Chromosomal and genetic aberrations differ with meningioma subtype

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.

Lyophilized brain tumor specimens can be used for histologic, nucleic acid, and protein analyses after 1 year of room temperature storage

Frozen tissue, a gold standard biospecimen, can yield well preserved nucleic acids and proteins after over a decade but is vulnerable to thawing and has substantial fiscal, spatial, and environmental costs. A long-term room temperature biospecimen storage alternative that preserves broad analytical utility can potentially empower tissue-based research. As there is scant data on the analytical utility of lyophilized brain tumor biospecimens, we evaluated lyophilized (freeze-dried) samples stored for 1 year at room temperature. Lyophilized tumor tissue processed into paraffin sections produced good histology. Yields of extracted DNA, RNA, and protein approximated those of frozen tissue. After 1 year, lyophilized samples yielded high molecular weight DNA that permitted copy number variation analysis, IDH 1 mutation detection, and MGMT promoter methylation PCR. A 27 % decrease in RIN scores over the 1 year suggests that RNA degradation was inhibited though incompletely. Nevertheless, RT-PCR studies on lyophilized tissue performed similarly to frozen tissue. In contrast to FFPE tissues where protein bands were absent or shifted to a lower molecular weight, lyophilized samples showed similar protein bands as frozen tissue on SDS-PAGE analysis. Lyophilized tissue performed similarly to frozen tissue for Western blots and enzyme activity assays. Immunohistochemistry of lyophilized tissue that were processed into FFPE blocks often required longer incubation times for staining than standard FFPE samples but generally provided robust antigen detection. This preliminary study suggests that lyophilization has promise for long-term room temperature storage while permitting varied tests; however, further work is required to better stabilize nucleic acids particularly RNA.

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.

Novel chromosomal aberrations in a recurrent malignant meningioma

The molecular basis of tumorigenesis and tumor progression in meningiomas is not fully understood. Here we present results of conventional cytogenetic, fluorescence in situ hybridization (FISH), and comparative genetic hybridization (CGH) analyses in a patient with recurrent anaplastic meningioma. We found complex aberrant karyotype alterations previously described in anaplastic meningiomas, such as 1p, 14q aberration, and a possibly tetraploid karyotype. Loss of chromosome 22q was detected by conventional cytogenetic analysis. Additional chromosomal aberrations not previously reported included a near-triploid karyotype and alterations such as 4p+, 5p-, 7p+, 8q+, and gain of chromosome 19. FISH with LSI 9p21, CEP9, LSI PML/RARA, and CGH confirmed the karyotype complexity in this case. Our findings of several previously unreported cytogenetic alterations suggest that complex karyotype alterations are a characteristic feature in anaplastic meningiomas. High chromosomal complexity might be associated with a highly aggressive meningioma phenotype.

From array to array: Confirmation of genomic gains and losses discovered by array-based comparative genomic hybridization utilizing fluorescence in situ hybridization on tissue microarrays

The combination of array-based comparative genomic hybridization (CGH) with fluorescence in situ hybridization utilizing custom-designed bacterial artificial chromosome (BAC) probes applied to tissue microarrays represents a powerful compendium of techniques-greatly enhancing the throughput of genomic analysis and subsequent target validation. Such approach can be automated at various levels and allows managing large volume of targets and samples in a few experiments. As such, this approach facilitates discovery, validation and implementation of findings in the process of identification of new diagnostic, prognostic and potentially therapeutic molecular markers.

Recurrent cytogenetic aberrations in histologically benign, invasive meningiomas of the sphenoid region

Meningiomas that arise in the sphenoid region (MSR) often display growth patterns leading to widespread invasion and destruction of the surrounding structures. Consequently, there is still estimated recurrence rate up to 30% with MSR. Conventional cytogenetic studies have failed to reveal aberrations characteristic of invasive meningiomas. Here we investigated 10 invasive and 5 non-invasive MSR using the array-based comparative genomic hybridization (array-CGH) with the GenoSensor Array 300. Mean number of aberrations detected per tumor was significantly greater for invasive meningiomas-67.4 compared with 40.5 for non-invasive MSR. Additionally, invasive MSR disclosed frequent losses on 1p, 6q, 14q and gains on 15q and 20, which were identified previously as molecular hallmarks of stepwise meningioma progression. Thus, the presence of a complex cytogenetic profile and progression-associated chromosomal aberrations in benign MSR is associated with their increased invasive potential. Inasmuch as no reliable adjuvant therapy for recurrent meningiomas is available thus far, revealed genomic aberrations can provide a potential targets for drug discovery and therapeutic intervention in a future.

Genetic and epigenetic biomarkers in cancer diagnosis and identifying high risk populations

Biomarkers present the normal and/or disease state in humans. Genetic and epigenetic biomarkers assessed in easily accessible biological materials are useful in diagnosis, early onset or risk of developing cancer or to predict the treatment efficacy or clinical outcome of different human malignancies. Moreover, some of these markers are expressed during early stages of the tumor development and hence provide an opportunity to develop intervention and treatment strategies. Attempts are being made to validate cancer biomarkers in non-invasively collected samples. Multiplexing of clinically validated markers is still a challenge. Once validated, these markers can be utilized in clinical settings and to identify high risk populations. In this review, the current status of the clinical genetic and epigenetic biomarkers and their implication in cancer diagnosis and risk assessment are discussed.

Meningothelioma as the predominant histological subtype of midline skull base and spinal meningioma

Object

This study was undertaken to test a hypothesis that meningiomas of the midline skull base and spine are predominantly of the meningothelial histological subtype.

Methods

The cases of 794 consecutive patients who underwent resection for meningioma at the Cleveland Clinic between January 1991 and March 2004 were reviewed retrospectively. The authors analyzed the relationship between the tumors’ histological subtypes and sites of origin in the 731 patients from this group who harbored tumors that were determined to be benign histologically (World Health Organization Grade I).

Meningothelial meningiomas (MMs) accounted for 63.5% (464/731) of the Grade I tumors. The incidence of MM according to the site of origin was as follows: 84.9% (186/219) in the midline skull base, 58.3% (35/60) in the lateral skull base, 48.5% (183/377) in a non–skull base location, and 80% (60/75) in spinal locations. The incidence of MM in the midline skull base and spinal locations were significantly higher than in non–skull base or lateral skull base locations.

Conclusions

Meningiomas of the midline neuraxis are predominantly meningotheliomas. Analysis of the increasingly available data on genetic and topographic characteristics of MMs suggests that they may represent a unique entity, contrary to the prevailing belief that all benign meningiomas are identical tumors.