Glioma revisited: from neurogenesis and cancer stem cells to the epigenetic regulation of the niche. J Oncol. 2012;2012:537861. [PMID: 22973309 PMCID: PMC3438806 DOI: 10.1155/2012/537861]

Modular Hub Genes in DNA Microarray Suggest Potential Signaling Pathway Interconnectivity in Various Glioma Grades

Gliomas have displayed significant challenges in oncology due to their high degree of invasiveness, recurrence, and resistance to treatment strategies. In this work, the key hub genes mainly associated with different grades of glioma, which were represented by pilocytic astrocytoma (PA), oligodendroglioma (OG), anaplastic astrocytoma (AA), and glioblastoma multiforme (GBM), were identified through weighted gene co-expression network analysis (WGCNA) of microarray datasets retrieved from the Gene Expression Omnibus (GEO) database. Through this, four highly correlated modules were observed to be present across the PA (GSE50161), OG (GSE4290), AA (GSE43378), and GBM (GSE36245) datasets. The functional annotation and pathway enrichment analysis done through the Database for Annotation, Visualization, and Integrated Discovery (DAVID) showed that the modules and hub genes identified were mainly involved in signal transduction, transcription regulation, and protein binding, which collectively deregulate several signaling pathways, mainly PI3K/Akt and metabolic pathways. The involvement of several hub genes primarily linked to other signaling pathways, including the cAMP, MAPK/ERK, Wnt/β-catenin, and calcium signaling pathways, indicates potential interconnectivity and influence on the PI3K/Akt pathway and, subsequently, glioma severity. The Drug Repurposing Encyclopedia (DRE) was used to screen for potential drugs based on the up- and downregulated hub genes, wherein the synthetic progestin hormones norgestimate and ethisterone were the top drug candidates. This shows the potential neuroprotective effect of progesterone against glioma due to its influence on EGFR expression and other signaling pathways. Aside from these, several experimental and approved drug candidates were also identified, which include an adrenergic receptor antagonist, a PPAR-γ receptor agonist, a CDK inhibitor, a sodium channel blocker, a bradykinin receptor antagonist, and a dopamine receptor agonist, which further highlights the gene network as a potential therapeutic avenue for glioma.

Fibroblast growth factor 2 is a druggable target against glioblastoma: A computational investigation

Fibroblast growth factor 2 (FGF2) is a key player in cancer and tissue homeostasis and regulates renewal of several stem cell types. The FGF2 role in malignant glioma is proven and tagged FGF2, a novel druggable target, is used for developing potent drugs against glioblastoma. In this study, Asinex 51412372, Asinex 51217461, and Asinex 51216586 were filtered to show the best binding affinity for FGF2 with binding energy scores of -8.3 kcal/mol, -8.2 kcal/mol, and -7.8 kcal/mol, respectively. The compounds showed chemical interactions with several vital residues of FGF2 along the compound length. The noticeable residues that interacted with the compounds were Arg15, Asp23, Arg63, and Gln105. In dynamic investigation in solution, the FGF2 reported unstable dynamics in the first 100 ns and gained structural equilibrium in the second phase of 100 ns. The maximum root mean square deviation (RMSD) value touched by the systems is 3 Å. Similarly, the residue flexibility of FGF2 in the presence of compounds was within a stable range and is compact along the simulation time length. The compounds showed robust atomic-level stable energies with FGF2, which are dominated by both van der Waals and electrostatic interactions. The net binding energy of systems varies between -40 kcal/mol and -86 kcal/mol, suggesting the formation of strong intermolecular docked complexes. The drug-likeness and pharmacokinetic properties also pointed toward good structures that are not toxic, have high gastric absorption, showed good distribution, and readily excreted from the body. In summary, the predicted compounds in this study might be ideal hits that might be further optimized for structure and activity during experimental studies.

Expression of CD133 Cancer Stem Cell Marker in IDH-Mutant and IDH-wildtype (Isocitrate Dehydrogenase) Astrocytoma

OBJECTIVE

This study evaluated the differences between IDH1-R132H and CD133 expression in different categories of  astrocytoma.

MATERIAL AND METHODS

This study used a cross-sectional design.  Sixty-seven paraffin embedded block of Diffuse Astrocytoma (DA), Anaplastic Astrocytoma (AA) and Glioblastoma (GB) were assessed using using the monoclonal antibody IDH1-R132H and Rabbit polyclonal antibody CD133.

RESULTS

It was found that there was a significant relationship between the expression of IDH1-R132H and CD133 in DA, AA and GB (p<0.001). Astrocytoma with IDH-mutant molecular status will express more markers of cancer stem cell CD133 than IDH-wildtype.

CONCLUSION

The IDH1-R132H and CD133 can provide predictive value on treatment success, disease prognosis, recurrence and can be considered as target combination therapy with chemotherapy.

Targeted inhibition of ubiquitin signaling reverses metabolic reprogramming and suppresses glioblastoma growth

Glioblastoma multiforme (GBM) is the most frequent and aggressive form of primary brain tumor in the adult population; its high recurrence rate and resistance to current therapeutics urgently demand a better therapy. Regulation of protein stability by the ubiquitin proteasome system (UPS) represents an important control mechanism of cell growth. UPS deregulation is mechanistically linked to the development and progression of a variety of human cancers, including GBM. Thus, the UPS represents a potentially valuable target for GBM treatment. Using an integrated approach that includes proteomics, transcriptomics and metabolic profiling, we identify praja2, a RING E3 ubiquitin ligase, as the key component of a signaling network that regulates GBM cell growth and metabolism. Praja2 is preferentially expressed in primary GBM lesions expressing the wild-type isocitrate dehydrogenase 1 gene (IDH1). Mechanistically, we found that praja2 ubiquitylates and degrades the kinase suppressor of Ras 2 (KSR2). As a consequence, praja2 restrains the activity of downstream AMP-dependent protein kinase in GBM cells and attenuates the oxidative metabolism. Delivery in the brain of siRNA targeting praja2 by transferrin-targeted self-assembling nanoparticles (SANPs) prevented KSR2 degradation and inhibited GBM growth, reducing the size of the tumor and prolonging the survival rate of treated mice. These data identify praja2 as an essential regulator of cancer cell metabolism, and as a potential therapeutic target to suppress GBM growth.

The E3 ubiquitin ligase praja2  is expressed in glioblastoma (GBM), targets the kinase suppressor of Ras 2 for degradation and attenuates oxidative metabolism. Nanoparticle-mediated delivery of praja2 siRNA to GBM-bearing mice reduces tumour size.

Runx1 promotes the development of glioma cells by regulating JAK-STAT signalling pathway

INTRODUCTION

Human glioma is known as the most frequent and primary malignant tumour of the central nervous system with high aggression and poor prognosis. Runx1 is essential for haematopoiesis and is associated with tumour progression in several types of cancers. Therefore, this study aimed to investigate the effect and the possible regulatory mechanisms of Runx1 in glioma.

MATERIAL AND METHODS

The expression of Runx1 in human glioma tissues was determined by qRT-PCR and immunohistochemistry (IHC). Subsequently, the effect of Runx1 on the glioma cell viability, migration, invasion and the protein level of p21, cyclin D1, MMP2, and MMP4 were detected by MTT, wound healing, transwell assays, and western blot, respectively, in U-138MG and U-251MG cell lines. We then explored the role of Runx1 in vivo by establishing a tumour-bearing mouse model.

RESULTS

The expression of Runx1 was significantly up-regulated in human glioma tissues and closely associated with tumour grade. Glioma patients with high Runx1 expression had decreased survival rate compared to those with low Runx1 level. Runx1 knockdown inhibited glioma cell viability, migration, invasion, and clone formation, while STAT3 suppressed these inhibitions. Moreover, Runx1 inhibited the activation of SOCS3/SOCS4 promoter, which in turn activated JAK/STAT3 signalling pathway. The tumour volume and weight of the siRunx1 group were lower than in the control group and the tumour mass grow more slowly as well.

CONCLUSIONS

Runx1 promotes the development of glioma cells via JAK/STAT signalling pathway by inhibiting the activation of SOCS3/SOCS4 promoter.

Targeting Protein Kinase C in Glioblastoma Treatment

Glioblastoma (GBM) is the most frequent and aggressive primary brain tumor and is associated with a poor prognosis. Despite the use of combined treatment approaches, recurrence is almost inevitable and survival longer than 14 or 15 months after diagnosis is low. It is therefore necessary to identify new therapeutic targets to fight GBM progression and recurrence. Some publications have pointed out the role of glioma stem cells (GSCs) as the origin of GBM. These cells, with characteristics of neural stem cells (NSC) present in physiological neurogenic niches, have been proposed as being responsible for the high resistance of GBM to current treatments such as temozolomide (TMZ). The protein Kinase C (PKC) family members play an essential role in transducing signals related with cell cycle entrance, differentiation and apoptosis in NSC and participate in distinct signaling cascades that determine NSC and GSC dynamics. Thus, PKC could be a suitable druggable target to treat recurrent GBM. Clinical trials have tested the efficacy of PKCβ inhibitors, and preclinical studies have focused on other PKC isozymes. Here, we discuss the idea that other PKC isozymes may also be involved in GBM progression and that the development of a new generation of effective drugs should consider the balance between the activation of different PKC subtypes.

Cancer Stem Cells: Significance in Origin, Pathogenesis and Treatment of Glioblastoma

Cancer stem cells (CSCs), known also as tumor-initiating cells, are quiescent, pluripotent, self-renewing neoplastic cells that were first identified in hematologic tumors and soon after in solid malignancies. CSCs have attracted remarkable research interest due to their role in tumor resistance to chemotherapy and radiation treatment as well as recurrence. Extensive research has been devoted to the role of CSCs in glioblastoma multiforme (GBM), the most common primary brain tumor in adults, which is characterized by a dismal prognosis because of its aggressive course and poor response to treatment. The aim of the current paper is to provide an overview of current knowledge on the role of cancer stem cells in the pathogenesis and treatment resistance of glioblastoma. The six regulatory mechanisms of glioma stem cells (GSCs)—tumor microenvironment, niche concept, metabolism, immunity, genetics, and epigenetics—are reviewed. The molecular markers used to identify GSCs are described. The role of GSCs in the treatment resistance of glioblastoma is reviewed, along with future treatment options targeting GSCs. Stem cells of glioblastoma thus represent both a driving mechanism of major treatment difficulties and a possible target for more effective future approaches.

Paris saponin H inhibits the proliferation of glioma cells through the A1 and A3 adenosine receptor‑mediated pathway

Paris saponin H (PSH) is a type of steroid saponin derived from Rhizoma Paridis (RP; the rhizome of Paris). In our previous studies, saponins from RP exerted antiglioma activity in vitro. However, the effects of PSH on glioma have not been elucidated. The aim of the present study was to evaluate the effects of PSH on U251 glioblastoma cells and elucidate the possible underlying mechanism. The cells were treated with PSH at various concentrations for 48 h, and the cell viability, invasion, apoptosis and cycle progression were assessed using specific assay kits. The activation of Akt, 44/42‑mitogen‑activated protein kinase (MAPK) and the expression levels of A1 adenosine receptor (ARA1) and ARA3 were assessed by western blotting. The results demonstrated that PSH inhibited cell viability, migration and invasion, and induced apoptosis. Treatment of U251 cells with PSH induced the upregulation of p21 and p27, and the downregulation cyclin D1 and S‑phase kinase associated protein 2 protein expression levels, which induced cell cycle arrest at the G1 phase. The results also demonstrated that PSH inhibited the expression of ARA1, and the agonist of ARA1, 2‑chloro‑N6‑cyclopentyladenosine, reversed the effects of PSH. Hypoxia induced increases in the ARA3, hypoxia‑inducible factor‑1α (HIF‑1α) and vascular endothelial growth factor (VEGF) protein expression levels, which were associated with the activation of the Akt and P44/42 MAPK pathways. Compared with the hypoxia group, PSH inhibited the expression levels of ARA3, HIF‑1α and VEGF, as well as the phosphorylation levels of Akt and 44/42 MAPK, and repressed HIF‑1α transcriptional activity. Furthermore, the results demonstrated that PSH inhibited the expression of HIF‑1α by inhibiting the phosphorylation of Akt and 44/42 MAPK mediated by ARA3. Taken together, these results suggested that PSH reduced U251 cell viability via the inhibition of ARA1 and ARA3 expression, and further inhibited Akt and 44/42 MAPK phosphorylation, induced apoptosis and cell cycle arrest.

Implication of Lactucopicrin in Autophagy, Cell Cycle Arrest and Oxidative Stress to Inhibit U87Mg Glioblastoma Cell Growth

In this study, we propose lactucopicrin (LCTP), a natural sesquiterpene lactone from Lactucavirosa, as a molecule able to control the growth of glioblastoma continuous cell line U87Mg. The IC50 of U87Mg against LCTP revealed a strong cytotoxic effect. Daily administration of LCTP showed a dose and time-dependent reduction of GBM cell growth and viability, also confirmed by inhibition of clonogenic potential and mobility of U87Mg cells. LCTP activated autophagy in U87Mg cells and decreased the phosphorylation of proliferative signals pAKT and pERK. LCTP also induced the cell cycle arrest in G2/M phase, confirmed by decrease of CDK2 protein and increase of p53 and p21. LCTP stimulated apoptosis as evidenced by reduction of procaspase 6 and the increase of the cleaved/full-length PARP ratio. The pre-treatment of U87Mg cells with ROS scavenger N-acetylcysteine (NAC), which reversed its cytotoxic effect, showed the involvement of LCTP in oxidative stress. Finally, LCTP strongly enhanced the sensitivity of U87Mg cells to canonical therapy Temozolomide (TMZ) and synergized with this drug. Altogether, the growth inhibition of U87Mg GBM cells induced by LCTP is the result of several synergic mechanisms, which makes LCTP a promising adjuvant therapy for this complex pathology.

Exploring Notch Pathway to Elucidate Phenotypic Plasticity and Intra-tumor Heterogeneity in Gliomas

The phenotypic plasticity and self-renewal of adult neural (aNSCs) and glioblastoma stem cells (GSCs) are both known to be governed by active Notch pathway. During development, GSCs can establish differential hierarchy to produce heterogeneous groups of tumor cells belong to different grades, which makes the tumor ecosystem more complex. However, the molecular events regulating these entire processes are unknown hitherto. In this work, based on the mechanistic regulations of Notch pathway activities, a novel computational framework is introduced to inspect the intra-cellular reactions behind the development of normal and tumorigenic cells from aNSCs and GSCs, respectively. The developmental dynamics of aNSCs/GSCs are successfully simulated and molecular activities regulating the phenotypic plasticity and self-renewal processes in normal and tumor cells are identified. A novel scoring parameter “Activity Ratio” score is introduced to find out driver molecules responsible for the phenotypic plasticity and development of different grades of tumor. A new quantitative method is also developed to predict the future risk of Glioblastoma tumor of an individual with appropriate grade by using the transcriptomics profile of that individual as input. Also, a novel technique is introduced to screen and rank the potential drug-targets for suppressing the growth and differentiation of tumor cells.

Effects of aloe emodin on U87MG glioblastoma cell growth: In vitro and in vivo study

Glioblastoma, the most aggressive and malignant form of glioma, appears to be resistant to various chemotherapeutic agents. Hence other approaches have been investigated to target more pathways involved in glioblastoma development and progression. Here we investigate the anticancer effect of Aloe-Emodin (AE), an anthraquinone compound presents in the leaves of Aloe arborescens, on human glioblastoma cell line U87MG. U87MG were treated with various concentrations of AE (20 and 40 μM) for different times (24, 48, and 72 hr). Cell growth was monitored by daily cell count after treatments. Growth analysis showed that AE significantly decrease proliferation of U87MG in a time and dose dependent manner. FACS analysis demonstrates a block of cell cycle in S and G2/M phase. AE probably induced also apoptosis by releasing of apoptosis-inducing factor: PARP and Lamin activation leading to nuclear shrinkage. In addition, exposure of U87MG to AE reduced pAKT phosphorylation. AE inhibition of U87MG growth is a result of more mechanism together. Here we report that AE has a specific growth inhibition on U87MG also in in vivo. The growth of U87MG, subcutaneously injected in nude mice with severe combined immunodeficiency, is inhibited without any appreciable toxic effects on the animals after AE treatment. AE might represent a conceptually new lead antitumor adjuvant drug.

Interaction of hematopoietic CD34+ CD45+ stem cells and cancer cells stimulated by TGF‑β1 in a model of glioblastoma in vitro

The majority of modern treatment methods for malignant brain tumors are not sufficiently effective, with a median survival time varying between 9 and 14 months. Metastatic and invasive processes are the principal characteristics of malignant tumors. The most important pathogenic mechanism is epithelial‑mesenchymal transition (EMT), which causes epithelial cells to become more mobile, and capable of invading the surrounding tissues and migrating to distant organs. Transforming growth factor‑β1 (TGF‑β1) serves a key role in EMT‑inducing mechanisms. The current study presented the interaction between hematopoietic stem cells and glioblastoma cells stimulated by TGF‑β1 in vitro. The materials for the study were hematopoietic progenitor cell antigen CD34+ hematopoietic stem cells (HSCs) and U87 glioblastoma cells. Cell culture methods, automated monitoring of cell‑cell interactions, confocal laser microscopy, flow cytometry and electron microscopy were used. It was demonstrated that U87 cells have a complex communication system, including adhesive intercellular contacts, areas of interdigitation with dissolution of the cytoplasm, cell fusion, communication microtubes and microvesicles. TGF‑β1 affected glioblastoma cells by modifying the cell shape and intensifying their exocrine function. HSCs migrated to glioblastoma cells, interacted with them and exchanged fluorescent tags. Stimulation of cancer cells with TGF‑β1 weakened the ability of glioblastoma cells to attract HSCs and exchange a fluorescent tag. This process stimulated cancer cell proliferation, which is an indication of the ability of HSCs to 'switch' the proliferation and invasion processes in glioblastoma cells.

Cell biology of glioblastoma multiforme: from basic science to diagnosis and treatment

First described in the 1800s, glioblastoma multiforme (GBM), a class IV neoplasm with astrocytic differentiation, as per the revised 2016 World Health Organization classification of tumors of the central nervous system (CNS) is the most common malignant tumor of the CNS. GBM has an extremely wide set of alterations, both genetic and epigenetic, which yield a great number of mutation subgroups, some of which have an established role in independent patient survival and treatment response. All of those components not only represent a closed cycle but are also relevant to the tumor biological behavior and resistance to treatment as they form the pathobiological behavior and clinical course. The presence of different triggering mutations on the background of the presence of key mutations in the GBM stem cells (GBMsc) further separates GBM as primary arising de novo from neural stem cell precursors developing into GBMsc and secondary, by means of aggregated mutations. Some of the change in cellular biology in GBM can be observed via light microscope as they form the cellular and tissue hallmarks of the condition. Changes in genetic information, resulting in alteration, suppression and expression of genes compared to their physiological levels in healthy astrocytes lead to not only cellular, but also extracellular matrix reorganization. These changes result in a multiform number of micromorphological and purely immunological/biochemical forms. Therefore, in the twenty-first century the term multiforme, previously outcast from nomenclatures, has gained new popularity on the background of genotypic diversity in this neoplastic entry.

Restoration of miR-29b exerts anti-cancer effects on glioblastoma

Background

Glioblastoma multiforme (GBM) is known as one of the most fatal forms of cancer. MicroRNAs have been widely implicated in the regulation of mammalian development and pathogenesis. The brain-enriched miR-29 subfamilies are known to be exclusively expressed in the developing brain, and they are aberrantly down-regulated in GBM. This study aims to elucidate the role of miR-29b in GBM development and the feasibility of therapeutic targeting using conjugated nanoparticles.

Methods

After confirmation of miR-29b expression levels in GBM tissues by analysis of open source data, the anticancer effect of miR-29b was tested by the introduction of syn-hsa-miR-29b-3p in the A172 GBM cell line. In vitro studies of cell viability and apoptosis and ex vivo study using GBM tissue slice cultures from 3 patients and nanoparticle delivery of miR-29b were performed.

Results

We discovered an increase in apoptotic cell populations with the introduction of miR-29b in the GBM cell line. An established human-derived GBM tissue slice culture system confirmed the anticancer effect of miR-29b-conjugated nanoparticles. Using PCR array, we found that exogenous miR-29b inhibits the expression of COL1A2, COL3A1, COL4A1, ELN, ITGA11, MMP24, and SPARC, which mediates an anticancer effect.

Conclusions

miR-29b may serve as a putative therapeutic molecule when its expression is restored using a nanoparticle delivery system in GBM.

Effects of Saikosaponin D on apoptosis in human U87 glioblastoma cells

Saikosaponin D (SSd) is a type of Saponin derivative, which is a component extracted from Bupleurum falactum. SSd has been reported to exert anticancer activities. However, the effects of SSd on gliomas have not been elucidated. The aim of the present study was to investigate the pharmacological functions and potential molecular mechanisms of SSd in human U87 glioblastoma cells. The cells were treated with SSd at various concentrations for 48 h, the cell viability was assessed with 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium assay, and the activation of Akt, extracellular signal‑regulated kinases (ERK), c‑Jun N‑terminal kinases (JNK) and caspase‑3 was assessed by western blotting. In addition, apoptosis levels were analyzed with Hoechst 33258 and Annexin V staining. The results demonstrated that treatment of the U87 glioma cells with SSd markedly suppressed cell proliferation in a dose‑dependent manner. Meanwhile, SSd treatment enhanced apoptosis in the U87 cells. Furthermore, SSd significantly inhibited the phosphorylation of Akt and ERK, and promoted phosphorylated‑JNK and cleaved caspase‑3 expression. The present study revealed the potential therapeutic effects of SSd in the treatment of gliomas, and the cytotoxic effects of SSd in U87 cells were at least partly attributed to the depression of phosphatidylinositol 3‑kinase/Akt and ERK protein expression levels, and activation of JNK and caspase-3 expression.

Maintenance of Stemlike Glioma Cells and Microglia in an Organotypic Glioma Slice Model

BACKGROUND

The therapeutic resistance of gliomas is, at least in part, due to stemlike glioma cells (SLGCs), which self-renew, generate the bulk of tumor cells, and sustain tumor growth. SLGCs from glioblastomas (GB) have been studied in cell cultures or mouse models, whereas little is known about SLGCs from lower grade gliomas.

OBJECTIVE

To compare cell and organotypic slice cultures from GBs and lower grade gliomas and study the maintenance of SLGCs.

METHODS

Cells and tissue slices from astrocytomas, oligodendrogliomas, oligoastrocytomas, and GBs were cultivated in (1) serum-free medium supplemented with the growth factors epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), (2) medium containing 10% serum plus EGF and bFGF (F+GF medium), or (3) medium containing 10% fetal calf serum (F medium). Maintenance of cells and cytoarchitecture was addressed, using several candidate SLGC markers (Nestin, Sox2, CD133, CD44, CD49f/integrin α6, and Notch) as well as CD31 (endothelial cells), ionized calcium-binding adapter molecule 1 (microglia), and vimentin. Cell vitality was determined.

RESULTS

SLGCs were present in tissue slices from lower and higher grade gliomas. Preservation of the cytoarchitecture in slices was possible for >3 weeks. Maintenance of SLGCs required the presence of EGF/bFGF in cell and slice cultures, in which F+GF appeared superior to N medium. Constraints were observed regarding the preservation of the microglia but not of the endothelial cells. Maintenance of the microglia was improved by addition of the cytokine macrophage colony-stimulating factor.

CONCLUSION

Medium supplemented with serum and growth factors EGF, bFGF, and macrophage colony-stimulating factor permits the preservation of SLGCs and non-SLGCs in the original glioma microenvironment.

Emerging targets for glioblastoma stem cell therapy

Glioblastoma multiforme (GBM), designated as World Health Organization (WHO) grade IV astrocytoma, is a lethal and therapy-resistant brain cancer comprised of several tumor cell subpopulations, including GBM stem cells (GSCs) which are believed to contribute to tumor recurrence following initial response to therapies. Emerging evidence demonstrates that GBM tumors are initiated from GSCs. The development and use of novel therapies including small molecule inhibitors of specific proteins in signaling pathways that regulate stemness, proliferation and migration of GSCs, immunotherapy, and non-coding microRNAs may provide better means of treating GBM. Identification and characterization of GSC-specific signaling pathways would be necessary to identify specific therapeutic targets which may lead to the development of more efficient therapies selectively targeting GSCs. Several signaling pathways including mTOR, AKT, maternal embryonic leucine zipper kinase (MELK), NOTCH1 and Wnt/β-catenin as well as expression of cancer stem cell markers CD133, CD44, Oct4, Sox2, Nanog, and ALDH1A1 maintain GSC properties. Moreover, the data published in the Cancer Genome Atlas (TCGA) specifically demonstrated the activated PI3K/AKT/mTOR pathway in GBM tumorigenesis. Studying such pathways may help to understand GSC biology and lead to the development of potential therapeutic interventions to render them more sensitive to chemotherapy and radiation therapy. Furthemore, recent demonstration of dedifferentiation of GBM cell lines into CSC-like cells prove that any successful therapeutic agent or combination of drugs for GBM therapy must eliminate not only GSCs, but the differentiated GBM cells and the entire bulk of tumor cells.

Astroblastoma: beside being a tumor entity, an occasional phenotype of astrocytic gliomas?

The diagnosis of astroblastoma is based on a typical histological aspect with perivascular distribution of cells sending cytoplasmic extensions to the vessels and vascular hyalinization. These criteria are useful for standardizing the identification of the tumor, but, in spite of this, there are discrepancies in the literature concerning the age distribution and the benign or malignant nature of the tumor. Three cases are discussed in this study: Case 1 was a typical high-grade astroblastoma; Case 2 was an oligodendroglioma at the first intervention and an oligoastrocytoma at the second intervention with typical perivascular arrangements in the astrocytic component; Case 3 was a gemistocytic glioma with malignant features and typical perivascular arrangements. Genetic analysis showed genetic alterations that are typical of gliomas of all malignancy grades. Using the neurosphere assay, neurospheres and adherent cells were found to have developed in Case 1, while adherent cells only developed in Case 2, in line with the stemness potential of the tumors. The cases are discussed in relation to their diagnostic assessment as astroblastoma, and it is hypothesized that the typical perivascular distribution of cells may not indicate a separate and unique tumor entity, but may be a peculiarity that can be acquired by astrocytic gliomas when an unknown cause from the tumor microenvironment influences the relationship between vessels and tumor cells.

Three-dimensional constructs using hyaluronan cell carrier as a tool for the study of cancer stem cells

BACKGROUND

Cancer research focuses increasingly on cancer stem cell study as those cells are thought to be the root of chemo and radioresistance of the most aggressive cancer types. Nevertheless, two-dimensional (2D) cell culture and even three-dimensional (3D) spheroid models, with their limited ability to reflect cell-extracellular matrix interactions, are not ideal for the study of cancer stem cells (CSCs). In this study, we establish a 3D in vitro cancer model using a synthetic and natural scaffold with tunable features and show that U87 cells cultured in this system acquire a stem-cell like phenotype.

METHODS

U87 astrocytoma cells were grown on polycaprolactone (PCL)-2D flat substrates (2D) and PCL-3D scaffolds (3D) eventually containing hyaluronic acid (3D-HA). Cell viability, growth patterns, morphology, and cell surface marker expression (CD44, RHAMM and CD133) were studied to assess the effect of 3D culture and presence of HA.

RESULTS

3D scaffold, but most prominently presence of HA induced changes in cell morphology and marker expression; 3D-HA cultures showed features of aggregates; moreover, markedly increased expression of Nestin, CD44, RHAMM, and CD133 in 3D-HA scaffolds were found.

CONCLUSIONS

the behavior of U87 in our 3D-HA model is more similar to tumor growth in vivo and a stem-like phenotype is promoted. Thus, the 3D-HA scaffold could provide a useful model for CSCs study and anti-cancer therapeutics research in vitro and may have preclinical application for the screening of drug candidates.

Recognizing and correcting failures in glioblastoma treatment

While current treatment remains universal for glioblastoma, recent evidence has demonstrated marked heterogeneity in their molecular profiles. Due to the near universal rate of recurrence, attention has focused on individualized treatment and subgroup population differences that may influence the efficacy of adjuvant therapy. Recent studies have implicated chemo-radioresistant GBM stem cells (GSCs) in the propagation of heterogeneous tumor profiles. As a result, there has been a shift to classify and target GSCs in order to increase survival and delay relapse. The overall objective of our editorial is to highlight current failures in GBM treatment and to propose novel personalized methods to correct our shortcomings in GBM treatment.

Adult neurogenesis and glial oncogenesis: when the process fails

Malignant brain tumors, including glioblastoma multiforme (GBM), are known for their high degree of invasiveness, aggressiveness, and lethality. These tumors are made up of heterogeneous cell populations and only a small part of these cells (known as cancer stem cells) is responsible for the initiation and recurrence of the tumor. The biology of cancer stem cells and their role in brain tumor growth and therapeutic resistance has been extensively investigated. Recent work suggests that glial tumors arise from neural stem cells that undergo a defective process of differentiation. The understanding of this process might permit the development of novel treatment strategies targeting cancer stem cells. In the present review, we address the mechanisms underlying glial tumor formation, paying special attention to cancer stem cells and the role of the microenvironment in preserving them and promoting tumor growth. Recent advancements in cancer stem cell biology, especially regarding tumor initiation and resistance to chemo- or radiotherapy, have led to the development of novel treatment strategies that focus on the niche of the stem cells that make up the tumor. Encouraging results from preclinical studies predict that these findings will be translated into the clinical field in the near future.

Brain stem cells as the cell of origin in glioma

Glioma incidence rates in the United States are near 20000 new cases per year, with a median survival time of 14.6 mo for high-grade gliomas due to limited therapeutic options. The origins of these tumors and their many subtypes remain a matter of investigation. Evidence from mouse models of glioma and human clinical data have provided clues about the cell types and initiating oncogenic mutations that drive gliomagenesis, a topic we review here. There has been mixed evidence as to whether or not the cells of origin are neural stem cells, progenitor cells or differentiated progeny. Many of the existing murine models target cell populations defined by lineage-specific promoters or employ lineage-tracing methods to track the potential cells of origin. Our ability to target specific cell populations will likely increase concurrently with the knowledge gleaned from an understanding of neurogenesis in the adult brain. The cell of origin is one variable in tumorigenesis, as oncogenes or tumor suppressor genes may differentially transform the neuroglial cell types. Knowledge of key driver mutations and susceptible cell types will allow us to understand cancer biology from a developmental standpoint and enable early interventional strategies and biomarker discovery.

Inhibitory activities of trichostatin a in U87 glioblastoma cells and tumorsphere-derived cells

Epigenetic alterations have been increasingly implicated in glioblastoma (GBM) pathogenesis, and epigenetic modulators including histone deacetylase inhibitors (HDACis) have been investigated as candidate therapies. GBMs are proposed to contain a subpopulation of glioblastoma stem cells (GSCs) that sustain tumor progression and therapeutic resistance and can form tumorspheres in culture. Here, we investigate the effects of the HDACi trichostatin A (TSA) in U87 GBM cultures and tumorsphere-derived cells. Using approaches that include a novel method to measure tumorsphere sizes and the area covered by spheres in GBM cultures, as well as a nuclear morphometric analysis, we show that TSA reduced proliferation and colony sizes, led to G2/M arrest, induced alterations in nuclear morphology consistent with cell senescence, and increased the protein content of GFAP, but did not affect migration, in cultured human U87 GBM cells. In cells expanded in tumorsphere assays, TSA reduced sphere formation and induced neuron-like morphological changes. The expression of stemness markers in these cells was detected by reverse transcriptase polymerase chain reaction. These findings indicate that HDACis can inhibit proliferation, survival, and tumorsphere formation, and promote differentiation of U87 GBM cells, providing further evidence for the development of HDACis as potential therapeutics against GBM.

Establishment of a green fluorescent protein tracing murine model focused on the functions of host components in necrosis repair and the niche of subcutaneously implanted glioma

Due to progress in the research of glioma stem cells and the glioma niche, development of an animal model that facilitates the elucidation of the roles of the host tissue and cells is necessary. The aim of the present study was to develop a subcutaneous xenograft green fluorescent protein nude mouse model and use this model to analyze the roles of host cells in tumor necrosis repair. Tumors derived from the human glioma stem/progenitor cell line SU3 were subcutaneously implanted in green fluorescent protein nude mice. The implanted tumors were then passed from animal to animal for 10 generations. Finally, subcutaneous xenografts were assayed with traditional pathology, immunopathological techniques and fluorescence photography. For each generation, the tumorigenicity rate was 100%. Subcutaneous xenografts were rich in blood vessels, and necrotic and hemorrhagic foci, which highly expressed hypoxia-inducible factor-1α, tumor necrosis factor, Ki-67, CD68 and CD11b. In the interstitial tissue, particularly in old hemorrhagic foci, there were numerous cells expressing green fluorescent protein, CD68 and CD11b. Green fluorescent protein nude mouse subcutaneous xenografts not only consistently maintained the high invasiveness and tumorigenicity of glioma stem/progenitor cells, but also consisted of a high concentration of tumor blood vessels and necrotic and hemorrhagic foci. Subcutaneous xenografts also expressed high levels of tumor microenvironment-related proteins and host-derived tumor interstitial molecules. The model has significant potential for further research on tumor tissue remodeling and the tumor microenvironment.

Epidermal growth factor receptor as a therapeutic target in glioblastoma

Glioblastoma represents one of the most challenging problems in neurooncology. Among key elements driving its behavior is the transmembrane epidermal growth factor receptor family, with the first member epidermal growth factor receptor (EGFR) centered in most studies. Engagement of the extracellular domain with a ligand activates the intracellular tyrosine kinase (TK) domain of EGFR, leading to autophosphorylation and signal transduction that controls proliferation, gene transcription, and apoptosis. Oncogenic missense mutations, deletions, and insertions in the EGFR gene are preferentially located in the extracellular domain in glioblastoma and cause constitutive activation of the receptor. The mutant EGFR may also transactivate other cell surface molecules, such as additional members of the EGFR family and the platelet-derived growth factor receptor, which ignite signaling cascades that synergize with the EGFR-initiated cascade. Because of the cell surface location and increased expression of the receptor along with its important biological function, EGFR has triggered much effort for designing targeted therapy. These approaches include TK inhibition, monoclonal antibody, vaccine, and RNA-based downregulation of the receptor. Treatment success requires that the drug penetrates the blood-brain barrier and has low systemic toxicity but high selectivity for the tumor. While the blockade of EGFR-dependent processes resulted in experimental and clinical treatment success, cells capable of using alternative signaling ultimately escape this strategy. A combination of interventions targeting tumor-specific cell surface regulators along with convergent downstream signaling pathways will likely enhance efficacy. Studies on EGFR in glioblastoma have revealed much information about the complexity of gliomagenesis and also facilitated the development of strategies for targeting drivers of tumor growth and combination therapies with increasing complexity.

The histone deacetylase inhibitor sodium butyrate promotes cell death and differentiation and reduces neurosphere formation in human medulloblastoma cells

Increasing evidence suggests that alterations in epigenetic mechanisms regulating chromatin state play a role in the pathogenesis of medulloblastoma (MB), the most common malignant brain tumor of childhood. Histone deacetylase (HDAC) inhibitors, which increase chromatin relaxation, have been shown to display anticancer activities. Here we show that the HDAC inhibitor sodium butyrate (NaB) markedly increases cell death and reduces colony formation in human MB cell lines. In addition, NaB increased the mRNA expression of Gria2, a neuronal differentiation marker, in D283 and DAOY cells and reduced the number of neurospheres in D283 cell cultures. Finally, NaB reduced the viability of D283 cells when combined with etoposide. These data show that NaB displays pronounced inhibitory effects on the survival of human MB cells and suggest that NaB might potentiate the effects of etoposide. In addition, our study suggests that HDAC inhibition might promote the neuronal differentiation of MB cells and provides the first evidence that an HDAC inhibitor might suppress the expansion or survival of MB cancer stem cells.