The molecular genetics and tumor pathogenesis of meningiomas and the future directions of meningioma treatments

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.

Molecular typing of Meningiomas by Desorption Electrospray Ionization Mass Spectrometry Imaging for Surgical Decision-Making

Meningiomas are the most frequent intracranial tumors. The majority is benign slow-growing tumors but they can be difficult to treat depending on their location and size. While meningiomas are well delineated on magnetic resonance imaging by their uptake of contrast, surgical limitations still present themselves from not knowing the extent of invasion of the dura matter by meningioma cells. The development of tools to characterize tumor tissue in real or near real time could prevent recurrence after tumor resection by allowing for more precise surgery, i.e. removal of tumor with preservation of healthy tissue. The development of ambient ionization mass spectrometry for molecular characterization of tissue and its implementation in the surgical decision-making workflow carry the potential to fulfill this need. Here, we present the characterization of meningioma and dura mater by desorption electrospray ionization mass spectrometry to validate the technique for the molecular assessment of surgical margins and diagnosis of meningioma from surgical tissue in real-time. Nine stereotactically resected surgical samples and three autopsy samples were analyzed by standard histopathology and mass spectrometry imaging. All samples indicated a strong correlation between results from both techniques. We then highlight the value of desorption electrospray ionization mass spectrometry for the molecular subtyping/subgrouping of meningiomas from a series of forty genetically characterized specimens. The minimal sample preparation required for desorption electrospray ionization mass spectrometry offers a distinct advantage for applications relying on real-time information such as surgical decision-making. The technology here was tested to distinguish meningioma from dura mater as an approach to precisely define surgical margins. In addition we classify meningiomas into fibroblastic and meningothelial subtypes and more notably recognize meningiomas with NF2 genetic aberrations.

Expression of c-MET in Invasive Meningioma

Background:

Meningiomas show high recurrence rates even after curative tumor removal. The invasiveness of meningiomas may contribute to their high recurrence rates. Recently, c-MET and hepatocyte growth factor (HGF) have been reported to be involved in cancer invasion.

Methods:

We examined the immunohistochemical expression of c-MET and HGF in 100 cases of patients with meningiomas who have undergone complete tumor removal.

Results:

c-MET^-High and HGFHigh were found in 17% and 13% of meningiomas, respectively. Brain invasion was observed in 17.6% of c-MET^-High meningiomas, but in only 2.4% of c-MET^-Low meningiomas (p=.033). Bone/soft tissue invasion was observed in 23.5% of c-MET^-High meningiomas and in 9.6% of c-MET^-Low meningiomas (p=.119). HGF^-High did not show statistical association with brain invasion or bone/soft tissue invasion. c-MET^-High demonstrated shorter recurrence-free survival (RFS, 93.5±8.2 months vs 96.1±1.9 months); however, this difference was not statistically significant (p=.139). There was no association of HGF^-High with RFS.

Conclusions:

This study demonstrates that c- MET^-High is associated with brain invasion of meningiomas, and that c-MET expression may be a useful predictive marker for meningioma recurrence. Patients with invasive meningiomas with high expressions of c-MET may be good candidates for targeted therapy using c-MET inhibitors.

Brain tumors: Special characters for research and banking

A brain tumor is an intracranial neoplasm within the brain or in the central spinal canal. Primary malignant brain tumors affect about 200,000 people worldwide every year. Brain cells have special characters. Due to the specific properties of brain tumors, including epidemiology, growth, and division, investigation of brain tumors and the interpretation of results is not simple. Research to identify the genetic alterations of human tumors improves our knowledge of tumor biology, genetic interactions, progression, and preclinical therapeutic assessment. Obtaining data for prevention, diagnosis, and therapy requires sufficient samples, and brain tumors have a wide range. As a result, establishing the bank of brain tumors is very important and essential.

Tentorial meningiomas: surgical options, clinical feature and management experience in 43 patients

OBJECTIVE

To investigate the optimal treatments and the prognostic factors of the tentorial meningiomas (TMs).

METHODS

The data of clinical symptom, imaging examination, surgical approaches as well as the influence factors of gross total resection (GTR) of 43 TMs cases were analyzed retrospectively.

RESULT

Imaging examinations of computer tomography (CT) and magnetic resonance image (MRI) were performed in all 43 cases. The angiographies such as computer tomography angiography (CTA), digital subtraction angiography (DSA), magnetic resonance angiography (MRA) and magnetic resonance venography (MRV) were obtained in part of these cases. The TMs can be classified into 2 types as superior/inferior to the tentorium, and subtypes as medial/lateral, anterior/middle/posterior according its location and the origination of the tumor. Six different surgical approaches were utilized in the study mainly depending on the tumor location and the surgeon's preference. CT scan was performed in all patients 6h after the operation. Follow-up MRI with contrast was also obtained 3 months later. Simpson's grade of excision was applied. GTR was defined as Simpson grade I and II, and was acquired in 34 cases, in which Simpson grade I resection was accomplished in 15 cases, and subtotal resection (STR) was defined as more than 90% of the tumor volume was removed and was acquired in 7 cases; histopathology revealed 34 benign (grade I), 8 atypical (grade II), and 1 malignant (grade III) cases.

CONCLUSION

Elaborate imaging examination, microsurgical skills as well as the choices of approaches and management of the sinus involved are the main prognostic factors of the TMs.

Molecular genetics of meningiomas: Building the roadmap towards personalized therapy

New advances have recently been made in the field of molecular genetics and mouse modeling of meningiomas, opening new perspectives for future treatments. Recent genome-wide genotyping and exome sequencing studies have confirmed the pivotal role of NF2 in meningioma tumorigenesis, concerning roughly half of the tumors, and unraveled new mutations in non-NF2 meningiomas concerning AKT1, SMO, KLF4 and TRAF7. The molecular mechanisms underlying tumorigenesis of high histological grades have been progressively deciphered with the recent discovery of TERT promoter mutations in progressing tumors. A better understanding of the genetics and clinical behavior of high-grade meningiomas is mandatory in order to better design future clinical trials. New genetically engineered mouse models of benign and histologically aggressive meningioma represent a substantial resource for the establishment of relevant pre-clinical trials. By studying the mechanisms underlying these new tumorigenesis pathways and the corresponding mouse models, we should be able to offer personalized chemotherapy to patients with surgery- and radiation-refractory meningiomas in the near future.

Results of immunohistochemical staining for cell cycle regulators predict the recurrence of atypical meningiomas

OBJECT

The aim of this study was to evaluate the role of certain cell-cycle regulatory proteins in the recurrence of atypical meningiomas. These proteins were analyzed with immunohistochemical staining to identify predisposing factors for the recurrence of atypical meningiomas.

METHODS

The authors retrospectively reviewed the medical records of patients with atypical meningiomas diagnosed in the period from January 2000 to June 2012 at the Department of Neurosurgery at Samsung Changwon Hospital and Dong-A University Medical Center. Clinical data included patient sex and age at the time of surgery, presenting symptoms at diagnosis, location and size of tumor, extent of surgery, use of postoperative radiotherapy, duration of follow-up, and recurrence. Immunohistochemical staining for cell-cycle regulatory proteins (p16, p15, p21, p27, cyclin-dependent kinase [CDK] 4 and 6, phosphorylated retinoblastoma [pRB] protein, and cyclin D1) and proliferative markers (MIB-1 antigen, mitosis, and p53) was performed on archived paraffin-embedded tissues obtained during resection. The recurrence rate and time to recurrence were assessed using Kaplan-Meier analysis.

RESULTS

Of the 67 atypical meningiomas eligible for analysis, 26 (38.8%) recurred during the follow-up period (mean duration 47.7 months, range 8.4-132.1 months). Immunohistochemically, there was overstaining for p16 in 44 samples (65.7%), for p15 in 21 samples (31.3%), for p21 in 25 samples (37.3%), for p27 in 32 samples (47.8%), for CDK4 in 38 samples (56.7%), for CDK6 in 26 samples (38.8%), for pRB protein in 42 samples (62.7%), and for cyclin D1 in 49 samples (73.1%). Multivariate analysis using the Cox proportional-hazards regression model showed that incomplete resection (HR 4.513, p < 0.001); immunohistochemical understaining for p16 (HR 3.214, p < 0.001); immunohistochemical overstaining for CDK6 (HR 3.427, p < 0.001), pRB protein (HR 2.854, p = 0.008), and p53 (HR 2.296, p = 0.040); and increased MIB-1 labeling index (HR 2.665, p = 0.013) and mitotic index (HR 2.438, p = 0.024) predicted the recurrence of atypical meningiomas after resection.

CONCLUSIONS

Findings in this study indicated that p16, CDK6, and pRB protein were associated with the recurrence of atypical meningiomas.

To repeat or to recreate: a contralateral posterior interhemispheric transfalcine transprecuneus approach for recurrent meningiomas at the trigone of the lateral ventricle

Surgery in the trigone of the lateral ventricle remains a challenge for neurosurgeons. In recurrent trigonal meningiomas (RTM), the disturbance of normal anatomic structures and adhesion due to previous surgeries, significant oedema, and their malignant properties heighten the difficulties associated with their surgical removal. This report presents two patients with recurrent meningiomas with anaplastic transformation at the trigone of the lateral ventricle who were successfully treated with contralateral posterior interhemispheric transfalcine transprecuneus (CITT) surgeries. The primary tumours were both completely removed through a transparietal approach in previous surgeries, but both patients experienced hemianopsia postoperatively. The second surgeries resulted in the complete resection of the recurrent tumours without any new-onset neurological dysfunction. The CITT approach suits most trigonal lesions with advantages of optic radiation preservation, reduction of retraction, improved exposure, and navigation accuracy, and because it addresses the origin of the trigonal lesion. Although the characteristics of RTM heighten the difficulty associated with their surgical removal, these challenges highlight the advantages of the CITT approach. In conclusion, the CITT approach is a safe and effective procedure for the removal of RTM.

Masked hypodiploidy in anaplastic meningiomas by duplication of the original clone found in atypical meningiomas: illustration of the evolution of genetic alterations

Meningiomas are common, usually benign neoplasms of the central nervous system. Atypical and anaplastic meningiomas can be aggressive, show more rapid growth, and a greater propensity to recur following resection. General consensus believes that genetic abnormalities leading to anaplastic transformation are present at initial tumor presentation; however, this has not been demonstrated by array-comparative genome hybridization. We confirm the hypothesis by showing the evolution of genetic alterations in the transformation of an atypical meningioma to an anaplastic meningioma. Additionally, we provide potential genes responsible for malignant transformation of meningiomas, which, with further research, may provide diagnostic and therapeutic implications.

A phase II trial of PTK787/ZK 222584 in recurrent or progressive radiation and surgery refractory meningiomas

When surgery and radiation are no longer treatment options, salvage systemic therapy has been used for recurrent meningiomas with little compelling evidence to suggest effectiveness. Patients with surgery and radiation refractory recurrent meningiomas were treated with the oral multifunctional tyrosine kinase inhibitor PTK787/ZK 222584 (PTK787) at a dose of 500 mg twice a day. Each treatment cycle was 4 weeks with MRI done every 8 weeks. Twenty-five patients (14 men; 11 women) with a median age of 59 years and KPS of 80 were treated. Meningioma WHO Grade was I in 2 patients, II in 14 patients and III in 8 patients; 1 patient had a hemangiopericytoma. All patients had prior surgery, external beam radiation therapy or radiosurgery and 11 patients prior systemic chemotherapy. Median number of cycles of PTK 787 administered was 4 (range <1-22). Best response in the 22 evaluable patients was stable disease in 15 (68.2 %). Predominant PTK787 related toxicities included fatigue (60 %), hypertension (24 %) and elevated transaminases (24 %). Grade II patients had a progression free survival (PFS)-6 of 64.3 %, a median PFS of 6.5 months and an overall survival (OS) of 26.0 months; grade III patients had a PFS-6 of 37.5 %, median PFS of 3.6 months and OS 23 months. PTK787 was modestly toxic at the dose of 500 mg administered twice per day. Activity as determined by PFS-6 suggests that targeting PDGF/VEGF pathway warrants further investigation.

Current standing and frontiers of gene therapy for meningiomas

Meningiomas are among the most common intracranial tumors. The treatment of choice for these lesions is complete resection, but in 50% of cases it is not achieved due to tumor location and/or surgical morbidities. Moreover, benign meningiomas have high recurrence rates of up to 32% in long-term follow-up. Molecular analyses have begun to uncover the genetics behind meningiomas, giving rise to potential genetics-based treatments, including gene therapy. The authors performed a literature review on the most relevant genes associated with meningiomas and both current and potential gene therapy strategies to treat these tumors. Wild-type NF2 gene insertion, oncolytic viruses, and transfer of silencing RNA have all shown promising results both in vitro and in mice. These strategies have decreased meningioma cell growth, proliferation, and angiogenesis. However, no clinical trial has been done to date. Future research and trials in gene insertion, selective inhibition of oncogenes, and the use of oncolytic viruses, among other potential treatment approaches, may shape the future of meningioma management.

The role of radiosurgery in the management of WHO Grade II and III intracranial meningiomas

Object

WHO Grade II and III intracranial meningiomas are uncommon, but they portend a significantly worse prognosis than their benign Grade I counterparts. The mainstay of current management is resection to obtain cytoreduction and histological tissue diagnosis. The timing and benefit of postoperative fractionated external beam radiation therapy and stereotactic radiosurgery remain controversial. The authors review the stereotactic radiosurgery outcomes for Grade II and III meningiomas.

Methods

A comprehensive literature search was performed using PubMed to identify all radiosurgery series reporting the treatment outcomes for Grade II and III meningiomas. Case reports and case series involving fewer than 10 patients were excluded.

Results

From 1998 to 2013, 19 radiosurgery series were published in which 647 Grade II and III meningiomas were treated. Median tumor volumes were 2.2–14.6 cm3. The median margin doses were 14–21 Gy, although generally the margin doses for Grade II meningiomas were 16–20 Gy and the margin doses for Grade III meningiomas were 18–22 Gy. The median 5-year PFS was 59% for Grade II tumors and 13% for Grade III tumors, which may have been affected by patient age, prior radiation therapy, tumor volume, and radiosurgical dose and timing. The median complication rate following radiosurgery was 8%.

Conclusions

The current data for radiosurgery suggest that it has a role in the management of residual or recurrent Grade II and III meningiomas. However, better studies are needed to fully define this role. Due to the relatively low prevalence of these tumors, it is unlikely that prospective studies will be feasible. As such, well-designed retrospective analyses may improve our understanding of the effect of radiosurgery on tumor recurrence and patient survival and the incidence and impact of treatment-induced complications.

Convexity en plaque meningioma manifesting as subcutaneous mass: case report

A 67-year-old woman sensed a slowly growing, painless hard mass in the left parietal region. Cranial computed tomography showed focal bony erosion and homogeneous sclerotic change at the affected site. Magnetic resonance (MR) imaging revealed an enhanced subcutaneous mass and irregularly thickened dura mater. Intraoperatively, the subcutaneous tumor was found to be strongly adhered to the temporalis muscle. The outer table was eroded adjacent to the subcutaneous tumor, whereas the bony structures of the inner table were intact. The dura mater underneath had irregular-shaped, yellowish convolutions both on the outer and inner surfaces. The patient underwent total tumor resection with sufficient normal margins. The histological diagnosis was World Health Organization (WHO) grade I meningioma, with finger-like outward extensions through the dura mater and overlying skull, and infiltration among into the temporalis muscle fibers. Meningiomas may form a subcutaneous mass without intracranial growth.

Perfusion heterogeneity in breast tumors for assessment of angiogenesis

OBJECTIVES

The purpose of this study was to investigate the perfusion heterogeneity of malignant and benign breast tumors and assay their vascular architecture changes and molecular expression, thereby evaluating the relevance between imaging and histologic characteristics of angiogenesis.

METHODS

Real-time grayscale contrast-enhanced sonography was performed in 310 women with 317 breast tumors. The enhancement patterns and perfusion parameters for malignant and benign tumors were analyzed by contrast-enhanced sonography with microvascular imaging and quantitative time-intensity curve analysis. Structural characteristics were observed by light and electron microscopy. The microvessel density, vascular endothelial growth factor (VEGF) expression, and human kinase insert domain-containing receptor (KDR) expression for all tumors were assessed by immunohistochemical staining of CD31, KDR, and VEGF.

RESULTS

Surgical pathologic analysis showed 163 malignant and 154 benign tumors. Significant morphologic differences, including perfusion defects, vessel distortion, vessel dilatation, and heterogeneous enhancement, were observed between the malignant and benign groups (P < .05). The mean perfusion parameters (peak intensity, ascending slope, area under the curve, and wash-out time) were greater in the malignant tumors (P < .05). There were significant differences in the peak intensity, ascending slope, area under the curve, and wash-out time between peripheral and central regions of the malignant tumors (P < .05) but none in the benign tumors. Vessels had various morphologic and distributional characteristics in the peripheral and central regions of the malignant tumors. The microvessel density and VEGF and KDR expression were significantly higher in the malignant group (P < .05), especially in the peripheral regions.

CONCLUSIONS

Perfusion heterogeneity was closely associated with the tumor microvascular architecture and molecular expression. Perfusion features, especially regional morphologic and hemodynamic features, can provide valuable information for differentiating malignant from benign breast tumors.

Genomic sequencing of meningiomas identifies oncogenic SMO and AKT1 mutations

Meningiomas are the most common primary nervous system tumor. The tumor suppressor NF2 is disrupted in approximately half of meningiomas¹ but the complete spectrum of genetic changes remains undefined. We performed whole-genome or whole-exome sequencing on 17 meningiomas and focused sequencing on an additional 48 tumors to identify and validate somatic genetic alterations. Most meningiomas exhibited simple genomes, with fewer mutations, rearrangements, and copy-number alterations than reported in other adult tumors. However, several meningiomas harbored more complex patterns of copy-number changes and rearrangements including one tumor with chromothripsis. We confirmed focal NF2 inactivation in 43% of tumors and found alterations in epigenetic modifiers among an additional 8% of tumors. A subset of meningiomas lacking NF2 alterations harbored recurrent oncogenic mutations in AKT1 (E17K) and SMO (W535L) and exhibited immunohistochemical evidence of activation of their pathways. These mutations were present in therapeutically challenging tumors of the skull base and higher grade. These results begin to define the spectrum of genetic alterations in meningiomas and identify potential therapeutic targets.

The role of radiotherapy following gross-total resection of atypical meningiomas

OBJECT

Atypical (WHO Grade II) meningiomas comprise a heterogeneous group of tumors, with histopathology delineated under the guidance of the WHO and a spectrum of clinical outcomes. The role of postoperative radiotherapy for patients with atypical meningiomas who have undergone gross-total resection (GTR) remains unclear. In this paper, the authors sought to clarify this role by reviewing their experience over the past 2 decades.

METHODS

The authors retrospectively analyzed all patients at their institution who underwent GTR between 1992 and 2011 with a final histology demonstrating atypical meningioma. Information regarding patients, tumor characteristics, and postoperative adjuvant therapy was gleaned from medical records. Time to recurrence and overall survival were analyzed using univariate, multivariate, and Kaplan-Meier survival analyses.

RESULTS

Forty-five patients who met the inclusion criteria underwent GTR for atypical meningiomas. By a median follow-up of 44.1 months, 22% of atypical meningiomas had recurred. There was no recurrence in 12 (92%) of 13 patients who received postoperative radiotherapy or in 19 (59%) of 32 patients who did not undergo postoperative radiotherapy (p = 0.085), demonstrating a strong trend toward improved local control with postoperative radiotherapy. No other factors were significantly associated with recurrence in univariate or multivariate analyses.

CONCLUSIONS

This retrospective series supports the observation that postoperative radiotherapy likely results in lower recurrence rates of gross totally resected atypical meningiomas. Although a multicenter prospective trial will ultimately be needed to fully define the role of radiotherapy in managing gross totally resected atypical meningiomas, the authors' results contribute to a growing number of series that support routine postoperative radiotherapy as an adjuvant treatment for these lesions.

A microRNA expression signature predicts meningioma recurrence

The aberrant expression of microRNAs (miRNAs) is associated with a variety of diseases, including cancer. In our study, we examined the miRNA expression profile of meningiomas, which is a common type of benign intracranial tumor derived from the protective meninges membranes that surround the brain and spinal cord. To define a typical human meningioma miRNA profile, the expression of 200 miRNAs in a training sample set were screened using quantitative reverse transcription polymerase chain reaction analysis, and then significantly altered miRNAs were validated in a secondary independent sample set. Kaplan-Meier and univariate/multivariate Cox proportional hazard regression analyses were performed to assess whether miRNA expression could predict the recurrence of meningioma after tumor resection. After a two-phase selection and validation process, 14 miRNAs were found to exhibit significantly different expression profiles in meningioma samples compared to normal adjacent tissue (NAT) samples. Unsupervised clustering analysis indicated that the 14-miRNA profile differed between tumor and NAT samples. Downregulation of miR-29c-3p and miR-219-5p were found to be associated with advanced clinical stages of meningioma. Kaplan-Meier analysis showed that high expression of miR-190a and low expression of miR-29c-3p and miR-219-5p correlated significantly with higher recurrence rates in meningioma patients. Cox proportional hazard regression analysis revealed that miR-190a expression level is an important prognostic predictor that is independent of other clinicopathological factors. Our results suggest that the use of miRNA profiling has significant potential as an effective diagnostic and prognostic marker in defining the expression signature of meningiomas and in predicting postsurgical outcomes.

Proline-rich Akt substrate of 40kDa (PRAS40): a novel downstream target of PI3k/Akt signaling pathway

Modifications in signaling of the proline-rich Akt substrate of 40-kDa (PRAS40) pathway is implicated in type 2 diabetes and melanoma. PRAS40 is known for its ability to regulate the mammalian target of rapamycin complex 1 (mTORC1) kinase activity, possessing a key regulatory role at the cross point of signal transduction pathways activated by growth factor receptors. Recently it has been found that PRAS40 is regulated by its upstream phosphatidylinositol 3-kinase/Akt (PI3K/Akt) which is activated by many tyrosine kinase receptors growth factors including insulin-like growth factor 1. Also, PRAS40 functions downstream of mTORC1 and upstream from its effectors ribosomal protein S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1). Phosphorylation of PRAS40 by Akt and mTORC1 disrupts the binding between mTORC1 and PRAS40, and relieves the inhibitory constraint of PRAS40 on mTORC1 activity. This review summarizes the signaling regulating PRAS40 phosphorylation, as well as the dual function of PRAS40 as substrate and inhibitor of mTORC1 upon growth factor stimulation and under pathophysiological conditions.