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Purpose: Cochlear implantation (CI) in patients with sensorineural hearing loss caused by a vestibular schwannoma (VS) represents a unique subtype of hearing rehabilitation, as the outcome may be compromised by vestibulocochlear nerve injury as part of the natural VS history or due to iatrogenic trauma induced by surgical tumor removal. This paper aims to review and report contemporary knowledge and practice regarding feasibility and outcomes of simultaneous vestibular schwannoma resection and cochlear implantation to serve as a reference and guide for future surgery and studies., Methods: The current literature was searched systematically according to the PRISMA guidelines and after criteria-based selection, 29 studies were identified, including a total of 86 patients who had undergone surgical resection of a vestibular schwannoma and subsequent cochlear implantation in a single procedure., Results: The postoperative outcomes were reported with a high degree of heterogeneity, hindering a proper meta-analysis. However, pooling those cases with reported speech discrimination outcomes demonstrated mean scores equivalent to moderate-to-high performance. A few cases had no audibility. A positive cochlear nerve test result was not a secure positive predictor of success. Complications were rare., Conclusion: NF2-associated and sporadic VS had good and comparable postoperative outcomes despite significant differences in tumor size, location and surgical approach.

Purpose: To evaluate ophthalmological and molecular findings in eight patients with a clinical diagnosis of neurofibromatosis type 2 (NF2). New pathological mutations are described and variability in the ophthalmic phenotype and NF2 allelic heterogeneity are discussed., Methods: Eye examination was performed in eight NF2 patients, and it included the measurement of the visual acuity, biomicroscopy, dilated fundus examination, color fundus photography, infrared photography, and spectral domain optical coherence tomography (SD-OCT). Molecular analysis was performed with whole-exome sequencing using DNA derived from peripheral blood mononuclear cells from each individual., Results: Ophthalmological features were present in all patients, ranging from subtle retinal alterations identified only using SD-OCT to severe ocular damage present at birth. Six mutations were observed: two patients with stop codon mutation as shown on table 1 and result section, three patients with frameshift mutation as shown on table 1 and result section. Three novel mutations were found among them., Conclusions: It is a descriptive study of a rare disease, with poor previous literature. Clinical and genetic data are shown, reviving the need to further studies to clarify the genotype-phenotype correlations in NF2.

Objective: Neurofibromatosis type 2 (NF2) affects about one in 25,000 to 40,000 people. Most NF2 patients have private loss-of-function mutations scattered along the NF2 gene. Here, we present our NF2 investigation strategy., Material and Methods: We report a comprehensive NF2 mutation analysis of 221 NF2 French patients: 134 unrelated typical NF2 patients fulfilling the Manchester criteria and 87 unrelated patients presenting symptoms that partially fulfilled the Manchester criteria., Results: A NF2 mutation was identified in 56 of the 221 patients, giving a global mutation detection rate of 25%. This rate reached 37% (49/134) for typical NF2 patients fulfilling the Manchester criteria and only 8% (7/87) for patients presenting symptoms suggestive of NF2. Six of these seven patients were under 25 of age. Our approach showed that 77% of NF2 identified variants were detected by coding exons sequencing. Multiplex ligation-dependent probe amplification allowed the identification of restricted rearrangements (23% of NF2 identified variants corresponding to complete deletion or partial deletion/duplication of NF2)., Conclusion: High mutation detection rate can be achieved if well phenotyped NF2 patients are studied with multiple complementary and optimized techniques. NF2 somatic mosaicism detection was improved by frozen tumor samples molecular analysis., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)

Objective: 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., Methods: 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 of proliferation inhibition in human primary VS cells and RT4-D6P2T cell line., Results: 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., Conclusions: 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., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Objective: To investigate 10 candidate single nucleotide polymorphisms (SNPs) in 5 genes (CASP8, XRCC1, WRN, NF2, and BRIP1) to confirm the association between the 5 genes and the meningioma risk in a Chinese population., Methods: We examined 10 candidate SNPs in 5 genes (CASP8, XRCC1, WRN, NF2, and BRIP1) to confirm the association between the 5 genes and the meningioma risk and tumor-related phenotype in 433 individuals, including 215 patients with meningioma and 218 controls., Results: The polymorphisms rs4968451T>G in BRIP1 were significantly associated with the risk of meningioma (TT vs. TG vs. GG additive, P = 0.005; TT+TG vs. GG dominant, P = 0.015; TT/GT+GG recessive, P = 0.034). The significant association was found only in females for BRIP1 rs4968451T>G (TT+TG vs. GG dominant, P = 0.001; TT/GT+GG recessive, P = 0.044). We observed no significant association between genotypes and the meningioma risk for the other 9 SNPs. Through genotype-phenotype analysis, the genotype of BRIP1 rs4968451T>G was also strongly associated with tumor-related phenotypes, including the tumor grade and tumor subtypes. BRIP1 rs4968451T>G was associated with markedly grade I meningioma risk (TT+TG vs. GG dominant, P = 0.008; TT/GT+GG recessive, P = 0.020). In addition, BRIP1 rs4968451T>G was associated with markedly meningothelial and transitional meningioma risk. Furthermore, the genotype of CAPS8, XRCC1, and NF2 was associated with different subtype of meningioma risk., Conclusions: This study indicated a role for BRIP1 gene variations in meningioma and may be informative for future genetic or biological studies of meningioma. These findings will assist in further understanding the genetic cause for meningiomas and guide more effective biological interventions to facilitate meningiomas., (Copyright © 2018. Published by Elsevier Inc.)

Cell adhesion to the extracellular matrix or to surrounding cells plays a key role in cell proliferation and differentiation and is critical for proper tissue homeostasis. An important pathway in adhesion-dependent cell proliferation is the Hippo signaling cascade, which is coregulated by the transcription factors Yes-associated protein 1 (YAP1) and transcriptional coactivator with PDZ-binding motif (TAZ). However, how cells integrate extracellular information at the molecular level to regulate YAP1's nuclear localization is still puzzling. Herein, we investigated the role of β1 integrins in regulating this process. We found that β1 integrin-dependent cell adhesion is critical for supporting cell proliferation in mesenchymal cells both in vivo and in vitro β1 integrin-dependent cell adhesion relied on the relocation of YAP1 to the nucleus after the down-regulation of its phosphorylated state mediated by large tumor suppressor gene 1 and 2 (LATS1/2). We also found that this phenotype relies on β1 integrin-dependent local activation of the small GTPase RAC1 at the plasma membrane to control the activity of P21 (RAC1)-activated kinase (PAK) of group 1. We further report that the regulatory protein merlin (neurofibromin 2, NF2) interacts with both YAP1 and LATS1/2 via its C-terminal moiety and FERM domain, respectively. PAK1-mediated merlin phosphorylation on Ser-518 reduced merlin's interactions with both LATS1/2 and YAP1, resulting in YAP1 dephosphorylation and nuclear shuttling. Our results highlight RAC/PAK1 as major players in YAP1 regulation triggered by cell adhesion., Competing Interests: The authors declare that they have no conflicts of interest with the contents of this article., (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)

Background: The INI1/SMARCB1 gene protein product has been implicated in the direct pathogenesis of schwannomas from patients with one form of schwannomatosis [SWNTS1; MIM # 162091] showing a mosaic pattern of loss of protein expression by immunohistochemistry [93% in familial vs. 55% in sporadic cases]., Aim of Study: To verify whether such INI1/SMARCB1 mosaic pattern could be extended to all schwannomas arising in the sporadic and familial schwannomatoses [i.e. to SMARCB1-related (SWNTS1) or LZTR1-related (SWNTS2) schwannomatosis or to SMARCB1/LZTR1-negative schwannomatosis] and whether it could be involved in classical NF2 or solitary peripheral schwannomas METHODS: We blindly analysed schwannoma samples obtained from a total of 22 patients including (a) 2 patients (2 males; aged 38 and 55 years) affected by non-familial SMARCB1-associated schwannomatosis (SWTNS1); (b) 1 patient (1 female; aged 33 years) affected by familial schwannomatosis (SWTNS1/ SMARCB1 germ line mutations); (c) 5 patients (3 males, 2 females; aged 33 to 35 years) affected by non-familial (sporadic) LZTR1-associated schwannomatosis (SWNTS2); (d) 3 patients (3 males; aged 35 to 47 years) affected by familial schwannomatosis (SWTNS2/ LZTR1 germ line mutations); (e) 2 patients (1 male, 1 female; aged 63 and 49 years, respectively) affected by non-familial schwannomatosis (SWTNS, negative for SMARCB1, LZTR1 and NF2 gene mutations); (f) 4 patients (3 males, 1 females; aged 15 to 24 years) affected by classical NF2 (NF2: harbouring NF2 germ line mutations; and (g) 5 patients (3 males, 2 females; aged 33 to 68 years) who had solitary schwannomas. [follow-up = 15-30 years; negative for constitutional/somatic mutation analysis for the SMARCB1, LZTR1 and NF2 genes] were (blindly) analyzed. The INI1/SMARCB1 immunostaining pattern was regarded as (1) diffuse positive nuclear staining [= retained expression] or (2) mosaic pattern [mixed positive/negative nuclei = loss of expression in a subset of tumour cells]., Results: All solitary peripheral schwannomas and NF2-associated vestibular schwannomas showed diffuse nuclear INI1/SMARCB1 staining in 97-100% of neoplastic cells; schwannomas obtained from all cases of non-familial and familial schwannomatosis and NF2-associated non-vestibular schwannomas showed a mosaic pattern ranging from 10 to 70% of INI1/SMARCB1-positive expression. We did not record a complete lack of nuclear staining., Conclusions: The present data suggests that (a) mosaic loss of immunohistochemical INI1/SMARCB1 expression, despite the interlesional variability, is a reliable marker of schwannomatosis regardless of the involved gene and it might help in the differential diagnosis of schwannomatosis vs. solitary schwannomas and (b) INI1/SMARCB1 expression is not useful in the differential with mosaic NF2, since NF2-associated peripheral schwannomas show the same immunohistochemical pattern.

Background: The genomic features underpinning renal cell carcinoma with sarcomatoid dedifferentiation (sRCC) are not well understood, and at present, there are no specific or effective therapies for sRCC., Objective: To identify genomic alterations in patients with sRCC., Design, Setting, and Participants: We conducted genomic profiling on paired epithelial and sarcomatoid areas of three sRCC cases. Genomic profiling was performed on another 23 sRCC patients harboring diverse epithelial components (total of 26 cases). Genomic profiling was conducted using a hybrid capture DNA next-generation sequencing assay of 236 cancer-related genes plus 19 genes frequently rearranged in cancer. Results were compared with 56 similarly sequenced cases of clear cell RCC (ccRCC) devoid of a sarcomatoid component, and with clear cell, papillary, and chromophobe renal cell carcinoma datasets from The Cancer Genome Atlas. Four additional ccRCC cases underwent whole exome sequencing., Outcome Measurements and Statistical Analysis: Genomic alterations in patients with sRCC and ccRCC were described, and their frequencies were compared using the Fisher exact test., Results and Limitations: Two of three patients with sRCC who underwent genomic profiling of both their epithelial and sarcomatoid components demonstrated identical mutational profiles, and a third case demonstrated commonly disrupted genes. Of the 26 sRCCs, TP53 (42.3%), VHL (34.6%), CDKN2A (26.9%), and NF2 (19.2%) were the most frequently altered genes. NF2 mutations were mutually exclusive with TP53 but not with VHL mutations. Limitations include the small sample size., Conclusions: We found that sRCC contains different driver mutations than ccRCC. The epithelial and sarcomatoid components of sRCC largely contain the same genomic features. On the basis of harboring either TP53 or NF2 mutations, sRCC can be divided into two groups. These findings may have implications for understanding the oncogenesis of sarcomatoid renal tumors and for defining systemic treatment options., Patient Summary: Next-generation sequencing of tumors from patients with sarcomatoid kidney cancer reveals mutations that differ from those in nonsarcomatoid patients. These findings have implications in understanding the pathobiology of sarcomatoid kidney cancer and indicate the need for a different treatment approach in these patients., (Copyright © 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.)

Schwannomas are benign nerve sheath tumors composed of well-differentiated Schwann cells. Other than frequent NF2 (neurofibromatosis type 2) mutations (50%-60%), their molecular pathogenesis is not fully understood. LATS1 and LATS2 are downstream molecules of NF2 and are negative regulators of the yes-associated protein (YAP) oncogene in the Hippo signaling pathway. We assessed mutations of the NF2, LATS1, and LATS2 genes, promoter methylation of LATS1 and LATS2, and expression of YAP and phosphorylated YAP in 82 cases of sporadic schwannomas. Targeted sequencing using the Ion Torrent Proton instrument revealed NF2 mutations in 45 cases (55%), LATS1 mutations in 2 cases (2%), and LATS2 mutations in 1 case (1%) of schwannoma. Methylation-specific polymerase chain reaction showed promoter methylation of LATS1 and LATS2 in 14 cases (17%) and 25 cases (30%), respectively. Overall, 62 cases (76%) had at least 1 alteration in the NF2, LATS1, and/or LATS2 genes. Immunohistochemistry revealed nuclear YAP expression in 18 of 42 cases of schwannoma (43%) and reduced cytoplasmic phosphorylated YAP expression in 15 of 49 cases of schwannoma (31%), all of which had at least 1 alteration in the NF2, LATS1, and/or LATS2 genes. These results suggest that an abnormal Hippo signaling pathway is involved in the pathogenesis of most sporadic schwannomas.

Malignant mesothelioma is a highly aggressive, asbestos-related cancer frequently marked by mutations of both NF2 and CDKN2A. We demonstrate that germline knockout of one allele of each of these genes causes accelerated onset and progression of asbestos-induced malignant mesothelioma compared with asbestos-exposed Nf2(+/-) or wild-type mice. Ascites from some Nf2(+/-);Cdkn2a(+/-) mice exhibited large tumor spheroids, and tail vein injections of malignant mesothelioma cells established from these mice, but not from Nf2(+/-) or wild-type mice, produced numerous tumors in the lung, suggesting increased metastatic potential of tumor cells from Nf2(+/-);Cdkn2a(+/-) mice. Intraperitoneal injections of malignant mesothelioma cells derived from Nf2(+/-);Cdkn2a(+/-) mice into severe combined immunodeficient mice produced tumors that penetrated the diaphragm and pleural cavity and harbored increased cancer stem cells (CSC). Malignant mesothelioma cells from Nf2(+/-);Cdkn2a(+/-) mice stained positively for CSC markers and formed CSC spheroids in vitro more efficiently than counterparts from wild-type mice. Moreover, tumor cells from Nf2(+/-);Cdkn2a(+/-) mice showed elevated c-Met expression/activation, which was partly dependent on p53-mediated regulation of miR-34a and required for tumor migration/invasiveness and maintenance of the CSC population. Collectively, these studies demonstrate in vivo that inactivation of Nf2 and Cdkn2a cooperate to drive the development of highly aggressive malignant mesotheliomas characterized by enhanced tumor spreading capability and the presence of a CSC population associated with p53/miR-34a-dependent activation of c-Met. These findings suggest that cooperativity between losses of Nf2 and Cdkn2a plays a fundamental role in driving the highly aggressive tumorigenic phenotype considered to be a hallmark of malignant mesothelioma., (©2013 AACR.)

Neurofibromatosis (NF) comprises two distinct genetic disorders-neurofibromatosis type 1 and 2 (NF1 and NF2)-in which affected individuals develop both benign and malignant tumours. NF1 results from germline mutations in the NF1 gene that encodes neurofibromin, while NF2 results from germline mutations in the NF2 gene that encodes merlin (or schwannomin). The major tumour types arising in individuals with NF1 include neurofibromas, malignant peripheral nerve sheath tumours, and gliomas, whereas NF2 is characterized by the formation of schwannomas, meningiomas, and ependymomas. With the identification of the NF1 and NF2 genes and the generation of robust preclinical mouse models of NF-associated neoplasms, novel treatments that specifically target the growth control pathways deregulated in these tumours have been discovered, some of which are now being tested in clinical trials in individuals with NF1 and NF2. In this Review, we will highlight the key clinical features of NF1 and NF2 and the advances in future clinical management based on an improved understanding of the function of the NF1 and NF2 genes and the development of small-animal models.

Purpose: In spite of the few clinical studies regarding the occurrence of intracranial meningiomas, their prognosis in neurofibromatosis type 2 (NF2) has not been accurately assessed and their management remains controversial. This study aims to compare NF2 patients with intracranial meningiomas to those without, and consequently to identify prognostic factors in attempt to improve the management of these tumors., Methods: This retrospective study includes a total of 80 NF2 patients followed at Lille Hospital Center between 1987 and 2011. The diagnosis of NF2 was confirmed either because the patient met the Manchester criteria or by the presence of genetic mutation. Clinical, radiological and genetic data were retrospectively recorded and analyzed. Patients underwent annual cranial and spinal MRI. Both location and size of each tumor were reported., Results: The mean follow-up period was 8.8 years (range 1-24 years; SD: ±0.8) and the mean age at diagnosis was 27.2 years (range 6-73 years; SD: ±1.7). Among all patients, 34 harbored intracranial meningiomas. Patients with intracranial meningiomas had a higher number of intracranial schwannomas, spinal tumors and cutaneous tumors (p < 0.05). They underwent more surgical procedures (p < 0.012). Twenty five intracranial meningiomas were surgically removed in 17 patients. The decision to perform surgery was taken in 10 cases for symptomatic tumors and in 15 cases for growing asymptomatic tumors determined by radiology. The histological analysis found a high rate of fibroblastic, transitional or grade 2 meningiomas preferentially located at the cerebri falx., Conclusion: Intracranial meningiomas are common in NF2. They are associated with poor prognosis factors. Clinical and radiological monitoring could lead to early treatment of these tumors both when clinical symptoms are present and in case of proven radiological evolution, and thus trying to maintain a favorable functional prognosis for as long as possible.

Purpose: Neurofibromatosis type 2 (NF2) is a well-studied disease. Although spinal tumors are frequent, many issues concerning their prognosis and management still have to be clarified. The authors studied the clinical impact and radiological progression of spinal tumors in patients with NF2 to determine their prognostic value., Methods: A total of 80 NF2 patients were followed in the Lille University Hospital between 1987 and 2011. Clinical, radiological and genetic data were retrospectively recorded and analyzed. Patients underwent annual cranial and spinal MRI. Both the location and size of each tumor were reported. The diagnosis of NF2 was confirmed either because the patient met the Manchester criteria or by the presence of genetic mutation., Results: The mean follow-up period was 8.8 years (range 1 to 24 years; SD: ±0.8), and the mean age at diagnosis was 27.2 years (range 6 to 73 years; SD: ±1.7). Among all patients, 48 harbored spinal tumors. Twenty of them were symptomatic, and 21 were operated on. Patients with spinal tumors had a lower age at diagnosis (p = 0.02), a higher number of intracranial meningiomas (p = 0.028) and schwannomas (p = 0.03), and more nonsense and frameshift mutations (p = 0.04)., Conclusion: Spinal tumors are common in NF2, and all patients should be regularly monitored by spinal MRI. The presence of spinal tumors seems to be a factor indicating poor prognosis. Clinical and radiological monitoring of spinal tumors could lead to early treatment both when clinical symptoms are present and in case of proven radiological evolution, maintaining a favorable functional prognosis as long as possible.

Neurofibromatosis type 2 (NF2) with onset before the first year of life has been anecdotally reported in the literature. We (a) prospectively (years 1997-2012) followed up three unrelated NF2 children, all harbouring NF2 gene mutations whose onset of disease was before age 1 year, and (b) systematically reviewed published reports on NF2 in the youngest age group (i.e. onset <1 year). The present three children had (1) small (<1 cm), bilateral vestibular schwannomas (VSs) detected (as an incidental finding) at magnetic resonance imaging (MRI) by the age of 4 to 5 months that were asymptomatic for 10 to 14 years, with sudden and rapid (<12 months) progression in two cases at the age of 11 and 15 years, respectively; (2) development of large numbers of skin NF2 plaques mainly in atypical locations (i.e. face, hands, legs and knees), which reverted to normal skin appearance at the time of VSs progression; (3) lens opacities (n = 1) and NF2 retinal changes (n = 2) detected as early as age of 3-4 months; (4) diffuse (asymptomatic) high signal lesions at brain MRI in the periventricular regions (alike cortical dysplasia); and (5) unaffected first-degree relatives who did not harbour NF2 gene abnormalities. This represents the youngest NF2 group with the longest prospective follow-up so far reported. NF2 may present as a congenital form with bilateral VSs presenting as early as the first months of life and with natural history different to that which occurs in classical NF2.

Purpose: To evaluate the mTORC1 (mammalian target of rapamycin complex 1) pathway in meningiomas and to explore mTORC1 as a therapeutic target in meningioma cell lines and mouse models., Experimental Design: Tissue microarrays (53 meningiomas of all WHO grades) were stained for phosphorylated polypeptides of mTOR, Akt, and the mTORC1 targets 4EBP1 and p70S6K, the latter being the consensus marker for mTORC1 activity. Expression of proteins and mRNAs was assessed by Western blotting and real-time PCR in 25 tumors. Cell lines Ben-Men-1 (benign), IOMM-Lee and KT21 (malignant), and pairs of merlin-positive or -negative meningioma cells were used to assess sensitivity toward mTORC1 inhibitors in methyl-tetrazolium and bromodeoxyuridine (BrdUrd) assays. The effect of temsirolimus (20 mg/kg daily) on tumor weight or MRI-estimated tumor volume was tested by treatment of eight nude mice (vs. 7 controls) carrying subcutaneous IOMM-Lee xenografts, or of eight (5) mice xenotransplanted intracranially with IOMM-Lee (KT21) cells in comparison to eight (5) untreated controls., Results: All components of the mTORC1 pathway were expressed and activated in meningiomas, independent of their WHO grade. A significant dosage-dependent growth inhibition by temsirolimus and everolimus was observed in all cell lines. It was slightly diminished by merlin loss. In the orthotopic and subcutaneous xenograft models, temsirolimus treatment resulted in about 70% growth reduction of tumors (P < 0.01), which was paralleled by reduction of Ki67 mitotic index (P < 0.05) and reduction of mTORC1 activity (p70S6K phosphorylation) within the tumors., Conclusion: mTORC1 inhibitors suppress meningioma growth in mouse models, although the present study did not measure survival., (©2012 AACR.)

Neurofibromatosis type 2 patients develop schwannomas, meningiomas and ependymomas resulting from mutations in the tumor suppressor gene, NF2, encoding a membrane-cytoskeleton adapter protein called merlin. Merlin regulates contact inhibition of growth and controls the availability of growth factor receptors at the cell surface. We tested if microtubule-based vesicular trafficking might be a mechanism by which merlin acts. We found that schwannoma cells, containing merlin mutations and constitutive activation of the Rho/Rac family of GTPases, had decreased intracellular vesicular trafficking relative to normal human Schwann cells. In Nf2-/- mouse Schwann (SC4) cells, re-expression of merlin as well as inhibition of Rac or its effector kinases, MLK and p38(SAPK), each increased the velocity of Rab6 positive exocytic vesicles. Conversely, an activated Rac mutant decreased Rab6 vesicle velocity. Vesicle motility assays in isolated squid axoplasm further demonstrated that both mutant merlin and active Rac specifically reduce anterograde microtubule-based transport of vesicles dependent upon the activity of p38(SAPK) kinase. Taken together, our data suggest loss of merlin results in the Rac-dependent decrease of anterograde trafficking of exocytic vesicles, representing a possible mechanism controlling the concentration of growth factor receptors at the cell surface.

Intracranial clear cell meningioma (CCM) is very rare and often has an aggressive clinical course. The predilection site of intracranial CCM in children was cerebellopontine angle where represents challenging tumor resection because of the vicinity of brainstem, vertebral artery, and lower cranial nerve. Therefore, special consideration is required for this tumor.We report two cases with intracranial CCM in a family and reviewed the literature concerning pediatric intracranial CCM. Case 1 is a 4-year-old boy with a tumor at the right posterior fossa. Case 2 is an 8-year-old boy with a left basilar region tumor. Gross total resection and subtotal resection was achieved in case 1 and case 2, respectively. Case 1 had no tumor recurrence at 12 months after the operation. Case 2 received cyber-knife radiosurgery (CKS) after subtotal resection at 4 months, and the residual tumor had gradually shrunk. Comprehensive chromosomal number aberrations in both patients were revealed by array-comparative genomic hybridization, and loss of neurofibromatosis 2 (NF2) gene was the common genetic abnormality in the two patients.To the best of our knowledge, this is the first report concerned two patients with CCM in a family, and the findings in this article suggest that CKS is a safe and effective adjuvant therapy for residual CCM after operation and NF2 gene mutation plays a role in tumorigenesis of pediatric intracranial CCM.

Objective: To determine the expression and clinical significance of Merlin protein in non-small cell lung cancer (NSCLC)., Methods: The expression of Merlin protein in 45 cases of NSCLC and adjacent tissue of NSCLC and normal lung tissue was checked by immunohistochemistry. The relation between the expression of Merlin protein and the multiple factors of pathological type, gender, P-TNM stage, differentiation and lymph node metastasis was analyzed., Results: The expression rates of Merlin protein in NSCLC and normal lung tissue sections were 73.33% and 15.56%, respectively (P<0.05). The expression of Merlin protein was not associated with the pathological type, gender, P-TNM stage, differentiation and lymph node metastasis (P>0.05)., Conclusion: Merlin protein might contribute to the initiation of metastasis of NSCLC.

Drosophila Merlin, an ortholog of the merlin protein encoded by the human Neurofibromatosis 2 (NF2) gene, is important for the regulation of cell proliferation and differentiation in the eye and wing. Also, it has been shown to be involved in male fertility in flies. In the present study, we formation using the comparative light and electron microscopic research of merlin mutants (mer3 and mer4) and ectopic expression of the Mer+ construct. Our work defines specific functions for Merlin in the mitochondria association and aggregation during the nebenkern formation and unfurling mitochondrial derivates during spermatid elongation. Possible role of Merlin as an adaptor protein that can link mitochondria with cytoskeleton is discussed.

Objective: To examine the relationship between the amount of change in size and associated hearing in bilateral vestibular schwannomas (VSs) in persons with neurofibromatosis 2 (NF2)., Study Design: Annual magnetic resonance imaging and audiological examinations were conducted on NF2 patients., Subjects: Fifty-two patients enrolled in the NF2 Natural History Consortium in whom both VSs were untreated. Magnetic resonance imaging and hearing exams were available for at least 2 time points 1 year apart. The 32 males and 20 females had a mean age at diagnosis of 26 years (SD = 18). In 19 (37%) subjects, the NF2 germline mutation could not be identified in the blood (mosaic)., Outcome Measures: Greatest diameter change in tumor size for each of the 2 tumors from first to second evaluation was determined. Differences in amounts of change between the 2 sides and in hearing (4-frequency pure-tone average) were evaluated using multivariate analysis of variance., Results: Overall, the VSs demonstrated significant average growth (p < 0.001), and hearing worsened significantly (p < 0.001) over 1 year. The amount of change in the bigger tumors was not associated with the amount of change in the smaller tumors within each patient. Vestibular schwannoma size changes were not associated with the corresponding hearing changes (Kendall's tau, p = not significant [n.s.])., Conclusion: A significant 1-year change in VS size and hearing occurred in NF2 patients. Clinically, tumor change or hearing deterioration on one VS cannot be used to predict changes in the other VS. This suggests that, although NF2 is a Mendelian disease, the germline genotype-phenotype relationship may resemble that of complex disorders.

Objective: Neurofibromatosis type 2 (NF2) is a common neurocutaneous disorder that exhibits an autosomal dominant inheritance, with a mutation at chromosome 22q12.2. Two forms can be distinguished: the Wishart-phenotype with an early and aggressive course and the Feiling-Gardner-phenotype with a less dramatic presentation. In general, patients present bilateral vestibular schwannomas, meningiomas and neurinomas of the central and peripheral nervous system as well as neurofibromas and gliomas. There is no reported case of pulmonary meningiomas and neurinomas associated with NF2 until now., Patient and Methods: Here, we present a 16-year-old girl with NF-2 associated to CNS and pulmonary tumours and we discuss the case in the backlight of the literature., Results: The reported patient presented a de novo NF2 germline mutation (R341X) and displayed the Wishart-type of NF-2 since she is 11 years old, with a huge anaplastic biparietal falx meningioma and a tentorium meningioma and a tumour-associated parietal mass as well as hypacusis starting at the infant age of 3 years. Multiple cranial and spinal tumours with extra- and intramedullary localization were also found. Moreover, recurrent pulmonary tumours developed and were classified as benign meningiomas and a single neurinoma. No direct evidence concerning a relationship between the pulmonary and cerebral tumours could be drawn., Conclusion: This rare case extends our knowledge of NF2 and also raises interesting questions about the pathogenesis of meningiomas outside the CNS.

Purpose: To report two cases of neurofibromatosis type 2 (NF2) initially presenting with isolated bilateral combined hamartomas of the retina and retinal pigment epithelium (RPE)., Methods: Retrospective observational case reports., Results: Two unrelated children presented to ophthalmology with isolated combined hamartomas of the retina and RPE. Patient one presented to ophthalmology at the age of 2 years; by 4 years, he developed what was thought to be a plexiform neurofibroma and, with more than 6 cafe au lait spots, was diagnosed with neurofibromatosis type 1 (NF1). By the age of 5, he had developed bilateral vestibular schwannomas, and was diagnosed with NF2. Subsequent molecular testing revealed a truncating mutation in exon 13 (c.1396C > T; p.R466X) of the NF2 gene. Patient two presented to ophthalmology at the age of 7 months; by age 6 she had developed two subcutaneous masses on her forehead, a mass in her left lower abdomen, and in her gumline. Despite lack of pathological evidence of neurofibroma upon biopsy, molecular testing was initiated at age 6 and revealed a truncating mutation in exon 8 (c.734delA) of the NF2 gene in the blood., Conclusions: Bilateral combined hamartomas of the retina and retinal pigment epithelium (RPE) in a young child should alert the clinician to the possibility of neurofibromatosis type 2. The recognition of this rare finding as a presenting feature of NF2 can lead to earlier diagnosis, which is vital to appropriate surveillance and possible surgical intervention.

Meningiomas, common tumors arising from arachnoidal cells of the meninges, may occur sporadically, or in association with the inherited disorder, neurofibromatosis 2 (NF2). Most sporadic meningiomas result from NF2 inactivation, resulting in loss of tumor suppressor merlin, implicated in regulating membrane-cytoskeletal organization. To investigate merlin function in an authentic target cell type for NF2 tumor formation, we established primary cultures from genetically-matched meningioma and normal arachnoidal tissues. Our studies revealed novel and distinct cell biological and biochemical properties unique to merlin-deficient meningioma cells compared to merlin-expressing arachnoidal and meningioma cells, and other NF2-deficient cell types. Merlin-deficient meningioma cells displayed cytoskeletal and cell contact defects, altered cell morphology and growth properties, most notably cell senescence, implicating the activation of senescence pathways in limiting benign meningioma growth. Merlin suppression by RNAi in arachnoidal cells replicated merlin-deficient meningioma features, thus establishing these cell systems as disease-relevant models for studying NF2 tumorigenesis.

Objectives: Individuals who develop a unilateral vestibular schwannoma (VS) and other neurogenic tumors are at high risk of having the inherited condition neurofibromatosis Type 2 (NF2). The risk of bilateral disease and transmission risk to offspring are important in surgical planning and counseling. The authors have attempted to resolve these risks., Methods: A large NF2 dataset was interrogated for individuals who had initially presented with a unilateral VS and other tumors before developing bilateral disease, to assess the contralateral and offspring risks., Results: Ninety-six patients with a unilateral VS and additional neurogenic tumors had a bilaterality rate of 48% at 20 years in those initially diagnosed when > 18 years of age and 82% if presenting earlier. Constitutional NF2 mutations were found in blood in 25 (27%) of 92, but 13 (76%) of 17 patients presenting with unilateral VS at < or = 18 years of age. Tumor analysis suggests that the vast majority of the remainder are mosaic for an NF2 mutation., Conclusions: Patients with unilateral VS and other NF2-related tumors who fulfill Manchester criteria have a high risk of developing a contralateral tumor, especially if presenting in childhood. Transmission risks are reduced for offspring, particularly in the older patients who are likely to be mosaic.

This review chapter is a synthesis of the recent literature about pathogenesis of schwannomas with emphasis on vestibular schwannomas (VSs). The cornerstone of cellular transformation and proliferation of Schwann cells toward schwannomas has been attributed to the nonexpression of normal schwannomin/merlin (S/M) by these cells. The understanding of this mechanism has been gained from molecular genetic studies of neurofibromatosis type 2 (NF2) patients, in whom mutations of a tumor suppressor gene (NF2 gene) was clearly identified. S/M is the normal NF2 gene product. Lack of normal S/M protein in the schwannoma cell is due to gene mutation in 50% of sporadic VSs. In the other cases, epigenetic factors or activation of protease cascade contribute to ineffective S/M. The exact interactions of S/M with extracellular matrix, membranous glycoprotein and cytoskeleton are not fully understood. However, it is recognized that these interactions activate several pathways that might regulate cell-cycle process, apoptosis and intercellular interaction. Apart from the involvement of the S/M pathway, the authors review the potential role of other genetic abnormalities and growing factors that are supposed to be involved in the pathogenesis of VS. Understanding the pathways of action and regulation of S/M may provide the basics for identifying potential therapeutic targets, which is of paramount importance for a better management of NF2 patients.

Objective: To describe the prevalence and location of cranial nerve schwannomas, other than bilateral vestibular schwannoma, in patients with neurofibromatosis 2 (NF2). The NF2 Natural History Consortium prospectively gathered cranial magnetic resonance imaging for 83 patients across 3 annual evaluations. The time between the first and last evaluation was approximately 3 years., Results: Forty-two patients (51%) had nonvestibular cranial nerve schwannomas (NVSs). Of these, 25 (60%) also had cranial meningiomas. Twenty-one of those without NVS (25% of 83) had at least 1 meningioma. The average size of the NVS was 0.4 cubic centimeters. Overall, there was no significant change in NVS size from Year 1 to Year 3 or from Year 1 to Year 2. The most common locations of the NVS were occulomotor and trigeminal. A family history of NF2 did not predict NVS location or growth., Conclusion: Nonvestibular cranial nerve schwannoma usually affect cranial nerves III and V, as was the case in our NF2 sample. Fortunately, neuropathies associated with these tumors are rare. In contrast, lower cranial nerve schwannomas, although also rare, are associated with swallowing difficulty, aspiration, and other sequelae.

Introduction: Germline mutations in the NF2 gene are responsible for 80 p.cent of neurofibromatosis type 2 typical cases. Mutations are mainly truncating mutations or deletions, missense mutations having been reported in few cases. An important phenotypic variability is observed among gene carriers. To assess whether the phenotypic variability of neurofibromatosis 2 could be linked to genotype, clinical data of 154 patients whose NF2 germline alteration had been identified in our laboratory have been collected., Methods: A retrospective questionnaire was sent to the physicians in charge of these patients. Statistical analyses regarding genotypic and phenotypic data were performed by comparisons of average values and correlation tests., Results: In French patients, type of mutation was correlated neither with patients' sex, nor with disease occurrence mode (de novo or inherited mutation). Disease associated with missense mutations occurred later, with a less severe symptomatology. Patients with nonsense or frameshift mutations were more frequently affected with meningiomas and spinal tumours, in addition to VIII nerve schwannomas, an observation that underlies the genetic determination of the number and type of NF2-related tumours., Conclusion: Results from the literature as well as from our study tend to show that only few correlations exist between genotype and phenotype in the NF2 disease. It also recognizes that missense mutations have a lower level of evolution, severity and mortality risk. Nonsense and frameshift mutations seem to be associated with a higher number of meningiomas and spinal tumours. Therefore, NF2 gene screening keeps its indications in both typical and moderate forms of the disease. Mutations are responsible of 80 p.cent of typical forms; in moderate forms, identification of a missense mutation seems linked to a lower disease evolution. In any case, assessment and supervision should be identical. Finally, in a small number of cases, the NF2 gene appears to be implicated in clinical forms different from those defined by NIH and it might be of interest to enlarge the clinical features suggestive of the disease.

Objective: The goal of this article was to review concisely what is currently known about the tumorigenesis of vestibular schwannomas., Background: Recent advances in molecular biology have led to a better understanding of the cause of vestibular schwannomas. Mutations in the neurofibromatosis type 2 tumor suppressor gene (NF2) have been identified in these tumors. In addition, the interactions of merlin, the protein product of the NF2 gene, and other cellular proteins are beginning to give us a better idea of NF2 function and the pathogenesis of vestibular schwannomas., Methods: Review of the relevant basic science studies at our institution as well as the basic science and clinical literature., Results: The clinical characteristics of vestibular schwannomas and neurofibromatosis type 2 syndromes are reviewed and related to alterations in the NF2 gene. Studies demonstrating our current understanding of tumor developmental pathways are highlighted. In addition, methods of clinical and genetic screening for neurofibromatosis type 2 disease are outlined. Avenues for the development of potential future research and therapies are discussed., Conclusion: Great strides have been made to identify why vestibular schwannomas develop at the molecular level. Continued research is needed to find targeted therapies with which to treat these tumors.

The WHO classification defines different histological variants of meningiomas. Mutations of the tumor suppressor gene NF2 on 22q have been described in 30% to 60 % of sporadic meningiomas. However, the vast majority of the meningiomas that have been subject to NF2 analysis belong to the most frequent variants like transitional, fibroblastic and meningothelial meningiomas. Within these subtypes, transitional and fibroblastic meningiomas harbor significantly more NF2 mutations than meningothelial meningiomas, indicating molecular subsets of these tumors. To determine whether rare meningioma variants carry NF2 mutations we analyzed 80 tumors. NF2 mutations were detected in 5 (36%) of 14 psammomatous, 1 (11%) of 9 angiomatous, 2 (22%) of 9 clear cell, 1 (33%) of 3 chordoid and 1 (100%) of 1 papillary meningioma. In the single papillary meningioma, 2 different NF2 mutations were observed. No NF2 mutations were found in 33 secretory, 7 microcystic, 2 lymphoplasmacyte-rich, one rhabdoid and one metaplastic meningioma. In the control group of 25 fibroblastic meningiomas, 11 cases were identified to carry an NF2 mutation. These results support the concept of different molecular subgroups of meningiomas which overlap with histological variants.

Germ line and somatic mutations in the neurofibromatosis Type 2 (NF2) tumor suppressor gene predispose individuals to tumors of the nervous system, including schwannomas and meningiomas. Since identification of the NF2 gene more than a decade ago, a large body of information has been collected on the nature and consequences of these alterations in patients with NF2 and in individuals in whom sporadic tumors associated with NF2 develop. The catalog of mutations identified thus far has facilitated extensive genetic analysis, including studies of patients with mosaicism and phenotype-genotype correlations, and has also led to experiments that have begun to unravel the molecular biology of the NF2 gene and its role in tumorigenesis. The authors describe some of the most significant findings in NF2 genetics and biology over the last decade.

The neurofibromatosis type2 (NF2) tumor suppressor gene product, merlin, is structurally related to the ezrin-radixin-moesin (ERM) family of proteins that anchor the actin cytoskeleton to specific membrane proteins and participate in cell signaling. However, the basis of the tumor suppressing activity of merlin is not well understood. Previously, we identified a role of merlin as an inhibitor of the Ras-ERK signaling pathway. Recent studies have suggested that phosphorylation of merlin, as of other ERM proteins, may regulate its function. To determine whether phosphorylation of merlin affects its suppression of Ras-ERK signaling, we generated plasmids expressing full-length merlin with substitutions of serine 518, a potential phosphorylation site. A substitution that mimics constitutive phosphorylation (S518D) abrogated the ability of merlin to suppress effects of the Ras-ERK signaling pathway such as Ras-induced SRE transactivation, Elk-mediated SRE transactivation, Ras-induced ERK phosphorylation and Ras-induced focus formation. On the other hand, an S518A mutant, which mimics nonphosphorylated merlin, acted like wild type merlin. These observations show that mimicking merlin phosphorylation impairs not only growth suppression by merlin but also its inhibitory action on the Ras-ERK signaling pathway.

Malignant mesothelioma has been linked to asbestos exposure and generally has a poor prognosis because it is often diagnosed in advanced stages and is refractory to conventional therapy. Human malignant mesotheliomas accumulate multiple somatic genetic alterations, including inactivation of the NF2 and CDKN2A/ARF tumor suppressor genes. To better understand the significance of NF2 inactivation in malignant mesothelioma and identify tumor suppressor gene alterations that cooperate with NF2 loss of function in malignant mesothelioma pathogenesis, we treated Nf2 (+/-) knockout mice with asbestos to induce malignant mesotheliomas. Asbestos-exposed Nf2 (+/-) mice exhibited markedly accelerated malignant mesothelioma tumor formation compared with asbestos-treated wild-type (WT) littermates. Loss of the WT Nf2 allele, leading to biallelic inactivation, was observed in all nine asbestos-induced malignant mesotheliomas from Nf2 (+/-) mice and in 50% of malignant mesotheliomas from asbestos-exposed WT mice. For a detailed comparison with the murine model, DNA analyses were also done on a series of human malignant mesothelioma samples. Remarkably, similar to human malignant mesotheliomas, tumors from Nf2 (+/-) mice showed frequent homologous deletions of the Cdkn2a/Arf locus and adjacent Cdkn2b tumor suppressor gene, as well as reciprocal inactivation of Tp53 in a subset of tumors that retained the Arf locus. As in the human disease counterpart, malignant mesotheliomas from the Nf2 (+/-) mice also showed frequent activation of Akt kinase, which plays a central role in tumorigenesis and therapeutic resistance. Thus, this murine model of environmental carcinogenesis faithfully recapitulates many of the molecular features of human malignant mesothelioma and has significant implications for the further characterization of malignant mesothelioma pathogenesis and preclinical testing of novel therapeutic modalities.

The role of the NF2 gene in the development of meningiomas has recently been documented; inactivating mutations plus allelic loss at 22q, the site of this gene (at 22q12), have been identified in both sporadic and neurofibromatosis type 2-associated tumors. Although epigenetic inactivation through aberrant CpG island methylation of the NF2 5' flanking region has been documented in schwannoma (another NF2-associated neoplasm), data on participation of this epigenetic modification in meningiomas are not yet widely available. Using methylation-specific PCR (MSP) plus sequencing, we assessed the presence of aberrant promoter NF2 methylation in a series of 88 meningiomas (61 grade I, 24 grade II, and 3 grade III), in which the allelic constitution at 22q and the NF2 mutational status also were determined by RFLP/microsatellite and PCR-SSCP analyses. Chromosome 22 allelic loss, NF2 gene mutation, and aberrant NF2 promoter methylation were detected in 49%, 24%, and 26% of cases, respectively. Aberrant NF2 methylation with loss of heterozygosity (LOH) at 22q was found in five cases, and aberrant methylation with NF2 mutation in another; LOH 22q and the mutation were found in 16 samples. The aberrant methylation of the NF2 gene also was the sole alteration in 15 samples, most of which were from grade I tumors. These results indicate that aberrant NF2 hypermethylation may participate in the development of a significant proportion of sporadic meningiomas, primarily those of grade I.

Hypothesis: The genesis, morphology, and growth characteristics of vestibular schwannomas are determined by genetic alterations which vary gene transcript expression and this transcript expression can be qualitatively and quantitatively evaluated using the SAGE technique. By use of such technique, gene products with tumorigenic potential may be identified, providing insight and targets for future study., Background: Serial analysis of gene expression (SAGE) is a powerful new technique that allows detailed qualitative and quantitative evaluation of cellular gene transcript expression. Tissue in limited quantity (5 x 10 to 2 x 10 cells) may be analyzed by a modified version of SAGE called microSAGE. Application of SAGE or microSAGE to study vestibular schwannoma gene expression has not been previously reported., Methods: Fresh, vestibular schwannoma specimen from an individual with the diagnosis of neurofibromatosis type 2 was attained intraoperatively and maintained in a sealed container at -80degreesC until the time of analysis. The tissue was processed according to the microSAGE protocol, using 180 mg of vestibular schwannoma as starting material., Results: The protocol resulted in the generation and sequencing of a tag library involving 458 tags representing 277 different gene products, including many transcripts known to be expressed in vestibular schwannomas. Several gene products with tumorigenic potential were identified., Conclusions: These data demonstrate that microSAGE is a useful technique to study vestibular schwannoma gene expression. Future studies will include building more comprehensive libraries and comparing libraries from various vestibular schwannoma phenotypes to identify useful diagnostic or prognostic markers, and targets for therapeutic intervention.

The neurofibromatosis 2 (NF2) tumor suppressor gene product, merlin, belongs to the ezrin-radixin-moesin (ERM) subgroup of the Protein 4.1 family, which links cell surface glycoproteins to the actin cytoskeleton. Previous studies have suggested that phosphorylation of merlin, similar to other ERM proteins, may regulate its function. To determine whether merlin phosphorylation has functional consequences for merlin suppression of cell growth and motility, we generated doxycycline-regulatable RT4 schwannoma cell lines that inducibly express full-length merlin with mutations at two potential phosphorylation sites (amino-acid residues S518 and T576). Whereas a mutation at S518 that mimics constitutive phosphorylation (S518D) abrogates the ability of merlin to suppress cell growth and motility, the S518A merlin mutant, which mimics nonphosphorylated merlin, functions equivalently to wild-type merlin. Similar mutations involving T576, the analogous phosphorylation site in ERM proteins important for regulating their function, had no effect. In contrast to other functionally inactive missense merlin mutants, the regulated overexpression of S518D merlin resulted in dramatic changes in cell shape and the elaboration of filopodial extensions. These results provide the first direct demonstration that the S518D merlin mutation, which mimics merlin phosphorylation, impairs not only merlin growth and motility suppression but also leads to an acquisition of a novel phenotype previously ascribed to ERM proteins.

Background: Neurofibromatosis type 2 is a group of tumors caused by loss-of-function mutations of a tumor suppressor gene encoding NF2/merlin. Development of chemotherapeutics for this disease, which often threatens the life of young children, has been hampered by a limited information on the signaling function of NF2. NF2 can inhibit Ras-induced malignant transformation. However, the primary (signaling) target of NF2 in the oncogenic pathway has not been previously identified., Results: Here, using a series of NF2 constructs, we show that NF2 inhibits directly the Rac/CDC42-dependent Ser/Thr kinase PAK1, which is essential for both Ras transformation and neurofibromatosis type 1 (NF1), through two separate domains. A mutant of NF2, that lacks the PAK1-inhibiting domain of 78 amino acids (NF78C, residues 447-524), fails to suppress Ras transformation. Furthermore, PAK1-specific inhibitors CEP-1347 and WR-PAK18 selectively inhibit the growth of NF2-deficient cancer cells, but not NF2-positive cells., Conclusions: These results suggest that PAK1 is essential for the malignant growth of NF2-deficient cells, and that PAK1-blocking drugs could be potentially useful forthe treatment of neurofibromatosis types 2, in addition to Ras-induced cancers and neurofibromatosis type 1.

The Nf2 tumor suppressor gene codes for merlin, a protein whose function has been elusive. We describe a novel interaction between merlin and p21-activated kinase 1 (Pak1), which is dynamic and facilitated upon increased cellular confluence. Merlin inhibits the activation of Pak1, as the loss of merlin expression results in the inappropriate activation of Pak1 under conditions associated with low basal activity. Conversely, the overexpression of merlin in cells that display a high basal activity of Pak1 resulted in the inhibition of Pak1 activation. This inhibitory function of merlin is mediated through its binding to the Pak1 PBD and by inhibiting Pak1 recruitment to focal adhesions. This link provides a possible mechanism for the effect of loss of merlin expression in tumorigenesis.

Context: Schwannomatosis is a newly described form of neurofibromatosis of unclear pathogenesis., Patient and Methods: We studied the NF2 locus on chromosome 22 in 7 tumor specimens resected from a 36-year-old man with schwannomatosis of the right ulnar nerve., Results: Unrelated truncating NF2 gene mutations were detected in 4 tumor specimens. None of the NF2 mutations were present in the blood specimen. Loss of heterozygosity at the NF2 locus was seen in all tumors, and in every case the same allele was lost. Loss of distal chromosome 22 markers was variable. Fluorescence in situ hybridization results were consistent with monosomy 22 in 4 tumors and mitotic recombination or nondisjunction in 1., Conclusions: Molecular analysis of tumor specimens distinguishes schwannomatosis from other forms of neurofibromatosis. Further work is needed to understand the natural history and molecular biology of this condition.

Purpose of Review: Recent clinical and molecular research on neurofibromatosis 2 (NF2) is reviewed, and the implications for clinical practice and research are discussed., Recent Findings: NF2 patients who are treated in specialty centers have a significantly lower risk of mortality than those who are treated in non-specialty centers. Vestibular schwannoma growth rates in NF2 are generally higher in younger people but are highly variable, even among multiple NF2 patients of similar ages in the same family. Radiation therapy is best reserved for NF2 patients who have particularly aggressive tumors, those who are poor surgical risks, those who refuse surgery, or those who are elderly. In-vivo studies have demonstrated that leptomeningeal cell activation of in mice results in leptomeningeal hyperplasia and meningioma formation. In-vitro studies have identified molecules that interact with the product (merlin or schwannomin), some of which (e.g., CD44 and paxillin) may play critical roles in merlin growth regulation., Summary: NF2 patients should be referred to specialty treatment centers for optimal care. Clinical management of multiple patients in NF2 families cannot be based on the expectation of similar vestibular schwannoma growth rates, even when other clinical aspects of disease severity are similar. The availability of accurate mouse models of human NF2-associated tumors and the identification of molecules involved in merlin growth regulation now provide an opportunity to design targeted treatments for schwannomas and meningiomas.

The NF2 tumor suppressor gene, located in chromosome 22q12, is involved in the development of multiple tumors of the nervous system, either associated with neurofibromatosis 2 or sporadic ones, mainly schwannomas and meningiomas. In order to evaluate the role of the NF2 gene in sporadic central nervous system (CNS) tumors, we analyzed NF2 mutations in 26 specimens: 14 meningiomas, 4 schwannomas, 4 metastases, and 4 other histopathological types of neoplasms. Denaturing high performance liquid chromatography (denaturing HPLC) and comparative genomic hybridization on a DNA microarray (microarray- CGH) were used as scanning methods for small mutations and gross rearrangements respectively. Small mutations were identified in six out of seventeen meningiomas and schwannomas, one mutation was novel. Large deletions were detected in six meningiomas. All mutations were predicted to result in truncated protein or in the absence of a large protein domain. No NF2 mutations were found in other histopathological types of CNS tumors. These results provide additional evidence that mutations in the NF2 gene play an important role in the development of sporadic meningiomas and schwannomas. Denaturing HPLC analysis of small mutations and microarray-CGH of large deletions are complementary, fast, and efficient methods for the detection of mutations in tumor tissues.

Individuals with the neurofibromatosis 2 (NF2) inherited tumor predisposition syndrome are prone to the development of nervous system tumors, including schwannomas and meningiomas. The NF2 tumor suppressor protein, merlin or schwannomin, inhibits cell growth and motility as well as affects actin cytoskeleton-mediated processes. Merlin interacts with several proteins that might mediate merlin growth suppression, including hepatocyte growth factor-regulated tyrosine kinase substrate (HRS or HGS). Previously, we demonstrated that regulated overexpression of HRS in RT4 rat schwannoma cells had the same functional consequences as regulated overexpression of merlin. To determine the functional significance of this interaction, we generated a series of HRS truncation mutants and defined the regions of HRS required for merlin binding and HRS growth suppression. The HRS domain required for merlin binding was narrowed to a region (residues 470-497) containing the predicted coiled-coil domain whereas the major domain responsible for HRS growth suppression was distinct (residues 498-550). To determine whether merlin growth suppression required HRS, we demonstrated that merlin inhibited growth in HRS (+/+), but not HRS( -/-) mouse embryonic fibroblast cells. In contrast, HRS could suppress cell growth in the absence of Nf2 expression. These results suggest that merlin growth suppression requires HRS expression and that the binding of merlin to HRS may facilitate its ability to function as a tumor suppressor.

Object: The results of two longitudinal studies of growth rates of vestibular schwannomas (VSs) in patients with neurofibromatosis Type 2 (NF2) differ as to whether VS growth rates decrease or increase with increasing patient age. The authors undertook this study to assess the relationship between VS growth rates and patient age and type of constitutional NF2 mutation; they also examined variability in VS growth rates among multiple patients in families with NF2., Methods: Gadolinium-enhanced magnetic resonance images obtained in 18 patients with inherited NF2 from 11 unrelated families were retrospectively analyzed. The patients had been observed for a median of 4 years. Volumes of the VSs were measured using a two-component box model (intrameatal and extrameatal parts measured separately). Single-strand conformation polymorphism analysis and Southern blot analysis were used to identify constitutional NF2 mutations. Growth rates of the VSs were highly variable, but tended to decrease with increasing patient age both at onset of signs or symptoms of NF2 (r2 = 0.35, p = 0.026) and at diagnosis (r2 = 0.33, p = 0.012). The VS growth rates did not vary significantly with the type of constitutional NF2 mutation or the number of non-VS cerebral or spinal tumors. The VS growth rates were highly variable within families and did not correspond to clinical indices of NF2 disease severity, such as patient age at symptom onset and the number of non-VS cerebral and spinal tumors., Conclusions: The growth rates of VSs in patients with NF2 are highly variable, but tend to decrease with increasing patient age. Clinical treatment of multiple patients in families with NF2 cannot be based on the expectations of similar VS growth rates, even when other clinical aspects of disease severity are similar.

Object: The factors that determine the growth rates of vestibular schwannomas (VSs) in patients with neurofibromatosis Type 2 (NF2) are unknown. The authors undertook this study to determine if clinical factors or type of constitutional NF2 mutation were associated with VS growth rates in cases of NF2., Methods: The authors reviewed serial gadolinium-enhanced magnetic resonance (MR) images of the head and full spine of 37 patients with sporadic NF2 who had been observed over periods ranging from 0.2 to 8 years (median 3.9 years) at a specialized referral clinic for NF2. A box model was used to calculate VS volumes so that tumor growth rates could be estimated. Temperature-gradient gel electrophoresis was used to screen for constitutional NF2 mutations. The VS growth rates tended to decrease with increasing patient age at onset of signs or symptoms (r2 = 0.23, p = 0.003) and at the time the baseline gadolinium-enhanced MR image was obtained (r2 = 0.38, p < 0.001). The authors did not find significant associations between VS growth rates and the number of non-VS cerebral or spinal tumors or different types of constitutional NF2 mutations., Conclusions: There is considerable variability in growth rates of VSs in patients with NF2, but they tend to be higher in patients who are younger at onset of signs or symptoms.

Neurofibromatosis type 2 is caused by mutations in the NF2 tumor suppressor gene. The NF2 gene encodes a 595-aminoacid protein, presumably functioning as a membrane-organizing element. Theoretically, the majority of mutations found in the NF2 gene should lead to a truncated protein product. Using immunoprecipitation with an antibody raised to N-terminal sequences of the NF2 protein, the authors sought to demonstrate the presence of truncated NF2 proteins in tumors. From 17 of 19 tumors (14 meningiomas and five schwannomas), 12 of which have previously been shown to harbor truncating NF2 mutations, wild-type NF2 protein was immunoprecipitated. From two tumors no protein was precipitated. Truncated NF2 proteins were not observed. The authors conclude that mutant NF2 proteins are unstable and undergo accelerated degradation.

Objective: It is hypothesized that transcriptional regulation plays an important role for neurofibromatosis type 2 (NF2) expression in Schwann cells and other cell types. The objective of this study is the isolation and characterization of the transcriptional regulatory elements of the NF2 gene., Study Design and Setting: A bacterial artificial chromosome library and a partial genomic DNA library were used to isolate the human NF2 gene; NF2 promoter-luciferase constructs were generated, and promoter activities were assayed. This study was carried out in a molecular biology laboratory., Results: A bacterial artificial chromosome clone with an approximately 100-kilobase insert containing nearly the entire human NF2 gene has been isolated. An additional 5' NF2 sequence has also been cloned. Transient transfection experiments demonstrate strong promoter activity from the NF2 5' flanking DNA., Conclusions: The NF2 gene is approximately 100 kilobases long. Both positive and negative regulatory elements are present in NF2 5' flanking regions., Significance: Better understanding of the NF2 gene and its regulation will improve molecular diagnostics and ultimately treatment of patients with NF2.

The neurofibromatosis type 2 (NF2) protein, known as merlin or schwannomin, is a tumor suppressor, and the NF2 gene has been found to be mutated in the majority of schwannomas and meningiomas, including both sporadically occurring and familial NF2 cases. Although the development of these tumors depends on the loss of merlin, the presence of tumors lacking detectable NF2 mutations suggests different mechanisms for inactivating merlin. Recent studies have demonstrated cleavage of merlin by calpain, a calcium-dependent neutral cysteine protease, and marked activation of the calpain system resulting in the degradation of merlin in these tumors. Increased turnover of merlin by calpain in some schwannomas and meningiomas exemplifies tumorigenesis linked to the calpain-mediated proteolytic pathway.