Evaluation of NF2 gene deletion in sporadic schwannomas, meningiomas, and ependymomas by chromogenic in situ hybridization

[Molecular genetic features of meningiomas]

Meningioma is the most common primary tumor of the central nervous system. Traditional classification is based on histological properties of tumors and distinguishes different grades of meningioma malignancy. However, knowledge about different molecular mechanisms of tumor provided new data on genetic features of meningiomas. The authors analyze current available data on the main driver mutations, new classifications based on molecular genetic characteristics and potential targets for therapy.

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

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

NF2 Gene Participates in Regulation of the Cell Cycle of Meningiomas by Restoring Spindle Assembly Checkpoint Function and Inhibiting the Binding of Cdc20 Protein to Anaphase Promoting Complex/Cyclosome

BACKGROUND

The neurofibromatosis type 2 (NF2) gene mutation is the leading genetic event in meningiomas, usually accompanied by malignant features. Dysfunction of the spindle assembly checkpoint (SAC) induces tumorigenesis. However, the crosstalk between NF2 and SAC in meningiomas remains unclear.

METHODS

Cell proliferation, invasion, apoptosis, and cell cycle of meningiomas were determined by cell counting kit-8 assay, transwell assay, and flow cytometry, respectively. The expression of SAC in meningioma cells was detected by quantitative real-time polymerase chain reaction and Western blot. The interaction between anaphase promoting complex/cyclosome (APC/C) and cell division cycle 20 (Cdc20) protein in meningioma cells was further explored by co-immunoprecipitation.

RESULTS

We found that the expression of NF2/merlin was low or absent in malignant meningiomas. Overexpression of NF2 suppressed the proliferation and invasion of meningioma cells, prolonged the G₂/M phase, and elevated the expression of SAC proteins at posttranscription. Furthermore, the interaction between APC/C and Cdc20 was inhibited by NF2.

CONCLUSIONS

Our findings suggested that NF2 might restore SAC function by impairing the binding of APC/C and Cdc20, thereby limiting the mitotic rate and inhibiting proliferation of meningiomas.

Management experience of pediatric meningioma in a Mexican reference center

OBJECTIVE

Determine the histopathological and clinical characteristics of patients diagnosed with meningiomas and to establish the frequency of these tumors in the pediatric population Mexican. Determine the NF1/2 frequency in meningioma pediatric.

METHODS

Samples from the histopathology file were reviewed, and from the complete clinical file the following patient data was reviewed: age, gender, diagnosis, diagnosis year, surgical resection, location, tumor size, symptoms, and family background. The frequency of NF1/2 in pediatric meningioma was reviewed in literature.

RESULTS

Forty-four de novo cases were collected from pediatric patients; 19 were female patients and 25 males. The most frequent histological subtype was transitional meningioma. Of all the cases, 75% had a supratentorial localization and 20% had an extramedullary intrarachidian localization. Some clinical manifestations included seizures, paresis, headache, and visual disturbances.

CONCLUSION

There is a low incidence of meningiomas in the pediatric population, more than 70% are Grade I, and they have supratentorial localization.

Utility of copy number variants in the classification of intracranial ependymoma

Ependymomas are neuroepithelial tumors that differentiate along the ependymal cell lineage, a lining of the ventricles of the brain and the central canal of the spinal cord. They are rare in adults, but account for around 9% of brain tumors in children, where they usually have an aggressive course. Efficient stratification could lead to improved care but remains a challenge even in the genomic era. Recent studies proposed a multivariate classification system based on tumor location, age, and broad genomic findings like global patterns of methylation and copy number variants (CNVs). This system shows improved prognostic utility, but is relatively impractical in the routine clinical setting because it necessitates multiple diagnostic tests. We analyzed 13 intracranial grade II and III ependymoma specimens on a DNA microarray to identify discrete CNVs that could support the existing classification. The loss of chr22 and the gain of 5p15.31 were common throughout our cohort (6 and 11 cases, respectively). Other CNVs correlated well with the previously proposed classification system. For example, gains of chr20 were unique to PF-EPN-B tumors of the posterior fossa and may differentiate them from PF-EPN-A. Given the ease of detecting CNVs using multiple, clinically validated methods, these CNVs should be further studied to confirm their diagnostic and prognostic utility, for incorporation into clinical testing algorithms.

Neurofibromatosis type 2 gene mutation and progesterone receptor messenger RNA expression in the pathogenesis of sporadic orbitocranial meningioma

AIM

To investigate neurofibromatosis type 2 (NF2) gene mutation at mRNA levels in sporadic orbitocranial meningioma and its association with progesterone receptor (PR) mRNA expression.

METHODS

This was a case-control study. Thirty-four sporadic meningioma patients with no familial NF2-related meningioma history were recruited. They were interviewed for their obstetric, gynecologic, and contraception history. PR investigation was performed with real-time polymerase chain reaction (PCR). NF2 mutation was investigated using Qbiomarker Somatic Mutation PCR Assay at NF2 mRNA level after its cDNA extraction (four mRNA mutation cytoband coordinates for nucleotide change: c.634C>T/p.Q212, c.655G>A/p.V219M, c.784C>T/p.R262 and c.1228C>T/p. Q410).

RESULTS

After mutation analysis at mRNA level, NF2 gene mutation was found in 35.29% patients. Non-mutation group was strongly associated with exogenous hormonal exposure (non-mutation vs mutation: 95.5% vs 83.3%, P<0.001). PR mRNA was found significantly lower in non-mutation group (P=0.033) which presumed as long term exogenous progesterone exposure. However, mutation group was associated with higher rate of progression to grade II (mutation vs non-mutation, 18.2% vs 5%, P<0.001) and was associated more in fibrous and anaplastic tumor tissue.

CONCLUSION

NF2 mutation-meningioma is associated with higher grade of meningioma. Non NF2 mutation-meningioma is strongly associated with exogenous progesterone exposure and lower PR expression.

TARBP2-Enhanced Resistance during Tamoxifen Treatment in Breast Cancer

Tamoxifen is the most widely used hormone therapy in estrogen receptor-positive (ER+) breast cancer, which accounts for approximately 70% of all breast cancers. Although patients who receive tamoxifen therapy benefit with respect to an improved overall prognosis, resistance and cancer recurrence still occur and remain important clinical challenges. A recent study identified TAR (HIV-1) RNA binding protein 2 (TARBP2) as an oncogene that promotes breast cancer metastasis. In this study, we showed that TARBP2 is overexpressed in hormone therapy-resistant cells and breast cancer tissues, where it enhances tamoxifen resistance. Tamoxifen-induced TARBP2 expression results in the desensitization of ER+ breast cancer cells. Mechanistically, tamoxifen post-transcriptionally stabilizes TARBP2 protein through the downregulation of Merlin, a TARBP2-interacting protein known to enhance its proteasomal degradation. Tamoxifen-induced TARBP2 further stabilizes SOX2 protein to enhance desensitization of breast cancer cells to tamoxifen, while similar to TARBP2, its induction in cancer cells was also observed in metastatic tumor cells. Our results indicate that the TARBP2-SOX2 pathway is upregulated by tamoxifen-mediated Merlin downregulation, which subsequently induces tamoxifen resistance in ER+ breast cancer.

Low Merlin expression and high Survivin labeling index are indicators for poor prognosis in patients with malignant pleural mesothelioma

INTRODUCTION

Alterations of the tumor suppressor Neurofibromatosis type II (NF2) have been reported in about 40% of Malignant pleural mesothelioma (MPM) patients. NF2 (Merlin) deficiency leads to alterations of the Hippo pathway; resulting in activation of the oncogenic Yes Associated Protein-1 (YAP1). Our aim was to investigate the association between these alterations and clinical outcomes.

MATERIAL AND METHODS

Tissue microarrays composed of MPM tumors derived from 2 independent MPM cohorts were employed for this study. Immunohistochemical expression of Merlin, YAP1 and its target genes, Survivin and connective tissue growth factor (CTGF) were assessed in nuclear and cytoplasmic fractions. Cohort 1 was comprised of 145 patients intended to be treated with chemotherapy (CTX) followed by extrapleural pneumonectomy (EPP), thus both pre- and post-CTX tissues were available. Cohort 2 was comprised of 59 patients treated with EPP followed by intraoperative hyperthermic cisplatin and/or adjuvant CTX and/or radiotherapy. Marker expression was quantified by means of labeling index (%) for nuclear Survivin and by H-score for the other markers. The dichotomized marker expression was tested for the association with overall survival (OS) and freedom from recurrence (FFR).

RESULTS

Kaplan-Meier survival curves revealed a significant association between low cytoplasmic Merlin expression in pre-induction CTX tissues of cohort 1 with shorter FFR (p = 0.02) and OS (p = 0.03). The same tendency was observed in the chemotherapy naïve tissues obtained during EPP of cohort 2. Low nuclear Merlin expression in post-CTX tissues (available from cohort 1 only) was associated with shorter FFR (p = 0.04) and OS (p = 0.05). High nuclear Survivin labeling indices in both pre- and post-CTX tissues of cohort 1 was associated with shorter FFR (p = 0.02). In cohort 2, this was associated with both FFR and OS (p = 0.046 and p = 0.002, respectively). In multivariate analysis, low expression of cytoplasmic Merlin remained an independent prognosticator for shorter FFR of cohort 1 [hazard ratio (HR) = 0.5, 95% confidence interval (CI) = 0.3-0.9, p = 0.001] and OS [HR = 0.5, 95% CI = 0.3-1, p = 0.04]. High Survivin labeling index was an independent prognostic factor for shorter FFR in patients from cohort 1 [HR = 3.4, 95% CI = 1.7-6.8, p = 0.006] and shorter OS in patients from cohort 2 [HR = 2.35, 95% CI = 1.27-4.33, p = 0.006].

CONCLUSIONS

Our findings uncover the significance of Merlin protein expression and Survivin labeling index as prognosticators for poor clinical outcome in two independent MPM cohorts. If confirmed, these markers may be used to identify subgroups of patients benefitting from additional treatment.

Expression alterations define unique molecular characteristics of spinal ependymomas

Ependymomas are glial tumors that originate in either intracranial or spinal regions. Although tumors from different regions are histologically similar, they are biologically distinct. We therefore sought to identify molecular characteristics of spinal ependymomas (SEPN) in order to better understand the disease biology of these tumors. Using gene expression profiles of 256 tumor samples, we identified increased expression of 1,866 genes in SEPN when compared to intracranial ependymomas. These genes are mainly related to anterior/posterior pattern specification, response to oxidative stress, glial cell differentiation, DNA repair, and PPAR signalling, and also significantly enriched with cellular senescence genes (P = 5.5 × 10-03). In addition, a high number of significantly down-regulated genes in SEPN are localized to chromosome 22 (81 genes from chr22: 43,325,255 - 135,720,974; FDR = 1.77 × 10-23 and 22 genes from chr22: 324,739 - 32,822,302; FDR = 2.07 × 10-09) including BRD1, EP300, HDAC10, HIRA, HIC2, MKL1, and NF2. Evaluation of NF2 co-expressed genes further confirms the enrichment of chromosome 22 regions. Finally, systematic integration of chromosome 22 genes with interactome and NF2 co-expression data identifies key candidate genes. Our results reveal unique molecular characteristics of SEPN such as altered expression of cellular senescence and chromosome 22 genes.

Expression of merlin, NDRG2, ERBB2, and c-MYC in meningiomas: relationship with tumor grade and recurrence

Meningiomas are common, usually benign tumors of the central nervous system that have a high rate of post-surgical recurrence or regrowth. We determined expression of the proteins merlin, NDRG2, ERBB2, and c-MYC in meningiomas using immunohistochemistry and assessed relationships between protein expression and gender, age, tumor grade, and recurrence or regrowth. The study sample comprised 60 patients, (44 women and 16 men) with a mean age of 53.2 ± 12.7 years. Tumors were classified as grade I (n=48) or grades II and III (n=12). Expression of merlin, NDRG2, ERBB2, and c-MYC was not significantly different statistically with relation to gender, age, or meningioma recurrence or regrowth. Merlin was expressed in 100% of the cases. No statistically significant difference between tumor grade and recurrence or regrowth was identified. Statistically significant differences were identified between the mean age of patients with grade I (54.83 ± 11.60) and grades II and III (46.58 ± 15.08) meningiomas (P=0.043), between strong c-MYC expression and grades II and III (P<0.001), and between partial surgical resection and tumor recurrence or regrowth (P<0.001). These findings reveal the lower mean age among grades II and III meningioma patients than grade I patients, the influence of the protein merlin on tumorigenesis, the association of c-MYC with aggressive meningiomas, and that partial surgical resection is associated with tumor recurrence or regrowth.

Using the neurofibromatosis tumor predisposition syndromes to understand normal nervous system development

Development is a tightly regulated process that involves stem cell self-renewal, differentiation, cell-to-cell communication, apoptosis, and blood vessel formation. These coordinated processes ensure that tissues maintain a size and architecture that is appropriate for normal tissue function. As such, tumors arise when cells acquire genetic mutations that allow them to escape the normal growth constraints. In this regard, the study of tumor predisposition syndromes affords a unique platform to better understand normal development and the process by which normal cells transform into cancers. Herein, we review the processes governing normal brain development, discuss how brain cancer represents a disruption of these normal processes, and highlight insights into both normal development and cancer made possible by the study of tumor predisposition syndromes.

Nf2/Merlin controls spinal cord neural progenitor function in a Rac1/ErbB2-dependent manner

Objective

Individuals with the neurofibromatosis type 2 (NF2) cancer predisposition syndrome develop spinal cord glial tumors (ependymomas) that likely originate from neural progenitor cells. Whereas many spinal ependymomas exhibit indolent behavior, the only treatment option for clinically symptomatic tumors is surgery. In this regard, medical therapies are unfortunately lacking due to an incomplete understanding of the critical growth control pathways that govern the function of spinal cord (SC) neural progenitor cells (NPCs).

Methods

To identify potential therapeutic targets for these tumors, we leveraged primary mouse Nf2-deficient spinal cord neural progenitor cells.

Results

We demonstrate that the Nf2 protein, merlin, negatively regulates spinal neural progenitor cell survival and glial differentiation in an ErbB2-dependent manner, and that NF2-associated spinal ependymomas exhibit increased ErbB2 activation. Moreover, we show that Nf2-deficient SC NPC ErbB2 activation results from Rac1-mediated ErbB2 retention at the plasma membrane.

Significance

Collectively, these findings establish ErbB2 as a potential rational therapeutic target for NF2-associated spinal ependymoma.

Schwannomas and their pathogenesis

Schwannomas may occur spontaneously, or in the context of a familial tumor syndrome such as neurofibromatosis type 2 (NF2), schwannomatosis and Carney's complex. Schwannomas have a variety of morphological appearances, but they behave as World Health Organization (WHO) grade I tumors, and only very rarely undergo malignant transformation. Central to the pathogenesis of these tumors is loss of function of merlin, either by direct genetic change involving the NF2 gene on chromosome 22 or secondarily to merlin inactivation. The genetic pathways and morphological features of schwannomas associated with different genetic syndromes will be discussed. Merlin has multiple functions, including within the nucleus and at the cell membrane, and this review summarizes our current understanding of the mechanisms by which merlin loss is involved in schwannoma pathogenesis, highlighting potential areas for therapeutic intervention.

Intracranial meningiomas and neurofibromatosis type 2

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.

Central nervous system tumors

Central nervous system tumors are the most frequent malignant tumor in children and the main cause of death in this age group after traffic accidents. The current estimates are that one adult in 2500 is a survivor of a brain tumor that occurred during childhood. These tumors are particularly heterogeneous in terms of histology/biology, treatment, and outcome. They share, however, a high risk of neurological and cognitive morbidity due to the disease itself and the treatment modalities (radiotherapy, surgery, and chemotherapy). Diagnosis is frequently delayed because symptoms are usually nonspecific at the beginning of the evolution. Posterior fossa is the most frequent site and the tumors present most frequently with signs of intracranial hypertension. Supratentorial tumors are more frequent in infants and in adolescents; seizures are not uncommon, especially for benign tumors. When adjuvant treatment is needed, radiotherapy is usually the mainstay apart from some histologies where chemotherapy may be sufficient: low-grade gliomas, desmoplastic medulloblastomas, malignant glial tumors in infants. Multidisciplinary care is best performed in tertiary care centers and should include early rehabilitation programs soon after surgery.

Loss of tumor suppressor Merlin in advanced breast cancer is due to post-translational regulation

Unlike malignancies of the nervous system, there have been no mutations identified in Merlin in breast cancer. As such, the role of the tumor suppressor, Merlin, has not been investigated in breast cancer. We assessed Merlin expression in breast cancer tissues by immunohistochemistry and by real-time PCR. The expression of Merlin protein (assessed immunohistochemically) was significantly decreased in breast cancer tissues (although the transcript levels were comparable) simultaneous with increased expression of the tumor-promoting protein, osteopontin (OPN). We further demonstrate that the loss of Merlin in breast cancer is brought about, in part, due to OPN-initiated Akt-mediated phosphorylation of Merlin leading to its proteasomal degradation. Restoring expression of Merlin resulted in reduced malignant attributes of breast cancer, characterized by reduced invasion, migration, motility, and impeded tumor (xenograft) growth in immunocompromised mice. The possibility of developing a model using the relationship between OPN and Merlin was tested with a logistic regression model applied to immunohistochemistry data. This identified consistent loss of immunohistochemical expression of Merlin in breast tumor tissues. Thus, we demonstrate for the first time a role for Merlin in impeding breast malignancy, identify a novel mechanism for the loss of Merlin protein in breast cancer, and have developed a discriminatory model using Merlin and OPN expression in breast tumor tissues.

Empirical development of improved diagnostic criteria for neurofibromatosis 2

PURPOSE

Four sets of clinical diagnostic criteria have been proposed for neurofibromatosis 2, but all have low sensitivity at the time of initial clinical assessment for the disease among patients with a negative family history who do not present with bilateral vestibular schwannomas. We have empirically developed and tested an improved set of diagnostic criteria that uses current understanding of the natural history and genetic characteristics of neurofibromatosis 2 to increase sensitivity while maintaining very high specificity.

METHODS

We used data from the UK Neurofibromatosis 2 Registry and Kaplan-Meier curves to estimate frequencies of clinical features at various ages among patients with or without unequivocal neurofibromatosis 2. On the basis of this analysis, we developed the Baser criteria, a new diagnostic system that incorporates genetic testing and gives more weight to the most characteristic features and to those that occur before 30 years of age.

RESULTS

In an independent validation subset of patients with unequivocal neurofibromatosis 2, the Baser criteria increased diagnostic sensitivity to 79% (9-15% greater than previous sets of criteria) while maintaining 100% specificity at the age at onset of the first characteristic sign of neurofibromatosis 2.

CONCLUSION

The Baser criteria permit early diagnosis in a greater proportion of patients with neurofibromatosis 2 than previous sets of diagnostic criteria.

CpG island hypermethylation of the neurofibromatosis type 2 (NF2) gene is rare in sporadic vestibular schwannomas

AIMS

Loss of both wild-type copies of the neurofibromatosis type 2 (NF2) gene is found in both sporadic and neurofibromatosis type 2-associated vestibular schwannomas (VS). Previous studies have identified a subset of VS with no loss or mutation of NF2. We hypothesized that methylation of NF2 resulting in gene silencing may play a role in such tumours.

METHODS

Forty sporadic VS were analysed by array comparative genomic hybridization using 1 Mb whole genome and chromosome 22 tile path arrays. The NF2 genes were sequenced and methylation of NF2 examined by pyrosequencing.

RESULTS

Monosomy 22 was the only recurrent change found. Twelve tumours had NF2 mutations. Eight tumours had complete loss of wild-type NF2, four had one mutated and one wild-type allele, 11 had only one wild-type allele and 17 showed no abnormalities. Methylation analysis showed low-level methylation in four tumours at a limited number of CpGs. No high-level methylation was found.

CONCLUSIONS

This study shows that a significant proportion of sporadic VS (>40%) have unmethylated wild-type NF2 genes. This indicates that other mechanisms, yet to be identified, are operative in the oncogenesis of these VSs.

The genetic and epigenetic basis of ependymoma

INTRODUCTION

Although ependymoma is the third most common pediatric brain tumor, we know little about the genetic/epigenetic basis of its initiation, maintenance, or progression. This is due in part to the heterogeneity of the disease, as well as the small sample size of the cohorts analyzed in most studies.

METHODS

Many of the genetic aberrations identified to date are large genomic regions, making the differentiation between passenger and driver genes difficult. The finding of a balanced karyotype in a significant subset of pediatric posterior fossa ependymomas increases the difficulty of identifying targets for rationale therapy.

CONCLUSION

The paucity of in vitro and in vivo model systems for ependymoma compound the difficulties outlined above. In this review, we discuss the published literature on ependymoma genetics and epigenetics and discuss possible future directions for the field.

Intracranial meningiomas in children: ten-year experience

Meningiomas are central nervous system neoplasms derived from arachnoid cap cells. They are the second most common brain tumors after gliomas, but are rare in children. Furthermore, meningiomas exhibit different behavior in this age group. From 1997-2007, 7 children with brain meningiomas were treated at the Department of Neurosurgery, Brazilian National Cancer Institute, Rio de Janeiro, Brazil. They represented 2.7% of all brain meningiomas, and 2.1% of all brain tumors, in children followed during this period at our institution. There were 4 boys, and the mean age at diagnosis was 7.3 years. Headaches, seizures, and motor deficits were the most frequent signs at presentation. All patients underwent surgery, and total resection was achieved in 6 of 7 patients. Most lesions were World Health Organization class I meningiomas. There were no deaths, and patients were asymptomatic or demonstrated mild motor or sensory signs at follow-up. In conclusion, meningiomas are rare in the pediatric population. Most of the lesions are low-grade, and the prognosis in this setting is good.