CGCG clinical practice guidelines for the management of adult diffuse gliomas

Changing paradigms for targeted therapies against diffuse infiltrative gliomas: tackling a moving target

Introduction: Gliomas are highly heterogeneous primary brain tumors which result in a disproportionately high degree of morbidity and mortality despite their locoregional occurrence. Advances in the understanding of the biological makeup of these malignancies have yielded a number of potential tumor-driving pathways which have been identified as rational targets for therapy. However, early trials of agents that target these pathways have uniformly failed to yield improvement in outcomes in patients with malignant gliomas. Areas covered: This review provides an overview of the most common biological features of gliomas and the strategies to target the same; in addition, the current status of immunotherapy and biological therapies are outlined and the future directions to tackle the challenges of therapy for gliomas are examined. Expert opinion: The limitations of current treatments are attributed to the inability of most of these agents to cross the blood-brain barrier and to the intrinsic heterogeneity of the tumors that result in treatment resistance. The recent emergence of immune-mediated and biological therapies and of agents that target metabolic pathways in gliomas have provided strategies that may overcome tumor heterogeneity and ongoing trials of such agents are anticipated to yield improved outcomes.

CircPCMTD1 Acts as the Sponge of miR-224-5p to Promote Glioma Progression

Glioma is the most common malignant tumor of the central nervous system with high morbidity and mortality. Circular RNAs (circRNAs) are abundant non-coding RNAs, which contribute to tumor progression by competing with other endogenous RNAs such as microRNA (miRNA). MiRNA are a class of small non-coding RNAs, which interrupt the translation of target mRNAs. CircPCMTD1 (hsa-circ-0001801) is a newly discovered circRNA that was found to be significantly upregulated in glioma. However, its function is unclear. In this study, circPCMTD1 upregulation promoted the cell viability, migration and invasion dramatically, while the inhibition of circPCMTD1 led to a significant reduction of tumor growth in vivo. MiRNAs microarray analyses on circPCMTD1 silencing models in U251 and U118MG cells were performed, and the results suggested that circPCMTD1 knockdown could upregulate the expression of miR-224-5p and downregulate the expression of mTOR, one of miR-224-5p targets, in both cell lines. According to the prediction from circular RNA interactome and Targetscan, there was a complementary sequence in circPCMTD1 for miR-224-5p. Dual-luciferase reporter assay demonstrated that circPCMTD1 were targets of miR-224-5p. RIP assay was also performed to further confirm their directly interaction. Overexpression of miR-224-5p inhibited the viability and proliferation, migration, and invasion of U251 and U118MG glioma cells. In conclusion, circPCMTD1 could contribute to the promotion of glioma progression, and it may serve as the sponge of miR-224-5p to exert its function.

RELB: A novel prognostic marker for glioblastoma as identified by population-based analysis

Glioblastoma multiforme (GBM) is the most common and malignant type of glioma, with a poor prognosis for patients. The survival time of patients varies greatly due to the complexity of the human genome, which harbors diverse oncogenic drivers. In order to identify the specific driving factors, 325 glioma samples from the Chinese Glioma Genome Atlas (CGGA) database were analyzed in the present study. The level of RELB proto-oncogene, NF-κβ subunit (RELB) expression increased with the pathological grade progression of the gliomas, and higher expression levels were present in the mesenchymal subtype and isocitrate dehydrogenase 1 (IDH1) wild-type gliomas. This RELB expression pattern was identified in the CGGA database and observed in three large independent databases. In patients with GBM from the CGGA database, a higher RELB expression level was associated with a shorter survival time, a mesenchymal subtype and IDH1 wild-type gliomas. Kaplan-Meier survival analysis, survival nomograms and Cox analysis demonstrated an independent prognostic value for RELB expression. Moreover, biological function analysis indicated the association of RELB with the ‘immune response’, ‘cell activation’ and the ‘apoptotic process’. In addition, RELB expression levels exhibited a negative correlation with the levels of microRNA (miR)-139-5p and miR-139-3p. The present study identified the pathological and biological roles of RELB in glioma and revealed its independent prognostic effect. These results suggested that RELB may be used as a prognostic biomarker and potential therapeutic target in glioma.

Immune microenvironments differ in immune characteristics and outcome of glioblastoma multiforme

Understanding the interactions between tumors and the host immune system holds great promise to uncover biomarkers for targeted therapies, predict the prognosis of patients and guide clinical treatment. However, the immune signatures of glioblastoma multiforme (GBM) remain largely unstudied in terms of systematic analyses. We aimed to classify GBM samples according to immune‐related genes and complement the existing immunotherapy system knowledge. In this study, we designed a strategy to identify 3 immune subtypes representing 3 different immune microenvironments (M1‐M3) and associated with prognosis. The 3 subtypes were significantly different in terms of specific immune characteristics (immune cell subpopulations, immune responses, immune cells, and checkpoint gene interactions). In additional, copy number variations and methylation changes were identified that correlated with genes related to a worse prognosis subtype in the microenvironment. More importantly, in M3 (worst prognosis subtype) and M2 (best prognosis subtype), the interaction between immune cells and checkpoint genes was different, which had an important effect on the prognosis. Finally, we used risk scores of immune cells and checkpoint genes to evaluate the prognosis of GBM patients and validated the results with 3 independent datasets. Disordered interactions between immune cells and checkpoint genes result in a change in the immune microenvironment and affects the prognosis of patients. We propose that a better understanding of the immune microenvironment of advanced cancers may provide new insights into immunotherapy.

A quantitative SVM approach potentially improves the accuracy of magnetic resonance spectroscopy in the preoperative evaluation of the grades of diffuse gliomas

Objectives

To investigate the association between proton magnetic resonance spectroscopy (¹H-MRS) metabolic features and the grade of gliomas, and to establish a machine-learning model to predict the glioma grade.

Methods

This study included 112 glioma patients who were divided into the training (n = 74) and validation (n = 38) sets based on the time of hospitalization. Twenty-six metabolic features were extracted from the preoperative ¹H-MRS image. The Student's t-test was conducted to screen for differentially expressed features between low- and high-grade gliomas (WHO grades II and III/IV, respectively). Next, the minimum Redundancy Maximum Relevance (mRMR) algorithm was performed to further select features for a support vector machine (SVM) classifier building. Performance of the predictive model was evaluated both in the training and validation sets using ROC curve analysis.

Results

Among the extracted ¹H-MRS metabolic features, thirteen features were differentially expressed. Four features were further selected as grade-predictive imaging signatures using the mRMR algorithm. The predictive performance of the machine-learning model measured by the AUC was 0.825 and 0.820 in the training and validation sets, respectively. This was better than the predictive performances of individual metabolic features, the best of which was 0.812.

Conclusions

¹H-MRS metabolic features could help in predicting the grade of gliomas. The machine-learning model achieved a better prediction performance in grading gliomas than individual features, indicating that it could complement the traditionally used metabolic features.

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¹H-MRS metabolic features could help in predicting the grades of gliomas.

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The machine-learning model performed better than individual metabolic features.

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The use of machine-learning model can complement the metabolic features.

miR-526b-3p serves as a prognostic factor and regulates the proliferation, invasion, and migration of glioma through targeting WEE1

Background: MicroRNAs play important roles in cancer progression including glioma. In this study, we aimed to explore the expression pattern, prognostic potential, and functional role of miR-526b-3p in human glioma.

Materials and methods: The expression of miR-526b-3p in glioma tissues and the adjacent non-tumor tissues was determined by quantitative RT-PCR. The chi-square test was performed to evaluate the statistical associations between miR-526b-3p level and patient characteristics. The prognostic value of miR-526b-3p was analyzed by Kaplan–Meier and Cox regression analyses. The function of miR-526b-3p was analyzed by MTT, colony formation assay, transwell assay, and flow cytometry analysis in vitro. The binding between miR-526b-3p and predicted target WEE1 was verified using dual luciferase assay and Western blot analysis.

Results: We found that miR-526b-3p expression was significantly downregulated in both glioma tissues and cell lines. Downregulation of miR-526b-3p was significantly associated with advanced WHO grade, lower KPS score, and inferior patient outcomes. Functional investigation indicated that overexpression of miR-526b-3p suppressed cell proliferation, migration, and invasion, and promoted apoptosis in glioma cell lines. Mechanically, WEE1 was identified as direct targets of miR-526b-3p and overexpression of WEE1 significantly suppressed the levels of WEE1. Moreover, re-introduction of WEE1 abrogates the suppression of motility and invasiveness induced by miR-526b-3p in glioma cells.

Conclusion: These findings indicate that miR-526b-3p may target WEE1 and inhibit glioma tumorigenesis and progression.

Identification of potential biomarkers related to glioma survival by gene expression profile analysis

BACKGROUND

Recent studies have proposed several gene signatures as biomarkers for different grades of gliomas from various perspectives. However, most of these genes can only be used appropriately for patients with specific grades of gliomas.

METHODS

In this study, we aimed to identify survival-relevant genes shared between glioblastoma multiforme (GBM) and lower-grade glioma (LGG), which could be used as potential biomarkers to classify patients into different risk groups. Cox proportional hazard regression model (Cox model) was used to extract relative genes, and effectiveness of genes was estimated against random forest regression. Finally, risk models were constructed with logistic regression.

RESULTS

We identified 104 key genes that were shared between GBM and LGG, which could be significantly correlated with patients' survival based on next-generation sequencing data obtained from The Cancer Genome Atlas for gene expression analysis. The effectiveness of these genes in the survival prediction of GBM and LGG was evaluated, and the average receiver operating characteristic curve (ROC) area under the curve values ranged from 0.7 to 0.8. Gene set enrichment analysis revealed that these genes were involved in eight significant pathways and 23 molecular functions. Moreover, the expressions of ten (CTSZ, EFEMP2, ITGA5, KDELR2, MDK, MICALL2, MAP 2 K3, PLAUR, SERPINE1, and SOCS3) of these genes were significantly higher in GBM than in LGG, and comparing their expression levels to those of the proposed control genes (TBP, IPO8, and SDHA) could have the potential capability to classify patients into high- and low- risk groups, which differ significantly in the overall survival. Signatures of candidate genes were validated, by multiple microarray datasets from Gene Expression Omnibus, to increase the robustness of using these potential prognostic factors. In both the GBM and LGG cohort study, most of the patients in the high-risk group had the IDH1 wild-type gene, and those in the low-risk group had IDH1 mutations. Moreover, most of the high-risk patients with LGG possessed a 1p/19q-noncodeletion.

CONCLUSION

In this study, we identified survival relevant genes which were shared between GBM and LGG, and those enabled to classify patients into high- and low-risk groups based on expression level analysis. Both the risk groups could be correlated with the well-known genetic variants, thus suggesting their potential prognostic value in clinical application.

Acidosis enhances the self-renewal and mitochondrial respiration of stem cell-like glioma cells through CYP24A1-mediated reduction of vitamin D

Acidosis is a significant feature of the tumor microenvironment in glioma, and it is closely related to multiple biological functions of cancer stem cells. Here, we found that the self-renewal ability, the mitochondrial activity and ATP production were elevated in stem cell-like glioma cells (SLCs) under acidic microenvironment, which promoted and maintained the stemness of SLCs. Under acidosis, 25-hydroxy vitamin D₃-24-hydroxylase (CYP24A1) was upregulated and catalyzed the fast degradation of 1α,25(OH)₂D₃. We further revealed that the active form of vitamin D (1α,25(OH)₂D₃) could inhibit the expression of stemness markers, attenuate acidosis-induced increase of self-renewal ability and mitochondrial respiration in stem cell-like glioma cells. Our study indicates that the acidosis–CYP24A1–vitamin D pathway may be a key regulator of the cancer stem cell phenotype in malignant glioma and point out the potential value for the utilization of vitamin D to target cancer stem cells and to restrain the growth of malignant glioma in the future.

ADAMTSL4, a Secreted Glycoprotein, Is a Novel Immune-Related Biomarker for Primary Glioblastoma Multiforme

Background

Researches on immunotherapy of glioblastoma multiforme (GBM, WHO grade IV) have increased exponentially in recent years. As a targeted therapy, a series of biomarkers have been identified in local tumor tissue, while circulating marker which could be detected in the body fluids is still lacking. ADAMTSL4, a secreted glycoprotein, was earlier found to play a critical role in a prognostic signature for primary GBM (pGBM). We aimed to investigate the role of ADAMTSL4 at transcriptome level and its relationship with clinical practice in pGBM.

Methods

A cohort of 88 pGBM patients with RNA-seq data from the Chinese Glioma Genome Atlas (CGGA) was analyzed, and 168 pGBM patients from TCGA were included as validation. Several bioinformatic methods and predictive tools were applied to investigate the ADAMTSL4-associated immune microenvironment status.

Results

We found that ADAMTSL4 was enriched in GBM (WHO grade IV), especially for those with IDH1/2 wild-type and MGMT unmethylated groups. According to the TCGA classification scheme, ADAMTSL4 can act as a potential marker for subtypes with poorer prognosis. Bioinformatic analyses revealed that ADAMTSL4 was significantly correlated to the immune-related processes in GBM (WHO grade IV), especially representing the infiltration of immune cells and complicated tumor microenvironment. Clinically, high expression of ADAMTSL4 was an independent indicator for poor prognosis.

Conclusion

The expression of ADAMTSL4 is closely related to the clinicopathologic characteristics of pGBM. Meanwhile, it may play a critical role in immune-related processes. As a secreted glycoprotein, ADAMTSL4 is a promising circulating biomarker for pGBM, deserving further investigations.

A novel analytical model of MGMT methylation pyrosequencing offers improved predictive performance in patients with gliomas

The methylation status of the promoter of MGMT gene is a crucial factor influencing clinical decision-making in patients with gliomas. MGMT pyrosequencing results are often dichotomized by a cut-off value based on an average of several tested CpGs. However, this method frequently results in a "gray zone", representing a dilemma for physicians. We therefore propose a novel analytical model for MGMT methylation pyrosequencing. MGMT CpG heterogeneity was investigated in 213 glioma patients in two tested cohorts: cohort A in which CpGs 75-82 were tested and cohort B in which CpGs 72-78 were tested. The predictive performances of the novel and traditional averaging models were compared in 135 patients who received temozolomide using receiver operating characteristic curves and Kaplan-Meier curves, and in patients stratified according to isocitrate dehydrogenase gene mutation status. The results were validated in an independent cohort of 65 consecutive patients with high-grade gliomas from the Chinese Glioma Genome Atlas database. Heterogeneity of MGMT promoter CpG methylation level was observed in most gliomas. The optimal cut-off value for each individual CpG varied from 4-16%. The current analysis defined MGMT promoter methylation as occurring when at least three CpGs exceeded their respective cut-off values. This novel analysis could accurately predict the prognosis of patients in the methylation "gray zone" according to the standard averaging method, and improved the area under the curves from 0.67, 0.76, and 0.67 to 0.70, 0.84, and 0.72 in cohorts A, B, and the validation cohort, respectively, demonstrating superiority of this analytical method in all three cohorts. Furthermore, the advantages of the novel analysis were retained regardless of WHO grade and isocitrate dehydrogenase gene mutation status. In conclusion, this novel analytical model offers an improved clinical predictive performance for MGMT pyrosequencing results and is suitable for clinical use in patients with gliomas.

Amino acid metabolism-related gene expression-based risk signature can better predict overall survival for glioma

Metabolic reprogramming has been proposed to be a hallmark of cancer. Aside from the glycolytic pathway, the metabolic changes of cancer cells primarily involve amino acid metabolism. However, in glioma, the characteristics of the amino acid metabolism‐related gene set have not been systematically profiled. In the present study, RNA sequencing expression data from 309 patients in the Chinese Glioma Genome Atlas database were included as a training set, while another 550 patients within The Cancer Genome Atlas database were used to validate. Consensus clustering of the 309 samples yielded two robust groups. Compared with Cluster1, Cluster2 correlated with a better clinical outcome. We then developed an amino acid metabolism‐related risk signature for glioma. Our results showed that patients in the high‐risk group had dramatically shorter overall survival than low‐risk counterparts in any subgroup, stratified by isocitrate dehydrogenase and 1p/19q status based on the 2016 World Health Organization classification guidelines. The 30‐gene signature showed better prognostic value than the traditional factors “age” and “grade” by analyzing the receiver operating characteristic curve with areas under curve of 0.966, 0.692, 0.898 and 0.975, 0.677, 0.885 for 3‐ and 5‐year survival, respectively. Moreover, univariate and multivariate analysis showed that the 30‐gene signature was an independent prognostic factor for glioma. Furthermore, Gene Ontology analysis and Gene Set Enrichment Analysis showed that tumors with a high risk score correlated with various aspects of the malignancy of glioma. In summary, we demonstrated a novel amino acid metabolism‐related risk signature for predicting prognosis for glioma.

ALDH1A3 induces mesenchymal differentiation and serves as a predictor for survival in glioblastoma

As aldehyde dehydrogenase (ALDH) is a novel stem cell marker, increasing studies have confirmed that high ALDH activity promotes tumorigenesis and progression in cancers. Some preliminary studies have found that ALDH1A3 may play an important role in glioma malignant progression, but so far there was no conclusive conclusion. The purpose of our study was to elucidate the mechanisms by which ALDH1A3 regulated in glioma and to provide practical tools for clinical application. Aldefluor, flow cytometry sorting and qRT-PCR were performed to verify the role of ALDH1A3 in ALDH activity maintenance. Transwell, immunofluorescence, glycolytic assays, and orthotopic xenograft models were used to explore ALDH1A3 bio-functions in GBM. LASSO-COX, COX survival analysis and Kaplan–Meier analysis were used to establish the prognostic evaluation system and predict postoperative chemotherapy sensitivity of GBMs. Our integrated study found that (1) ALDH1A3 associates with mesenchymal differentiation of GBM in Eastern and Western world patients. (2) ALDH1A3 plays a critical role in ALDH activity maintenance. (3) ALDH1A3 is an activator of mesenchymal transformation in GBM. (4) ALDH1A3-derived PMT markers’ molecular signature can predict 1-, 2-, and 3-year survival rates of GBMs precisely. In conclusion, ALDH1A3 was a major contributor to ALDH activity and a key driver in triggering mesenchymal transformation in GBM. ALDH1A3-based molecular classification scheme can help to improve guidance for prognosis forecasting and individualized treatment decision making for GBM patients.

PD-L2 expression is correlated with the molecular and clinical features of glioma, and acts as an unfavorable prognostic factor

Background: Gliomas are aggressive tumors with various molecular and clinical characteristics and exhibit strongly resistance to radio-chemotherapy. Programmed cell death 1 ligand 2 (PD-L2) is a cell surface protein, which was reported in many cancers, modulating cancer-associated immune responses, while the role of PD-L2 in gliomas remained unclear. Herein, we aimed to investigate the biological behaviors and clinical prognostic values of PD-L2 in gliomas.

Methods: Totally, we enrolled RNA sequencing data of 325 glioma samples from Chinese Glioma Genome Atlas (CGGA) as training cohort and RNA expression data of 1032 samples from The Cancer Genome Atlas (TCGA) dataset as validation cohort in this research. Then, the clinical and molecular characteristics, and the prognostic value of PD-L2 were analyzed.

Results: We found that PD-L2 expression level was significantly upregulated in higher grade glioma and IDH wild-type glioma. Receiver Operating Characteristic (ROC) analysis revealed that PD-L2 was a potential indicator of mesenchymal subtype. PD-L2 exhibited tight relationship with immune response and immune-modulating process in glioma. Moreover, PD-L2 expression level could predict unfavorable prognoses of patients independent of age, grade, IDH status and 1p/19q status.

Conclusions: Our study revealed that PD-L2 was closely related with inflammation and immune response. Patients with lower PD-L2 expression level tended to experience improved survival. Targeting PD-L2 may become a valuable approach for the treatment of gliomas in clinical practice.

Potential Epigenetic-Based Therapeutic Targets for Glioma

Glioma is characterized by a high recurrence rate, short survival times, high rates of mortality and treatment difficulties. Surgery, chemotherapy and radiation (RT) are the standard treatments, but outcomes rarely improve even after treatment. With the advancement of molecular pathology, recent studies have found that the development of glioma is closely related to various epigenetic phenomena, including DNA methylation, abnormal microRNA (miRNA), chromatin remodeling and histone modifications. Owing to the reversibility of epigenetic modifications, the proteins and genes that regulate these changes have become new targets in the treatment of glioma. In this review, we present a summary of the potential therapeutic targets of glioma and related effective treating drugs from the four aspects mentioned above. We further illustrate how epigenetic mechanisms dynamically regulate the pathogenesis and discuss the challenges of glioma treatment. Currently, among the epigenetic treatments, DNA methyltransferase (DNMT) inhibitors and histone deacetylase inhibitors (HDACIs) can be used for the treatment of tumors, either individually or in combination. In the treatment of glioma, only HDACIs remain a good option and they provide new directions for the treatment. Due to the complicated pathogenesis of glioma, epigenetic applications to glioma clinical treatment are still limited.

ISG20 promotes local tumor immunity and contributes to poor survival in human glioma

Recent evidence has confirmed that a mutation of the isocitrate dehydrogenase (IDH) gene occurs early in gliomagenesis and contributes to suppressed immunity. The present study aimed to determine the candidate genes associated with IDH mutation status that could serve as biomarkers of immune suppression for improved prognosis prediction. Clinical information and RNA-seq gene expression data were collected for 932 glioma samples from the CGGA and TCGA databases, and differentially expressed genes in both lower-grade glioma (LGG) and glioblastoma (GBM) samples were identified according to IDH mutation status. Only one gene, interferon-stimulated exonuclease gene 20 (ISG20), with reduced expression in IDH mutant tumors, demonstrated significant prognostic value. ISG20 expression level significantly increased with increasing tumor grade, and its high expression was associated with a poor clinical outcome. Moreover, increased ISG20 expression was associated with increased infiltration of monocyte-derived macrophages and neutrophils, and suppressed adaptive immune response. ISG20 expression was also positively correlated with PD-1, PD-L1, and CTLA4 expression, along with the levels of several chemokines. We conclude that ISG20 is a useful biomarker to identify IDH-mediated immune processes in glioma and may serve as a potential therapeutic target.

Elevated Na/H exchanger 1 (SLC9A1) emerges as a marker for tumorigenesis and prognosis in gliomas

Background

Sodium/hydrogen exchanger 1 (NHE1), encoded by the SLC9A1 gene (SoLute Carrier family 9A1) in humans, is the main H⁺ efflux mechanism in maintaining alkaline intracellular pH (pH_i) and Warburg effects in glioma. However, to date, there are no clinical studies exploring pharmacological inhibition of NHE1 protein in cancer treatment. In this study, we investigated NHE1 expression in gliomas and its relationship with glioma clinical outcome.

Methods

The Chinese Glioma Genome Atlas (CGGA) dataset containing transcriptome sequencing data of 325 glioma samples and the Cancer Genome Atlas (TCGA) with 698 glioma mRNAseq data were analyzed in this study. Mouse SB28 and GL26 intracranial syngeneic glioma models in C57BL/6 J mice were established to investigate NHE1 expression and impact of NHE1 protein inhibition with its inhibitor HOE642 on tumorigenesis and anti-PD1 therapy. Tumor angiogenesis, immunogenicity, and progression were assessed by immunofluorescence staining and flow cytometric profiling.

Results

Analysis of SLC9A1 mRNA expression in two data sets, CGGA and TCGA, reveals significantly higher SLC9A1 mRNA levels in higher grade gliomas. The SLC9A1 mRNA expression was especially enriched in isocitrate dehydrogenase (IDH)1/2 wild-type glioblastoma (GBM) and in mesenchymal glioma subtypes. Worsened survival probabilities were correlated with the elevated SLC9A1 mRNA levels in gliomas. The underlying mechanisms include promoting angiogenesis, and extracellular matrix remodeling. Increased SLC9A1 mRNA expression was also associated with tumor-associated macrophage accumulation. NHE1 inhibitor HOE642 reduced glioma volume, invasion, and prolonged overall survival in mouse glioma models. Blockade of NHE1 protein also stimulated immunogenic tumor microenvironment via activating CD8 T-cell accumulation, increasing expression of interferon-gamma (Ifng), and sensitized animals to anti-PD-1 therapy.

Conclusion

Our findings strongly suggest that NHE1 protein emerges as a marker for tumorigenesis and prognosis in glioma. Blocking NHE1 protein is a novel strategy for adjuvant anti-cancer therapies.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0923-z) contains supplementary material, which is available to authorized users.

A radiomic signature as a non-invasive predictor of progression-free survival in patients with lower-grade gliomas

Objective

The aim of this study was to develop a radiomics signature for prediction of progression-free survival (PFS) in lower-grade gliomas and to investigate the genetic background behind the radiomics signature.

Methods

In this retrospective study, training (n = 216) and validation (n = 84) cohorts were collected from the Chinese Glioma Genome Atlas and the Cancer Genome Atlas, respectively. For each patient, a total of 431 radiomics features were extracted from preoperative T2-weighted magnetic resonance images. A radiomics signature was generated in the training cohort, and its prognostic value was evaluated in both the training and validation cohorts. The genetic characteristics of the group with high-risk scores were identified by radiogenomic analysis, and a nomogram was established for prediction of PFS.

Results

There was a significant association between the radiomics signature (including 9 screened radiomics features) and PFS, which was independent of other clinicopathologic factors in both the training (P < 0.001, multivariable Cox regression) and validation (P = 0.045, multivariable Cox regression) cohorts. Radiogenomic analysis revealed that the radiomics signature was associated with the immune response, programmed cell death, cell proliferation, and vasculature development. A nomogram established using the radiomics signature and clinicopathologic risk factors demonstrated high accuracy and good calibration for prediction of PFS in both the training (C-index, 0.684) and validation (C-index, 0.823) cohorts.

Conclusions

PFS can be predicted non-invasively in patients with LGGs by a group of radiomics features that could reflect the biological processes of these tumors.

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We developed a non-invasive model for the prediction of PFS in patients with lower-grade gliomas.

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We further revealed the biological processes underlying the radiomic signature by using comprehensive radiogenomic analysis.

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PFS of lower-grade gliomas could be predicted effectively based on the radiomics model.

Glycerophosphatidylcholine PC(36:1) absence and 3'-phosphoadenylate (pAp) accumulation are hallmarks of the human glioma metabolome

Glioma is the most prevalent malignant brain tumor. A comprehensive analysis of the glioma metabolome is still lacking. This study aims to explore new special metabolites in glioma tissues. A non-targeted human glioma metabolomics was performed by UPLC-Q-TOF/MS. The gene expressions of 18 enzymes associated with 3’-phosphoadenylate (pAp) metabolism was examined by qRT-PCR. Those enzymes cover the primary metabolic pathway of pAp. We identified 15 new metabolites (13 lipids and 2 nucleotides) that were significantly different between the glioma and control tissues. Glycerophosphatidylcholine [PC(36:1)] content was high and pAp content was significantly low in the control brain (p  < 0.01). In glioma tissues, PC(36:1) was not detected and pAp content was significantly increased. The gene expressions of 3′-nucleotidases (Inositol monophosphatase (IMPAD-1) and 3′(2′),5′-bisphosphate nucleotidase 1(BPNT-1)) were dramatically down-regulated. Meanwhile, the gene expression of 8 sulfotransferases (SULT), 2 phosphoadenosine phosphosulfate synthases (PAPSS-1 and PAPSS-2) and L-aminoadipate-semialdehyde dehydrogenase-phosphopante-theinyl transferase (AASDHPPT) were up-regulated. PC(36:1) absence and pAp accumulation are the most noticeable metabolic aberration in glioma. The dramatic down-regulation of IMPAD-1 and BPNT-1 are the primary cause for pAp dramatic accumulation. Our findings suggest that differential metabolites discovered in glioma could be used as potentially novel therapeutic targets or diagnostic biomarkers and that abnormal metabolism of lipids and nucleotides play roles in the pathogenesis of glioma.

CKAP2 expression is associated with glioma tumor growth and acts as a prognostic factor in high‑grade glioma

Cytoskeletal‑associated protein 2 (CKAP2), which is also known as tumor‑associated microtubule‑associated protein, has been reported to be dysregulated in various types of human cancer. However, the role of CKAP2 in glioma has not been fully elucidated. The present study evaluated the expression pattern of CKAP2 using the Chinese Glioma Genome Atlas microarray database, which included 301 patients, and validated the findings using The Cancer Genome Atlas RNA sequencing database. Kaplan‑Meier survival analysis, and univariate and multivariate Cox analyses, were used to estimate survival distributions. Furthermore, the biological implication of aberrant CKAP2 expression in high‑grade glioma (HGG) was investigated using Gene Ontology analysis, gene set enrichment analysis, gene set variation analysis and STRING. The results indicated that patients with HGG exhibited significantly higher CKAP2 expression levels compared with patients with low‑grade glioma in both databases. Higher expression levels of CKAP2 were significantly associated with shorter overall survival and progression‑free survival of patients with HGG. Furthermore, CKAP2 was also positively correlated with known malignant factors, including high Ki67 expression and phosphatase and tensin homolog mutations. The univariate and multivariate Cox regression analyses demonstrated that CKAP2 may be a novel independent prognostic biomarker for patients with HGG. Functional assays also indicated that CKAP2 was closely associated with the cell cycle, mitosis and cell proliferation. These results suggested that CKAP2 may be associated with tumor growth and could serve as an independent prognostic factor, particularly in patients with HGG.

Blockade of Na/H exchanger stimulates glioma tumor immunogenicity and enhances combinatorial TMZ and anti-PD-1 therapy

The weak immunogenicity of gliomas presents a barrier for effective immunotherapy. Na/H exchanger isoform 1 (NHE1) maintains alkaline intracellular pH (pHi) of glioma cells and acidic microenvironment. In addition, NHE1 is expressed in tumor-associated microglia and tumor-associated macrophages (TAMs) and involved in protumoral communications between glioma and TAMs. Therefore, we hypothesize that NHE1 plays a role in developing tumor resistance and immunosuppressive tumor microenvironment. In this study, we investigated the efficacy of pharmacological inhibition of NHE1 on combinatorial therapies. Here we show that temozolomide (TMZ) treatment stimulates NHE1 protein expression in two intracranial syngeneic mouse glioma models (SB28, GL26). Pharmacological inhibition of NHE1 potentiated the cytotoxic effects of TMZ, leading to reduced tumor growth and increased median survival of mice. Blockade of NHE1 stimulated proinflammatory activation of TAM and increased cytotoxic T cell infiltration into tumors. Combining TMZ, anti-PD-1 antibody treatment with NHE1 blockade significantly prolonged the median survival in the mouse glioma model. These results demonstrate that pharmacological inhibition of NHE1 protein presents a new strategy for potentiating TMZ-induced cytotoxicity and increasing tumor immunogenicity for immunotherapy to improve glioma therapy.

Mesenchymal glioblastoma constitutes a major ceRNA signature in the TGF-β pathway

Rationale: Competitive endogenous RNA (ceRNA) networks play important roles in posttranscriptional regulation. Their dysregulation is common in cancer. However, ceRNA signatures have been poorly examined in the invasive and aggressive phenotypes of mesenchymal glioblastoma (GBM). This study aims to characterize mesenchymal glioblastoma at the mRNA-miRNA level and identify the mRNAs in ceRNA networks (micNET) markers and their mechanisms in tumorigenesis. Methods: The mRNAs in ceRNA networks (micNETs) of glioblastoma were investigated by constructing a GBM ceRNA network followed by integration with a STRING protein interaction network. The prognostic micNET markers of mesenchymal GBM were identified and validated across multiple datasets. ceRNA interactions were identified between micNETs and miR181 family members. LY2109761, an inhibitor of TGFBR2, demonstrated tumor-suppressive effects on both primary cultured cells and a patient-derived xenograft intracranial model. Results: We characterized mesenchymal glioblastoma at the mRNA-miRNA level and reported a ceRNA network that could separate the mesenchymal subtype from other subtypes. Six genes (TGFBR2, RUNX1, PPARG, ACSL1, GIT2 and RAP1B) that interacted with each other in both a ceRNA-related manner and in terms of their protein functions were identified as markers of the mesenchymal subtype. The coding sequence (CDS) and 3'-untranslated region (UTR) of TGFBR2 upregulated the expression of these genes, whereas TGFBR2 inhibition by siRNA or miR-181a/d suppressed their expression levels. Furthermore, mesenchymal subtype-related genes and the invasion phenotype could be reversed by suppressing the six mesenchymal marker genes. Conclusions: This study suggests that the micNETs may have translational significance in the diagnosis of mesenchymal GBM and may be novel therapeutic targets.

Genetic and clinical characterization of B7-H3 (CD276) expression and epigenetic regulation in diffuse brain glioma

Gliomas are the most common malignant tumors of the brain. Immune checkpoints have been increasingly emphasized as targets for treating malignant tumors. B7-H3 has been identified as an immune checkpoint that shows potential value for targeting therapies. We set out to characterize the expression pattern and biological function of B7-H3 in brain gliomas using high-throughput data obtained from the Chinese Glioma Genome Atlas (CGGA) and the Cancer Genome Atlas (TCGA) projects. B7-H3 was upregulated more in higher-grade gliomas than that in lower-grade gliomas in both CGGA and TCGA datasets. Isocitrate dehydrogenase (IDH) mutation seemed to exert significant influence on B7-H3 expression in gliomas but led to quite different results between grade II gliomas and higher-grade gliomas. In addition to IDH, methylation of B7-H3 promoter and microRNA-29 family also showed a potential regulatory effect on B7-H3 expression. Gene ontology analysis revealed that B7-H3 was associated with mitotic cell cycle, cell proliferation and immune response. Further investigation suggested that B7-H3 was mostly involved in the Toll-like receptor signaling pathway. Survival analysis indicated that B7-H3 was an independent unfavorable prognosticator for glioma patients in both CGGA and TCGA datasets. B7-H3 expression is regulated by multiple mechanisms and is potentially involved in the T-cell receptor signaling pathway. Higher B7-H3 expression indicates a worse prognosis for glioma patients, which warrants further research into the development of inhibitors for targeting this immune checkpoint, but we still need to be cautious about immune checkpoint inhibition for central nervous system tumors.

Apatinib suppresses cell growth and metastasis and promotes antitumor activity of temozolomide in glioma

Apatinib, a small-molecule multi-targeted tyrosine kinase inhibitor, is widely used to treat various types of solid tumors. In the present study, it was investigated whether apatinib has therapeutic potential for glioma. Cell Counting Kit-8 and colony formation assays were utilized to determine the cell viability of p53- and EGFR-mutated U251MG glioma cells, and wild-type U-87MG ATCC glioma cells. Furthermore, apoptosis, and the invasion and migration abilities of glioma cells were investigated by flow cytometry, invasion assays and wound-healing assays. The potential of the combination of apatinib with temozolomide (TMZ) for glioma therapy was also investigated. The results demonstrate that apatinib significantly inhibited cell proliferation and colony formation through promoting cell apoptosis in p53- and EGFR-mutated and wild-type glioma cells. Cell invasion and migration abilities were notably decreased following treatment with apatinib. Overall, the present study indicates a synergistic antitumor effect of apatinib and TMZ in glioma, and presents a basis for the use of apatinib in glioma treatment.

CMTM6 overexpression is associated with molecular and clinical characteristics of malignancy and predicts poor prognosis in gliomas

CMTM6, a previously uncharacterized protein, was identified as a critical regulator of PD-L1, which is reported as an immune checkpoint inhibitor, to modulate the T cell activities both in vitro and in vivo of other tumors. However, the role of CMTM6 has so far remained unclear in glioma. To investigate the role of CMTM6 in gliomas, we analyzed the transcriptome level, genomic profiles and its relationship with clinical practice. 1862 glioma samples with transcriptome data were enrolled in this study, including CGGA RNA-seq, TCGA RNA-seq, CGGA-microarray, GSE16011 and IVY GBM databases. Clinical information and genomic profiles containing somatic mutations and DNA copy numbers were also obtained. We found that CMTM6 expression was highly correlated with major clinical and molecular characteristics. Cases with high CMTM6 expression were more likely to be predicted as malignant entities and frequent with genomic aberrations of driver oncogenes. Moreover, gene ontology analysis based on significantly correlated genes of CMTM6 expression exhibited that CMTM6 was associated with immune responses and inflammatory activities. CMTM6 was synthetic with other immune checkpoint inhibitors. Additionally, CMTM6 was involved in immune functions via modulating T-lymphocyte-mediated anti-tumor immunity. Finally, high CMTM6 expression was associated with reduced survival time and may serve as a strong indicator of poor prognosis in gliomas. In brief, High level of CMTM6 expression is closely related to high malignant gliomas. Meanwhile, CMTM6 plays an important role in regulating T cell activation and antitumor responses. Therefore, CMTM6 is a promising target for developing immunotherapy of gliomas.

Combinations of four or more CpGs methylation present equivalent predictive value for MGMT expression and temozolomide therapeutic prognosis in gliomas

AIMS

The pyrosequencing (PSQ) has been regarded as the gold standard for MGMT promoter methylation testing in gliomas. However, various CpG combinations are currently used in clinical practice. We aimed to clarify how and how many CpGs combined is robust enough to predict MGMT mRNA expression and therapeutic prognosis of patients.

METHODS

Total 223 patients with WHO III/IV gliomas were enrolled from Chinese Glioma Genome Atlas, including two independent cohorts, the eight-site cohort (with CpGs 75-82 tested) and the seven-site cohort (with CpGs 72-78 tested). Spearman's correlation and ROC curves were employed to investigate the value of different CpG combinations on predicting MGMT mRNA expression. The ROC curves and Kaplan-Meier steps were performed to compare the TMZ therapeutic prognostic values of different CpG combinations.

RESULTS

The methylation level of all individual CpG and CpG combinations for the eleven CpGs (CpGs 72-82), significantly correlated to MGMT mRNA expression (Spearman, all P < 0.0001), could effectively predict the mRNA expression (AUC, 0.86-0.91 in the eight-site cohort, 0.83-0.90 in the seven-site cohort). Moreover, the correlation coefficients and the predictive values presented equivalent when four or more CpGs combinedly used (AUC, 0.88-0.90 in the eight-site cohort, 0.87-0.88 in the seven-site cohort). Finally, similar results were also observed when using selected CpG combinations to predict therapeutic prognosis of patients.

CONCLUSIONS

Four-CpG combinations of pyrosequencing are sufficient for evaluating the methylation status of MGMT and predicting therapeutic prognosis in gliomas.

Molecular profiles of tumor contrast enhancement: A radiogenomic analysis in anaplastic gliomas

The presence of contrast enhancement (CE) on magnetic resonance (MR) imaging is conventionally regarded as an indicator for tumor malignancy. However, the biological behaviors and molecular mechanism of enhanced tumor are not well illustrated. The aim of this study was to investigate the molecular profiles associated with anaplastic gliomas (AGs) presenting CE on postcontrast T1‐weighted MR imaging. In this retrospective database study, RNA sequencing and MR imaging data of 91 AGs from the Cancer Genome Atlas (TCGA) and 64 from the Chinese Glioma Genome Atlas (CGGA) were collected. Gene set enrichment analysis (GSEA), significant analysis of microarray, generalized linear models, and Least absolute shrinkage and selection operator algorithm were used to explore radiogenomic and prognostic signatures of AG patients. GSEA indicated that angiogenesis and epithelial‐mesenchymal transition were significantly associated with post‐CE. Genes driving immune system response, cell proliferation, and focal adhesions were also significantly enriched. Gene ontology of 237 differential genes indicated consistent results. A 48‐gene signature for CE was identified in TCGA and validated in CGGA dataset (area under the curve = 0.9787). Furthermore, seven genes derived from the CE‐specific signature could stratify AG patients into two subgroups based on overall survival time according to corresponding risk score. Comprehensive analysis of post‐CE and genomic characteristics leads to a better understanding of radiology‐pathology correlations. Our gene signature helps interpret the occurrence of radiological traits and predict clinical outcomes. Additionally, we found nine prognostic quantitative radiomic features of CE and investigated the underlying biological processes of them.

Clinical Long-Term Follow-Up Evaluation of Functional Neuronavigation in Adult Cerebral Gliomas

OBJECTIVE

To assess the application of functional neuronavigation in surgeries of adult cerebral gliomas.

METHODS

We performed a retrospective analysis of 375 cases of adult cerebral glioma patients who underwent microsurgical treatment between 2011 and 2017 in our department. Among them, 142 patients underwent surgery using functional neuronavigation (group A), and the other 233 patients were operated on without the help of functional neuronavigation (group B). For both groups, we categorized them into several subgroups according to the lesion locations.

RESULTS

A significant difference in the gross total resection rate was observed between group A and group B (P = 0.001 for overall; P = 0.036 for EO area; and P = 0.004 for BBT area). The postoperative complication rate of group A was much lower than that of group B (P = 0.003 for overall; and P = 0.016 for BBT area). The postoperative 6-month Karnofsky Performance Scale score of all patients in group A was significantly higher than that of group B. Kaplan-Meier survival analyses showed significant increases in the median survival time of group A compared with that of group B (P < 0.001 for overall; P = 0.012 for EO area; P = 0.006 for BBT area), and the Cox proportional regression analysis estimated the hazard ratio of the functional neuronavigation to be 0.533, helping reduce the risk of death by 46.7%.

CONCLUSIONS

This study confirmed that the application of neuronavigation in adult glioma surgery can improve postoperative quality of life and lengthen the survival time of patients, especially in cases involving the brainstem and the eloquent area.

The TERT promoter mutation status and MGMT promoter methylation status, combined with dichotomized MRI-derived and clinical features, predict adult primary glioblastoma survival

Purpose

This study aimed to integrate the TERT promoter mutation status, MGMT promoter methylation status, MRI‐derived features, and clinical features into a survival analysis model to better understand adult primary glioblastoma prognosis‐related markers.

Method

A total of 304 adult glioblastoma samples collected after surgical resection were selected for retrospective analysis, and Sanger sequencing was performed to detect IDH and TERT promoter mutations. The methylation of the MGMT promoter was analyzed by pyrosequencing, and MRI‐derived and clinical features were dichotomized into easily acquired variables. Random survival forest analysis, Kaplan‐Meier analysis, Cox proportional hazard regression, and LASSO regression were performed for the survival analysis, and ROC analysis and Pearson's chi‐squared test were employed for the correlation analysis.

Results

Wild‐type IDH was present in 89.8% of the adult glioblastoma samples, and TERT promoter mutations and MGMT promoter methylation were observed in 66.42% and 38.49% of all adult primary glioblastomas, respectively. Age and MGMT promoter methylation were identified as independent prognostic biomarkers, and the TERT promoter mutation status and MGMT promoter methylation status, when combined with other tumor‐related factors, generated several different survival subgroups. None of the factors investigated in this study predicted the MGMT promoter status, and MRI‐detected necrosis was positively associated with TERT promoter mutations.

Conclusion

MGMT promoter methylation and TERT promoter mutations, combined with MRI‐derived and clinical features, revealed different survival subgroups with distinct responses to current treatments, and this information increases the ability to predict the survival of adult primary glioblastoma patients. MRI‐detected necrosis often indicates the presence of TERT promoter mutations.

Imaging biomarkers guided anti-angiogenic therapy for malignant gliomas

Antiangiogenic therapy is a universal approach to the treatment of malignant gliomas but fails to prolong the overall survival of newly diagnosed or recurrent glioblastoma patients. Imaging biomarkers are quantitative imaging parameters capable of objectively describing biological processes, pathological changes and treatment responses in some situations and have been utilized for outcome predictions of malignant gliomas in anti-angiogenic therapy. Advanced magnetic resonance imaging techniques (including perfusion-weighted imaging and diffusion-weighted imaging), positron emission computed tomography and magnetic resonance spectroscopy are imaging techniques that can be used to acquire imaging biomarkers, including the relative cerebral blood volume (rCBV), K^trans, and the apparent diffusion coefficient (ADC). Imaging indicators for a better prognosis when treating malignant gliomas with antiangiogenic therapy include the following: a lower pre- or post-treatment rCBV, less change in rCBV during treatment, a lower pre-treatment K^trans, a higher vascular normalization index during treatment, less change in arterio-venous overlap during treatment, lower pre-treatment ADC values for the lower peak, smaller ADC volume changes during treatment, and metabolic changes in glucose and phenylalanine. The investigation and utilization of these imaging markers may confront challenges, but may also promote further development of anti-angiogenic therapy. Despite considerable evidence, future prospective studies are critically needed to consolidate the current data and identify novel biomarkers.

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Anti-angiogenic therapy only benefits specific populations of glioma patients.

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Advanced imaging techniques can produce quantitative imaging biomarkers.

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Physiological and metabolic parameter can predict outcome for anti-angiogenic therapy.

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Larger prospective studies are needed to provide further evidence.

ARL2 overexpression inhibits glioma proliferation and tumorigenicity via down-regulating AXL

BACKGROUND

Glioma is the most common primary brain tumor in adults with a poor prognosis. As a member of ARF subfamily GTPase, ARL2 plays a key role in regulating the dynamics of microtubules and mitochondrial functions. Recently, ARL2 has been identified as a prognostic and therapeutic target in a variety range of malignant tumors. However, the biological functional role of ARL2 in glioma still remains unknown. The aim of this study was to explore the expression and functional role of ARL2 in glioma.

METHODS

In this study, we investigated the expression of ARL2 in glioma samples by using RT-PCR, immunohistochemistry and western blot. The correlation between ARL2 expression and the outcomes of glioma patients was evaluated with survival data from TCGA, CGGA and Rembrandt dataset. Lentiviral technique was used for ARL2 overexpression in U87 and U251 cells. CCK8 assay, colony formation assay, wound healing test, transwell invasion assay and in vivo subcutaneous xenograft model were performed to investigated the biological functions of ARL2.

RESULTS

ARL2 expression was down-regulated in glioma, and was inversely associated with poor prognosis in glioma patients. Furthermore, exogenous ARL2 overexpression attenuated the growth and colony-formation abilities of glioma cells, as well as their migration and invasive capabilities. Moreover, elevated expression of ARL2 inhibited in vivo tumorigenicity of glioma cells. Mechanistically, ARL2 regulated AXL expression, which was known as an important functional regulator of proliferation and tumorigenicity in glioma cells.

CONCLUSION

Our study suggests that ARL2 inhibits the proliferation, migration and tumorigenicity of glioma cells by regulating the expression of AXL and may conduct as a new prognostic and therapeutic target for glioma.

Overexpression of Fn14 in gliomas: tumor progression and poor prognosis

AIM

To confirm whether the expression level of Fn14 could affect progression or prognosis of glioma patients.

METHODS

Glioma cohorts in The Cancer Genome Atlas, Gene Expression Omnibus and Chinese Glioma Genome Atlas databases were comprehensively analyzed.

RESULTS

Low-grade patients had lower expression level of Fn14, while patients with higher expression of Fn14 tended to harbor shorter overall survival and disease-free survival. The expression level of Fn14 was downregulated by IDH1/IDH2 mutations while its gene body methylation was upregulated. After adjusting age, the expression level of Fn14 was still significantly associated with overall survival and disease-free survival in low-grade gliomas. In a cell line data analysis, Fn14 expression was positively correlated with temozolomide dosage.

CONCLUSION

Fn14 was an independent predictive biomarker for the progression and prognosis in low-grade gliomas.

Stratification according to recursive partitioning analysis predicts outcome in newly diagnosed glioblastomas

Glioblastoma accounts for more than half of diffuse gliomas. The prognosis of patients with glioblastoma remains poor despite comprehensive and intensive treatments. Furthermore, the clinical significance of molecular parameters and routinely available clinical variables for the prognosis prediction of glioblastomas remains limited. The authors describe a novel model may help in prognosis prediction and clinical management of glioblastoma patients. We performed a recursive partitioning analysis to generate three independent prognostic classes of 103 glioblastomas patients from TCGA dataset. Class I (MGMT promoter methylated, age <58), class II (MGMT promoter methylation, age ≥58; MGMT promoter unmethylation, age <54, KPS ≥70; MGMT promoter unmethylation, age >59, KPS ≥70), class III (MGMT promoter unmethylation, age 54-58, KPS ≥70; MGMT promoter unmethylation, KPS <70). Age, KPS and MGMT promoter methylation were the most significant prognostic factors for overall survival. The results were validated in CGGA dataset.

This was the first study to combine various molecular parameters and clinical factors into recursive partitioning analysis to predict the prognosis of patients with glioblastomas. We included MGMT promoter methylation in our study, which could give better suggestion to patients for their chemotherapy. This clinical study will serve as the backbone for the future incorporation of molecular prognostic markers currently in development. Thus, our recursive partitioning analysis model for glioblastomas may aid in clinical prognosis evaluation.

Classifying lower grade glioma cases according to whole genome gene expression

OBJECTIVE

To identify a gene-based signature as a novel prognostic model in lower grade gliomas.

RESULTS

A gene signature developed from HOXA7, SLC2A4RG and MN1 could segregate patients into low and high risk score groups with different overall survival (OS), and was validated in TCGA RNA-seq and GSE16011 mRNA array datasets. Receiver operating characteristic (ROC) was performed to show that the three-gene signature was more sensitive and specific than histology, grade, age, IDH1 mutation and 1p/19q co-deletion. Gene Set Enrichment Analysis (GSEA) and GO analysis showed high-risk samples were associated with tumor associated macrophages (TAMs) and highly invasive phenotypes. Moreover, HOXA7-siRNA inhibited migration and invasion in vitro, and downregulated MMP9 at the protein level in U251 glioma cells.

METHODS

A cohort of 164 glioma specimens from the Chinese Glioma Genome Atlas (CGGA) array database were assessed as the training group. TCGA RNA-seq and GSE16011 mRNA array datasets were used for validation. Regression analyses and linear risk score assessment were performed for the identification of the three-gene signature comprising HOXA7, SLC2A4RG and MN1.

CONCLUSIONS

We established a three-gene signature for lower grade gliomas, which could independently predict overall survival (OS) of lower grade glioma patients with higher sensitivity and specificity compared with other clinical characteristics. These findings indicate that the three-gene signature is a new prognostic model that could provide improved OS prediction and accurate therapies for lower grade glioma patients.

CDH2 expression is of prognostic significance in glioma and predicts the efficacy of temozolomide therapy in patients with glioblastoma

Glioma is the most common and malignant primary brain cancer in adults. Radical surgical excision accompanied by radiotherapy and chemotherapy is the prevailing standard therapy for patients with glioblastoma (GBM). Cadherin 2 (CDH2) encodes the N-cadherin protein, a classical cadherin and a member of the cadherin superfamily, which sustains the integrity of the cell and is involved in several cell signal transduction pathways. In the present study, the association between CDH2 expression and clinical features was investigated based on the Chinese Glioma Genome Atlas (CGGA), the Rembrandt datasets and The Cancer Genome Atlas datasets (TCGA). Medical statistical methods, including Kaplan-Meier analysis and Cox regression model were used. The expression of CDH2 was identified to be strongly associated with glioma World Health Organization grade in the CGGA and Rembrandt datasets. Patients with low CDH2 expression had an improved prognosis and benefited from temozolomide therapy. In conclusion, these findings revealed that CDH2 may serve as a prognostic and predictive molecular biomarker for the grading and treatment of glioma.

FGFR3, as a receptor tyrosine kinase, is associated with differentiated biological functions and improved survival of glioma patients

Background

Activation of receptor tyrosine kinases is common in Malignancies. FGFR3 fusion with TACC3 has been reported to have transforming effects in primary glioblastoma and display oncogenic activity in vitro and in vivo. We set out to investigate the role of FGFR3 in glioma through transcriptomic analysis.

Results

FGFR3 increased in Classical subtype and Neural subtype consistently in CGGA and TCGA cohort. Similar patterns of FGFR3 distribution through subtypes were observed in CGGA and TCGA samples. Gene ontology analysis was performed with genes that were significantly correlated with FGFR3 expression. We found that positively associated biological processes of FGFR3 were focused on differentiated cellular functions and neuronal activities, while negatively correlated biological processes focused on mitosis and cell cycle phase. Clinical investigation showed that higher FGFR3 expression predicted improved survival for glioma patients, especially in Proneural subtype. Moreover, FGFR3 showed very limited relevance with other receptor tyrosine kinases in glioma at transcriptome level.

Materials and Methods

FGFR3 expression data of glioma was obtained from Chinese Glioma Genome Atlas (CGGA) and TCGA (The Cancer Genome Atlas). In total, RNA sequencing data of 325 glioma samples and mRNA microarray data of 301 samples from CGGA dataset were enrolled into this study. To consolidate the findings that we have revealed in CGGA dataset, RNA-seq data of 672 glioma samples from TCGA dataset were used as a validation cohort. R language was used as the main tool to perform statistical analysis and graphical work.

Conclusions

FGFR3 expression increased in classical and neural subtypes and was associated with differentiated cellular functions. FGFR3 showed very limited correlation with other common receptor tyrosine kinases, and predicted improved survival for glioma patients.

Structural and advanced imaging in predicting MGMT promoter methylation of primary glioblastoma: a region of interest based analysis

Background

The methylation status of oxygen 6-methylguanine-DNA methyltransferase (MGMT) promoter has been associated with treatment response in glioblastoma(GBM). Using pre-operative MRI techniques to predict MGMT promoter methylation status remains inconclusive. In this study, we investigated the value of features from structural and advanced imagings in predicting the methylation of MGMT promoter in primary glioblastoma patients.

Methods

Ninety-two pathologically confirmed primary glioblastoma patients underwent preoperative structural MR imagings and the efficacy of structural image features were qualitatively analyzed using Fisher’s exact test. In addition, 77 of the 92 patients underwent additional advanced MRI scans including diffusion-weighted (DWI) and 3-diminsional pseudo-continuous arterial spin labeling (3D pCASL) imaging. Apparent diffusion coefficient (ADC) and relative cerebral blood flow (rCBF) values within the manually drawn region-of-interest (ROI) were calculated and compared using independent sample t test for their efficacies in predicting MGMT promoter methylation. Receiver operating characteristic curve (ROC) analysis was used to investigate the predicting efficacy with the area under the curve (AUC) and cross validations. Multiple-variable logistic regression model was employed to evaluate the predicting performance of multiple variables.

Results

MGMT promoter methylation was associated with tumor location and necrosis (P <  0.05). Significantly increased ADC value (P <  0.001) and decreased rCBF (P <  0.001) were associated with MGMT promoter methylation in primary glioblastoma. The ADC achieved the better predicting efficacy than rCBF (ADC: AUC, 0.860; sensitivity, 81.1%; specificity, 82.5%; vs rCBF: AUC, 0.835; sensitivity, 75.0%; specificity, 78.4%; P = 0.032). The combination of tumor location, necrosis, ADC and rCBF resulted in the highest AUC of 0.914.

Conclusion

ADC and rCBF are promising imaging biomarkers in clinical routine to predict the MGMT promoter methylation in primary glioblastoma patients.

Radiation combined with temozolomide contraindicated for young adults diagnosed with anaplastic glioma

Purpose

Age is a major prognostic factor for malignant gliomas. However, few studies have investigated the management of gliomas in young adults. We determined the role of survival and treatment in young adults with advanced gliomas in a large population from the Chinese Glioma Genome Atlas (CGGA).

Methods

This study included 726 adults (age ≥ 18) with histologically proven anaplastic glioma or glioblastoma multiforme (GBM). The overall and progression-free survival was determined in young (age < 50) and older groups (age ≥ 50).

Results

The study included an older group (OP) of 264 patients and a younger group (YP) of 462patients. In the OP group with GBM and anaplastic glioma, patients treated with RT combined with temozolomide (TMZ) manifested significantly longer OS and PFS compared with patients assigned to RT alone (P < 0.05). In contrast, the YP group diagnosed with anaplastic glioma failed to show any survival advantage with RT plus TMZ compared with RT alone.

Conclusions

We observed no survival benefit in young adults (age < 50) with anaplastic glioma when treated with TMZ combined with RT. Our findings warrant further investigation of younger patients diagnosed with anaplastic glioma treated with radiotherapy plus TMZ chemotherapy.

BmK CT enhances the sensitivity of temozolomide-induced apoptosis of malignant glioma U251 cells in vitro through blocking the AKT signaling pathway

Temozolomide (TMZ) is a drug that has been demonstrated to improve the survival time of patients with glioblastoma multiforme (GBM) when administered with concomitant radiotherapy. However, chemoresistance is one of the major obstacles in the treatment of GBM. In the present study, an MTT assay and flow cytometry were used to demonstrate that chlorotoxin-like toxin in the venom of the scorpion Buthus martensii Kirsch (BmK CT) markedly inhibited cell proliferation and induced apoptosis in U251 cells when combined with TMZ. In combination with TMZ, BmK CT exhibited a significant and synergistic anti-tumor effect by inhibiting protein kinase B (AKT) independently and triggering the apoptosis signaling cascade in vitro. Furthermore, BmK CT increased the expression of phosphatase and tensin homolog at the transcriptional level, which is a key negative regulator of the AKT signaling pathway. The results of the present study demonstrated that BmK CT enhanced the sensitivity of TMZ-induced U251 cell apoptosis through the downregulation of phosphorylated AKT levels, suggesting that BmK CT and TMZ combination therapy may be a novel approach for glioma therapy.

Immune heterogeneity and clinicopathologic characterization of IGFBP2 in 2447 glioma samples

Glioblastoma is an immunosuppressive, deadly brain tumor. IGFBP2, a circulating biomarker for cancer diagnosis and a potential immunotherapeutic target, is attracting more and more attention from oncologists and clinicians. Thus, it is urgent to thoroughly investigate the immune biological process of IGFBP2 to understand tumor immune complexity and provide potential evidence for anti-IGFBP2 therapy. Through authoritative public databases, we enrolled a total of 2447 glioma samples with gene expression profiles. Then, the clinical characteristics and immunosuppressive status of IGFBP2 in the glioma samples were analyzed. Immunohistochemical staining detected the expression of immunosuppressive biomarkers. We found that IGFBP2 expression was upregulated in high-grade glioma and GBM and downregulated in IDH mutant glioma. Increased IGFBP2 accompanied PTEN loss and EGFR amplification. Bioinformatic analysis revealed that IGFBP2 is related to immunological processes. We further selected specific immunologic related gene sets and found IGFBP2 predominated immunosuppressive activities in GBM. Furthermore, we explored the relationship between IGFBP2 and genes that were well-characterized glioma-mediated immunosuppressive molecules to investigate the potential effect of IGFBP2. We discovered that IGFBP2 was correlated with CHI3L1, TNFRSF1A, LGALS1, TIMP1, VEGFA, ANXA1 and LGALS3, which were classic immunosuppressive biomarkers. Higher IGFBP2 expression predicted unfavorable survival for patients with GBM. Our findings implied that IGFBP2 is involved in immunosuppressive activities and is an independent unfavorable prognostic biomarker for patients with GBM. IGFBP2 is a potential immunotherapeutic target for GBM in future clinical trials.

Vaccination in the immunotherapy of glioblastoma

Glioblastoma remains one of the most common central nervous system tumors with an extremely poor prognosis. Recently, rapid progress in immunotherapy has provided new options for the treatment of glioblastoma. Vaccination, the primary method of immunotherapy, stimulates the body's tumor-specific immune response by the injection of foreign antigens. Peptide vaccines involve the injection of tumor-specific antigens, such as EGFRvIII or heat-shock proteins. Cell-based vaccines, which primarily include dendritic cell vaccines and tumor cell vaccines, involve injections of ex vivo-modified cells. Despite the encouraging results of phase I/II clinical trials, no successful phase III clinical trials involving glioblastoma immunotherapy, including glioblastoma vaccinations, have been reported to date. In this review, the authors summarize the published outcomes of glioblastoma vaccine therapy, explore its future prospects based on ongoing clinical trials, and discuss combined therapy as a future direction for glioblastoma treatment.

Loss of ATRX suppresses ATM dependent DNA damage repair by modulating H3K9me3 to enhance temozolomide sensitivity in glioma

Mutations in ATRX constitute the most prevalent genetic abnormalities in gliomas. The presence of ATRX mutations in glioma serves as a marker of better prognosis with longer patient survival although the underlying mechanisms are poorly understood. In the present study, we found that ATRX biological function was significantly involved in DNA replication and repair. CRISPR/Cas9-mediated genetic inactivation of ATRX induced inhibition of cell proliferation, invasion and vasculogenic mimicry. In addition, temozolomide (TMZ) treatment induced greater DNA damage and apoptotic changes in ATRX knockout glioma cells. Moreover, we confirmed that ATRX knockout resulted in a failure to trigger ATM phosphorylation and finally restrained the activation of downstream proteins of the ATM pathway. The ATM-associated DNA repair pathway was extensively compromised in ATRX knockout cells owing to decreased histone H3K9me3 availability. Public databases also showed that patients with low ATRX expression exhibited preferable overall survival and profited more from TMZ treatment. These data suggest that ATRX is involved in DNA damage repair by regulating the ATM pathway and might serve as a prognostic maker in predicting TMZ chemosensitivity.

Reactive Astrocytes in Glioblastoma Multiforme

Despite the multidisciplinary integration in the therapeutic management of glioblastoma multiforme (GBM), the prognosis of GBM patients is poor. There is growing recognition that the cells in the tumor microenvironment play a vital role in regulating the progression of glioma. Astrocytes are an important component of the blood-brain barrier (BBB) as well as the tripartite synapse neural network to promote bidirectional communication with neurons under physiological conditions. Emerging evidence shows that tumor-associated reactive astrocytes interact with glioma cells and facilitate the progression, aggression, and survival of tumors by releasing different cytokines. Communication between reactive astrocytes and glioma cells is further promoted through ion channels and ion transporters, which augment the migratory capacity and invasiveness of tumor cells by modifying H⁺ and Ca²⁺ concentrations and stimulating volume changes in the cell. This in part contributes to the loss of epithelial polarization, initiating epithelial-mesenchymal transition. Therefore, this review will summarize the recent findings on the role of reactive astrocytes in the progression of GBM and in the development of treatment-resistant glioma. In addition, the involvement of ion channels and transporters in bridging the interactions between tumor cells and astrocytes and their potential as new therapeutic anti-tumor targets will be discussed.

A novel gene signature based on five glioblastoma stem-like cell relevant genes predicts the survival of primary glioblastoma

PURPOSE

Primary glioblastoma (pGBM) is the most common and lethal type of neoplasms in the central nervous system, while the existing biomarkers, lacking consideration on the stemness changes of GBM cells, are not specific enough to predict the complex prognosis respectively. We aimed to build a high-efficiency prediction gene signature related to GBM cell stemness and investigate its prognostic value in primary glioblastoma.

METHODS

Differentially expressed genes were screened in GSE23806 database. The selected genes were then verified by univariate Cox regression in 591 patients from four enormous independent databases, including the Chinese Glioma Genome Atlas (CGGA), TCGA, REMBRANDT and GSE16011. Finally, the intersected genes were included to build the gene signature. GO analysis and GSEA were carried out to explore the bioinformatic implication.

RESULTS

The novel five-gene signature was used to identify high- and low-risk groups in the four databases, and the high-risk group showed notably poorer prognosis (P < 0.05). Gene ontology (GO) terms including "immune response", "apoptotic process", and "angiogenesis" were picked out by GO analysis and GSEA, which revealed that the gene signature was highly possibly related to the stemness of GSCs and predicting the prognosis of GBM effectively.

CONCLUSION

We built a gene signature with five glioblastoma stem-like cell (GSC) relevant genes, and predicted the survival in four independent databases effectively, which is possibly related to the stemness of GSCs in pGBM. Several GO terms were investigated to be correlated to the signature. The signature can predict the prognosis of glioblastoma efficiently.

Monitoring autophagic flux using p62/SQSTM1 based luciferase reporters in glioma cells

Autophagy is a highly dynamic process characterized with the term of autophagic flux. In the present study, we developed a quantifiable luciferase reporter system to measure the capacity as well as the dynamics of autophagic flux. Briefly, a luciferase variant of Luc2p was fused with p62/SQSTM1 or its UBA domain deletion mutant (p62ΔU) and transfected into cells. The expressed Luc2p-p62 fusion protein was primarily degraded via autophagy, while Luc2p-p62ΔU was employed as a normalization control due to its resistance to autophagic degradation. The luciferase activity of the lysates from two parallel populations of glioma cells expressing either Luc2p-p62 or Luc2p-p62ΔU was determined and the ratio of Luc2p-p62ΔU/Luc2p-p62 was used to assay the autophagic flux. By this approach, the induction of autophagy was manifested as an increased Luc2p-p62ΔU/Luc2p-p62 ratio, which could be neutralized by autophagy inhibitors or knockdown of ATG5. The performance of our autophagic flux detection system was comparable to a recently reported GFP-LC3-RFP-LC3ΔG probe. We tested the system in TMZ treated glioma cells, and found that coadministration of chloroquine to attenuate cellular autophagic flux significantly improved the TMZ efficacy by triggering more early apoptosis. Collectively, our luciferase-based autophagic flux assay may serve as a useful alternative yet sensitive method for autophagic flux detection in tumor cells.

Research of differential expression of sIL1RAP in low-grade gliomas between children and adults

Glioma is the most common intracranial malignant tumor. Low-grade gliomas (LGG) occupy almost 80% in all of the gliomas. The prognosis of LGG in children is much better than in adult, however, the molecular mechanism is still unclear. In our investigation, it was first found that the level of soluble IL1RAP (sIL1RAP) was significantly higher in the LGG from children than that from adult. We also revealed that sIL1RAP could induce the apoptosis of U251. In cells with overexpression of sIL-1RAP, the cell proliferation promoted by IL-1 was significantly inhibited. These decreased tumor growth ability and better prognosis of low-grade gliomas in children patients than that in adult patients. The expression level of sIL1RAP may become one of the potential indexes for determining the prognosis of low-grade gliomas.

TAGLN2 is a candidate prognostic biomarker promoting tumorigenesis in human gliomas

Background

Transgelin-2 (TAGLN2) is a member of the calponin family of actin-bundling proteins that is involved in the regulation of cell morphology, motility, and cell transformation. Here, the clinical significance and potential function of TAGLN2 in malignant gliomas were investigated.

Methods

Molecular and clinical data was obtained from The Cancer Genome Atlas (TCGA) database. Gene ontology and pathway analysis was used to predict potential functions of TAGLN2. RNA knockdown was performed using siRNA or lentiviral contructs in U87MG and U251 glioma cell lines. Cells were characterized in vitro or implanted in vivo to generate orthotopic xenografts in order to assess molecular status, cell proliferation/survival, and invasion by Western blotting, flow cytometry, and 3D tumor spheroid invasion assay, respectively.

Results

Increased TAGLN2 expression was associated with increasing tumor grade (P < 0.001), the mesenchymal molecular glioma subtype and worse prognosis in patients (P < 0.001). Immunohistochemistry performed with anti-TAGLN2 on an independent cohort of patients (n = 46) confirmed these results. Gene silencing of TAGLN2 in U87MG and U251 significantly inhibited invasion and tumor growth in vitro and in vivo. Western blot analysis revealed that epithelial-mesenchymal transition (EMT) molecular markers, such as N-cadherin, E-cadherin, and Snail, were regulated in a manner corresponding to suppression of the EMT phenotype in knockdown experiments. Finally, TAGLN2 was induced ~ 2 to 3-fold in U87MG and U251 cells by TGFβ2, which was also elevated in GBM and highly correlated with TAGLN2 mRNA levels (P < 0.001).

Conclusions

Our findings indicate that TAGLN2 exerts a role in promoting the development of human glioma. The regulation and function of TAGLN2 therefore renders it as a candidate molecular target for the treatment of GBM.

Electronic supplementary material

The online version of this article (10.1186/s13046-017-0619-9) contains supplementary material, which is available to authorized users.

Complex role of connexin 43 in astrocytic tumors and possible promotion of glioma‑associated epileptic discharge (Review)

Connexin (Cx)43 is a multifunction protein which forms gap junction channels and hemi‑channels. It also contains abundant binding domains which possess the ability to interact with certain Cx43‑associated proteins and therefore serve a fundamental role in various physiological and pathological functions. However, the understanding of the association between cancer and Cx43 along with Cx43‑gap junctions (GJ) remains unclear. All available data illustrate that Cx43 and its associated GJ serve important functions in cancers. The expression levels of Cx43 demonstrate a downward trend and an increase in the levels of malignancy, particularly in astrocytomas. The GJ intercellular communication activity in glioma cells can be adjusted via Cx43 phosphorylation and through the combination of Cx43 and its associated protein. Available evidence reveals Cx43 as a tumor‑inhibiting factor that suppresses glioma growth and proliferation. However, its mechanism is also regarded as complicated and ambiguous. Furthermore, it is apparent that Cx43‑GJ and the carboxyl tail may contribute to glioma growth and proliferation too. However, this valuable role could be weakened by its effects on migration and invasiveness. The detailed mechanism remains unclear and full of controversies. Cx43 can enhance the motor ability and invasiveness of astrocytic glioma cells. It is also able to influence glioma cells to detach from the tumor core to the peritumoral neocortex. This peritumoral region has recently been regarded as the basic focus of glioma‑associated seizure. Thus, Cx43 may take part in the onset and development of glioma‑associated epileptic discharge. In addition, change and increase of Cx43 expression in GJs has been observed in seizure perilesional tissue, which is associated with brain tumors. Cx43 or GJ/hemi‑channels exert enduring effects in the promotion of glioma‑associated epileptic release through direct mass effects and change of the tumor microenvironment. However, there are still a number of issues concerning this aspect that require further exploration. Cx43, as a potential treatment target against this incurable disease and its common symptom of epilepsy, requires further investigation.