Inactivation patterns of NF2 and DAL-1/4.1B (EPB41L3) in sporadic meningioma

Crispr/Cas-based modeling of NF2 loss in meningioma cells

BACKGROUND

Alterations of the neurofibromatosis type 2 gene (NF2) occur in more than fifty percent of sporadic meningiomas. Meningiomas develop frequently in the setting of the hereditary tumor syndrome NF2. Investigation of potential drug-based treatment options has been limited by the lack of appropriate in vitro and in vivo models.

NEW METHODS

Using Crispr/Cas gene editing, of the malignant meningioma cell line IOMM-Lee, we generated a pair of cell clones characterized by either stable knockout of NF2 and loss of the protein product merlin or retained merlin protein (transfected control without gRNA).

RESULTS

IOMM-Lee cells lacking NF2 showed reduced apoptosis and formed bigger colonies compared to control IOMM-Lee cells. Treatment of non-transfected IOMM-Lee cells with the focal adhesion kinase (FAK) inhibitor GSK2256098 resulted in reduced colony sizes. Orthotopic mouse xenografts showed the formation of convexity tumors typical for meningiomas with NF2-depleted and control cells.

COMPARISON WITH EXISTING METHODS

No orthotopic meningioma models with genetically-engineered cell pairs are available so far.

CONCLUSION

Our model based on Crispr/Cas-based gene editing provides paired meningioma cells suitable to study functional consequences and therapeutic accessibility of NF2/merlin loss.

Erythrocyte membrane protein band 4.1-like 3 inhibits osteosarcoma cell invasion through regulation of Snai1-induced epithelial-to-mesenchymal transition

Erythrocyte membrane protein band 4.1-like 3 (EPB41L3) is an important membrane skeletal protein that may interact with numerous membrane proteins. Loss of EPB41L3 is reported in multiple cancer types, and it is originally identified as a tumor suppressor. In this study, through analyzing expression profiling retrieved from the Gene Expression Omnibus (GEO) dataset, we find that EPB41L3 is upregulated in primary osteosarcoma (OS) and osteosarcoma cell lines. Importantly, EPB41L3 may promote osteosarcoma cell proliferation and suppress osteosarcoma cell migration and invasion. Reduced EPB41L3 leads to a decrease of E-cadherin as well as an increase of N-cadherin and Vimentin, implying a prominent epithelial-to-mesenchymal transition. Furthermore, we demonstrate that EPB41L3 inhibits the epithelial-to-mesenchymal transition through destabilizing the Snai1 protein, one of the most important transcription factors of the epithelial-to-mesenchymal transition process. Collectively, our study has first established the complex and vital roles of EPB41L3 and implicated EPB41L3 as a potential biomarker in osteosarcoma.

Meningioma: A Review of Clinicopathological and Molecular Aspects

Meningiomas are the most the common primary brain tumors in adults, representing approximately a third of all intracranial neoplasms. They classically are found to be more common in females, with the exception of higher grades that have a predilection for males, and patients of older age. Meningiomas can also be seen as a spectrum of inherited syndromes such as neurofibromatosis 2 as well as ionizing radiation. In general, the 5-year survival for a WHO grade I meningioma exceeds 80%; however, survival is greatly reduced in anaplastic meningiomas. The standard of care for meningiomas in a surgically-accessible location is gross total resection. Radiation therapy is generally saved for atypical, anaplastic, recurrent, and surgically inaccessible benign meningiomas with a total dose of ~60 Gy. However, the method of radiation, regimen and timing is still evolving and is an area of active research with ongoing clinical trials. While there are currently no good adjuvant chemotherapeutic agents available, recent advances in the genomic and epigenomic landscape of meningiomas are being explored for potential targeted therapy.

Molecular characteristics of meningiomas

Meningioma is the most common primary intracranial tumor in adults. The grading of meningioma is based on World Health Organization criteria, which rely on histopathological features alone. This grading system is unable to conclusively predict the clinical behavior of these tumors (i.e., recurrence or prognosis in benign or atypical grades). Advances in molecular techniques over the last decade that include genomic and epigenomic data associated with meningiomas have been used to identify genetic biomarkers that can predict tumor behavior. This review summarizes the molecular characteristics of meningioma using genetic and epigenetic biomarkers. Molecular alterations that can predict meningioma behavior may be integrated into the upcoming World Health Organization grading system.

Pivotal roles of protein 4.1B/DAL‑1, a FERM‑domain containing protein, in tumor progression (Review)

Protein 4.1B/DAL‑1, encoded by erythrocyte membrane protein band 4.1‑like 3 (EPB41L3), belongs to the protein 4.1 superfamily, a group of proteins that share a conserved four.one‑ezrin‑radixin‑moesin (FERM) domain. Protein 4.1B/DAL‑1 serves a crucial role in cytoskeletal organization and a number of processes through multiple interactions with membrane proteins via its FERM, spectrin‑actin‑binding and C‑terminal domains. A number of studies have indicated that a loss of EPB41L3 expression is commonly observed in lung cancer, breast cancer, esophageal squamous cell carcinoma and meningiomas. DNA methylation and a loss of heterozygosity have been reported to contribute to the downregulation of EPB41L3. To date, the biological functions of protein 4.1B/DAL‑1 in carcinogenesis remain unknown. The present review summarizes the current understanding of the role of protein 4.1B/DAL‑1 in cancer and highlights its potential as a cancer diagnostic and prognostic biomarker in cancer therapeutics.

Serum TIMP1 and TIMP2 concentration in patients with different grades of meningioma

OBJECTIVE

Meningiomas are common primary brain tumors that constitute about 13% of all intracranial tumors. Matrix metalloproteinase-9 (MMP-9) is able to degrade the extracellular matrix and basement membrane leading to cancer cell invasion and metastasis. MMPs are specifically inhibited by a family of small extracellular proteins known as the tissue inhibitors of metalloproteinases (TIMPs). The objective of this project was to evaluate serum concentration of TIMP-1 and TIMP-2 in patients with different grades of meningioma.

PATIENTS AND METHODS

Ninety samples from different stages of patients with meningitis (42 cases of grade I, 28 grade II, 20 grade III) and 51 samples from normal healthy were included in this study. Total protein concentration (TPC) and the level TIMP-1 and TIMP-2 serum were determined by Bio-Rad protein assay based on the Bradford dye procedure and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

No significant change in the TPC was seen in the serum of patients with meningioma when compared with normal controls. Results obtained demonstrated that all serum samples presented TIMP-1 and TIMP-2 expression, whereas, starting from grade I to III meningiomas, a significant decrease of TIMP-1 and TIMP-2 expression was observed as compared to controls.

CONCLUSION

The results of this study show that a low expression of TIMP1 and TIMP2 is correlated with advanced stages of meningioma. It is also concluded that the detection of serum TIMP1 and TIMP2 may be useful in classifying different grades of meningioma.

Advances in meningioma genetics: novel therapeutic opportunities

Meningiomas currently are among the most frequent intracranial tumours. Although the majority of meningiomas can be cured by surgical resection, ∼20% of patients have an aggressive clinical course with tumour recurrence or progressive disease, resulting in substantial morbidity and increased mortality of affected patients. During the past 3 years, exciting new data have been published that provide insights into the molecular background of meningiomas and link sites of tumour development with characteristic histopathological and molecular features, opening a new road to novel and promising treatment options for aggressive meningiomas. A growing number of the newly discovered recurrent mutations have been linked to a particular clinicopathological phenotype. Moreover, the updated WHO classification of brain tumours published in 2016 has incorporated some of these molecular findings, setting the stage for the improvement of future therapeutic efforts through the integration of essential molecular findings. Finally, an additional potential classification of meningiomas based on methylation profiling has been launched, which provides clues in the assessment of individual risk of meningioma recurrence. All of these developments are creating new prospects for effective molecularly driven diagnosis and therapy of meningiomas.

Cellular prion protein (PrPC) in the development of Merlin-deficient tumours

Loss of function mutations in the neurofibromatosis Type 2 (NF2) gene, coding for a tumour suppressor, Merlin, cause multiple tumours of the nervous system such as schwannomas, meningiomas and ependymomas. These tumours may occur sporadically or as part of the hereditary condition neurofibromatosis Type 2 (NF2). Current treatment is confined to (radio) surgery and no targeted drug therapies exist. NF2 mutations and/or Merlin inactivation are also seen in other cancers including some mesothelioma, breast cancer, colorectal carcinoma, melanoma and glioblastoma. To study the relationship between Merlin deficiency and tumourigenesis, we have developed an in vitro model comprising human primary schwannoma cells, the most common Merlin-deficient tumour and the hallmark for NF2. Using this model, we show increased expression of cellular prion protein (PrP^C) in schwannoma cells and tissues. In addition, a strong overexpression of PrP^C is observed in human Merlin-deficient mesothelioma cell line TRA and in human Merlin-deficient meningiomas. PrP^C contributes to increased proliferation, cell-matrix adhesion and survival in schwannoma cells acting via 37/67 kDa non-integrin laminin receptor (LR/37/67 kDa) and downstream ERK1/2, PI3K/AKT and FAK signalling pathways. PrP^C protein is also strongly released from schwannoma cells via exosomes and as a free peptide suggesting that it may act in an autocrine and/or paracrine manner. We suggest that PrP^C and its interactor, LR/37/67 kDa, could be potential therapeutic targets for schwannomas and other Merlin-deficient tumours.

Genetic and epigenetic alterations in meningiomas

Meningiomas originate from the arachnoid layer of the meninges and divided histologically into three grades: benign (grade I), atypical (grade II), and malignant meningiomas (grade III). Genetic alterations in grade I meningiomas include frequent deletions of chromosomal locus 22q12 and NF2 gene mutations and uncommon somatic SMARCB1 and SMARCE1gene mutations; In grade II meningiomas, chromosomal losses occur on 1p, 22q, 14q, 18q, 10, and 6q, and gains on 20q, 12q, 15q, 1q, 9q, and 17q; In grade III meningiomas, losses have been recognized on 6q, 10, and 14q and alterations of PTEN, CDKN2A and CDKN2B genes. Epigenetic alterations in meningiomas include hypermethylation of the tumor suppressor genes p73 in grade I meningiomas and TIMP3 GSTP1, MEG3, HOXA6, HOXA9, PENK, WNK2 and UPK3A genes with an increasing frequency according to grade. Abnormal expression of IGF signaling family genes and Wnt signaling pathway is associated with meningioma progression. MiRNA expression profiling of meningiomas show downregulation of miR-29c-3p, miR-200a, miR-145 and miR- 219-5p and upregulation of miR-21 miR-335 and miR-190a levels. In conclusion, extensive genetic and epigenetic alterations exist in meningiomas that may help assessing prognosis. In addition, since miRNA expression may be modified by artificial miRNAs, new effective therapeutic strategies may be developed especially for resistant or high grade meningiomas.

Genetic/molecular alterations of meningiomas and the signaling pathways targeted

Meningiomas are usually considered to be benign central nervous system tumors; however, they show heterogenous clinical, histolopathological and cytogenetic features associated with a variable outcome. In recent years important advances have been achieved in the identification of the genetic/molecular alterations of meningiomas and the signaling pathways involved. Thus, monosomy 22, which is often associated with mutations of the NF2 gene, has emerged as the most frequent alteration of meningiomas; in addition, several other genes (e.g., AKT1, KLF4, TRAF7, SMO) and chromosomes have been found to be recurrently altered often in association with more complex karyotypes and involvement of multiple signaling pathways. Here we review the current knowledge about the most relevant genes involved and the signaling pathways targeted by such alterations. In addition, we summarize those proposals that have been made so far for classification and prognostic stratification of meningiomas based on their genetic/genomic features.

Biology and clinical management challenges in meningioma

Meningiomas are the most frequently occurring intracranial tumors. They are characterized by a broad spectrum of histopathologic appearance. Molecular alterations driving meningioma development, which affect the NF2 gene, are found in roughly 50% of patients. Rare genetic events in benign meningiomas are mutations in TRAF7, KLF4, AKT1, and SMO; all of these mutations are exclusive of NF2 alterations. Progression to a clinically aggressive meningioma is linked to inactivation of CDKN2A/B genes, and a plethora of signaling molecules have been described as activated in meningiomas, which supports the concept of successful clinical use of specific inhibitors. Established treatments include surgical resection with or without radiotherapy delivered in a single fraction, a few large fractions (radiosurgery), or multiple fractions (fractionated radiotherapy). For recurrent and aggressive tumors, inhibitors of the vascular endothelial growth factor (VEGF) pathway, such as vatalinib, bevacizumab, and sunitinib, showed signs of activity in small, uncontrolled studies, and prospective clinical studies will test the efficacy of the tetrahydroisoquinoline trabectedin and of SMO and AKT1 inhibitors.

EPB41L3, TSP-1 and RASSF2 as new clinically relevant prognostic biomarkers in diffuse gliomas

Hypermethylation of tumor suppressor genes is one of the hallmarks in the progression of brain tumors. Our objectives were to analyze the presence of the hypermethylation of EPB41L3, RASSF2 and TSP-1 genes in 132 diffuse gliomas (astrocytic and oligodendroglial tumors) and in 10 cases of normal brain, and to establish their association with the patients’ clinicopathological characteristics. Gene hypermethylation was analyzed by methylation-specific-PCR and confirmed by pyrosequencing (for EPB41L3 and TSP-1) and bisulfite-sequencing (for RASSF2). EPB41L3, RASSF2 and TSP-1 genes were hypermethylated only in tumors (29%, 10.6%, and 50%, respectively), confirming their cancer-specific role. Treatment of cells with the DNA-demethylating-agent 5-aza-2′-deoxycytidine restores their transcription, as confirmed by quantitative-reverse-transcription-PCR and immunofluorescence. Immunohistochemistry for EPB41L3, RASSF2 and TSP-1 was performed to analyze protein expression; p53, ki-67, and CD31 expression and 1p/19q co-deletion were considered to better characterize the tumors. EPB41L3 and TSP-1 hypermethylation was associated with worse (p = 0.047) and better (p = 0.037) prognosis, respectively. This observation was confirmed after adjusting the results for age and tumor grade, the role of TSP-1 being most pronounced in oligodendrogliomas (p = 0.001). We conclude that EPB41L3, RASSF2 and TSP-1 genes are involved in the pathogenesis of diffuse gliomas, and that EPB41L3 and TSP-1 hypermethylation are of prognostic significance.

Case-Based Review: meningioma

Meningioma is by far the most common primary intracranial tumor in adults. Treatment of meningioma is complex due to a tremendous amount of variability in tumor behavior. Many patients are incidentally found to have tumors that will remain asymptomatic throughout their lives. It is important to identify these patients so that they can be spared from potentially morbid interventions. On the other end of the spectrum, high-grade meningiomas can behave very aggressively. When treatment is necessary, surgical resection is the cornerstone of meningioma therapy. Studies spanning decades have demonstrated that extent of resection correlates with prognosis. Radiation therapy, either in the form of external beam radiation therapy or stereotactic radiosurgery, represents another important therapeutic tool that can be used in place of or as a supplement to surgery. There are no chemotherapeutic agents of proven efficacy against meningioma, and chemotherapy treatment is generally reserved for patients who have exhausted surgical and radiotherapy options. Ongoing and future studies will help to answer unresolved questions such as the optimum use of radiation in resected WHO grade II meningiomas and the efficacy of additional chemotherapy agents.

Surgically resected skull base meningiomas demonstrate a divergent postoperative recurrence pattern compared with non-skull base meningiomas

OBJECTIVE The objective of this study was to identify the natural history and clinical predictors of postoperative recurrence of skull base and non-skull base meningiomas. METHODS The authors performed a retrospective hospital-based study of all patients with meningioma referred to their institution from September 1993 to January 2014. The cohort constituted both patients with a first-time presentation and those with evidence of recurrence. Kaplan-Meier curves were constructed for analysis of recurrence and differences were assessed using the log-rank test. Cox proportional hazard regression was used to identify potential predictors of recurrence. RESULTS Overall, 398 intracranial meningiomas were reviewed, including 269 (68%) non-skull base and 129 (32%) skull base meningiomas (median follow-up 30.2 months, interquartile range [IQR] 8.5-76 months). The 10-year recurrence-free survival rates for patients with gross-total resection (GTR) and subtotal resection (STR) were 90% and 43%, respectively. Skull base tumors were associated with a lower proliferation index (0.041 vs 0.062, p = 0.001), higher likelihood of WHO Grade I (85.3% vs 69.1%, p = 0.003), and younger patient age (55.2 vs 58.3 years, p = 0.01). Meningiomas in all locations demonstrated an average recurrence rate of 30% at 100 months of follow-up. Subsequently, the recurrence of skull base meningiomas plateaued whereas non-skull base lesions had an 80% recurrence rate at 230 months follow-up (p = 0.02). On univariate analysis, a prior history of recurrence (p < 0.001), initial WHO grade following resection (p < 0.001), and the inability to obtain GTR (p < 0.001) were predictors of future recurrence. On multivariate analysis a prior history of recurrence (p = 0.02) and an STR (p < 0.01) were independent predictors of a recurrence. Assessing only patients with primary presentations, STR and WHO Grades II and III were independent predictors of recurrence (p < 0.001 for both). CONCLUSIONS Patients with skull base meningiomas present at a younger age and have less aggressive lesions overall. Extent of resection is a key predictor of recurrence and long-term follow-up of meningiomas is necessary, especially for non-skull base tumors. In skull base meningiomas, recurrence risk plateaus approximately 100 months after surgery, suggesting that for this specific cohort, follow-up after 100 months can be less frequent.

Merlin/NF2 Suppresses Pancreatic Tumor Growth and Metastasis by Attenuating the FOXM1-Mediated Wnt/β-Catenin Signaling

Merlin, the protein encoded by the NF2 gene, is a member of the band 4.1 family of cytoskeleton-associated proteins and functions as a tumor suppressor for many types of cancer. However, the roles and mechanism of Merlin expression in pancreatic cancer have remained unclear. In this study, we sought to determine the impact of Merlin expression on pancreatic cancer development and progression using human tissue specimens, cell lines, and animal models. Decreased expression of Merlin was pronounced in human pancreatic tumors and cancer cell lines. Functional analysis revealed that restored expression of Merlin inhibited pancreatic tumor growth and metastasis in vitro and in vivo. Furthermore, Merlin suppressed the expression of Wnt/β-catenin signaling downstream genes and the nuclear expression of β-catenin protein, and overexpression of Forkhead box M1 (FOXM1) attenuated the suppressive effect of Merlin on Wnt/β-catenin signaling. Mechanistically, Merlin decreased the stability of FOXM1 protein, which plays critical roles in nuclear translocation of β-catenin. Collectively, these findings demonstrated that Merlin critically regulated pancreatic cancer pathogenesis by suppressing FOXM1/β-catenin signaling, suggesting that targeting novel Merlin/FOXM1/β-catenin signaling is an effective therapeutic strategy for pancreatic cancer.

Malignant progression to anaplastic meningioma: Neuropathology, molecular pathology, and experimental models

Meningioma is a common adult intracranial tumor, and while several cases are considered benign, a subset is malignant with biologically aggressive behavior and is refractory to current treatment strategies of combined surgery and radiotherapy. Anaplastic meningiomas are quite aggressive and correspond to a World Health Organization (WHO) Grade III tumor. This highly aggressive phenotype mandates the need for more efficacious therapies. Designing rational therapies for treatment will have its foundation in the biologic understanding of involved genes and molecular pathways in these types of tumors. Anaplastic meningiomas (WHO Grade III) can arise from malignant transformation of lower grade (WHO Grade I/II) tumors, however there is an incomplete understanding of specific genetic drivers of malignant transformation in these tumors. Here, the current understanding of anaplastic meningiomas is reviewed in the context of human neuropathologic specimens and small animal models.

Tumor suppressor role of protein 4.1B/DAL-1

Protein 4.1B/DAL-1 is a membrane skeletal protein that belongs to the protein 4.1 family. Protein 4.1B/DAL-1 is localized to sites of cell-cell contact and functions as an adapter protein, linking the plasma membrane to the cytoskeleton or associated cytoplasmic signaling effectors and facilitating their activities in various pathways. Protein 4.1B/DAL-1 is involved in various cytoskeleton-associated processes, such as cell motility and adhesion. Moreover, protein 4.1B/DAL-1 also plays a regulatory role in cell growth, differentiation, and the establishment of epithelial-like cell structures. Protein 4.1B/DAL-1 is normally expressed in multiple human tissues, but loss of its expression or prominent down-regulation of its expression is frequently observed in corresponding tumor tissues and tumor cell lines, suggesting that protein 4.1B/DAL-1 is involved in the molecular pathogenesis of these tumors and acts as a potential tumor suppressor. This review will focus on the structure of protein 4.1B/DAL-1, 4.1B/DAL-1-interacting molecules, 4.1B/DAL-1 inactivation and tumor progression, and anti-tumor activity of the 4.1B/DAL-1.

Diagnostic and molecular pathology of meningiomas

This article will review the neuropathology of meningiomas. From the neurosurgeon's point of view, accurate neuropathological diagnosis will play an increasingly important role in clinical practice. Predicting an individual patient's prognosis will become ever more important with the advent of various new radiotherapeutic/radiosurgical modalities. Defining the optimal treatment for nonbenign meningiomas requires a robust and reproducible diagnosis. This review will therefore not only describe classical radiological and histopathological diagnosis, but will also focus on the emerging field of molecular neuropathology. Implementing these advances in our daily clinical routine holds the promise of improving diagnostic accuracy.

Current standing and frontiers of gene therapy for meningiomas

Meningiomas are among the most common intracranial tumors. The treatment of choice for these lesions is complete resection, but in 50% of cases it is not achieved due to tumor location and/or surgical morbidities. Moreover, benign meningiomas have high recurrence rates of up to 32% in long-term follow-up. Molecular analyses have begun to uncover the genetics behind meningiomas, giving rise to potential genetics-based treatments, including gene therapy. The authors performed a literature review on the most relevant genes associated with meningiomas and both current and potential gene therapy strategies to treat these tumors. Wild-type NF2 gene insertion, oncolytic viruses, and transfer of silencing RNA have all shown promising results both in vitro and in mice. These strategies have decreased meningioma cell growth, proliferation, and angiogenesis. However, no clinical trial has been done to date. Future research and trials in gene insertion, selective inhibition of oncogenes, and the use of oncolytic viruses, among other potential treatment approaches, may shape the future of meningioma management.

Analysis of gene expression pattern and neuroanatomical correlates for SLC20A2 (PiT-2) shows a molecular network with potential impact in idiopathic basal ganglia calcification ("Fahr's disease")

Familial idiopathic basal ganglia calcification (FIBGC), also known as "Fahr's disease," is a neuropsychiatric disorder with motor and cognitive symptoms. It is characterized pathologically by bilateral calcification most commonly in the basal ganglia and also in other brain regions such as the thalamus and cerebellum. A recent report by Wang et al. (2012) discovered multiple families with FIBGC carrying mutations in the SLC20A2 gene, encoding the inorganic phosphate transporter PiT-2, which segregated in an autosomal dominant pattern. To understand further the role of SLC20A2 in FIBGC brain pathology, here we described the gene expression pattern across the whole brain for SLC20A2, using the Allen Institute Human Brain Atlas database. Microarray analysis provided evidence that the neuroanatomical pattern of expression for SLC20A2 is highest in the regions most commonly affected in FIBGC. Neuroanatomical regions that demonstrated high correlation or anti-correlation with SLC20A2 expression also showed a molecular network with potential to explain the limited neuroanatomical distribution of calcifications in IBGC. Lastly, these co-expression networks suggest additional further candidate genes for FIBGC.

Spinal cord tumours: advances in genetics and their implications for treatment

Tumours of the spinal cord, although rare, are associated with high morbidity. Surgical resection remains the primary treatment for patients with this disease, and offers the best chance for cure. Such surgical procedures, however, carry substantial risks such as worsening of neurological deficit, paralysis and death. New therapeutic avenues for spinal cord tumours are needed, but genetic studies of the molecular mechanisms governing tumourigenesis in the spinal cord are limited by the scarcity of high-quality human tumour samples. Many spinal cord tumours have intracranial counterparts that have been extensively studied, but emerging data show that the tumours are genetically and biologically distinct. The differences between brain and spine tumours make extrapolation of data from one to the other difficult. In this Review, we describe the demographics, genetics and current treatment approaches for the most commonly encountered spinal cord tumours--namely, ependymomas, astrocytomas, haemangioblastomas and meningiomas. We highlight advances in understanding of the biological basis of these lesions, and explain how the latest progress in genetics and beyond are being translated to improve patient care.

Genomic sequencing of meningiomas identifies oncogenic SMO and AKT1 mutations

Meningiomas are the most common primary nervous system tumor. The tumor suppressor NF2 is disrupted in approximately half of meningiomas¹ but the complete spectrum of genetic changes remains undefined. We performed whole-genome or whole-exome sequencing on 17 meningiomas and focused sequencing on an additional 48 tumors to identify and validate somatic genetic alterations. Most meningiomas exhibited simple genomes, with fewer mutations, rearrangements, and copy-number alterations than reported in other adult tumors. However, several meningiomas harbored more complex patterns of copy-number changes and rearrangements including one tumor with chromothripsis. We confirmed focal NF2 inactivation in 43% of tumors and found alterations in epigenetic modifiers among an additional 8% of tumors. A subset of meningiomas lacking NF2 alterations harbored recurrent oncogenic mutations in AKT1 (E17K) and SMO (W535L) and exhibited immunohistochemical evidence of activation of their pathways. These mutations were present in therapeutically challenging tumors of the skull base and higher grade. These results begin to define the spectrum of genetic alterations in meningiomas and identify potential therapeutic targets.

Epigenetic subclassification of meningiomas based on genome-wide DNA methylation analyses

Meningiomas are among the most common intracranial tumors and are mostly curable by surgical resection. However, some populations of meningiomas with benign histological profiles show malignant behavior. The reasons for this inconsistency are yet to be ascertained, and novel diagnostic criteria other than the histological one are urgently needed. The aim of the present study is to subclassify meningiomas from the viewpoint of gene methylation and to determine the subgroup with malignant characteristics. Thirty meningiomas were analyzed using microarrays for 6157 genes and were classified into three clusters on the basis of their methylation status; these were found to be independent of the histological grading. One of the clusters showed a high frequency of recurrence, with a marked accumulation of methylation in a subset of genes. We hypothesized that the aggressive meningiomas universally share characteristic methylation in certain genes; therefore, we chose the genes that strongly contributed to cluster formation. The quantified methylation values of five chosen genes (HOXA6, HOXA9, PENK, UPK3A and IGF2BP1) agreed well with microarray findings, and a scoring system consisting of the five genes significantly correlated with a high frequency of recurrence in an additional validation set of 32 patients. Of particular note is that three cases with malignant transformation already showed hypermethylation at histologically benign stage. In conclusion, a subgroup of meningiomas is characterized by aberrant hypermethylation of the subset of genes in the early stage of tumorigenesis, and our findings highlight the possibility of speculating potential malignancy of meningiomas by assessing methylation status.

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.

Molecular genetics of meningiomas: a systematic review of the current literature and potential basis for future treatment paradigms

Although a majority of meningiomas are benign neoplasms, those occurring at the cranial base may be challenging tumors to treat because of extensive tissue invasion, an inability to achieve gross-total microscopic resection, and local tumor recurrence and/or progression. A more comprehensive understanding of the genetic abnormalities associated with meningioma tumorigenesis, growth, and invasion may provide novel targets for grading assessments and individualizing molecular therapies for skull base meningiomas. The authors performed a review of the current literature to identify genes that have been associated with the formation and/or progression of meningiomas. Mutations in the NF2 gene have been most commonly implicated in the formation of the majority of meningiomas. Inactivation of other tumor suppressor genes, including DAL-1 and various tissue inhibitors of matrix metalloproteinases, upregulation of several oncogenes including c-sis and STAT3, and signaling dysregulation of pathways such as the Wnt pathway, have each been found to play important, and perhaps, complementary roles in meningioma development, progression, and recurrence. Identification of these genetic factors using genome-wide association studies and high-throughput genomics may provide data for future individualized treatment strategies.

The molecular genetics and tumor pathogenesis of meningiomas and the future directions of meningioma treatments

Meningiomas are mostly benign, slow-growing tumors of the CNS that originate from arachnoidal cap cells. While monosomy 22 is the most frequent genetic abnormality found in meningiomas, a multitude of other aberrant chromosomal alterations, signaling pathways, and growth factors have been implicated in its pathogenesis. Losses on 22q12.2, a region encoding the tumor suppressor gene merlin, represent the most common genetic alterations in early meningioma formation. Malignant meningioma progression, however, is associated with more complex karyotypes and greater genetic instability. Cytogenetic studies of atypical and anaplastic meningiomas revealed gains and losses on chromosomes 9, 10, 14, and 18, with amplifications on chromosome 17. However, the specific gene targets in a majority of these chromosomal abnormalities remain elusive.

Studies have also implicated a myriad of aberrant signaling pathways involved with meningioma tumorigenesis, including those involved with proliferation, angiogenesis, and autocrine loops. Understanding these disrupted pathways will aid in deciphering the relationship between various genetic changes and their downstream effects on meningioma pathogenesis.

Despite advancements in our understanding of meningioma pathogenesis, the conventional treatments, including surgery, radiotherapy, and stereotactic radiosurgery, have remained largely stagnant. Surgery and radiation therapy are curative in the majority of lesions, yet treatment remains challenging for meningiomas that are recurrent, aggressive, or refractory to conventional treatments. Future therapies will include combinations of targeted molecular agents as a result of continued progress in the understanding of genetic and biological changes associated with meningiomas.

In search of a better crystal ball: recent advances in prognostic markers for clear-cell renal cell carcinoma

Advances in imaging have led to a steady increase in the incidence of kidney cancer over the last two decades. There has been no corresponding improvement in our ability to predict the behavior of renal cell carcinoma. Patients with low-risk renal cell carcinoma have good long-term survival with only localized therapy but patients with aggressive disease do poorly, even with optimal multimodal treatment. Biomarkers to differentiate between these two very divergent populations have traditionally been of only limited utility. We review the recent advances in the development of molecular and immunologic markers aimed at improving prognostication of renal cell carcinoma.

Pathological classification and molecular genetics of meningiomas

Meningiomas are extremely common adult brain tumors originating from meningeal coverings of the brain and spinal cord. While most are slowly growing Word Health organization (WHO) grade I tumors, rare variants (clear cell, chordoid, papillary, and rhabdoid), as well as brain invasive (WHO grade II), atypical (WHO grade II), and anaplastic (WHO grade III) meningiomas are considerably more aggressive. This review summarizes the histopathological and genetic features of meningiomas, including differential diagnosis, pitfalls, and grading challenges. Early stages of meningioma tumorigenesis are closely linked to inactivation of one or more members of the 4.1 superfamily, including the neurofibromatosis type 2 (NF2) and 4.1B (DAL-1) genes, which interact with the 14-3-3 protein family. Other chromosome 22q genes implicated include BAM22, BCR (breakpoint cluster region), and TIMP-1, the last of which is implicated in higher-grade meningiomas. Atypical meningiomas also commonly show chromosomal losses of 1p, 6q, 10, 14q, and 18q, as well as multiple chromosomal gains. While most relevant genes remain unknown, two chromosome 14q candidates (MEG3 and NDRG2) have recently been identified. In addition to alterations of CDKN2A, p14(ARF), and CDKN2B tumor suppressor genes on 9p21, a contribution of the wingless (wnt) pathway with alterations of the E-cadherin and beta-catenin proteins, as well as alterations of the hedgehog signaling pathway have been implicated in anaplastic meningiomas. The integration of histopathological appearance, complex genetic/genomic data, and outcome will likely result in the identification of clinically distinct meningioma subgroups, which in turn can facilitate the development of targeted therapeutic strategies.

Downregulated microRNA-200a in meningiomas promotes tumor growth by reducing E-cadherin and activating the Wnt/beta-catenin signaling pathway

Meningiomas, one of the most common human brain tumors, are derived from arachnoidal cells associated with brain meninges, are usually benign, and are frequently associated with neurofibromatosis type 2. Here, we define a typical human meningioma microRNA (miRNA) profile and characterize the effects of one downregulated miRNA, miR-200a, on tumor growth. Elevated levels of miR-200a inhibited meningioma cell growth in culture and in a tumor model in vivo. Upregulation of miR-200a decreased the expression of transcription factors ZEB1 and SIP1, with consequent increased expression of E-cadherin, an adhesion protein associated with cell differentiation. Downregulation of miR-200a in meningiomas and arachnoidal cells resulted in increased expression of beta-catenin and cyclin D1 involved in cell proliferation. miR-200a was found to directly target beta-catenin mRNA, thereby inhibiting its translation and blocking Wnt/beta-catenin signaling, which is frequently involved in cancer. A direct correlation was found between the downregulation of miR-200a and the upregulation of beta-catenin in human meningioma samples. Thus, miR-200a appears to act as a multifunctional tumor suppressor miRNA in meningiomas through effects on the E-cadherin and Wnt/beta-catenin signaling pathways. This reveals a previously unrecognized signaling cascade involved in meningioma tumor development and highlights a novel molecular interaction between miR-200a and Wnt signaling, thereby providing insights into novel therapies for meningiomas.

Genomic profiling distinguishes familial multiple and sporadic multiple meningiomas

Background

Meningiomas may occur either as familial tumors in two distinct disorders, familial multiple meningioma and neurofibromatosis 2 (NF2), or sporadically, as either single or multiple tumors in individuals with no family history. Meningiomas in NF2 and approximately 60% of sporadic meningiomas involve inactivation of the NF2 locus, encoding the tumor suppressor merlin on chromosome 22q. This study was undertaken to establish whether genomic profiling could distinguish familial multiple meningiomas from sporadic solitary and sporadic multiple meningiomas.

Methods

We compared 73 meningiomas presenting as sporadic solitary (64), sporadic multiple (5) and familial multiple (4) tumors using genomic profiling by array comparative genomic hybridization (array CGH).

Results

Sporadic solitary meningiomas revealed genomic rearrangements consistent with at least two mechanisms of tumor initiation, as unsupervised cluster analysis readily distinguished tumors with chromosome 22 deletion (associated with loss of the NF2 tumor suppressor) from those without chromosome 22 deletion. Whereas sporadic meningiomas without chromosome 22 loss exhibited fewer chromosomal imbalance events overall, tumors with chromosome 22 deletion further clustered into two major groups that largely, though not perfectly, matched with their benign (WHO Grade I) or advanced (WHO Grades II and III) histological grade, with the latter exhibiting a significantly greater degree of genomic imbalance (P < 0.001). Sporadic multiple meningiomas showed a frequency of genomic imbalance events comparable to the atypical grade solitary tumors. By contrast, familial multiple meningiomas displayed no imbalances, supporting a distinct mechanism for the origin for these tumors.

Conclusion

Genomic profiling can provide an unbiased adjunct to traditional meningioma classification and provides a basis for exploring the different genetic underpinnings of tumor initiation and progression. Most importantly, the striking difference observed between sporadic and familial multiple meningiomas indicates that genomic profiling can provide valuable information for differential diagnosis of subjects with multiple meningiomas and for considering the risk for tumor occurrence in their family members.

Expression of the Tumor Suppressor Genes NF2, 4.1B, and TSLC1 in Canine Meningiomas

Meningiomas are common primary brain tumors in dogs; however, little is known about the molecular genetic mechanisms involved in their tumorigenesis. Several tumor suppressor genes have been implicated in meningioma pathogenesis in humans, including the neurofibromatosis 2 ( NF2), protein 4.1B ( 4.1 B), and tumor suppressor in lung cancer-1 ( TSLC1) genes. We investigated the expression of these tumor suppressor genes in a series of spontaneous canine meningiomas using quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) ( NF2; n = 25) and western blotting (NF2/merlin, 4.1B, TSLC1; n = 30). Decreased expression of 4.1B and TSLC1 expression on western blotting was seen in 6/30 (20%) and in 15/30 (50%) tumors, respectively, with 18/30 (60%) of meningiomas having decreased or absent expression of one or both proteins. NF2 gene expression assessed by western blotting and RT-PCR varied considerably between individual tumors. Complete loss of NF2 protein on western blotting was not seen, unlike 4.1B and TSLC1. Incidence of TSLC1 abnormalities was similar to that seen in human meningiomas, while perturbation of NF2 and 4.1B appeared to be less common than reported for human tumors. No association was observed between tumor grade, subtype, or location and tumor suppressor gene expression based on western blot or RT-PCR. These results suggest that loss of these tumor suppressor genes is a frequent occurrence in canine meningiomas and may be an early event in tumorigenesis in some cases. In addition, it is likely that other, as yet unidentified, genes play an important role in canine meningioma formation and growth.

A role for the p53 pathway in the pathology of meningiomas with NF2 loss

The neurofibromatosis 2 locus (NF2) is inactivated through mutation and loss of heterozygosity (LOH) in 40-65% of all sporadic meningiomas, while the role of the p53 tumor suppression pathway in meningioma initiation and progression is still unclear. This study aims to determine if a p53 codon 72 arginine-to-proline polymorphism, found to be correlated with cancer development and cancer patient survival in other tumors, is associated with sporadic meningioma initiation or progression. We investigated Pro72 incidence in a cohort of 92 sporadic meningiomas and analyzed its association with histological grade (WHO classification) and with NF2 LOH (determined using polymorphic microsatellite markers on 22q). The Pro72 allele was not found to be selected for in the cohort. However, in the subgroup of meningiomas with NF2 LOH and carrying Pro72, 50.0% had high grade tumors (WHO grades II and III) compared to only 14.3% of those without NF2 LOH (OR = 6.0, CI = 1.56-23.11, P = 0.012). The significant association occurred only when considering subgroups of meningiomas with or without NF2 LOH, suggesting that not including NF2 status when analyzing study cohorts may explain the variability seen in the literature where all meningiomas were grouped together. Our data suggests a role for the p53 pathway in the progression of meningiomas in which NF2 is inactivated, and highlights the importance of accounting for NF2 LOH in future studies of meningiomas and the p53 pathway.

Potential role of EPB41L3 (protein 4.1B/Dal-1) as a target for treatment of advanced prostate cancer

BACKGROUND

Loss of erythrocyte membrane protein band 4.1-like 3 (EPB41L3; aliases: protein 4.1B, differentially expressed in adenocarcinoma of the lung-1 (Dal-1)) expression has been implicated in tumor progression.

OBJECTIVE

To evaluate literature describing the role of EPB41L3 in tumorigenesis and metastasis, and to consider whether targeting this gene would be useful in the treatment of prostate cancer.

METHODS

A literature review of studies describing EPB41L3 and its aliases was conducted. Online databases (NCBI, SwissProt) were also interrogated to collect further data.

RESULTS/CONCLUSION

A growing body of evidence supports a role for loss of EPB41L3 in tumor progression, including in prostate cancer. Therapeutic strategies that could be harnessed to upregulate EPB41L3 gene expression in prostate cancer cells are currently being developed.

Array-based comparative genomic hybridization of mapped BAC DNA clones to screen for chromosome 14 copy number abnormalities in meningiomas

Chromosome 14 loss in meningiomas are associated with more aggressive tumour behaviour. To date, no studies have been reported in which the entire chromosome 14q of meningioma tumour cells has been studied by high-resolution array comparative genomic hybridization (a-CGH). Here, we used a high-resolution a-CGH to define the exact localization and extent of numerical changes of chromosome 14 in meningioma patients. An array containing 807 bacterial artificial chromosome clones specific for chromosome 14q (average resolution of approximately 130 Kb) was constructed and applied to the study of 25 meningiomas in parallel to the confirmatory interphase fluorescence in situ hybridization (iFISH) analyses. Overall, abnormalities of chromosome 14q were detected in 10/25 cases (40%). Interestingly, in seven of these cases, loss of chromosome 14q32.3 was detected by iFISH and confirmed to correspond to monosomy 14 by a-CGH. In contrast, discrepant results were found between iFISH and a-CGH in the other three altered cases. In one patient, a diploid background was observed by iFISH, while monosomy 14 was identified by a-CGH. In the remaining two cases, which showed gains of the IGH gene by iFISH, a-CGH did not detected copy number changes in one case showing a tetraploid karyotype, while in the other tumour, varying genetic imbalances along the long arm of chromosome 14 were detected. In summary, here, we report for the first time, the high-resolution a-CGH profiles of chromosome 14q in meningiomas, confirming that monosomy 14 is the most frequent alteration associated with this chromosome; other numerical abnormalities being only sporadically detected.

Gene expression profiles of meningiomas are associated with tumor cytogenetics and patient outcome

Cytogenetic analysis is a powerful tool for predicting recurrence in meningiomas, even among histologically benign/grade I tumors. Despite this, no study has been reported in which the impact of tumor cytogenetics on the gene expression profiles (GEP) has been analyzed in meningiomas. Here, we analyzed the GEP of 47 tumors and correlated them with the most clinical relevant cytogenetic subgroups of meningiomas, as confirmed through the analysis of 172 patients. Additionally three normal meningeal samples were also studied. Overall, our results show a clear association between the clinically relevant cytogenetic subgroups of meningiomas including diploid tumors (n = 18), isolated -22/22q- (n = 12), del(1p36) alone (n = 4) and complex karyotypes associated with del(1p36) and/or -14q (n = 13) and their GEP. Accordingly, based on the expression of 85 genes (40 of which were coded in the altered chromosomes used for patient stratification) the cytogenetic class of the tumor could be predicted with an error of <1%, a clear association being found between the GEP and patient outcome (P = 0.03) but not tumor histopathology. In summary, we show a clear association between GEP of neoplastic cells and clinically relevant cytogenetic subgroups of meningiomas.

Gene expression profiles in human lymphocytes irradiated in vitro with low doses of gamma rays

The molecular mechanisms underlying responses to low radiation doses are still unknown, especially in normal lymphocytes, despite the evidence suggesting specific changes that may characterize cellular responses. Our purpose was to analyze gene expression profiles by DNA microarrays in human lymphocytes after in vitro irradiation (10, 25 and 50 cGy) with gamma rays. A cytogenetic analysis was also carried out for different radiation doses. G 0 lymphocytes were irradiated and induced to proliferate for 48 h; then RNA samples were collected for gene expression analysis. ANOVA was applied to data obtained in four experiments with four healthy donors, followed by SAM analysis and hierarchical clustering. For 10, 25 and 50 cGy, the numbers of significantly (FDR <or= 0.05) modulated genes were 86, 130 and 142, respectively, and 25, 35 and 33 genes were exclusively modulated for each dose, respectively. We found CYP4X1, MAPK10 and ATF6 (10 cGy), DUSP16 and RAD51L1 (25 cGy), and RAD50, REV3L and DCLRE1A (50 cGy). A set of 34 significant genes was common for all doses; while SERPINB2 and C14orf104 were up-regulated, CREB3L2, DDX49, STK25 and XAB2 were down-regulated. Chromosome damage was significantly induced for doses >or=10 cGy (total aberrations) and >or=50 cGy (dicentrics/ rings). Therefore, low to moderate radiation doses induced qualitative and/or quantitative differences and similarities in transcript profiles, reflecting the type and extent of DNA lesions. The main biological processes associated with modulated genes were metabolism, stress response/DNA repair, cell growth/differentiation, and transcription regulation. The results indicate a potential risk to humans regarding the development of genetic instability and acquired diseases.

Molecular genetics of meningiomas: from basic research to potential clinical applications

To review our current understanding of the molecular pathogenesis of meningiomas, to suggest topics for future investigations, and to present perspectives for clinical application. Significant progress has been made in recent years in delineating the molecular mechanisms involved in meningioma formation, growth, and malignant progression. However, many questions remain unanswered. Mutations in the NF2 gene probably account for the formation of more than half of all meningiomas. On the other hand, the molecular events underlying the initiation of meningiomas without NF2 mutations have yet to be identified. Investigating hereditary conditions associated with an increased meningioma incidence and the mechanisms underlying the development of radiation-induced meningiomas could potentially yield relevant insights. Meningioma growth is sustained by the dysregulated expression of steroid hormones, growth factors, their receptors, and activation of signal transduction cascades. The underlying genetic causes are unknown. Malignant progression of meningiomas probably involves the inactivation of tumor suppressor genes on chromosomes 1p, 9p, 10q, and 14q. However, with the possible exception of INK4A/INK4B, the actual targets of these chromosomal losses have remained largely elusive. Cell cycle dysregulation and telomerase activation have been recognized as important steps in meningioma progression. Telomere dynamics, cell cycle control, and the mechanisms responsible for deoxyribonucleic acid damage control are tightly interwoven. Investigating genes involved in the maintenance of genomic integrity might significantly deepen the understanding of meningioma progression. An area that has received relatively little attention thus far is the genetic background of meningioma spread and invasion. Possible clinical applications of the molecular data available may include a meningioma grading system based on genetic alterations, as well as therapeutic strategies for refractory meningiomas aimed at interfering with signal transduction pathways.

Mutational spectrum of the NF2 gene: a meta-analysis of 12 years of research and diagnostic laboratory findings

The NF2 tumor suppressor gene on chromosome 22 is a member of the protein 4.1 family of cytoskeletal elements. A number of single- and multiple-tumor phenotypes have been linked to alterations of NF2 since its characterization in 1993. We present a meta-analysis of 967 constitutional and somatic NF2 alterations from 93 published reports, along with 59 additional unpublished events identified in our laboratory and 115 alterations identified in clinical samples submitted to the Massachusetts General Hospital (MGH) Neurogenetics DNA Diagnostic Laboratory. In total, these sources defined 1,070 small genetic changes detected primarily by exon scanning, 42 intragenic changes of one whole exon or larger, and 29 whole gene deletions and gross chromosomal rearrangements. Constitutional single-exon events (N=422) were significantly more likely to be nonsense or splice site changes than somatic events (N=533), which favored frameshift changes (chi(2) test; P<0.001). Somatic events also differed markedly between tumors of different pathology, most significantly in the tendency of somatic events in meningiomas to lie within the 5' FERM domain of the transcript (Fisher's exact test; P<0.01 in comparison to schwannomas) with a complete absence of mutations in exons 14 and 15. There was no statistically significant difference in mutation type or exon distribution between published constitutional events and those found by the clinical laboratory. Less than 10% of all published and unpublished small alterations are nontruncating (N=63) and these changes are clustered in exons 2 and 3, suggesting that this region may be especially crucial to tumor suppressor activity in the protein.

Histological classification and molecular genetics of meningiomas

Meningiomas account for up to 30% of all primary intracranial tumours. They are histologically classified according to the World Health Organization (WHO) classification of tumours of the nervous system. Most meningiomas are benign lesions of WHO grade I, whereas some meningioma variants correspond with WHO grades II and III and are associated with a higher risk of recurrence and shorter survival times. Mutations in the NF2 gene and loss of chromosome 22q are the most common genetic alterations associated with the initiation of meningiomas. With increase in tumour grade, additional progression-associated molecular aberrations can be found; however, most of the relevant genes are yet to be identified. High-throughput techniques of global genome and transcriptome analyses and new meningioma models provide increasing insight into meningioma biology and will help to identify common pathogenic pathways that may be targeted by new therapeutic approaches.

Age associated increase in the prevalence of chromosome 22q loss of heterozygosity in histological subsets of benign meningioma

Chromosome 22q loss of heterozygosity (LOH) is the most common allelic loss in benign meningioma and is thought to be the earliest initiating event in meningioma formation. We used published data and logistic regression to evaluate the association of 22q LOH with age at diagnosis in 318 transitional, fibroblastic, and meningothelial meningiomas. After adjustment for anatomical location, the odds ratio of 22q LOH per year of age was >1 in each histological type of meningioma, and was significantly >1 in transitional and fibroblastic meningioma. This finding is compatible with involvement of the neurofibromatosis 2 tumour suppressor gene, NF2, on chromosome 22q in the high incidence of benign meningioma in the elderly.