Neurofibromatosis 2 [Bilateral acoustic neurofibromatosis, central neurofibromatosis, NF2, neurofibromatosis type II]

NF2-Related Schwannomatosis (NF2): Molecular Insights and Therapeutic Avenues

NF2-related schwannomatosis (NF2) is a genetic syndrome characterized by the growth of benign tumors in the nervous system, particularly bilateral vestibular schwannomas, meningiomas, and ependymomas. This review consolidates the current knowledge on NF2 syndrome, emphasizing the molecular pathology associated with the mutations in the gene of the same name, the NF2 gene, and the subsequent dysfunction of its product, the Merlin protein. Merlin, a tumor suppressor, integrates multiple signaling pathways that regulate cell contact, proliferation, and motility, thereby influencing tumor growth. The loss of Merlin disrupts these pathways, leading to tumorigenesis. We discuss the roles of another two proteins potentially associated with NF2 deficiency as well as Merlin: Yes-associated protein 1 (YAP), which may promote tumor growth, and Raf kinase inhibitory protein (RKIP), which appears to suppress tumor development. Additionally, this review discusses the efficacy of various treatments, such as molecular therapies that target specific pathways or inhibit neomorphic protein-protein interaction caused by NF2 deficiency. This overview not only expands on the fundamental understanding of NF2 pathophysiology but also explores the potential of novel therapeutic targets that affect the clinical approach to NF2 syndrome.

Gene Therapy for Neurofibromatosis Type 2-Related Schwannomatosis: Recent Progress, Challenges, and Future Directions

Neurofibromatosis type 2 (NF2)-related schwannomatosis is a rare autosomal dominant monogenic disorder caused by mutations in the NF2 gene. The hallmarks of NF2-related schwannomatosis are bilateral vestibular schwannomas (VS). The current treatment options for NF2-related schwannomatosis, such as observation with serial imaging, surgery, radiotherapy, and pharmacotherapies, have shown limited effectiveness and serious complications. Therefore, there is a critical demand for novel effective treatments. Gene therapy, which has made significant advancements in treating genetic diseases, holds promise for the treatment of this disease. This review covers the genetic pathogenesis of NF2-related schwannomatosis, the latest progress in gene therapy strategies, current challenges, and future directions of gene therapy for NF2-related schwannomatosis.

Spontaneous Regression of a Large Vestibular Schwannoma: Is Nonoperative Management Reasonable?

Vestibular schwannomas (VSs) are the most common cerebellopontine tumors. The natural history of smaller-sized VSs (<30 mm) has been well-studied, leading to the recommendation of a "watch and wait" approach. However, large VSs (>30 mm) have not been extensively studied, mainly because of their rarity. As such, most patients are conventionally offered surgery which carries a significant risk of neurological morbidity. Here, we report a case of a giant VS (>40 mm) in a 30-year-old man who regressed spontaneously. He was lost to follow-up for 18 years and, upon re-presentation, the symptomatology drastically improved and repeat imaging demonstrated a marked reduction in tumor size. Referring to similar cases in other studies, we postulate that most large and giant VSs undergo a phase of growth and stasis, followed by regression due to shifts in the balance between tumorigenic and regressive factors. Taken together with emerging molecular data, further studies are required to better understand the history of large and giant VSs to shape more personalized treatment options. This potentially includes non-operative management as a tenable option.

Stem cell modeling of nervous system tumors

Nervous system tumors, particularly brain tumors, represent the most common tumors in children and one of the most lethal tumors in adults. Despite decades of research, there are few effective therapies for these cancers. Although human nervous system tumor cells and genetically engineered mouse models have served as excellent platforms for drug discovery and preclinical testing, they have limitations with respect to accurately recapitulating important aspects of the pathobiology of spontaneously arising human tumors. For this reason, attention has turned to the deployment of human stem cell engineering involving human embryonic or induced pluripotent stem cells, in which genetic alterations associated with nervous system cancers can be introduced. These stem cells can be used to create self-assembling three-dimensional cerebral organoids that preserve key features of the developing human brain. Moreover, stem cell-engineered lines are amenable to xenotransplantation into mice as a platform to investigate the tumor cell of origin, discover cancer evolutionary trajectories and identify therapeutic vulnerabilities. In this article, we review the current state of human stem cell models of nervous system tumors, discuss their advantages and disadvantages, and provide consensus recommendations for future research.

Neurofibromatosis type1, type 2, tuberous sclerosis and Von Hippel-Lindau disease

Neurocutaneous syndromes (also known as phakomatoses) are heterogenous group of disorders that involve derivatives of the neuroectoderm. Each disease has diagnostic and pathognomonic criteria, once identified, thorough clinical examination to the patient and the family members should be done. Magnetic resonance imaging (MRI) is used to study the pathognomonic findings withing the CNS (Evans et al. in Am J Med Genet A 152A:327-332, 2010). This chapter includes the 4 most common syndromes faced by neurosurgeons and neurologists; neurofibromatosis types 1 and 2, tuberous sclerosis and Von Hippel-Lindau disease. Each syndrome has specific genetic anomaly that involves a tumor suppressor gene and the loss of inhibition of specific pathways. The result is a spectrum of cutaneous manifestations and neoplasms.

Surgical Management of Meningiomas Involving the Torcula, Transverse Sinus, and Jugular Bulb: A Technical Note and Review of the Literature

Meningiomas that invade the confluens sinuum are rare and require extensive preoperative planning. Here, we describe the surgical and radio-oncological management of an aggressive large occipital meningioma invading the superior sagittal sinus, torcula, right and left transverse sinus down to the level of the jugular bulb in a 21-year-old female patient. Details of the surgical approach are presented to highlight the planned staged resection of this tumor at the level of the torcula to initially debulk the lesion while preserving venous outflow through the patent's sinus. Once the tumor fully occluded the confluens, a second-stage en bloc resection ensued. Postsurgical adjuvant radiation therapy was delivered via fractionated external beam therapy which has provided local control of the tumor since. This case is being discussed in the context of the pertinent literature to demonstrate the highly complex interdisciplinary and staged management of partially intravascular meningiomas involving the major venous sinuses.

Vestibular Impairment in Patients with Vestibular Schwannoma: A Journey through the Pitfalls of Current Literature

Vestibular Schwannoma is the most common tumour of Ponto Cerebellar Angle and is capable of strongly impacting the patient's quality of life. In recent decades, the proposals for the management of the disease have multiplied, just as the diagnostic capacity has improved. While in the past, the primary objective was the preservation of the facial function, and subsequently also of the auditory function, the attention to the vestibular symptomatology, which appears to be one of the main indicators of deterioration of quality of life, is still unsatisfactory. Many authors have tried to provide guidance on the best possible management strategy, but a universally recognized guideline is still lacking. This article offers an overview of the disease and the proposals which have advanced in the last twenty years, evaluating their qualities and defects in a critical reading.

A review of bilateral sudden sensorineural hearing loss in pediatric patients

OBJECTIVE

Bilateral, sudden sensorineural hearing loss (SSNHL) in the pediatric population is a rare phenomenon potentially detrimental to language acquisition and social development. This study comprehensively reviews and analyzes existing literature to determine any correlation or commonality in etiologies, presentations, and management of this condition.

METHODS

PubMed, Cochrane, Scopus, and Web of Science databases were systematically searched for articles related to pediatric SSNHL from 1970 to 2021. Case series, case reports, and cohort studies were included. Data on patient demographics, etiology, diagnostic testing, management, and hearing recovery were collected.

RESULTS

Excluding duplicates, 553 unique titles were identified by established search criteria, of which 342 titles were relevant to pediatric sudden hearing loss. Forty-six papers reported cases of bilateral SSNHL, totaling 145 individual cases. Not included in the analysis were 45 cases documented as non-organic hearing loss. The average age of the total 145 included patients was 8.5 years and 51 were male. Reported etiologies included cytomegalovirus (n = 3), meningitis (n = 13), mumps (n = 5), ototoxin exposure (n = 13), and enlarged vestibular aqueduct (n = 9). Tinnitus (n = 30) was the most reported concurrent symptom, followed by vertigo (n = 21). Systemic steroid therapy was the most common treatment and, when follow up was reported, most patients (51.2%) had complete or partial recovery of hearing.

CONCLUSIONS

This is a comprehensive review of pediatric bilateral SSNHL. Though often idiopathic, etiologies also include infectious, structural, and autoimmune. Treatment largely consists of systemic steroid therapy, with variables rates of recovery. Further studies on intratympanic administration of steroids may guide future treatment.

Multiple craniospinal tumors in a pediatric patient with neurofibromatosis type 2: a case report

INTRODUCTION

Neurofibromatosis type 2 (NF-2) is an inherited disease, linked with abnormalities in the NF-2 gene, which is located on chromosome 22 and involved in merlin production. Many craniospinal tumors are common in individuals with NF-2. We present a case of NF-2 with the rapid symptomatic progression of multiple craniospinal tumors.

CASE REPORT

A 12-year-old male complained of headache and hearing impairment in the right ear for 7 months. Brain magnetic resonance imaging (MRI) revealed a right frontal meningioma, bilateral vestibular and trigeminal schwannomas, and a brainstem tumor. He was diagnosed with NF-2 and underwent brain surgery and radiotherapy for chordoid meningioma. He complained of right leg motor weakness 5 months post-surgery. The spine MRI showed multiple heterogeneously enhanced masses spreading over the entire spinal cord. The symptomatic intradural extramedullary mass at the cervicothoracic area was removed and the histological finding was schwannoma. His leg motor weakness was relieved after surgery. At the 6-month follow-up, brain MRI revealed the progression of the vestibular schwannoma, trigeminal schwannoma, and brainstem tumor. The patient was treated with bevacizumab (5 mg/kg) every 2 weeks for 6 months. For 2 years, all of the craniospinal tumors were stable without neurological deterioration after the completion of chemotherapy.

CONCLUSION

Meningiomas and schwannomas grow slowly in most patients with NF-2, but these multiple craniospinal tumors can show sudden rapid growth and manifest as neurological symptoms in a pediatric patient. These tumors could be controlled with local symptomatic and systemic bevacizumab treatments.

Celastrol suppresses the growth of vestibular schwannoma in mice by promoting the degradation of β-catenin

Vestibular schwannoma (VS), one of characteristic tumors of neurofibromatosis type 2 (NF2), is an intracranial tumor that arises from Schwann cells of the vestibular nerve. VS results in hearing loss, tinnitus, dizziness, and even death, but there are currently no FDA-approved drugs for treatment. In this study, we established a high-throughput screening to discover effective compounds that could inhibit the viability of VS cells. Among 1019 natural products from the Korea Chemical Bank screened, we found that celastrol, a pentacyclic triterpene derived from a Tripterygium Wilfordi plant, exerted potent inhibitory effect on the viability of VS cells with an IC50 value of 0.5  µM. Celastrol (0.5, 1  µM) dose-dependently inhibited the proliferation of primary VS cells derived from VS patients. Celastrol also inhibited the growth, and induced apoptosis of two other VS cell lines (HEI-193 and SC4). Aberrant activation of Wnt/β-catenin signaling has been found in VS isolated from clinically defined NF2 patients. In HEI-193 and SC4 cells, we demonstrated that celastrol (0.1, 0.5 μM) dose-dependently inhibited TOPFlash reporter activity and protein expression of β-catenin, but not mRNA level of β-catenin. Furthermore, celastrol accelerated the degradation of β-catenin by promoting the formation of the β-catenin destruction complex. In nude mice bearing VS cell line SC4 allografts, administration of celastrol (1.25 mg · kg-1 · d-1, i.p. once every 3 days for 2 weeks) significantly suppressed the tumor growth without showing toxicity. Collectively, this study demonstrates that celastrol can inhibit Wnt/β-catenin signaling by promoting the degradation of β-catenin, consequently inhibiting the growth of VS.

The Hippo pathway in cancer: YAP/TAZ and TEAD as therapeutic targets in cancer

Tumorigenesis is a highly complex process, involving many interrelated and cross-acting signalling pathways. One such pathway that has garnered much attention in the field of cancer research over the last decade is the Hippo signalling pathway. Consisting of two antagonistic modules, the pathway plays an integral role in both tumour suppressive and oncogenic processes, generally via regulation of a diverse set of genes involved in a range of biological functions. This review discusses the history of the pathway within the context of cancer and explores some of the most recent discoveries as to how this critical transducer of cellular signalling can influence cancer progression. A special focus is on the various recent efforts to therapeutically target the key effectors of the pathway in both preclinical and clinical settings.

Clinical manifestations and genetic analysis of a family with neurofibromatosis type 2

BACKGROUND

Neurofibromatosis type 2 (NF2) is an autosomal dominantly inherited disease with slow, yet potentially life-threatening progression.

OBJECTIVE

We describe the clinical manifestations and genetic profile of a family with NF2.

METHODS

We enrolled a 16-member family with NF2. We collected clinical examinations and imaging information. Genetic analysis was conducted through multiplex ligation-dependent probe amplification (MLPA). The SALSA MLPA probemix P044-B2 NF2 kit was used to detect genetic variations in genomic upstream and 17 exons of the NF2 gene.

RESULTS

The most common clinical manifestation was hearing impairment (37.5%), followed by tinnitus (18.8%). Four participants had vestibular schwannoma: 2 were bilateral and 2 unilateral, and tumor size ranged from 86.3 to 5064 mm³. A weak correlation between hearing impairment and tumor size was observed. Genetic analysis revealed that the DNA dosages of exons 9, 10, and 11 of the NF2 gene in 3 diseased family members (participants #3, #5, and #11) were higher than those in the controls. However, we could not detect an indicative abnormal DNA dosage of NF2 in participant #6 despite such a dosage being considered a diagnostic indicator of NF2.

CONCLUSIONS

Hearing impairment was the most common clinical manifestation in this family. The NF2 gene is a gene of interest that warrants familial genetic screening.

Origins of biallelic inactivation of NF2 in Neurofibromatosis Type 2

BACKGROUND

Elucidating the mechanism by which biallelic inactivation evolved could provide a mechanistic understanding for NF2 tumorigenesis and also a rationale for clinical management.

METHODS

A cohort of 60 NF2 patients was recruited. Next-generation sequencing of tumor and paired control samples was used to explore how NF2 mutations evolve in determining the clinical phenotypes.

RESULTS

Total 60 blood samples (one from each patient) and 61 (from 35 patients) NF2 associated tumors were collected. Next-generation sequencing of the blood samples detected "first hit" NF2 mutation in 35/60 donors (58.3%), 82.9% of which (29/35) bear heterozygous germline mutations, and 17.1% (6/35) of which are mosaics with variable allelic frequency (VAF). Whilst a number of NF2 patients were found without germline mutation, most (57/61, 93.4%) NF2 associated tumors were identified with NF2 somatic mutation. We calculated the correlation between the onset latency of mosaic and germline NF2 allele carriers with the mosaicism VAF. The mosaicism VAF is negatively and linearly correlated to clinical symptom onset latency (R2 0.3677, P=0.00351), suggesting biallelic inactivation probability is a linear function of 'first hit' prevalence in the body. The second NF2 somatic mutation occurrence time positively correlates with the onset of clinical symptom (R2=0.4151, P=0.02633), suggesting tumor growth is linearly proportional to the time after biallelic inactivation.

CONCLUSIONS

Our results suggested that biallelic inactivation of NF2 evolved through neutral drift and pre-existing first hit NF2 allele determines certain aspects of the clinical symptom. Genetic diagnosis should be included in the diagnostic criteria and treatment consideration of NF2.

RKIP Induction Promotes Tumor Differentiation via SOX2 Degradation in NF2-Deficient Conditions

Loss of NF2 (merlin) has been suggested as a genetic cause of neurofibromatosis type 2 and malignant peripheral nerve sheath tumor (MPNST). Previously, we demonstrated that NF2 sustained TGFβ receptor 2 (TβR2) expression and reduction or loss of NF2 activated non-canonical TGFβ signaling, which reduced Raf kinase inhibitor protein (RKIP) expression via TβR1 kinase activity. Here, we show that a selective RKIP inducer (novel chemical, Nf18001) inhibits tumor growth and promotes schwannoma cell differentiation into mature Schwann cells under NF2-deficient conditions. In addition, Nf18001 is not cytotoxic to cells expressing NF2 and is not disturb canonical TGFβ signaling. Moreover, the novel chemical induces expression of SOX10, a marker of differentiated Schwann cells, and promotes nuclear export and degradation of SOX2, a stem cell factor. Treatment with Nf18001 inhibited tumor growth in an allograft model with mouse schwannoma cells. These results strongly suggest that selective RKIP inducers could be useful for the treatment of neurofibromatosis type 2 as well as NF2-deficient MPNST. IMPLICATIONS: This study identifies that a selective RKIP inducer inhibits tumor growth and promotes schwannoma cell differentiation under NF2-deficient conditions by reducing SOX2 and increasing SOX10 expression.

Neurofibromatosis 2: Primary Modality of Hearing Rehabilitation with Cochlear Implant

Auditory Brainstem Implants have been recommended as the gold standard in hearing rehabilitation of Neurofibromatosis Type 2 patients who lose hearing completely in both the ears and the cochlear nerves are not stimulable. Some patients have undergone cochlear implantation, in whom the cochlear nerve was spared during surgery or have undergone stereotactic radiotherapy preserving the function of the cochlear nerve. Here we report a case in whom we chose cochlear implantation prior to any definitive treatment for the tumour itself during the 'wait and watch' period. The reasons in favour of this approach have been discussed in this article. Post switch-on the implant is benefitting the patient satisfactorily and she is on regular follow up for monitoring the bilateral tumours.

Treatment Analysis and Overall Survival Outcomes of Patients With Bilateral Vestibular Schwannoma

OBJECTIVES

To investigate the clinical presentation, treatment breakdown, and overall survival (OS) outcomes of patients with neurofibromatosis type 2 (NF2)-associated bilateral vestibular schwannoma (NVS).

METHODS

The 2004 to 2016 National Cancer Database was queried for patients with a diagnosis of VS. The "Laterality" code was used to stratify patients into sporadic unilateral vestibular schwannoma (UVS) and NVS.

RESULTS

Of the 33,839 patients with VS, 155 (0.46%) were coded for NVS with an average age and tumor size of 37.4 ± 20.5 years and 23.5 ± 18.2 mm. Patients underwent observation (45.3%), surgery (29.3%), and radiotherapy (20.0%), and had a 5.8% 5-year mortality rate. Compared with UVS, NVS was negatively associated with receiving surgery (40.2% versus 29.3%, p = 0.02) while watchful observation was more prevalent (30.1% versus 45.3%, p = 0.001). In NVS, undergoing surgery was associated with larger tumor size (34.5 ± 21.2 versus 17.8 ± 13.3 mm, p = 0.001) and shorter diagnosis-to-treatment time (49.1 ± 60.6 versus 87.0 ± 78.5 d, p = 0.02), radiotherapy was associated with older age (44.4 ± 18.9 versus 35.2 ± 20.6 yr, p = 0.02) and longer diagnosis-to-treatment time (85.9 ± 77.9 versus 53.9 ± 65.5 d, p = 0.04), and observation was associated with smaller tumor size (17.8 ± 15.9 versus 28.0 ± 19.2 mm, p = 0.01). Kaplan-Meier log-rank analysis demonstrated similar 10-year OS between NVS and UVS patients (p = 0.58) without factoring the earlier age of presentation. Furthermore, there were no temporal changes in presentation/management of NVS, and OS was not dependent on the received treatment (p = 0.30).

CONCLUSIONS

With younger age, larger tumors, and more conservative management, NVS's OS was not treatment-dependent and was similar to sporadic UVS, though the latter should not be interpreted as similar life expectancies due to the much earlier presentation.

Genetic syndromes predisposing to pediatric brain tumors

The application of high-throughput sequencing approaches including paired tumor/normal sampling with therapeutic intent has demonstrated that 8%-19% of pediatric CNS tumor patients harbor a germline alteration in a classical tumor predisposition gene (NF1, P53). In addition, large-scale germline sequencing studies in unselected cohorts of pediatric neuro-oncology patients have demonstrated novel candidate tumor predisposition genes (ELP1 alterations in sonic hedgehog medulloblastoma). Therefore, the possibility of an underlying tumor predisposition syndrome (TPS) should be considered in all pediatric patients diagnosed with a CNS tumor which carries critical implications including accurate prognostication, selection of optimal therapy, screening, risk reduction, and family planning. The Pediatric Cancer Working Group of the American Association for Cancer Research (AACR) recently published consensus screening recommendations for children with the most common TPS. In this review, we provide an overview of the most relevant as well as recently identified TPS associated with the most frequently encountered pediatric CNS tumors with an emphasis on pathogenesis, genetic testing, clinical features, and treatment implications.

Rationale and Design of BeatNF2 Trial: A Clinical Trial to Assess the Efficacy and Safety of Bevacizumab in Patients with Neurofibromatosis Type 2 Related Vestibular Schwannoma

Simple Summary

Neurofibromatosis type 2 (NF2) is a rare genetic hereditary disease characterized by multiple central nervous system tumors, most frequently bilateral vestibular schwannomas (VSs). No chemotherapeutic agents are available for clinical use, and surgery and radiotherapy are the only therapeutic options available now. Still, neither treatment option alleviates hearing loss in patients with NF2 and VS; they may even exacerbate it. However, bevacizumab has been reported to be effective in suppressing the tumor’s growth and has shown unprecedented efficacy in improving hearing. We describe a new ongoing and novel clinical trial, BeatNF2, a randomized, double-blinded, placebo-controlled, multicenter trial to assess bevacizumab’s efficacy and safety in patients with NF2. The study’s primary endpoint is improved hearing function 24 weeks after the beginning of the treatment protocol.

Abstract

Neurofibromatosis type 2 (NF2) causes bilateral vestibular schwannomas (VSs), leading to deafness. VS is treated by surgery or radiation, but neither treatments prevent hearing loss. Bevacizumab was found to be effective in suppressing the tumor’s growth and may help to improve hearing. We are conducting a randomized, double-blind, multicenter clinical trial to verify the efficacy and safety of bevacizumab in NF2-related VS. The primary objective is to evaluate the efficacy of bevacizumab in improving hearing in the affected ear. One of the secondary objectives is to evaluate bevacizumab’s efficacy in rechallenge treatment in relapsed cases. Sixty patients will randomly receive either bevacizumab or a placebo and will be clinically observed for 48 weeks in the initial intervention phase. In the first half (24 weeks), they will receive either 5 mg/kg of bevacizumab or a placebo drug. In the second half, all patients will receive 5 mg/kg of bevacizumab. If hearing function deteriorated in a patient who had shown improvement during the first phase, a rechallenge dose with bevacizumab would be offered.

mTOR kinase inhibition disrupts neuregulin 1-ERBB3 autocrine signaling and sensitizes NF2-deficient meningioma cellular models to IGF1R inhibition

Meningiomas (MNs), arising from the arachnoid/meningeal layer, are nonresponsive to chemotherapies, with ∼50% showing loss of the Neurofibromatosis 2 (NF2) tumor suppressor gene. Previously, we established NF2 loss activates mechanistic target of rapamycin complex 1 (mTORC1) and mechanistic target of rapamycin complex 2 (mTORC2) signaling, leading to clinical trials for NF2 and MN. Recently our omics studies identified activated ephrin (EPH) receptor and Src family kinases upon NF2 loss. Here, we report increased expression of several ligands in NF2-null human arachnoidal cells (ACs) and the MN cell line Ben-Men-1, particularly neuregulin-1/heregulin (NRG1), and confirm increased NRG1 secretion and activation of V-ERB-B avian erythroblastic leukemia viral oncogene homolog 3 (ERBB3) receptor kinase. Conditioned-medium from NF2-null ACs or exogenous NRG1 stimulated ERBB3, EPHA2, and mTORC1/2 signaling, suggesting pathway crosstalk. NF2-null cells treated with an ERBB3-neutralizing antibody partially downregulated mTOR pathway activation but showed no effect on viability. mTORC1/2 inhibitor treatment decreased NRG1 expression and downregulated ERBB3 while re-activating pAkt T308, suggesting a mechanism independent of NRG1-ERBB3 but likely involving activation of another upstream receptor kinase. Transcriptomics after mTORC1/2 inhibition confirmed decreased ERBB3/ERBB4 while revealing increased expression of insulin-like growth factor receptor 1 (IGF1R). Drug treatment co-targeting mTORC1/2 and IGF1R/insulin receptor attenuated pAkt T308 and showed synergistic effects on viability. Our findings indicate potential autocrine signaling where NF2 loss leads to secretion/activation of NRG1-ERBB3 signaling. mTORC1/2 inhibition downregulates NRG1-ERBB3, while upregulating pAkt T308 through an adaptive response involving IGF1R/insulin receptor and co-targeting these pathways may prove effective for treatment of NF2-deficient MN.

MiR-25-3p Serves as an Oncogenic MicroRNA by Downregulating the Expression of Merlin in Osteosarcoma

PURPOSE

Moesin-ezrin-radixin-like protein (Merlin) has been identified as a tumor suppressor in several types of cancers. However, the biological function of Merlin in osteosarcoma remains unclear. MicroRNAs (miRNAs) can influence cancer progression by targeting oncogenes or anti-oncogenes. In this study, we sought to evaluate the regulation of Merlin expression by miR-25-3p and the role of the miR-25-3p/Merlin axis in osteosarcoma progression, with the aim of identifying a potential therapeutic target for osteosarcoma.

MATERIALS AND METHODS

TCGA (The Cancer Genome Atlas) database was used to analyze the correlation between Merlin expression and prognosis. RT-qPCR and Western blotting analyses were performed to compare Merlin expression between normal and malignant cells. A dual-luciferase reporter assay was performed to evaluate the direct targeting of Merlin by miR-25-3p. We overexpressed miR-25-3p, or/and Merlin, in U-2 OS and 143B cells, and studied their cellular functions in vitro. MTT and colony formation assays were performed to determine the effects on cell growth. EdU and cell cycle assays were performed to analyze the effects in cell replication. We used annexin V-fluorescein isothiocyanate and propidium iodide to stain apoptotic cells, and analyzed the cells using flow cytometry. The effects on cell metastasis were studied in wound healing and transwell assays. Lastly, the underlying mechanism was determined in RT-qPCR and Western blotting experiments.

RESULTS

Low Merlin expression was linked to poor prognosis. miR-25-3p was observed to directly target Merlin and downregulate its expression. miR-25-3p promoted cell growth, migration, and invasion, and inhibited apoptosis induced by cisplatin. Moreover, the overexpression of Merlin reversed the abovementioned effects of miR-25-3p. Further, the miR-25-3p/Merlin axis was observed to play an important role in the Hippo pathway, and regulated the expression of genes such as BIRC5, CTGF, and CYR61.

CONCLUSION

miR-25-3p functions as an oncogenic microRNA in osteosarcoma by targeting Merlin, and may serve as a potential therapeutic target for osteosarcoma.

Multiple Schwannomas of the Lower Extremity

This case study presents a 72-year-old male patient who presented with multiple schwannomas. The patient underwent several soft-tissue mass excisions performed by general surgery and podiatry. The physical examination displayed multiple nodules on the left foot, ankle, and previously in the groin. Magnetic resonance imaging displayed high-T2-weighted signal masses in the left plantar heel and ankle. These masses were excised and, through pathologic analysis, were diagnosed as schwannomas. Immunohistochemistry displayed a mosaic pattern of INI1 expression, a gene associated with tumor suppression. The patient demonstrated findings consistent with multiple schwannomas (eg, schwannomatosis or neurofibromatosis type 2). Because of the patient's medical history, neurofibromatosis type 2 was more probable.

Bevacizumab for NF2-associated vestibular schwannomas of childhood and adolescence

Seventeen children at six institutions with neurofibromatosis type 2 (NF2)-related vestibular schwannomas received bevacizumab. Eight of the 13 patients with initial hearing loss (61%) showed objective hearing improvement within six months of treatment. No patients showed hearing deterioration during therapy; however, only two patients showed objective radiological response. Seven of eight patients had tumor progression or worsening hearing loss upon cessation of treatment. Bevacizumab was well tolerated with no patients discontinuing therapy. Bevacizumab appears to postpone hearing loss in childhood NF2-associated vestibular schwannomas, but responses are not durable, suggesting that either longer maintenance therapy or new strategies are required.

[Hereditary predisposition to tumors of the central and peripheral nervous systems]

Some tumors of the central and peripheral nervous system may be associated with a cancer predisposition syndrome, either hereditary or occurring de novo. Such a syndrome is usually associated with multiple tumors occurring early in life. Patients with neurofibromatosis type 1 present with multiple neurofibromas, especially of the plexiform type (which may transform into malignant peripheral nerve sheath tumor), and pilocytic astrocytomas of the optic pathways. Neurofibromatosis type 2 patients present with multiple schwannomas (typically bilateral vestibular schwannomas), meningiomas, and ependymomas. Li-Fraumeni syndrome (germline TP53 mutation) is associated with choroid plexus tumors (carcinomas), medulloblastomas, and diffuse astrocytomas. Multiple hemangioblastomas are characteristic of von Hippel-Lindau syndrome while subependymal giant cell astrocytomas are pathognomonic of tuberous sclerosis complex. Dysplastic cerebellar gangliocytomas of adult patients occur in Cowden syndrome. Turcot syndrome overlaps with constitutional mismatch repair deficiency syndrome (CMMRD), which is associated with giant cell glioblastomas. Rhabdoid tumor predisposition syndrome (germline mutation of SMARCB1/INI1) is associated with atypical teratoid/rhabdoid tumors. Tumors arising in the setting of a cancer predisposition syndrome develop along specific genetic pathways. Some histopathological and immunohistochemical characteristics of these tumors may point toward such a syndrome. The diagnosis of a cancer predisposition syndrome is of tremendous importance to the patients and their families who require genetic counseling and long-term follow-up.

Bevacizumab Therapy of Neurofibromatosis Type 2 Associated Vestibular Schwannoma in Japanese Patients

We conducted a feasibility study to investigate the therapeutic effect of bevacizumab on vestibular schwannomas (VS) associated with neurofibromatosis type 2 (NF2) in a sample of Japanese patients. Ten NF2 patients were selected between 2013 and 2018: nine women and one man, with ages ranging from 12 to 45 years (mean: 29.4). Bevacizumab was administered intravenously in 5 mg/kg doses four times, with an inter-dose interval of 2 weeks. Seventeen tumors were followed for 3-72 months (mean: 39). A reduction from baseline tumor volume of at least 20% was considered a therapeutic radiologic response. Maximum reduction in tumor volume was identified in the 3rd month in 11 tumors, and in the 6th month in three tumors. Three tumors did not show any response to bevacizumab. A radiologic response was detected in seven tumors (41%). There was a significantly lower tumor volume mean in the 3rd month in comparison to the baseline for the entire sample. Tumors in patients aged 25 and above showed a significant reduction in volume in the 3rd month and significantly lower tumor-volume-to-baseline ratio than younger patients in both the 3rd and 6th months. The interaction between 'time' and 'age group' factors significantly affected the therapeutic outcome of bevacizumab on tumor volume. This study investigated the therapeutic effects of bevacizumab on NF2-associated vestibular schwannomas in Japanese patients. Bevacizumab appears to be a useful therapeutic choice in NF2 cases to control the growth of VS. Therefore, a randomised control trial to prove this assumption is necessary.

Current status and recommendations for imaging in neurofibromatosis type 1, neurofibromatosis type 2, and schwannomatosis

Neurofibromatosis type 1 (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis (SWN) are three clinically distinct tumor predisposition syndromes with a shared tendency to develop peripheral and central nervous system neoplasms. Disease expression and complications of NF1, NF2, and SWN are highly variable, necessitating a multidisciplinary approach to care in order to optimize outcomes. This review will discuss the imaging appearance of NF1, NF2, and SWN and highlight the important role that imaging plays in informing management decisions in people with tumors associated with these syndromes. Recent technological advances, including the role of both whole-body and localized imaging strategies, routine anatomic and advanced magnetic resonance (MR) imaging sequences such as diffusion-weighted imaging (DWI) with quantitative apparent diffusion coefficient (ADC) mapping, and metabolic imaging techniques (MR spectroscopy and positron emission testing) are discussed in the context of the diagnosis and management of people with NF1, NF2, and SWN based on the most up-to-date clinical imaging studies.

Nonsteroidal sulfamate derivatives as new therapeutic approaches for Neurofibromatosis 2 (NF2)

BACKGROUND

Neurofibromatosis 1 and 2, although involving two different tumour suppressor genes (neurofibromin and merlin, respectively), are both cancer predisposition syndromes that disproportionately affect cells of neural crest origin. New therapeutic approaches for both NF1 and NF2 are badly needed. In promising previous work we demonstrated that two non-steroidal analogues of 2-methoxy-oestradiol (2ME2), STX3451(2-(3-bromo-4,5-dimethoxybenzyl)-7-methoxy-6-sulfamoyloxy-1,2,3,4-tetrahydroisoquinoline), and STX2895 (7-Ethyl-6-sulfamoyloxy-2-(3,4,5-trimethoxybenzyl)-1,2,3,4-tetrahydroisoquinoline) reduced tumour cell growth and induced apoptosis in malignant and benign human Neurofibromatosis 1 (NF1) tumour cells. In earlier NF1 mechanism of action studies we found that in addition to their effects on non-classical hormone-sensitive pathways, STX agents acted on the actin- and myosin-cytoskeleton, as well as PI3Kinase and MTOR signaling pathways. Tumour growth in NF2 cells is affected by different inhibitors from those affecting NF1 growth pathways: specifically, NF2 cells are affected by merlin-downstream pathway inhibitors. Because Merlin, the affected tumour suppressor gene in NF2, is also known to be involved in stabilizing membrane-cytoskeletal complexes, as well as in cell proliferation, and apoptosis, we looked for potentially common mechanisms of action in the agents' effects on NF1 and NF2. We set out to determine whether STX agents could therefore also provide a prospective avenue for treatment of NF2.

METHODS

STX3451 and STX2895 were tested in dose-dependent studies for their effects on growth parameters of malignant and benign NF2 human tumour cell lines in vitro. The mechanisms of action of STX3451 and STX2895 were also analysed.

RESULTS

Although neither of the agents tested affected cell growth or apoptosis in the NF2 tumour cell lines tested through the same mechanisms by which they affect these parameters in NF1 tumour cell lines, both agents disrupted actin- and myosin-based cytoskeletal structures in NF2 cell lines, with subsequent effects on growth and cell death.

CONCLUSIONS

Both STX3451 and STX2895 provide new approaches for inducing cell death and lowering tumour burden in NF2 as well as in NF1, which both have limited treatment options.

EPH receptor signaling as a novel therapeutic target in NF2-deficient meningioma

Background

Meningiomas are the most common primary brain tumor in adults, and somatic loss of the neurofibromatosis 2 (NF2) tumor suppressor gene is a frequent genetic event. There is no effective treatment for tumors that recur or continue to grow despite surgery and/or radiation. Therefore, targeted therapies that either delay tumor progression or cause tumor shrinkage are much needed. Our earlier work established mammalian target of rapamycin complex mTORC1/mTORC2 activation in NF2-deficient meningiomas.

Methods

High-throughput kinome analyses were performed in NF2-null human arachnoidal and meningioma cell lines to identify functional kinome changes upon NF2 loss. Immunoblotting confirmed the activation of kinases and demonstrated effectiveness of drugs to block the activation. Drugs, singly and in combination, were screened in cells for their growth inhibitory activity. Antitumor drug efficacy was tested in an orthotopic meningioma model.

Results

Erythropoietin-producing hepatocellular receptor tyrosine kinases (EPH RTKs), c-KIT, and Src family kinase (SFK) members, which are biological targets of dasatinib, were among the top candidates activated in NF2-null cells. Dasatinib significantly inhibited phospho-EPH receptor A2 (pEPHA2), pEPHB1, c-KIT, and Src/SFK in NF2-null cells, showing no cross-talk with mTORC1/2 signaling. Posttreatment kinome analyses showed minimal adaptive changes. While dasatinib treatment showed some activity, dual mTORC1/2 inhibitor and its combination with dasatinib elicited stronger growth inhibition in meningiomas.

Conclusion

Co-targeting mTORC1/2 and EPH RTK/SFK pathways could be a novel effective treatment strategy for NF2-deficient meningiomas.

The NF2 tumor suppressor merlin interacts with Ras and RasGAP, which may modulate Ras signaling

Inactivation of the tumor suppressor NF2/merlin underlies neurofibromatosis type 2 (NF2) and some sporadic tumors. Previous studies have established that merlin mediates contact inhibition of proliferation; however, the exact mechanisms remain obscure and multiple pathways have been implicated. We have previously reported that merlin inhibits Ras and Rac activity during contact inhibition, but how merlin regulates Ras activity has remained elusive. Here we demonstrate that merlin can directly interact with both Ras and p120RasGAP (also named RasGAP). While merlin does not increase the catalytic activity of RasGAP, the interactions with Ras and RasGAP may fine-tune Ras signaling. In vivo, loss of RasGAP in Schwann cells, unlike the loss of merlin, failed to promote tumorigenic growth in an orthotopic model. Therefore, modulation of Ras signaling through RasGAP likely contributes to, but is not sufficient to account for, merlin’s tumor suppressor activity. Our study provides new insight into the mechanisms of merlin-dependent Ras regulation and may have additional implications for merlin-dependent regulation of other small GTPases.

Efficacy and safety of bevacizumab for vestibular schwannoma in neurofibromatosis type 2: a systematic review and meta-analysis of treatment outcomes

BACKGROUND

Individual evidence suggests that the anti-angiogenic agent bevacizumab may control vestibular schwannoma (VS) growth and promote hearing preservation in patients with neurofibromatosis type 2 (NF2). However, such metadata has yet to be consolidated, as well as its side-effect profile yet to be fully understood. Our aim was to pool systematically-identified metadata in the literature and substantiate the clinical efficacy and safety of bevacizumab with respect to radiographic tumor response, hearing, and treatment outcomes.

METHODS

Searches of seven electronic databases from inception to March 2019 were conducted following PRISMA guidelines. Articles were screened against pre-specified criteria. The incidence of outcomes was then extracted and pooled by random-effects meta-analysis of proportions.

RESULTS

Eight articles reporting 161 NF2 patients with 196 assessable VS met satisfied all criteria. Radiographic response to bevacizumab was partial regression in 41% (95% CI 31-51%), no change in 47% (95% CI 39-55%), and tumor progression in 7% (95% CI 1-15%). In patients with assessable audiometric data, bevacizumab treatment resulted in hearing improvement in 20% (95% CI 9-33%), stability in 69% (95% CI 51-85%) and additional loss in 6% (95% CI 1-15%) Serious bevacizumab toxicity was observed in 17% (95% CI 10-26%). Subsequent surgical intervention was required in 11% (95% CI 2-20%).

CONCLUSIONS

Bevacizumab may arrest both tumor progression and hearing loss in select NF2 patients presenting with VS lesions. However, a considerable proportion of patients are anticipated to experience serious adverse events; correspondingly, judicious use of bevacizumab for symptomatic management of VS in NF2 is recommended.

Role of the Hippo Pathway in Fibrosis and Cancer

The Hippo pathway is the key player in various signaling processes, including organ development and maintenance of tissue homeostasis. This pathway comprises a core kinases module and transcriptional activation module, representing a highly conserved mechanism from Drosophila to vertebrates. The central MST1/2-LATS1/2 kinase cascade in this pathway negatively regulates YAP/TAZ transcription co-activators in a phosphorylation-dependent manner. Nuclear YAP/TAZ bind to transcription factors to stimulate gene expression, contributing to the regenerative potential and regulation of cell growth and death. Recent studies have also highlighted the potential role of Hippo pathway dysfunctions in the pathology of several diseases. Here, we review the functional characteristics of the Hippo pathway in organ fibrosis and tumorigenesis, and discuss its potential as new therapeutic targets.

GPCR-Hippo Signaling in Cancer

The Hippo signaling pathway is involved in tissue size regulation and tumorigenesis. Genetic deletion or aberrant expression of some Hippo pathway genes lead to enhanced cell proliferation, tumorigenesis, and cancer metastasis. Recently, multiple studies have identified a wide range of upstream regulators of the Hippo pathway, including mechanical cues and ligands of G protein-coupled receptors (GPCRs). Through the activation related G proteins and possibly rearrangements of actin cytoskeleton, GPCR signaling can potently modulate the phosphorylation states and activity of YAP and TAZ, two homologous oncogenic transcriptional co-activators, and major effectors of the Hippo pathway. Herein, we summarize the network, regulation, and functions of GPCR-Hippo signaling, and we will also discuss potential anti-cancer therapies targeting GPCR-YAP signaling.

Genomic landscape analyses of reprogrammed cells using integrative and non-integrative methods reveal variable cancer-associated alterations

Recent development of cell reprogramming technologies brought a major hope for future cell therapy applications by the use of these cells or their derivatives. For this purpose, one of the major requirements is the absence of genomic alterations generating a risk of cell transformation. Here we analyzed by microarray-based comparative genomic hybridization human iPSC generated by two non-integrative and one integrative method at pluripotent stage as well as in corresponding teratomas. We show that all iPSC lines exhibit copy number variations (CNV) of several genes deregulated in oncogenesis. These cancer-associated genomic alterations were more pronounced in virally programmed hiPSCs and their derivative teratoma as compared to those found in iPSC generated by mRNA-mediated reprogramming. Bioinformatics analysis showed the involvement of these genes in human leukemia and carcinoma. We conclude that genetic screening should become a standard procedure to ensure that hiPSCs are free from cancer-associated genomic alterations before clinical use.

YAP/TAZ Signaling as a Molecular Link between Fibrosis and Cancer

Tissue fibrosis is a pathological condition that is associated with impaired epithelial repair and excessive deposition of extracellular matrix (ECM). Fibrotic lesions increase the risk of cancer in various tissues, but the mechanism linking fibrosis and cancer is unclear. Yes-associated protein (YAP) and the transcriptional coactivator with PDZ-binding motif (TAZ) are core components of the Hippo pathway, which have multiple biological functions in the development, homeostasis, and regeneration of tissues and organs. YAP/TAZ act as sensors of the structural and mechanical features of the cell microenvironment. Recent studies have shown aberrant YAP/TAZ activation in both fibrosis and cancer in animal models and human tissues. In fibroblasts, ECM stiffness mechanoactivates YAP/TAZ, which promote the production of profibrotic mediators and ECM proteins. This results in tissue stiffness, thus establishing a feed-forward loop of fibroblast activation and tissue fibrosis. In contrast, in epithelial cells, YAP/TAZ are activated by the disruption of cell polarity and increased ECM stiffness in fibrotic tissues, which promotes the proliferation and survival of epithelial cells. YAP/TAZ are also involved in the epithelial–mesenchymal transition (EMT), which contributes to tumor progression and cancer stemness. Importantly, the crosstalk with transforming growth factor (TGF)-β signaling and Wnt signaling is essential for the profibrotic and tumorigenic roles of YAP/TAZ. In this article, we review the latest advances in the pathobiological roles of YAP/TAZ signaling and their function as a molecular link between fibrosis and cancer.

Intra-Orbital Meningioma Causing Loss of Vision in Neurofibromatosis Type 2: Case Series and Management Considerations

Objectives: Little evidence exists regarding the management of orbital meningioma causing vision loss in the setting of neurofibromatosis Type 2 (NF2). We review here our experience with patients at risk for blindness due to intra-orbital meningioma. Design/Setting/Participants/Main Outcome Measures: The charts of patients with NF2 presenting for evaluation of intra-orbital meningioma and vision impairment between 2008 and 2013 were retrospectively reviewed in accordance with institutional IRB policies. Patients with primarily extra-orbital tumors and minimal intra-orbital extension were excluded. Charts were analyzed for the presence and/or imaging progression of intra-orbital tumor, presence of other optic apparatus pathology, presence and/ or progression of vision impairment, and intervention performed (if any). Results: Seven patients with intra-orbital meningioma on MRI and bilateral vision loss and/or unilateral visual impairment due to tumor and contralateral blindness of any etiology were identified. Patients without salvageable vision in either eye were excluded (n = 3). Diagnosis of meningioma was obtained either by biopsy or based on imaging assessment. Conclusion: Conservative management of orbital tumors in NF2 may be preferred in asymptomatic patients but may not be acceptable in patients with progressive visual decline. Radiation is a reasonable option for meningiomas of the orbit and optic nerve sheath. Finally, although the benefit of cranial nerve decompression in NF2 for preservation of facial nerve and hearing has previously been established, the role of optic nerve decompression for preservation of vision in NF2 remains poorly defined.

Craniofacial and oral alterations in patients with Neurofibromatosis 1

ABTSRACT

Neurofibromatosis type 1 (NF1) is one of the most common inherited syndromes. The literature on craniofacial alterations associated with NF1 has been limited and partially contradictory. This review is based on literature search and the results of the clinical study "Craniofacial and Oral Alterations and Speech in patients with Neurofibromatosis 1", carried out at the University of Turku and Turku University Hospital, Finland in 2006-2012. By the end of 2012, a total of 110 NF1 patients, 54 female and 56 male patients, were examined.A part of our results confirms pre-existing understanding, a part is contradictory to previous considerations based mainly on case reports, and some are entirely novel. Specifically, our results confirmed that enlargement the mandibular canal is the most common abnormality of the mandible in patients with NF1. It should be noted, however, that this finding does not require treatment. Caries was not a major problem. In fact, it was less frequent in NF1 patients compared to reference population. These findings abrogate some previous perceptions. Novel findings of our project include periapical cemental dysplasia in females; short jaws, a finding which usually does not affect bite; and immunohistological analysis of oral mucosal abnormalities. Pioneering study on speech showed that various deviations were very common: As many as 94% of the participants showed some alterations.To conclude, the awareness of craniofacial alterations common in NF1would help avoiding unnecessary and even harmful involvement, e.g. of periapical cemental dysplasia or enlarged mandibular canal which do not require treatment.

Radiotherapy in Patients with Vestibular Schwannoma and Neurofibromatosis Type 2: Clinical Results and Review of the Literature

Aims and Background

To evaluate the long-term outcome of patients with vestibular schwannoma (VS) and neurofibromatosis type 2 (NF2) treated with fractionated stereotactic radiotherapy (FSRT) or stereotactic radiosurgery (SRS).

Patients and Methods

Sixteen VS in 14 patients with NF2 were treated with FSRT (n = 14) and SRS (n = 2). Patients with tumor progression and/or progression of clinical symptoms were selected for treatment. For patients treated with FSRT a median total dose of 57.6 Gy was prescribed with a median fractionation of 5 × 1.8 Gy per week. For patients who underwent SRS a median single dose of 17 Gy was prescribed to the 80% isodose.

Results

FSRT and SRS were well tolerated. Local control rate was 94% for a median follow-up time of 131 months; 2- and 5-year progression-free survival were 100%. The probability of maintaining the pretreatment hearing level was 44%. Useful hearing preservation was 33%. Cranial nerve toxicity was moderate. Trigeminal nerve function worsened in 2 patients (12%) and facial nerve function in 3 patients (19%). One patient developed a new tinnitus.

Conclusion

FSRT and SRS are both safe and effective noninvasive and minimally invasive treatment options for patients with VS in the setting of NF2. The long-term local control rates are excellent. Functional hearing preservation is worse in patients with VS and NF2 than in patients with sporadic VS.

Childhood neurofibromatosis type 2 (NF2) and related disorders: from bench to bedside and biologically targeted therapies

Neurofibromatosis type 2 [NF2; MIM # 101000] is an autosomal dominant disorder characterised by the occurrence of vestibular schwannomas (VSs), schwannomas of other cranial, spinal and cutaneous nerves, cranial and spinal meningiomas and/or other central nervous system (CNS) tumours (e.g., ependymomas, astrocytomas). Additional features include early onset cataracts, optic nerve sheath meningiomas, retinal hamartomas, dermal schwannomas (i.e., NF2-plaques), and (few) café-au-lait spots. Clinically, NF2 children fall into two main groups: (1) congenital NF2 - with bilateral VSs detected as early as the first days to months of life, which can be stable/asymptomatic for one-two decades and suddenly progress; and (2) severe pre-pubertal (Wishart type) NF2- with multiple (and rapidly progressive) CNS tumours other-than-VS, which usually present first, years before VSs [vs. the classical adult (Gardner type) NF2, with bilateral VSs presenting in young adulthood, sometimes as the only disease feature]. Some individuals can develop unilateral VS associated with ipsilateral meningiomas or multiple schwannomas localised to one part of the peripheral nervous system [i.e., mosaic NF2] or multiple non-VS, non-intradermal cranial, spinal and peripheral schwannomas (histologically proven) [schwannomatosis]. NF2 is caused by mutations in the NF2 gene at chromosome 22q12.1, which encodes for a protein called merlin or schwannomin, most similar to the exrin-readixin-moesin (ERM) proteins; mosaicNF2 is due to mosaic phenomena for the NF2 gene, whilst schwannomatosis is caused by coupled germ-line and mosaic mutations either in the SMARCB1 gene [SWNTS1; MIM # 162091] or the LZTR1 gene [SWNTS2; MIM # 615670] both falling within the 22q region and the NF2 gene. Data driven from in vitro and animal studies on the merlin pathway [e.g., post-translational and upstream/downstream regulation] allowed biologically targeted treatment strategies [e.g., Lapatinib, Erlotinib, Bevacizumab] aimed to multiple tumour shrinkage and/or regression and tumour arrest of progression with functional improvement.

Wnt/β-catenin signaling pathway inhibits the proliferation and apoptosis of U87 glioma cells via different mechanisms

The Wnt signaling pathway is necessary for the development of the central nervous system and is associated with tumorigenesis in various cancers. However, the mechanism of the Wnt signaling pathway in glioma cells has yet to be elucidated. Small-molecule Wnt modulators such as ICG-001 and AZD2858 were used to inhibit and stimulate the Wnt/β-catenin signaling pathway. Techniques including cell proliferation assay, colony formation assay, Matrigel cell invasion assay, cell cycle assay and Genechip microarray were used. Gene Ontology Enrichment Analysis and Gene Set Enrichment Analysis have enriched many biological processes and signaling pathways. Both the inhibiting and stimulating Wnt/β-catenin signaling pathways could influence the cell cycle, moreover, reduce the proliferation and survival of U87 glioma cells. However, Affymetrix expression microarray indicated that biological processes and networks of signaling pathways between stimulating and inhibiting the Wnt/β-catenin signaling pathway largely differ. We propose that Wnt/β-catenin signaling pathway might prove to be a valuable therapeutic target for glioma.

Diagnostic and Prognostic Relevance of the Cutaneous Manifestations of Neurofibromatosis Type 2

Neurofibromatosis type 2 is an autosomal dominant hereditary disease with complete penetrance. It gives rise to multiple central and peripheral nervous system tumors, ocular alterations, and various types of skin lesion. In general, neither dermatologists nor other specialists have in-depth knowledge of the clinical manifestations of neurofibromatosis type 2. In some cases, this can lead to delayed diagnosis, which can increase morbidity and mortality. We describe the less well known clinical manifestations of NF2, focusing particularly on skin lesions specific to this disease. Identification of these lesions, when present, can facilitate diagnosis.

Neurofibromatosis Type 2

Neurofibromatosis type 2 (NF2) is a rare autosomal dominant disorder (incidence 1:33 000-40 000) characterized by formation of central nervous system tumors, due to mutation in the NF2 gene on chromosome 22q12. Vestibular schwannomas are the hallmark lesion, affecting 95% of individuals and typically occur bilaterally. Schwannomas commonly occur on other nerves intracranially and in the spinal compartment, along with meningiomas, ependymomas, and gliomas. Although histologically benign, tumors are associated with significant morbidity due to multiple problems including hearing and vision loss, gait abnormalities, paralysis, pain, and seizures. Risk of early mortality from brainstem compression and other complications is significant. Severity of disease is higher when NF2 presents during childhood. Children have a more variable presentation, which can be associated with significant delays in recognition of the condition. Careful examination of the skin and eyes can identify important clinical signs of NF2 during childhood, allowing timely initiation of disease-specific surveillance and treatment. Monitoring for complications comprises clinical evaluation, along with functional testing including audiology and serial neuroimaging, which together inform decisions regarding treatment. Evidence for disease-specific medical treatment options is increasing, nevertheless most patients will benefit from multimodal treatment including surgery during their lifetime. Patient enrolment in international natural history and treatment trials offers the best opportunity to accelerate our understanding of the complications and optimal treatment of NF2, with a view to improving outcomes for all affected individuals.

Pediatric neurofibromatosis type 2: clinical and molecular presentation, management of vestibular schwannomas, and hearing rehabilitation

OBJECTIVE

This study aims to describe the clinical and molecular presentation of pediatric neurofibromatosis type 2 (NF2) and the subsequent management of vestibular schwannomas (VS) and hearing rehabilitation.

METHODS

This is a single-center retrospective study of neurofibromatosis type 2 diagnosed before the age of 18 years old from 1997. Natural history of vestibular schwannomas and surgical outcomes were evaluated using volumetric MRI, hearing, and facial nerve assessment. Patients included in chemotherapy protocols were excluded.

RESULTS

From a database of 80 patients followed up for NF2 on a regular basis, 25 patients were eligible (11 sporadic cases, 14 inherited in five families). The mean age at diagnosis was 11.6 years old. The average clinical follow-up was 6.5 years. NF2 mutation was identified in 81 % of the probands. The average growth rate based on the maximum linear diameter (DGR) was 1.68 mm/year (n = 33, average follow-up 4.22 years) and 545 mm³/year in volumetric assessment (VGR) for VS larger than 1 cm (n = 21, average follow-up 3.4 years). In unoperated ears, hearing was stable in about 50 % of ears. The mean change in dB HL was 9.5 dB/year for pure-tone average and 3.5 for speech-recognition threshold (n = 34, 5.5 years 1-12). Eight children required removal through a translabyrinthine approach (mean follow-up was 4.5 years), six patients were operated on for hearing preservation (mean postoperative follow-up 4.3 years). Six patients were eligible for hearing rehabilitation with cochlear implantation (I), and five received placement of an auditory brainstem implant.

CONCLUSION

Early diagnosis and treatment of small growing VS should be carefully discussed considering familial history and possible rehabilitation with a CI.

Immunohistochemical correlates of TP53 somatic mutations in cancer

Despite controversy on the correlation between p53 accumulation and TP53 mutational status, immunohistochemical (IHC) detection of overexpressed protein has long been used as a surrogate method for mutation analysis. The aim of our study was to characterise the IHC expression features of TP53 somatic mutations and define their occurrence in human cancers. A large-scale database analysis was conducted in the IARC TP53 Database (R17); 7878 mutations with IHC features were retrieved representing 60 distinct tumour sites. The majority of the alterations were immunopositive (p <0.001). Sex was known for 4897 mutations showing a female dominance (57.2%) and females carrying negative mutations were significantly younger. TP53 mutations were divided into three IHC groups according to mutation frequency and IHC positivity. Each group had female dominance. Among the IHC groups, significant correlations were observed with age at diagnosis in breast, bladder, liver, haematopoietic system and head & neck cancers. An increased likelihood of false negative IHC associated with rare nonsense mutations was observed in certain tumour sites. Our study demonstrates that p53 immunopositivity largely correlates with TP53 mutational status but expression is absent in certain mutation types.Besides, describing the complex IHC expression of TP53 somatic mutations, our results reveal some caveats for the diagnostic practice.

Neurocutaneous Syndromes and Brain Tumors

The etiology of most childhood cancer remains largely unknown, but is likely attributable to random or induced genetic aberrations in somatic tissue. However, a subset of children develops cancer in the setting of an underlying inheritable condition involving a germline genetic mutation or chromosomal aberration. The term "neurocutaneous syndrome" encompasses a group of multisystem, hereditary disorders that are associated with skin manifestations as well as central and/or peripheral nervous system lesions of variable severity. This review outlines the central nervous system tumors associated with underlying neurocutaneous disorders, including neurofibromatosis type 1, neurofibromatosis type 2, schwannomatosis, tuberous sclerosis complex, Von Hippel Lindau, and nevoid basal cell carcinoma syndrome. Recognizing the presence of an underlying syndrome is critically important to both optimizing clinical care and treatment as well as genetic counseling and monitoring of these affected patients and their families.

A high-throughput kinome screen reveals serum/glucocorticoid-regulated kinase 1 as a therapeutic target for NF2-deficient meningiomas

Meningiomas are the most common primary intracranial adult tumor. All Neurofibromatosis 2 (NF2)-associated meningiomas and ~60% of sporadic meningiomas show loss of NF2 tumor suppressor protein. There are no effective medical therapies for progressive and recurrent meningiomas. Our previous work demonstrated aberrant activation of mTORC1 signaling that led to ongoing clinical trials with rapamycin analogs for NF2 and sporadic meningioma patients. Here we performed a high-throughput kinome screen to identify kinases responsible for mTORC1 pathway activation in NF2-deficient meningioma cells. Among the emerging top candidates were the mTORC2-specific target serum/glucocorticoid-regulated kinase 1 (SGK1) and p21-activated kinase 1 (PAK1). In NF2-deficient meningioma cells, inhibition of SGK1 rescues mTORC1 activation, and SGK1 activation is sensitive to dual mTORC1/2 inhibitor AZD2014, but not to rapamycin. PAK1 inhibition also leads to attenuated mTORC1 but not mTORC2 signaling, suggesting that mTORC2/SGK1 and Rac1/PAK1 pathways are independently responsible for mTORC1 activation in NF2-deficient meningiomas. Using CRISPR-Cas9 genome editing, we generated isogenic human arachnoidal cell lines (ACs), the origin cell type for meningiomas, expressing or lacking NF2. NF2-null CRISPR ACs recapitulate the signaling of NF2-deficient meningioma cells. Interestingly, we observe increased SGK1 transcription and protein expression in NF2-CRISPR ACs and in primary NF2-negative meningioma lines. Moreover, we demonstrate that the dual mTORC1/mTORC2 inhibitor, AZD2014 is superior to rapamycin and PAK inhibitor FRAX597 in blocking proliferation of meningioma cells. Importantly, AZD2014 is currently in use in several clinical trials of cancer. Therefore, we believe that AZD2014 may provide therapeutic advantage over rapalogs for recurrent and progressive meningiomas.