Epigenetic changes underlie the aggressiveness of histologically benign meningiomas that recur

Update on the Diagnosis and Management of Meningiomas

This series of five articles (one original article and four reviews) focuses on the most recent and interesting research studies on the biomolecular and radiological diagnosis and the surgical and medical management of meningiomas [...].

Dissecting Stemness in Aggressive Intracranial Meningiomas: Prognostic Role of SOX2 Expression

Meningiomas are mostly benign tumors that, at times, can behave aggressively, displaying recurrence despite gross-total resection (GTR) and progression to overt malignancy. Such cases represent a clinical challenge, particularly because they are difficult to recognize at first diagnosis. SOX2 (Sex-determining region Y-box2) is a transcription factor with a key role in stem cell maintenance and has been associated with tumorigenesis in a variety of cancers. The purpose of the present work was to dissect the role of SOX2 in predicting the aggressiveness of meningioma. We analyzed progressive/recurrent WHO grade 1−2 meningiomas and WHO grade 3 meningiomas; as controls, non-recurring WHO grade 1 and grade 2 meningioma patients were enrolled. SOX2 expression was evaluated using both immunohistochemistry (IHC) and RT-PCR. The final analysis included 87 patients. IHC was able to reliably assess SOX2 expression, as shown by the good correlation with mRNA levels (Spearman R = 0.0398, p = 0.001, AUC 0.87). SOX2 expression was an intrinsic characteristic of any single tumor and did not change following recurrence or progression. Importantly, SOX2 expression at first surgery was strongly related to meningioma clinical behavior, histological grade and risk of recurrence. Finally, survival data suggest a prognostic role of SOX2 expression in the whole series, both for overall and for recurrence-free survival (p < 0.0001 and p = 0.0001, respectively). Thus, SOX2 assessment could be of great help to clinicians in informing adjuvant treatments during follow-up.

Matched Paired Primary and Recurrent Meningiomas Points to Cell-Death Program Contributions to Genomic and Epigenomic Instability along Tumor Progression

Meningioma (MN) is an important cause of disability, and predictive tools for estimating the risk of recurrence are still scarce. The need for objective and cost-effective techniques addressed to this purpose is well known. In this study, we present methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) as a friendly method for deepening the understanding of the mechanisms underlying meningioma progression. A large follow-up allowed us to obtain 50 samples, which included the primary tumor of 20 patients in which half of them are suffering one recurrence and the other half are suffering more than one. We histologically characterized the samples and performed MS-MLPA assays validated by FISH to assess their copy number alterations (CNA) and epigenetic status. Interestingly, we determined the increase in tumor instability with higher values of CNA during the progression accompanied by an increase in epigenetic damage. We also found a loss of HIC1 and the hypermethylation of CDKN2B and PTEN as independent prognostic markers. Comparison between grade 1 and higher primary MN's self-evolution pointed to a central role of GSTP1 in the first stages of the disease. Finally, a high rate of alterations in genes that are related to apoptosis and autophagy, such as DAPK1, PARK2, BCL2, FHIT, or VHL, underlines an important influence on cell-death programs through different pathways.

The integrated multiomic diagnosis of sporadic meningiomas: a review of its clinical implications

Introduction

Meningiomas are generally considered “benign,” however, these tumors can demonstrate variability in behavior and a surprising aggressiveness with elevated rates of recurrence. The advancement of next-generation molecular technologies have led to the understanding of the genomic and epigenomic landscape of meningiomas and more recent correlations with clinical characteristics and behavior.

Methods

Based on a thorough review of recent peer-reviewed publications (PubMed) and edited texts, we provide a molecular overview of meningiomas with a focus on relevant clinical implications.

Results

The identification of specific somatic driver mutations has led to the classification of several major genomic subgroups, which account for more than 80% of sporadic meningiomas, and can be distinguished using noninvasive clinical variables to help guide management decisions. Other somatic genomic modifications, including non-coding alterations and copy number variations, have also been correlated with tumor characteristics. Furthermore, epigenomic modifications in meningiomas have recently been described, with DNA methylation being the most widely studied and potentially most clinically relevant. Based on these molecular insights, several clinical trials are currently underway in an effort to establish effective medical therapeutic options for meningioma.

Conclusion

As we enhance our multiomic understanding of meningiomas, our ability to care for patients with these tumors will continue to improve. Further biological insights will lead to additional progress in precision medicine for meningiomas.

Genomics, Epigenetics, and Hearing Loss in Neurofibromatosis Type 2

OBJECTIVES

In this review, we discuss current knowledge about the genetics and epigenetics of vestibular schwannoma (VS) in relation to hearing loss. A multistep and sequential genetic algorithm suitable for the identification of Neurofibromatosis Type 2 (NF2) constitutional and somatic mutations is discussed.

DATA SOURCES, STUDY SELECTION

A review was performed of the English literature from 1990 to 2019 using PubMed regarding genetics and epigenetics of vestibular schwannoma and NF2.

CONCLUSION

NF2 is a genetic disorder characterized by NF2 mutations that affect the function of a tumor suppressor called merlin. In particular, individuals with NF2 develop bilateral VS that can lead to hearing loss and even deafness. Recent advances in genetic and epigenetic studies have improved our understanding of the genotype-phenotype relationships that affect hearing in NF2 patients. Specific constitutional NF2 mutations including particular truncating, deletion, and missense mutations have been associated with poorer hearing outcomes and more severe clinical manifestations. Epigenetic events, such as DNA methylation and histone modifications, also contribute to the development and progression of hearing loss in NF2 patients. Furthermore, the accumulation of multiple NF2 and non-NF2 genetic and epigenetic abnormalities at the level of the tumor may contribute to worse hearing outcomes. Understanding genetic and epigenetic signatures in individual NF2 patients and particularly in each VS will allow us to develop novel gene therapies and precision medicine algorithms to preserve hearing in NF2 individuals.

Identification of a Novel BRCA1 Alteration in Recurrent Melanocytoma Resulting in Increased Proliferation

Primary meningeal melanocytomas are rare tumors of the central nervous system. Although they are considered benign neoplasms, some reports describe recurrent rates up to 45%. Little is known about their genetic and epigenetic landscape because of their infrequency. Even less has been described about markers with prognostic value. Here we describe a patient who developed a primary meningeal melanocytoma, suffered 3 recurrences in a period of 6 years and died of the tumor. The genetic and epigenetic changes explored confirmed GNAQ mutation as an initiating event. We found an epigenetic alteration of GSTP1, a feature that has recently been described in meningiomas, from the beginning of the disease. In addition, there was loss of heterozygosity in BRCA1 beginning in the second recurrence that was linked to an increase in the proliferation index; this suggested a progression pathway similar to the one described in uveal melanomas. These findings underscore the necessity of further research focused on these tumors.

Is DNA Methylation a Ray of Sunshine in Predicting Meningioma Prognosis?

Meningioma is the most common intracranial tumor, and recent studies have drawn attention to the importance of further research on malignant meningioma. According to the World Health Organization (WHO) grading, meningioma is classified into 15 subtypes with three grades of malignancy. However, due to a lack of descriptions of molecular subtypes, genetic mutations, or other features, there were deficiencies in the WHO classification. The DNA methylation-based meningioma classification published in 2017 used DNA copy number analysis, mutation profiling, and RNA sequencing to distinguish six clinically relevant methylation classes, which contributed to a better prediction of tumor recurrence and prognosis. Further studies indicated that gene variation and gene mutations, such as those in neurofibromin 2 (NF2) and BRCA1, were related to the high WHO grade, malignant invasion, and recurrence. Among the mutant genes described above, some have been associated with differential DNA methylation. Herein, we searched for articles published in PubMed and Web of Science from January 2000 to May 2020 by entering the keywords “meningioma,” “methylation,” and “gene mutation,” and found a number of published studies that analyzed DNA methylation in meningiomas. In this review, we summarize the key findings of recent studies on methylation status and genetic mutations of meningioma and discuss the current deficits of the WHO grading. We also propose that a methylation-based meningioma classification could provide clues in the assessment of individual risk of meningioma recurrence, which is associated with clinical benefits for patients.

Somatic copy number alterations are associated with EGFR amplification and shortened survival in patients with primary glioblastoma

Glioblastoma (GBM) is the most common malignant primary tumor of the central nervous system. With no effective therapy, the prognosis for patients is terrible poor. It is highly heterogeneous and EGFR amplification is its most frequent molecular alteration.

In this light, we aimed to examine the genetic heterogeneity of GBM and to correlate it with the clinical characteristics of the patients. For that purpose, we analyzed the status of EGFR and the somatic copy number alterations (CNAs) of a set of tumor suppressor genes and oncogenes.

Thus, we found GBMs with high level of EGFR amplification, low level and with no EGFR amplification. Highly amplified tumors showed histological features of aggressiveness. Interestingly, accumulation of CNAs, as a measure of tumor mutational burden, was frequent and significantly associated to shortened survival. EGFR-amplified GBMs displayed both a higher number of concrete CNAs and a higher global tumor mutational burden than their no EGFR-amplified counterparts. In addition to genetic changes previously described in GBM, we found PARK2 and LARGE1 CNAs associated to EGFR amplification. The set of genes analyzed allowed us to explore relevant signaling pathways on GBM. Both PARK2 and LARGE1 are related to receptor tyrosine kinase/PI3K/PTEN/AKT/mTOR-signaling pathway. Finally, we found an association between the molecular pathways altered, EGFR amplification and a poor outcome.

Our results underline the potential interest of categorizing GBM according to their EGFR amplification level and the usefulness of assessing the tumor mutational burden. These approaches would open new knowledge possibilities related to GBM biology and therapy.