Loss-of-function mutations in SMARCE1 cause an inherited disorder of multiple spinal meningiomas

Evolving concepts in meningioma management in the era of genomics

Meningioma is the most common type of primary brain tumor. Surgical resection followed by surveillance is the first-line treatment for the majority of symptomatic meningiomas; however, recent advances in molecular sequencing, DNA methylation, proteomics, and single-cell sequencing provide insights into further characterizing this heterogeneous group of tumors with a wide range of prognoses. A subset of these tumors are highly aggressive and cause severe morbidity and mortality. Therefore, identifying those individuals with a poor prognosis and intervening are critical. This review aims to help readers interpret the molecular profiling of meningiomas to identify patients with worse prognoses and guide the management and strategy for surveillance.

Update on Cancer Predisposition Syndromes and Surveillance Guidelines for Childhood Brain Tumors

Tumors of the central nervous system (CNS) comprise the second most common group of neoplasms in childhood. The incidence of germline predisposition among children with brain tumors continues to grow as our knowledge on disease etiology increases. Some children with brain tumors may present with nonmalignant phenotypic features of specific syndromes (e.g., nevoid basal cell carcinoma syndrome, neurofibromatosis type 1 and type 2, DICER1 syndrome, and constitutional mismatch-repair deficiency), while others may present with a strong family history of cancer (e.g., Li-Fraumeni syndrome) or with a rare tumor commonly found in the context of germline predisposition (e.g., rhabdoid tumor predisposition syndrome). Approximately 50% of patients with a brain tumor may be the first in a family identified to have a predisposition. The past decade has witnessed a rapid expansion in our molecular understanding of CNS tumors. A significant proportion of CNS tumors are now well characterized and known to harbor specific genetic changes that can be found in the germline. Additional novel predisposition syndromes are also being described. Identification of these germline syndromes in individual patients has not only enabled cascade testing of family members and early tumor surveillance but also increasingly affected cancer management in those patients. Therefore, the AACR Cancer Predisposition Working Group chose to highlight these advances in CNS tumor predisposition and summarize and/or generate surveillance recommendations for established and more recently emerging pediatric brain tumor predisposition syndromes.

Context-specific functions of chromatin remodellers in development and disease

Chromatin remodellers were once thought to be highly redundant and nonspecific in their actions. However, recent human genetic studies demonstrate remarkable biological specificity and dosage sensitivity of the thirty-two adenosine triphosphate (ATP)-dependent chromatin remodellers encoded in the human genome. Mutations in remodellers produce many human developmental disorders and cancers, motivating efforts to investigate their distinct functions in biologically relevant settings. Exquisitely specific biological functions seem to be an emergent property in mammals, and in many cases are based on the combinatorial assembly of subunits and the generation of stable, composite surfaces. Critical interactions between remodelling complex subunits, the nucleosome and other transcriptional regulators are now being defined from structural and biochemical studies. In addition, in vivo analyses of remodellers at relevant genetic loci have provided minute-by-minute insights into their dynamics. These studies are proposing new models for the determinants of remodeller localization and function on chromatin.

Spinal Meningiomas: A Comprehensive Review and Update on Advancements in Molecular Characterization, Diagnostics, Surgical Approach and Technology, and Alternative Therapies

Spinal meningiomas are the most common intradural, extramedullary tumor in adults, yet the least common entity when accounting for all meningiomas spanning the neuraxis. While traditionally considered a benign recapitulation of their intracranial counterpart, a paucity of knowledge exists regarding the differences between meningiomas arising from these two anatomic compartments in terms of histopathologic subtypes, molecular tumor biology, surgical principles, long-term functional outcomes, and recurrence rates. To date, advancements at the bench have largely been made for intracranial meningiomas, including the discovery of novel gene targets, DNA methylation profiles, integrated diagnoses, and alternative systemic therapies, with few exceptions reserved for spinal pathology. Likewise, evolving clinical research offers significant updates to our understanding of guiding surgical principles, intraoperative technology, and perioperative patient management for intracranial meningiomas. Nonetheless, spinal meningiomas are predominantly relegated to studies considering non-specific intradural extramedullary spinal tumors of all histopathologic types. The aim of this review is to comprehensively report updates in both basic science and clinical research regarding intraspinal meningiomas and to provide illustrative case examples thereof, thereby lending a better understanding of this heterogenous class of central nervous system tumors.

Translational Aspects of Epithelioid Sarcoma: Current Consensus

Epithelioid sarcoma (EpS) is an ultra-rare malignant soft-tissue cancer mostly affecting adolescents and young adults. EpS often exhibits an unfavorable clinical course with fatal outcome in ∼50% of cases despite aggressive multimodal therapies combining surgery, chemotherapy, and irradiation. EpS is traditionally classified in a more common, less aggressive distal (classic) type and a rarer aggressive proximal type. Both subtypes are characterized by a loss of nuclear INI1 expression, most often following homozygous deletion of its encoding gene, SMARCB1-a core subunit of the SWI/SNF chromatin remodeling complex. In 2020, the EZH2 inhibitor tazemetostat was the first targeted therapy approved for EpS, raising new hopes. Still, the vast majority of patients did not benefit from this drug or relapsed rapidly. Further, other recent therapeutic modalities, including immunotherapy, are only effective in a fraction of patients. Thus, novel strategies, specifically targeted to EpS, are urgently needed. To accelerate translational research on EpS and eventually boost the discovery and development of new diagnostic tools and therapeutic options, a vibrant translational research community has formed in past years and held two international EpS digital expert meetings in 2021 and 2023. This review summarizes our current understanding of EpS from the translational research perspective and points to innovative research directions to address the most pressing questions in the field, as defined by expert consensus and patient advocacy groups.

Mutation of the SWI/SNF complex component Smarce1 decreases nucleosome stability in embryonic stem cells and impairs differentiation

The SWI/SNF chromatin remodeling complex consists of more than ten component proteins that form a large protein complex of >1 MDa. The catalytic proteins Smarca4 or Smarca2 work in concert with the component proteins to form a chromatin platform suitable for transcriptional regulation. However, the mechanism by which each component protein works synergistically with the catalytic proteins remains largely unknown. Here, we report on the function of Smarce1, a component of the SWI/SNF complex, through the phenotypic analysis of homozygous mutant embryonic stem cells (ESCs). Disruption of Smarce1 induced the dissociation of other complex components from the SWI/SNF complex. Histone binding to DNA was loosened in homozygous mutant ESCs, indicating that disruption of Smarce1 decreased nucleosome stability. Sucrose gradient sedimentation analysis suggested that there was an ectopic genomic distribution of the SWI/SNF complex upon disruption of Smarce1, accounting for the misregulation of chromatin conformations. Unstable nucleosomes remained during ESC differentiation, impairing the heterochromatin formation that is characteristic of the differentiation process. These results suggest that Smarce1 guides the SWI/SNF complex to the appropriate genomic regions to generate chromatin structures adequate for transcriptional regulation.

Personalized Driver Gene Prediction Using Graph Convolutional Networks with Conditional Random Fields

Cancer is a complex and evolutionary disease mainly driven by the accumulation of genetic variations in genes. Identifying cancer driver genes is important. However, most related studies have focused on the population level. Cancer is a disease with high heterogeneity. Thus, the discovery of driver genes at the individual level is becoming more valuable but is a great challenge. Although there have been some computational methods proposed to tackle this challenge, few can cover all patient samples well, and there is still room for performance improvement. In this study, to identify individual-level driver genes more efficiently, we propose the PDGCN method. PDGCN integrates multiple types of data features, including mutation, expression, methylation, copy number data, and system-level gene features, along with network structural features extracted using Node2vec in order to construct a sample-gene interaction network. Prediction is performed using a graphical convolutional neural network model with a conditional random field layer, which is able to better combine the network structural features with biological attribute features. Experiments on the ACC (Adrenocortical Cancer) and KICH (Kidney Chromophobe) datasets from TCGA (The Cancer Genome Atlas) demonstrated that the method performs better compared to other similar methods. It can identify not only frequently mutated driver genes, but also rare candidate driver genes and novel biomarker genes. The results of the survival and enrichment analyses of these detected genes demonstrate that the method can identify important driver genes at the individual level.

Lumbar clear cell meningioma mimicking schwannoma 7 years after resection of the same type of intracranial tumor: a case report

BACKGROUND

Meningioma is the second most common intradural extramedullary tumor, following schwannoma. Meningioma is primarily categorized as benign World Health Organization grade 1, but clear cell meningioma is grade 2 of the intermediate malignant category. Clear cell meningiomas are rare, accounting for less than 1% of all meningioma tumors. There is no previous report of multiple intraspinal clear cell meningiomas without dural attachment.

CASE PRESENTATION

A 27-year-old Asian male patient presented with lower right extremity pain, and had undergone tumor resection for intracranial clear cell meningioma 7 years previously, with re-resection and radiotherapy for local tumor recurrence at our hospital's department of neurosurgery being carried out 4 years previously. No recurrence was observed since then. Preoperative lumbar magnetic resonance imaging showed two tumors at the L1 and L4 levels, both mimicking schwannoma with well-defined margins, no dural tail sign and homogeneous internal contrast. Intraoperative findings on tumor resection showed two tumors contiguous with the right L2 and L5 roots, which were not attached to the dura mater, similar to a schwannoma. After gross total resection, the postoperative pathology revealed no nuclear SMARCE1 antibody staining. The patient was diagnosed with clear cell meningioma. The patient's postoperative course went well, with no symptoms of nerve dropout and no recurrence 2 years after surgery. In this case, both lumbar lesions were well demarcated and spherical in shape, occurring with single roots. Tumor characteristics suggested a primary rather than a metastatic lesion. Clear cell meningioma is characterized by a SMARCE1 mutation and is different from other types of meningiomas.

CONCLUSION

To the best of our knowledge, this is the first report of multiple intraspinal clear cell meningiomas without dural attachment at the lumbar spine after resection of intracranial clear cell meningioma. We speculate that the two tumors were de novo lesions on the basis of the features of the tumors, although they were detected 7 years after the resection of intracranial clear cell meningioma.

A novel patient-derived meningioma spheroid model as a tool to study and treat epithelial-to-mesenchymal transition (EMT) in meningiomas

Meningiomas are the most common intracranial brain tumours. These tumours are heterogeneous and encompass a wide spectrum of clinical aggressivity. Treatment options are limited to surgery and radiotherapy and have a risk of post-operative morbidities and radiation neurotoxicity, reflecting the need for new therapies. Three-dimensional (3D) patient-derived cell culture models have been shown to closely recapitulate in vivo tumour biology, including microenvironmental interactions and have emerged as a robust tool for drug development. Here, we established a novel easy-to-use 3D patient-derived meningioma spheroid model using a scaffold-free approach. Patient-derived meningioma spheroids were characterised and compared to patient tissues and traditional monolayer cultures by histology, genomics, and transcriptomics studies. Patient-derived meningioma spheroids closely recapitulated morphological and molecular features of matched patient tissues, including patient histology, genomic alterations, and components of the immune microenvironment, such as a CD68 + and CD163 + positive macrophage cell population. Comprehensive transcriptomic profiling revealed an increase in epithelial-to-mesenchymal transition (EMT) in meningioma spheroids compared to traditional monolayer cultures, confirming this model as a tool to elucidate EMT in meningioma. Therefore, as proof of concept study, we developed a treatment strategy to target EMT in meningioma. We found that combination therapy using the MER tyrosine kinase (MERTK) inhibitor UNC2025 and the histone deacetylase (HDAC) inhibitor Trichostatin A (TSA) effectively decreased meningioma spheroid viability and proliferation. Furthermore, we demonstrated this combination therapy significantly increased the expression of the epithelial marker E-cadherin and had a repressive effect on WHO grade 2-derived spheroid invasion, which is suggestive of a partial reversal of EMT in meningioma spheroids.

A novel BRAF::PTPRN2 fusion in meningioma: a case report

Gene fusion events have been linked to oncogenesis in many cancers. However, gene fusions in meningioma are understudied compared to somatic mutations, chromosomal gains/losses, and epigenetic changes. Fusions involving B-raf proto-oncogene, serine/threonine kinase (BRAF) are subtypes of oncogenic BRAF genetic abnormalities that have been reported in certain cases of brain tumors, such as pilocytic astrocytomas. However, BRAF fusions have not been recognized in meningioma. We present the case of an adult female presenting with episodic partial seizures characterized by déjà vu, confusion, and cognitive changes. Brain imaging revealed a cavernous sinus and sphenoid wing mass and she underwent resection. Histopathology revealed a World Health Organization (WHO) grade 1 meningioma. Genetic profiling with next generation sequencing and microarray analysis revealed an in-frame BRAF::PTPRN2 fusion affecting the BRAF kinase domain as well as chromothripsis of chromosome 7q resulting in multiple segmental gains and losses including amplifications of cyclin dependent kinase 6 (CDK6), tyrosine protein-kinase Met (MET), and smoothened (SMO). Elevated pERK staining in tumor cells provided evidence of activated mitogen-activated protein kinase (MAPK) signaling. This report raises the possibility that gene fusion events may be involved in meningioma pathogenesis and warrant further investigation.

Super-enhancer hijacking drives ectopic expression of hedgehog pathway ligands in meningiomas

Hedgehog signaling mediates embryologic development of the central nervous system and other tissues and is frequently hijacked by neoplasia to facilitate uncontrolled cellular proliferation. Meningiomas, the most common primary brain tumor, exhibit Hedgehog signaling activation in 6.5% of cases, triggered by recurrent mutations in pathway mediators such as SMO. In this study, we find 35.6% of meningiomas that lack previously known drivers acquired various types of somatic structural variations affecting chromosomes 2q35 and 7q36.3. These cases exhibit ectopic expression of Hedgehog ligands, IHH and SHH, respectively, resulting in Hedgehog signaling activation. Recurrent tandem duplications involving IHH permit de novo chromatin interactions between super-enhancers within DIRC3 and a locus containing IHH. Our work expands the landscape of meningioma molecular drivers and demonstrates enhancer hijacking of Hedgehog ligands as a route to activate this pathway  in neoplasia.

Novel Advances in Treatment of Meningiomas: Prognostic and Therapeutic Implications

Meningiomas are the most frequent histotypes of tumors of the central nervous system. Their incidence is approximately 35% of all primary brain tumors. Although they have the status of benign lesions, meningiomas are often associated with a decreased quality of life due to focal neurological deficits that may be related. The optimal treatment is total resection. Histological grading is the most important prognostic factor. Recently, molecular alterations have been identified that are specifically related to particular phenotypes and, probably, are also responsible for grading, site, and prognostic trend. Meningiomas recur in 10-25% of cases. In these cases, and in patients with atypical or anaplastic meningiomas, the methods of approach are relatively insufficient. To date, data on the molecular biology, genetics, and epigenetics of meningiomas are insufficient. To achieve an optimal treatment strategy, it is necessary to identify the mechanisms that regulate tumor formation and progression. Combination therapies affecting multiple molecular targets are currently opening up and have significant promise as adjuvant therapeutic options. We review the most recent literature to identify studies investigating recent therapeutic treatments recently used for meningiomas.

The SWI/SNF Complex in Neural Crest Cell Development and Disease

While the neural crest cell population gives rise to an extraordinary array of derivatives, including elements of the craniofacial skeleton, skin pigmentation, and peripheral nervous system, it is today increasingly recognized that Schwann cell precursors are also multipotent. Two mammalian paralogs of the SWI/SNF (switch/sucrose nonfermentable) chromatin-remodeling complexes, BAF (Brg1-associated factors) and PBAF (polybromo-associated BAF), are critical for neural crest specification during normal mammalian development. There is increasing evidence that pathogenic variants in components of the BAF and PBAF complexes play central roles in the pathogenesis of neural crest-derived tumors. Transgenic mouse models demonstrate a temporal window early in development where pathogenic variants in Smarcb1 result in the formation of aggressive, poorly differentiated tumors, such as rhabdoid tumors. By contrast, later in development, homozygous inactivation of Smarcb1 requires additional pathogenic variants in tumor suppressor genes to drive the development of differentiated adult neoplasms derived from the neural crest, which have a comparatively good prognosis in humans.

The role of radiation therapy and systemic treatments in meningioma: The present and the future

Meningiomas are the most prevalent tumors of the central nervous system. Their standard treatment is surgery, which can be curative. Adjuvant radiotherapy treatment is reserved for newly diagnosed cases of grade II and grade III meningiomas in cases of recurrent disease or when surgery is not radical or feasible. However, around 20% of these patients cannot undergo further surgical and/or radiotherapy treatment. Systemic oncological therapy can find its place in this setting. Several tyrosine kinase inhibitors have been tested (gefitinib, erlotinib, sunitinib) with unsatisfactory or negative results. Bevacizumab has shown encouraging results in these settings of patients. Immunotherapy with immune checkpoint inhibitors has reported interesting results with modest objective response rates. Several ongoing studies are assessing different target therapies and multimodal therapies; the results are to be disclosed. Not only a better understanding of the molecular characteristics in meningiomas has allowed the gathering of more information regarding pathogenesis and prognosis, but in addition, the availability of new target therapy, immunotherapy, and biological drugs has widened the scope of potentially effective treatments in this patient population. The aim of this review was to explore the radiotherapy and systemic treatments of meningioma with an analysis of ongoing trials and future therapeutic perspectives.

Spinal Meningiomas: Diagnosis, Surgical Management, and Adjuvant Therapies

Meningiomas of the spinal canal are the most common intradural spinal canal tumors encountered in adults and account for 8% of all meningiomas. Patient presentation can vary considerably. Once diagnosed, these lesions are primarily treated surgically, but depending on location and pathological features, chemotherapy and radiosurgery may be required. Emerging modalities may represent adjuvant therapies. In this article, we review the current management of meningiomas of the spinal column.

Advances in the systemic therapy for recurrent meningiomas and the challenges ahead

INTRODUCTION

Meningiomas represent the most common primary neoplasms of the central nervous system (CNS). 20% present with atypical (WHO grade II) or malignant (grade III) meningiomas, which show aggressive biologic behavior and high recurrence. Although surgical resection and radiation therapy are the primary treatment options for these tumors, there is a subgroup of patients who do not respond well to or are poor candidates for these approaches, leading to the exploration of systemic therapies as an alternative.

AREAS COVERED

The literature on different therapeutic groups of systemic drugs for recurrent meningiomas is reviewed, with a focus on the different molecular targets. Past and current ongoing clinical trials are also discussed.

EXPERT OPINION

To date, there is no recognized treatment that has demonstrated a substantial increase in progression-free or overall survival rates. Nonetheless, therapies targeting anti-VEGF have exhibited more encouraging results in general. The examination of genomic and epigenomic traits of meningiomas, along with the integration of molecular markers into the latest WHO tumor grading system, has provided valuable insights. This has opened avenues for exploring numerous intracellular and extracellular pathways, as well as mutations, that have been targeted in ongoing clinical trials.

SMARCE1-related meningiomas: A clear example of cancer predisposing syndrome

We report the case of a 16-year-old girl presenting with spinal clear-cell multiple meningiomas (CCMs). In view of this presentation, we sequenced a bioinformatic panel of genes associated with susceptibility to meningioma, identifying a germline heterozygous variant inSMARCE1. Somatic DNA investigations in the CCM demonstrated the deletion of the wild-type allele (loss of heterozygosity, LOH), supporting the causative role of this variant. Family segregation study detected the SMARCE1 variant in the asymptomatic father and in the asymptomatic sister who, nevertheless, presents 2 spinal lesions. Germline heterozygous loss-of-function (LoF) variants in SMARCE1, encoding a protein of the chromatin-remodeling complex SWI/SNF, have been described in few familial cases of susceptibility to meningioma, in particular the CCM subtype. Our case confirms the role of NGS in investigating predisposing genes for meningiomas (multiple or recurrent), with specific regard to SMARCE1 in case of pediatric CCM. In addition to the age of onset, the presence of familial clustering or the coexistence of multiple synchronous meningiomas also supports the role of a genetic predisposition that deserves a molecular assessment. Additionally, given the incomplete penetrance, it is of great importance to follow a specific screening or follow-up program for symptomatic and asymptomatic carriers of pathogenic variants in SMARCE1.

Review of meningioma diagnosis and management

Meningiomas are the most common intracranial tumors in adult patients. Although the majority of meningiomas are diagnosed as benign, approximately 20% of cases are high-grade tumors that require significant clinical treatment. The gold standard for grading central nervous system tumors comes from the World Health Organization Classification of Tumors of the central nervous system. Treatment options also depend on the location, imaging, and histopathological features of the tumor. This review will cover diagnostic strategies for meningiomas, including 2021 updates to the World Health Organization's grading of meningiomas. Meningioma treatment plans are variable and highly dependent on tumor grading. This review will also update the reader on developments in the treatment of meningiomas, including surgery, radiation therapy and monoclonal antibody treatment.

The "extreme phenotype approach" applied to male breast cancer allows the identification of rare variants of ATR as potential breast cancer susceptibility alleles

In oncogenetics, some patients could be considered as "extreme phenotypes", such as those with very early onset presentation or multiple primary malignancies, unusually high numbers of cancers of the same spectrum or rare cancer types in the same parental branch. For these cases, a genetic predisposition is very likely, but classical candidate gene panel analyses often and frustratingly remains negative. In the framework of the EX2TRICAN project, exploring unresolved extreme cancer phenotypes, we applied exome sequencing on rare familial cases with male breast cancer, identifying a novel pathogenic variant of ATR (p.Leu1808*). ATR has already been suspected as being a predisposing gene to breast cancer in women. We next identified 3 additional ATR variants in a cohort of both male and female with early onset and familial breast cancers (c.7762-2A>C; c.2078+1G>A; c.1A>G). Further molecular and cellular investigations showed impacts on transcripts for variants affecting splicing sites and reduction of ATR expression and phosphorylation of the ATR substrate CHEK1. This work further demonstrates the interest of an extended genetic analysis such as exome sequencing to identify very rare variants that can play a role in cancer predisposition in extreme phenotype cancer cases unexplained by classical cancer gene panels testing.

Recent advances in the molecular prognostication of meningiomas

Meningiomas are the most common primary intracranial neoplasm. While traditionally viewed as benign, meningiomas are associated with significant patient morbidity, and certain meningioma subgroups display more aggressive and malignant behavior with higher rates of recurrence. Historically, the risk stratification of meningioma recurrence has been primarily associated with the World Health Organization histopathological grade and surgical extent of resection. However, a growing body of literature has highlighted the value of utilizing molecular characteristics to assess meningioma aggressiveness and recurrence risk. In this review, we discuss preclinical and clinical evidence surrounding the use of molecular classification schemes for meningioma prognostication. We also highlight how molecular data may inform meningioma treatment strategies and future directions.

Mother and daughter with a SMARCE1 mutation resulting in a cervical clear cell meningioma at an identical location: illustrative cases

BACKGROUND

A rare meningioma subtype is a clear cell (CC) meningioma, which can be associated with a SMARCE1 gene mutation. Manifestation of a CC meningioma in the cervical spine is unusual. In the current case, both mother and daughter present with a CC meningioma at an identical cervical location.

OBSERVATIONS

A 67-year-old patient with an intradural extramedullary mass at the level of C5 presented with progressive myelopathy. The mass was resected through a ventral approach by a two-level corpectomy with an expandable cage and instrumentation. The daughter of this patient appeared to have had an intradural extramedullary mass at C5 at the age of 20, which was resected through a posterior approach. Pathological investigation of both tumors revealed CC meningioma. Genetic testing of the daughter revealed a SMARCE1 mutation.

LESSONS

It is of major importance to consider a SMARCE1 mutation in elderly presenting with a CC meningioma, which is still uncommon in current practice. This could lead to timely diagnostics in the succeeding generation. Complete resection of a CC meningioma is important because of the high recurrence rate. Routine follow-up should therefore be performed in the postoperative period. An anterior approach should be considered for a ventral cervical CC meningioma.

A current review of spinal meningiomas: epidemiology, clinical presentation and management

PURPOSE

To provide an up-to-date review of the epidemiology, histopathology, molecular biology, and etiology of spinal meningiomas, as well as discuss the clinical presentation, clinical evaluation, and most recent treatment recommendations for these lesions.

METHODS

PubMed and Google Scholar search was performed for studies related to meningiomas of the spine. The terms "meningioma," "spinal meningioma," "spine meningioma," "meningioma of the spine," "benign spinal tumors," and "benign spine tumors," were used to identify relevant studies. All studies, including primary data papers, meta-analyses, systematic reviews, general reviews, case reports, and clinical trials were considered for review.

RESULTS

Eighty-four studies were identified in the review. There were 22 studies discussing adverse postoperative outcomes, 21 studies discussing tumor genetics, 19 studies discussing epidemiology and current literature, 9 studies discussing radiation modalities and impact on subsequent tumor development, 5 studies on characteristic imaging findings, 5 studies discussing hormone use/receptor status on tumor development, 2 discussing operative techniques and 1 discussing tumor identification.

CONCLUSION

Investigations into spinal meningiomas generally lag behind that of intracranial meningiomas. Recent advancements in the molecular profiling of spinal meningiomas has expanded our understanding of these tumors, increasing our appreciation for their heterogeneity. Continued investigation into the defining characteristics of different spinal meningiomas will aid in treatment planning and prognostication.

Preclinical Models of Meningioma

The management of clinically aggressive meningiomas remains challenging due to limited treatment options aside from surgical removal and radiotherapy. High recurrence rates and lack of effective systemic therapies contribute to the unfavorable prognosis of these patients. Accurate in vitro and in vivo models are critical for understanding meningioma pathogenesis and to identify and test novel therapeutics. In this chapter, we review cell models, genetically engineered mouse models, and xenograft mouse models, with special emphasis on the field of application. Finally, promising preclinical 3D models such as organotypic tumor slices and patient-derived tumor organoids are discussed.

Spinal Meningiomas

Spinal meningiomas are relatively rare, but account for a significant proportion of primary spinal tumors in adults. These meningiomas can be found anywhere along the spinal column and their diagnosis is often delayed due to their slow growth and the lack of significant neurological symptoms until they reach a critical size, at which point signs of spinal cord or nerve root compression generally manifest and progress. If left untreated, spinal meningiomas can cause severe neurological deficits including rendering patients paraplegic or tetraplegic. In this chapter we will review the clinical features of spinal meningiomas, their surgical management, and detail molecular features that differentiate them from intracranial meningiomas.

Current Knowledge on Spinal Meningiomas Epidemiology, Tumor Characteristics and Non-Surgical Treatment Options: A Systematic Review and Pooled Analysis (Part 1)

BACKGROUND

Spinal meningiomas are the most common primary intradural spinal tumors. Although they are a separate entity, a large portion of the knowledge on spinal meningiomas is based on findings in intracranial meningiomas. Therefore, a comprehensive review of all the literature on spinal meningiomas was performed.

METHODS

Electronic databases were searched for all studies on spinal meningiomas dating from 2000 and onward. Findings of matching studies were pooled to strengthen the current body of evidence.

RESULTS

A total of 104 studies were included. The majority of patients were female (72.83%), elderly (peak decade: seventh), and had a world health organization (WHO) grade 1 tumor (95.7%). Interestingly, the minority of pediatric patients had a male overrepresentation (62.0% vs. 27.17%) and higher-grade tumors (33.3% vs. 4.3%). Sensory and motor dysfunction and pain were the most common presenting symptoms. Despite a handful of studies reporting promising findings associated with the use of non-surgical treatment options, the literature still suffers from contradictory results and limitations of study designs.

CONCLUSIONS

Elderly females with WHO grade 1 tumors constituted the stereotypical type of patient. Compared to surgical alternatives, the evidence for the use of non-surgical treatments is still relatively weak.

Prognostic significance of telomerase reverse transcriptase promoter gen mutations in high grade meningiomas

Introduction: Mutations in the promoter region of telomerase reverse transcriptase occur frequently in meningiomas. Objective: To estimate the prognostic importance of telomerase reverse transcriptase mutations in Colombian patients with grades II and III meningioma. Materials and methods: This was a multicenter retrospective cohort study of patients diagnosed with refractory or recurrent WHO grades II and III meningiomas, recruited between 2011 and 2018, and treated with systemic therapy (sunitinib, everolimus ± octreotide, and bevacizumab). Mutation status of the telomerase reverse transcriptase promoter was established by PCR. Results: Forty patients were included, of which telomerase reverse transcriptase mutations were found in 21 (52.5%), being C228T and C250T the most frequent variants with 87.5 % and 14.3 %, respectively. These were more frequent among patients with anaplastic meningiomas (p=0.18), with more than 2 recurrences (p=0.04); and in patients with parasagittal region and anterior fossa lesions (p=0.05). Subjects characterized as having punctual mutations were more frequently administered with everolimus, sunitinib and bevacizumab drug series (p=0.06). Overall survival was 23.7 months (CI95% 13.1-34.2) and 43.4 months (CI95% 37.5-49.3; p=0.0001) between subjects with and without mutations, respectively. Multivariate analysis showed that the number of recurrences and the presence of telomerase reverse transcriptase mutations were tthe only variables that negatively affected overall survival. Conclusions: Mutations in telomerase reverse transcriptase allows the identification of high-risk patients and could be useful in the selection of the best medical treatment.

Molecular diagnosis and treatment of meningiomas: an expert consensus (2022)

ABSTRACT

Meningiomas are the most common primary intracranial neoplasm with diverse pathological types and complicated clinical manifestations. The fifth edition of the WHO Classification of Tumors of the Central Nervous System (WHO CNS5), published in 2021, introduces major changes that advance the role of molecular diagnostics in meningiomas. To follow the revision of WHO CNS5, this expert consensus statement was formed jointly by the Group of Neuro-Oncology, Society of Neurosurgery, Chinese Medical Association together with neuropathologists and evidence-based experts. The consensus provides reference points to integrate key biomarkers into stratification and clinical decision making for meningioma patients.

REGISTRATION

Practice guideline REgistration for transPAREncy (PREPARE), IPGRP-2022CN234.

Molecular determinants of outcomes in meningiomas

Meningiomas are the most common intracranial primary tumor in adults. Surgery is the predominant therapeutic modality for symptomatic meningiomas. Although the majority of meningiomas are benign, there exists a subset of meningiomas that are clinically aggressive. Recent advances in genetics and epigenetics have uncovered molecular alterations that drive tumor meningioma biology with prognostic and therapeutic implications. In this review, we will discuss the advances on molecular determinants of therapeutic response in meningiomas to date and discuss findings of targeted therapies in meningiomas.

Epigenetic dysregulation in meningiomas

Background

Meningiomas are the most common primary brain tumor. Though typically benign with a low mutational burden, tumors with benign histology may behave aggressively and there are no proven chemotherapies. Although DNA methylation patterns distinguish subgroups of meningiomas and have higher predictive value for tumor behavior than histologic classification, little is known about differences in DNA methylation between meningiomas and surrounding normal dura tissue.

Methods

Whole-exome sequencing and methylation array profiling were performed on 12 dura/meningioma pairs (11 WHO grade I and 1 WHO grade II). Single-nucleotide polymorphism (SNP) genotyping and methylation array profiling were performed on an additional 19 meningiomas (9 WHO grade I, 5 WHO grade II, 4 WHO grade III).

Results

Using multimodal studies of meningioma/dura pairs, we identified 4 distinct DNA methylation patterns. Diffuse DNA hypomethylation of malignant meningiomas readily facilitated their identification from lower-grade tumors by unsupervised clustering. All clusters and 12/12 meningioma-dura pairs exhibited hypomethylation of the gene promoters of a module associated with the craniofacial patterning transcription factor FOXC1 and its upstream lncRNA FOXCUT. Furthermore, we identified an epigenetic continuum of increasing hypermethylation of polycomb repressive complex target promoters with increasing histopathologic grade.

Conclusion

These findings support future investigations of the role of epigenetic dysregulation of FOXC1 and cranial patterning genes in meningioma formation as well as studies of the utility of polycomb inhibitors for the treatment of malignant meningiomas.

SMARCE1 deficiency generates a targetable mSWI/SNF dependency in clear cell meningioma

Mammalian SWI/SNF (mSWI/SNF) ATP-dependent chromatin remodeling complexes establish and maintain chromatin accessibility and gene expression, and are frequently perturbed in cancer. Clear cell meningioma (CCM), an aggressive tumor of the central nervous system, is uniformly driven by loss of SMARCE1, an integral subunit of the mSWI/SNF core. Here, we identify a structural role for SMARCE1 in selectively stabilizing the canonical BAF (cBAF) complex core-ATPase module interaction. In CCM, cBAF complexes fail to stabilize on chromatin, reducing enhancer accessibility, and residual core module components increase the formation of BRD9-containing non-canonical BAF (ncBAF) complexes. Combined attenuation of cBAF function and increased ncBAF complex activity generates the CCM-specific gene expression signature, which is distinct from that of NF2-mutated meningiomas. Importantly, SMARCE1-deficient cells exhibit heightened sensitivity to small-molecule inhibition of ncBAF complexes. These data inform the function of a previously elusive SWI/SNF subunit and suggest potential therapeutic approaches for intractable SMARCE1-deficient CCM tumors.

Genomic profiling of sporadic multiple meningiomas

BACKGROUND

Multiple meningiomas (MMs) rarely occur sporadically. It is unclear whether each individual tumor in a single patient behaves similarly. Moreover, the molecular mechanisms underlying the formation of sporadic MMs and clonal formation etiology of these tumors are poorly understood.

METHODS

Patients with spatially separated MMs without prior radiation exposure or a family history who underwent surgical resection of at least two meningiomas were included. Unbiased, comprehensive next generation sequencing was performed, and relevant clinical data was analyzed.

RESULTS

Fifteen meningiomas and one dural specimen from six patients were included. The majority of tumors (12/15) were WHO Grade I; one patient had bilateral MMs, one of which was Grade II, while the other was Grade I. We found 11/15 of our cohort specimens were of NF2-loss subtype. Meningiomas from 5/6 patients had a monoclonal origin, with the tumor from the remaining patient showing evidence for independent clonal formation. We identified a novel case of non-NF2 mutant MM with monoclonal etiology. MMs due to a monoclonal origin did not always display a homogenous genomic profile, but rather exhibited heterogeneity due to branching evolution.

CONCLUSIONS

Both NF2-loss and non-NF2 driven MMs can form due to monoclonal expansion and those tumors can acquire inter-tumoral heterogeneity through branched evolution. Grade I and II meningiomas can occur in the same patient. Thus, the molecular make-up and clinical behavior of one tumor in MMs, cannot reliably lend insight into that of the others and suggests the clinical management strategy for MMs should be tailored individually.

Clinical Significance of Molecular Alterations and Systemic Therapy for Meningiomas: Where Do We Stand?

Meningiomas are common intracranial tumors that can be treated successfully in most cases with surgical resection and/or adjuvant radiotherapy. However, approximately 20% of patients show an aggressive clinical course with tumor recurrence or progressive disease, resulting in significant morbidity and increased mortality. Despite several studies that have investigated different cytotoxic agents in aggressive meningiomas in the past several years, limited evidence of efficacy and clinical benefit has been reported thus far. Novel molecular alterations have been linked to a particular clinicopathological phenotype and have been correlated with grading, location, and prognosis of meningiomas. In this regard, SMO, AKT, and PIK3CA mutations are typical of anterior skull base meningiomas, whereas KLF4 mutations are specific for secretory histology, and BAP1 alterations are common in progressive rhabdoid meningiomas. Alterations in TERT, DMD, and BAP1 correlate with poor outcomes. Moreover, some actionable mutations, including SMO, AKT1, and PIK3CA, regulate meningioma growth and are under investigation in clinical trials. PD-L1 and/or M2 macrophage expression in the microenvironment provides evidence for the investigation of immunotherapy in progressive meningiomas.

Examination of Genetic Susceptibility in Radiation-Associated Meningioma

Previous epidemiological studies have demonstrated elevated susceptibility to ionizing radiation in some families, thus suggesting the presence of genetic components that conferred increased rate of radiation-associated meningioma (RAM). In this study, we exome-sequenced and investigated the segregation pattern of rare deleterious variants in 11 RAM pedigrees. In addition, we performed a rare-variant association analysis in 92 unrelated familial cases of RAM that were ancestry-matched with 88 meningioma-free controls. In the pedigree analysis, we found that each family carried mostly a unique set of rare deleterious variants. A follow-up pathway analysis of the union of the genes that segregated within each of the 11 pedigrees identified a single statistically significant (q value = 7.90E-04) “ECM receptor interaction” set. In the case-control association analysis, we observed no statistically significant variants or genes after multiple testing correction; however, examination of ontological categories of the genes that associated with RAM at nominal P values <0.01 identified biologically relevant pathways such as DNA repair, cell cycle and apoptosis. These results suggest that it is unlikely that a small number of highly penetrant genes are involved in the pathogenesis of RAM. Substantially larger studies are needed to identify genetic risk variants and genes in RAM.

Skull Base Tumors: Neuropathology and Clinical Implications

Tumors that arise in and around the skull base comprise a wide range of common and rare entities. Recent studies have advanced our understanding of their pathogenesis, which in some cases, have significantly influenced clinical practice. The genotype of meningiomas is strongly associated with their phenotype, including histologic subtype and tumor location, and clinical outcome. A single molecular alteration, NAB2-STAT6 fusion, has redefined the category of solitary fibrous tumors to include the previous entity hemangiopericytomas. Schwannomas, both sporadic and familial, are characterized by near ubiquitous alterations in NF2 , with additional mutations in SMARCB1 or LZTR1 in schwannomatosis. In pituitary adenohypophyseal tumors, cell lineage transcription factors such as SF-1, T-PIT, and PIT-1 are now essential for classification, providing a more rigorous taxonomy for tumors that were previously considered null cell adenomas. The pituicyte lineage transcription factor TTF-1 defines neurohypophyseal tumors, which may represent a single nosological entity with a spectrum of morphologic manifestations (ie, granular cell tumor, pituicytoma, and spindle cell oncocytoma). Likewise, the notochord cell lineage transcription factor brachyury defines chordoma, discriminating them from chondrosarcomas. The identification of nonoverlapping genetic drivers of adamantinomatous craniopharyngiomas and papillary craniopharyngiomas indicates that these are distinct tumor entities and has led to successful targeted treatment of papillary craniopharyngiomas using BRAF and/or mitogen-activated protein kinase inhibitors. Similarly, dramatic therapeutic responses have been achieved in patients with Langerhans cell histiocytosis, both with BRAF -mutant and BRAF -wildtype tumors. Familiarity with the pathology of skull base tumors, their natural history, and molecular features is essential for optimizing patient care.

Diagnostic, therapeutic, and prognostic implications of the 2021 World Health Organization classification of tumors of the central nervous system

The 2016 revised fourth edition of the World Health Organization (WHO) classification of central nervous system (CNS) tumors incorporated molecular features with histologic grading, revolutionizing how oncologists conceptualize primary brain and spinal cord tumors as well as providing new insights into their management and prognosis. The 2021 revised fifth edition of the WHO classification further integrates molecular alterations for CNS tumor categorization, updating current understanding of the pathophysiology of many of these disease entities. Here, the authors review changes in the new classification for the most common primary adult tumors-gliomas (including astrocytomas, oligodendrogliomas, and ependymomas) and meningiomas-highlighting the key genomic alterations for each group classification to help clinicians interpret them as they consider therapeutic options-including clinical trials and targeted therapies-and discuss the prognosis of these tumors with their patients. The revised, updated 2021 WHO classification also further integrates molecular alterations in the classification of pediatric CNS tumors, but those are not covered in the current review.

Eribulin prolongs survival in an orthotopic xenograft mouse model of malignant meningioma

Meningioma is the most common intracranial tumor, with generally favorable patient prognosis. However, patients with malignant meningioma typically experience recurrence, undergo multiple surgical resections, and ultimately have a poor prognosis. Thus far, effective chemotherapy for malignant meningiomas has not been established. We recently reported the efficacy of eribulin (Halaven) for glioblastoma with a telomerase reverse transcriptase (TERT) promoter mutation. This study investigated the anti–tumor effect of eribulin against TERT promoter mutation‐harboring human malignant meningioma cell lines in vitro and in vivo. Two meningioma cell lines, IOMM‐Lee and HKBMM, were used in this study. The strong inhibition of cell proliferation by eribulin via cell cycle arrest was demonstrated through viability assay and flow cytometry. Apoptotic cell death in malignant meningioma cell lines was determined through vital dye assay and immunoblotting. Moreover, a wound healing assay revealed the suppression of tumor cell migration after eribulin exposure. Intraperitoneal administration of eribulin significantly prolonged the survival of orthotopic xenograft mouse models of both malignant meningioma cell lines implanted in the subdural space (P < .0001). Immunohistochemistry confirmed apoptosis in brain tumor tissue treated with eribulin. Overall, these results suggest that eribulin is a potential therapeutic agent for malignant meningiomas.

Biology and Treatment of Meningiomas: A Reappraisal

Meningiomas are largely indolent tumors with a benign clinical course, but a minority exhibit aggressive behavior characterized by rapid growth, neurologic deficits, and increased mortality. Identifying high-risk patients requiring intervention is challenging, but recent insights into meningioma biology provide a useful guide for decision making. Standard of care for recurrent or biologically aggressive tumors consists of surgery and radiation therapy. Systemic therapies targeting vascular endothelial growth factor signaling and somatostatin analogues are potential options for those with refractory disease but display only modest activity. New paradigms in meningioma clinical trial design provide hope for improved options in the future.

EANO guideline on the diagnosis and management of meningiomas

Meningiomas are the most common intracranial tumors. Yet, only few controlled clinical trials have been conducted to guide clinical decision making, resulting in variations of management approaches across countries and centers. However, recent advances in molecular genetics and clinical trial results help to refine the diagnostic and therapeutic approach to meningioma. Accordingly, the European Association of Neuro-Oncology (EANO) updated its recommendations for the diagnosis and treatment of meningiomas. A provisional diagnosis of meningioma is typically made by neuroimaging, mostly magnetic resonance imaging. Such provisional diagnoses may be made incidentally. Accordingly, a significant proportion of meningiomas, notably in patients that are asymptomatic or elderly or both, may be managed by a watch-and-scan strategy. A surgical intervention with tissue, commonly with the goal of gross total resection, is required for the definitive diagnosis according to the WHO classification. A role for molecular profiling including gene panel sequencing and genomic methylation profiling is emerging. A gross total surgical resection including the involved dura is often curative. Inoperable or recurrent tumors requiring treatment can be treated with radiosurgery, if the size or the vicinity of critical structures allows that, or with fractionated radiotherapy (RT). Treatment concepts combining surgery and radiosurgery or fractionated RT are increasingly used, although there remain controversies regard timing, type, and dosing of the various RT approaches. Radionuclide therapy targeting somatostatin receptors is an experimental approach, as are all approaches of systemic pharmacotherapy. The best albeit modest results with pharmacotherapy have been obtained with bevacizumab or multikinase inhibitors targeting vascular endothelial growth factor receptor, but no standard of care systemic treatment has been yet defined.

Duplex-Repair enables highly accurate sequencing, despite DNA damage

Accurate DNA sequencing is crucial in biomedicine. Underlying the most accurate methods is the assumption that a mutation is true if altered bases are present on both strands of the DNA duplex. We now show that this assumption can be wrong. We establish that current methods to prepare DNA for sequencing, via ‘End Repair/dA-Tailing,’ may substantially resynthesize strands, leading amplifiable lesions or alterations on one strand to become indiscernible from true mutations on both strands. Indeed, we discovered that 7–17% and 32–57% of interior ‘duplex base pairs’ from cell-free DNA and formalin-fixed tumor biopsies, respectively, could be resynthesized in vitro and potentially introduce false mutations. To address this, we present Duplex-Repair, and show that it limits interior duplex base pair resynthesis by 8- to 464-fold, rescues the impact of induced DNA damage, and affords up to 8.9-fold more accurate duplex sequencing. Our study uncovers a major Achilles’ heel in sequencing and offers a solution to restore high accuracy.

Genomic Biomarkers of Meningioma: A Focused Review

Meningiomas represent a phenotypically and genetically diverse group of tumors which often behave in ways that are not simply explained by their pathologic grade. The genetic landscape of meningiomas has become a target of investigation as tumor genomics have been found to impact tumor location, recurrence risk, and malignant potential. Additionally, targeted therapies are being developed that in the future may provide patients with personalized chemotherapy based on the genetic aberrations within their tumor. This review focuses on the most common genetic mutations found in meningiomas of all grades, with an emphasis on the impact on tumor location and clinically relevant tumor characteristics. NF-2 and the non-NF-2 family of genetic mutations are summarized in the context of low-grade and high-grade tumors, followed by a comprehensive discussion regarding the genetic and embryologic basis for meningioma location and phenotypic heterogeneity. Finally, targeted therapies based on tumor genomics currently in use and under investigation are reviewed and future avenues for research are suggested. The field of meningioma genomics has broad implications on the way meningiomas will be treated in the future, and is gradually shifting the way clinicians approach this diverse group of tumors.

Intradural Pediatric Spinal Tumors: An Overview from Imaging to Novel Molecular Findings

Pediatric spinal tumors are rare and account for 10% of all central nervous system tumors in children. Onset usually occurs with chronic nonspecific symptoms and may depend on the intra- or extradural neoplastic location. Meningiomas, schwannomas, and neurofibromas are the most common intradural-extramedullary lesions, while astrocytomas and ependymomas represent the majority of intramedullary tumors. The new molecular discoveries regarding pediatric spinal cancer currently contribute to the diagnostic and therapeutic processes. Moreover, some familial genetic syndromes can be associated with the development of spinal tumors. Currently, magnetic resonance imaging (MRI) is the standard reference for the evaluation of pediatric spinal tumors. Our aim in this review was to describe the imaging of the most frequent intradural intra/extramedullary pediatric spinal tumors and to investigate the latest molecular findings and genetic syndromes.

Innumerable Meningiomas Arising in a Patient With Tuberous Sclerosis Complex Decades After Radiation Therapy

Meningioma is the most common radiation-induced brain neoplasm, usually occurring after a latency of 20 - 35 years, with multiplicity in 10% of cases. Radiation-induced meningiomas (RIMs) have not previously been reported in patients with tuberous sclerosis complex (TSC), unlike their well-known occurrence in other familial tumor predisposition syndrome patients. We report a TSC patient who developed numerous intracranial meningiomas twenty five year after radiation therapy for subependymal giant cell astrocytoma (SEGA). Autopsy examination showed innumerable, coalescent, benign, meningothelial meningiomas, WHO grade 1, ranging in size from 0.2 cm to 3.3 cm. Autopsy also showed small residual SEGA, radiation-induced cerebral vasculopathy, and classic TSC features including several small subependymal nodules ("candle gutterings"), white matter radial heterotopia, facial angiofibromas, dental enamel pitting, one ash leaf spot, and multiple hepatic and renal angiomyolipomas. Next-generation sequencing analysis utilizing a 500+ gene cancer panel demonstrated chromosomal loss involving the majority of chromosome 22, including the NF2 gene locus, as well as a truncating nonsense mutation in TSC1 p. R509*. While TSC patients rarely require radiation therapy, this striking case suggests that patients with TSC should be monitored closely if cranial therapeutic radiation is administered.

Clinical and genomic factors associated with seizures in meningiomas

OBJECTIVE

The association of seizures with meningiomas is poorly understood. Moreover, any relationship between seizures and the underlying meningioma genomic subgroup has not been studied. Herein, the authors report on their experience with identifying clinical and genomic factors associated with preoperative and postoperative seizure presentation in meningioma patients.

METHODS

Clinical and genomic sequencing data on 394 patients surgically treated for meningioma at Yale New Haven Hospital were reviewed. Correlations between clinical, histological, or genomic variables and the occurrence of preoperative and postoperative seizures were analyzed. Logistic regression models were developed for assessing multiple risk factors for pre- and postoperative seizures. Mediation analyses were also conducted to investigate the causal pathways between genomic subgroups and seizures.

RESULTS

Seventeen percent of the cohort had presented with preoperative seizures. In a univariate analysis, patients with preoperative seizures were more likely to have tumors with a somatic NF2 mutation (p = 0.020), WHO grade II or III tumor (p = 0.029), atypical histology (p = 0.004), edema (p < 0.001), brain invasion (p = 0.009), and worse progression-free survival (HR 2.68, 95% CI 1.30-5.50). In a multivariate analysis, edema (OR 3.11, 95% CI 1.46-6.65, p = 0.003) and atypical histology (OR 2.00, 95% CI 1.03-3.90, p = 0.041) were positive predictors of preoperative seizures, while genomic subgroup was not, such that the effect of an NF2 mutation was indirectly mediated through atypical histology and edema (p = 0.012). Seizure freedom was achieved in 83.3% of the cohort, and only 20.8% of the seizure-free patients, who were more likely to have undergone gross-total resection (p = 0.031), were able to discontinue antiepileptic drug use postoperatively. Preoperative seizures (OR 3.54, 95% CI 1.37-9.12, p = 0.009), recurrent tumors (OR 2.89, 95% CI 1.08-7.74, p = 0.035), and tumors requiring postoperative radiation (OR 2.82, 95% CI 1.09-7.33, p = 0.033) were significant predictors of postoperative seizures in a multivariate analysis.

CONCLUSIONS

Seizures are relatively common at meningioma presentation. While NF2-mutated tumors are significantly associated with preoperative seizures, the association appears to be mediated through edema and atypical histology. Patients who undergo radiation and/or have a recurrence are at risk for postoperative seizures, regardless of the extent of resection. Preoperative seizures may indeed portend a more potentially aggressive molecular entity and challenging clinical course with a higher risk of recurrence.

Chromatin Alterations in Neurological Disorders and Strategies of (Epi)Genome Rescue

Neurological disorders (NDs) comprise a heterogeneous group of conditions that affect the function of the nervous system. Often incurable, NDs have profound and detrimental consequences on the affected individuals' lives. NDs have complex etiologies but commonly feature altered gene expression and dysfunctions of the essential chromatin-modifying factors. Hence, compounds that target DNA and histone modification pathways, the so-called epidrugs, constitute promising tools to treat NDs. Yet, targeting the entire epigenome might reveal insufficient to modify a chosen gene expression or even unnecessary and detrimental to the patients' health. New technologies hold a promise to expand the clinical toolkit in the fight against NDs. (Epi)genome engineering using designer nucleases, including CRISPR-Cas9 and TALENs, can potentially help restore the correct gene expression patterns by targeting a defined gene or pathway, both genetically and epigenetically, with minimal off-target activity. Here, we review the implication of epigenetic machinery in NDs. We outline syndromes caused by mutations in chromatin-modifying enzymes and discuss the functional consequences of mutations in regulatory DNA in NDs. We review the approaches that allow modifying the (epi)genome, including tools based on TALENs and CRISPR-Cas9 technologies, and we highlight how these new strategies could potentially change clinical practices in the treatment of NDs.

Proton therapy: A therapeutic opportunity for aggressive pediatric meningioma

Meningiomas are an extremely rare histology among pediatric brain tumors, and there is a shortage of literature on their management. Proton therapy is currently used safely and effectively for many types of both pediatric and adult cancer, and its main advantage is the sparing of healthy tissues from radiation, which could translate in the reduction of late side effects. We review the literature on radiotherapy and proton therapy for pediatric meningiomas and report clinical outcomes for two aggressive pediatric meningiomas we treated with protons. Proton therapy might be a safe and effective therapeutic option for this rare subgroup of tumors.

Inherited genetic syndromes and meningiomas

Meningiomas arising with inherited genetic syndromes occur nearly exclusively in the context of neurofibromatosis type 2 (NF2). NF2 is an autosomal dominant familial neoplasia syndrome that results from a mutation in the NF2 tumor suppressor gene located on the long arm of chromosome 22. The NF2 gene encodes for the protein merlin (moesin-ezrin-radixin-like protein), which has tumor suppressive effects that are reduced/inactivated in NF2-associated tumors. NF2-associated neoplasms affect the nervous system (schwannomas, meningiomas, ependymomas, astrocytomas, and neurofibromas) and skin. Other NF2 findings include ophthalmological lesions and peripheral neuropathy. Meningiomas are the second most frequent NF2-associated tumors (occurring in approximately half of all NF2 patients). They are often multiple and have unpredictable growth patterns. NF2-associated meningiomas can cause significant morbidity and mortality due to their location and a mass effect. Because of the multiplicity, frequent development of new tumors, and their protean nature, defined treatment strategies with serial surveillance is critical for optimal management of NF2-associated meningiomas. While surgical resection is the primary treatment for NF2-associated meningiomas, radiation plays an important adjunctive role in the management of recurrent and inoperable meningiomas.