Comparative analysis of the NF2, TP53, PTEN, KRAS, NRAS and HRAS genes in sporadic and radiation-induced human meningiomas

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a meta-analysis of 967 constitutional and somatic NF2 alterations from 93 published reports, along with 59 additional unpublished events identified in our laboratory and 115 alterations identified in clinical samples submitted to the Massachusetts General Hospital (MGH) Neurogenetics DNA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 Less than 10% of all published and unpublished small alterations are nontruncating (N=63) and these changes are clustered in exons 2 and 3, suggesting that this region may be especially crucial to tumor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.

The p53/p21 DNA damage-signaling pathway is defective in most meningioma cells

Although meningiomas represent the most common class of tumors of the central nervous system, the molecular events underlying their genesis and development are still not well defined. In the present study we have used the immuno-blotting technique to study the expression level of the tumor suppressor proteins p53, p21 and PTEN in primary meningioma cells. We have also studied the induction of p21 and p53 in response to both UV light and gamma-rays. We present evidence that the p53/p21-dependent gamma-ray signaling pathway is defective in 5 out of 8 (62%) of these cells. Furthermore, we have shown that the tumor suppressor p21, p53 and PTEN proteins are differently expressed in these cells, with up to 40-folds difference between the lowest and the highest levels of each protein. These results suggest that the tumor suppressors p53/p21 signaling pathway and PTEN play important roles in the development of benign meningiomas.

CyberKnife Radiosurgery for Extremity Schwannomas: Technical Note and Case Report

Peripheral nerve sheath tumors are uncommon. Although surgical resection remains the treatment of choice for most symptomatic lesions, the potential for intraoperative injury to the nerve is not insignificant. This concern is of particular relevance in those patients with a genetic proclivity to develop multiple peripheral nerve sheath tumors. Here we report four symptomatic peripheral extremity schwannomas all in 1 patient who was treated with CyberKnife radiosurgery. The radiosurgical Dmax in each case was between 24.4 and 25.32 Gy. At 1-year follow-up, patient symptoms had been ameliorated, no tumor had increased in size and there was no compromise in neurological function. Although this experience is still very preliminary, it represents the first published description of a peripheral nerve sheath tumor being treated with stereotactic radiosurgery.

Meningeal tumors of childhood and infancy. An update and literature review

Meningeal derived tumors of the first 2 decades of life are often diagnostically challenging due to the wide morphologic spectrum encountered and the rarity of most individual entities. The 2 most common patterns include the dural/leptomeningeal-based mass and neoplastic meningitis. Both primary and secondary meningeal presentations may occur, either early or late in the course of various meningothelial, mesenchymal, embryonal, glial, hematopoietic, histiocytic, melanocytic, and inflammatory tumors. As in other areas of pediatric pathology, there are significant differences between this patient cohort and adults, differences which will be emphasized in this review.

Cancer therapy-associated CNS neuropathology: an update and review of the literature

Standard therapeutic options for brain tumors include surgery, radiation, and chemotherapy. Unfortunately, these same therapies pose risks of neurotoxicity, the most common long-term complications being radiation necrosis, chemotherapy-associated leukoencephalopathy, and secondary neoplasms. These side effects remain difficult to predict, but are associated with risk factors that include patient age, therapeutic modality and dosage, genetic background, and idiosyncratic predispositions. Experimental treatments designed to enhance efficacy and to minimize neurotoxicity include molecularly targeted, genetic, stem cell, and immune therapies. Newer modifications in radiation and drug delivery include stereotactic radiosurgery, interstitial therapy such as intracavitary brachytherapy and gliadel wafer placement, 3D conformal radiation, boron neutron capture therapy, radiosensitizers, blood-brain barrier disrupting agents, and convection enhanced delivery. Toxicities associated with these newer modalities have yet to be fully investigated and documented. Additionally, a number of recently implemented radiographic techniques such as PET and SPECT imaging have enhanced the ability to distinguish recurrent tumor from radiation necrosis. Nevertheless, post-therapeutic brain biopsies and autopsies remain the gold standard for assessing neurotoxicity, therapeutic efficacy, tumor progression, and the development of secondary neoplasms. At the same time, treatment-associated changes such as tumor necrosis, vasculopathy, inflammation, and cytologic atypia can pose significant diagnostic pitfalls, particularly if the pathologist is not provided a detailed therapeutic history. Therefore, it is critical to recognize the full spectrum of cancer therapy-associated neuropathology, the topic of the current review.

The Burden of Radiation-Induced Central Nervous System Tumors

Radiation-induced tumors of the central and peripheral nervous systems are becoming a noticeable subset of tumors seen at referral institutions. This paper outlines a single institution s experience with 22 examples of secondary meningiomas, gliomas, and sarcomas that developed in adults. These tumors are being increasingly encountered by physicians, but the greatest burden is on the patients themselves, who not only experience the life-altering effects of the original tumor and the subsequent delayed cognitive effects of radiotherapy, but later develop a second intracranial neoplasm. We detail a particularly poignant example of a 34-year-old man who developed a high-grade sarcoma with rhabdomyosarcomatous and osteogenic elements. Local control was difficult over the next year, and he eventually developed cerebrospinal fluid dissemination and succumbed. Although radiation-induced neoplasm remain relatively infrequent numerically, each case reminds us of the need for new, less toxic, and more targeted therapies for brain neoplasms.

Specific TP53 mutation pattern in radiation-induced sarcomas

The mutagenic properties of ionizing radiation are well known, but the presence of specific mutations in human radiation-induced tumours is not established. We have studied a series of 36 secondary sarcomas arising in the irradiation field of a primary tumour following radiotherapy. The allelic status and the presence of mutations of the TP53 gene were investigated. The mutation pattern was compared with data from sporadic sarcomas recorded in the IARC TP53 somatic mutations database. A high proportion (58%) of the radiation-induced sarcomas exhibited a somatic inactivating mutation for one allele of TP53, systematically associated with a loss of the other allele. The high frequency (52%) of short deletions observed in the mutation pattern of radiation-induced sarcomas may be related to the induction of DNA breaks by ionizing radiation. The lack of hyper-reactivity of CpG dinucleotides and the presence of recurrent sites of mutation at codons 135 and 237 seem also to be specific for radiation tumorigenesis.

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

The molecular basis of tumorigenesis and tumor progression in meningiomas is not fully understood. The neurofibromatosis 2 (NF2) locus is inactivated in 50-60% of sporadic meningiomas, but the genetic basis of sporadic meningiomas not inactivated at the NF2 locus remains unclear. Specifically, there is conflicting data regarding the role of the tumor suppressor gene DAL-1/4.1B. Using microsatellite markers, we studied 63 sporadic meningiomas to determine loss of heterozygosity (LOH) at the NF2 and DAL-1/4.1B loci. Array comparative genomic hybridization analysis of 52 of these tumors was performed to determine copy number changes on chromosomes 18 and 22. Forty-one of 62 informative tumors showed LOH at the NF2 locus (66%) while only 12 of 62 informative tumors (19%) showed LOH of DAL-1/4.1B. Eleven of 12 (92%) tumors with DAL-1/4.1B LOH also had NF2 LOH. Monosomy or large deletions of chromosomes 18 and 22 were the main mechanism for LOH in these tumors. These studies implicate the DAL-1/4.1B locus in sporadic meningiomas less commonly than reported previously, and suggest that it is a progression rather than an initiation locus. Furthermore, we found the majority of meningiomas developed monosomy rather than isodisomy at the NF2 and DAL-1/4.1B loci as the mechanism for LOH.

Genotyping of patients with sporadic and radiation-associated meningiomas

Ionizing radiation is the most established risk factor for meningioma formation. Our aim was to evaluate the main effect of selected candidate genes on the development of meningioma and their possible interaction with ionizing radiation in the causation of this tumor. The total study population included 440 cases and controls: 150 meningioma patients who were irradiated for tinea capitis in childhood, 129 individuals who were similarly irradiated but did not develop meningioma, 69 meningioma patients with no previous history of irradiation, and 92 asymptomatic population controls. DNA from peripheral blood samples was genotyped for single nucleotide polymorphisms (SNP) in 12 genes: NF2, XRCC1, XRCC3, XRCC5, ERCC2, Ki-ras, p16, cyclin D1, PTEN, E-cadherin, TGFB1, and TGFBR2. SNP analysis was done using the MassArray system (Sequenom, San Diego, CA) and computerized analysis by SpectroTYPER. Logistic regressions were applied to evaluate main effect of each gene on meningioma formation and interaction between gene and radiation. Intragenic SNPs in the Ki-ras and ERCC2 genes were associated with meningioma risk (odds ratio, 1.76; 95% confidence interval, 1.07-2.92 and odds ratio, 1.68; 95% confidence interval, 1.00-2.84, respectively). A significant interaction was found between radiation and cyclin D1 and p16 SNPs (P for interaction = 0.005 and 0.057, respectively). Our findings suggest that Ki-ras and ERCC2 SNPs are possible markers for meningioma formation, whereas cyclin D1 and p16 SNPs may be markers of genes that have an inverse effect on the risk to develop meningioma in irradiated and nonirradiated populations.

p53 point mutation is rare in meningiomas from Singaporean patients

In Asian populations, meningiomas account for up to 35% of all central nervous system tumours, a significantly higher incidence than in Caucasian populations. While several studies have examined p53 both at the level of the gene and the protein in both benign and malignant meningiomas, its role remains controversial, particularly with regard to the discrepancy between p53 over-expression and gene mutation. We examined 19 benign meningiomas, all of which were known to over-express p53, and eight malignant meningiomas, of which three were known to over-express p53, for mutations in the p53 gene using polymerase chain reaction amplification and direct sequencing of exons 4 to 9, inclusive. Only one single mutation was detected in a benign meningioma, confirming that p53 over-expression in meningiomas is commonly found in the absence of gene mutations, and that despite the significantly higher incidence of meningiomas in some Asian populations, this is not associated with a significantly higher rate of p53 mutations.

Molecular pathogenesis of meningiomas

Meningiomas are common central nervous system tumors that originate from the meningeal coverings of the brain and the spinal cord. Most meningiomas are slowly growing benign tumors that histologically correspond to World Health Organization (WHO) grade I. However, certain rare histological variants (clear cell, chordoid, papillary, and rhabdoid), as well as atypical (WHO grade II) and anaplastic (WHO grade III) meningiomas show a more aggressive biological behavior and are clinically associated with a high risk of local recurrence and a less favorable prognosis. This review summarizes the most important features of meningioma pathology and provides an up-to-date overview about the molecular mechanisms involved in meningioma initiation and progression. Current data indicate that meningioma initiation is closely linked to the inactivation of one or more members of the highly conserved protein 4.1 superfamily, including the neurofibromatosis type 2 gene product merlin/schwannomin, protein 4.IB (DAL-1) and protein 4.1R. The genetic alterations in atypical meningiomas are complex and involve losses on 1p, 6q, 10, 14q and 18q, as well as gains on multiple chromosomes. The relevant genes are still unknown. Anaplastic meningiomas show even more complex genetic alterations, including frequent alteration of the CDKN2A, p14ARF, and CDKN2B tumor suppressor genes at 9p21, as well as gene amplification on 17q23. A better understanding of the molecular mechanisms involved in meningioma pathogenesis may not only lead to the identification of novel diagnostic and prognostic marker but will also facilitate the development of new pathogenesis-based therapeutic strategies.

Radiation-induced intracranial meningiomas: review of six operated cases

It is well known that radiation can induce meningiomas. These tumors usually arise in patients with a history of low-dose radiation to the scalp for treatment of tinea capitis or high-dose radiation for a previous brain tumor. Radiation-associated meningiomas (RAMs) morphologically resemble their spontaneously arising counterparts. However, RAMs frequently present a more malignant phenotype and, as such, are diagnosed as "atypical" or "aggressive" meningiomas and occur predominantly in younger patients. This paper describes six cases of radiation-associated intracranial meningiomas in patients previously treated with low-dose radiation to the scalp for tinea capitis.

Meningioma pathology, genetics, and biology

Over the past 5 to 10 years, important advances were made in the understanding of meningioma biology. Progress in molecular genetics probably represents the most important accomplishment in the comprehensive knowledge of meningioma pathogenesis. Several genes could be identified as targets for mutation or inactivation. Additional chromosomal regions were found to be commonly deleted or amplified, suggesting the presence of further tumor suppressor genes or proto-oncogenes, respectively, in these regions. Histopathologically, the most important innovation is represented by the revised WHO classification in the year 2000. Meningioma grading criteria in the new classification scheme are more precise and objective, and should thus improve consistency in predicting tumor recurrence and aggressive behavior. This review focuses mainly on the advances in molecular biology that were achieved in recent years. It summarizes the most important aspects of meningioma classification as the basis to place biological observations into a correlative context, and, further, includes mechanisms of angiogenesis and edema formation as well as the role of hormone receptors in meningiomas.

Meningiomas: Updating Basic Science, Management, and Outcome

BACKGROUND

Meningiomas are biologically complex and clinically and surgically challenging. These features, combined with the rewarding potential for cure, make them of great interest to neurologists, neurosurgeons, and neuroscientists alike.

REVIEW SUMMARY

Initially, we review the clinical context of meningiomas, particularly recent changes in histopathological classification, diagnosis, and neuroimaging. Secondly, the underlying basic science as it has evolved over the last decades is summarized. The status of areas recently of intense interest, such as steroid hormone receptors and oncogenic viruses is described. Additionally, emerging areas of great promise, such as cytogenetics and molecular biology are presented. Lastly, we describe recent advances in management. In particular, skull-base surgery, image-guided surgery, and advances in radiotherapy are emphasized. The possible impact of basic research on management and outcome is also outlined.

CONCLUSIONS

Although usually benign and amenable to cure, meningiomas still present significant diagnostic and treatment challenges. Advances in basic science, surgery, and adjuvant therapy are widening the potential for safe, effective, evidence-based management leading to even better outcomes

Prognostic value of allelic losses and telomerase activity in meningiomas

OBJECT

The goal of this study was to examine allelic losses and telomerase activity in meningiomas to determine whether they could be used to predict disease recurrence.

METHODS

To identify predictive markers of recurrence, a cohort of high-grade (24 World Health Organization [WHO] Grade II and six WHO Grade III) and low-grade (21 WHO Grade I) meningiomas was investigated for losses of heterozygosity (LOHs) on chromosomes 1p, 9p, 10q, 14q, and 22q, a deletion of CDKN2A, and telomerase activity. Results of molecular analyses were compared with radiological and histological findings and progression-free survival (PFS). Losses of heterozygosity on chromosomes 22q, 1p, and 10q, as well as telomerase activity were related to the WHO histological grades of the lesions (p < 0.01, p < 10(-5), p < 10(-4), and p = 0.002, respectively). In the absence of an LOH on 22q, the other alterations were found infrequently. Overall, the number of molecular alterations was closely related to the histological grades of the lesions (p < 10(-6)). An LOH on 22q occurred much more frequently in convexity or falx (33 [87%] of 38 lesions) than in skull base or spinal meningiomas (four [31%] of 13 lesions) (p < 0.001). The histological grade; Simpson grade; an LOH on chromosome 1p, 9p, or 10q; and telomerase activity were correlated with a shorter PFS time (p < 10(-4), p = 0.02, p = 0.000365, p = 0.022, p = 0.00027, and p = 0.000512, respectively).

CONCLUSIONS

On the basis of these data the authors suggest that LOH analysis and a telomerase activity assay could be useful to determine molecular predictors of outcome in patients with meningiomas.

Choroid plexus papilloma and meningioma: coincidental posterior fossa tumors: case report and review of the literature

OBJECTIVE

We report an unusual case of an extraventricular choroid plexus papilloma (CPP) occupying the right ventral foramen magnum and lower right cerebellopontine angle (CPA), occurring together with a petro-tentorial meningioma. The clinical presentation, preoperative imaging, differential diagnosis, surgical treatment and histologic features of the two tumors are discussed.

CASE DESCRIPTION

The patient presented with a 2-month history of headache, altered facial sensation, dysphagia, and gait unsteadiness. Neurologic examination confirmed a wide-based, unsteady gait, hoarse voice, anisocoria, and partial right vocal cord paralysis. Diagnostic imaging demonstrated right petro-tentorial and right ventral foramen magnum lesions, both hyperintense on contrasted images and suggestive of meningiomas. A right suboccipital craniotomy and far lateral approach was used to resect both tumors. The petro-tentorial tumor was a histologically confirmed meningioma, but the ventral foramen magnum tumor was an extraventricular CPP.

CONCLUSIONS

This is a rare occurrence of concomitant meningioma and CPP. There is no known link between these two tumors. An exophytic 4th ventricular CPP must be considered in the differential diagnosis of a CPA or foramen magnum tumor.

Loss of 1p and 7p in radiation-induced meningiomas identified by comparative genomic hybridization

Cytogenetic and molecular studies of radiation-induced meningiomas (RIM) are rare and controversial. While comparative genomic hybridization (CGH) analysis identified monosomy 22 as the predominant change in RIM, occurring in frequencies comparable to those found in spontaneous meningioma (SM), molecular genetic analysis shows infrequent loss of chromosome 22 DNA markers. We have performed CGH analysis of six additional cases of RIM and detected an unbalanced genome in five of 6 cases. Loss of 1p and 7p was identified in the majority of RIM with an abnormal karyotype (4/5 cases), whereas loss of 6q occurred in three of five cases. Only one of five RIM had monosomy for chromosome 22. Loss of 7p is not frequently reported in SM and yet it was detected in four of 5 RIM with an abnormal karyotype in our study. Molecular and cytogenetic studies of chromosome 7 copy number should be attempted on a larger number of RIM to further investigate the role of 7p loss in RIM.

Gamma knife radiosurgery and its possible relationship to malignancy: a review

✓ The question has been raised recently whether gamma knife radiosurgery (GKS) can induce secondary neoplasia. Because there is little or no detailed knowledge about this potential complication, background information culled from the radiotherapy literature is reviewed as a guide to the clinical situations in which radiotherapy may induce secondary neoplastic change. Available case reports are then reviewed and discussed against the background of the current knowledge. On the basis of the review, the following suggestions are proposed on how to limiting the extent of this complication, document its frequency, and inform patients. It should be remembered that: the benefits of GKS are great; its alternatives also have risks; there often are no alternatives to GKS; follow-up documentation should be pursued more actively so that, if possible, no patient falls through the net; practitioners should be proactive in defining the problem, and genetic analysis of tumor biopsy specimens obtained in patients who will undergo or have undergone GKS should become routine; the extent of secondary neoplasia is not known; and patient information should be guided by what is known rather than by what is feared.

Radiation-induced meningioma: a descriptive study of 253 cases

OBJECT

Ionizing radiation is the only established risk factor recognized today in the causation of meningioma. The aim of the present report is to describe the demographic and clinical characteristics of a large series of 253 patients with radiation-induced meningiomas (RIMs). These parameters were compared with those of 41 patients with meningiomas in whom there was no previous history of irradiation (non-RIM group) and with other series of patients presented in the literature.

METHODS

The cases of RIM were recruited from a cohort of approximately 11,000 individuals who had been treated with ionizing radiation during childhood for tinea capitis and from a group of individuals who, as adults, applied for compensation because of that treatment. The non-RIM group was identified through the Israeli Cancer Registry. Exposure to radiation was carefully validated among all cases of RIM and absence of previous irradiation was verified for all patients in the non-RIM group. Significantly, a lower patient age at diagnosis, higher prevalence of calvarial tumors, higher proportion of multiple meningiomas, and a nonsignificant higher recurrence rate were observed among patients with RIM compared with the non-RIM group. The mean latency period from date of radiation exposure to development of a meningioma among the RIM group was approximately 36 years.

CONCLUSIONS

The findings of this study agree with those of other studies indicating the demographic, clinical, and even genetic variability between RIM and non-RIM cases. The existence of two different subtypes of meningiomas may have profound implications for screening, early diagnosis, and therapy of meningiomas.