Bevacizumab in NF2-related vestibular schwannomas: a nationally coordinated approach to delivery and prospective evaluation

Background: NF2 patients develop multiple nervous system tumors including bilateral vestibular schwannomas (VS). The tumors and their surgical treatment are associated with deafness, neurological disability, and mortality. Medical treatment with bevacizumab has been reported to reduce VS growth and to improve hearing. In addition to evaluating these effects, this study also aimed to determine other important consequences of treatment including patient-reported quality of life and the impact of treatment on surgical VS rates. Methods: Patients treated with bevacizumab underwent serial prospective MRI, audiology, clinical, CTCAE-4.0 adverse events, and NFTI-QOL quality-of-life assessments. Tumor volumetrics were classified according to the REiNs criteria and annual VS surgical rates reviewed. Results: Sixty-one patients (59% male), median age 25 years (range, 10–57), were reviewed. Median follow-up was 23 months (range, 3–53). Partial volumetric tumor response (all tumors) was seen in 39% and 51% had stabilization of previously growing tumors. Age and pretreatment growth rate were predictors of response. Hearing was maintained or improved in 86% of assessable patients. Mean NFTI-QOL scores improved from 12.0 to 10.7 (P < .05). Hypertension was observed in 30% and proteinuria in 16%. Twelve treatment breaks occurred due to adverse events. The rates of VS surgery decreased after the introduction of bevacizumab. Conclusion: Treatment with bevacizumab in this large, UK-wide cohort decreased VS growth rates and improved hearing and quality of life. The potential risk of surgical iatrogenic damage was also reduced due to an associated reduction in VS surgical rates. Ongoing follow-up of this cohort will determine the long-term benefits and risks of bevacizumab treatment.

Cellular schwannomas of the intracranial and intraspinal compartment: morphological and immunological characteristics compared with classical benign schwannomas.

The concept of cellular schwannoma as an unusual benign tumor is well established for peripheral nerves but has never been tested in neurosurgical series. In order to test the validity of this concept in cranial nerves and spinal roots we performed an analysis of the clinical and morphological characteristics of 12 cellular and 166 classical benign schwannomas. Immunohistochemical detection of antigen expression in Schwann cells including proliferating cell nuclear antigen (PCNA) was also performed. This study shows that cellular schwannomas in neurosurgical series manifest at a lower age than the classical benign variant and occur mainly in the spinal roots. Mitotic activity and sinusoidal vessels appear more frequently in cellular schwannomas and constitute with high cellularity, the most valuable criteria separating both entities. The postoperative course in both types of tumors was free of metastases or sarcomatous changes. Immunoexpression of S-100 protein, vimentin, epithelial membrane antigen and glial fibrillary acidic protein is not statistically different between the two variants. In contrast, PCNA is more highly expressed in cellular schwannomas. These These results confirm the concept that cellular schwannomas are a clinico-pathological variant of benign schwannomas and provide significant support for the introduction of this entity in neurosurgical oncology.

Transient ocular motor nerve palsies associated with presumed cranial nerve schwannomas.

BACKGROUND: Cranial nerve schwannomas are radiologically characterized by nodular cranial nerve enhancement on magnetic resonance imaging (MRI). Schwannomas typically present with gradually progressive symptoms, but isolated reports have suggested that schwannomas may cause fluctuating symptoms as well. METHODS: This is a report of ten cases of presumed cranial nerve schwannoma that presented with transient or recurring ocular motor nerve deficits. RESULTS: Schwannomas of the third, fourth, and fifth nerves resulted in fluctuating deficits of all 3 ocular motor nerves. Persistent nodular cranial nerve enhancement was present on sequential MRI studies. Several episodes of transient oculomotor (III) deficts were associated with headaches, mimicking ophthalmoplegic migraine. CONCLUSIONS: Cranial nerve schwannomas may result in relapsing and remitting cranial nerve symptoms.

Intraoral schwannomas: Presentation of a series of 12 cases

Introduction: Schwannomas are benign and not very frequent tumors of the peripheral nerves, derived from the nerve supporting Schwann cells. Study Design: Data were collected on the clinical manifestations (sex, age), location, size and symptonts of the lesions as well as the evolution time and the initial (presumption) diagnosis. Results: Twelve patients were documented, with a mean age of 29,5 ± 12,1 years (range 16-50) and a balanced gender distribution. The mean duration of the lesions was 42,17± 45,3 months. The lesion located in the floor of the mouth was the largest tumor, measuring about 4 cm in maximum diameter, while the average size of the 12 schwannomas was 2.04± 1.1 cm. Conclusion: We present 12 oral schwannomas diagnosed and treated over a period of 10 years. © Medicina Oral S. L. C.I.F. B 96689336 - eISSN: 1989-5488.

Radiological factors related to pre-operative hearing levels in patients with vestibular schwannomas

The pathogenetic mechanism of hearing loss in patients with vestibular schwannomas (VS) remains unclear. Our aim was to determine the radiological and clinical parameters that might be related to hearing. The radiological images and charts of 99 patients were reviewed. Image processing software was used to analyse the maximal tumor diameter in three planes; its volume; its extension cranially, caudally, anteriorly and posteriorly; the width and length of the intrameatal tumor portion, its shape and consistency; and the tumor-fundus distance. These parameters were correlated with the patient's pre-operative hearing range. The degree of hearing correlated significantly with the tumor size, volume and coronal diameter, the degree of intrameatal tumor growth, and the distance between the lateral tumor end and the fundus (p < 0.05). No correlation was found regarding tumor extension, shape and consistency, the presence of hydrocephalus, or the extent of erosion of the internal auditory canal. Loss of hearing in the VS appears to be multifactorial. Determining the radiological parameters related to the hearing level can help to clarify the pathophysiological mechanisms involved.

Factors affecting postoperative cerebrospinal fluid leaks after retrosigmoidal craniotomy for vestibular schwannomas

OBJECT: The aim of this study was to identify patients likely to develop CSF leaks after vestibular schwannoma surgery using a retrospective analysis for the identification of risk factors. METHODS: Between January 2001 and December 2006, 420 patients underwent retrosigmoidal microsurgical tumor removal in a standardized procedure. Of these 420 patients, 363 underwent treatment for the first time, and 27 suffered from recurrent tumors. Twenty-six patients had bilateral tumors due to neurofibromatosis Type 2, and 4 patients had previously undergone radiosurgical treatment. An analysis was performed to examine the incidence of postoperative CSF fistulas in all 4 groups. RESULTS: The incidence of CSF leakage was higher in the tumor recurrence group (11.1%) than in patients undergoing surgery for the first time (4.4%). There were no CSF fistulas in the neurofibromatosis Type 2 group or in patients with preoperative radiosurgical treatment. Tumor size was identified as a possible risk factor in a previous study. CONCLUSIONS: Surgery for recurrent tumors is a significant risk factor for the development of CSF leaks.

The Neurofibromatosis 2 tumor suppressor merlin in cytoskeleton organization and cell cycle regulation

Neurofibromatosis 2 (NF2) is a dominantly inherited disorder, which predisposes to multiple tumours of the nervous system, typically schwannomas and meningiomas. Biallelic inactivation of the NF2 gene occurs both in sporadic and NF2-related schwannomas and in most meningiomas. The NF2 gene product merlin (or schwannomin) is structurally related to the ERM proteins, ezrin, radixin and moesin, which act as molecular linkers between the actin cytoskeleton and the plasma membrane. Merlin is a tumor suppressor that participates in cell cycle regulation. Merlin s phosphorylation status appears to be associated with its tumour suppressor activity, i.e. non-phosphorylated merlin functions as a tumour suppressor, whereas protein phosphorylation results in loss of functional activity. This thesis study was initiated to investigate merlin s role as a tumor suppressor and growth inhibitor. These studies show, that like many other tumor suppressors, also merlin is targeted to the nucleus at some stages of the cell cycle. Merlin s nuclear localization is regulated by cell cycle phase, contact inhibition and adhesion. In addition, a potential nuclear binding partner for merlin was identified, Human Enhancer of Invasion 10 (HEI10), a cyclin B interacting protein. Many tumor suppressors interact with microtubules and this thesis work shows that also merlin colocalizes with microtubules in mitotic structures. Merlin binds microtubules directly, and increases their polymerization in vitro and in vivo. In addition, primary mouse Schwann cells lacking merlin displays disturbed microtubule cytoskeleton. Fourth part of this thesis work began from the notion that PKA phosphorylates an unidentified site from the merlin N-terminus. Our studies show that serine 10 is a target for PKA and modulation of this residue regulates cytoskeletal organization, lamellipodia formation and cell migration. In summary, this thesis work shows that merlin s role is much more versatile than previously thought. It has a yet unidentified role in the nucleus and it participates in the regulation of both microtubules and the actin cytoskeleton. These studies have led to a better understanding of this enigmatic tumor suppressor, which eventually will aid in the design of specific drugs for the NF2 disease.

Functional regulation of the Neurofibromatosis 2 tumor suppressor merlin

Neurofibromatosis 2 (NF2) is an autosomal dominant disorder manifested by the formation of multiple benign tumors of the nervous system. Affected individuals typically develop bilateral vestibular schwannomas which lead to deafness and balance disorders. The syndrome is caused by inactivation of the NF2 tumor suppressor gene, and mutation or loss of the NF2 product, merlin, is sufficient for tumorigenesis in both hereditary and sporadic NF2-associated tumors. Merlin belongs to the band 4.1 superfamily of cytoskeletal proteins, which also contain the related ezrin, radixin, and moesin (ERM) proteins. The ERM members provide a link between the cell cytoskeleton and membrane by connecting membrane-associated proteins to actin filaments. By stabilizing complexes in the cell cortex, the ERMs modulate morphology, growth, and migration of cells. Despite their structural homology, overlapping subcellular distribution, direct molecular association, and partial overlap of molecular interactions, merlin and ezrin exert opposite effects on cell proliferation. Merlin suppresses cell proliferation, whereas ezrin expression is linked to oncogenic activity. We hypothesized that the regions which differ between the proteins might explain merlin s specificity as a tumor suppressor. We therefore analyzed the regions, which are most diverse between merlin and ezrin; the N-terminal tail and the C-terminus. To determine the properties of the C-terminal region, we studied the two most predominant merlin isoforms together with truncation variants similar to those found in patients. We also focused on the evolutionally conserved C-terminal residues, E545-E547, that harbor disease causing mutations in its corresponding DNA sequence. In addition to inhibiting cell proliferation, merlin regulates cytoskeletal organization. The morphogenic properties of merlin may play a role in tumor suppression, since patient-derived tumor cells demonstrate cytoskeletal abnormalities. We analyzed the mechanisms of merlin-induced extension formation and determined that the C-terminal region of amino acids 538-568 is particularly important for the morphogenic activity. We also characterized the role of C-terminal merlin residues in the regulation of proliferation, phosphorylation, and intramolecular associations. In contrast to previous reports, we demonstrated that both merlin isoforms are able to suppress cell proliferation, whereas C-terminally mutated merlin constructs showed reduced growth inhibition. Phosphorylation serves as a mechanism to regulate the tumor suppressive activity of merlin. The C-terminal serine 518 is phosphorylated in response to both p21-activated kinase (PAK) and protein kinase A (PKA), which inactivates the growth inhibitory function of merlin. However, at least three differentially phosphorylated forms of the protein exist. In this study we demonstrated that also the N-terminus of merlin is phosphorylated by AGC kinases, and that both PKA and Akt phosphorylate merlin at serine 10 (S10). We evaluated the impact of this N-terminal tail phosphorylation, and showed that the phosphorylation state of S10 is an important regulator of merlin s ability to modulate cytoskeletal organization but also regulates the stability of the protein. In summary, this study describes the functional effect of merlin specific regions. We demonstrate that both S10 in the N-terminal tail and residues E545-E547 in the C-terminus are essential for merlin activity and function.

Caracterização da marcação imunohistoquímica da protein gene product 9.5 (PGP 9.5) em células astrocitárias

Tese de mestrado, Neurociências, Faculdade de Medicina, Universidade de Lisboa, 2015

S-100 protein: is it useful as a tumour marker in diagnostic immunocytochemistry

A heterogeneous group of 159 tumours was studied for the presence of S-100 protein by the immunoperoxidase technique in order to determine whether this marker may be of value in facilitating immunocytochemical diagnosis. Among cases of melanocytic and pigmented lesions, S-100 was widely distributed and demonstrated the strongest degrees of reactivity. S-100 protein was identified in virtually all nerve sheath tumours such as schwannomas, neurofibromas, myxoid sheath nerve tumour and also in some tumours of controversial histogenesis such as granular cell tumours. The great majority of carcinomas did not express S-100, with only two cases of breast carcinoma displaying focal S-100 staining. In a miscellaneous group of tumours S-100 was demonstrated in chordomas, myoepitheliomas and Wilms' tumour with Schwann cell differentiation. Despite its presence in a wide array of cell types, S-100 protein continues to be an extremely useful marker especially for soft tissue and peripheral nervous system tumours.

Clinicopathologic and immunohistochemical features of oral neurofibroma

Objective. The purposes of this study were to assess clinical, histopathological and immunohistochemical features of 22 oral neurofibromas (NFs) and discuss with previously described literature, addressing the main aspects regarding the differential diagnosis. Materials and methods. Immunohistochemical reactions included S-100, CD34, GLUT-1, EMA, Ki-67, p53 and Collagen IV and histochemical reactions for Alcian blue. Results. Clinically, the preferential location was the maxillary bones, tongue and buccal mucosa. Microscopically, widely spread spindle-shaped cells with scant cytoplasm and elongated nuclei were observed. Immunostaining revealed that the tumor cells weakly expressed GLUT-1, Collagen IV, Ki-67 and p53. They were variably positive for CD34, S-100 protein and membrane epithelial antigen (EMA). Conclusions. The different types of nerve sheath cells observed in the present series reinforce the presence of heterogeneous population in NFs. The strong positivity for S-100 suggests that the lesions were more composed by S-100-positive Schwann cells than other cells. Besides, the high number of CD34-positive cells suggests that this marker can be useful for the differential diagnosis of NFs against PEN, traumatic neuromas and Schwannomas. Finally, the low immunostaining for p53 and Ki-67 may indicate that NFs massively composed by S-100-positive Schwann cells present low potential of aggressiveness and malignant transformation.

Melanotic tumors of the nervous system are characterized by distinct mutational, chromosomal and epigenomic profiles.

Melanotic tumors of the nervous system show overlapping histological characteristics but differ substantially in their biological behavior. In order to achieve a better delineation of such tumors, we performed an in-depth molecular characterization. Eighteen melanocytomas, 12 melanomas, and 14 melanotic and 14 conventional schwannomas (control group) were investigated for methylome patterns (450k array), gene mutations associated with melanotic tumors and copy number variants (CNVs). The methylome fingerprints assigned tumors to entity-specific groups. Methylation groups also showed a substantial overlap with histology-based diagnosis suggesting that they represent true biological entities. On the molecular level, melanotic schwannomas were characterized by a complex karyotype with recurrent monosomy of chromosome 22q and variable whole chromosomal gains and recurrent losses commonly involving chromosomes 1, 17p and 21. Melanocytomas carried GNAQ/11 mutations and presented with CNV involving chromosomes 3 and 6. Melanomas were frequently mutated in the TERT promoter, harbored additional oncogene mutations and showed recurrent chromosomal losses involving chromosomes 9, 10 and 6q, as well as gains of 22q. Together, melanotic nervous system tumors have several distinct mutational and chromosomal alterations and can reliably be distinguished by methylome profiling.