Human Vestibular Schwannomas Research Articles

Identification of Predictive Proteins and Biological Pathways for the Tumorigenicity of Vestibular Schwannoma by Proteomic Profiling.

Vestibular schwannomas (VSs) are benign tumors that account for 8-10% of all intracranial tumors. So far, the tumorigenesis of VS has not been fully elucidated. This study is designed to identify differently expressed proteins involved in VS tumorigenesis. An isobaric tag is used for relative and absolute quantification (iTRAQ) approach to characterize the protein expression profiles from pooled VS tissues (n = 12) and pooled matched normal vestibular tissues (n = 12). A total of 933 differentially expressed proteins are identified between VS and the matched normal vestibular tissues, with 489 being upregulated and 444 being downregulated. Bioinformatics analyses are performed according to Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses. Several of the differentially expressed proteins are validated by western blotting analyses, and upregulation of LGALS1, ANXA1, GRB2, and STAT1 is validated in VS tissue by immunohistochemistry. The study represents the successful application of iTRAQ technology to an investigation of VS. Many of the differentially expressed proteins identified here have not been linked to VS before, and these dysregulated proteins may provide potential biomarkers for human VS diagnosis.

Preclinical assessment of MEK1/2 inhibitors for neurofibromatosis type 2-associated schwannomas reveals differences in efficacy and drug resistance development.

Neurofibromatosis type 2 (NF2) is a genetic tumor-predisposition disorder caused by NF2/merlin tumor suppressor gene inactivation. The hallmark of NF2 is formation of bilateral vestibular schwannomas (VS). Because merlin modulates activity of the Ras/Raf/mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway, we investigated repurposing drugs targeting MEK1 and/or MEK2 as a treatment for NF2-associated schwannomas. Mouse and human merlin-deficient Schwann cell lines (MD-MSC/HSC) were screened against 6 MEK1/2 inhibitors. Efficacious drugs were tested in orthotopic allograft and NF2 transgenic mouse models. Pathway and proteome analyses were conducted. Drug efficacy was examined in primary human VS cells with NF2 mutations and correlated with DNA methylation patterns. Trametinib, PD0325901, and cobimetinib were most effective in reducing MD-MSC/HSC viability. Each decreased phosphorylated pERK1/2 and cyclin D1, increased p27, and induced caspase-3 cleavage in MD-MSCs. Proteomic analysis confirmed cell cycle arrest and activation of pro-apoptotic pathways in trametinib-treated MD-MSCs. The 3 inhibitors slowed allograft growth; however, decreased pERK1/2, cyclin D1, and Ki-67 levels were observed only in PD0325901 and cobimetinib-treated grafts. Tumor burden and average tumor size were reduced in trametinib-treated NF2 transgenic mice; however, tumors did not exhibit reduced pERK1/2 levels. Trametinib and PD0325901 modestly reduced viability of several primary human VS cell cultures with NF2 mutations. DNA methylation analysis of PD0325901-resistant versus -susceptible VS identified genes that could contribute to drug resistance. MEK inhibitors exhibited differences in antitumor efficacy resistance in schwannoma models with possible emergence of trametinib resistance. The results support further investigation of MEK inhibitors in combination with other targeted drugs for NF2 schwannomas.

RETRACTED: Brazilein induces apoptosis and G1/G0 phase cell cycle arrest by up-regulation of miR-133a in human vestibular schwannoma cells

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Given the comments of Dr Elisabeth Bik regarding this article “... the Western blot bands in all 400+ papers are all very regularly spaced and have a smooth appearance in the shape of a dumbbell or tadpole, without any of the usual smudges or stains. All bands are placed on similar looking backgrounds, suggesting they were copy/pasted from other sources, or computer generated”, the journal requested the authors to provide the raw data. However, the authors were not able to fulfil this request and therefore the Editor-in-Chief decided to retract the article.

Fluorescent Detection of Merlin-deficient Schwann Cells and Primary Human Vestibular Schwannoma Cells Using Sodium Fluorescein.

Merlin-deficient Schwann cells (MD-SC) and primary human vestibular schwannoma (VS) cells exhibit selective uptake of sodium-fluorescein (SF), allowing for fluorescent detection and improved visualization of tumor cells, when compared with Schwann cells (SC). SF is a fluorescent compound used for fluorescence-guided resection of gliomas. The utility of SF for VS surgery has not been assessed. Mouse MD-SCs and rat SCs were cultured on 96-well plates at different cell densities and treated with SF at several drug concentrations and durations. Relative fluorescence units (RFU) were measured using a fluorometer to determine optimal treatment parameters in vitro. Subsequently, a four-point Likert scale for fluorescence visualization of pelleted cells was created and validated. Blinded observers rated SF-treated primary human VS and SC cultures, which were developed from deidentified specimens obtained from live and cadaveric donors, respectively. In contrast to SCs that showed low levels of fluorescence, MD-SCs demonstrated dose-dependent increases in RFUs when treated with incremental dosages of SF as well as longer treatment and fluorescent excitation times. In addition, RFUs were higher at greater MD-SC densities. The Likert scale for fluorescence visualization was validated using nine blinded observers and there were excellent inter- and intrarater reliabilities (intraclass coefficients of 0.989 and >0.858, respectively). Using the Likert scale, human VS treated with SF received higher scores than human SCs (p < 0.001). Mouse MD-SC and human VS cells demonstrate preferential uptake of SF when compared with normal primary SCs. Observers detected differences in fluorescence using the validated Likert scale. Further investigations into the utility of SF-guidance in VS surgery are warranted.

Ailanthone Promotes Human Vestibular Schwannoma Cell Apoptosis and Autophagy by Downregulation of miR-21.

Ailanthone (AIL) is a quassinoid isolated from the traditional Chinese medicinal herb Ailanthus altissima. The antitumor activities of AIL have been reported in several cancers. The purpose of the present study was to explore the effect of AIL on vestibular schwannomas (VSs). Various concentrations of AIL (0–1 μM) were used to treat human primary VS cells, and then cell viability, proliferation, apoptosis, and autophagy were assessed. Expression of miR-21 in VS cells was altered by miRNA transfection. The functional actions of AIL on miR-21 dysregulated cells were also assessed. AIL significantly reduced the viability of VS cells, and the IC50 value was 0.48 ± 0.023 μM. In response to 0.6 μM AIL, BrdU+ cell rate and cyclin D1 expression were reduced, apoptotic cell rate was increased, caspase 3 and caspase 9 were cleaved, Beclin-1 and LC3-II were accumulated, and p62 was downregulated. miR-21 was lowly expressed in AIL-treated cells, and AIL-induced apoptosis and autophagy were attenuated by miR-21 overexpression. In addition, AIL downregulated Ras and Raf and deactivated MEK, ERK, mTOR, and p70S6K, while the downregulation and deactivation induced by AIL were reversed by miR-21 overexpression. To conclude, AIL inhibited VS cell proliferation and induced apoptosis and autophagy. The antitumor activities of AIL in VS cells were realized possibly via downregulation of miR-21 and blocking the Ras/Raf/MEK/ERK and mTOR pathways.

Deregulation of the Hippo Pathway Promotes Tumor Cell Proliferation Through YAP Activity in Human Sporadic Vestibular Schwannoma

Vestibular schwannomas (VSs) can cause serious neurological defects including hearing loss and facial paralysis. The aim of this study is to identify whether Hippo signaling could be a potential targetable pathway for clinical treatment in VSs. Gene expression profiling was performed in 10 sporadic VSs and 4 normal nerves to identify aberrant genes expression of the Hippo pathway. Western blotting and immunohistochemical staining were used to examine the expression of Hippo core components in 20 VS samples. Neurofibromatosis type 2 (NF2) gene sequencing was also performed in all tumors using sanger sequencing. Verteporfin, inhibitor of yes-associated protein (YAP)-TEA domain family member, was used to assess the effect ofproliferation inhibition in human primary VS cells and RT4-D6P2T cell line. We found 51 differentially expressed genes of the Hippo pathway between VSs and healthy controls. Unsupervised analysis identified the 2 molecular variants that significantly related with distinct NF2 mutation status. The phosphorylation levels of large tumor suppressor 1 and YAP were significantly decreased in NF2-mutated VSs compared with wild-type VSs and normal nerves. Immunohistochemical staining showed that increased nuclear YAP expression in VSs was positively correlated with high Ki-67 index and low Merlin expression. Verteporfin reduced viability of primary VS cells and RT4-D6P2T cells. Our findings implicate that deregulation of the Hippo pathway as a molecular mechanism of pathogenesis in human VSs, and suggest inhibition of this pathway as a potential treatment strategy.

Computational repositioning and preclinical validation of mifepristone for human vestibular schwannoma

The computational repositioning of existing drugs represents an appealing avenue for identifying effective compounds to treat diseases with no FDA-approved pharmacotherapies. Here we present the largest meta-analysis to date of differential gene expression in human vestibular schwannoma (VS), a debilitating intracranial tumor, and use these data to inform the first application of algorithm-based drug repositioning for this tumor class. We apply an open-source computational drug repositioning platform to gene expression data from 80 patient tumors and identify eight promising FDA-approved drugs with potential for repurposing in VS. Of these eight, mifepristone, a progesterone and glucocorticoid receptor antagonist, consistently and adversely affects the morphology, metabolic activity, and proliferation of primary human VS cells and HEI-193 human schwannoma cells. Mifepristone treatment reduces VS cell viability more significantly than cells derived from patient meningiomas, while healthy human Schwann cells remain unaffected. Our data recommend a Phase II clinical trial of mifepristone in VS.

Combination Therapy with c-Met and Src Inhibitors Induces Caspase-Dependent Apoptosis of Merlin-Deficient Schwann Cells and Suppresses Growth of Schwannoma Cells.

Neurofibromatosis type 2 (NF2) is a nervous system tumor disorder caused by inactivation of the merlin tumor suppressor encoded by the NF2 gene. Bilateral vestibular schwannomas are a diagnostic hallmark of NF2. Mainstream treatment options for NF2-associated tumors have been limited to surgery and radiotherapy; however, off-label uses of targeted molecular therapies are becoming increasingly common. Here, we investigated drugs targeting two kinases activated in NF2-associated schwannomas, c-Met and Src. We demonstrated that merlin-deficient mouse Schwann cells (MD-MSC) treated with the c-Met inhibitor, cabozantinib, or the Src kinase inhibitors, dasatinib and saracatinib, underwent a G1 cell-cycle arrest. However, when MD-MSCs were treated with a combination of cabozantinib and saracatinib, they exhibited caspase-dependent apoptosis. The combination therapy also significantly reduced growth of MD-MSCs in an orthotopic allograft mouse model by greater than 80% of vehicle. Moreover, human vestibular schwannoma cells with NF2 mutations had a 40% decrease in cell viability when treated with cabozantinib and saracatinib together compared with the vehicle control. This study demonstrates that simultaneous inhibition of c-Met and Src signaling in MD-MSCs triggers apoptosis and reveals vulnerable pathways that could be exploited to develop NF2 therapies. Mol Cancer Ther; 16(11); 2387-98. ©2017 AACR.

Tumor-Penetrating Delivery of siRNA against TNF\u03b1 to Human Vestibular Schwannomas

Vestibular schwannoma (VS) is the most common tumor of the cerebellopontine angle, and it typically presents with sensorineural hearing loss. The genomic landscape of schwannoma is complex and many of the molecules implicated in VS pathogenesis represent targets not amenable to antibody-based or small molecule therapeutics. Tumor-targeted delivery of small interfering RNA (siRNA) therapeutics provides a direct and effective means to interrogate targets while minimizing off-target effects. To establish a preclinical model for therapeutic inhibition of putative targets in VS, archived tumor specimens, fresh tumor cells derived from patients with sporadic VS, and an established schwannoma cell line were screened. Nanoparticles directed by the tumor-homing peptide iRGD were selectively taken up by primary VS cultures in vitro via interactions with αvβ3/β5 integrins and neuropilin-1 (NRP-1). Cellular uptake was inhibited by a neutralizing antibody against αv integrin in a dose-dependent manner. When applied to primary VS cultures, iRGD-targeted nanoparticles delivered siRNA directed against TNFα in a receptor-specific fashion to potently silence gene expression and protein secretion. Taken together, our results provide a proof of principle for tumor-targeted, nanoparticle-mediated delivery of siRNA to VS and establish a novel platform for the development and pre-clinical screening of molecular therapeutics against VS.

Ponatinib promotes a G1 cell-cycle arrest of merlin/NF2-deficient human schwann cells.

Neurofibromatosis type 2 (NF2) is a genetic syndrome that predisposes individuals to multiple benign tumors of the central and peripheral nervous systems, including vestibular schwannomas. Currently, there are no FDA approved drug therapies for NF2. Loss of function of merlin encoded by the NF2 tumor suppressor gene leads to activation of multiple mitogenic signaling cascades, including platelet-derived growth factor receptor (PDGFR) and SRC in Schwann cells. The goal of this study was to determine whether ponatinib, an FDA-approved ABL/SRC inhibitor, reduced proliferation and/or survival of merlin-deficient human Schwann cells (HSC). Merlin-deficient HSC had higher levels of phosphorylated PDGFRα/β, and SRC than merlin-expressing HSC. A similar phosphorylation pattern was observed in phospho-protein arrays of human vestibular schwannoma samples compared to normal HSC. Ponatinib reduced merlin-deficient HSC viability in a dose-dependent manner by decreasing phosphorylation of PDGFRα/β, AKT, p70S6K, MEK1/2, ERK1/2 and STAT3. These changes were associated with decreased cyclin D1 and increased p27Kip1levels, leading to a G1 cell-cycle arrest as assessed by Western blotting and flow cytometry. Ponatinib did not modulate ABL, SRC, focal adhesion kinase (FAK), or paxillin phosphorylation levels. These results suggest that ponatinib is a potential therapeutic agent for NF2-associated schwannomas and warrants further in vivo investigation.

Correlation Between Aspirin Intake and Reduced Growth of Human Vestibular Schwannoma

To determine whether people with sporadic vestibular schwannoma (VS) who take aspirin for unrelated medical reasons exhibit less tumor growth than nonaspirin users. We previously demonstrated the efficacy of salicylates in inhibiting VS growth in vitro, corroborating the results of our retrospective clinical study, which found halted VS growth (based on linear tumor measurements) in aspirin users. The current study evaluates this association using more accurate tumor volumetric measurements, and quantifies the degree of frequency-specific, VS-induced hearing loss. Retrospective analysis. Tertiary care hospital. Diagnosed with VS between 1980 and 2012, followed by serial magnetic resonance imaging for at least 1 year. Patient history of aspirin intake; change in VS volume over time of observation; frequency-specific, VS-induced audiometric threshold shifts. Of the 347 patients followed by serial magnetic resonance imaging scans, 86 had sequential scans available for 3D-segmented volumetric analysis for up to 11 years of follow-up (median 53 mo). Twenty-five (29%) had documented history of aspirin intake; 8 (32%) of these demonstrated VS growth. Of the 61 (71%) nonusers, 36 (59%) demonstrated growth. A significant inverse association was found among aspirin users and VS growth: odds ratio 0.32, 95% confidence interval 0.11 to 0.91. VS-induced audiometric thresholds shifts were larger above than below 2000 Hz. Our volumetric analysis of VS growth reaffirms the results of our linear analysis and suggests that aspirin may inhibit VS growth. The audiometric findings are consistent with the previously reported VS-induced predominantly high-frequency sensorineural hearing loss.

Extracellular vesicles derived from human vestibular schwannomas associated with poor hearing damage cochlear cells.

Vestibular schwannoma (VS) is a tumor of the vestibular nerve that transmits balance information from the inner ear to the brain. Sensorineural hearing loss occurs in 95% of patients with these tumors, but the cause of this loss is not well understood. We posit a role of VS-secreted extracellular vesicles (EVs) as a major contributing factor in cochlear nerve damage. Using differential centrifugation, we isolated EVs from VS cell line HEI-193 and primary cultured human VS cells from patients with good hearing or poor hearing. The EVs were characterized using a Nanosight device and transmission electron microscopy and by extracting their RNA content. The EVs' effects on cultured murine spiral ganglion cells and organotypic cochlear cultures were studied using a transwell dual-culture system and by direct labeling of EVs with PKH-67 dye. EV-induced changes in cochlear cells were quantified using confocal immunohistochemistry. Transfection of VS cells with a green fluorescent protein-containing plasmid was confirmed with reverse transcription PCR. Human VS cells, from patients with poor hearing, produced EVs that could damage both cultured murine cochlear sensory cells and neurons. In contrast, EVs derived from VS cells from patients with good hearing did not damage the cultured cochlear cells. This is the first report on EVs derived from VSs and on the capacity of EVs from VSs from patients with hearing loss to selectively damage cochlear cells, thereby identifying a potential novel mechanism of VS-associated sensorineural hearing loss.

Components of the eIF4F complex are potential therapeutic targets for malignant peripheral nerve sheath tumors and vestibular schwannomas.

The eukaryotic initiation factor 4F (eIF4F) complex plays a pivotal role in protein translation initiation; however, its importance in malignant and benign Schwann cell tumors has not been explored, and whether blocking eIF4F function is effective for treating these tumors is not known. Immunostaining was performed on human malignant peripheral nerve sheath tumors (MPNSTs) and vestibular schwannomas (VSs) for eIF4F components. The role of eIF4A and eIF4E in cell growth was assessed by RNA interference. Various natural compounds were screened for their growth-inhibitory activity. Flow cytometry and Western blotting were performed to characterize the action of silvestrol, and its antitumor activity was verified in orthotopic mouse models. MPNSTs and VSs frequently overexpressed eIF4A, eIF4E, and/or eIF4G. Depletion of eIF4A1, eIF4A2, and eIF4E substantially reduced MPNST cell growth. From screening a panel of plant-derived compounds, the eIF4A inhibitor silvestrol was identified as a leading agent with nanomolar IC50 values in MPNST and VS cells. Silvestrol induced G2/M arrest in both NF1-deficient and NF1-expressing MPNST cells and primary VS cells. Silvestrol consistently decreased the levels of multiple cyclins, Aurora A, and mitogenic kinases AKT and ERKs. Silvestrol treatment dramatically suppressed tumor growth in mouse models for NF1(-/-) MPNST and Nf2(-/-) schwannoma. This decreased tumor growth was accompanied by elevated phospho-histone H3 and TUNEL labeling, consistent with G2/M arrest and apoptosis in silvestrol-treated tumor cells. The eIF4F complex is a potential therapeutic target in MPNSTs and VS, and silvestrol may be a promising agent for treating these tumors.

MiR-1 association with cell proliferation inhibition and apoptosis in vestibular schwannoma by targeting VEGFA.

A growing body of research has demonstrated the tumor suppressive function of microRNA (miR)-1 in many cancers. Our study aimed to investigate its role in vestibular schwannoma (VS). We examined miR-1 expression in 95 VS specimens and 79 normal vestibular nerves using quantitative real-time polymerase chain reaction. Moreover, miR-1 mimics, miR-1 inhibitors, and negative control oligonucleotides were transfected into HEI-193 human VS cells to investigate the functional significance of miR-1 expression in this condition at a cellular level. Finally, the role of vascular endothelial growth factor A (VEGFA) in miR-1-mediated HEI-193 cell growth was confirmed. miR-1 levels were significantly reduced in VS specimens compared with normal vestibular nerve tissues (P < 0.001). In addition, low levels of miR-1 were associated with larger tumor volumes. In functional assays, miR-1 suppressed HEI-193 cell proliferation and colony formation, and enhanced apoptosis. VEGFA was verified as a target gene of miR-1, and VEGFA overexpression partially negated the effects of miR-1 on HEI-193 cells. These findings suggest that miR-1 suppresses VS growth by targeting VEGFA, and should be considered as a potential therapeutic target for treatment of this condition.

Secreted Factors from Human Vestibular Schwannomas Can Cause Cochlear Damage.

Vestibular schwannomas (VSs) are the most common tumours of the cerebellopontine angle. Ninety-five percent of people with VS present with sensorineural hearing loss (SNHL); the mechanism of this SNHL is currently unknown. To establish the first model to study the role of VS-secreted factors in causing SNHL, murine cochlear explant cultures were treated with human tumour secretions from thirteen different unilateral, sporadic VSs of subjects demonstrating varied degrees of ipsilateral SNHL. The extent of cochlear explant damage due to secretion application roughly correlated with the subjects’ degree of SNHL. Secretions from tumours associated with most substantial SNHL resulted in most significant hair cell loss and neuronal fibre disorganization. Secretions from VSs associated with good hearing or from healthy human nerves led to either no effect or solely fibre disorganization. Our results are the first to demonstrate that secreted factors from VSs can lead to cochlear damage. Further, we identified tumour necrosis factor alpha (TNFα) as an ototoxic molecule and fibroblast growth factor 2 (FGF2) as an otoprotective molecule in VS secretions. Antibody-mediated TNFα neutralization in VS secretions partially prevented hair cell loss due to the secretions. Taken together, we have identified a new mechanism responsible for SNHL due to VSs.

TR-13 * EFFECTS OF EVEROLIMUS ON MENINGIOMA GROWTH IN PATIENTS WITH NEUROFIBROMATOSIS TYPE 2

BACKGROUND: Vestibular schwannomas (VS) and meningiomas are associated with biallelic loss of NF2, and may arise sporadically or in the context of the tumor predisposition syndrome neurofibromatosis type 2. Loss of NF2 activates the mammalian target of rapamycin (mTOR) pathway, and published in vitro and in vivo data indicate that mTOR inhibition may be effective in the treatment of NF2-deficient VS and meningiomas. Everolimus is an oral inhibitor of mTOR complex 1 (mTORC1) with anti-tumor activity in a variety of tumors. METHODS: We conducted a retrospective review of patients with NF2 and progressive vestibular schwannomas treated with everolimus on our prospective phase II clinical trial (ClinicalTrials.gov NCT01419639). Everolimus was administered at a daily dose of 10 mg in continuous 28-day courses for up to 12 courses. In this retrospective study, we included patients with at least one volumetrically measurable meningioma (>0.5 cc) who received at least six 28-day courses of therapy. Tumor response was assessed with brain MRI every three months using three-dimensional volumetric analysis. RESULTS: Three patients met criteria and had 10 evaluable meningiomas, with a total combined volume of 11.84 cc at baseline (median 1.20 cc, range 0.53–3.00 cc). Median time on therapy was 9 months (range 6–12 months). Total combined meningioma volume remained stable during treatment (-1.8%). Correspondingly, none of the individual tumors analyzed met criteria for volumetric response or progression during the treatment period (range -10% to +9.4%). CONCLUSIONS: Neither objective response nor progression was appreciated in meningiomas patients during a median treatment duration of 6 months. Further clinical studies will be required to determine whether everolimus affects meningioma growth velocity in patients with NF2. To better understand pharmacologic mTOR signaling pathway modulation in human VS and meningiomas in vivo, we are currently conducting a multi-center pharmacodynamic/pharmacokinetic (“phase 0”) study with everolimus (NCT01880749).

Preclinical validation of anti-nuclear factor-kappa B therapy to inhibit human vestibular schwannoma growth

Vestibular schwannomas (VSs), the most common tumors of the cerebellopontine angle, arise from Schwann cells lining the vestibular nerve. Pharmacotherapies against VS are almost non-existent. Although the therapeutic inhibition of inflammatory modulators has been established for other neoplasms, it has not been explored in VS. A bioinformatic network analysis of all genes reported to be differentially expressed in human VS revealed a pro-inflammatory transcription factor nuclear factor-kappa B (NF-κB) as a central molecule in VS pathobiology. Assessed at the transcriptional and translational level, canonical NF-κB complex was aberrantly activated in human VS and derived VS cultures in comparison to control nerves and Schwann cells, respectively. Cultured primary VS cells and VS-derived human cell line HEI-193 were treated with specific NF-κB siRNAs, experimental NF-κB inhibitor BAY11-7082 (BAY11) and clinically relevant NF-κB inhibitor curcumin. Healthy human control Schwann cells from the great auricular nerve were also treated with BAY11 and curcumin to assess toxicity. All three treatments significantly reduced proliferation in primary VS cultures and HEI-193 cells, with siRNA, 5 μM BAY11 and 50 μM curcumin reducing average proliferation (±standard error of mean) to 62.33% ± 10.59%, 14.3 ± 9.7%, and 23.0 ± 20.9% of control primary VS cells, respectively. These treatments also induced substantial cell death. Curcumin, unlike BAY11, also affected primary Schwann cells. This work highlights NF-κB as a key modulator in VS cell proliferation and survival and demonstrates therapeutic efficacy of directly targeting NF-κB in VS.

Nonsteroidal anti-inflammatory medications are cytostatic against human vestibular schwannomas

Vestibular schwannomas (VSs) are the most common tumors of the cerebellopontine angle. Significant clinical need exists for pharmacotherapies against VSs. Motivated by previous findings that immunohistochemical expression of cyclooxygenase 2 (COX-2) correlates with VS growth rate, we investigated the role of COX-2 in VSs and tested COX-2 inhibiting salicylates against VSs. COX-2 was found to be aberrantly expressed in human VS and primary human VS cells in comparison with control human nerve specimens and primary Schwann cells (SCs), respectively. Furthermore, levels of prostaglandin E2, the downstream enzymatic product of COX-2, were correlated with primary VS culture proliferation rate. Because COX-2 inhibiting salicylates such as aspirin are well tolerated and frequently clinically used, we assessed their repurposing for VS. Changes in proliferation, cell death, and cell viability were analyzed in primary VS cultures treated with aspirin, sodium salicylate, or 5-aminosalicylic acid. These drugs neither increased VS cell death nor affected healthy SCs. The cytostatic effect of aspirin in vitro was in concurrence with our previous clinical finding that patients with VS taking aspirin demonstrate reduced tumor growth. Overall, this work suggests that COX-2 is a key modulator in VS cell proliferation and survival and highlights salicylates as promising pharmacotherapies against VS.

Lack of association between human herpesvirus and vestibular schwannoma: analysis of 121 cases.

To assess for the presence of human herpesvirus (HHV) using immunohistochemical and polymerase chain reaction (PCR) assay in surgically excised vestibular schwannoma (VS) samples. Cross-sectional study. A retrospective laboratory-based study of tumors from patients with vestibular schwannoma. Tissue microarrays (TMAs) representing sporadic and NF2-associated VS from 121 patients, as well as appropriate positive and negative controls, were studied. TMA sections were immunostained using antibodies directed against HHV-1, HHV-2, HHV-3, HHV-4, HHV-5, and HHV-8. PCR was used for the detection of all 8 known human herpesviruses. There was no detectable HHV (HHV-1, HHV-2, HHV-3, HHV-4, HHV-5, HHV-8) by immunohistochemistry in any of the 121 cases of sporadic and NF2 cases analyzed. These data were further validated by DNA sequence analyses using PCR in a subset of the VS samples, all of which were found to be negative for all HHV. The data offer no support for an association between HHV and the development of sporadic or NF2-associated VS in humans.

Interplay between VEGF-A and cMET signaling in human vestibular schwannomas and schwann cells

Vestibular schwannoma (VS), the fourth most common intracranial tumor, arises from the Schwann cells of the vestibular nerve. Although several pathways have been independently implicated in VS pathobiology, interactions among these pathways have not been explored in depth. We have investigated the potential cross-talk between hepatocyte growth factor (HGF) and vascular endothelial growth factor-A (VEGF-A) in human VS, an interaction that has been described in other physiological and pathological cell types. We affirmed previous findings that VEGF-A signaling is aberrantly upregulated in VS, and established that expression of HGF and its receptor cMET is also significantly higher in sporadic VS than in healthy nerves. In primary human VS and Schwann cell cultures, we found that VEGF-A and HGF signaling pathways modulate each other. siRNAs targeting cMET decreased both cMET and VEGF-A protein levels, and siRNAs targeting VEGF-A reduced cMET expression. Additionally, siRNA-mediated knockdown of VEGF-A or cMET and pharmacologic inhibition of cMET decreased cellular proliferation in primary human VS cultures. Our data suggest cross-talk between these 2 prominent pathways in VS and highlight the HGF/cMET pathway as an additional important therapeutic target in VS.