Hyperdiploidy defines a distinct cytogenetic entity of meningiomas

The Evolving Classification of Meningiomas: Integration of Molecular Discoveries to Inform Patient Care

Meningioma classification and treatment have evolved over the past eight decades. Since Bailey, Cushing, and Eisenhart's description of meningiomas in the 1920s and 1930s, there have been continual advances in clinical stratification by histopathology, radiography and, most recently, molecular profiling, to improve prognostication and predict response to therapy. Precise and accurate classification is essential to optimizing management for patients with meningioma, which involves surveillance imaging, surgery, primary or adjuvant radiotherapy, and consideration for clinical trials. Currently, the World Health Organization (WHO) grade, extent of resection (EOR), and patient characteristics are used to guide management. While these have demonstrated reliability, a substantial number of seemingly benign lesions recur, suggesting opportunities for improvement of risk stratification. Furthermore, the role of adjuvant radiotherapy for grade 1 and 2 meningioma remains controversial. Over the last decade, numerous studies investigating the molecular drivers of clinical aggressiveness have been reported, with the identification of molecular markers that carry clinical implications as well as biomarkers of radiotherapy response. Here, we review the historical context of current practices, highlight recent molecular discoveries, and discuss the challenges of translating these findings into clinical practice.

Distinct clinical outcome of microcystic meningioma as a WHO grade 1 meningioma subtype

OBJECTIVE

To evaluate the clinicopathological characteristics, radiology, and long-term outcomes of microcystic meningiomas (MM) and compare it with other subtypes of meningiomas managed at a single neurosurgical center.

METHODS

A total of 87 consecutive patients who underwent surgical resection and were diagnosed as MM between 2005 and 2016 were enrolled for analysis. Clinicopathological, radiology, and prognostic information was collected and analyzed. Progression free survival (PFS) was compared with 659 patients with other subtypes of WHO grade 1 meningiomas and 167 patients with atypical meningiomas treated during the same period.

RESULTS

Fifty six females and 31 males with MM were analyzed. Peri-tumor brain edema was frequent on T2 WI (85%).12 patients (13.8%) experienced tumor progression during the mean follow-up of 101.66 ± 40.92 months. The median PFS was unavailable, and the 5, 10, and 15 year progression-free rates were 96.9%, 84.0%, and 73.9%, respectively. Univariate COX analysis demonstrated skull base location and higher Ki-67 index as significant negative prognostic factors for PFS (P < 0.05); multivariate analysis identified tumor location and Ki-67 index as independent factors (P < 0.01), as well. Of note, the PFS of MM was worse than other WHO grade 1 subtypes (P < 0.001), but better than atypical meningiomas (P < 0.001), and the PFS differences were retained even when the analysis was limited to the patients receiving GTR (P < 0.05).

CONCLUSION

The PFS of MM was worse than other WHO grade 1 subtypes and better than atypical meningiomas. Skull base location and higher Ki-67 index were independent negative prognostic factors in MM.

MicroRNA 200a as a histologically independent marker for meningioma recurrence: Results of a four microRNA panel analysis in meningiomas

INTRODUCTION

Meningiomas are mostly benign neoplasms of the central nervous system. Nevertheless there are recurrences in about 20% after surgical resection. Previous studies could reveal several predictors of meningioma recurrence. Tumor progression often is associated with a specific pattern of chromosome losses. Our study investigated the potential function of selected microRNAs as markers of tumor progression.

METHODS

By real-time polymerase chain reaction the expressions of microRNA 21-3p, 34a-3p, 200a-3p, and 409-3p were analyzed in solid tumor and in blood samples of 51 meningioma patients as well as in blood samples of 20 healthy individuals. Additionally, aberrations of parts of chromosomes 1, 14, 18, and 22 were analyzed by FISH. Tumor and blood samples were statistically analyzed, using Spearman's rank correlation coefficient as well as Mann-Whitney U- and Kruskal-Wallis-Test.

RESULTS

MicroRNA 200a showed significantly lower expressions in recurrent meningiomas than in newly diagnosed ones. MicroRNA 409 in meningiomas was correlated significantly with tumor volume and showed a significant negative correlation with patient age. Significance was found between the expression patterns of microRNAs 34a and 200a with the respective aberrations of chromosome 1p and the microRNA 409 with aberration of chromosome 14. In the male cohort the expression of microRNA 200a in blood was significantly upregulated in patients compared to healthy volunteers. By our research the function of microRNA 200a was proved to detect meningioma patients by liquid biopsy.

CONCLUSION

We detected microRNA 200a as a new biomarker to indicate meningioma recurrences. Future transferability to blood could be important for patient follow-up.

Fluorescence image-guided resection of intracranial meningioma: an experimental in vivo study on nude mice

INTRODUCTION

The use of photodynamic agents in malignant cranial tumor surgery is quite common. For example five-aminolevulinic acid (5-ALA)-induced porphyrins in malignant gliomas are potent photosensitizers. Until today there is no comparable selective fluorescent substance available for meningiomas. Nevertheless, there is a demand for intraoperative fluorescent identification of e.g. invasive skull base meningiomas to increase radicality. This study was established to investigate fluorescent image-guided resection with somatostatin receptor labelled fluorescence dye for intracranial meningioma in the nude mice.

METHODS

Primary meningioma cell culture samples were stereotactically implanted subdural into 20 nude mice. 90 days after inoculation of the cells, a cranial MRI with contrast agent revealed tumor growth. After detection of tumor mass in MRI, FAM-TOC5,6-Carboxyfluoresceine-Tyr3-Octreotide was injected intravenously and tumor mass was hereafter resected under visualization via fluorescence microscope and endoscope. After attempted total resection, animal were sacrificed brain slices were obtained and histologically analysed to verify the resection extent.

RESULTS

In 18 mice tumor growth was detected in MRI after 90 days of inoculation. The tumor mass could be clearly identified with fluorescence microscope and endoscope after injecting FAM-TOC5,6-Carboxyfluoresceine-Tyr3-Octreotide. The tumor margins could be better visualized. After fluorescence-guided resection no remaining tumor could be identified in histological analysis.

CONCLUSIONS

This study describes for the first time the use of FAM-TOC5,6-Carboxyfluoresceine-Tyr3-Octreotide and demonstrates its value of fluorescent identification of meningioma cells in vivo. Furthermore, the authors established a new experimental animal model for fluorescence meningioma surgery.

Multiple Whole Chromosomal Gains Define Angiomatous Meningiomas and Are Absent From the Tumor Vasculature

Angiomatous meningioma is a variant with prominent vascularity that can mimic other highly vascularized tumors and present diagnostic challenges. Unlike most meningioma variants, where NF2 gene loss on chromosome 22 is the most common genetic abnormality, angiomatous meningiomas are unique in having multiple whole chromosome gains (polysomies). We analyzed 38 meningiomas, 9 angiomatous (including 2 atypical and 1 anaplastic), and 29 nonangiomatous meningiomas, using array comparative genomic hybridization (aCGH). Angiomatous meningiomas showed multiple chromosomal alterations including polysomies and copy neutral loss of heterozygosity in comparison to nonangiomatous variants. The most frequent gains were of chromosomes 5 and 20 (100% and 89% of cases, respectively); none showed chromosome 22 loss. Furthermore, using fluorescence in situ hybridization we show that the vasculature lacked chromosomal polysomy. While generally benign, we present 2 grade II and the first cytogenetically confirmed grade III angiomatous meningioma, demonstrating their potentially aggressive behavior. Thus, multiple polysomies define angiomatous meningioma and aCGH can distinguish this variant from nonangiomatous meningiomas and other histological mimics in diagnostically challenging cases. Furthermore, the prominent vasculature is not neoplastic and likely induced by angiogenic factors. Together, these findings suggest a distinct tumorigenic pathway in angiomatous meningiomas.

The Loss of 1p as a Reliable Marker of Progression in a Child with Aggressive Meningioma: A 16-Year Follow-Up Case Report

BACKGROUND

Here, we present the case of a 32-year-old female with a progressing history of meningioma for 16 years starting with an ethmoidal lesion in 2002. The initial tumor specimen of this patient showed a deletion of the short arm of chromosome 1 through a translocation between chromosomes 1 and 11 (t[1; 11]) as well as additional chromosomal aberrations, including partial or complete monosomy of chromosomes 2, 6, 7, 11, 13, and 22. These molecular characteristics were already known to be associated with an aggressive course of the disease, and the patient was, therefore, included in a strict follow-up regime. From 2003 to 2019, the patient suffered multiple relapses and consecutive tumor resections.

METHODS

Tumor specimen from 2017 was examined using a genome-wide methylation analysis as well as a whole-genome sequencing.

RESULTS

These analyses confirmed the findings of 2002 and proved genetic alteration in the meningioma to be very stable over the time. Yet SMO and AKT1 mutations, which have been described to be paradigmatic in frontobasal meningioma, could not be found.

CONCLUSIONS

Genetic characteristics seem to be very stable during progression of the disease. The loss of 1p represents to be a potential marker for the poor clinical course of our child meningioma. In 2019, our patient passed away due to the progress of her meningioma disease.

Deletions in the 17q chromosomal region and their influence on the clonal cytogenetic evolution of recurrent meningiomas

Objective

Meningiomas are among the most frequent intracranial tumors. Although the majority of meningiomas can be cured by surgical resection, up to 20% of the patients develop an aggressive clinical course with tumor recurrence or progressive disease.

Cytogenetically, meningiomas frequently harbour a normal karyotype or monosomy of chromosome 22 as the sole anomaly. However, progression of meningiomas is associated with a non-random pattern of secondary losses of the chromosomes and chromosomal regions 1p, 6, 10, 14, 18, and 19. There is evidence, that loss of chromosome 17 might be involved in the clonal cytogenetic evolution of recurrent meningiomas. The aim of this study was to determine the role of deletions in the 17q chromosomal region in patients with recurrent meningiomas.

Results

The authors retrospectively reviewed all patients that underwent repeated surgery for recurrent meningiomas between 1999 and 2015 at the Department of Neurosurgery of the Saarland University Hospital. Patients were included in this study if tumor samples from two or more different meningiomas were available.

A total of 7 patients underwent repeated surgery for recurrent meningiomas (4 males, 3 females, mean age: 45.4 years at the date of surgery) between 1999 and 2015. Collectively, 22 biopsies were analyzed with FISH (fluorescence-in-situ-hybridization) for the chromosomal region 17q23.3. In 20/22 (90.1%) specimens, the tumor samples harboured a significant deletion in the chromosomal region 17q (range: 10 to 63% of the cells). In 3/3 (100%) cases, deletion in the 17q chromosomal region was detectable in the primary tumor. In the tumor evolution, there was no steady in- or decrease in the percentage of this deletion.

Conclusion

Deletion in the 17q chromosomal region was present in the patients’ primary tumors as well as in late recurrences. Overall, a significant deletion in the 17q chromosomal region was detected in 90.1% of the tumors. Thus, the authors assume that deletion in the 17q chromosomal region displays rather an early event in meningioma progression. Accordingly, deletion in the 17q chromosomal region might clinically serve as a potential early marker for malignancy and a higher risk for recurrence in meningiomas.

Identification of shared genomic aberrations between angiomatous and microcystic meningiomas

Background

Angiomatous and microcytic meningiomas are classified as rare subtypes of grade I meningiomas by World Health Organization (WHO). They typically exhibit distinct histopathological features as indicated by their WHO titles; however, these angiomatous and microcystic features are often intermixed. Recently, angiomatous meningiomas were reported to show characteristic chromosomal polysomies unlike the other WHO grade I meningiomas. In the present study, we hypothesize that microcystic meningiomas share similar cytogenetic abnormalities with angiomatous meningioma.

Methods

We performed copy number analysis using single nucleotide polymorphism (SNP) arrays for three angiomatous and eight microcystic meningiomas. Of these, three angiomatous and three microcystic meningiomas were also analyzed by whole exome sequencing and RNA sequencing.

Results

We first analyzed three angiomatous and three microcystic meningiomas for which both frozen tissues and peripheral blood were accessible. Copy number analysis confirmed previously reported multiple polysomies in angiomatous meningiomas, which were entirely replicated in microcystic meningiomas when analyzed on different analytical platforms with five additional samples prepared from formalin-fixed paraffin-embedded tumors. Polysomy of chromosome 5 was found in all cases, along with chromosome 6, 12, 17, 18, and 20 in more than half of the cases including both angiomatous and microcystic meningiomas. Furthermore, next generation sequencing did not reveal any distinctive somatic point mutations or differences in gene expression characterizing either angiomatous or microcystic meningiomas, indicating a common genetic mechanism underlying tumorigenesis.

Conclusions

Angiomatous and microcystic meningiomas have substantially similar genetic profiles represented by the characteristic patterns of multiple polysomies originating from chromosome 5 amplification.

Fluorescence imaging of meningioma cells with somatostatin receptor ligands: an in vitro study

BACKGROUND

The use of five-aminolevulinic acid (5-ALA) in the staining of malignant glioma cells has significantly improved intraoperative radicality in the resection of gliomas in the last decade. Currently, there is no comparable selective fluorescent substance available for meningiomas. There is however a demand for intraoperative fluorescent identification of, e.g., invasive skull base meningiomas to help improve safe radical resection. Meningiomas show high expression of the somatostatin receptor type 2, offering the possibility of receptor-targeted imaging. The authors used a somatostatin receptor-labeled fluorescence dye in the identification of meningiomas in vitro. The aim of this study was to evaluate the possibility of selective identification of meningioma cells with fluorescent techniques.

METHODS

Twenty-four primary human meningioma cell cultures were analyzed. The tumor cells were incubated with FAM-TOC (5,6-Carboxyfluoresceine-Tyr3-Octreotide). As a negative control, four human dura tissues were cultured as well as a mixed cell culture in vitro and incubated with the same somatostatin receptor-labeled fluorescence substance. After incubation, fluorescence signal and intensity in all cell cultures were analyzed at three different time points using a fluorescence microscope with 488 nm epi-illumination.

RESULTS

Sixteen WHO I, six WHO II, two WHO III meningioma primary cell cultures, and four dura cell cultures were analyzed. Fluorescence was detected in all meningioma cell cultures (22 cell culture stained strongly, 2 cell cultures moderately) directly after incubation up until 4 h later. There were no differences in the quality and quantity of fluorescence signal between the various meningioma grades. The fluorescence signal persisted unchanged during the analyzed period. In the negative control, dura cell cultures remained unstained.

CONCLUSIONS

This study demonstrates the use of FAM-TOC in the selective fluorescent identification of meningioma cells in vitro. Further evaluation of the chemical kinetics of the applied somatostatin receptor ligand and fluorescence dye is warranted. As a next step, an experimental animal model is needed to evaluate these promising results in vivo.

Genetic/molecular alterations of meningiomas and the signaling pathways targeted

Meningiomas are usually considered to be benign central nervous system tumors; however, they show heterogenous clinical, histolopathological and cytogenetic features associated with a variable outcome. In recent years important advances have been achieved in the identification of the genetic/molecular alterations of meningiomas and the signaling pathways involved. Thus, monosomy 22, which is often associated with mutations of the NF2 gene, has emerged as the most frequent alteration of meningiomas; in addition, several other genes (e.g., AKT1, KLF4, TRAF7, SMO) and chromosomes have been found to be recurrently altered often in association with more complex karyotypes and involvement of multiple signaling pathways. Here we review the current knowledge about the most relevant genes involved and the signaling pathways targeted by such alterations. In addition, we summarize those proposals that have been made so far for classification and prognostic stratification of meningiomas based on their genetic/genomic features.

Angiomatous meningiomas have a distinct genetic profile with multiple chromosomal polysomies including polysomy of chromosome 5

Meningiomas are a diverse group of tumors with a broad spectrum of histologic features. There are over 12 variants of meningioma, whose genetic features are just beginning to be described. Angiomatous meningioma is a World Health Organization (WHO) meningioma variant with a predominance of blood vessels. They are uncommon and confirming the histopathologic classification can be challenging. Given a lack of biomarkers that define the angiomatous subtype and limited understanding of the genetic changes underlying its tumorigenesis, we compared the genomic characteristics of angiomatous meningioma to more common meningioma subtypes. While typical grade I meningiomas demonstrate monosomy of chromosome 22 or lack copy number aberrations, 13 of 14 cases of angiomatous meningioma demonstrated a distinct copy number profile--polysomies of at least one chromosome, but often of many, especially in chromosomes 5, 13, and 20. WHO grade II atypical meningiomas with angiomatous features have both polysomies and genetic aberrations characteristic of other atypical meningiomas. Sequencing of over 560 cancer-relevant genes in 16 cases of angiomatous meningioma showed that these tumors lack common mutations found in other variants of meningioma. Our study demonstrates that angiomatous meningiomas have distinct genomic features that may be clinically useful for their diagnosis.

Molecular biological determinations of meningioma progression and recurrence

Meningiomas are tumors that arise from the coverings of the brain or spinal cord. 5% of the cases turn into malignant forms with aggressive clinical behavior and increased risk of tumor recurrence. One hundred and five patients with meningiomas were operated by open surgery. To investigate predictors of meningioma recurrence in total 124 samples of 105 patients were investigated by iFISH. Dual-probe hybridization was performed to access chromosomal alterations of chromosomes 1p-, 9p- and 22q. Additionally, methylation of TIMP3 and p16 was analyzed with MS-PCR. Of the 105 investigated tumors 59.1% (62/105) were WHO grade I, 33.3% (35/105) were WHO grade II and 7.7% (8/105) were anaplastic meningiomas (grade III), respectively. The histopathological data correlates with the recurrence rate of the investigated meningiomas. Hypermethylation of TIMP3 was detected in 13.3% of all meningiomas: 10.9% in WHO grade I meningiomas, 25.0% in grade II and 14.3% in grade III meningiomas, respectively. No correlation of TIMP3 hypermethylation with tumor recurrence or WHO grade (p = 0.2) was observed. Interestingly, deletion of 1p36 emerged as a significant predictor of shorter overall survival (log rank test, p<0.001), whereas TIMP3 promoter methylation had no significant effect on overall survival (log rank test, p = 0.799). The results of the current study support the finding that the deletion of chromosome 1p is an independent marker of meningioma recurrence and progression (p = 0.0097). Therefore the measurement of genetic aberrations in meningiomas allows in a combined histological approach a more precise assessment of the prognosis of meningiomas than histopathology alone.

Establishment of a molecular cytogenetic analysis for native tumor tissue of meningiomas-suitable for clinical application

Background

Meningiomas are mostly benign tumors which arise from the meninges. They are among the cytogenetically best-studied solid tumors, mostly displaying a normal karyotype or, as a typical primary aberration, monosomy of chromosome 22. Further secondary chromosomal aberrations, especially the deletion of chromosome 1p, are correlated with increasing biological aggressiveness up to malignancy. These data are derived from the cytogenetical characterization of 661 meningiomas, from which the genetic progression score (GPS) has been developed. Due to the high expenditure of time and the expert knowledge for the cytogenetical characterization, the aim of this work was to establish an equally reliable yet more rapid clinical diagnosis based on fluorescence in situ hybridization (FISH) on meningiomas. Thus a comparison between the native tumor tissue and the primary culture of the same tumor was done in order to determine the most efficient method for a molecular cytogenetic characterization. The diagnostic procedure has to deliver fast and robust results, since they must enable the attending physician to plan the appropriate follow-up regimens for the patients. All in all, preparations of native tumor tissue as well as preparations of cell culture of 22 meningiomas were tested with FISH for aberrations concerning the prognostically relevant chromosome regions 1p and 9p, and the chromosomes 10, 14, 18 and 22 in comparison with the particular karyotypes revealed by conventional karyotyping using G-banding.

Results

The FISH examinations between native and cultured cells showed an accordance of 93.4%. The comparison of FISH data and karyotyping presented accordance to the greatest possible extent concerning the chromosomes 14, 18 and 22, but to detect the progression associated losses of 1p and 9p FISH is the most sensitive method.

Conclusions

The raised data reveal that both methods can be used for a significant analysis of chromosome aberrations on meningiomas. As a result of that the complex primary culture could also be avoided. Therefore a clinical diagnosis based on FISH on meningiomas is at hand for the assignment of patients to a suitable follow-up regimen.

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.

Delineation of commonly deleted chromosomal regions in meningiomas by high-density single nucleotide polymorphism genotyping arrays

Despite recent advances in the identification of the cytogenetic profiles of meningiomas, a significant group of tumors still show normal karyotypes or few chromosomal changes. The authors analyzed the cytogenetic profile of 50 meningiomas using fluorescence in situ hybridization and high-density (500 K) single nucleotide polymorphism (SNP) arrays. Our results confirm that del(22q) (52%) and del(1p) (16%) (common deleted regions: 22q11.21-22q13.3. and 1p31.2-p36.33) are the most frequent alterations. Additionally, recurrent monosomy 14 (8%), del(6q) (10%), del(7p) (10%), and del(19q) (4%) were observed, while copy number patterns consistent with recurrent chromosomal gains, gene amplification, and copy number neutral loss of heterozygosity (cnLOH) were either absent or rare. Based on their overall SNP profiles, meningiomas could be classified into: (i) diploid cases, (ii) meningiomas with a single chromosomal change [e.g., monosomy 22/del(22q)] and (iii) tumors with ≥2 altered chromosomes. In summary, our results confirm and extend on previous observations showing that the most recurrent chromosomal abnormalities in meningiomas correspond to chromosome losses localized in chromosomes 1, 22 and less frequently in chromosomes 6, 7, 14, and 19, while chromosomal gains and cnLOH are restricted to a small proportion of cases. Finally, a set of cancer-associated candidate genes associated with the TP53, MYC, CASP3, HDAC1, and TERT signaling pathways was identified, in cases with coexisting monosomy 14 and del(1p).

Correspondence of tumor localization with tumor recurrence and cytogenetic progression in meningiomas

OBJECTIVE

Meningiomas are mostly benign tumors that originate from the coverings of the brain and spinal cord. Cytogenetically, they reveal a normal karyotype or, typically, monosomy of chromosome 22. Progression of meningiomas is associated with a non-random pattern of secondary losses of other autosomes. Deletion of the short arm of one chromosome 1 is a decisive step to anaplastic growth in meningiomas.

METHODS

Statistical analyses were performed for the karyotypes of 661 meningiomas with respect to localization, progression, and recurrence of the tumor. A mathematical mixture model estimates typical pathogenetic routes in terms of the accumulation of somatic chromosome changes in tumor cells. The model generates a genetic progression score (GPS) that estimates the prognosis as related to the cytogenetic properties of a given tumor.

RESULTS

In 53 patients, one or several recurrences were documented over the period of observation. This corresponds to a total rate of recurrence of 8.0% after macroscopically complete tumor extirpation. Higher GPS values were shown to be strongly correlated with tumor recurrence (P = 2.9 x 10(-7)). High-risk tumors, both in terms of histology and cytogenetics, are localized much more frequently at the brain surface than at the cranial base (P = 1.2 x 10(-5) for World Health Organization grade and P = 3.3 x 10(-12) for GPS categorization).

CONCLUSION

The tendency of cranial base meningiomas to recur seems to depend on surgical rather than biological reasons. As a quantitative measure, the GPS allows for a more precise assessment of the prognosis of meningiomas than the established categorical cytogenetic markers.