Jan Boström

Alterations of the Tumor Suppressor Genes CDKN2A (p16INK4a), p14ARF, CDKN2B (p15INK4b), and CDKN2C (p18INK4c) in Atypical and Anaplastic Meningiomas

We investigated 67 meningothelial tumors (20 benign meningiomas, 34 atypical meningiomas, and 13 anaplastic meningiomas) for losses of genetic information from chromosome arms 1p and 9p, as well as for deletion, mutation, and expression of the tumor suppressor genes CDKN2A (p16(INKa)/MTS1), p14(ARF), CDKN2B (p15(INK4b)/MTS2) (all located at 9p21) and CDKN2C (1p32). Comparative genomic hybridization and microsatellite analysis showed losses on 1p in 11 anaplastic meningiomas (85%), 23 atypical meningiomas (68%), and 5 benign meningiomas (25%). One atypical meningioma with loss of heterozygosity on 1p carried a somatic CDKN2C mutation (c.202C>T: R68X). Losses on 9p were found in five anaplastic meningiomas (38%), six atypical meningiomas (18%), and one benign meningioma (5%). Six anaplastic meningiomas (46%) and one atypical meningioma (3%) showed homozygous deletions of the CDKN2A, p14(ARF), and CDKN2B genes. Two anaplastic meningiomas carried somatic point mutations in CDKN2A (c.262G>T: E88X and c.262G>A: E88K) and p14(ARF) (c.305G>T: G102V and c.305G>A: G102E). One anaplastic meningioma, three atypical meningiomas, and one benign meningioma without a demonstrated homozygous deletion or mutation of CDKN2A, p14(ARF), or CDKN2B lacked detectable transcripts from at least one of these genes. Hypermethylation of CDKN2A, p14(ARF), and CDKN2B could be demonstrated in one of these cases. Taken together, our results indicate that CDKN2C is rarely altered in meningiomas. However, the majority of anaplastic meningiomas either show homozygous deletions of CDKN2A, p14(ARF), and CDKN2B, mutations in CDKN2A and p14(ARF), or lack of expression of one or more of these genes. Thus, inactivation of the G(1)/S-phase cell-cycle checkpoint is an important aberration in anaplastic meningiomas.

Molecular classification of diffuse cerebral WHO grade II/III gliomas using genome- and transcriptome-wide profiling improves stratification of prognostically distinct patient groups

Abstract Cerebral gliomas of World Health Organization (WHO) grade II and III represent a major challenge in terms of histological classification and clinical management. Here, we asked whether large-scale genomic and transcriptomic profiling improves the definition of prognostically distinct entities. We performed microarray-based genome- and transcriptome-wide analyses of primary tumor samples from a prospective German Glioma Network cohort of 137 patients with cerebral gliomas, including 61 WHO grade II and 76 WHO grade III tumors. Integrative bioinformatic analyses were employed to define molecular subgroups, which were then related to histology, molecular biomarkers, including isocitrate dehydrogenase 1 or 2 (IDH1/2) mutation, 1p/19q co-deletion and telomerase reverse transcriptase (TERT) promoter mutations, and patient outcome. Genomic profiling identified five distinct glioma groups, including three IDH1/2 mutant and two IDH1/2 wild-type groups. Expression profiling revealed evidence for eight transcriptionally different groups (five IDH1/2 mutant, three IDH1/2 wild type), which were only partially linked to the genomic groups. Correlation of DNA-based molecular stratification with clinical outcome allowed to define three major prognostic groups with characteristic genomic aberrations. The best prognosis was found in patients with IDH1/2 mutant and 1p/19q co-deleted tumors. Patients with IDH1/2 wild-type gliomas and glioblastoma-like genomic alterations, including gain on chromosome arm 7q (+7q), loss on chromosome arm 10q (−10q), TERT promoter mutation and oncogene amplification, displayed the worst outcome. Intermediate survival was seen in patients with IDH1/2 mutant, but 1p/19q intact, mostly astrocytic gliomas, and in patients with IDH1/2 wild-type gliomas lacking the +7q/−10q genotype and TERT promoter mutation. This molecular subgrouping stratified patients into prognostically distinct groups better than histological classification. Addition of gene expression data to this genomic classifier did not further improve prognostic stratification. In summary, DNA-based molecular profiling of WHO grade II and III gliomas distinguishes biologically distinct tumor groups and provides prognostically relevant information beyond histological classification as well as IDH1/2 mutation and 1p/19q co-deletion status.

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.

Identification of Two Distinct Deleted Regions on the Short Arm of Chromosome 1 and Rare Mutation of the CDKN2C Gene from 1p32 in Oligodendroglial Tumors

Oligodendroglial tumors frequently show allelic losses on the short arm of chromosome 1. To narrow down the putative tumor suppressor gene site(s) on 1p, we have investigated 35 oligodendrogliomas and 10 mixed gliomas (oligoastrocytomas) for loss of heterozygosity (LOH) at 21 highly polymorphic loci on chromosome 1 (19 loci on 1p and 2 loci on 1q). LOH at loci on 1p was found in 30 of the 45 tumors (67%). Two distinct regions of common allelic loss were identified: a distal region between D1S76 and D1S253 at 1p36.3, and a proximal region between D1S482 and D1S2743 at 1p34-p35. We also analyzed our tumor series for genetic alterations and expression of the cyclin dependent kinase inhibitor gene CDKN2C (p18INK4c) from 1p32. We found 1 recurrent anaplastic oligodendroglioma that carried a somatic CDKN2C mutation at codon 113 (GAA ==> TAA: Glu ==> Stop). The remaining 44 tumors of our series showed neither coding sequence mutations nor homozygous deletions of CDKN2C. Investigation of 35 tumors by differential reverse transcription-PCR revealed expression of CDKN2C transcripts in all instances. Our data thus provide evidence for more than a single oligodendroglioma-associated tumor suppressor gene on 1p and implicate CDKN2C as a candidate tumor suppressor gene altered in a low fraction of oligodendroglial tumors.

Allelic losses on chromosome arm 10q and mutation of the PTEN (MMAC1) tumour suppressor gene in primary and metastatic malignant melanomas

Abstract Malignant melanomas frequently show loss of alleles on the long arm of chromosome 10. The PTEN (MMAC1) gene has been identified as a tumour suppressor gene at 10q23.3 that is mutated in various types of advanced human cancers. We have investigated a series of 40 sporadic melanomas from 37 patients (15 primary cutaneous melanomas and 25 melanoma metastases) for allelic losses on chromosome 10, as well as for deletion and mutation of the PTEN gene. Microsatellite analysis revealed loss of heterozygosity at loci located on 10q in tumours from 15 of 34 patients investigated (44%). Somatic PTEN mutations were identified in melanomas from 4 of 37 patients (11%), all of whom had metastatic disease. In two of these patients, the tumours had additionally lost one PTEN allele, indicating complete loss of wild-type PTEN in the tumour cells. Our findings corroborate that loss of heterozygosity on chromosome 10 is a frequent aberration in malignant melanomas and implicate PTEN as a tumour suppressor gene inactivated by somatic mutation in a fraction of these tumours.

Interinstitutional variance of postoperative radiotherapy and follow up for meningiomas in Germany: impact of changes of the WHO classification

Objective: To document and critically analyse the impact of the revised WHO 2000 histological classification for meningiomas on postoperative radiotherapy/radiosurgery indications and MRI follow up protocols. Methods: The current (2000) WHO classification was used to grade 57 meningiomas treated surgically at one institution. These had been reviewed previously in 1999. All German neurosurgical departments carrying out intracranial microsurgery were asked to detail their guidelines for radiation therapy and follow up for meningiomas of different WHO grades. Results: Use of the current criteria downgraded seven of 15 atypical meningiomas (WHO grade II, MII) to grade I (MI), and four of six anaplastic tumours (WHO grade III, MIII) to grade II. Indications for radiotherapy/radiosurgery and MRI follow up protocols varied substantially with the histological grade and between institutions—for example, after an incomplete resection, radiotherapy/radiosurgery recommendations differed between MI and MII in 30 of 58 units (52%), and between MII and MIII in 34 of 56 units (61%). Conclusions: Correlative studies combining treatment and outcome data with a standardised histopathological analysis are warranted to define properly the indications for radiotherapy/radiosurgery and follow up protocols after surgery for meningiomas of different histological grades. The use of changing grading paradigms during recent years renders decision making based on local and published experience difficult. The relatively large number of meningiomas classified as atypical/WHO grade II in current practice would argue against an uncritically aggressive approach to these tumours.

Alterations of INK4ap16—p14ARF/INK4bp15 Expression and Telomerase Activation in Meningioma Progression

Dysregulation of cell cycle progression and telomerase activation have been implicated in malignant tumor progression as well as in the evasion of senescence and immortalization. We have investigated expression of the cell cycle control and tumor suppressor genes INK4ap16–p14ARF, INK4bp15–p10 and RB, and their relation to telomerase activation during malignant meningioma progression. 7/26 (27%) benign, 3/12 (25%) atypical but 4/7 (57%) anaplastic tumors lacked both, p16 and p15 protein expression. 14/39 (36%) benign and atypical but 5/7 (71%) anaplastic meningiomas contained no p14ARF mRNA. 2/46 (4%) tumors failed to express pRB. We observed frequent differential loss of expression of the alternatively spliced INK4a tumor suppressors p16 and p14ARF. Exclusive expression of the alternative INK4b transcript p10 possibly at the expense of p15 and therefore resulting in loss of p15 tumor suppressor activity was noted in two meningiomas. We have previously described telomerase activity or expression of the telomerase catalytic subunit hTERT in this meningioma series. Telomerase activation was detected in 10/27 (37%) benign, but 18/19 (95%) non-benign meningiomas. We observed no significant overall correlation between loss of INK4a/INK4b expression and telomerase activation. In conclusion, our results suggest a greater role for losses of INK4a/INK4b gene products in meningioma formation and malignant progression than previously thought. Inactivation of p16/p15- and p14ARF-dependent pathways possibly in conjunction with telomerase activation might be critical steps for a meningioma cell towards escape from senescence, that is, immortalization.

Analysis of human meningiomas for aberrations of the MADH2, MADH4, APM‐1 and DCC tumor suppressor genes on the long arm of chromosome 18

We have previously reported that losses of genomic material from the long arm of chromosome 18 are frequent in atypical and anaplastic meningiomas but rare in benign meningiomas. In the present study, we have investigated a series of 37 meningiomas for mutation and expression of 4 tumor suppressor genes (MADH2, MADH4, APM‐1 and DCC) located at 18q21. Comparative genomic hybridization or loss of heterozygosity analysis showed losses on chromosome 18 that included sequences from 18q21 in 15 of 37 tumors. Mutation analysis of APM‐1revealed a missense mutation (c. 1819G>A: G607S) in 1 atypical meningioma. None of the tumors showed mutations of MADH2 and MADH4 or loss of detectable transcripts from MADH2, MADH4, APM‐1and DCC. In contrast to human brain tissue, normal leptomeninges and meningiomas showed preferential expression of a DCC splice variant lacking 60 base pairs from exon 17. Taken together, our data do not support a significant role for MADH2, MADH4, APM‐1 and DCC alterations in the pathogenesis of meningiomas. The targeted gene that is inactivated in most meningiomas with 18q losses remains to be identified.

Management and outcome in adult intramedullary spinal cord tumours: a 20-year single institution experience

BackgroundSeveral uncertainties remain concerning the management of intramedullary spinal cord tumours (IMSCTs). These include the timing and extent of resection, its interrelated functional outcome, and the adequate use and timing of radiation therapy and/or chemotherapy. In this retrospective study we report on all adult cases involving IMSCTs treated from 1987 to 2007 in our institution to validate our treatment strategy for IMSCTs. Pre- and post-operative functional performance was classified according to the McCormick scale.ResultsA total of 70 adult cases with IMSCTs consisting of ependymoma (39), astrocytoma (11), carcinoma metastasis (8), haemangioblastoma (5), cavernoma (3) and others (4) were reviewed. Mean age was 46.8 years (range, 18-79 years), and mean follow-up was 4.5 years (range, 1-195 months). The proportion of localisation in descending order was thoracic (36%), cervical (33%), cervicothoracic (19%) and conus region (13%), with 45 gross total resections, 22 partial resections and three biopsies. Surgery-related morbidity with worsening postoperative symptoms occurred immediately in 13 patients (18.6%). The preoperative McCormick grade correlated significantly with the early postoperative grade and the grade at follow-up (χ2-test; p = 0.001). None of the patients with preserved intraoperative evoked potentials exhibited significant postoperative deterioration. The degree of resection was correlated with progression-free survival (Duncan test; p = 0.05). Most patients with malignant tumours, namely anaplastic ependymoma (3), astrocytoma (2) or metastatic lesions (5), underwent postoperative radiation therapy. Six patients (one anaplastic ependymoma, two anaplastic astrocytomas and three metastatic lesions) received postoperative chemotherapy.ConclusionsIMSCTs should be operated on when symptoms are mild. We recommend evoked potential-guided microsurgical total resection of ependymomas and other benign lesions; partial resection or biopsy followed by adjuvant therapy should be confined to patients with high-grade astrocytomas, whereas resection or biopsy with adjuvant therapy is the best option for metastatic lesions.

Factors of influence upon overall survival in the treatment of intracranial MPNSTs. Review of the literature and report of a case

BackgroundIntracranial malignant peripheral nerve sheath tumors are rare entities that carry a poor prognosis. To date, there are no established therapeutic strategies for these tumors.MethodsWe review the present treatment modalities and present the current therapeutic dilemmas. We perform a statistical analysis to evaluate the prognostic factors for Overall Survival of these patients. Additionally, we present our experience with a 64-year-old man with a MPNST of the left cerebellopontine angle.ResultsTo our best knowledge, forty three patients with intracranial MPNSTs, including our case, have been published in the international literature. Our analysis showed gross total resection, radiotherapy and female gender to be beneficial prognostic factors of survival in the univariate analysis. Gross total resection was recognized as the only independent predictor of prolonged Overall Survival. In our case, we performed a gross total resection followed for the first time by stereotactically guided radiotherapy.ConclusionConsidering the results of the statistical analysis and the known advantages of the stereotaxy, we suggest aggressive surgery followed by stereotactically guided radiotherapy as therapy of choice.