Meningioma Progression Research Articles

STMN1 as a candidate gene associated with atypical meningioma progression

ObjectivesMeningiomas are the most common type of primary intracranial tumor. Atypical meningiomas are especially difficult to manage due to frequent disease recurrence. This study aimed to examine the role of stathmin (coded by the gene STMN1) as a factor in atypical meningioma recurrence. Patients and methodsA total of 59 sporadic atypical meningioma formalin-fixed paraffin-embedded (FFPE) samples were collected. The mRNA levels of the biomarker gene STMN1 were tested using quantitative RT-PCR. ResultsWe observed significant up-regulation of STMN1 mRNA expression in recurrent tumors in comparison with primary tumors (p<0.05). Moreover, mRNA expression levels of STMN1 significantly correlated with Ki-67 score (r=0.93, p<0.01). Multivariate survival analyses indicated that high expression of STMN1, high Ki-67 score, and more advanced patient age at diagnosis (>60yrs) each act as independence prognostic factors for recurrence. Kaplan-Meier analysis revealed that STMN1 expression pattern could effectively predict prognosis of atypical meningioma in patients (p<0.01). ConclusionsOur study indicates for the first time that an increased risk of sporadic atypical meningioma recurrence can be found in cases with elevated expression of STMN1. These results suggest that STMN1 expression might serve as a biomarker for determining patient atypical meningioma prognosis.

Molecular progression in unusual recurrent non-pediatric intracranial clear cell meningioma.

We report a case of a recurrent clear cell meningioma (ccm) in the frontal lobe of the brain of a 67-year-old man. The patient developed three recurrences: at 3, 10, and 12 years after his initial surgery. Histopathology observations revealed a grade 2 ccm with positivity for vimentin and epithelial membrane antigen. Expression of E-cadherin was positive only in the primary tumour and in the first available recurrence. Fluorescence in situ hybridization analyses demonstrated 1p and 14q deletions within the last recurrence. Multiplex ligation-dependent probe amplification studies revealed a heterozygous partial NF2 gene deletion, which progressed to total loss in the last recurrence. The last recurrence showed homozygous deletions in CDKN2A and CDKN2B. The RASSF1 gene was hypermethylated during tumour evolution. In this report, we show the genetic alterations of a primary ccm and its recurrences to elucidate their relationships with the changes involved in the progression of this rare neoplasm.

Whole exome sequencing and copy-number variation analysis of 20 NF2-associated spinal and cranial meningiomas.

2051 Background: Neurofibromatosis type 2 is a heritable tumor predisposition syndrome characterized by the growth of multiple tumor types in the nervous system, including bilateral vestibular schwannomas, meningiomas and ependymomas. Recent genomic sequencing studies have revealed that NF2 inactivation is the most frequent genetic event in sporadic meningiomas. In line with Knudson’s hypothesis, it is accepted that somatic inactivation of the wildtype NF2 allele initiates tumor growth in NF2 patients, but little is known of what other genes or pathways influence meningioma tumorigenesis. Methods: To investigate this question, we performed whole exome sequencing (WES) (Illumina Hi-Seq 2500 platform, 96 Mb SeqCap EZ Exome + UTR Library, NimbleGen) and SNP-array analysis (HumanOmniExpressExome-8, v1.2 arrays, Illumina) of twenty spinal and cranial meningioma samples from seven NF2 patients. Mutation validation was completed via orthogonal sequencing (IonTorrent, ThermoFisher). Results: We identified NF2 germline mutations in all patients, including five nonsense, one splice site and one likely pathogenic intronic mutation. We found that the predominant mechanism of somatic NF2 inactivation in the tumors was loss of heterozygosity (LOH): we identified large chromosome 22 deletions containing NF2 in nineteen out of twenty meningiomas. The second most frequent chromosomal aberration was a deletion within chromosome 1p, followed by entire chromosome X deletion and rearrangements in chromosome 17q. The remaining samples exhibited normal diploid genomic architecture. Somatic mutations included about twenty point substitutions and small indels. Conclusions: Our study revealed that somatic inactivation of NF2 is the most frequent and only recurrent genetic event in NF2-associated meningiomas. Large LOH events are the most prevalent second hit mechanism and may also represent a common path of meningioma progression. Somatic single nucleotide substitutions and small indels are rare in these tumors. Interestingly, we did not identify mutations in TRAF7, KLF4, AKT1, or SMO, which have been found to be critical for non-NF2 meningioma growth.

NANOG overexpression and its correlation with stem cell and differentiation markers in meningiomas of different WHO grades.

NANOG, as a key regulator of pluripotency and acting synergistically with other factors, has been described as a crucial transcription factor in various types of cancer. In meningiomas the expression of this marker has not yet been described. With our study, we aimed to identify and localize NANOG and other possible markers of pluripotency, stem cell properties and differentiation in meningioma tissue, to elucidate a possible effect on tumorigenesis. The gene expression levels of NANOG (NANOG1 and NANOGP8), SOX2, OCT4, KLF4, ABCG2, CMYC, MSI1, CD44, NOTCH1, NES, SALL4B, TP53, and EPAS1 were quantitatively examined using RT-qPCR in 33 surgical specimens of low- (WHO grade I) as well as in high-grade (WHO grade II/III) meningiomas with dural tissue as reference. Immunofluorescence co-localization analysis following confocal fluorescence microscopy for NANOG, OCT4, SOX2, Nestin, KI-67, and CD44 was also performed. There was a significant overexpression of NANOG, MSI1, and EPAS1 and a downregulation of NES in all examined tumors. Subgroup analysis (WHO grade I versus grade II/III) revealed differences in the expression of NANOG, CD44, and MSI1. We found 1% NANOG-positive (NANOG+) cells in low-grade and 2% in grade II/III meningiomas co-expressing the other mentioned markers in various compositions. In particular, NANOG+ cells expressing SOX2 and OCT4 were successfully identified (26% low-grade versus 20% high-grade). Our data reveal an overexpression of NANOG and other markers of pluripotency and stemness in meningiomas. Such potentially pluripotent "stem cell-like" cells may have an impact on tumorigenesis and progression in human meningiomas.

P12.05 Role of Dkk-3 in the neoplastic progression of meningiomas. Could it represent a new therapeutic target?

P12.05 Role of Dkk-3 in the neoplastic progression of meningiomas. Could it represent a new therapeutic target?

Transforming Growth Factor Beta Family in the Pathogenesis of Meningiomas.

Meningiomas account for 36% of primary brain tumors. The pathogenesis of these tumors is not completely established, hindering development of effective chemotherapy. Numerous studies have identified alterations in several growth factors and receptor kinases that regulate meningioma growth. These may be targets for new therapies. One of these, sometimes overlooked, is the transforming growth factor beta (TGF-β) family of proteins. Its receptors and signaling pathways play a critical role in development or progression of many forms of neoplasia. Evidence suggesting a potential role for TGF-β, bone morphogenetic protein, and their mediators is reviewed. TGF-β inhibition of growth in normal leptomeninges may be lost in neoplasia. Moreover, loss of TGF-β and bone morphogenetic protein signaling components and TGF-β type III receptor likely contribute to the development and/or progression of higher grade meningiomas. Accumulating evidence suggests that derangement of TGF-β family signaling contributes to development and progression of meningiomas. The TGF-β family may represent new targets for chemotherapy and could include inhibitors of kinases activated by TGF-β.

Tissue thioredoxin-interacting protein expression predicted recurrence in patients with meningiomas.

The redox regulatory protein, thioredoxin-interacting protein (TXNIP), has been confirmed as an important tumor suppressor gene in various types of human cancers. In previous studies, we found that overexpression of tumor suppressor gene RIZ1 in meningiomas can significantly improve the expression of TXNIP by microarray data analysis. Therefore, we hypothesized that TXNIP was associated with the initiation and progression of meningiomas. First, we evaluated the expression of TXNIP and Ki-67 in meningioma tissues from 65 patients using immunohistochemistry. We also analyzed the correlation between TXNIP immunoreactivity and clinicopathological features, as well as patient prognostic factors. According to immunohistochemistry results, high-grade meningioma tissues had significantly lower expression of TXNIP than benign meningioma tissues (29.31±18.70 vs 74.61±7.51, P<0.0001). TXNIP and Ki67 were negatively correlated (P<0.0001). Moreover, the expression of TXNIP was higher in nonrecurrent high-grade meningiomas (P<0.05). In addition, Kaplan-Meier analysis indicated that expression of TXNIP and Ki-67 was related to recurrence-free time. Multivariate Cox analysis showed that TXNIP expression level was the only independent predictor for meningioma prognosis. Our results demonstrated that high expression of TXNIP indicates a lower pathological grade of meningnioma, and is also associated with longer recurrence-free time. Therefore, TXNIP could be regarded as a potential molecular marker to predict recurrence in patients with meningiomas.

Dysregulation of Apoptosis Caused by Aberrant Histone Modification Influences on the Recurrence of Meningiomas

Background: Alteration of apoptosis is related with progression and recurrence of atypical meningiomas (AMs). However, no comprehensive study has been conducted regarding histone modification regulating apoptosis in AMs. This study was aimed to determine the prognostic values of certain apoptosis-associated factors, and examine the role of histone modification on apoptosis in AMs. Materials and method: The medical records of 67 patients with AMs, as diagnosed during recent 13 years, were reviewed retrospectively. Immunohistochemical staining was performed on archived paraffin-embedded tissues for pro-apoptotic factors (CASP3, IGFBP, TRAIL-R1, BAX, and XAF1), anti-apoptotic factors (survivin, ERK, RAF1, MDM2, and BCL2), and the histone modifying enzymes (MLL2, RIZ, EZH1, NSD2, KDM5c, JMJD2a, UTX, and JMJD5). Results: Twenty-six (38.8%) patients recurred during the follow-up period (mean duration 47.7 months). In terms of time-to-recurrence (TTR), overexpression of CASP3, TRAIL-R1, and BAX had a longer TTR than underexpression, and overexpression of Survivin, MDM2, and BCL2 had a shorter TTR than underexpression (P<0.05). Additionally, overexpression of MLL2, UTX, and JMJ5 had shorter TTRs than underexpression, and overexpression of KDM5c had a longer TTR than underexpression. However, in the multi-variate analysis of predicting factors for recurrence, underexpression of CASP3 (P<0.001), and BAX (P<0.001), and overexpression of survivin (P=0.007), and MDM2 (P=0.037) were associated with recurrence independently, but any enzymes modifying histone were not associated with recurrence. Conclusion: This study suggests certain apoptosis-associated factors should be associated with recurrence of AMs, which may be regulated epigenetically by histone modifying enzymes.

Evaluation of Venous Drainage Patterns for Skull Base Meningioma Surgery.

The evaluation of venous drainage patterns prior to surgery for skull base meningioma is important owing to their deep location and the vulnerability of surrounding vascular structures. In recent years, the microsurgical skull base approach has matured as a surgical technique, making it an important option for reducing complications related to skull base meningioma surgery. In addition, knowledge of the venous anatomy can prevent venous drainage route disturbance and potentially life-threatening complications. Hence, this topic review aimed to provide an overview of normal venous anatomy as it relates to the microsurgical skull base approach, discuss known changes in venous drainage routes that are associated with the progression of skull base meningioma and the selection of an appropriate operative approach with the highest likelihood of preserving venous drainage structures.

Quantitative analysis of tumor-infiltrating lymphocytes in meningiomas of the brain

Tumor-infiltrating lymphocytes (TIL) are an important component of the microenvironment in brain tumors and particularly in meningiomas. It is considered that immune cell infiltrates in meningiomas of the brain are composed of different populations of immune cells that perform a wide range of functions.Objective: To investigate the quantitative composition and distribution of CD4, CD8, CD20 tumor-infiltrating lymphocytes (TIL) in the tumor microenvironment of the brain meningiomas.Material and methods. Using immunohistochemistry 60 cases of meningiomas were analyzed.Results. The lowest quantity of CD4+ and CD8+ TIL was established in angiomatous subtypes and the median amount of CD4+ and CD8+ TIL in meningothelial subtypes was the highest, it was equal to 9 (1; 26) and 16 (8; 47) cells respectively. It was found that the number of CD4+ TIL was significantly higher in meningothelial variants than the number of CD4+ TIL in angiomatous (p = 0,035) and fibroblastic cases (p = 0,040). The number of CD8+ TIL in meningothelial subtypes was statistically significantly higher than in angiomatous (p = 0,010) and transitional (p = 0,003). We revealed that in grade I meningiomas number of CD8+ TIL significantly exceeded the number of CD4+ TIL (p = 0,003). The CD8+/CD4+ TIL ratio was 1,66. The median number of CD4+ TIL in anaplastic meningiomas was 9 (3; 20) cells, and CD8+ TIL – 14 (9; 80) cells. Although the number of CD8+ TIL exceeded the number of CD4+ TIL, but the results were not statistically significant (p = 0,164). The CD8+/CD4+ TIL ratio was 2,99. Median quantity of CD20+ TIL was increased in the following row: fibroblastic – 1 (0; 6) cells, transitional – 5,5 (0; 10) cells, meningothelial – 14,5 (0; 39) cells and anaplastic meningiomas – 24 (2,5; 46) cells.Conclusions. In benign meningiomas quantity of CD8+ TIL significantly exceeded the number of CD4+ TIL, that can play an important role in limiting the rate of growth of these tumors. There was no statistically significant difference in the number of CD4+, CD8+ and CD20+ TIL between grade I and grade III meningiomas. Interaction of immune cells in the tumor microenvironment is complex and largely depends on the phenotype of TIL, its establishment will be able to uncover the mechanisms of progression in anaplastic meningiomas.

OS14 - 208 The prognostic role of pre-operative complete blood count (CBC) in progression-free survival in patients with meningioma

Factors which might influence outcome in patients with meningioma are not well-understood. Previous studies have examined associations of laboratory blood values including hemoglobin levels with patient outcomes in cancer. We hypothesized those changes in CBC before tumor resection can be used as one of the prognostic factors for tumor recurrence/progression in meningioma. To address this, we gathered the clinical and pre-operative CBC results for final analysis from 226 patients (64 males and 162 females) who underwent craniotomy for primary meningioma (grades: 157 WHO GI, 59 GII, 10 GIII) at our institution between 2001 and 2015.Individual parameters were analyzed for correlation with progression-free survival. The median recurrence free survival (RFS) was not reached and follow-up ranged 0.3-14 years. Fifty-six patients (25%) had anemia and 30% of the patients showed leukocytosis using standard cut-offs. On univariate analyses, low hemoglobin (Hb) level, as well as high leukocytes (Lkc), neutrophil (Neutro) and monocyte counts correlated with worse RFS. As expected, tumor grade was correlated with RFS. Low Hb level, high Lkc and Neutro counts were all significantly associated with RFS after adjusting for grade. Strikingly, 32% of patients with pre-operative anemia experienced a recurrence at 5 years, compared with only 11% of non-anemic patients. Conclusion: In this exploratory study, we find that pre-operative CBC data, which is readily available, may contain prognostic information relevant to subsequent risk of recurrence or progression in meningioma. While the biological mechanism for these associations is not clear, they represent hypotheses for further investigation.

Genetic landscape of meningioma.

Meningioma is the most common intracranial tumor, arising from arachnoid cells of the meninges. Monosomy 22 and inactivating mutations of NF2 are well-known genetic alterations of meningiomas. More recently, mutations in TRAF7, AKT1, KLF4, SMO, and PIK3CA were identified by next-generation sequencing. We here reviewed 553 meningiomas for the mutational patterns of the six genes. NF2 aberration was observed in 55% of meningiomas. Mutations of TRAF7, AKT1, KLF4, PIK3CA, and SMO were identified in 20, 9, 9, 4.5, and 3% of cases, respectively. Altogether, 80% of cases harbored at least one of the genetic alterations in these genes. NF2 alterations and mutations of the other genes were mutually exclusive with a few exceptions. Clinicopathologically, tumors with mutations in TRAF7/AKT1 and SMO shared specific features: they were located in the anterior fossa, median middle fossa, or anterior calvarium, and most of them were meningothelial or transitional meningiomas. TRAF7/KLF4 type meningiomas showed different characteristics in that they occurred in the lateral middle fossa and median posterior fossa as well as anterior fossa and median middle fossa, and contained a secretory meningioma component. We also discuss the mutational hotspots of these genes and other genetic/cytogenetic alterations contributing to tumorigenesis or progression of meningiomas.

Altered tryptophan metabolism in human meningioma.

Meningiomas are the neoplasms that arise from the arachnoid cells of the meninges. It was reported that cancer cells escape from immune system through the metabolism of an aromatic essential amino acid tryptophan (TRP) via Kynurenine (KYN) pathway. However, the role of TRP metabolites such as, 5-Hydroxy tryptophan (5-HTP), 5-Hydroxy tryptamine (5-HT), N-acetyl serotonin (NAS), Melatonin (MEL), KYN, N-acetyl tryptamine, 5-Hydroxy indole acetic acid (5-HIAA) and 5-Methoxy indole acetic acid is not yet evaluated in human meningioma. Therefore, in the current study we have evaluated the levels of TRP and its metabolites in the progression of human meningioma using tumor biopsy samples and autopsy control meninges with Reverse Phase-HPLC. We here report that TRP metabolism favors towards KYN pathway in human meningioma and it could be due to increased indoleamine 2,3-dioxygenase 2 levels as we found its m-RNA levels to be up regulated in human meningioma. We observed significant increase in KYN and 5HIAA levels and significant decrease in TRP, 5-HTP, 5-HT, NAS and MEL levels in meningioma compared to control meninges. Since TRP metabolites regulate inducible nitric oxide synthase (INOS) gene expression and thereby nitric oxide (NO) production, we have also evaluated the INOS and NO levels. The INOS and NO levels were up regulated in human meningioma. The present data corroborates with existing data on TRP metabolism in tumor progression and may serve to target TRP metabolism as a therapeutic intervention.

Classification of human meningiomas: lights, shadows, and future perspectives.

Meningiomas represent the most common primary tumors of the central nervous system (CNS) in adulthood. They are currently classified into several histotypes and into three grades of malignancy according to the criteria of the World Health Organization (WHO) classification of tumors of the CNS. WHO histological grade is currently the most significant morphological predictor of recurrence risk of meningiomas. For this reason, it is fully taken into consideration in postsurgical therapeutic decision making in patients with meningioma. However, the main drawback of the WHO grading system system is that criteria for its assessment are rather subjective and poorly standardized. Hence, additional factors are warranted to predict recurrence risk of meningiomas, so that patients may actually receive the most appropriate therapy. In recent years, biomolecular pathogenesis of meningiomas has been partially clarified, and many efforts have been made in the identification of molecular factors associated with recurrence risk of meningioma. Here we review WHO criteria currently used for classification of meningiomas and discuss on pitfalls and limits of grading assessment. In addition we present the latest advancement in the knowledge of biomolecular alterations involved in the pathogenesis and progression of meningiomas. Similarly to what has already happened for gliomas, a novel classification integrating histology and molecular information might overcome the limits of histological classification in terms of reproducibility as well as of prognostic and predictive relevance. © 2016 Wiley Periodicals, Inc.

Microarray Expression Data Identify DCC as a Candidate Gene for Early Meningioma Progression.

Meningiomas are the most common primary brain tumors bearing in a minority of cases an aggressive phenotype. Although meningiomas are stratified according to their histology and clinical behavior, the underlying molecular genetics predicting aggressiveness are not thoroughly understood. We performed whole transcript expression profiling in 10 grade I and four grade II meningiomas, three of which invaded the brain. Microarray expression analysis identified deleted in colorectal cancer (DCC) as a differentially expressed gene (DEG) enabling us to cluster meningiomas into DCC low expression (3 grade I and 3 grade II tumors), DCC medium expression (2 grade I and 1 grade II tumors), and DCC high expression (5 grade I tumors) groups. Comparison between the DCC low expression and DCC high expression groups resulted in 416 DEGs (p-value < 0.05; fold change > 2). The most significantly downregulated genes in the DCC low expression group comprised DCC, phosphodiesterase 1C (PDE1C), calmodulin-dependent 70kDa olfactomedin 2 (OLFM2), glutathione S-transferase mu 5 (GSTM5), phosphotyrosine interaction domain containing 1 (PID1), sema domain, transmembrane domain (TM) and cytoplasmic domain, (semaphorin) 6D (SEMA6D), and indolethylamine N-methyltransferase (INMT). The most significantly upregulated genes comprised chromosome 5 open reading frame 63 (C5orf63), homeodomain interacting protein kinase 2 (HIPK2), and basic helix-loop-helix family, member e40 (BHLHE40). Biofunctional analysis identified as predicted top upstream regulators beta-estradiol, TGFB1, Tgf beta complex, LY294002, and dexamethasone and as predicted top regulator effectors NFkB, PIK3R1, and CREBBP. The microarray expression data served also for a comparison between meningiomas from female and male patients and for a comparison between brain invasive and non-invasive meningiomas resulting in a number of significant DEGs and related biofunctions. In conclusion, based on its expression levels, DCC may constitute a valid biomarker to identify those benign meningiomas at risk for progression.

Expression and gene doses changes of the p53-regulator PPM1D in meningiomas: a role in meningioma progression?

The aim of our study was to clarify the expression and gene copy number levels of protein phosphatase 1D magnesium-dependent, delta isoform (PPM1D), which is thought to be a regulator of the p53 protein in meningiomas of all three different WHO grades. Genomic DNA and mRNA were extracted from frozen tissues of meningiomas (WHO grade I, 20 cases; grade II, 17 cases; grade III, 20 cases). For analysis of the mRNA expression and gene dosage level of PPM1D, semiquantitative duplex RT-PCR, real-time RT-PCR, and semiquantitative duplex PCR were performed. We also analyzed several genes which locate near PPM1D in the genomic locus 17q22-24 using semiquantitative duplex RT-PCR. We found that the mean mRNA expression of PPM1D is higher in WHO grade II and III meningiomas than in grade I tumors. This finding is accompanied by moderate gene dosage increases for PPM1D in meningiomas of higher grades. Other genes located in the vicinity of PPM1D also showed mRNA overexpression in single meningioma cases. For these genes, however, no significant expression differences between meningioma grades could be observed. Thus, PPM1D in the chromosomal location 17q22-24 might be the most relevant candidate gene with respect to a potential functional implication in meningioma progression.

Aryl hydrocarbon receptor (AHR) signalling pathway is activated and involved in tumor progression of human meningioma

Aryl hydrocarbon receptor (AHR) signalling pathway is activated and involved in tumor progression of human meningioma

MNGO-10IMPACT OF MULTIPLE SCLEROSIS (MS) AND ITS IMMUNOMODULATORY TREATMENT ON MENINGIOMA OUTCOMES

BACKGROUND: Meningioma is rarely described in the MS literature and the influence of immunomodulatory treatment is not known. There are only a few case reports on the relationship of MS and meningioma, some of which suggest progression of disease with MS treatment. METHOD: We retrospectively reviewed patients diagnosed with MS by Macdonald criteria and meningioma from January 1992 to December 2014. RESULTS: We identified 7 women, median age of 65 (range: 46-69), with both MS and meningioma. Six patients were followed for a median of 9 years (range: 1 month-10 years). Two were never treated with any disease modifying therapy (DMT), 3 were treated with interferon-beta 1a (IFNb-1a), 1 with glatiramer acetate then, natalizumab, and 1 with IFNb-1a then, natalizumab. At the time of meningioma diagnosis, 4 had not been treated with any DMT, 2 were on IFNb-1a, and 1 was on glatiramer acetate. In six cases, meningioma was diagnosed after the MS diagnosis (median of 11 years, range of 0- 21 years). Of the 7 patients identified, meningioma progression necessitated tumor treatment in 4 patients; 3 surgical resections, 1 stereotactic radiosurgery. Histology of all resected tumors was WHO grade I. Of these patients, 2 were on IFNb-1a and 2 never received DMT. The one patient who had stereotactic radiosurgery was on treatment with IFNb-1a during meningioma growth period. This patient had multiple complications due to radiation necrosis. The remaining 3 patients treated for MS did not require treatment of their meningioma. CONCLUSION: In this small series of patients with both MS and meningioma, tumor progression necessitating treatment in patients receiving DMT or off DMT. In the one patient who received stereotactic radiosurgery, radiation caused severe complications.

NDRG4 is a novel oncogenic protein and p53 associated regulator of apoptosis in malignant meningioma cells.

Aggressive meningiomas exhibit high levels of recurrence, morbidity and mortality. When surgical and radiation options are exhausted, there is need for novel molecularly-targeted therapies. We have recently identified NDRG4 overexpression in aggressive meningiomas. NDRG4 is a member of the N-Myc Downstream Regulated Gene (NDRG) family of the alpha/beta hydrolase superfamily. We have demonstrated that NDRG4 downregulation results in decreased cell proliferation, migration and invasion. In follow up to our prior studies; here we demonstrate that the predominant form of cell death following NDRG4 silencing is apoptosis, utilizing Annexin-V flow cytometry assay. We show that apoptosis caused by p53 upregulation, phosphorylation at Ser15, BAX activation, Bcl-2 and BcL-xL downregulation, mitochondrial cytochrome c release and execution of caspases following NDRG4 depletion. Sub-cellular distribution of BAX and cytochrome c indicated mitochondrial-mediated apoptosis. In addition, we carried out the fluorescence cytochemical analysis to confirm mitochondrial-mediated apoptosis by changes in mitochondrial membrane potential (Ψm), using JC-1 dye. Immunoprecipitation and immunofluorescence confirmed binding of NDRG4 to p53. In addition, we demonstrate that apoptosis is mitochondrial and p53 dependent. The proapoptotic effect of p53 was verified by the results in which a small molecule compound PFT-α, an inhibitor of p53 phosphorylation, is greatly protected against targeting NDRG4 induced apoptosis. These findings bring novel insight to the roles of NDRG4 in meningioma progression. A better understanding of this pathway and its role in meningioma carcinogenesis and cell biology is promising for the development of novel therapeutic targets for the management of aggressive meningiomas.

ARID1A and TERT promoter mutations in dedifferentiated meningioma

Unlike patients with World Health Organization (WHO) grade I meningiomas, which are considered benign, patients with WHO grade III meningiomas have very high mortality rates. The principles underlying tumor progression in meningioma are largely unknown, yet a detailed understanding of these mechanisms will be required for effective management of patients with these high grade lethal tumors. We present a case of an intraventricular meningioma that at first presentation displayed remarkable morphologic heterogeneity-composed of distinct regions independently fulfilling histopathologic criteria for WHO grade I, II, and III designations. The lowest grade regions had classic meningothelial features, while the highest grade regions were markedly dedifferentiated. Whereas progression in meningiomas is generally observed during recurrence following radiation and systemic medical therapies, the current case offers us a snapshot of histologic progression and intratumoral heterogeneity in a native pretreatment context. Using whole exome sequencing and high resolution array-based comparative genomic hybridization, we observed marked genetic heterogeneity between the various areas. Notably, in the higher grade regions we found increased aneuploidy with progressive loss of heterozygosity, the emergence of mutations in the TERT promoter, and compromise of ARID1A. These findings provide new insights into intratumoral heterogeneity in the evolution of malignant phenotypes in anaplastic meningiomas and potential pathways of malignant progression.