Neuro-oncology in 2013: improving outcome in newly diagnosed malignant glioma

Origin recognition complex 6 overexpression promotes growth of glioma cells

The discovery of novel oncotargets for glioma is of immense significance. We here explored the expression patterns, biological functions, and underlying mechanisms associated with ORC6 (origin recognition complex 6) in glioma. Through the bioinformatics analyses, we found a significant increase in ORC6 expression within human glioma tissues, correlating with poorer overall survival, higher tumor grade, and wild-type isocitrate dehydrogenase status. Additionally, ORC6 overexpression is detected in glioma tissues obtained from locally-treated patients and across various primary/established glioma cells. Further bioinformatics scrutiny revealed that genes co-expressed with ORC6 are enriched in multiple signaling cascades linked to cancer. In primary and immortalized (A172) glioma cells, depleting ORC6 using specific shRNA or Cas9-sgRNA knockout (KO) significantly decreased cell viability and proliferation, disrupted cell cycle progression and mobility, and triggered apoptosis. Conversely, enhancing ORC6 expression via a lentiviral construct augmented malignant behaviors in human glioma cells. ORC6 emerged as a crucial regulator for the expression of key oncogenic genes, including Cyclin A2, Cyclin B2, and DNA topoisomerase II (TOP2A), within glioma cells. Silencing or KO of ORC6 reduced the mRNA and protein levels of these genes, while overexpression of ORC6 increased their expression in primary glioma cells. Bioinformatics analyses further identified RBPJ as a potential transcription factor of ORC6. RBPJ shRNA decreased ORC6 expression in primary glioma cells, while its overexpression increased it. Additionally, significantly enhanced binding between the RBPJ protein and the proposed ORC6 promoter region was detected in glioma tissues and cells. In vivo experiments demonstrated a significant reduction in the growth of patient-derived glioma xenografts in the mouse brain subsequent to ORC6 KO. ORC6 depletion, inhibited proliferation, decreased expression of Cyclin A2/B2/TOP2A, and increased apoptosis were detected within these ORC6 KO intracranial glioma xenografts. Altogether, RBPJ-driven ORC6 overexpression promotes glioma cell growth, underscoring its significance as a promising therapeutic target.

Tissue metabolites in diffuse glioma and their modulations by IDH1 mutation, histology and treatment

The discovery of the oncometabolite 2-hydroxyglutarate in isocitrate dehydrogenase 1–mutated (IDH1-mutated) tumor entities affirmed the role of metabolism in cancer. However, large databases with tissue metabolites that are modulated by IDH1 mutation remain an area of development. Here, we present an unprecedented and valuable resource for tissue metabolites in diffuse glioma and their modulations by IDH1 mutation, histology, and tumor treatments in 101 tissue samples from 73 diffuse glioma patients (24 astrocytoma, 17 oligodendroglioma, 32 glioblastoma), investigated by NMR-based metabolomics and supported by RNA-Seq. We discovered comparison-specific metabolites and pathways modulated by IDH1 (IDH1 mutation status cohort) and tumor entity. The Longitudinal investigation cohort provides metabolic profiles of untreated and corresponding treated glioma samples at first progression. Most interestingly, univariate and multivariate cox regressions and Kaplan-Meier analyses revealed that tissue metabolites correlate with progression-free and overall survival. Thus, this study introduces potentially novel candidate prognostic and surrogate metabolite biomarkers for future prospective clinical studies, aiming at further refining patient stratification in diffuse glioma. Furthermore, our data will facilitate the generation of so-far–unanticipated hypotheses for experimental studies to advance our molecular understanding of glioma biology.

Epigenetic loss of RNA-methyltransferase NSUN5 in glioma targets ribosomes to drive a stress adaptive translational program

Tumors have aberrant proteomes that often do not match their corresponding transcriptome profiles. One possible cause of this discrepancy is the existence of aberrant RNA modification landscapes in the so-called epitranscriptome. Here, we report that human glioma cells undergo DNA methylation-associated epigenetic silencing of NSUN5, a candidate RNA methyltransferase for 5-methylcytosine. In this setting, NSUN5 exhibits tumor-suppressor characteristics in vivo glioma models. We also found that NSUN5 loss generates an unmethylated status at the C3782 position of 28S rRNA that drives an overall depletion of protein synthesis, and leads to the emergence of an adaptive translational program for survival under conditions of cellular stress. Interestingly, NSUN5 epigenetic inactivation also renders these gliomas sensitive to bioactivatable substrates of the stress-related enzyme NQO1. Most importantly, NSUN5 epigenetic inactivation is a hallmark of glioma patients with long-term survival for this otherwise devastating disease.

Reoperation for Recurrent Glioblastoma Multiforme

The role of reoperation for glioblastoma multiforme (GBM) recurrence is currently unknown. However, multiple studies have indicated that survival and quality of life are improved with a repeat operation at the time of disease recurrence. Prognosis is likely interdependent on several factors, including age, functional status, initial resection status, disease location, and surgical efficacy. However, there are significant data indicating no survival benefit for reoperation. This comprehensive literature review considering the controversial question of whether to operate for progressive or recurrent GBM seeks to evaluate the current available evidence and report on its conclusions.

Outcome evaluation of patients with newly diagnosed anaplastic gliomas treated in a single institution

AIM

To evaluate the outcome of newly diagnosed anaplastic glioma patients treated in our institution in relation to the 2016 WHO classification suggestions.

METHODS

This retrospective study included patients who underwent surgery plus adjuvant chemotherapy alone or concomitant and adjuvant chemoradiotherapy. Response was recorded using the Response Assessment in Neuro-Oncology criteria.

RESULTS

123 patients were analyzed. The median progression-free survival time and the 2, 3 and 5 years progression-free survival rate were 27 months, 65.5, 21.2 and 21.2%; the 2, 3 and 5 years overall survival rate were 89.7, 83.0 and 58.4%. From the univariate/multivariate analysis, the factors conditioning survival were Karnofsky performance scale, extent of resection, IDH1 mutation status and presence of 1p/19q codeletion.

CONCLUSION

The choice of adjuvant treatment have to consider molecular assessment and, in our experience, the extent of surgical resection.

MicroRNA-211 expression is down-regulated and associated with poor prognosis in human glioma

Accumulating evidence has supported the role of microRNAs in the initiation and development of malignant tumors. MicroRNA-211 (miR-211), which was reported to involve in diverse physiological activities in several cancers, was investigated for its expression in human glioma and adjacent normal brain tissues, as well as its correlation with patient prognosis. Glioma tissues and adjacent normal brain tissues were obtained from 82 patients who underwent surgical resection, and quantitative real-time polymerase chain reaction was performed to assess the expression level of miR-211. Here, we found that miR-211 was significantly decreased in glioma tissues compared with adjacent normal brain tissues (glioma, 3.52 ± 0.14 vs. normal, 4.96 ± 0.17, p < 0.001), and inversely associated with ascending WHO classification (grade III-IV, 3.16 ± 0.21 vs. grade I-II, 4.22 ± 0.26, p < 0.001). Then, the correlation of miR-211 with clinicopathological factors was investigated by Pearson's Chi square test, indicating that miR-211 might be a potential biomarker to predict the malignant status of glioma. Further, Kaplan-Meier curves with log-rank analysis were carried out to determine the relationship between miR-211 expression level and the overall survival rate of glioma patients. Our data showed that there was a close correlation between down-regulated miR-211 and shorter survival time in 82 patients (p = 0.026). Finally, the multivariate Cox regression analysis indicated that WHO grade (HR = 2.437, 95% CI 1.251-4.966, p = 0.007), KPS (HR = 2.215, 95% CI 1.168-4.259, p = 0.016), and miR-211 expression level (HR = 3.614, 95% CI 2.152-6.748, p < 0.001) were considered as independent risk factors for glioma prognosis. These results suggested that lower miR-211 expression might be a marker for poor prognosis of glioma patients.

Long-term analysis of the NOA-04 randomized phase III trial of sequential radiochemotherapy of anaplastic glioma with PCV or temozolomide

BACKGROUND

Optimal treatment and precise classification for anaplastic glioma are needed.

METHODS

The objective for long-term follow-up of NOA-04 is to optimize the treatment sequence for patients with anaplastic gliomas. Patients were randomized 2:1:1 to receive the standard radiotherapy (RT) (arm A), procarbazine, lomustine and vincristine (PCV) (arm B1), or temozolomide (TMZ) (arm B2).

RESULTS

Primary endpoint was time-to-treatment-failure (TTF), defined as progression after 2 lines of therapy or any time before if no further therapy was administered. Exploratory analyses examined associations of molecular marker status with TTF, progression-free survival (PFS), and overall survival (OS). At 9.5 (95% CI: 8.6-10.2) years, no difference between arms (A vs B1/B2) was observed: median TTF (4.6 [3.4-5.1] y vs 4.4 [3.3-5.3) y), PFS (2.5 [1.3-3.5] y vs 2.7 [1.9-3.2] y), and OS (8 [5.5-10.3] y vs 6.5 [5.4-8.3] y). Oligodendroglial versus astrocytic histology-but more so the subgroups according to CpG island methylator phenotype (CIMP) and 1p/19q co-deletion status-revealed a strong prognostic value of CIMPpos with (CIMPcodel) versus without 1p/19 co-deletion (CIMPnon-codel) versus CIMPneg. but no differential efficacy of RT versus chemotherapy for any of the endpoints. PFS was better for PCV- than for TMZ-treated patients with CIMPcodel tumors (HR B1 vs B2 0.39 [0.17-0.92], P = .031). In CIMPneg. tumors, hypermethylation of the O6-methyl-guanyl-DNA methyltransferase promoter (MGMT) provided a risk reduction for PFS with chemotherapy.

CONCLUSIONS

There is no differential activity of primary chemotherapy versus RT in any subgroup of anaplastic glioma. Molecular diagnosis is superior to histology.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00717210.

Amino-acid PET versus MRI guided re-irradiation in patients with recurrent glioblastoma multiforme (GLIAA) - protocol of a randomized phase II trial (NOA 10/ARO 2013-1)

Background

The higher specificity of amino-acid positron emission tomography (AA-PET) in the diagnosis of gliomas, as well as in the differentiation between recurrence and treatment-related alterations, in comparison to contrast enhancement in T1-weighted MRI was demonstrated in many studies and is the rationale for their implementation into radiation oncology treatment planning. Several clinical trials have demonstrated the significant differences between AA-PET and standard MRI concerning the definition of the gross tumor volume (GTV). A small single-center non-randomized prospective study in patients with recurrent high grade gliomas treated with stereotactic fractionated radiotherapy (SFRT) showed a significant improvement in survival when AA-PET was integrated in target volume delineation, in comparison to patients treated based on CT/MRI alone.

Methods

This protocol describes a prospective, open label, randomized, multi-center phase II trial designed to test if radiotherapy target volume delineation based on FET-PET leads to improvement in progression free survival (PFS) in patients with recurrent glioblastoma (GBM) treated with re-irradiation, compared to target volume delineation based on T1Gd-MRI. The target sample size is 200 randomized patients with a 1:1 allocation ratio to both arms. The primary endpoint (PFS) is determined by serial MRI scans, supplemented by AA-PET-scans and/or biopsy/surgery if suspicious of progression. Secondary endpoints include overall survival (OS), locally controlled survival (time to local progression or death), volumetric assessment of GTV delineated by either method, topography of progression in relation to MRI- or PET-derived target volumes, rate of long term survivors (>1 year), localization of necrosis after re-irradiation, quality of life (QoL) assessed by the EORTC QLQ-C15 PAL questionnaire, evaluation of safety of FET-application in AA-PET imaging and toxicity of re-irradiation.

Discussion

This is a protocol of a randomized phase II trial designed to test a new strategy of radiotherapy target volume delineation for improving the outcome of patients with recurrent GBM. Moreover, the trial will help to develop a standardized methodology for the integration of AA-PET and other imaging biomarkers in radiation treatment planning.

Trial registration

The GLIAA trial is registered with ClinicalTrials.gov (NCT01252459, registration date 02.12.2010), German Clinical Trials Registry (DRKS00000634, registration date 10.10.2014), and European Clinical Trials Database (EudraCT-No. 2012-001121-27, registration date 27.02.2012).

Integrated analysis of genome-wide DNA methylation, gene expression and protein expression profiles in molecular subtypes of WHO II-IV gliomas

Background

Glioma is the most common malignant primary brain tumor among adults, among which glioblastoma (GBM) exhibits the highest malignancy. Despite current standard chemoradiation, glioma is still invariably fatal. A further insight into the molecular background of glioma is required to improve patient outcomes.

Method

Previous studies evaluated molecular genetic differences through comparing different grades of glioma. Here, we integrated DNA methylation, RNA sequencing and protein expression data sets of WHO grade II to IV gliomas, to screen for dysregulated genes in subtypes during malignant progression of glioma.

Results

We propose a list of universal genes (UG) as novel glioma biomarkers: 977 up-regulated genes and 114 down-regulated genes, who involved in cell cycle, Wnt receptor signaling pathway and fatty acid metabolic process. Poorer survival was associated significantly with the high expression of 977 up-regulated genes and low expression of 114 down-regulated in UG (P <0.001).

Conclusion

To our knowledge, this was the first study that focused on subtypes to detect dysregulated genes that could contribute to malignant progression. Furthermore, the differentially expressed genes profile may lead to the identification of new therapeutic targets for glioma patients.

MicroRNA-mediated down-regulation of NKG2D ligands contributes to glioma immune escape

Malignant gliomas are intrinsic brain tumors with a dismal prognosis. They are well-adapted to hypoxic conditions and poorly immunogenic. NKG2D is one of the major activating receptors of natural killer (NK) cells and binds to several ligands (NKG2DL).

Here we evaluated the impact of miRNA on the expression of NKG2DL in glioma cells including stem-like glioma cells. Three of the candidate miRNA predicted to target NKG2DL were expressed in various glioma cell lines as well as in glioblastomas in vivo: miR-20a, miR-93 and miR-106b. LNA inhibitor-mediated miRNA silencing up-regulated cell surface NKG2DL expression, which translated into increased susceptibility to NK cell-mediated lysis. This effect was reversed by neutralizing NKG2D antibodies, confirming that enhanced lysis upon miRNA silencing was mediated through the NKG2D system. Hypoxia, a hallmark of glioblastomas in vivo, down-regulated the expression of NKG2DL on glioma cells, associated with reduced susceptibility to NK cell-mediated lysis. This process, however, was not mediated through any of the examined miRNA. Accordingly, both hypoxia and the expression of miRNA targeting NKG2DL may contribute to the immune evasion of glioma cells at the level of the NKG2D recognition pathway. Targeting miRNA may therefore represent a novel approach to increase the immunogenicity of glioblastoma.

Survival trends of grade I, II, and III astrocytoma patients and associated clinical practice patterns between 1999 and 2010: A SEER-based analysis

Background

The survival trends and the patterns of clinical practice pertaining to radiation therapy and surgical resection for WHO grade I, II, and III astrocytoma patients remain poorly characterized.

Methods

Using the Surveillance, Epidemiology and End Results (SEER) database, we identified 2497 grade I, 4113 grade II, and 2755 grade III astrocytomas during the period of 1999-2010. Time-trend analyses were performed for overall survival, radiation treatment (RT), and the extent of surgical resection (EOR).

Results

While overall survival of grade I astrocytoma patients remained unchanged during the study period, we observed improved overall survival for grade II and III astrocytoma patients (Tarone-Ware P < .05). The median survival increased from 44 to 57 months and from 15 to 24 months for grade II and III astrocytoma patients, respectively. The differences in survival remained significant after adjusting for pertinent variables including age, ethnicity, marital status, sex, tumor size, tumor location, EOR, and RT status. The pattern of clinical practice in terms of EOR for grade II and III astrocytoma patients did not change significantly during this study period. However, there was decreased RT utilization as treatment for grade II astrocytoma patients after 2005.

Conclusion

Results from the SEER database indicate that there were improvements in the overall survival of grade II and III astrocytoma patients over the past decade. Analysis of the clinical practice patterns identified potential opportunities for impacting the clinical course of these patients.

LRG1 modulates invasion and migration of glioma cell lines through TGF-β signaling pathway

Studies have shown that the abnormal expression of leucine-rich α2 glycoprotein 1 (LRG1) is associated with multiple malignancies, yet its role in glioma pathology remains to be elucidated. In this study, we investigated the role of LRG1 in regulating proliferation, migration and invasion of glioma cells by establishing glioma cell strains with constitutively silenced or elevated LRG1 expression. LRG1 overexpression and silenced cell lines demonstrated modulation of glioma cellular proliferation, migration and invasion through MTT, cell scratching and Transwell assays. Furthermore, overexpression of LRG1 led to augmented activation of transforming growth factor-β (TGF-β) signaling pathway as well as downregulation of E-cadherin and resultant enhanced invasiveness, which was reversed by TGF-β signaling pathway inhibitor SB431542. In summary, our findings suggest that LRG1 promotes invasion and migration of glioma cells through TGF-β signaling pathway.

Oligodendroglioma: pathology, molecular mechanisms and markers

For nearly a century, the diagnosis and grading of oligodendrogliomas and oligoastrocytomas has been based on histopathology alone. Roughly 20 years ago, the first glioma-associated molecular signature was found with complete chromosome 1p and 19q codeletion being particularly common in histologically classic oligodendrogliomas. Subsequently, this codeletion appeared to not only carry diagnostic, but also prognostic and predictive information, the latter aspect only recently resolved after carefully constructed clinical trials with very long follow-up times. More recently described biomarkers, including the non-balanced translocation leading to 1p/19q codeletion, promoter hypermethylation of the MGMT gene, mutations of the IDH1 or IDH2 gene, and mutations of FUBP1 (on 1p) or CIC (on 19q), have greatly enhanced our understanding of oligodendroglioma biology, although their diagnostic, prognostic, and predictive roles are less clear. It has therefore been suggested that complete 1p/19q codeletion be required for the diagnosis of 'canonical oligodendroglioma'. This transition to an integrated morphological and molecular diagnosis may result in the disappearance of oligoastrocytoma as an entity, but brings new challenges as well. For instance it needs to be sorted out how (histopathological) criteria for grading of 'canonical oligodendrogliomas' should be adapted, how pediatric oligodendrogliomas (known to lack codeletions) should be defined, which platforms and cut-off levels should ideally be used for demonstration of particular molecular aberrations, and how the diagnosis of oligodendroglioma should be made in centers/countries where molecular diagnostics is not available. Meanwhile, smart integration of morphological and molecular information will lead to recognition of biologically much more uniform groups within the spectrum of diffuse gliomas and thereby facilitate tailored treatments for individual patients.

MicroRNA-320 inhibits cell proliferation in glioma by targeting E2F1

MicroRNAs (miRs) are a class of small non-coding RNAs that are involved in the regulation of gene expression, and in cancer development and progression. In the present study, miR-320 expression was found to be significantly reduced in glioma tissue in comparison with that in adjacent healthy tissues. In the present study, in vitro analyses demonstrated that overexpression of miR-320 inhibited cell proliferation and metastasis, while antisense miR-320 oligonucleotides enhanced cell proliferation and migration in U251 and SHG-44 glioma cell lines, compared with that in negative control cells. Protein expression of E2F1, a cell-cycle regulator, was negatively regulated by miR-320. Therefore, the present study provides novel insights into the association between miR-320 and glioma development.

The future of high-grade glioma: Where we are and where are we going

High-grade glioma (HGG) are optimally treated with maximum safe surgery, followed by radiotherapy (RT) and/or systemic chemotherapy (CT). Recently, the treatment of newly diagnosed anaplastic glioma (AG) has changed, particularly in patients with 1p19q codeleted tumors. Results of trials currenlty ongoing are likely to determine the best standard of care for patients with noncodeleted AG tumors. Trials in AG illustrate the importance of molecular characterization, which are germane to both prognosis and treatment. In contrast, efforts to improve the current standard of care of newly diagnosed glioblastoma (GB) with, for example, the addition of bevacizumab (BEV), have been largely disappointing and furthermore molecular characterization has not changed therapy except in elderly patients. Novel approaches, such as vaccine-based immunotherapy, for newly diagnosed GB are currently being pursued in multiple clinical trials. Recurrent disease, an event inevitable in nearly all patients with HGG, continues to be a challenge. Both recurrent GB and AG are managed in similar manner and when feasible re-resection is often suggested notwithstanding limited data to suggest benefit from repeat surgery. Occassional patients may be candidates for re-irradiation but again there is a paucity of data to commend this therapy and only a minority of selected patients are eligible for this approach. Consequently systemic therapy continues to be the most often utilized treatment in recurrent HGG. Choice of therapy, however, varies and revolves around re-challenge with temozolomide (TMZ), use of a nitrosourea (most often lomustine; CCNU) or BEV, the most frequently used angiogenic inhibitor. Nevertheless, no clear standard recommendation regarding the prefered agent or combination of agents is avaliable. Prognosis after progression of a HGG remains poor, with an unmet need to improve therapy.

Assessing CpG island methylator phenotype, 1p/19q codeletion, and MGMT promoter methylation from epigenome-wide data in the biomarker cohort of the NOA-04 trial

BACKGROUND

Molecular biomarkers including isocitrate dehydrogenase 1 or 2 (IDH1/2) mutation, 1p/19q codeletion, and O(6)-methylguanine-DNA-methyltransferase (MGMT) promoter methylation may improve prognostication and guide treatment decisions for patients with World Health Organization (WHO) anaplastic gliomas. At present, each marker is individually tested by distinct assays. Illumina Infinium HumanMethylation450 BeadChip arrays (HM450) enable the determination of large-scale methylation profiles and genome-wide DNA copy number changes. Algorithms have been developed to detect the glioma CpG island methylator phenotype (G-CIMP) associated with IDH1/2 mutation, 1p/19q codeletion, and MGMT promoter methylation using a single assay.

METHODS

Here, we retrospectively investigated the diagnostic and prognostic performance of these algorithms in comparison to individual marker testing and patient outcome in the biomarker cohort (n = 115 patients) of the NOA-04 trial.

RESULTS

Concordance for IDH and 1p/19q status was very high: In 92% of samples, the HM450 and reference data agreed. In discordant samples, survival analysis by Kaplan-Meier and Cox regression analyses suggested a more accurate assessment of biological phenotype by the HM450 analysis. The HM450-derived MGMT-STP27 model to calculate MGMT promoter methylation probability revealed this aberration in a significantly higher fraction of samples than conventional methylation-specific PCR, with 87 of 91 G-CIMP tumors predicted as MGMT promoter-methylated. Pyrosequencing of discordant samples confirmed the HM450 assessment in 14 of 17 cases.

CONCLUSIONS

G-CIMP and 1p/19q codeletion are reliably detectable by HM450 analysis and are associated with prognosis in the NOA-04 trial. For MGMT, HM450 suggests promoter methylation in the vast majority of G-CIMP tumors, which is supported by pyrosequencing.