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

A large-scale targeted proteomics of serum and tissue shows the utility of classifying high grade and low grade meningioma tumors

BACKGROUND

Meningiomas are the most prevalent primary brain tumors. Due to their increasing burden on healthcare, meningiomas have become a pivot of translational research globally. Despite many studies in the field of discovery proteomics, the identification of grade-specific markers for meningioma is still a paradox and requires thorough investigation. The potential of the reported markers in different studies needs further verification in large and independent sample cohorts to identify the best set of markers with a better clinical perspective.

METHODS

A total of 53 fresh frozen tumor tissue and 51 serum samples were acquired from meningioma patients respectively along with healthy controls, to validate the prospect of reported differentially expressed proteins and claimed markers of Meningioma mined from numerous manuscripts and knowledgebases. A small subset of Glioma/Glioblastoma samples were also included to investigate inter-tumor segregation. Furthermore, a simple Machine Learning (ML) based analysis was performed to evaluate the classification accuracy of the list of proteins.

RESULTS

A list of 15 proteins from tissue and 12 proteins from serum were found to be the best segregator using a feature selection-based machine learning strategy with an accuracy of around 80% in predicting low grade (WHO grade I) and high grade (WHO grade II and WHO grade III) meningiomas. In addition, the discriminant analysis could also unveil the complexity of meningioma grading from a segregation pattern, which leads to the understanding of transition phases between the grades.

CONCLUSIONS

The identified list of validated markers could play an instrumental role in the classification of meningioma as well as provide novel clinical perspectives in regard to prognosis and therapeutic targets.

Recent advances in the molecular prognostication of meningiomas

Meningiomas are the most common primary intracranial neoplasm. While traditionally viewed as benign, meningiomas are associated with significant patient morbidity, and certain meningioma subgroups display more aggressive and malignant behavior with higher rates of recurrence. Historically, the risk stratification of meningioma recurrence has been primarily associated with the World Health Organization histopathological grade and surgical extent of resection. However, a growing body of literature has highlighted the value of utilizing molecular characteristics to assess meningioma aggressiveness and recurrence risk. In this review, we discuss preclinical and clinical evidence surrounding the use of molecular classification schemes for meningioma prognostication. We also highlight how molecular data may inform meningioma treatment strategies and future directions.

Molecular genetics of meningiomas

Comprehensive genomic studies of meningioma have offered important insights about the molecular mechanisms underlying this common brain tumor. The use of next-generation sequencing techniques has identified driver mutations in approximately 80% of benign sporadic lesions, as well as epigenetic, regulatory, and copy number events that are associated with formation and disease progression. The events described to date fall into five mutually exclusive molecular subgroups that correlate with tumor location and embryological origin. Importantly, these subgroups also carry implications for clinical management, as they are predictive of histologic subtype and the likelihood of progression. Further work is necessary to understand the molecular mechanisms by which identified mutations drive tumorigenesis as well as the genomic pathways that transform benign lesions into malignancies. Progress made during the past decade has opened the door to potential molecular therapies as well as integration of meningioma genotyping data into clinical management decisions. Several pharmacologic trials are currently underway that leverage recent genomic findings to target established oncogenic pathways in refractory tumors. With the combined efforts of physicians and basic science investigators, the clinical management of meningioma will continue to make important strides in the coming years.

Intracranial meningioma with leptomeningeal dissemination : retrospective study with review of the literature

OBJECTIVE

The purposes of this article are to present 5 cases of intracranial meningioma with leptomeningeal dissemination (LD) and investigate the characteristics of this disease.

METHODS

We present a retrospective case series of 5 females at our institutions (age ranged 21-72 years, mean 54.6 years) diagnosed with LD of an intracranial meningioma after surgery between 1998 and 2013. A database search revealed 45 cases with LD of meningioma in the English literature. Characteristic features were analyzed and compared.

RESULTS

The incidence rate at our institutions of LD of meningioma was 0.9% (5/534). World Health Organization (WHO) grade was distributed as follows: I : 2, II : 2, and III : 1. Time to LD ranged from 2.5 months to 6.9 years; the patient with WHO grade III had the shortest interval to LD. The patient with an intraventricular meningioma (WHO grade II) had the second shortest interval to LD (1.7 years), and simultaneously revealed both LD and extraneuronal metastases. Four of 5 patients showed a disease progression, with the survival ranging from 1 month to 3.8 years after LD. Based on the literature, the initial tumor was an intraventricular meningioma in 9 patients, and their time to LD was shorter on average (mean 1.9 years). Histologically, 26 of 45 (58%) were initially diagnosed with a WHO grade II or III meningioma, and 6 of 19 patients (32%) with WHO grade I revealed malignant transformation.

CONCLUSION

This study shows that intraventricular location and histologically aggressive features seem to increase the chance of LD of meningioma.

Loss of the protein-tyrosine phosphatase DEP-1/PTPRJ drives meningioma cell motility

DEP-1/PTPRJ is a transmembrane protein-tyrosine phosphatase which has been proposed as a suppressor of epithelial tumors. We have found loss of heterozygosity (LOH) of the PTPRJ gene and loss of DEP-1 protein expression in a subset of human meningiomas. RNAi-mediated suppression of DEP-1 in DEP-1 positive meningioma cell lines caused enhanced motility and colony formation in semi-solid media. Cells devoid of DEP-1 exhibited enhanced signaling of endogenous platelet-derived growth factor (PDGF) receptors, and reduced paxillin phosphorylation upon seeding. Moreover, DEP-1 loss caused diminished adhesion to different matrices, and impaired cell spreading. DEP-1-deficient meningioma cells exhibited invasive growth in an orthotopic xenotransplantation model in nude mice, indicating that elevated motility translates into a biological phenotype in vivo. We propose that negative regulation of PDGF receptor signaling and positive regulation of adhesion signaling by DEP-1 cooperate in inhibition of meningioma cell motility, and possibly tumor invasiveness. These phenotypes of DEP-1 loss reveal functions of DEP-1 in adherent cells, and may be more generally relevant for tumorigenesis.

Early malignant transformation of a petroclival meningothelial meningioma

Although some authors have reported the malignant transformation of meningiomas, there has been no previous report describing that a meningothelial meningioma transformed into an atypical meningioma within 1 year. This report documents a 57-year-old woman who presented with right hearing disturbance. Magnetic resonance imaging revealed a right petroclival meningioma. The tumor was subtotally removed and was diagnosed to be a meningothelial meningioma. Seven months after surgery, a recurrence of the tumor was confirmed. The diagnosis of this recurrent tumor was an atypical meningioma. The MIB-1 index and the percent of p53 protein-positive cells in the primary tumor were 4.6% and 35.4%, respectively, whereas those of the recurrent tumor were 34.7% and 33.1%, respectively. A chromosomal DNA copy number loss was observed on 1p, 6q, 10, 14q, and -22q detected in both the primary and the recurrent tumors. These results suggest that the present case had a potentially malignant tumor in the early stage, although it had the histological features of benign meningiomas. An evaluation of the MIB-1 index, as well as the expression of p53 and chromosomal aberrations, may be useful for predicting the malignant transformation of meningiomas.

Malignant transformation-related genes in meningiomas: allelic loss on 1p36 and methylation status of p73 and RASSF1A

OBJECT

Analysis of meningiomas supports the suggestion that loss of heterozygosity (LOH) of chromosome arm 1p plays an important role in malignancy. The aim of this study was to identify genes related to meningioma progression from the benign state to the atypical and anaplastic states by examining 1p LOH and the promoter methylation of RASSF1A and p73.

METHODS

The authors studied 40 surgical specimens (22 WHO Grade I, 11 Grade II, and seven Grade III) obtained in 37 patients with meningioma. The LOH at 1p36 was analyzed using microsatellite markers, and promoter methylation of p73 and RASSFIA was analyzed using methylation-specific polymerase chain reaction.

RESULTS

No 1p LOH was detected in the Grade I tumors, whereas it was detected in more than 80% of the Grade II and III tumors. Methylation of the p73 promoter was observed in 81.8 and 71.4% of the Grade II and III tumors, respectively, but it was not observed in any of the Grade I tumors; methylation of the RASSF1A promoter was observed in 18.2, 63.6, and 42.9% of the Grade I, II, and III tumors, respectively. Interestingly, 1p LOH and p73 promoter hypermethylation were detected in the malignantly transformed tumors but not in the lower-grade primary ones.

CONCLUSIONS

Based on the hypothesis that meningiomas cumulatively acquire genetic alterations and thus progress from the benign to the atypical and anaplastic states, genetic alterations in the methylation status of p73 or RASSF1A along with 1p LOH may result in the malignant transformation of a meningioma. This type of genetic fingerprint may play both diagnostic and therapeutic roles.

Loss of heterozygosity of the p53 gene and deregulated expression of its mRNA and protein in human brain tumors

Tumor-specific alterations at the p53 gene locus were analyzed in 40 human brain tumor samples. Gliomas were more prevalent in young males and meningiomas in old females. Structural changes at the intron 1 region of the p53 gene were analyzed in these tumors by Southern blotting. Among the 40 tumors, 33 were informative and 21 of these (63.6%) informative cases showed loss of heterozygosity (LOH). This is the first report showing LOH at the intron 1 region of p53 gene in human brain tumors. The level of p53 mRNA, p53 protein and Ser 392 phosphorylated p53 protein were also analyzed in all tumor samples. Normal sized p53 mRNA and protein were present in all the tumor samples; however, their levels were 1.5- to 4-fold higher compared to the control suggesting deregulated p53 pathway in these tumors. No correlation was found between LOH status and the levels of p53 mRNA and protein. In all high-grade glioblastomas majority of the p53 protein existed as Ser 392 phosphorylated form as compared to low-grade gliomas. In addition, the percentage of Ser 392 phosphorylated form of p53 protein was lower in meningiomas and other brain tumor types irrespective of tumor grade. These results suggest involvement of Ser 392 phosphorylated form of p53 protein during the later stages of glioma development. These results also indicate that deregulation of p53 gene could occur at various steps in p53 pathway and suggest an overall deregulation of p53 gene in most brain tumor types.