Association of elevated glial expression of interleukin-1beta with improved survival in patients with glioblastomas multiforme

Fluoride in the Central Nervous System and Its Potential Influence on the Development and Invasiveness of Brain Tumours-A Research Hypothesis

The purpose of this review is to attempt to outline the potential role of fluoride in the pathogenesis of brain tumours, including glioblastoma (GBM). In this paper, we show for the first time that fluoride can potentially affect the generally accepted signalling pathways implicated in the formation and clinical course of GBM. Fluorine compounds easily cross the blood-brain barrier. Enhanced oxidative stress, disruption of multiple cellular pathways, and microglial activation are just a few examples of recent reports on the role of fluoride in the central nervous system (CNS). We sought to present the key mechanisms underlying the development and invasiveness of GBM, as well as evidence on the current state of knowledge about the pleiotropic, direct, or indirect involvement of fluoride in the regulation of these mechanisms in various tissues, including neural and tumour tissue. The effects of fluoride on the human body are still a matter of controversy. However, given the growing incidence of brain tumours, especially in children, and numerous reports on the effects of fluoride on the CNS, it is worth taking a closer look at these mechanisms in the context of brain tumours, including gliomas.

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.

Demeclocycline Reduces the Growth of Human Brain Tumor-Initiating Cells: Direct Activity and Through Monocytes

Myeloid cells that infiltrate into brain tumors are deactivated or exploited by the tumor cells. We previously demonstrated that compromised microglia, monocytes, and macrophages in malignant gliomas could be reactivated by amphotericin-B to contain the growth of brain tumorinitiating cells (BTICs). We identified meclocycline as another activator of microglia, so we sought to test whether its better-tolerated derivative, demeclocycline, also stimulates monocytes to restrict BTIC growth. Monocytes were selected for study as they would be exposed to demeclocycline in the circulation prior to entry into brain tumors to become macrophages. We found that demeclocycline increased the activity of monocytes in culture, as determined by tumor necrosis factor-α production and chemotactic capacity. The conditioned medium of demeclocycline-stimulated monocytes attenuated the growth of BTICs generated from human glioblastoma resections, as evaluated using neurosphere and alamarBlue assays, and cell counts. Demeclocycline also had direct effects in reducing BTIC growth. A global gene expression screen identified several genes, such as DNA damage inducible transcript 4, frizzled class receptor 5 and reactive oxygen species modulator 1, as potential regulators of demeclocycline-mediated BTIC growth reduction. Amongst several tetracycline derivatives, only demeclocycline directly reduced BTIC growth. In summary, we have identified demeclocycline as a novel inhibitor of the growth of BTICs, through direct effect and through indirect stimulation of monocytes. Demeclocycline is a candidate to reactivate compromised immune cells to improve the prognosis of patients with gliomas.

Prognostic Significance of Preoperative Systemic Cellular Inflammatory Markers in Gliomas: A Systematic Review and Meta-Analysis

Glioma is the most common malignant brain tumor and has high lethality. This tumor generated a robust inflammatory response that results in the deterioration of the disease. However, the prognostic role of systemic cellular inflammatory indicators in gliomas remains controversial. This meta‐analysis aimed to assess the prognostic significance of preoperative neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), lymphocyte/monocyte ratio (LMR), red cell distribution width (RDW), and prognostic nutritional index (PNI) in patients with gliomas. Databases of PubMed, EMBASE, Web of Science, and The Cochrane Library were systematically searched for all studies published up to January 2019. Study screening and data extraction followed established Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines. The Newcastle–Ottawa Scale was used to assess the quality of studies. Eighteen studies containing 3,261 patients were included. The analyses showed an increased NLR or RDW was found to be an independent predictor of worse survival in patients with gliomas (hazard ratio (HR): 1.38; 95% confidence interval (CI): 1.09–1.74; P = 0.008; and HR: 1.40; 95% CI: 1.13–1.74; P = 0.002, respectively). Furthermore, a higher PNI indicates a better overall survival (OS; HR: 0.57; 95% CI: 0.42–0.77; P = 0.0002). For the evaluation of PLR and LMR, none of these variables correlated with OS (P = 0.91 and P = 0.21, respectively). Our meta‐analysis indicates the NLR, RDW, and PNI rather than PLR and LMR are the independent index for predicting the OS of gliomas. Pre‐operative NLR, RDW, and PNI can help to evaluate disease progression, optimize treatment, and follow‐up in patients with gliomas.

Mining TCGA database for genes of prognostic value in glioblastoma microenvironment

Glioblastoma (GBM) is one of the most deadly brain tumors. The convenient access to The Cancer Genome Atlas (TCGA) database allows for large-scale global gene expression profiling and database mining for potential correlation between genes and overall survival of a variety of malignancies including GBM. Previous reports have shown that tumor microenvironment cells and the extent of infiltrating immune and stromal cells in tumors contribute significantly to prognosis. Immune scores and stromal scores calculated based on the ESTIMATE algorithm could facilitate the quantification of the immune and stromal components in a tumor. To better understand the effects of genes involved in immune and stromal cells on prognosis, we categorized GBM cases in the TCGA database according to their immune/stromal scores into high and low score groups, and identified differentially expressed genes whose expression was significantly associated with prognosis in GBM patients. Functional enrichment analysis and protein-protein interaction networks further showed that these genes mainly participated in immune response, extracellular matrix, and cell adhesion. Finally, we validated these genes in an independent GBM cohort from the Chinese Glioma Genome Atlas (CGGA). Thus, we obtained a list of tumor microenvironment-related genes that predict poor outcomes in GBM patients.

The role of microglia and P2X7 receptors in gliomas

Gliomas are the most prevalent tumours of the central nervous system and present with high morbidity and mortality. The most common and most aggressive form of glioma is glioblastoma multiforme, of which patients have a median survival time of only 12 to 15 months. Current treatment options are limited and have a small impact on clinical outcome and prognosis. There is accumulating evidence that microglia, the immunocompetent cells of the central nervous system, and the purinergic P2X7 receptor (P2X7R) may contribute to tumour progression and pathology. Importantly, P2X7R on both tumour cells and infiltrating microglia is overexpressed in animal and human glioma cultures. Factors released by glioma cells and P2X7R activation recruit microglia into the largely immunosuppressive tumour microenvironment where they have been demonstrated to contribute to either tumour proliferation or tumour suppression. It is likely that P2X7R mediates a range of microglia effector functions in the glioma setting, potentially increasing tumour growth and proliferation. This review evaluates current evidence on the roles of microglia and P2X7R in glioma pathogenesis. Understanding the nature, mechanisms and outcomes of microglia and P2X7R activation in gliomas is necessary for the development of more therapies with increased efficacy and specificity.

Importance of GFAP isoform-specific analyses in astrocytoma

Gliomas are a heterogenous group of malignant primary brain tumors that arise from glia cells or their progenitors and rely on accurate diagnosis for prognosis and treatment strategies. Although recent developments in the molecular biology of glioma have improved diagnosis, classical histological methods and biomarkers are still being used. The glial fibrillary acidic protein (GFAP) is a classical marker of astrocytoma, both in clinical and experimental settings. GFAP is used to determine glial differentiation, which is associated with a less malignant tumor. However, since GFAP is not only expressed by mature astrocytes but also by radial glia during development and neural stem cells in the adult brain, we hypothesized that GFAP expression in astrocytoma might not be a direct indication of glial differentiation and a less malignant phenotype. Therefore, we here review all existing literature from 1972 up to 2018 on GFAP expression in astrocytoma patient material to revisit GFAP as a marker of lower grade, more differentiated astrocytoma. We conclude that GFAP is heterogeneously expressed in astrocytoma, which most likely masks a consistent correlation of GFAP expression to astrocytoma malignancy grade. The GFAP positive cell population contains cells with differences in morphology, function, and differentiation state showing that GFAP is not merely a marker of less malignant and more differentiated astrocytoma. We suggest that discriminating between the GFAP isoforms GFAPδ and GFAPα will improve the accuracy of assessing the differentiation state of astrocytoma in clinical and experimental settings and will benefit glioma classification.

Role of NOD- like Receptors in Glioma Angiogenesis: Insights into future therapeutic interventions

Gliomas are the most common solid tumors among central nervous system tumors. Most glioma patients succumb to their disease within two years of the initial diagnosis. The median survival of gliomas is only 14.6 months, even after aggressive therapy with surgery, radiation, and chemotherapy. Gliomas are heavily infiltrated with myeloid- derived cells and endothelial cells. Increasing evidence suggests that these myeloid- derived cells interact with tumor cells promoting their growth and migration. NLRs (nucleotide-binding oligomerization domain (NOD)-containing protein like receptors) are a class of pattern recognition receptors that are critical to sensing pathogen and danger associated molecular patterns. Mutations in some NLRs lead to autoinflammatory diseases in humans. Moreover, dysregulated NLR signaling is central to the pathogenesis of several cancers, autoimmune and neurodegenerative diseases. Our review explores the role of angiogenic factors that contribute to upstream or downstream signaling pathways leading to NLRs. Angiogenesis plays a significant role in the pathogenesis of variety of tumors including gliomas. Though NLRs have been detected in several cancers including gliomas and NLR signaling contributes to angiogenesis, the exact role and mechanism of involvement of NLRs in glioma angiogenesis remain largely unexplored. We discuss cellular, molecular and genetic studies of NLR signaling and convergence of NLR signaling pathways with angiogenesis signaling in gliomas. This may lead to re-appropriation of existing anti-angiogenic therapies or development of future strategies for targeted therapeutics in gliomas.

Interleukin-1β promotes hypoxia-induced apoptosis of glioblastoma cells by inhibiting hypoxia-inducible factor-1 mediated adrenomedullin production

Glioblastoma is the most common brain tumor in adults. Advanced glioblastomas normally contain hypoxic areas. The primary cellular responses to hypoxia are generally mediated by the transcription factor hypoxia-inducible factor 1 (HIF-1). Interleukin-1β (IL-1β) is a cytokine that is often present in the glioblastoma microenvironment and is known to be a modulator of glioblastoma progression. However, the role of IL-1β in regulating glioblastoma progression is still controversial. In this study, we found that in the human glioblastoma cell lines U87MG and U138MG, IL-1β inhibits the transactivation activity of HIF-1 by promoting the ubiquitin-independent proteasomal degradation of the oxygen-labile α-subunit of HIF-1 and downregulates the expression of the HIF-1 target gene adrenomedullin (AM). Apoptosis and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assays showed that AM protects glioblastoma cells against hypoxia-induced apoptosis in a dose-dependent manner. Thus, in the presence of IL-1β more glioblastoma cells undergo hypoxia-induced cell death. Our findings suggest that when estimating the influence of IL-1β on the prognosis of glioblastoma patients, factors such as the degree of hypoxia, the expression levels of HIF-1 and AM should be taken into consideration. For the AM-producing glioblastoma cells, IL-1β represents a potent apoptosis inducer.

Restoring soluble guanylyl cyclase expression and function blocks the aggressive course of glioma

The NO and cGMP signaling pathways are of broad physiological and pathological significance. We compared the NO/soluble guanylyl cyclase (sGC)/cGMP pathway in human glioma tissues and cell lines with that of healthy control samples and demonstrated that sGC expression is significantly lower in glioma preparations. Our analysis of GEO databases (National Cancer Institute) further revealed a statistically significant reduction of sGC transcript levels in human glioma specimens. On the other hand, the expression levels of particulate (membrane) guanylyl cyclases (pGC) and cGMP-specific phosphodiesterase (PDE) were intact in the glioma cells that we have tested. Pharmacologically manipulating endogenous cGMP generation in glioma cells through either stimulating pGC by ANP/BNP, or blocking PDE by 3-isobutyl-1-methylxanthine/zaprinast caused significant inhibition of proliferation and colony formation of glioma cells. Genetically restoring sGC expression also correlated inversely with glioma cells growth. Orthotopic implantation of glioma cells transfected with an active mutant form of sGC (sGCα1β1(Cys105)) in athymic mice increased the survival time by 4-fold over the control. Histological analysis of xenografts overexpressing α1β1(Cys105) sGC revealed changes in cellular architecture that resemble the morphology of normal cells. In addition, a decrease in angiogenesis contributed to glioma inhibition by sGC/cGMP therapy. Our study proposes the new concept that suppressed expression of sGC, a key enzyme in the NO/cGMP pathway, may be associated with an aggressive course of glioma. The sGC/cGMP signaling-targeted therapy may be a favorable alternative to chemotherapy and radiotherapy for glioma and perhaps other tumors.

Cytokine expression profile in human pancreatic carcinoma cells and in surgical specimens: implications for survival

Cytokine shedding by tumor cells into the local microenvironment modulates host immune response, tumor growth, and metastasis. The study aimed to verify the hypothesis that the immunological microenvironment of pancreatic carcinoma exists in a prevalently immunosuppressive state, influencing survival. We analyzed expression profiles of pro-inflammatory (IL-1beta, IL-2, IL-6, IL-8, IL-12 p40, IL-18 and IFN-gamma) and anti-inflammatory (IL-10, IL-11, IL-13 and TGF-beta isoforms) cytokines. The study was performed both in vitro, in five pancreatic carcinoma cell lines (real time RT-PCR), and in specimens from 65 patients, comparing tumoral versus non-tumoral pancreatic tissues (real time RT-PCR and immunohistochemistry). Furthermore, cytokines were measured in supernatants and sera (from patients and controls) by ELISA. All cell lines expressed IL-8, IL-18, TGF-beta1, TGF-beta2 and TGF-beta3, but not IFN-gamma and IL-2 transcripts. Expression of IL-1beta, IL-6, IL-10, IL-11, IL-13 and IL-12 mRNA was variable. All the above cytokines were detected as soluble proteins in supernatants, except IL-13. Tumor tissues overexpressed IL-1beta, IL-6, IL-8, IL-10, IL-11, IL-12 p40, IL-18, IFN-gamma, TGF-beta1, TGF-beta2 and TGF-beta3 at the mRNA level and IL-1beta, IL-18, TGF-beta2 and TGF-beta3 also at the protein level. Conversely, non-tumor tissues had stronger RNA and protein expression of IL-13. Survival was significantly longer in patients with high IL-1beta and IL-11 and moderate IL-12 expression. Serum IL-8, IL-10, IL-12, IL-18, TGF-beta1 and TGF-beta2 were higher in patients than in controls, as opposed to IL-1beta and IL-13. Patients with low circulating levels of IL-6, IL-18 and TGF-beta2 survived longer. Pancreatic cancer is characterized by peculiar cytokine expression patterns, associated with different survival probabilities.

Aberrant methylation and down-regulation of TMS1/ASC in human glioblastoma

TMS1/ASC is an intracellular signaling molecule with proposed roles in the regulation of apoptosis, nuclear factor-kappaB activation, and cytokine maturation. Previous studies have shown that TMS1/ASC is silenced by epigenetic means in human breast tumors. In this study, we examined methylation and expression of TMS1/ASC in glioblastoma multiforme (GBM). Whereas normal brain tissue was unmethylated at the TMS1 locus and expressed TMS1 message, 11 of 23 human GBM cell lines exhibited reduced or absent expression of TMS1 that was associated with aberrant methylation of a CpG island in the promoter of the TMS1 gene. Quantitative analysis showed that there was an inverse correlation between the degree of methylation and level of TMS1 expression. Treatment of GBM cell lines lacking TMS1 expression with the methyltransferase inhibitor 5-aza-2'deoxycytidine resulted in partial demethylation and re-expression of TMS1. Analysis of primary tissues indicated that the TMS1 gene is unmethylated and expressed in normal brain, where its expression is restricted to astrocytes. In contrast, TMS1 was aberrantly methylated in 43% (10 of 23) primary GBM specimens. Tumors that exhibited aberrant methylation of TMS1 generally expressed reduced or absent expression of TMS1 as compared to unmethylated cases. Methylation of TMS1 was not associated with patient age, gender, or treatment status. Although the relationship did not reach statistical significance, there was a trend toward increased overall survival for patients with unmethylated tumors. For one patient, disease progression from astrocytic astrocytoma (World Health Organization grade III) to GBM (World Health Organization grade IV) was associated with selective expansion of TMS1-negative cells. The data suggest a role for the epigenetic silencing of TMS1 in the pathogenesis of human GBM. Methylation of TMS1 may prove to be a useful prognostic marker and/or predictor of patient survival and tumor malignancy.

Intratumoral infusion of interleukin-1β and interferon-γ induces tumor invasion with macrophages and lymphocytes in a rat glioma model

Malignant gliomas are hard to treat successfully. Like other treatments immune therapy fails presumably due to low concentration of immune modifiers within the tumor. However, convection-enhanced delivery (CED) may overcome this problem. So, we analyzed the effect of intratumoral delivery of interleukin (IL)-1beta and interferon (IFN)-gamma by CED on tumor immune cell invasion in a rat glioma model. Tumors were implanted into the left caudate nucleus and tumor growth was demonstrated by MRI. Afterwards intratumoral infusion of IL-1beta or IFN-gamma was started for 48 h. Then animals were sacrificed and the number of tumor infiltrating CD4+ and CD8+ lymphocytes as well as macrophages was analyzed by immunohistochemistry. Our results demonstrate that intratumoral cytokine infusion using CED leads to a strong tumor invasion with macrophages and lymphocytes suggesting a tumor specific immune response.

Time-course of the expression of inflammatory cytokines and matrix metalloproteinases in the striatum and mesencephalon of mice injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a dopaminergic neurotoxin

Injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice results in a retrograde nigrostriatal dopaminergic pathway denervation and subsequent tissue reorganization. Since the role of inflammatory mediators after MPTP remains unclear, proinflammatory cytokine and matrix metalloproteinase (MMP) expression were evaluated by comparative RT-PCR during denervation and tissue reorganization following a single-dose of MPTP (40 mg/kg, s.c.) in young (8-week-old) mice. The time-course of denervation/reorganization was assessed through [(3)H]GBR-12935 binding on dopamine transporter and tyrosine hydroxylase immunohistochemistry. In the striatum, TNF-alpha, IL-1alpha, IL-1beta, IL-6 and MMP-9 mRNA expression peaked on day 1. In the ventral mesencephalon, cytokines (TNF-alpha, IL-1alpha, IL-1beta) and MMP-9 mRNA expression peaked on day 3. During tissue reorganization (day 6 through 16), the only change observed in the striatum consisted of IL-1alpha mRNA and protein overexpression together with MMP-2 downregulation. Whereas the early expression of proinflammatory cytokines and MMP might participate in the retrograde nigrostriatal denervation, the late component of IL-1alpha expression suggests a possible role for this cytokine in the subsequent striatal reorganization.

Immunotherapy and biological modifiers for the treatment of malignant brain tumors

The relative ineffectiveness of current therapies for malignant gliomas has led to the need for novel therapeutics. Therapies based on biologic modifiers are among a variety of cancer treatments currently in use or under experimental evaluation and have shown great promise, especially since several potent stimulators of the immune system have been cloned and are now available for clinical use. Early attempts at glioma therapy based on biologic modifiers, however, have failed to demonstrate significant effectiveness. In this review, we select and summarize the results of preclinical and clinical studies published during the past two years that focus on immunotherapy and biologic modifiers for treating gliomas. Despite limited clinical success, we conclude that an increased understanding of molecular biology and immunology from recent studies may pave the way for more effective approaches.

Microglia in brain tumors

Microglia have long been ignored by neurooncologists. This has changed with the realization that microglial cells not only occur within and around brain tumors but also contribute significantly to the actual tumor mass, notably in astrocytic gliomas. In addition, it has been speculated that microglia could play a role in the defense against neoplasms of the nervous system. However, the biological success of these tumors, i.e., their highly malignant behavior, indicates that natural microglial defense mechanisms do not function properly in astrocytomas. In fact, there is evidence that microglial behavior is controlled by tumor cells, supporting their growth and infiltration. This unexpected "Achilles heel" of microglial immune defense illustrates the risk of generalizing on the basis of a single aspect of microglial biology. Microglia are highly plastic cells, capable of exerting cytotoxic functions under conditions of CNS infections, but not necessarily during glioma progression. Thus, the suggestion that microglial activation through stimulation by cytokines (e.g., interferon-gamma) will benefit patients with brain tumors could prove fatally wrong. Therapeutic recruitment of microglia to treat such diffusely infiltrative brain tumors as astrocytic gliomas must be considered premature.