Glioblastoma Multiforme Tumorigenesis Research Articles

Therapeutic Potential of RTA 404 in Human Brain Malignant Glioma Cell Lines via Cell Cycle Arrest via p21/AKT Signaling.

Background Glioblastoma multiforme (GBM) is the most common malignant brain tumor in the world. Despite advances in surgical resection, radiotherapy, and chemotherapy, GBM continues to have a poor overall survival. CDDO (2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid), a synthetic triterpenoid, is an Nrf2 activator used to inhibit proliferation and induce differentiation and apoptosis in various cancer cells. One new trifluoroethylamide derivative of CDDO, RTA 404, has been found to have increased ability to cross the blood-brain barrier. However, it is not clear what effect it may have on tumorigenesis in GBM. Methods This in vitro study evaluated the effects of RTA 404 on GBM cells. To do this, we treated GBM840 and U87 MG cell lines with RTA 404 and assessed apoptosis, cell cycle, cell locomotion, and senescence. DNA content and induction of apoptosis were analyzed by flow cytometry and protein expression by Western blot analysis. Results RTA 404 significantly inhibited the proliferation of tumor cells at concentrations higher than 100 nM (p < 0.05) and reduced their locomotion ability. In addition, treatment with RTA 404 led to an accumulation of RTA 404-treated G2/M phase cells and apoptosis. An analysis of the p21/AKT expression suggested that RTA 404 may not only help prevent brain cancer but it may also exert antitumor activities in established GBM cells. Conclusion RTA404 can inhibit proliferation, cell locomotion, cell cycle progression, and induce apoptosis in GBM cells in vitro, possibly through its inhibition of N-cadherin and E-cadherin expression via its inhibition of the AKT pathway.

The novel roles of virus infection-associated gene CDKN1A in chemoresistance and immune infiltration of glioblastoma.

Chemoresistance is a common limitation for successful treatment of glioblastoma multiforme (GBM). Recently, virus infections have been demonstrated to be associated with tumorigenesis and chemoresistance in tumors. However, the role of infection-related genes in GBM haven’t been clearly demonstrated. Here, we explored the roles and mechanisms of human T-lymphotropic virus type-1 (HTLV-1) infections in tumorigenesis and chemoresistance in GBM. Four candidate genes, CDKN1A, MSX1, MYC and CHEK2, were identified to be the codifferentially expressed genes between three temozolomide (TMZ) chemotherapy datasets and one HTLV-1 infection gene set. Next, comprehensive bioinformatics data from several databases indicated that only CDKN1A was significantly upregulated in both GBM tissues and cells and showed the greatest prognostic value in GBM patients. Clinical data identified the correlations between CDKN1A expression and clinicopathological parameters of GBM patients. Moreover, CDKN1A was found to be involved in AKT-mediated TMZ resistance of glioma cells. In addition, KEGG analysis of CDKN1A-associated coexpression genes showed that CDKN1A was potentially involved in complement and coagulation cascades pathways in GBM. Finally, TISIDB database was used to investigate the role of CDKN1A in tumor-immune system interactions in GBM. These findings enhanced our understanding of the roles of CDKN1A in tumorigenesis and therapy response in GBM.

Beyond glucose: alternative sources of energy in glioblastoma.

Glioblastoma multiforme (GBM) is the most common malignant brain tumor in adults. With a designation of WHO Grade IV, it is also the most lethal primary brain tumor with a median survival of just 15 months. This is often despite aggressive treatment that includes surgical resection, radiation therapy, and chemotherapy. Based on the poor outcomes and prevalence of the tumor, the demand for innovative therapies continues to represent a pressing issue for clinicians and researchers. In terms of therapies targeting metabolism, the prevalence of the Warburg effect has led to a focus on targeting glucose metabolism to halt tumor progression. While glucose is the dominant source of growth substrate in GBM, a number of unique metabolic pathways are exploited in GBM to meet the increased demand for replication and progression. In this review we aim to explore how metabolites from fatty acid oxidation, the urea cycle, the glutamate-glutamine cycle, and one-carbon metabolism are shunted toward energy producing pathways to meet the high energy demand in GBM. We will also explore how the process of autophagy provides a reservoir of nutrients to support viable tumor cells. By so doing, we aim to establish a foundation of implicated metabolic mechanisms supporting growth and tumorigenesis of GBM within the literature. With the sparse number of therapeutic interventions specifically targeting metabolic pathways in GBM, we hope that this review expands further insight into the development of novel treatment modalities.

LINC01152 upregulates MAML2 expression to modulate the progression of glioblastoma multiforme via Notch signaling pathway

Glioblastoma multiforme (GBM) brings serious physical and psychological pain to GBM patients, whose survival rate remains not optimistic. Long noncoding RNAs (lncRNAs) have been reported to participate in the progression of many cancers, including GBM. However, the mechanism and function of long intergenic non-protein coding RNA 1152 (LINC01152) in GBM are still unclear. In our study, we aimed to explore the function and mechanism of LINC01152 in GBM. Then qRT-PCR analysis was implemented to search the expression of RNAs in GBM tissues and cells. Functional assays such as EdU assay, colony formation assay, TUNEL assay and flow cytometry analysis were conducted to estimate GBM cell proliferation and apoptosis. RNA pull down assay, luciferase reporter assay, RIP and ChIP assays were implemented to search the binding between molecules. As a result, we discovered that LINC01152 was upregulated in GBM tissues and cells. LINC01152 and mastermind like transcriptional coactivator 2 (MAML2) could both play the oncogenic part in GBM. Moreover, LINC01152 positively regulated MAML2 in GBM by sponging miR-466 and recruiting SRSF1. In turn, RBPJ/MAML2 transcription complex was found to activate the transcription of LINC01152 in GBM cells. In conclusion, LINC01152 could upregulate the expression of MAML2 to promote tumorigenesis in GBM via Notch signaling pathway.

MALT1 is a potential therapeutic target in glioblastoma and plays a crucial role in EGFR‐induced NF‐κB activation

Glioblastoma multiforme (GBM) is the most common malignant tumour in the adult brain and hard to treat. Nuclear factor κB (NF‐κB) signalling has a crucial role in the tumorigenesis of GBM. EGFR signalling is an important driver of NF‐κB activation in GBM; however, the correlation between EGFR and the NF‐κB pathway remains unclear. In this study, we investigated the role of mucosa‐associated lymphoma antigen 1 (MALT1) in glioma progression and evaluated the anti‐tumour activity and effectiveness of MI‐2, a MALT1 inhibitor in a pre‐clinical GBM model. We identified a paracaspase MALT1 that is involved in EGFR‐induced NF‐kB activation in GBM. MALT1 deficiency or inhibition significantly affected the proliferation, survival, migration and invasion of GBM cells both in vitro and in vivo. Moreover, MALT1 inhibition caused G1 cell cycle arrest by regulating multiple cell cycle–associated proteins. Mechanistically, MALTI inhibition blocks the degradation of IκBα and prevents the nuclear accumulation of the NF‐κB p65 subunit in GBM cells. This study found that MALT1, a key signal transduction cascade, can mediate EGFR‐induced NF‐kB activation in GBM and may be potentially used as a novel therapeutic target for GBM.

Protein Palmitoylation Regulates Cell Survival by Modulating XBP1 Activity in Glioblastoma Multiforme

Glioblastoma multiforme (GBM) almost invariably acquires an invasive phenotype, resulting in limited therapeutic options. Protein palmitoylation markedly affects tumorigenesis and malignant progression in GBM. The role of protein palmitoylation in GBM, however, has not been systematically reported. This study aimed to investigate the effect of protein palmitoylation on GBM cell survival and the cell cycle. In this study, most palmitoyltransferases were upregulated in GBM and its cell lines, and protein palmitoylation participated in signaling pathways controlling cell survival and the GBM cell cycle. Inhibition of protein palmitoylation with substrate-analog inhibitors, that is, 2-bromopalmitate, cerulenin, and tunicamycin, induced G2 cell cycle arrest and cell death in GBM cells through enhanced endoplasmic reticulum (ER) stress. These effects are primarily attributed to the palmitoylation inhibitors activating pro-apoptotic pathways and ER stress signals. Further analysis revealed was the accumulation of SUMOylated XBP1 (X-box binding protein 1) and its transcriptional repression, along with a reduction in XBP1 palmitoylation. Taken together, the present results indicate that protein palmitoylation plays an important role in the survival of GBM cells, further providing a potential therapeutic strategy for GBM.

Germ Cell-Specific Gene 1-Like Protein Regulated by Splicing Factor CUGBP Elav-Like Family Member 5 and Primary Bile Acid Biosynthesis are Prognostic in Glioblastoma Multiforme.

BackgroundAlternative splicing (AS) modifies 92-94% human genes, abnormal splicing events might relate to tumor development and invasion. Glioblastoma Multiforme (GBM) is a fatal, invasive, and malignant tumor in nervous system. The recurrence and development leads to poor prognosis. However, few studies have focused on AS in GBM.MethodsRNA-seq and Alternative splicing events (ASEs) data of GBM samples were downloaded from The Cancer Genome Atlas (TCGA) and TCGASpliceSeq databases, respectively. Firstly, the Cox regression analysis was utilized to identify the overall survival splicing events (OS-SEs). Secondly, a multivariable model was applied to access the prognostic value of risk score. Then, we constructed a co-expressed network between splicing factors (SFs) and overall survival alternative splicing events (OS-SEs). Additionally, to explore the relationship between the potential prognostic signaling pathways and OS-SEs, we constructed a network between these pathways and OS-SEs. Ultimately, to better explain the results, validations from multi-dimension platforms were applied.ResultsIn the first step, 1,062 OS-SEs were selected by Cox regression. Then, 11 OS-SEs were integrated in a multivariate model by Lasso regression. The area under the curve (AUC) of receiver operator characteristic (ROC) curve was 0.861. In addition, the risk score generated from the multivariate model was confirmed to be an independent prognostic factor (P < 0.001). What's more, in the network of SFs and ASEs, CELF5 significantly regulated GSG1L|35696|AP and GSG1L|35698|AP (P < 0.001, R = 0.511 and = -0.492). Additionally, GSG1L|35696|AP (P = 0.006) and GSG1L|35698|AP (P = 0.007) showed a significant relationship with cancer status. Eventually, KEGG pathways related to prognosis of GBM were selected by GSVA. The primary bile acid synthesis (P < 0.001, R = 0.420) was the significant pathway co-expressed with Germ Cell-Specific Gene 1-Like Protein (GSG1L).ConclusionsBased on the comprehensive bioinformatics analysis, we proposed that aberrant splicing factor CUGBP Elav-like family member 5 (CELF5) significantly, positively and negatively, regulated ASE of GSG1L, and the primary bile acid synthesis pathway might play an important role in tumorigenesis and prognosis of GBM.

Overexpression of microRNA-129-5p in glioblastoma inhibits cell proliferation, migration, and colony-forming ability by targeting ZFP36L1.

Glioblastoma multiforme (GBM) is a highly invasive cancer with a high recurrence rate. The prognosis of GBM patients remains poor, even after standard surgical resection combined with chemoradiotherapy. Thus, there is an urgent need for new therapeutic targets in GBM. In recent years, microRNAs have received considerable attention due to their important role in tumor development and progression. In this study, we investigated the role of miR-129-5p and miR-129-5p/ZFP36L1 axis in GBM tumorigenesis. Analysis of GSE103228 microarray data from the GEO database showed that miR-129-5p was significantly downregulated in GBM vs. normal brain tissues. Quantitative reverse transcription PCR analysis of miR-129-5p expression in seven GBM cell lines (LN229, A172, U87, T98G, U251, H4, and LN118) vs. normal human astrocytes (NHA) showed miR-129-5p was significantly downregulated in GBM cells. Overexpression of miR-129-5p in LN229 and A172 cells significantly suppressed cell proliferation, migration, invasion, and colony-forming ability. Target Scan analysis identified ZFP36L1 as the target of miR-129-5p. UALCAN dataset analysis found that ZFP36L1 was significantly upregulated in GBM vs. normal brain tissues, and high ZFP36L1 expression was positively associated with poor survival of GBM patients. Western blot analysis demonstrated that ZFP36L1 was significantly upregulated in seven GBM cell lines vs. NHA. Overexpression of miR-129-5p in LN229 and A172 cells significantly inhibited ZFP36L1 mRNA and protein expression, while overexpression of ZFP36L1 in LN229 and A172 cells reversed miR-129-5p-mediated inhibition on GBM tumorigenesis. Our results revealed an important role of miR-129-5p in the negative regulation of ZFP36L1 expression in GBM, suggesting new candidates for targeted therapy in GBM patients.

Expression and clinical significance of CPS1 in glioblastoma multiforme

Carbamoyl phosphate synthetase-1 (CPS1), the first rate-limiting mitochondrial enzyme in the urea cycle, regulates proliferation and differentiation during tumor progression. However, the detailed function of CPS1 in glioblastoma Multiforme (GBM) is still unclear. Here, we highlight mechanisms for CPS1 upregulation and the effects of upregulated CPS1 on GBM tumorigenesis. The transcriptome data from several public databases, such as Oncomine and GEPIA, revealed that CPS1 transcriptional level was significantly upregulated in GBM tissues and cells. Moreover, CPS1 was hypomethylated in GBM tissues. The Wanderer database, linked to the Cancer Genome Atlas (TCGA), showed the association between CPS1 expression or its methylation values and the clinicopathological parameters in GBM patients. Our work fully demonstrated that CPS1 expression was upregulated in GBM and this gene could be used as a potential diagnostic and prognosis indicator for GBM.

Preclinical Evidence of STAT3 Inhibitor Pacritinib Overcoming Temozolomide Resistance via Downregulating miR-21-Enriched Exosomes from M2 Glioblastoma-Associated Macrophages.

Background: The tumor microenvironment (TME) plays a crucial role in virtually every aspect of tumorigenesis of glioblastoma multiforme (GBM). A dysfunctional TME promotes drug resistance, disease recurrence, and distant metastasis. Recent evidence indicates that exosomes released by stromal cells within the TME may promote oncogenic phenotypes via transferring signaling molecules such as cytokines, proteins, and microRNAs. Results: In this study, clinical GBM samples were collected and analyzed. We found that GBM-associated macrophages (GAMs) secreted exosomes which were enriched with oncomiR-21. Coculture of GAMs (and GAM-derived exosomes) and GBM cell lines increased GBM cells’ resistance against temozolomide (TMZ) by upregulating the prosurvival gene programmed cell death protein 4 (PDCD4) and stemness markers SRY (sex determining region y)-box 2 (Sox2), signal transducer and activator of transcription 3 (STAT3), Nestin, and miR-21-5p and increasing the M2 cytokines interleukin 6 (IL-6) and transforming growth factor beta 1(TGF-β1) secreted by GBM cells, promoting the M2 polarization of GAMs. Subsequently, pacritinib treatment suppressed GBM tumorigenesis and stemness; more importantly, pacritinib-treated GBM cells showed a markedly reduced ability to secret M2 cytokines and reduced miR-21-enriched exosomes secreted by GAMs. Pacritinib-mediated effects were accompanied by a reduction of oncomiR miR-21-5p, by which the tumor suppressor PDCD4 was targeted. We subsequently established patient-derived xenograft (PDX) models where mice bore patient GBM and GAMs. Treatment with pacritinib and the combination of pacritinib and TMZ appeared to significantly reduce the tumorigenesis of GBM/GAM PDX mice as well as overcome TMZ resistance and M2 polarization of GAMs. Conclusion: In summation, we showed the potential of pacritinib alone or in combination with TMZ to suppress GBM tumorigenesis via modulating STAT3/miR-21/PDCD4 signaling. Further investigations are warranted for adopting pacritinib for the treatment of TMZ-resistant GBM in clinical settings.

Long non‑coding RNA DLEU1 promotes cell proliferation of glioblastoma multiforme.

Glioblastoma multiforme (GBM) is the most common malignant tumor with high morbidity and mortality. This study investigated the role of long non‑coding RNAs (lncRNAs) in glioblastomagenesis progression. Using the GSE2223 and GSE59612 datasets, and RNA sequencing data of GBM from The Cancer Genome Atlas, differentially expressed (DE) genes including DE messenger RNAs (DEmRNAs) and DElncRNAs between GBM and normal controls were identified. Based on the competing endogenous RNA hypothesis, DElncRNA‑micro RNA (miRNA)‑DEmRNA interactions were obtained by target gene prediction. Gene Ontology (GO) and Kyoto Encyclopedia of Gene and Genomes pathway analysis of DEmRNAs in the DElncRNA‑miRNA‑DEmRNA network was performed. Expression and function analyses of DElncRNAs were performed by reverse transcription‑polymerase chain reaction (RT‑PCR) and an established viability assay, respectively. In total, 712 DE genes were identified. Significant upregulation of lncRNA deleted in lymphocytic leukemia 1 (DLEU1) was revealed in GBM and a number of other types of cancer. DLEU1 interacted with 315 miRNAs and 105 DEmRNAs. The DEmRNAs were mainly enriched in tumorigenesis‑associated GO terms (angiogenesis, positive regulation of cell proliferation, positive regulation of fibroblast apoptotic processes and regulation of neutrophil migration) and pathways (Hippo signaling pathway, cancer pathways, and Wnt signaling pathway). Correlation analysis revealed that mRNA TNF receptor associated factor 4 (TRAF4) was associated with DLEU1 expression. RT‑PCR demonstrated that the expression levels of DLEU1 and TRAF4 were increased in GBM tissues. Small interfering RNA demonstrated that silencing DLEU1 downregulated TRAF4. The viability of GBM cells was significantly decreased following RNA interference with DLEU1 and TRAF4 production. The results demonstrate that DLEU1 and TRAF4 is highly expressed in GBM tissues and promotes proliferation of GBM cells. It may act as a competing endogenous RNA and influence tumorigenesis of GBM.

Construction of Potential Glioblastoma Multiforme-Related miRNA-mRNA Regulatory Network.

Background: Glioblastoma multiforme (GBM), the most common and aggressive human malignant brain tumor, is notorious for its limited treatment options and poor prognosis. MicroRNAs (miRNAs) are found to be involved in tumorigenesis of GBM. However, a comprehensive miRNA-mRNA regulatory network has still not been established.Methods: A miRNA microarray dataset (GSE90603) was obtained from GEO database. Then, we employed GEO2R tool to perform differential expression analysis. Potential transcription factors and target genes of screened differentially expressed miRNAs (DE-miRNAs) were predicted. The GBM mRNA dataset were downloaded from TCGA database for identifying differentially expressed genes (DEGs). Next, GO annotation and KEGG pathway enrichment analysis was conducted. PPI network was then established, and hub genes were identified via Cytoscape software. The expression and prognostic roles of hub genes was further evaluated.Results: Total 33 DE-miRNAs, consisting of 10 upregulated DE-miRNAs and 23 downregulated DE-miRNAs, were screened. SP1 was predicted to potentially regulate most of screened DE-miRNAs. Three thousand and twenty seven and 3,879 predicted target genes were obtained for upregulated and downregulated DE-miRNAs, respectively. Subsequently, 1,715 upregulated DEGs and 1,259 downregulated DEGs were identified. Then, 149 and 295 potential downregulated and upregulated genes commonly appeared in target genes of DE-miRNAs and DEGs were selected for GO annotation and KEGG pathway enrichment analysis. The downregulated genes were significantly enriched in cGMP-PKG signaling pathway and calcium signaling pathway whereas the upregulated genes were enriched in pathways in cancer and PI3K-Akt signaling pathway. Construction and analysis of PPI network showed that STXBP1 and TP53 were recognized as hub genes with the highest connectivity degrees. Expression analytic result of the top 20 hub genes in GBM using GEPIA database was generally identical with previous differential expression analysis for TCGA data. EGFR, PPP3CB, and MYO5A expression was significantly associated with patients' OS.Conclusions: In this study, we established a potential GBM-related miRNA-mRNA regulatory network, which explores a comprehensive understanding of the molecular mechanisms and provides key clues in seeking novel therapeutic targets for GBM. In the future, more experiments need to be performed to validate our current findings.

Basic Gene Expression Characteristics of Glioma Stem Cells and Human Glioblastoma.

Glioma stem cells (GSCs) play important roles in the tumorigenesis of glioblastoma multiforme (GBM). Using a novel cellular bioinformatics pipeline, we aimed to characterize the differences in gene-expression profiles among GSCs, U251 (glioma cell line), and a human GBM tissue sample. Total RNA was extracted from GSCs, U251 and GBM and microarray analysis was performed; the data were then applied to the bioinformatics pipeline consisting of a principal component analysis (PCA) with factor loadings, an intracellular pathway analysis, and an immunopathway analysis. The PCA clearly distinguished the three groups. The factor loadings of the PCA suggested that v-myc avian myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN), dipeptidyl-peptidase 4 (DPP4), and macrophage migration-inhibitory factor (MIF) contribute to the stemness of GSCs. The intracellular pathway and immunopathway analyses provided relevant information about the functions of representative genes in GSCs. The newly-developed cellular bioinformatics pipeline was a useful method to clarify the similarities and differences among samples.

Drosophila melanogaster as a Model System for Human Glioblastomas.

Glioblastoma multiforme (GBM) is the most common primary malignant adult brain tumor. Genomic amplifications, activating mutations, and overexpression of receptor tyrosine kinases (RTKs) such as EGFR, and genes in core RTK signaling transduction pathways such as PI3K are common in GBM. However, efforts to target these pathways have been largely unsuccessful in the clinic, and the median survival of GBM patients remains poor at 14-15months. Therefore, to improve patient outcomes, there must be a concerted effort to elucidate the underlying biology involved in GBM tumorigenesis. Drosophila melanogaster has been a highly effective model for furthering our understanding of GBM tumorigenesis due to a number of experimental advantages it has over traditional mouse models. For example, there exists extensive cellular and genetic homology between humans and Drosophila, and 75% of genes associated with human disease have functional fly orthologs. To take advantage of these traits, we developed a Drosophila GBM model with constitutively active variants of EGFR and PI3K that effectively recapitulated key aspects of GBM disease. Researchers have utilized this model in forward genetic screens and have expanded on its functionality to make a number of important discoveries regarding requirements for key components in GBM tumorigenesis, including genes and pathways involved in extracellular matrix signaling, glycolytic metabolism, invasion/migration, stem cell fate and differentiation, and asymmetric cell division. Drosophila will continue to reveal novel biological pathways and mechanisms involved in gliomagenesis, and this knowledge may contribute to the development of effective treatment strategies to improve patient outcomes.

EIF4A3-induced circular RNA MMP9 (circMMP9) acts as a sponge of miR-124 and promotes glioblastoma multiforme cell tumorigenesis

BackgroundCircular RNAs (circRNAs) have been found to play critical roles in the development and progression of various cancers. However, little is known about the effects of the circular RNA network on glioblastoma multiforme (GBM).MethodsA microarray was used to screen circRNA expression in GBM. Quantitative real-time PCR was used to detect the expression of circMMP9. GBM cells were transfected with a circMMP9 overexpression vector or siRNA, and cell proliferation, migration and invasion, as well as tumorigenesis in nude mice, were assessed to examine the effect of circMMP9 in GBM. Biotin-coupled miRNA capture, fluorescence in situ hybridization and luciferase reporter assays were conducted to confirm the relationship between circMMP9 and miR-124.ResultsIn this study, we screened differentially expressed circRNAs and identified circMMP9 in GBM. We found that circMMP9 acted as an oncogene, was upregulated in GBM and promoted the proliferation, migration and invasion abilities of GBM cells. Next, we verified that circMMP9 served as a sponge that directly targeted miR-124; circMMP9 accelerated GBM cell proliferation, migration and invasion by targeting miR-124. Furthermore, we found that cyclin-dependent kinase 4 (CDK4) and aurora kinase A (AURKA) were involved in circMMP9/miR-124 axis-induced GBM tumorigenesis. Finally, we found that eukaryotic initiation factor 4A3 (eIF4A3), which binds to the MMP9 mRNA transcript, induced circMMP9 cyclization and increased circMMP9 expression in GBM.ConclusionsOur findings indicate that eIF4A3-induced circMMP9 is an important underlying mechanism in GBM cell proliferation, invasion and metastasis through modulation of the miR-124 signaling pathway, which could provide pivotal potential therapeutic targets for the treatment of GBM.Graphical abstract

Biomimetic models to examine microenvironmental regulation of glioblastoma stem cells

Glioblastoma multiforme (GBM), a malignant brain tumor, is the deadliest form of human cancer with low survival rates because of its highly invasive nature. In recent years, there has been a growing appreciation for the role that glioblastoma stem cells (GSCs) play during tumorigenesis and tumor recurrence of GBM. GSCs are a specialized subset of GBM cells with stem cell-like features that contribute to tumor initiation and therapeutic resistance. Thus, to enhance therapeutic efficiency and improve survival, targeting GSCs and their microenvironmental niche appears to be a promising approach. To develop this approach, understanding GSC-microenvironment interactions is crucial. This review discusses various biomimetic model systems to understand the impact of biophysical, biochemical, and cellular microenvironmental cues on GSC behaviors. These models include two-dimensional or matrix-free environment models, engineered biomaterial-based three-dimensional models, co-culture models, and mouse and rat in vivo models. These systems have been used to study the effects of biophysical factors, modulation of signaling pathways, extracellular matrix components, and culture conditions on the GSC phenotype. The advantages and disadvantages of these model systems and their impact in the field of GSC research are discussed.

Biomarkers and therapeutic advances in glioblastoma multiforme.

Glioblastoma multiforme (GBM) is a malignant tumor within the brain. Generally classified as primary and secondary with several different subtypes, ample molecular biomarkers have risen throughout the years which have garnered the attention of researchers. The advancements in genomics and proteomics have allowed researchers to gather prominent molecular biomarkers. All these biomarkers are gathered by means of biopsy or bodily fluid sample collection and are quantitatively analyzed by polymerase chain reaction coupled with other computational technologies. This review highlights the significance, regulation and prevalence of molecular biomarkers such as O6 -methylguanine-DNA methyltransferase, epidermal growth factor receptor vIII, isocitrate dehydrogenase mutation and several others which expressed differently in different types and molecular subtypes of GBM. The discoveries and roles of GBM-specific microRNAs including miR-21 and miR-10b as biomarkers with promising prognostic values were also delineated. The role and mechanism of biomarkers in GBM tumorigenesis are essential in the development of therapy for patients suffering from the disease itself. Thus, this review also discusses the mechanisms, effects and limitations of therapy such as temozolomide, viral gene transfer, biomarker-based vaccines or even engineered T cells for more specific responses. Biomarkers have displayed a high value and could eventually be utilized as drug targets. It is hoped that by combining different aspects of the disease which present with different biomarkers could lead to the development of a robust, effective and innovative take on GBM therapy.

Human SLFN5 is a transcriptional co-repressor of STAT1-mediated interferon responses and promotes the malignant phenotype in glioblastoma.

We provide evidence that the IFN-regulated member of the Schlafen (SLFN) family of proteins, SLFN5, promotes the malignant phenotype in glioblastoma multiforme (GBM). Our studies indicate that SLFN5 expression promotes motility and invasiveness of GBM cells, and that high levels of SLFN5 expression correlate with high grade gliomas and shorter overall survival in patients suffering from GBM. In efforts to uncover the mechanism by which SLFN5 promotes GBM tumorigenesis, we found that this protein is a transcriptional co-repressor of STAT1. Type-I IFN treatment triggers the interaction of STAT1 with SLFN5, and the resulting complex negatively controls STAT1-mediated gene transcription via interferon stimulated response elements (ISRE). Thus, SLFN5 is both an IFN-stimulated response gene and a repressor of IFN-gene transcription, suggesting the existence of a negative-feedback regulatory loop that may account for suppression of antitumor immune responses in glioblastoma.

TDP-43/HDAC6 axis promoted tumor progression and regulated nutrient deprivation-induced autophagy in glioblastoma.

Glioblastoma Multiforme (GBM) is a lethal primary brain tumor with poor survival lifespan and dismal outcome. Surgical resection of GBM is greatly limited due to the biological significance of brain, giving rise to tumor relapse in GBM patients. Transactive response DNA binding protein-43 (TDP-43) is a DNA/RNA-binding protein known for causing neurodegenerative diseases through post-translational modification; but little is known about its involvement in cancer development. In this study, we found that nutrient deprivation in GBM cell lines elevated TDP-43 expression by a mechanism of evasion from ubiquitin-dependent proteolytic pathway, and subsequently activated the autophagy process. Exogenous overexpression of TDP-43 consistently activated autophagy and suppressed stress-induced apoptosis. The inhibition of autophagy in TDP-43-overexpressing cells effectively increased the apoptotic population under nutrition shortage. Furthermore, we demonstrated that HDAC6 was involved in the activation of autophagy in TDP-43-overexpressing GBM cell lines. The treatment with SAHA, a universal HDAC inhibitor, significantly reduced TDP-43-mediated anti-apoptotic effect. Additionally, the results of immunohistochemistry showed that TDP-43 and HDAC6 collaborated in GBM-tumor lesions and negatively correlated with the relapse-free survival of GBM patients. Taken together, our results suggest that the TDP-43-HDAC6 signaling axis functions as a stress responsive pathway in GBM tumorigenesis and combats nutrient deprivation stress via activating autophagy, while inhibition of HDAC6 overpowers the pathway and provides a novel therapeutic strategy against GBM.

Upregulation of miR-181a suppresses the formation of glioblastoma stem cells by targeting the Notch2 oncogene and correlates with good prognosis in patients with glioblastoma multiforme

Glioblastoma stem-like cells (GSCs) are responsible for the initiation and progression of glioblastoma multiforme (GBM), and microRNAs (miRNAs) play an important role in this disease. However, the mechanisms underlying the role of miRNAs in the stemness of GSCs have not been completely elucidated. We previously showed that miR-181a is downregulated in GBM and may predict prognosis in patients with this disease. Here, we demonstrate that the upregulation of miR-181a suppressed GSC formation and inhibited GBM tumorigenesis by targeting the Notch2 oncogene. We found that miR-181a was downregulated in GSCs derived from human glioblastoma U87MG and U373MG cells. The high expression of miR-181a inhibited the levels of stemness-related markers CD133 and BMI1, attenuated sphere proliferation, promoted cell apoptosis, and reduced the tumorigenicity of GSCs. MiR-181a decreased the expression of Notch2 by targeting the 3’-untranslated region of its mRNA. Notch2 overexpression inhibited the effects of miR-181a downregulation on GSCs, and was negatively correlated with miR-181a expression. Moreover, high Notch2 expression together with low miR-181a expression was correlated with a shorter median overall survival for GBM patients. Together, these data show that miR-181a may play an essential role in GSC formation and GBM progression by targeting Notch2, suggesting that Notch2 and miR-181a have potential prognostic value as tumor biomarkers in GBM patients.