Subgroup and subtype-specific outcomes in adult medulloblastoma.

Medulloblastoma, a common pediatric malignant central nervous system tumour, represent a small proportion of brain tumours in adults. Previously it has been shown that in adults, Sonic Hedgehog (SHH)-activated tumours predominate, with Wingless-type (WNT) and Group 4 being less common, but molecular risk stratification remains a challenge. We performed an integrated analysis consisting of genome-wide methylation profiling, copy number profiling, somatic nucleotide variants and correlation of clinical variables across a cohort of 191 adult medulloblastoma cases identified through the Medulloblastoma Advanced Genomics International Consortium. We identified 30 WNT, 112 SHH, 6 Group 3, and 41 Group 4 tumours. Patients with SHH tumours were significantly older at diagnosis compared to other subgroups (p < 0.0001). Five-year progression-free survival (PFS) for WNT, SHH, Group 3, and Group 4 tumours was 64.4 (48.0-86.5), 61.9% (51.6-74.2), 80.0% (95% CI 51.6-100.0), and 44.9% (95% CI 28.6-70.7), respectively (p = 0.06). None of the clinical variables (age, sex, metastatic status, extent of resection, chemotherapy, radiotherapy) were associated with subgroup-specific PFS. Survival among patients with SHH tumours was significantly worse for cases with chromosome 3p loss (HR 2.9, 95% CI 1.1-7.6; p = 0.02), chromosome 10q loss (HR 4.6, 95% CI 2.3-9.4; p < 0.0001), chromosome 17p loss (HR 2.3, 95% CI 1.1-4.8; p = 0.02), and PTCH1 mutations (HR 2.6, 95% CI 1.1-6.2; p = 0.04). The prognostic significance of 3p loss and 10q loss persisted in multivariable regression models. For Group 4 tumours, chromosome 8 loss was strongly associated with improved survival, which was validated in a non-overlapping cohort (combined cohort HR 0.2, 95% CI 0.1-0.7; p = 0.007). Unlike in pediatric medulloblastoma, whole chromosome 11 loss in Group 4 and chromosome 14q loss in SHH was not associated with improved survival, where MYCN, GLI2 and MYC amplification were rare. In sum, we report unique subgroup-specific cytogenetic features of adult medulloblastoma, which are distinct from those in younger patients, and correlate with survival disparities. Our findings suggest that clinical trials that incorporate new strategies tailored to high-risk adult medulloblastoma patients are urgently needed.

Leptomeningeal dissemination: a sinister pattern of medulloblastoma growth.

Leptomeningeal dissemination (LMD) is the defining pattern of metastasis for medulloblastoma. Although LMD is responsible for virtually 100% of medulloblastoma deaths, it remains the least well-understood part of medulloblastoma pathogenesis. The fact that medulloblastomas rarely metastasize outside the CNS but rather spread almost exclusively to the spinal and intracranial leptomeninges has fostered the long-held belief that medulloblastoma cells spread directly through the CSF, not the bloodstream. In this paper the authors discuss selected molecules for which experimental evidence explains how the effects of each molecule on cell physiology contribute mechanistically to LMD. A model of medulloblastoma LMD is described, analogous to the invasion-metastasis cascade of hematogenous metastasis of carcinomas. The LMD cascade is based on the molecular themes that 1) transcription factors launch cell programs that mediate cell motility and invasiveness and maintain tumor cells in a stem-like state; 2) disseminating medulloblastoma cells escape multiple death threats by subverting apoptosis; and 3) inflammatory chemokine signaling promotes LMD by creating an oncogenic microenvironment. The authors also review recent experimental evidence that challenges the belief that CSF spread is the sole mechanism of LMD and reveal an alternative scheme in which medulloblastoma cells can enter the bloodstream and subsequently home to the leptomeninges.

Spectrum and prevalence of genetic predisposition in medulloblastoma: a retrospective genetic study and prospective validation in a clinical trial cohort.

BACKGROUND: Medulloblastoma is associated with rare hereditary cancer predisposition syndromes; however, consensus medulloblastoma predisposition genes have not been defined and screening guidelines for genetic counselling and testing for paediatric patients are not available. We aimed to assess and define these genes to provide evidence for future screening guidelines. METHODS: In this international, multicentre study, we analysed patients with medulloblastoma from retrospective cohorts (International Cancer Genome Consortium [ICGC] PedBrain, Medulloblastoma Advanced Genomics International Consortium [MAGIC], and the CEFALO series) and from prospective cohorts from four clinical studies (SJMB03, SJMB12, SJYC07, and I-HIT-MED). Whole-genome sequences and exome sequences from blood and tumour samples were analysed for rare damaging germline mutations in cancer predisposition genes. DNA methylation profiling was done to determine consensus molecular subgroups: WNT (MBWNT), SHH (MBSHH), group 3 (MBGroup3), and group 4 (MBGroup4). Medulloblastoma predisposition genes were predicted on the basis of rare variant burden tests against controls without a cancer diagnosis from the Exome Aggregation Consortium (ExAC). Previously defined somatic mutational signatures were used to further classify medulloblastoma genomes into two groups, a clock-like group (signatures 1 and 5) and a homologous recombination repair deficiency-like group (signatures 3 and 8), and chromothripsis was investigated using previously established criteria. Progression-free survival and overall survival were modelled for patients with a genetic predisposition to medulloblastoma. FINDINGS: We included a total of 1022 patients with medulloblastoma from the retrospective cohorts (n=673) and the four prospective studies (n=349), from whom blood samples (n=1022) and tumour samples (n=800) were analysed for germline mutations in 110 cancer predisposition genes. In our rare variant burden analysis, we compared these against 53 105 sequenced controls from ExAC and identified APC, BRCA2, PALB2, PTCH1, SUFU, and TP53 as consensus medulloblastoma predisposition genes according to our rare variant burden analysis and estimated that germline mutations accounted for 6% of medulloblastoma diagnoses in the retrospective cohort. The prevalence of genetic predispositions differed between molecular subgroups in the retrospective cohort and was highest for patients in the MBSHH subgroup (20% in the retrospective cohort). These estimates were replicated in the prospective clinical cohort (germline mutations accounted for 5% of medulloblastoma diagnoses, with the highest prevalence [14%] in the MBSHH subgroup). Patients with germline APC mutations developed MBWNT and accounted for most (five [71%] of seven) cases of MBWNT that had no somatic CTNNB1 exon 3 mutations. Patients with germline mutations in SUFU and PTCH1 mostly developed infant MBSHH. Germline TP53 mutations presented only in childhood patients in the MBSHH subgroup and explained more than half (eight [57%] of 14) of all chromothripsis events in this subgroup. Germline mutations in PALB2 and BRCA2 were observed across the MBSHH, MBGroup3, and MBGroup4 molecular subgroups and were associated with mutational signatures typical of homologous recombination repair deficiency. In patients with a genetic predisposition to medulloblastoma, 5-year progression-free survival was 52% (95% CI 40-69) and 5-year overall survival was 65% (95% CI 52-81); these survival estimates differed significantly across patients with germline mutations in different medulloblastoma predisposition genes. INTERPRETATION: Genetic counselling and testing should be used as a standard-of-care procedure in patients with MBWNT and MBSHH because these patients have the highest prevalence of damaging germline mutations in known cancer predisposition genes. We propose criteria for routine genetic screening for patients with medulloblastoma based on clinical and molecular tumour characteristics. FUNDING: German Cancer Aid; German Federal Ministry of Education and Research; German Childhood Cancer Foundation (Deutsche Kinderkrebsstiftung); European Research Council; National Institutes of Health; Canadian Institutes for Health Research; German Cancer Research Center; St Jude Comprehensive Cancer Center; American Lebanese Syrian Associated Charities; Swiss National Science Foundation; European Molecular Biology Organization; Cancer Research UK; Hertie Foundation; Alexander and Margaret Stewart Trust; V Foundation for Cancer Research; Sontag Foundation; Musicians Against Childhood Cancer; BC Cancer Foundation; Swedish Council for Health, Working Life and Welfare; Swedish Research Council; Swedish Cancer Society; the Swedish Radiation Protection Authority; Danish Strategic Research Council; Swiss Federal Office of Public Health; Swiss Research Foundation on Mobile Communication; Masaryk University; Ministry of Health of the Czech Republic; Research Council of Norway; Genome Canada; Genome BC; Terry Fox Research Institute; Ontario Institute for Cancer Research; Pediatric Oncology Group of Ontario; The Family of Kathleen Lorette and the Clark H Smith Brain Tumour Centre; Montreal Children's Hospital Foundation; The Hospital for Sick Children: Sonia and Arthur Labatt Brain Tumour Research Centre, Chief of Research Fund, Cancer Genetics Program, Garron Family Cancer Centre, MDT's Garron Family Endowment; BC Childhood Cancer Parents Association; Cure Search Foundation; Pediatric Brain Tumor Foundation; Brainchild; and the Government of Ontario.

Application of 3-Dimensional Printing in a Case of Osteogenesis Imperfecta for Patient Education, Anatomic Understanding, Preoperative Planning, and Intraoperative Evaluation.

BACKGROUND: The techniques and applications of 3-dimensional (3D) printing have progressed at a fast pace. In the last 10 years, there has been significant progress in applying this technology to medical applications. We present a case of osteogenesis imperfecta in which treatment was aided by prospectively using patient-specific, anatomically accurate 3D prints of the calvaria. The patient-specific, anatomically accurate 3D prints were used in the clinic and in the operating room to augment patient education, improve surgical decision making, and enhance preoperative planning. CASE DESCRIPTION: A 41-year-old woman with osteogenesis imperfecta and an extensive neurosurgical history presented for cranioplasty revision. Computed tomography (CT) data obtained as part of routine preoperative imaging were processed into a 3D model. The 3D patient-specific models were used in the clinic for patient education and in the operating room for preoperative visualization, planning, and intraoperative evaluation of anatomy. The patient reported the 3D models improved her understanding and comfort with the planned surgery when compared with discussing the procedure with the neurosurgeon or viewing the CT images with a neuroradiologist. The neurosurgeon reported an improved understanding of the patient's anatomy and potential cause of patient symptoms as well as improved preoperative planning compared with viewing the CT imaging alone. The neurosurgeon also reported an improvement in the planned surgical approach with a better intraoperative visualization and confirmation of the regions of planned calvarial resection. CONCLUSIONS: The use of patient-specific, anatomically accurate 3D prints may improve patient education, surgeon understanding and visualization, preoperative decision making, and intraoperative management.

IGFBP2 expression predicts IDH-mutant glioma patient survival.

Mutations of the isocitrate dehydrogenase (IDH) 1 and 2 genes occur in ~80% of lower-grade (WHO grade II and grade III) gliomas. Mutant IDH produces (R)-2-hydroxyglutarate, which induces DNA hypermethylation and presumably drives tumorigenesis. Interestingly, IDH mutations are associated with improved survival in glioma patients, but the underlying mechanism for the difference in survival remains unclear. Through comparative analyses of 286 cases of IDH-wildtype and IDH-mutant lower-grade glioma from a TCGA data set, we report that IDH-mutant gliomas have increased expression of tumor-suppressor genes (NF1, PTEN, and PIK3R1) and decreased expression of oncogenes(AKT2, ARAF, ERBB2, FGFR3, and PDGFRB) and glioma progression genes (FOXM1, IGFBP2, and WWTR1) compared with IDH-wildtype gliomas. Furthermore, each of these genes is prognostic in overall gliomas; however, within the IDH-mutant group, none remains prognostic except IGFBP2 (encodinginsulin-like growth factor binding protein 2). Through validation in an independent cohort, we show that patients with low IGFBP2 expressiondisplay a clear advantage in overall and disease-free survival, whereas those with high IGFBP2 expressionhave worse median survival than IDH-wildtype patients. These observations hold true across different histological and molecular subtypes of lower-grade glioma. We propose therefore that an unexpected biological consequence of IDH mutations in glioma is to ameliorate patient survival by promoting tumor-suppressor signaling while inhibiting that of oncogenes, particularly IGFBP2.

Somatic cell transfer of c-Myc and Bcl-2 induces large-cell anaplastic medulloblastomas in mice.

A highly aggressive subgroup of the pediatric brain tumor medulloblastoma is characterized by overexpression of the proto-oncogene c-Myc, which encodes a transcription factor that normally maintains neural progenitor cells in an undifferentiated, proliferating state during embryonic development. Myc-driven medulloblastomas typically show a large-cell anaplastic (LCA) histological pattern, in which tumor cells display large, round nuclei with prominent nucleoli. This subgroup of medulloblastoma is therapeutically challenging because it is associated with a high rate of metastatic dissemination, which is a powerful predictor of short patient survival times. Genetically engineered mouse models have revealed important insights into the pathogenesis of medulloblastoma and served as preclinical testing platforms for new therapies. Here we report a new mouse model of Myc-driven medulloblastoma, in which tumors arise in situ after retroviral transfer and expression of Myc in Nestin-expressing neural progenitor cells in the cerebella of newborn mice. Tumor induction required concomitant loss of Tp53 or overexpression of the antiapoptotic protein Bcl-2. Like Myc-driven medulloblastomas in humans, the tumors induced in mice by Myc + Bcl-2 and Myc - Tp53 showed LCA cytoarchitecture and a high rate of metastatic dissemination to the spine. The fact that Myc - Tp53 tumors arose only in Tp53(-/-) mice, coupled with the inefficient germline transmission of the Tp53-null allele, made retroviral transfer of Myc + Bcl-2 a more practical method for generating LCA medulloblastomas. The high rate of spinal metastasis (87% of brain tumor-bearing mice) will be an asset for testing new therapies that target the most lethal aspect of medulloblastoma.

Molecular Classification of Ependymal Tumors across All CNS Compartments, Histopathological Grades, and Age Groups.

Ependymal tumors across age groups are currently classified and graded solely by histopathology. It is, however, commonly accepted that this classification scheme has limited clinical utility based on its lack of reproducibility in predicting patients' outcome. We aimed at establishing a uniform molecular classification using DNA methylation profiling. Nine molecular subgroups were identified in a large cohort of 500 tumors, 3 in each anatomical compartment of the CNS, spine, posterior fossa, supratentorial. Two supratentorial subgroups are characterized by prototypic fusion genes involving RELA and YAP1, respectively. Regarding clinical associations, the molecular classification proposed herein outperforms the current histopathological classification and thus might serve as a basis for the next World Health Organization classification of CNS tumors.

Molecular subgroups of atypical teratoid rhabdoid tumours in children: an integrated genomic and clinicopathological analysis.

BACKGROUND: Rhabdoid brain tumours, also called atypical teratoid rhabdoid tumours, are lethal childhood cancers with characteristic genetic alterations of SMARCB1/hSNF5. Lack of biological understanding of the substantial clinical heterogeneity of these tumours restricts therapeutic advances. We integrated genomic and clinicopathological analyses of a cohort of patients with atypical teratoid rhabdoid tumours to find out the molecular basis for clinical heterogeneity in these tumours. METHODS: We obtained 259 rhabdoid tumours from 37 international institutions and assessed transcriptional profiles in 43 primary tumours and copy number profiles in 38 primary tumours to discover molecular subgroups of atypical teratoid rhabdoid tumours. We used gene and pathway enrichment analyses to discover group-specific molecular markers and did immunohistochemical analyses on 125 primary tumours to evaluate clinicopathological significance of molecular subgroup and ASCL1-NOTCH signalling. FINDINGS: Transcriptional analyses identified two atypical teratoid rhabdoid tumour subgroups with differential enrichment of genetic pathways, and distinct clinicopathological and survival features. Expression of ASCL1, a regulator of NOTCH signalling, correlated with supratentorial location (p=0·004) and superior 5-year overall survival (35%, 95% CI 13-57, and 20%, 6-34, for ASCL1-positive and ASCL1-negative tumours, respectively; p=0·033) in 70 patients who received multimodal treatment. ASCL1 expression also correlated with superior 5-year overall survival (34%, 7-61, and 9%, 0-21, for ASCL1-positive and ASCL1-negative tumours, respectively; p=0·001) in 39 patients who received only chemotherapy without radiation. Cox hazard ratios for overall survival in patients with differential ASCL1 enrichment treated with chemotherapy with or without radiation were 2·02 (95% CI 1·04-3·85; p=0·038) and 3·98 (1·71-9·26; p=0·001). Integrated analyses of molecular subgroupings with clinical prognostic factors showed three distinct clinical risk groups of tumours with different therapeutic outcomes. INTERPRETATION: An integration of clinical risk factors and tumour molecular groups can be used to identify patients who are likely to have improved long-term radiation-free survival and might help therapeutic stratification of patients with atypical teratoid rhabdoid tumours. FUNDING: C17 Research Network, Genome Canada, b.r.a.i.n.child, Mitchell Duckman, Tal Doron and Suri Boon foundations.

Genetic drivers of metastatic dissemination in sonic hedgehog medulloblastoma.

Leptomeningeal dissemination (LMD), the metastatic spread of tumor cells via the cerebrospinal fluid to the brain and spinal cord, is an ominous prognostic sign for patients with the pediatric brain tumor medulloblastoma. The need to reduce the risk of LMD has driven the development of aggressive treatment regimens, which cause disabling neurotoxic side effects in long-term survivors. Transposon-mediated mutagenesis studies in mice have revealed numerous candidate metastasis genes. Understanding how these genes drive LMD will require functional assessment using in vivo and cell culture models of medulloblastoma. We analyzed two genes that were sites of frequent transposon insertion and highly expressed in human medulloblastomas: Arnt (aryl hydrocarbon receptor nuclear translocator) and Gdi2 (GDP dissociation inhibitor 2). Here we show that ectopic expression of Arnt and Gdi2 promoted LMD in mice bearing Sonic hedgehog (Shh)-induced medulloblastomas. We overexpressed Arnt and Gdi2 in a human medulloblastoma cell line (DAOY) and an immortalized, nontransformed cell line derived from mouse granule neuron precursors (SHH-NPD) and quantified migration, invasiveness, and anchorage-independent growth, cell traits that are associated with metastatic competence in carcinomas. In SHH-NPD cells. Arnt and Gdi2 stimulated all three traits. In DAOY cells, Arnt had the same effects, but Gdi2 stimulated invasiveness only. These results support a mechanism whereby Arnt and Gdi2 cause cells to detach from the primary tumor mass by increasing cell motility and invasiveness. By conferring to tumor cells the ability to proliferate without surface attachment, Arnt and Gdi2 favor the formation of stable colonies of cells capable of seeding the leptomeninges.

TERT promoter mutations are highly recurrent in SHH subgroup medulloblastoma.

Telomerase reverse transcriptase (TERT) promoter mutations were recently shown to drive telomerase activity in various cancer types, including medulloblastoma. However, the clinical and biological implications of TERT mutations in medulloblastoma have not been described. Hence, we sought to describe these mutations and their impact in a subgroup-specific manner. We analyzed the TERT promoter by direct sequencing and genotyping in 466 medulloblastomas. The mutational distributions were determined according to subgroup affiliation, demographics, and clinical, prognostic, and molecular features. Integrated genomics approaches were used to identify specific somatic copy number alterations in TERT promoter-mutated and wild-type tumors. Overall, TERT promoter mutations were identified in 21 % of medulloblastomas. Strikingly, the highest frequencies of TERT mutations were observed in SHH (83 %; 55/66) and WNT (31 %; 4/13) medulloblastomas derived from adult patients. Group 3 and Group 4 harbored this alteration in <5 % of cases and showed no association with increased patient age. The prognostic implications of these mutations were highly subgroup-specific. TERT mutations identified a subset with good and poor prognosis in SHH and Group 4 tumors, respectively. Monosomy 6 was mostly restricted to WNT tumors without TERT mutations. Hallmark SHH focal copy number aberrations and chromosome 10q deletion were mutually exclusive with TERT mutations within SHH tumors. TERT promoter mutations are the most common recurrent somatic point mutation in medulloblastoma, and are very highly enriched in adult SHH and WNT tumors. TERT mutations define a subset of SHH medulloblastoma with distinct demographics, cytogenetics, and outcomes.

Glioblastoma presenting with steroid-induced pseudoregression of contrast enhancement on magnetic resonance imaging.

Corticosteroid-induced reduction in contrast enhancement on radiographic imaging is most commonly associated with lymphoma but has been reported in other entities, including glioma. This finding may represent a diagnostic dilemma. Concern that steroid-induced cytotoxicity obscures histological diagnosis of suspected lymphoma may lead to postponement of a biopsy. If glioma is not considered in the differential diagnosis, reduction in tumor contrast enhancement may be misinterpreted as disease regression rather than a transient radiographic change. We report a case of a patient with an enhancing right temporoparietal mass adjacent to the atrium of the lateral ventricle. After treatment with dexamethasone was started, the mass exhibited marked reduction in contrast enhancement, with symptom improvement. The clinical course suggested lymphoma, and surgery was not performed. Subsequent screening for extra-axial lymphoma was negative. Two weeks later, the patient developed worsening symptoms, and repeat T1-weighted imaging showed interval increase in size and enhancement. The findings suggested a possible diagnosis of malignant glioma. The patient underwent a stereotactic-guided craniotomy for excision of the right temporoparietal mass lesion. Final histological diagnosis was glioblastoma multiforme, World Health Organization grade IV.

Functional genomics identifies drivers of medulloblastoma dissemination.

Medulloblastomas are malignant brain tumors that arise in the cerebellum in children and disseminate via the cerebrospinal fluid to the leptomeningeal spaces of the brain and spinal cord. Challenged by the poor prognosis for patients with metastatic dissemination, pediatric oncologists have developed aggressive treatment protocols, combining surgery, craniospinal radiation, and high-dose chemotherapy, that often cause disabling neurotoxic effects in long-term survivors. Insights into the genetic control of medulloblastoma dissemination have come from transposon insertion mutagenesis studies. Mobilizing the Sleeping Beauty transposon in cerebellar neural progenitor cells caused widespread dissemination of typically nonmetastatic medulloblastomas in Patched(+/-) mice, in which Shh signaling is hyperactive. Candidate metastasis genes were identified by sequencing the insertion sites and then mapping these sequences back to the mouse genome. To determine whether genes located at transposon insertion sites directly caused medulloblastomas to disseminate, we overexpressed candidate genes in Nestin(+) neural progenitors in the cerebella of mice by retroviral transfer in combination with Shh. We show here that ectopic expression of Eras, Lhx1, Ccrk, and Akt shifted the in vivo growth characteristics of Shh-induced medulloblastomas from a localized pattern to a disseminated pattern in which tumor cells seeded the leptomeningeal spaces of the brain and spinal cord.

Clonal selection drives genetic divergence of metastatic medulloblastoma.

Medulloblastoma, the most common malignant paediatric brain tumour, arises in the cerebellum and disseminates through the cerebrospinal fluid in the leptomeningeal space to coat the brain and spinal cord. Dissemination, a marker of poor prognosis, is found in up to 40% of children at diagnosis and in most children at the time of recurrence. Affected children therefore are treated with radiation to the entire developing brain and spinal cord, followed by high-dose chemotherapy, with the ensuing deleterious effects on the developing nervous system. The mechanisms of dissemination through the cerebrospinal fluid are poorly studied, and medulloblastoma metastases have been assumed to be biologically similar to the primary tumour. Here we show that in both mouse and human medulloblastoma, the metastases from an individual are extremely similar to each other but are divergent from the matched primary tumour. Clonal genetic events in the metastases can be demonstrated in a restricted subclone of the primary tumour, suggesting that only rare cells within the primary tumour have the ability to metastasize. Failure to account for the bicompartmental nature of metastatic medulloblastoma could be a major barrier to the development of effective targeted therapies.