Malignant Progression Of Glioma Research Articles

MicroRNA expression patterns in the malignant progression of gliomas and a 5-microRNA signature for prognosis.

MicroRNAs (miRNAs) are directly involved in the progression in various cancers. To date, no systematic researches have been performed on the expression pattern of miRNA during progression from low grade gliomas to anaplastic gliomas or secondary glioblastomas and those prognostic miRNAs in anaplastic gliomas and secondary glioblastomas. In the present study, high-throughput microarrays were used to measure miRNA expression levels in 116 samples in the different progression stages of glioma. We found that miRNA expression pattern totally altered when low grade gliomas progressed to anaplastic gliomas or secondary glioblastomas. However, anaplastic gliomas and secondary glioblastomas have similar expression pattern in miRNA level. Furthermore, we developed a five-miRNA signature (two protective miRNAs-miR-767-5p, miR-105; three risky miRNAs: miR-584, miR-296-5p and miR-196a) that could identify patients with a high risk of unfavorable outcome in anaplastic gliomas regardless of histology type. It should be highlighted that the five-miRNA signature can also identify patients who had a high risk of unfavorable outcome in secondary and TCGA Proneural glioblastomas, but not Neural, Classical and Mesenchymal glioblastomas. Taken together, our results demonstrate that miRNA expression patterns in the malignant progression of gliomas and a novel prognostic classifier, the five-miRNA signature, serve as a prognostic marker for patient risk stratification in anaplastic gliomas, Secondary and Proneural glioblastomas.

EG-13 * GENOME-WIDE METHYLATION ANALYSIS IDENTIFIES GENOMIC DNA DEMETHYLATION DURING MALIGNANT PROGRESSION OF GLIOMAS

Low-grade gliomas often undergo malignant progression, and these transformations are a leading cause of death in patients with low-grade gliomas. However, the molecular mechanisms underlying malignant tumor progression are still not well understood. Recent evidence indicates that epigenetic deregulation is an important cause of gliomagenesis; therefore, we examined the impact of epigenetic changes during malignant progression of low-grade gliomas. Specifically, we used the Illumina Infinium Human Methylation 450K BeadChip to perform genome-wide DNA methylation analysis of 120 gliomas and four normal brains. This study sample included 25 matched-pairs of initial low-grade gliomas and recurrent tumors (temporal heterogeneity) and 20 of the 25 recurring tumors recurred as malignant progressions, and one matched-pair of newly emerging malignant lesions and pre-existing lesions (spatial heterogeneity). Analyses of methylation profiles demonstrated that most low-grade gliomas in our sample (43/51; 84%) had a CpG island methylator phenotype (G-CIMP). Remarkably, approximately 50% of secondary glioblastomas that had progressed from low-grade tumors with the G-CIMP status exhibited a characteristic partial demethylation of genomic DNA during malignant progression, but other recurrent gliomas showed no apparent change in DNA methylation pattern. Interestingly, we found that most loci that were demethylated during malignant progression were located outside of CpG islands. The information of histone modifications patterns in normal human astrocytes and embryonal stem cells also showed that the ratio of active marks at the site corresponding to DNA demethylated loci in G-CIMP-demethylated tumors was significantly lower; this finding indicated that most demethylated loci in G-CIMP-demethylated tumors were likely transcriptionally inactive. A small number of the genes that were upregulated and had demethylated CpG islands were associated with cell cycle-related pathway. In summary, we demonstrated that characteristic DNA demethylation occurred during malignant progression of a subset of low-grade gliomas. The mechanisms underlying and consequences of such DNA demethylation should be studied further.

Mannose phosphate isomerase regulates fibroblast growth factor receptor family signaling and glioma radiosensitivity.

Asparagine-linked glycosylation is an endoplasmic reticulum co- and post- translational modification that enables the transit and function of receptor tyrosine kinase (RTK) glycoproteins. To gain insight into the regulatory role of glycosylation enzymes on RTK function, we investigated shRNA and siRNA knockdown of mannose phosphate isomerase (MPI), an enzyme required for mature glycan precursor biosynthesis. Loss of MPI activity reduced phosphorylation of FGFR family receptors in U-251 and SKMG-3 malignant glioma cell lines and also resulted in significant decreases in FRS2, Akt, and MAPK signaling. However, MPI knockdown did not affect ligand-induced activation or signaling of EGFR or MET RTKs, suggesting that FGFRs are more susceptible to MPI inhibition. The reductions in FGFR signaling were not caused by loss of FGF ligands or receptors, but instead were caused by interference with receptor dimerization. Investigations into the cellular consequences of MPI knockdown showed that cellular programs driven by FGFR signaling, and integral to the clinical progression of malignant glioma, were impaired. In addition to a blockade of cellular migration, MPI knockdown also significantly reduced glioma cell clonogenic survival following ionizing radiation. Therefore our results suggest that targeted inhibition of enzymes required for cell surface receptor glycosylation can be manipulated to produce discrete and limited consequences for critical client glycoproteins expressed by tumor cells. Furthermore, this work identifies MPI as a potential enzymatic target for disrupting cell surface receptor-dependent survival signaling and as a novel approach for therapeutic radiosensitization.

Abstract 1440: Metabolic therapy reduces expression of PECAM-1/CD31 and decreases peritumoral edema in a mouse model of malignant glioma

Abstract Patients with malignant brain tumors have a median survival of approximately one year following diagnosis, regardless of currently available treatments which include surgery followed by radiation and chemotherapy. Improvement in the survival of brain cancer patients requires the design of new therapeutic modalities that take advantage of common phenotypes. One such phenotype is the metabolic dysregulation that is a hallmark of cancer cells. It has therefore been postulated that one approach to treating brain tumors may be by metabolic alteration such as that which occurs through the use of the ketogenic diet (KD). The KD is high-fat, low-carbohydrate diet that induces ketosis and has been utilized for the non-pharmacologic treatment of refractory epilepsy. We and others have shown that this diet enhances survival and potentiates standard therapy in mouse models of malignant gliomas, yet the anti-tumor mechanisms are not fully understood. It has been previously shown that caloric restriction, which induces ketosis, reduces microvessel density in mouse and human brain tumor models, suggesting an anti-angiogenic effect. We now report that in animals fed KetoCal® (KC) (4:1 fat:protein/carbohydrates) ad libitum, peritumoral edema is significantly reduced early in tumor progression when compared to those fed a standard rodent diet (SD). Western blot analysis showed a reduction of platelet endothelial cell adhesion molecule 1 (PECAM1/CD31) in tumors from animals maintained on KC. These results were supported by immunohistochemical staining for CD31 which also revealed abnormal vessel structure in the tumors from animals fed SD but not in those fed KC, suggesting a normalizing effect by the KC. Furthermore gene expression profiling demonstrated that KC decreases expression of a group of genes involved in angiogenesis and vessel structuring including the genes encoding vascular endothelial growth factor B (VEGFB) and angiopoetin 1 receptor (TEK), integrin beta 1 (ITGB1), urokinase-type plasminogen activator (PLAU) and tissue inhibitor of metalloproteases 1 (TIMP1). Taken together our data suggests that KC alters the angiogenic processes involved in malignant progression of gliomas. A greater understanding of the effects of the ketogenic diet as an adjuvant therapy will allow for a more rational approach to its clinical use. Citation Format: Eric C. Woolf, Julie A. Charlton, Qingwei Liu, Gregory Turner, Mark C. Preul, Adrienne C. Scheck. Metabolic therapy reduces expression of PECAM-1/CD31 and decreases peritumoral edema in a mouse model of malignant glioma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1440. doi:10.1158/1538-7445.AM2014-1440

Abstract 1402: Regulation of Id2 In the proliferation of glioma-initiating neural progenitor cells

Abstract There are more than 14,000 new cases of malignant high grade glioma diagnosed each year in the US, and although surgical resection, radiation, and cytotoxic therapies are available, these current treatment methods are not curative. Inhibitor of DNA Binding 2 (Id2), a helix-loop-helix (HLH) protein, functions as a dominant negative inhibitor of basic helix-loop-helix (bHLH) transcription factors and is highly expressed in glioma. Recent data from our laboratory defines a critical role for Id2 in the pathogenesis of a subset of glioma known as proneural glioma. Id2 protein function has been characterized in neural progenitor cells (NPCs) where it acts to suppress differentiation and enhance cell cycle progression. These are two key characteristics that are shared with glioma-derived stem cells. We have identified three phosphorylation sites on Id2 in proliferating NPCs using mass spectrometry, and prepared altered Id2 molecules that cannot be phosphorylated at each of these sites. Id2-/- NPCs expressing WT and phosphorylation-site-ablated Id2 have been prepared to examine the role of Id2 phosphorylation in mediating its interactions with binding partners and in modulating the rate of proteasome-dependent degradation. We found an increased level of Id2 in NPCs expressing a mutant form of Id2 that cannot by phosphorylated when compared with NPCs expressing WT Id2. Moreover, the level of WT Id2 protein decreases when NPCs exit the cell cycle; however, unphosphorylated Id2 resists this degradation and exhibits a longer half-life. Stable isotope labeling by amino acids in cell culture (SILAC) experiments revealed that unphosphorylated Id2 molecules bind significantly less than WT Id2 to several anaphase promoting complex (APC) subunits. These findings suggested a possible mechanism for phosphorylation-dependent proteasome-mediated degradation of Id2 in NPCs. Understanding the effect of Id2 phosphorylation in modulating steady state levels of this important protein will inform future studies designed to identify pathways of interest in the transformation of NPCs and the malignant progression of NPC-initiated glioma. This work was supported in part by the Theodora B. Betz Foundation. Citation Format: Jaclyn Sullivan, Matthew Havrda, Brenton Paolella, Arminja Kettenbach, Scott Gerber, Mark A. Israel. Regulation of Id2 In the proliferation of glioma-initiating neural progenitor cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1402. doi:10.1158/1538-7445.AM2014-1402

Suppression of miR-184 in malignant gliomas upregulates SND1 and promotes tumor aggressiveness.

Malignant glioma is an aggressive cancer requiring new therapeutic targets. MicroRNAs (miRNAs) regulate gene expression post transcriptionally and are implicated in cancer development and progression. Deregulated expressions of several miRNAs, specifically hsa-miR-184, correlate with glioma development. Bioinformatic approaches were used to identify potential miR-184-regulated target genes involved in malignant glioma progression. This strategy identified a multifunctional nuclease, SND1, known to be overexpressed in multiple cancers, including breast, colon, and hepatocellular carcinoma, as a putative direct miR-184 target gene. SND1 levels were evaluated in patient tumor samples and human-derived cell lines. We analyzed invasion and signaling in vitro through SND1 gain-of-function and loss-of-function. An orthotopic xenograft model with primary glioma cells demonstrated a role of miR-184/SND1 in glioma pathogenesis in vivo. SND1 is highly expressed in human glioma tissue and inversely correlated with miR-184 expression. Transfection of glioma cells with a miR-184 mimic inhibited invasion, suppressed colony formation, and reduced anchorage-independent growth in soft agar. Similar phenotypes were evident when SND1 was knocked down with siRNA. Additionally, knockdown (KD) of SND1 induced senescence and improved the chemoresistant properties of malignant glioma cells. In an orthotopic xenograft model, KD of SND1 or transfection with a miR-184 mimic induced a less invasive tumor phenotype and significantly improved survival of tumor bearing mice. Our study is the first to show a novel regulatory role of SND1, a direct target of miR-184, in glioma progression, suggesting that the miR-184/SND1 axis may be a useful diagnostic and therapeutic tool for malignant glioma.

O4.07 * A NOVEL POLYCOMB FEED FORWARD LOOP IN GLIOBLASTOMA MULTIFORME

INTRODUCTION: Glioblastoma (GBM) is the most aggressive high grade glioma and the most common malignant adult brain tumour. Dysregulation of epigenetic mechanisms is an essential driver in the progression of malignant gliomas. Polycomb group proteins (PcG) are chromatin associated proteins that play an essential role in epigenetic regulation of gene expression by maintaining heritable gene repression. METHOD: We used genetically engineered mouse models to study overexpression of PcG gene Bmi1 in neural stem cells (NSC) and GBM initiating cells (GBM-IC). ChIP followed by target specific or genome wide screening was carried out and the results analysed in combination with gene expression as assessed by RNASeq. RESULTS: Overexpression of Bmi1 in NSC increased their proliferation and self-renewal. At the mechanistic level, in Bmi1Over NSC we observed downregulation of both the p21/Foxg1 and the ink4a/arf pathways, the latter of which coincided with the accumulation of H3K27me3 at the promoter region of the p16ink4a gene. This suggests that increased trimethylation of H3K27 is a core mechanism mediating the functional outcome of Bmi1 upregulation. To understand how aberrant H3K27me3 contributes to gliomagenesis, a genome wide ChIPSeq analysis for H3K27me3 and RNASeq were performed on Bmi1Over NSC and GBM-IC expressing similar level of Bmi1 and results of this analysis will also be presented. CONCLUSION: Elucidating the molecular mechanisms of the epigenetic dysregulation observed in high grade gliomas is essential for the identification of novel biomarkers of early stage tumours and also offers an opportunity to identify novel druggable targets or drug repositioning opportunities for more effective therapies.

P01.23 * NEUROTENSIN PROMOTES THE PROGRESSION OF MALIGNANT GLIOMA THROUGH NTSR1 AND IMPACTS THE PROGNOSIS OF GLIOMA PATIENTS

BACKGROUND: Neurotensin (NTS) functions as a neuromodulator and induces cellular proliferation and migration in various solid tumors. However, whether NTS can promote the progression of malignant glioma and its prognostic significance for glioma patients remain unclear. METHODS: NTS and its high-affinity receptor (NTSR1) expression levels in clinical glioma samples were detected by immunohistochemistry and immunobloting. The prognostic analysis in glioma patients were conducted online by R2 microarray analysis and the visualization platform. The proliferation of glioma cells were evaluated by CCK8 and BrdU incorporation assay. The celluar invasiveness were tested by wound healing model and the Matrigel transwell assay. A neutralizing antibody to NTS, NTSR1-selective antagonist SR48692 and NTSR1-siRNA were used to suppress the NTS stimulation. Erk1/2 phosphorylation was tested by immunobloting. The orthotopic glioma implantation model was established to examine the role of NTS and NTSR1 in the progression of glioma in vivo. RESULTS: Positive correlations were shown between the expression levels of NTS and NTSR1 with the pathological grade of gliomas. The high levels of NTS and NTSR1 expression indicate a worse prognosis in glioma patients. The proliferation and invasiveness of glioma cells could be enhanced by NTS stimulation and impaired by the inhibition of NTSR1 functions. NTS stimulated Erk1/2 phosphorylation in glioma cells, which could be reversed by treatment with SR48692 or NTSR1-siRNA. In vivo experiments showed that therapy with SR48692 significantly prolonged the survival length of glioma-bearing mice and inhibited glioma cell invasiveness in vivo. CONCLUSIONS: NTS promotes the proliferation and invasion of glioma via the activation of NTSR1 and its downstream signaling molecules, resulting in Erk1/2 phosphorylation. High levels of NTS and NTSR1 expression predict a bad prognosis in glioma patients.

Versican isoform V1 regulates proliferation and migration in high-grade gliomas.

Versican is a large chondroitin sulphate proteoglycan produced by several tumor cell types, including high-grade gliomas. Increased expression of distinct versican isoforms in the extracellular matrix plays a role in tumor cell growth, adhesion and migration. We have recently shown that transforming growth factor (TGF-beta)2, an important modulator of glioma invasion, interacts with versican isoforms V0/V1 during malignant progression of glioma in vitro. However, the distinct subtype of versican that modulates these effects could not be specified. Here, we show that transient down-regulation of V1 by siRNA leads to a significant reduction of proliferation and migration in glioblastoma cell lines and glioblastoma progenitor cells, whereas tumor cell attachment stays unaffected. We conclude that V1 plays a predominant role in modulating central pathophysiological mechanisms as proliferation and migration in glioblastoma. Considering that TGF-beta is a master regulator of glioma pathophysiology, and that V0/1 is induced by TGF-beta2, therapeutic regulation of V1 may induce meaningful effects on glioma cell migration not only in vitro, but also in vivo.

Cytokines: shifting the balance between glioma cells and tumor microenvironment after irradiation.

Malignant gliomas invariably recur after irradiation, showing radioresistance. Meanwhile, cranial irradiation can bring some risk for developing cognitive dysfunction. There is increasing evidence that cytokines play their peculiar roles in these processes. On the one hand, cytokines directly influence the progression of malignant glioma, promoting or suppressing tumor progression. On the other hand, cytokines indirectly contribute to the immunologic response against gliomas, exhibiting pro-inflammatory or immunosuppressive activities. We propose that cytokines are not simply unregulated products from tumor cells or immune cells, but mediators finely adjust the balance between glioma cells and tumor microenvironment after irradiation. The paper, therefore, focuses on the changes of cytokines after irradiation, analyzing how these mediate the response of tumor cells and normal cells to irradiation. In addition, cytokine-based immunotherapeutic strategies, accompanied with irradiation, for the treatment of gliomas are also discussed.

Differential expression of p42.3 in low- and high-grade gliomas.

BackgroundMalignant gliomas are the most common form of primary malignant brain tumor. It has recently been suggested that genetic changes are involved in the progression of malignant gliomas. In previous studies, a novel gene, p42.3, was characterized as a tumor-specific gene that encodes a mitosis phase–dependent expression protein which is expressed in gastric cancer, but not in matched normal tissues.MethodsIn a series of 200 human brain gliomas and 13 normal tissues, we performed RT-PCR and mRNA in situ hybridization for analysis of p42.3 gene expression in gliomas, including astrocytoma (grade 2), oligoastrocytomas (grade 2), anaplastic oligoastrocytomas (grade 3), glioblastomas (grade 4) and normal tissues. Also, the mRNA expression was detected in gliomas by in situ hybridization. After producing polyclonal antibody to p42.3, we further tested p42.3 protein expression in astrocytomas and glioblastomas by immunohistochemistry and Western blot analysis.ResultsOur results demonstrated that overexpression of the p42.3 gene is detected in gliomas, but not in normal brain tissues. Importantly, p42.3 mRNA expression is correlated with the pathological features of gliomas. In addition, p42.3 protein is expressed in both the cytoplasm and the nucleus in astrocytomas, whereas this protein appeared in the cytoplasm in glioblastomas.ConclusionsThese results indicate that p42.3 might be involved in carcinogenesis as a potential molecular marker for malignant gliomas.

Correlation of hypoxia measured by fluorine-18 fluoroerythronitroimidazole (18F-FETNIM) PET/CT and the malignant progression of gliomas.

11100 Background: Hypoxia is important in the biology of human gliomas. PET offers a noninvasive method to differentiate individual tumor biology and modify treatment accordingly. The development o...

The Anti-Migratory Effect of Cirsium japonicum Pharmacopuncture in C6 Glioma Cell

Objectives : Cirsium japonicum is a traditional Korean medicine that has been used in the treatment of inflammatory diseases such as appendicitis, hepatitis, pulmonary abscess and tumor. The aim of study was to elucidate anti-migratory activity of CJP(Cirsium japonicum pharmacopuncture) through regulation of inflammatory mediators in C6 glioma cell. Methods : Nitric oxide(NO) production was determined by using nitrite assay. The cell migration was analyzed by wound-healing assay and Boyden chamber assay. The expression levels of iNOS, and protein kinase C(PKC)- were measured by western blotting assay. Results : CJP showed a significant decrease on NO production. Moreover, glioma cell migration was effectively suppressed by CJP. Furthermore, CJP inhibited the expressions of iNOS and PKC- in C6 glioma cells. Conclusions : These results suggest that CJP inhibits glioma cell migration and iNOS expression through regulation of PKC-. Therefore, it is expected that CJP could be an effective agents for blocking malignant progression of glioma.

Impact of MACC1 on human malignant glioma progression and patients' unfavorable prognosis

Metastasis-associated in colon cancer 1 (MACC1) has been established as an independent prognostic indicator of metastasis formation and metastasis-free survival for patients with colon cancer and other solid tumors. However, no data are available concerning MACC1 expression in human astrocytic tumors. Glioblastoma multiforme (GBM) is the most prevalent primary brain tumor of adulthood, and due to its invasive and rapid growth, patients have unfavorable prognoses. Although these tumors rarely metastasize, their invasive and migratory behavior is similar to those of metastatic cells of tumors of different origin. Thus, we hypothesized that MACC1 may be involved in progression of human gliomas. We performed real-time measurements of proliferation and migration in MACC1-transfected GBM cell lines (U138, U251) and evaluated tumor formation in organotypic hippocampal slice cultures of mice. Semiquantitative and quantitative real-time reverse transcription PCR analyses were performed for MACC1 and for its transcriptional target c-Met in human astrocytoma of World Health Organization grade II (low-grade astrocytoma) and GBM biopsies. Data were validated by MACC1 immunohistochemistry in independent matched samples of low-grade astrocytoma and GBM. MACC1 increases the proliferative, migratory, and tumor-formation abilities of GBM cells. The c-Met inhibitor crizotinib reduced MACC1-induced migration and tumor formation in organotypic hippocampal slice cultures of mice. Analyzing patients' biopsies, MACC1 expression increased concomitantly with increasing World Health Organization grade. Moreover, MACC1 expression levels allowed discrimination of dormant and recurrent low-grade astrocytomas and of primary and secondary GBM. Strong MACC1 expression correlated with reduced patient survival. MACC1 may represent a promising biomarker for prognostication and a new target for treatment of human gliomas.

Expression of osteopontin and matrix metalloproteinase-9 and vascular endothelial growth factor in glioma and their clinical significance

endothelial growth factor (VEGF) in tumor tissues and its relationship with tumor grade and prognosis in patients with glioma.Methods The immunohistochemical SP method was used to detect the expression of MMP-9 and VEGF in 50 cases of glioma and 30 cases of normal brain tissue.The correlation between the expression of MMP-9 and VEGF and grading characteristics of glioma was analyzed.Results In 30 cases of normal brain tissues,the expression of MMP-9 protein was negative,and VEGF protein positive expression rate was 26.7％ (8/30).The expression positive rate of MMP-9 and VEGF in gliomas was 68.0％ (34/50),and 76.0％ (38/50) respectively.There was significant difference in the MMP-9 and VEGF expression between low and high malignant groups of gliomas (P ＜ 0.05).Conclusion The upregulated MMP-9 and VEGF in gliomas is associated with malignant progression of gliomas and may play synergic effects in the occurrence and development of gliomas. Key words: Glioma; Matrix metalloproteinase-9; Vascular endothelial growth factor

Comprehensive analysis of the functional microRNA–mRNA regulatory network identifies miRNA signatures associated with glioma malignant progression

Glioma is the most common and fatal primary brain tumour with poor prognosis; however, the functional roles of miRNAs in glioma malignant progression are insufficiently understood. Here, we used an integrated approach to identify miRNA functional targets during glioma malignant progression by combining the paired expression profiles of miRNAs and mRNAs across 160 Chinese glioma patients, and further constructed the functional miRNA–mRNA regulatory network. As a result, most tumour-suppressive miRNAs in glioma progression were newly discovered, whose functions were widely involved in gliomagenesis. Moreover, three miRNA signatures, with different combinations of hub miRNAs (regulations≥30) were constructed, which could independently predict the survival of patients with all gliomas, high-grade glioma and glioblastoma. Our network-based method increased the ability to identify the prognostic biomarkers, when compared with the traditional method and random conditions. Hsa-miR-524-5p and hsa-miR-628-5p, shared by these three signatures, acted as protective factors and their expression decreased gradually during glioma progression. Functional analysis of these miRNA signatures highlighted their critical roles in cell cycle and cell proliferation in glioblastoma malignant progression, especially hsa-miR-524-5p and hsa-miR-628-5p exhibited dominant regulatory activities. Therefore, network-based biomarkers are expected to be more effective and provide deep insights into the molecular mechanism of glioma malignant progression.

RAB38 confers a poor prognosis, associated with malignant progression and subtype preference in glioma

RAB38 is a new member of the RAB small G protein family that regulates intracellular vesicle trafficking. RAB38 is expressed in melanocytes and it has been shown that a point mutation in the postulated GTP-binding domain of RAB38 is the gene responsible for human Hermansky-Pudlak syndrome. However, the prognostic and molecular features of tumors with RAB38 expression is still unclear, as well as glioma. Whole genome mRNA expression microarray data on 220 glioma samples from the Chinese glioma genome atlas (CGGA) database (http://www.cgga.org.cn) was applied as discovery set. Each grade of glioma patients was analyzed by the Kaplan-Meier method. To determine the protein expression levels of RAB38, further 82 glioma tissues were stained by immunohistochemistry. Three additional datasets (TCGA, GSE16011 and Rembrandt) were obtained as validation sets. The functional annotation of RAB38 was analyzed by Gene ontology (GO) analysis and Gene set variation analysis (GSVA) in 89 glioblastomas (GBMs). High RAB38 expression was mainly increased in high-grade gliomas, and high RAB38 expression also conferred high mortality of glioma in the CGGA cohort. RAB38 showed a mesenchymal subtype, G3 subtype and isocitrate dehydrogenase 1 (IDH1) wild-type preference. GO and GSVA analysis showed that RAB38 was significantly correlated with migration. These results were validated in other 3 datasets. The expression levels of RAB38 were significantly associated with grade progression as well as prognosis in gliomas. RAB38 is an important prognostic biomarker and potential therapeutic target in gliomas.

Epigenetic silencing of KAZALD1 confers a better prognosis and is associated with malignant transformation/progression in glioma

In order to more thoroughly analyze aberrant DNA methylation in glioma, we applied a large cohort methylation microarray including 119 glioma samples. Six genes, ADCY1, KAZALD1, KLF4, SLMAP, TETRAN and TP53INP1, were screened out through significance analysis of microarray (SAM), survival Cox-regression and certain other pre-set conditions. We focused on the KAZALD1 oncogene. KAZALD1, also known as IGFBP-rP10, belongs to the IGFBP family. We found that KAZALD1 was hypomethylated in high-grade glioma (anaplastic gliomas and glioblastomas) compared to low-grade glioma (astrocytoma, oligodendrocytoma and oligoastrocytoma) using methylation microarrays (p<0.001). Immunohistochemistry (IHC) of 91 glioma samples showed that the KAZALD1 expression scores of high-grade glioma samples were higher compared to the scores of low-grade gliomas (p<0.001). In high-grade gliomas, overall survival (OS) was shorter for patients with KAZALD1 hypomethylation or overexpression compared to those without. Decreased KAZALD1 expression in glioma inhibited cell proliferation and invasion both invitro and invivo. On the basis of these observations and the results from subset analysis, it is reasonable to conclude that KAZALD1 promoter hypomethylation is an important prognostic biomarker in glioma. KAZALD1 promotes glioma malignant progression through invasion and proliferation.

MiR-145 functions as a tumor-suppressive RNA by targeting Sox9 and adducin 3 in human glioma cells

MicroRNAs (miRNAs) are increasingly being recognized as being involved in cancer development and progression in gliomas. Using a model cell system developed in our lab to study glioma progression comprising human neuroglial culture (HNGC)-1 and HNGC-2 cells, we report here that miR-145 is one of the miRNAs significantly downregulated during malignant transformation in glioblastoma multiforme (GBM). In a study using tumor samples derived from various glioma grades, we show that expression of miR-145 is decreased in a graded manner, with GBM patients showing lowest expression relative to lower-grade gliomas (P < .05) and normal brain tissues (P < .0001). Functional studies involving ectopic expression of miR-145 in glioma cells had a negative impact on cell proliferation and tumor development, as well as invasion and induced apoptosis, providing further support to the concept that inactivation of miR-145 is important for glioma disease pathogenesis. More notably, these growth-suppressive effects of miR-145 are mediated through its target proteins Sox9 and the cell adhesion-associated molecule adducin 3 (ADD3). Inhibiting Sox9 and ADD3 rescued effects of miR-145 loss. Interestingly, miR-145 loss in glioma cells led to overexpression of molecules involved in cell proliferation, like cyclin D1, c-myc, and N-myc, as well as enhanced expression of cell adhesion- and invasion-related molecules N-cadherin and E-cadherin, an effect which was again restored upon miR-145 overexpression in glioma cells. The miR-145 promoter was methylated at its cytosine-phosphate-guanine (CpG) islands in the glioma cell lines studied. Our study demonstrates that miR-145 has a tumor-suppressive function in glioblastoma in that it reduces proliferation, adhesion, and invasion of glioblastoma cells, apparently by suppressing the activity of oncogenic proteins Sox9 and ADD3. Reduced levels of miR-145 may lead to neoplastic transformation and malignant progression in glioma due to unregulated activity of these proteins.

Involvement of FOS-mediated miR-181b/miR-21 signalling in the progression of malignant gliomas

Recently, a group of microRNAs (miRNAs) were shown to be dysregulated in gliomas, and involved in glioma development. However, the effect of miRNA–miRNA functional networks on gliomas is poorly understood. In this study, we identified that FBJ murine osteosarcoma viral oncogene homolog (FOS)-mediated miR-181b/miR-21 signalling was critical for glioma progression. Using microarrays and quantitative RT-PCR (qRT-PCR), we found increased FOS in high grade gliomas. FOS depletion (via FOS-shRNA), inhibited invasion and promoted apoptosis in glioma cells. Using microarrays, combined with Pearson correlation analysis, we found FOS positively correlated with miR-21 expression. Reduction of FOS inhibited miR-21 expression by binding to the miR-21 promoter using luciferase reporter assays. Introduction of miR-21 abrogated FOS knockdown-induced cell invasion and apoptosis. Moreover, bioinformatics and luciferase reporter assays showed that miR-181b modulated FOS expression by directly targeting the binding site within the 3′UTR. Expression of FOS with a FOS cDNA lacking 3′UTR overrided miR-181b-induced miR-21 expression and cell function. Finally, immunohistochemistry (IHC) and in situ hybridisation (ISH) analysis revealed a significant correlation in miR-181b, FOS and miR-21 expression in nude mouse tumour xenograft and human glioma tissues. To our knowledge, it is the first time to demonstrate that miR-181b/FOS/miR-21 signalling plays a critical role in the progression of gliomas, providing important clues for understanding the key roles of transcription factor mediated miRNA–miRNA functional network in the regulation of gliomas.