to predict patient prognosis. LUAD data were downloaded from The Cancer Genome Atlas (TCGA) database as a training set to construct a LUAD prognostic model. According to the risk score, a Kaplan-Meier cumulative curve was plotted to evaluate the prognostic value. Furthermore, a nomogram was established to predict the three-year and five-year survival of patients with LUAD based on their prognostic characteristics. Two genes (ITGB1 and EIF2AK3) were identified in the autophagy-related prognostic model, and the multivariate Cox proportional risk model showed that risk score was an independent predictor of prognosis in LUAD patients (HR=3.3, 95%CI= 2.3 to 4.6, P< 0.0001). The Kaplan-Meier cumulative curve showed that low-risk patients had significantly better overall (P<0.0001). The validation dataset GSE68465 further confirmed the nomogram’s robust ability to assess the prognosis of LUAD patients. A prognosis model of autophagy-related genes based on a LUAD dataset was constructed and exhibited diagnostic value in the prognosis of LUAD patients. Moreover, real-time qPCR confirmed the expression patterns of EIF2AK3 and ITGB1 in LUAD cell lines. Two key autophagy-related genes have been suggested as prognostic markers for lung adenocarcinoma.

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.

Analysis of D-Amino Acids: Relevance in Human Disease

Small metabolic molecules often are chiral and can play important roles in regulating a variety of biological functions, occasionally providing information about the presence and progression of disease. The most ubiquitous class of such small molecules are amino acids. Sensitive and accurate analysis of the less prevalent D-amino acids as free entities or as constituents of peptides can be challenging, particularly when complex physiological matrices are involved. The number of studies involving low-abundance D-amino acids in biological systems has increased significantly over the last decade. Studies involving their presence and importance have become increasingly difficult to ignore. Their relevance in neurological pathologies, cancer, kidney disorders, and more, has advanced. Chiral separations have played and continue to play a central role in these studies. Because enantiomers and epimers have the same exact mass, stereoselective separations are essential. However, sensitive detection is also necessary because trace levels of these analytes are involved. Multidimensional separations often provide the best avenue for accurate qualitative and quantitative results. Future developments will involve faster and highly specific routine testing, particularly if these analyses are to enter the clinical realm.

Emerging Roles of the Nervous System in Gastrointestinal Cancer Development

Simple Summary

Nerve–cancer cross-talk has increasingly become a focus of the oncology field, particularly in gastrointestinal (GI) cancers. The indispensable roles of the nervous system in GI tumorigenesis and malignancy have been dissected by epidemiological, experimental animal and mechanistic data. Herein, we review and integrate recent discoveries linking the nervous system to GI cancer initiation and progression, and focus on the molecular mechanisms by which nerves and neural receptor pathways drive GI malignancy.

Abstract

Our understanding of the fascinating connection between nervous system and gastrointestinal (GI) tumorigenesis has expanded greatly in recent years. Recent studies revealed that neurogenesis plays an active part in GI tumor initiation and progression. Tumor-driven neurogenesis, as well as neurite outgrowth of the pre-existing peripheral nervous system (PNS), may fuel GI tumor progression via facilitating cancer cell proliferation, chemoresistance, invasion and immune escape. Neurotransmitters and neuropeptides drive the activation of various oncogenic pathways downstream of neural receptors within cancer cells, underscoring the importance of neural signaling pathways in GI tumor malignancy. In addition, neural infiltration also plays an integral role in tumor microenvironments, and contributes to an environment in favor of tumor angiogenesis, immune evasion and invasion. Blockade of tumor innervation via denervation or pharmacological agents may serve as a promising therapeutic strategy against GI tumors. In this review, we summarize recent findings linking the nervous system to GI tumor progression, set the spotlight on the molecular mechanisms by which neural signaling fuels cancer aggressiveness, and highlight the importance of targeting neural mechanisms in GI tumor therapy.

A phase Ib dose-escalation study of troriluzole (BHV-4157), an oral glutamatergic signaling modulator, in combination with nivolumab in patients with advanced solid tumors

BACKGROUND

Glutamate signaling activates MAPK and PI3K/AKT pathways in tumor cells. Treatment with riluzole, a glutamate release inhibitor, has been previously shown to be safe in melanoma patients and produced biologic effects, but did not lead to radiographic responses, possibly due to poor pharmacokinetic properties. Therefore, we conducted a phase Ib trial to determine the safety and tolerability of the combination of the riluzole prodrug troriluzole (BHV-4157, trigriluzole) and the PD-1 antibody nivolumab in patients with advanced solid tumors.

METHODS

Patients with advanced or refractory solid tumors and measurable disease per RECIST 1.1 were treated with increasing doses of troriluzole using a semi-Bayesian modified toxicity probability interval dose escalation procedure. Troriluzole monotherapy was orally self-administered for a 14-day lead-in period followed by continuation of troriluzole in combination with nivolumab 240 mg IV every 2 weeks. Endpoints included safety, pharmacokinetics (PK) and efficacy.

RESULTS

We enrolled 14 patients with advanced solid tumors (melanoma = 3, NSCLC = 3, renal cell carcinoma = 2, bladder/urothelial = 2, ovarian cancer = 1, adenoid cystic carcinoma = 1, pleural mesothelial = 1, head and neck cancer = 1). Eleven patients had cancer progression on prior therapy with PD-1 or PD-L1 agent. Patients received troriluzole total daily doses from 140 to 560 mg (divided). The most common treatment-related adverse events (TRAE) occurring in ≥ 5 patients (> 35%) were transaminitis and increased lipase. DLT (dose-limiting toxicity) occurred in 3 patients: (1) grade 3 anorexia, (2) grade 3 fatigue and, (3) grade 3 atrial fibrillation. Six patients were treated at the MTD (maximum tolerated dose). No subjects discontinued treatment due to AEs. One response occurred (7%), which was a partial response in a subject who had PD-1 refractory disease. The 6-month PFS rate was 21%. PK data showed that the prodrug troriluzole was efficiently cleaved into riluzole by 2-h post-dosing in all dose cohorts tested.

CONCLUSION

The combination of troriluzole and nivolumab was safe and well-tolerated. The MTD of troriluzole was determined to be 420 mg total daily dose. The observed antitumor activity, primarily disease stabilization, is of interest in patients with PD-1 resistant tumors. Trial Registration ClinicalTrials.gov Identifier NCT03229278.

Memantine in the Prevention of Radiation-Induced Brain Damage: A Narrative Review

Simple Summary

Decline in cognitive function is a major problem for patients undergoing whole-brain radiotherapy (WBRT). Scientific interest has increased due to the high dropout rate of patients in the first months after WBRT and the early onset of cognitive decline. Therefore, the study of antiglutamatergic pharmacological prophylaxis and hippocampal-sparing WBRT techniques has been deepened based on the knowledge of the mechanisms of hyperglutamatergic neurotoxicity and the role of some hippocampal areas in cognitive decline. In order to provide a summary of the evidence in this field, and to foster future research in this setting, this literature review presents current evidence on the prevention of radiation-induced cognitive decline and particularly on the role of memantine.

Abstract

Preserving cognitive functions is a priority for most patients with brain metastases. Knowing the mechanisms of hyperglutamatergic neurotoxicity and the role of some hippocampal areas in cognitive decline (CD) led to testing both the antiglutamatergic pharmacological prophylaxis and hippocampal-sparing whole-brain radiotherapy (WBRT) techniques. These studies showed a relative reduction in CD four to six months after WBRT. However, the failure to achieve statistical significance in one study that tested memantine alone (RTOG 0614) led to widespread skepticism about this drug in the WBRT setting. Moreover, interest grew in the reasons for the strong patient dropout rates in the first few months after WBRT and for early CD onset. In fact, the latter can only partially be explained by subclinical tumor progression. An emerging interpretation of the (not only) cognitive impairment during and immediately after WBRT is the dysfunction of the limbic and hypothalamic system with its immune and hormonal consequences. This new understanding of WBRT-induced toxicity may represent the basis for further innovative trials. These studies should aim to: (i) evaluate in greater detail the cognitive effects and, more generally, the quality of life impairment during and immediately after WBRT; (ii) study the mechanisms producing these early effects; (iii) test in clinical studies, the modern and advanced WBRT techniques based on both hippocampal-sparing and hypothalamic-pituitary-sparing, currently evaluated only in planning studies; (iv) test new timings of antiglutamatergic drugs administration aimed at preventing not only late toxicity but also acute effects.

Transcriptomic profiling of nonneoplastic cortical tissues reveals epileptogenic mechanisms in dysembryoplastic neuroepithelial tumors

Low-grade dysembryoplastic neuroepithelial tumors (DNTs) are a frequent cause of drug-refractory epilepsy. Molecular mechanisms underlying seizure generation in these tumors are poorly understood. This study was conducted to identify altered genes in nonneoplastic epileptogenic cortical tissues (ECTs) resected from DNT patients during electrocorticography (ECoG)-guided surgery. RNA sequencing (RNAseq) was used to determine the differentially expressed genes (DEGs) in these high-spiking ECTs compared to non-epileptic controls. A total of 477 DEGs (180 upregulated; 297 downregulated) were observed in the ECTs compared to non-epileptic controls. Gene ontology analysis revealed enrichment of genes belonging to the following Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways: (i) glutamatergic synapse; (ii) nitrogen metabolism; (iii) transcriptional misregulation in cancer; and (iv) protein digestion and absorption. The glutamatergic synapse pathway was enriched by DEGs such as GRM4, SLC1A6, GRIN2C, GRM2, GRM5, GRIN3A, and GRIN2B. Enhanced glutamatergic activity was observed in the pyramidal neurons of ECTs, which could be attributed to altered synaptic transmission in these tissues compared to non-epileptic controls. Besides glutamatergic synapse, altered expression of other genes such as GABRB1 (synapse formation), SLIT2 (axonal growth), and PROKR2 (neuron migration) could be linked to epileptogenesis in ECTs. Also, upregulation of GABRA6 gene in ECTs could underlie benzodiazepine resistance in these patients. Neural cell-type-specific gene set enrichment analysis (GSEA) revealed transcriptome of ECTs to be predominantly contributed by microglia and neurons. This study provides first comprehensive gene expression profiling of nonneoplastic ECTs of DNT patients and identifies genes/pathways potentially linked to epileptogenesis.

Ligand-Gated Ion Channels as Targets for Treatment and Management of Cancers

Ligand-gated ion channels are an ionotropic receptor subtype characterized by the binding of an extracellular ligand, followed by the transient passage of ions through a transmembrane pore. Ligand-gated ion channels are commonly subcategorized into three superfamilies: purinoreceptors, glutamate receptors, and Cys-loop receptors. This classification is based on the differing topographical morphology of the receptors, which in turn confers functional differences. Ligand-gated ion channels have a diverse spatial and temporal expression which implicate them in key cellular processes. Given that the transcellular electrochemical gradient is finely tuned in eukaryotic cells, any disruption in this homeostasis can contribute to aberrancies, including altering the activity of pro-tumorigenic molecular pathways, such as the MAPK/ERK, RAS, and mTOR pathways. Ligand-gated ion channels therefore serve as a potential targetable system for cancer therapeutics. In this review, we analyze the role that each of the three ligand-gated ion channel superfamilies has concerning tumor proliferation and as a target for the treatment of cancer symptomatology.

Glutamatergic system components as potential biomarkers and therapeutic targets in cancer in non-neural organs

Glutamate is one of the most abundant amino acids in the blood. Besides its role as a neurotransmitter in the brain, it is a key substrate in several metabolic pathways and a primary messenger that acts through its receptors outside the central nervous system (CNS). The two main types of glutamate receptors, ionotropic and metabotropic, are well characterized in CNS and have been recently analyzed for their roles in non-neural organs. Glutamate receptor expression may be particularly important for tumor growth in organs with high concentrations of glutamate and might also influence the propensity of such tumors to set metastases in glutamate-rich organs, such as the liver. The study of glutamate transporters has also acquired relevance in the physiology and pathologies outside the CNS, especially in the field of cancer research. In this review, we address the recent findings about the expression of glutamatergic system components, such as receptors and transporters, their role in the physiology and pathology of cancer in non-neural organs, and their possible use as biomarkers and therapeutic targets.

NMDA receptor expression during cell transformation process at early stages of liver cancer in rodent models

Hepatocellular carcinoma (HCC) is the most common primary liver cancer, which is not sensitive to radiotherapy and chemotherapy and very often experiences postoperative relapse. In this regard, effective screening of liver cancer is considered as the most important and urgent task. The aim of our study was to determine whether N-methyl-D-aspartate receptor (NMDAR) and, in particular, its subunits, can serve as biomarkers to distinguish the precancerous liver at early stages of liver fibrosis. We assessed the development of HCC after 10, 15, and 22 wk using a HCC rat model. The expression of NMDAR subunits was monitored at different stages of HCC by means of immunohistochemistry combined with epifluorescence microscopy imaging, Western blotting, and direct bisulfite sequencing. NMDAR subunits were not found in healthy liver tissues. In contrast, NMDAR subunits, in particular NR1 and NR2B, appeared at the stage of severe liver fibrosis (precancerous liver disease) in rats and were expressed during the development of HCC in rats and mice. Using the direct bisulfite sequencing, we detected that increased expression of NMDAR directly correlated with the demethylation of CpG islands in the promoter region of genes encoding receptor subunits. The obtained results confirmed that NMDAR subunits can serve as new biomarkers of precancerous liver disease, severe fibrosis, and its progression towards HCC.NEW & NOTEWORTHY We have shown NMDAR expression in cell transformation process at early stages of cancer, specifically HCC. The aim of our study was to define the disease stages from precancerous liver disease towards liver cancer progression when NMDAR subunits were expressed/detected. A fibrosis/HCC rat model, immunohistochemistry combined with epifluorescence microscopy imaging, Western blotting was used. The dynamics of appearance of NMDAR subunits, their expression and methylation status during the development of HCC were shown and discussed.

Glutamatergic Signaling a Therapeutic Vulnerability in Melanoma

Like other cancers, melanomas are associated with the hyperactivation of two major cell signaling cascades, the MAPK and PI3K/AKT pathways. Both pathways are activated by numerous genes implicated in the development and progression of melanomas such as mutated BRAF, RAS, and NF1. Our lab was the first to identify yet another driver of melanoma, Metabotropic Glutamate Receptor 1 (protein: mGluR1, mouse gene: Grm1, human gene: GRM1), upstream of the MAPK and PI3K/AKT pathways. Binding of glutamate, the natural ligand of mGluR1, activates MAPK and PI3K/AKT pathways and sets in motion the deregulated cellular responses in cell growth, cell survival, and cell metastasis. In this review, we will assess the proposed modes of action that mediate the oncogenic properties of mGluR1 in melanoma and possible application of anti-glutamatergic signaling modulator(s) as therapeutic strategy for the treatment of melanomas.

Inhibition of metabotropic glutamate receptor III facilitates sensitization to alkylating chemotherapeutics in glioblastoma

Glioblastoma (GBM), the most malignant tumor of the central nervous system, is marked by its dynamic response to microenvironmental niches. In particular, this cellular plasticity contributes to the development of an immediate resistance during tumor treatment. Novel insights into the developmental trajectory exhibited by GBM show a strong capability to respond to its microenvironment by clonal selection of specific phenotypes. Using the same mechanisms, malignant GBM do develop intrinsic mechanisms to resist chemotherapeutic treatments. This resistance was reported to be sustained by the paracrine and autocrine glutamate signaling via ionotropic and metabotropic receptors. However, the extent to which glutamatergic signaling modulates the chemoresistance and transcriptional profile of the GBM remains unexplored. In this study we aimed to map the manifold effects of glutamate signaling in GBM as the basis to further discover the regulatory role and interactions of specific receptors, within the GBM microenvironment. Our work provides insights into glutamate release dynamics, representing its importance for GBM growth, viability, and migration. Based on newly published multi-omic datasets, we explored the and characterized the functions of different ionotropic and metabotropic glutamate receptors, of which the metabotropic receptor 3 (GRM3) is highlighted through its modulatory role in maintaining the ability of GBM cells to evade standard alkylating chemotherapeutics. We addressed the clinical relevance of GRM3 receptor expression in GBM and provide a proof of concept where we manipulate intrinsic mechanisms of chemoresistance, driving GBM towards chemo-sensitization through GRM3 receptor inhibition. Finally, we validated our findings in our novel human organotypic section-based tumor model, where GBM growth and proliferation was significantly reduced when GRM3 inhibition was combined with temozolomide application. Our findings present a new picture of how glutamate signaling via mGluR3 interacts with the phenotypical GBM transcriptional programs in light of recently published GBM cell-state discoveries.

G Protein-Coupled receptors and heterotrimeric G proteins as cancer drivers

G protein-coupled receptors (GPCRs) and heterotrimeric G proteins play central roles in a diverse array of cellular processes. As such, dysregulation of GPCRs and their coupled heterotrimeric G proteins can dramatically alter the signalling landscape and functional state of a cell. Consistent with their fundamental physiological functions, GPCRs and their effector heterotrimeric G proteins are implicated in some of the most prevalent human diseases, including a complex disease such as cancer that causes significant morbidity and mortality worldwide. GPCR/G protein-mediated signalling impacts oncogenesis at multiple levels by regulating tumour angiogenesis, immune evasion, metastasis, and drug resistance. Here, we summarize the growing body of research on GPCRs and their effector heterotrimeric G proteins as drivers of cancer initiation and progression, and as emerging antitumoural therapeutic targets.

Mechanisms of Invasion in Glioblastoma: Extracellular Matrix, Ca2+ Signaling, and Glutamate

Glioblastoma (GBM) is the most common and malignant form of primary brain tumor with a median survival time of 14–16 months in GBM patients. Surgical treatment with chemotherapy and radiotherapy may help increase survival by removing GBM from the brain. However, complete surgical resection to eliminate GBM is almost impossible due to its high invasiveness. When GBM cells migrate to the brain, they interact with various cells, including astrocytes, neurons, endothelial cells, and the extracellular matrix (ECM). They can also make their cell body shrink to infiltrate into narrow spaces in the brain; thereby, they can invade regions of the brain and escape from surgery. Brain tumor cells create an appropriate microenvironment for migration and invasion by modifying and degrading the ECM. During those processes, the Ca²⁺ signaling pathway and other signaling cascades mediated by various ion channels contribute mainly to gene expression, motility, and invasion of GBM cells. Furthermore, GBM cells release glutamate, affecting migration via activation of ionotropic glutamate receptors in an autocrine manner. This review focuses on the cellular mechanisms of glioblastoma invasion and motility related to ECM, Ca²⁺ signaling, and glutamate. Finally, we discuss possible therapeutic interventions to inhibit invasion by GBM cells.

Glutamatergic Mechanisms in Glioblastoma and Tumor-Associated Epilepsy

The progression of glioblastomas is associated with a variety of neurological impairments, such as tumor-related epileptic seizures. Seizures are not only a common comorbidity of glioblastoma but often an initial clinical symptom of this cancer entity. Both, glioblastoma and tumor-associated epilepsy are closely linked to one another through several pathophysiological mechanisms, with the neurotransmitter glutamate playing a key role. Glutamate interacts with its ionotropic and metabotropic receptors to promote both tumor progression and excitotoxicity. In this review, based on its physiological functions, our current understanding of glutamate receptors and glutamatergic signaling will be discussed in detail. Furthermore, preclinical models to study glutamatergic interactions between glioma cells and the tumor-surrounding microenvironment will be presented. Finally, current studies addressing glutamate receptors in glioma and tumor-related epilepsy will be highlighted and future approaches to interfere with the glutamatergic network are discussed.

Acetylation-dependent glutamate receptor GluR signalosome formation for STAT3 activation in both transcriptional and metabolism regulation

Besides their original regulating roles in the brain, spinal cord, retina, and peripheral nervous system for mediating fast excitatory synaptic transmission, glutamate receptors consisting of metabotropic glutamate receptors (GluRs) and ionotropic glutamate receptors (iGluRs) have emerged to have a critical role in the biology of cancer initiation, progression, and metastasis. However, the precise mechanism underpinning the signal transduction mediated by ligand-bound GluRs is not clearly elucidated. Here, we show that iGluRs, GluR1 and GluR2, are acetylated by acetyltransferase CREB-binding protein upon glutamate stimulation of cells, and are targeted by lysyl oxidase-like 2 for deacetylation. Acetylated GluR1/2 recruit β-arrestin1/2 and signal transducer and activator of transcription 3 (STAT3) to form a protein complex. Both β-arrestin1/2 and STAT3 are subsequently acetylated and activated. Simultaneously, activated STAT3 acetylated at lysine 685 translocates to mitochondria to upregulate energy metabolism-related gene transcription. Our results reveal that acetylation-dependent formation of GluR1/2-β-arrestin1/2-STAT3 signalosome is critical for glutamate-induced cell proliferation.

Bridging the Metabolic Parallels Between Neurological Diseases and Cancer

Despite the many recent breakthroughs in cancer research, oncology has traditionally been seen as a distinct field from other diseases. Recently, more attention has been paid to repurposing established therapeutic strategies and targets of other diseases towards cancer treatment, with some of these attempts generating promising outcomes [1, 2]. Recent studies using advanced metabolomics technologies [3] have shown evidence of close metabolic similarities between cancer and neurological diseases. These studies have unveiled several metabolic characteristics shared by these two categories of diseases, including metabolism of glutamine, gamma-aminobutyric acid (GABA), and N-acetyl-aspartyl-glutamate (NAAG) [4-6]. The striking metabolic overlap between cancer and neurological diseases sheds light on novel therapeutic strategies for cancer treatment. For example, 2-(phosphonomethyl) pentanedioic acid (2-PMPA), one of the glutamate carboxypeptidase II (GCP II) inhibitors that prevent the conversion of NAAG to glutamate, has been shown to suppress cancer growth [6, 7]. These promising results have led to an increased interest in integrating this metabolic overlap between cancer and neurological diseases into the study of cancer metabolism. The advantages of studying this metabolic overlap include not only drug repurposing but also translating existing knowledge from neurological diseases to the field of cancer research. This chapter discusses the specific overlapping metabolic features between cancer and neurological diseases, focusing on glutamine, GABA, and NAAG metabolisms. Understanding the interconnections between cancer and neurological diseases will guide researchers and clinicians to find more effective cancer treatments.

Communication of Glioma cells with neuronal plasticity: What is the underlying mechanism?

There has been a significantly rising discussion on how neuronal plasticity communicates with the glioma growth and invasion. This literature review aims to determine which neurotransmitters, ion channels and signaling pathways are involved in this context, how information is transferred from synaptic sites to the glioma cells and how glioma cells apply established mechanics of synaptic plasticity for their own increment. This work is a compilation of some outstanding findings related to the influence of the glutamate, calcium, potassium, chloride and sodium channels and other important brain plasticity molecules over the glioma progression. These topics also include the relevant molecular signaling data which could prove to be helpful for an effective clinical management of brain tumors in the future.

Roles of N-methyl-D-aspartate receptors and D-amino acids in cancer cell viability

N-methyl-D-aspartate (NMDA) receptors, which are widely present in the central nervous system, have also been found to be up-regulated in a variety of cancer cells and tumors and they can play active roles in cancer cell growth regulation. NMDA receptor antagonists have been found to affect cancer cell viability and interfere with tumor growth. Moreover, cancer cells also have been shown to have elevated levels of some D-amino acids. Two human skin cell lines: Hs 895.T skin cancer and Hs 895.Sk skin normal cells were investigated. They were derived from the same patient to provide tumor and normal counterparts for comparative studies. The expression of specific NMDA receptors was confirmed for the first time in both skin cell lines. Dizocilpine (MK-801) and memantine, NMDA receptor channel blockers, were found to inhibit the growth of human skin cells by reducing or stopping NMDA receptor activity. Addition of D-Ser, D-Ala, or D-Asp, however, significantly reversed the antiproliferative effect on the human skin cells triggered by MK-801 or memantine. Even more interesting was the finding that the specific intracellular composition of a few relatively uncommon amino acids was selectively elevated in skin cancer cells when exposed to MK-801. It appears that a few specific and upregulated D-amino acids can reverse the drug-induced antiproliferative effect in skin cancer cells via the reactivation of NMDA receptors. This study provides a possible innovative anticancer therapy by acting on the D-amino acid pathway in cancer cells either blocking or activating their regulatory enzymes.

Uncovering the Role of N-Acetyl-Aspartyl-Glutamate as a Glutamate Reservoir in Cancer

N-acetyl-aspartyl-glutamate (NAAG) is a peptide-based neurotransmitter that has been extensively studied in many neurological diseases. In this study, we show a specific role of NAAG in cancer. We found that NAAG is more abundant in higher grade cancers and is a source of glutamate in cancers expressing glutamate carboxypeptidase II (GCPII), the enzyme that hydrolyzes NAAG to glutamate and N-acetyl-aspartate (NAA). Knocking down GCPII expression through genetic alteration or pharmacological inhibition of GCPII results in a reduction of both glutamate concentrations and cancer growth. Moreover, targeting GCPII in combination with glutaminase inhibition accentuates these effects. These findings suggest that NAAG serves as an important reservoir to provide glutamate to cancer cells through GCPII when glutamate production from other sources is limited. Thus, GCPII is a viable target for cancer therapy, either alone or in combination with glutaminase inhibition.

Nguyen et al. show that NAAG is more abundant in higher grade cancers and a source of glutamate in cancers expressing GCPII, the enzyme that hydrolyzes NAAG to glutamate and NAA. The results suggest that GCPII is a viable target for cancer therapy, either alone or in combination with glutaminase inhibition.

Tumor-induced neurogenesis and immune evasion as targets of innovative anti-cancer therapies

Normal cells are hijacked by cancer cells forming together heterogeneous tumor masses immersed in aberrant communication circuits that facilitate tumor growth and dissemination. Besides the well characterized angiogenic effect of some tumor-derived factors; others, such as BDNF, recruit peripheral nerves and leukocytes. The neurogenic switch, activated by tumor-derived neurotrophins and extracellular vesicles, attracts adjacent peripheral fibers (autonomic/sensorial) and neural progenitor cells. Strikingly, tumor-associated nerve fibers can guide cancer cell dissemination. Moreover, IL-1β, CCL2, PGE₂, among other chemotactic factors, attract natural immunosuppressive cells, including T regulatory (Tregs), myeloid-derived suppressor cells (MDSCs), and M2 macrophages, to the tumor microenvironment. These leukocytes further exacerbate the aberrant communication circuit releasing factors with neurogenic effect. Furthermore, cancer cells directly evade immune surveillance and the antitumoral actions of natural killer cells by activating immunosuppressive mechanisms elicited by heterophilic complexes, joining cancer and immune cells, formed by PD-L1/PD1 and CD80/CTLA-4 plasma membrane proteins. Altogether, nervous and immune cells, together with fibroblasts, endothelial, and bone-marrow-derived cells, promote tumor growth and enhance the metastatic properties of cancer cells. Inspired by the demonstrated, but restricted, power of anti-angiogenic and immune cell-based therapies, preclinical studies are focusing on strategies aimed to inhibit tumor-induced neurogenesis. Here we discuss the potential of anti-neurogenesis and, considering the interplay between nervous and immune systems, we also focus on anti-immunosuppression-based therapies. Small molecules, antibodies and immune cells are being considered as therapeutic agents, aimed to prevent cancer cell communication with neurons and leukocytes, targeting chemotactic and neurotransmitter signaling pathways linked to perineural invasion and metastasis.

Tonic NMDA receptor signalling shapes endosomal organisation in mammalian cells

Calcium signalling through NMDA-type glutamate receptors (NMDARs) plays a key role in synaptic plasticity in the central nervous system (CNS). NMDAR expression has also been detected in other tissues and aberrant glutamate signalling has been linked to cancer; however, the significance of NMDAR function outside of the CNS remains unclear. Here, I show that removal of extracellular calcium rapidly decreases the size of early endosomes in primary human fibroblasts. This effect can be mimicked by blockade of NMDA-type glutamate receptors but not voltage-gated calcium channels (VGCCs), and can also be observed in primary hippocampal neurons and Jurkat T cells. Conversely, in a breast cancer cell line MDA-MB-231 NMDAR blockade results in an increase in endosomal size and decrease in number. These findings reveal that calcium signalling via glutamate receptors controls the structure of the endosomal system and suggest that aberrations in NMDAR-regulated membrane trafficking may be associated with cancer.

Epileptogenesis and oncogenesis: An antineoplastic role for antiepileptic drugs in brain tumours?

The first description of epileptic seizures due to brain tumours occurred in 19th century. Nevertheless, after over one hundred years, scientific literature is still lacking on how epilepsy and its treatment can affect tumour burden, progression and clinical outcomes. In patients with brain tumours, epilepsy dramatically impacts their quality of life (QoL). Even antiepileptic therapy seems to affect tumor lesion development. Numerous studies suggest that certain actors involved in epileptogenesis (inflammatory changes, glutamate and its ionotropic and metabotropic receptors, GABA-A and its GABA-AR receptor, as well as certain ligand- and voltage-gated ion channel) may also contribute to tumorigenesis. Although some antiepileptic drugs (AEDs) are known operating on such mechanisms underlying epilepsy and tumor development, few preclinical and clinical studies have tried to investigate them as targets of pharmacological tools acting to control both phenomena. The primary aim of this review is to summarize known determinants and pathophysiological mechanisms of seizures, as well as of cell growth and spread, in patients with brain tumors. Therefore, a special focus will be provided on the anticancer effects of commonly prescribed AEDs (including levetiracetam, valproic acid, oxcarbazepine and others), with an overview of both preclinical and clinical data. Potential clinical applications of this finding are discussed.

Kaposi's Sarcoma-Associated Herpesvirus Infection Induces the Expression of Neuroendocrine Genes in Endothelial Cells

Kaposi's sarcoma-associated herpesvirus (KSHV) is etiologically associated with endothelial Kaposi's sarcoma (KS) in immunocompromised individuals. KS lesion cells exhibit many similarities to neuroendocrine (NE) cancers, such as highly vascular and red/purple tumor lesions, spindle-shaped cells, an insignificant role for classic oncogenes in tumor development, the release of bioactive amines, and indolent growth of the tumors. However, the mechanistic basis for the similarity of KS lesion endothelial cells to neuroendocrine tumors remains unknown. Next-generation sequencing and bioinformatics analysis in the present study demonstrate that endothelial cells latently infected with KSHV express several neuronal and NE genes. De novo infection of primary dermal endothelial cells with live and UV-inactivated KSHV demonstrated that viral gene expression is responsible for the upregulation of five selected NE genes (adrenomedullin 2 [ADM2], histamine receptor H1 [HRH1], neuron-specific enolase [NSE] [ENO2], neuronal protein gene product 9.5 [PGP9.5], and somatostatin receptor 1 [SSTR1]). Immunofluorescence and immunohistochemistry examinations demonstrated the robust expression of the NE genes HRH1 and NSE/ENO2 in KSHV-infected KS tissue samples and KS visceral tissue microarrays. Further analysis demonstrated that KSHV latent open reading frame K12 (ORFK12) gene (kaposin A)-mediated decreased host REST/NRSF (RE1-silencing transcription factor/neuron-restrictive silencer factor) protein, a neuronal gene transcription repressor protein, is responsible for NE gene expression in infected endothelial cells. The NE gene expression observed in KSHV-infected cells was recapitulated in uninfected endothelial cells by the exogenous expression of ORFK12 and by the treatment of cells with the REST inhibitor X5050. When the neuroactive ligand-activating receptor HRH1 and inhibitory SSTR1 were knocked out by CRISPR, HRH1 knockout (KO) significantly inhibited cell proliferation, while SSTR1 KO induced cell proliferation, thus suggesting that HRH1 and SSTR1 probably counteract each other in regulating KSHV-infected endothelial cell proliferation. These results demonstrate that the similarity of KS lesion cells to neuroendocrine tumors is probably a result of KSHV infection-induced transformation of nonneuronal endothelial cells into cells with neuroendocrine features. These studies suggest a potential role of neuroendocrine pathway genes in the pathobiological characteristics of KSHV-infected endothelial cells, including a potential mechanism of escape from the host immune system by the expression of immunologically privileged neuronal-site NE genes, and NE genes could potentially serve as markers for KSHV-infected KS lesion endothelial cells as well as novel therapeutic targets to control KS lesions.IMPORTANCE Kaposi's sarcoma-associated herpesvirus (KSHV) manipulates several cellular pathways for its survival advantage during its latency in the infected human host. Here, we demonstrate that KSHV infection upregulates the expression of genes related to neuronal and neuroendocrine (NE) functions that are characteristic of NE tumors, both in vitro and in KS patient tissues and the heterogeneity of neuroendocrine receptors having opposing roles in KSHV-infected cell proliferation. Induction of NE genes by KSHV could also provide a potential survival advantage, as the expression of proteins at immunologically privileged sites such as neurons on endothelial cells may be an avenue to escape host immune surveillance functions. The NE gene products identified here could serve as markers for KSHV-infected cells and could potentially serve as therapeutic targets to combat KSHV-associated KS.

Identification of the differential expression of genes and upstream microRNAs in small cell lung cancer compared with normal lung based on bioinformatics analysis

Small cell lung cancer (SCLC) is one of the most lethal cancer, mainly attributing to its high tendency to metastasis. Mounting evidence has demonstrated that genes and microRNAs (miRNAs) are related to human cancer onset and progression including invasion and metastasis.An eligible gene dataset and an eligible miRNA dataset were downloaded from the Gene Expression Omnibus (GEO) database based our screening criteria. Differentially expressed genes (DE-genes) or DE-miRNAs for each dataset obtained by the R software package. The potential target genes of the top 10 DE-miRNAs were predicted by multiple databases. For annotation, visualization and integrated discovery, Metascape 3.0 was introduced to perform enrichment analysis for the DE-genes and the predicted target genes of the selected top 10 DE-miRNAs, including Pathway and Process Enrichment Analysis or protein-protein interaction enrichment analysis. The intersection of predicted target genes and DE-genes was taken as the final DE-genes. Then apply the predicted miRNAs-targets relationship of top 10 DE-miRNAs to the final DE-genes to gain more convinced DE-miRNAs, DE-genes and their one to one relationship.GSE19945 (miRNA microarray) and GSE40275 (gene microarray) datasets were selected and downloaded. 56 DE-miRNAs and 861 DE-genes were discovered. 297 miRNAs-targets relationships (284 unique genes) were predicted as the target of top 10 upregulating DE-miRNAs. 245 miRNAs-targets relationships (238 unique genes) were identified as the target of top 10 downregulating DE-miRNAs. The key results of enrichment analysis include protein kinase B signaling, transmembrane receptor protein tyrosine kinase signaling pathway, negative regulation of cell differentiation, response to growth factor, cellular response to lipid, muscle structure development, response to growth factor, signaling by Receptor Tyrosine Kinases, epithelial cell migration, cellular response to organic cyclic compound, Cell Cycle (Mitotic), DNA conformation change, cell division, DNA replication, cell cycle phase transition, blood vessel development, inflammatory response, Staphylococcus aureus infection, leukocyte migration, and myeloid leukocyte activation. Differential expression of genes-upstream miRNAs (RBMS3-hsa-miR-7-5p, NEDD9-hsa-miR-18a-5p, CRIM1-hsa-miR-18a-5p, TGFBR2-hsa-miR-9-5p, MYO1C-hsa-miR-9-5p, KLF4-hsa-miR-7-5p, EMP2-hsa-miR-1290, TMEM2-hsa-miR-18a-5p, CTGF-hsa-miR-18a-5p, TNFAIP3-hsa-miR-18a-5p, THBS1-hsa-miR-182-5p, KPNA2-hsa-miR-144-3p, GPR137C-hsa-miR-1-3p, GRIK3-hsa-miR-144-3p, and MTHFD2-hsa-miR-30a-3p) were identified in SCLC.RBMS3, NEDD9, CRIM1, KPNA2, GPR137C, GRIK3, hsa-miR-7-5p, hsa-miR-18a-5p, hsa-miR-144-3p, hsa-miR-1-3p along with the pathways included protein kinase B signaling, muscle structure development, Cell Cycle (Mitotic) and blood vessel development may gain a high chance to play a key role in the prognosis of SCLC, but more studies should be conducted to reveal it more clearly.

SIRT4 prevents excitotoxicity via modulating glutamate metabolism in glioma cells

Excitotoxicity is the presence of excessive glutamate, which is normally taken up by glutamate transporters on astrocytes. Glutamate transporter 1 (GLT-1) is the major transporter on glia cells clearing more than 90% of the glutamate. Sirtuin 4 (SIRT4) is a mitochondrial sirtuin which is expressed in the brain. Previously, it was shown that loss of SIRT4 leads to a more severe reaction to kainic acid, an excitotoxic agent, and also decreased GLT-1 expression in the brain. In this study, we aimed to investigate whether overexpression of SIRT4 is protective against excitotoxicity in glia cells. We overexpressed SIRT4 in A172 glioma cell line and treated with kainic acid in order to induce excitotoxicity. We observed that SIRT4 overexpression increased the cell viability after kainic acid treatment. In addition, reduced glutamate was detected in glutamate assay with overexpression of SIRT4 after kainic acid treatment since SIRT4 decreased cell death by preventing excitotoxicity. Our results show that overexpression of SIRT4 increased the protein levels of GLT-1 and glutamate dehydrogenase (GDH) after kainic acid (KA) treatment so that excess glutamate can be absorbed. However, overexpression of SIRT4 decreased glutamine synthetase (GS) levels. These results demonstrate that, by inhibiting GS, SIRT4 prevents glutamine formation, which will be converted to glutamate in neurons. SIRT4 prevents excitotoxicity via upregulating glutamate metabolism. Finally, our results may show that SIRT4 might prevent excitotoxicity and related cell death via reducing GS expression and upregulating GLT-1 and GDH levels. Therefore, it is important to develop therapeutics against excitotoxicity through SIRT4-related pathways in the cell.

GRM4 inhibits the proliferation, migration, and invasion of human osteosarcoma cells through interaction with CBX4

In recent years, the survey of metabolic glutamate receptor 4 (GRM4) in tumor biology has been gradually concerned. There are currently few studies on GRM4 in osteosarcoma, and the biological function is not clear. Analysis of TCGA database showed that there was no substantial deviation in the expression of GRM4 between osteosarcoma and normal tissues. In the subsequent experiments, there is no significant difference in either mRNA or protein levels among immortalized human osteoblasts and various osteosarcoma cells. With the overexpression of GRM4, cell proliferation, migration and invasion were inhibited obviously. It was further revealed that GRM4 can interact with CBX4 to restrict the nuclear localization of CBX4 and affect the transcriptional activity of HIF-1α. This is the evidence supporting the interaction between GRM4 and CBX4, which could inhibit the malignant behavior of osteosarcoma cells through the GRM4/CBX4/HIF-1α signaling pathway.

Ca2+ Channel Toolkit in Neuroendocrine Tumors

Neuroendocrine tumors (NET) constitute a heterogeneous group of malignancies with various clinical presentations and growth rates but a common origin in neuroendocrine cells located all over the body. NET are a relatively low-frequency disease mostly represented by gastroenteropancreatic (GEP) and bronchopulmonary tumors (pNET); on the other hand, an increasing frequency and prevalence have been associated with NET. Despite great efforts in recent years, the management of NET is still a critical unmet need due to the lack of knowledge of the biology of the disease, the lack of adequate biomarkers, late presentation, the relative insensitivity of imaging modalities, and a paucity of predictably effective treatment options. In this context Ca2+ signals, being pivotal molecular devices in sensing and integrating signals from the microenvironment, are emerging to be particularly relevant in cancer, where they mediate interactions between tumor cells and the tumor microenvironment to drive different aspects of neoplastic progression (e.g., cell proliferation and survival, cell invasiveness, and proangiogenetic programs). Indeed, ion channels represent good potential pharmacological targets due to their location on the plasma membrane, where they can be easily accessed by drugs. The present review aims to provide a critical and up-to-date overview of NET development integrating Ca2+ signal involvement. In this perspective, we first give an introduction to NET and Ca2+ channels and then describe the different families of Ca2+ channels implicated in NET, i.e., ionotropic receptors, voltage-dependent Ca2+ channels, and transient receptor potential channels, as well as intracellular Ca2+ channels and their signaling molecules.

NMDAR PAMs: Multiple Chemotypes for Multiple Binding Sites

The N-methyl-D-aspartate receptor (NMDAR) is a member of the ionotropic glutamate receptor (iGluR) family that plays a crucial role in brain signalling and development. NMDARs are nonselective cation channels that are involved with the propagation of excitatory neurotransmission signals with important effects on synaptic plasticity. NMDARs are functionally and structurally complex receptors, they exist as a family of subtypes each with its own unique pharmacological properties. Their implication in a variety of neurological and psychiatric conditions means they have been a focus of research for many decades. Disruption of NMDAR-related signalling is known to adversely affect higherorder cognitive functions (e.g. learning and memory) and the search for molecules that can recover (or even enhance) receptor output is a current strategy for CNS drug discovery. A number of positive allosteric modulators (PAMs) that specifically attempt to overcome NMDAR hypofunction have been discovered. They include various chemotypes that have been found to bind to several different binding sites within the receptor. The heterogeneity of chemotype, binding site and NMDAR subtype provide a broad landscape of ongoing opportunities to uncover new features of NMDAR pharmacology. Research on NMDARs continues to provide novel mechanistic insights into receptor activation and this review will provide a high-level overview of the research area and discuss the various chemical classes of PAMs discovered so far.

Transcriptional modulation of calcium-permeable AMPA receptor subunits in glioblastoma by MEK-ERK1/2 inhibitors and their role in invasion

Glioblastoma is the most common primary brain tumor. Glioblastoma cells secrete a significant amount of glutamate, which serve as a potential growth factor in glioma pathobiology through their specific receptor subtypes including α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR). Glioblastoma express AMPAR subunits; however, its regulation and activation with downstream intracellular signaling are not well-understood. Phosphorylated-extracellular signaling-regulated kinase (ERK)1/2 is known to regulate the ionotropic glutamate receptors in cortical neurons. The mitogen-activated protein kinase cascade is frequently activated in several tumors, including glioma. Nonetheless, the association of ERK signaling with AMPAR subunits in glioblastoma is undetermined. Here, we demonstrated potential role of AMPAR in invasion, and the modulation of AMPAR subunits at transcript level by ERK signaling in glioblastoma cells. Inhibition of ERK signaling specifically downregulated the expression of calcium-permeable AMPAR subunits, GluA1 and GluA4, and upregulated calcium-impermeable AMPAR subunit GluA2 implying differential regulation of the expression of calcium-permeable AMPAR subunits of glioblastoma. Concomitantly, it significantly decreased the invasion of U87MG cells. Taken together, these findings suggest that the AMPAR enhances invasion of glioblastoma, and ERK signaling modulates the differential expression of calcium-permeable AMPAR phenotype that might play a crucial role in the invasive propensity of glioblastoma cells.

Survival of glioblastoma cells in response to endogenous and exogenous oxidative challenges: possible implication of NMDA receptor-mediated regulation of redox homeostasis

Cancer cells are highly metabolically active and produce high levels of reactive oxygen species (ROS). Drug resistance in cancer cells is closely related to their redox status. The role of ROS and its impact on cancer cell survival seems far from elucidation. The mechanisms through which glioblastoma cells overcome aberrant ROS and oxidative stress in a milieu of hypermetabolic state is still elusive. We hypothesize that the formidable growth potential of glioma cells is through manipulation of tumor microenvironment for its survival and growth, which can be attributed to an astute redox regulation through a nexus between activation of N-methyl-d-aspartate receptor (NMDAR) and glutathione (GSH)-based antioxidant prowess. Hence, we examined the NMDAR activation on intracellular ROS level, and cell viability on exposure to hydrogen peroxide (H₂ O₂ ), and antioxidants in glutamate-rich microenvironment of glioblastoma. The activation of NMDAR attenuated the intracellular ROS production in LN18 and U251MG glioma cells. MK-801 significantly reversed this effect. On evaluation of GSH redox cycle in these cells, the level of reduced GSH and glutathione reductase (GR) activity were significantly increased. NMDAR significantly enhanced the cell viability in LN18 and U251MG glioblastoma cells, by attenuating exogenous H₂ O₂ -induced oxidative stress, and significantly increased catalase activity, the key antioxidant that detoxifies H₂ O₂ . We hereby report an unexplored role of NMDAR activation induced protection of the rapidly multiplying glioblastoma cells against both endogenous ROS as well as exogenous oxidative challenges. We propose potentiation of reduced GSH, GR, and catalase in glioblastoma cells through NMDAR as a novel rationale of chemoresistance in glioblastoma.

Sodium homeostasis in the tumour microenvironment

The concentration of sodium ions (Na+) is raised in solid tumours and can be measured at the cellular, tissue and patient levels. At the cellular level, the Na+ gradient across the membrane powers the transport of H+ ions and essential nutrients for normal activity. The maintenance of the Na+ gradient requires a large proportion of the cell's ATP. Na+ is a major contributor to the osmolarity of the tumour microenvironment, which affects cell volume and metabolism as well as immune function. Here, we review evidence indicating that Na+ handling is altered in tumours, explore our current understanding of the mechanisms that may underlie these alterations and consider the potential consequences for cancer progression. Dysregulated Na+ balance in tumours may open opportunities for new imaging biomarkers and re-purposing of drugs for treatment.

Osteosarcoma growth suppression by riluzole delivery via iron oxide nanocage in nude mice

Osteosarcomas are the most commonly occurring malignant bone cancer in young individuals. The survival rate of patients with metastatic osteosarcoma is low and has been stagnant for over two decades. We previously demonstrated that the glutamate release inhibitor, riluzole inhibits osteosarcoma cell growth. Towards the development of more effective therapy, we investigated the delivery of riluzole in human metastatic osteosarcoma xenografts in mice. We compared the efficacy of riluzole delivery by intraperitoneally injecting either free riluzole or riluzole released via two different shapes of iron oxide nanoparticles (nanocage or nanosphere) of size 15±2.5 nm. We monitored tumor size using Vernier calipers and bioluminescence assay and found a significant reduction in tumor size in the riluzole-treated groups when injected, either in free form or via nanoparticles, compared to the control groups (PBS, nanosphere or nanocage). Importantly, nanocage-delivered riluzole was most effective in reducing tumor size in the xenograft nude mice. While riluzole delivery induced apoptosis in tumor tissues in all three groups of riluzole-treated animals, it was highest in tumors from the nanocage-delivered riluzole group. Therefore, we conclude that riluzole is an effective drug to reduce tumor size in osteosarcoma and the efficacy of riluzole as a apoptotic and tumor-reducing drug is enhanced when delivered via nanocage.

Glutamate in cancers: from metabolism to signaling

Glutamine and glutamate are major bioenergy substrates for normal and cancer cell growth. Cancer cells need more biofuel than normal tissues for energy supply, anti-oxidation activity and biomass production. Genes related to metabolic chains in many cancers are somehow mutated, which makes cancer cells more glutamate dependent. Meanwhile, glutamate is an excitatory neurotransmitter for conducting signals through binding with different types of receptors in central neuron system. Interestingly, increasing evidences have shown involvement of glutamate signaling, guided through their receptors, in human malignancy. Dysregulation of glutamate transporters, such as excitatory amino acid transporter and cystine/glutamate antiporter system, also generates excessive extracellular glutamate, which in turn, activates glutamate receptors on cancer cells and results in malignant growth. These features make glutamate an attractive target for anti-cancer drug development with some glutamate targeted but blood brain barrier impermeable anti-psychosis drugs under consideration. We discussed the relevant progressions and drawbacks in this field herein.

Glutamate Ionotropic Receptor Kainate Type Subunit 3 (GRIK3) promotes epithelial-mesenchymal transition in breast cancer cells by regulating SPDEF/CDH1 signaling

Glutamate Ionotropic Receptor Kainate Type Subunit 3 (GRIK3) is an important excitatory neurotransmitter receptor that plays a significant role in various neurodegenerative diseases. However, the biological functions of GRIK3 in malignancies are largely unknown because of limited related studies. Here, we primarily reported that the expression of GRIK3 was higher in breast cancer tissues than in adjacent noncancerous tissues. GRIK3 expression was also positively correlated with the prognosis of patients with breast cancer. GRIK3 promoted the proliferation and migration abilities of breast cancer cells and enhanced the growth of orthotopically implanted tumors. Mechanically, GRIK3 influenced a range of signaling pathways and key signal transducers, including two epithelial-mesenchymal transition regulators, SPDEF and CDH1. Heterogenous expression of SPDEF and CDH1 counteracted the migration and invasion abilities, respectively, of breast cancer cells induced by GRIK3. Moreover, overexpression of GRIK3 increased the expression of mesenchymal markers and decreased the expression of epithelial markers, resulting in the translocation of β-catenin into the nucleus and the increased β-catenin transcriptional activity. In conclusion, the present study reported a novel oncogenic role of GRIK3. Meanwhile, GRIK3, as a membrane receptor, may also serve as a potential therapeutic target for the treatment of breast cancer.

NMDA Receptor-Mediated Signaling Pathways Enhance Radiation Resistance, Survival and Migration in Glioblastoma Cells-A Potential Target for Adjuvant Radiotherapy

Glioblastoma is one of the most aggressive malignant brain tumors, with a survival time less than 15 months and characterized by a high radioresistance and the property of infiltrating the brain. Recent data indicate that the malignancy of glioblastomas depends on glutamatergic signaling via ionotropic glutamate receptors. In this study we revealed functional expression of Ca²⁺-permeable NMDARs in three glioblastoma cell lines. Therefore, we investigated the impact of this receptor on cell survival, migration and DNA double-strand break (DSB) repair in the presence of both, glutamate and NMDAR antagonists, and after clinically relevant doses of ionizing radiation. Our results indicate that treatment with NMDAR antagonists slowed the growth and migration of glutamate-releasing LN229 cells, suggesting that activation of NMDARs facilitate tumor expansion. Furthermore, we found that DSB-repair upon radiation was more effective in the presence of glutamate. In contrast, antagonizing the NMDAR or the Ca²⁺-dependent transcription factor CREB impaired DSB-repair similarly and resulted in a radiosensitizing effect in LN229 and U-87MG cells, indicating a common link between NMDAR signaling and CREB activity in glioblastoma. Since the FDA-approved NMDAR antagonists memantine and ifenprodil showed differential radiosensitizing effects, these compounds may constitute novel optimizations for therapeutic interventions in glioblastoma.