Adult medulloblastoma comprises three major molecular variants

Long-term outcomes of adult medulloblastoma patients treated with radiotherapy

Medulloblastoma (MB) is rare in adults and treatment guidelines are consequently not well-established. Few modern series have reported long-term follow-up and treatment sequelae. We examined long-term outcomes of adult MB patients at one institution. Records of 29 consecutive patients (18 male, 11 female) aged ≥ 18 years who received radiotherapy (RT) for primary MB from 1990 to 2016 were reviewed. Median age at diagnosis was 28 years (range 18-72 years). Seventeen patients were standard risk and 12 were high risk. Nineteen patients had gross total resection, seven had subtotal resection, and three had biopsy only. Median craniospinal irradiation and boost doses were 36 Gy (range 23.4-39.6 Gy) and 55.8 Gy (range 54-59.4 Gy), respectively. Of 24 patients receiving chemotherapy, 20 received concurrent + adjuvant and 4 received adjuvant only. At median follow-up of 9.0 years (range 1.1-20.5 years), five patients recurred: four in the posterior fossa and one in both the posterior fossa and above the tentorium. Five patients died: two of disease progression and three after possible treatment complications (seizure, lobar pneumonia, and multifactorial sepsis). At last follow-up, 23 patients were alive with no evidence of disease. Long-term effects include executive dysfunction (n = 17), weakness/ataxia (n = 16), and depression/anxiety (n = 13). Kaplan-Meier estimates of 10-year overall survival and failure-free survival are 83% (95% confidence interval [CI] 59-93%) and 79% (CI 55-91%), respectively. Despite encouraging disease control in this cohort, long-term sequelae may limit quality of life. Multimodality pediatric regimens using lower RT doses may be considered to reduce treatment-related morbidity.

Imaging Biomarkers for Adult Medulloblastomas: Genetic Entities May Be Identified by Their MR Imaging Radiophenotype

BACKGROUND AND PURPOSE

The occurrence of medulloblastomas in adults is rare; nevertheless, these tumors can be subdivided into genetic and histologic entities each having distinct prognoses. This study aimed to identify MR imaging biomarkers to classify these entities and to uncover differences in MR imaging biomarkers identified in pediatric medulloblastomas.

MATERIALS AND METHODS

Eligible preoperative MRIs from 28 patients (11 women; 22-53 years of age) of the Multicenter Pilot-study for the Therapy of Medulloblastoma of Adults (NOA-7) cohort were assessed by 3 experienced neuroradiologists. Lesions and perifocal edema were volumetrized and multiparametrically evaluated for classic morphologic characteristics, location, hydrocephalus, and Chang criteria. To identify MR imaging biomarkers, we correlated genetic entities sonic hedgehog (SHH) TP53 wild type, wingless (WNT), and non-WNT/non-SHH medulloblastomas (in adults, Group 4), and histologic entities were correlated with the imaging criteria. These MR imaging biomarkers were compared with corresponding data from a pediatric study.

RESULTS

There were 19 SHH TP53 wild type (69%), 4 WNT-activated (14%), and 5 Group 4 (17%) medulloblastomas. Six potential MR imaging biomarkers were identified, 3 of which, hydrocephalus (P = .03), intraventricular macrometastases (P = .02), and hemorrhage (P = .04), when combined, could identify WNT medulloblastoma with 100% sensitivity and 88.3% specificity (95% CI, 39.8%-100.0% and 62.6%-95.3%). WNT-activated nuclear β-catenin accumulating medulloblastomas were smaller than the other entities (95% CI, 5.2-22.3 cm³ versus 35.1-47.6 cm³; P = .03). Hemorrhage was exclusively present in non-WNT/non-SHH medulloblastomas (P = .04; n = 2/5). MR imaging biomarkers were all discordant from those identified in the pediatric cohort. Desmoplastic/nodular medulloblastomas were more rarely in contact with the fourth ventricle (4/15 versus 7/13; P = .04).

CONCLUSIONS

MR imaging biomarkers can help distinguish histologic and genetic medulloblastoma entities in adults and appear to be different from those identified in children.

Distinctive localization and MRI features correlate of molecular subgroups in adult medulloblastoma

Medulloblastoma (MB) is recognized as comprising four molecular subgroups with distinct transcriptional profiles, clinical features, and outcomes. Previous studies demonstrate that pediatric MBs present with subgroup-specific MRI manifestations. We hypothesized that combination of anatomical localization and conventional features based on MR imaging can predict these subgroups in adult MBs. MR Imaging manifestations of 125 adult patients with MB were analyzed retrospectively based on pre-operative MRI scans. MB molecular subgroups were evaluated by the expression profiling array and immunohistochemistry. A pediatric MB cohort of 60 patients were analyzed for comparison with data of adult patients. Multiple logistic regression analysis revealed that tumor location (P < 0.0001) and pattern of enhancement (P = 0.0048) were significantly correlated with molecular subgroups in adult MBs. Ninety-two percent of adult MBs were correctly predicted by using logistic regression model based on the anatomical localization patterns and pattern of enhancement. Exclusively intra-cerebellar growth, localization in the rostral cerebellum, and no brainstem contact were specific to adult SHH-MBs. Group 4-MBs in adult were characterized by minimal/no enhancement compared with other two subgroups. Infant SHH-MBs represented significant different localization patterns compared with SHH tumors in children and adults. We identified that molecular subgroups of adult MBs could be well predicted by tumor localization patterns and enhancement pattern. Our study also provided important evidence that MB subgroups in adult possibly derived from different cellular origins.

Medulloblastoma: From Myth to Molecular

Current therapies for medulloblastoma were introduced primarily in the 1980s and consist of predominantly cytotoxic, nontargeted approaches. Mortality from medulloblastoma remains significant. In addition, many survivors suffer from severe treatment-related effects of radiation and cytotoxic chemotherapy. Further intensification of nonspecific therapy is unlikely to offer additional benefits, because survival rates have reached a plateau. Recent publications in medulloblastoma have revolved largely around the recognition that medulloblastoma per se does not exist, but rather, that there are a group of histologically similar but clinically and molecularly distinct entities that have been grouped under that rubric. Distinguishing the four molecular subgroups of medulloblastoma-wingless (WNT), sonic hedgehog (SHH), group 3, and group 4-in the daily treatment of patients, as well in the setting of clinical trials, is an important challenge in the near term for the pediatric neuro-oncology community. The preponderance of morbidity in treating patients with medulloblastoma is secondary to the treatment or prophylaxis of leptomeningeal metastases, and the cause of most deaths is leptomeningeal metastases. Recurrence of medulloblastoma is a nearly universally fatal event, with no significant salvage rate. The extent of spatial and temporal intratumoral heterogeneity as medulloblastoma metastasizes to leptomeninges and as it evolves in the face of radiation and cytotoxic chemotherapy is just beginning to be understood as a major barrier to therapeutic success. Pediatric neuro-oncology clinicians and scientists must now determine how best to incorporate rapid changes in our biologic understanding of medulloblastoma into the next generation of upfront clinical trials, with the goal of both improving survival for the highest-risk patients and improving quality of life for survivors.

Intertumoral Heterogeneity within Medulloblastoma Subgroups

While molecular subgrouping has revolutionized medulloblastoma classification, the extent of heterogeneity within subgroups is unknown. Similarity network fusion (SNF) applied to genome-wide DNA methylation and gene expression data across 763 primary samples identifies very homogeneous clusters of patients, supporting the presence of medulloblastoma subtypes. After integration of somatic copy-number alterations, and clinical features specific to each cluster, we identify 12 different subtypes of medulloblastoma. Integrative analysis using SNF further delineates group 3 from group 4 medulloblastoma, which is not as readily apparent through analyses of individual data types. Two clear subtypes of infants with Sonic Hedgehog medulloblastoma with disparate outcomes and biology are identified. Medulloblastoma subtypes identified through integrative clustering have important implications for stratification of future clinical trials.

Molecular mechanisms and therapeutic targets in pediatric brain tumors

Brain tumors are among the leading causes of cancer-related deaths in children. Although surgery, aggressive radiation, and chemotherapy have improved outcomes, many patients still die of their disease. Moreover, those who survive often suffer devastating long-term side effects from the therapies. A greater understanding of the molecular underpinnings of these diseases will drive the development of new therapeutic approaches. Advances in genomics and epigenomics have provided unprecedented insight into the molecular diversity of these diseases and, in several cases, have revealed key genes and signaling pathways that drive tumor growth. These not only serve as potential therapeutic targets but also have facilitated the creation of animal models that faithfully recapitulate the human disease for preclinical studies. In this Review, we discuss recent progress in understanding the molecular basis of the three most common malignant pediatric brain tumors-medulloblastoma, ependymoma, and high-grade glioma-and the implications for development of safer and more effective therapies.

Update on the integrated histopathological and genetic classification of medulloblastoma - a practical diagnostic guideline

The revised WHO classification of tumors of the CNS 2016 has introduced the concept of the integrated diagnosis. The definition of medulloblastoma entities now requires a combination of the traditional histological information with additional molecular/genetic features. For definition of the histopathological component of the medulloblastoma diagnosis, the tumors should be assigned to one of the four entities classic, desmoplastic/nodular (DNMB), extensive nodular (MBEN), or large cell/anaplastic (LC/A) medulloblastoma. The genetically defined component comprises the four entities WNT-activated, SHH-activated and TP53 wildtype, SHH-activated and TP53 mutant, or non-WNT/non-SHH medulloblastoma. Robust and validated methods are available to allow a precise diagnosis of these medulloblastoma entities according to the updated WHO classification, and for differential diagnostic purposes. A combination of immunohistochemical markers including β-catenin, Yap1, p75-NGFR, Otx2, and p53, in combination with targeted sequencing and copy number assessment such as FISH analysis for MYC genes allows a precise assignment of patients for risk-adapted stratification. It also allows comparison to results of study cohorts in the past and provides a robust basis for further treatment refinement.

Cell Signaling Pathways in Brain Tumors

Primary brain tumors, particularly glioblastoma, are associated with significant morbidity and are often recalcitrant to standard therapies. In recent years, brain tumors have been the focus of large-scale genomic sequencing efforts, providing unprecedented insight into the genomic aberrations and cellular signaling mechanisms that drive these cancers. Discoveries from these efforts have translated into novel diagnostic algorithms, biomarkers, and therapeutic strategies in Neuro-Oncology. However, the cellular mechanisms that drive brain tumors are heterogeneous and complex: applying this new knowledge to improve patient outcomes remains a challenge. Efforts to characterize and target these molecular vulnerabilities are evolving.

Complete and sustained response of adult medulloblastoma to first-line sonic hedgehog inhibition with vismodegib

Medulloblastoma is an aggressive primitive neuroectodermal tumor of the cerebellum that is rare in adults. Medulloblastomas fall into 4 prognostically significant molecular subgroups that are best defined by experimental gene expression profiles: the WNT pathway, sonic hedgehog (SHH) pathway, and subgroups 3 and 4 (non-SHH/WNT). Medulloblastoma of adults belong primarily to the SHH category. Vismodegib, an SHH-pathway inhibitor FDA-approved in 2012 for treatment of basal cell carcinoma, has been used successfully in the setting of chemorefractory medulloblastoma, but not as a first-line therapy. In this report, we describe a sustained response of an unresectable multifocal form of adult medulloblastoma to vismodegib. Molecular analysis in this case revealed mutations in TP53 and a cytogenetic abnormality, i17q, that is prevalent and most often associated with subgroup 4 rather than the SHH-activated form of medulloblastoma. Our findings indicate that vismodegib may also block alternate, non-canonical forms of downstream SHH pathway activation. These findings provide strong impetus for further investigation of vismodegib in clinical trials in the first-line setting for pediatric and adult forms of medulloblastoma.

Clinicopathological characteristics, molecular subgrouping, and expression of miR-379/miR-656 cluster (C14MC) in adult medulloblastomas

Medulloblastoma (MB) is a childhood tumor comprising four molecular subgroups: WNT, SHH, group 3 and group 4, with diagnostic and prognostic connotations. Very few studies are available on molecular subgrouping of adult MBs due to their rarity. Recently, loss of chromosome14q has been reported in SHH MBs, with downregulation of miR-379/miR-656 cluster (C14MC) in pediatric SHH MBs. Hence, the present study on adult MBs was undertaken to enumerate clinicopathological characteristics and molecular subgroups, and to analyze expression of C14MC and its transcriptional regulators, MEF2, JUN and ESRRG. Immunohistochemistry for β-catenin, GAB1 and YAP1 was performed to identify molecular subgroups. MYC amplification was evaluated by FISH. Expression profiling of 47 miRNAs from C14MC was performed using customized Taqman low-density array. Expression of transcriptional regulators was examined using RT-PCR. Seventy-one adult MBs were analyzed. They had male predominance and majority were located laterally (52 %). A significant proportion of cases were of Desmoplastic/nodular histology (32 %); MBEN was not seen. WNT tumors constituted 4.2 %, SHH 62 %, and non-WNT/non-SHH 33.8 %. MYC amplification was identified in 11.1 % cases. Patient outcome was worse in adults. Significant downregulation of C14MC was observed in all MB subgroups, and MEF-2 expression was downregulated. Adult MBs are distinct from childhood MBs in terms of location, histopathological subtypes, molecular subgroups, as well as prognosis. Silencing of C14MC in all MB subgroups suggests its role as a tumor suppressor locus in tumorigenesis. Deregulation of C14MC can possibly be attributed to repression of MEF2.

Adult medulloblastoma: A rare case report and literature review

Background:

Medulloblastoma is a highly malignant embryonal tumor which commonly arises in the cerebellum. It is relatively rare and accounts for less than 2% of all primary brain tumors. The tumor primarily occurs in childhood; however, rarely, it may be found in adult population. In addition, medulloblastoma in adult population shows features which are quite distinct from the pediatric group.

Case Description:

We report the case of a 33-year-old man who presented to our institution with a history of blurred vision of both eyes for 5 months preceded by intermittent headache since the previous year. Preoperative investigation suggested a posterior fossa mass and we suspected an ependymoma. The patient underwent ventriculoperitoneal shunt and craniotomy tumor removal, followed by radiotherapy. Histopathological and immunohistochemical examination were performed, and the results showed a diagnosis of medulloblastoma.

Conclusion:

This case is exceptional because adult medulloblastoma occurrence in our center is extremely rare, and the diagnosis can only be established through histopathological and immunohistochemical studies.

The Neuroradiological Spectra of Adult and Pediatric Medulloblastoma Differ : Results from a Literature-based Meta-analysis

PURPOSE

Current knowledge on the spectrum of the neuroradiological appearance of adult medulloblastoma is sparse. Due to the rarity of the disease, adult patients were generally diagnosed and treated similar to children; however, pediatric and adult medulloblastomas display substantial molecular differences that may influence the neuroradiological phenotype. This study therefore aimed at assessment of the neuroradiological spectrum of adult medulloblastoma in comparison to pediatric tumors.

METHODS

All available publications on adult medulloblastoma published until June 2013 were screened for imaging data on single patients. A total of 109 patients were identified and compared to 118 pediatric patients described in 4 cohorts.

RESULTS

The average age of the adult patients was 34.3 years. Most adult medulloblastomas (57.6 %) were localized laterally (vs. 14.4 % in pediatric patients). On T1-weighted sequences, only 41.1 % of all adult medulloblastomas appeared hypointense (vs. 89.3 %) and 69.6 % were hyperintense on T2 sequences (vs. 83 %). In contrast to pediatric patients only 53.3 % showed strong contrast enhancement (pediatric patients 77.1 %), while the contrast uptake of the remainder was described as subtle, moderate or lacking. Contrast enhancement was more often described as inhomogeneous in adults (35.5 % as compared to 15.2 % in children) and 26.4 % had cysts.

CONCLUSION

Although the neuroradiological spectrum of medulloblastoma in adults was similar to children, an atypical presentation with inhomogeneous contrast enhancement, more hyperintense signal on T1 and a more hypointense signal on T2-weighted sequences was common. Given the rarity of the tumor, awareness of these differences constitutes a prerequisite to avoid delays in diagnostics.

Risk stratification of childhood medulloblastoma in the molecular era: the current consensus

Historical risk stratification criteria for medulloblastoma rely primarily on clinicopathological variables pertaining to age, presence of metastases, extent of resection, histological subtypes and in some instances individual genetic aberrations such as MYC and MYCN amplification. In 2010, an international panel of experts established consensus defining four main subgroups of medulloblastoma (WNT, SHH, Group 3 and Group 4) delineated by transcriptional profiling. This has led to the current generation of biomarker-driven clinical trials assigning WNT tumors to a favorable prognosis group in addition to clinicopathological criteria including MYC and MYCN gene amplifications. However, outcome prediction of non-WNT subgroups is a challenge due to inconsistent survival reports. In 2015, a consensus conference was convened in Heidelberg with the objective to further refine the risk stratification in the context of subgroups and agree on a definition of risk groups of non-infant, childhood medulloblastoma (ages 3-17). Published and unpublished data over the past 5 years were reviewed, and a consensus was reached regarding the level of evidence for currently available biomarkers. The following risk groups were defined based on current survival rates: low risk (>90 % survival), average (standard) risk (75-90 % survival), high risk (50-75 % survival) and very high risk (<50 % survival) disease. The WNT subgroup and non-metastatic Group 4 tumors with whole chromosome 11 loss or whole chromosome 17 gain were recognized as low-risk tumors that may qualify for reduced therapy. High-risk strata were defined as patients with metastatic SHH or Group 4 tumors, or MYCN-amplified SHH medulloblastomas. Very high-risk patients are Group 3 with metastases or SHH with TP53 mutation. In addition, a number of consensus points were reached that should be standardized across future clinical trials. Although we anticipate new data will emerge from currently ongoing and recently completed clinical trials, this consensus can serve as an outline for prioritization of certain molecular subsets of tumors to define and validate risk groups as a basis for future clinical trials.

Molecular Classification of Medulloblastoma

Medulloblastoma (MB) is one of the most frequent malignant brain tumors in children. The current standard treatment regimen consists of surgical resection, craniospinal irradiation, and adjuvant chemotherapy. Although these treatments have the potential to increase the survival of 70–80% of patients with MB, they are also associated with serious treatment-induced morbidity. The current risk stratification of MB is based on clinical factors, including age at presentation, metastatic status, and the presence of residual tumor following resection. In addition, recent genomic studies indicate that MB consists of at least four distinct molecular subgroups: WNT, sonic hedgehog (SHH), Group 3, and Group 4. WNT and SHH MBs are characterized by aberrations in the WNT and SHH signaling pathways, respectively. WNT MB has the best prognosis compared to the other MBs, while SHH MB has an intermediate prognosis. The underlying signaling pathways associated with Group 3 and 4 MBs have not been identified. Group 3 MB is frequently associated with metastasis, resulting in a poor prognosis, while Group 4 is sometimes associated with metastasis and has an intermediate prognosis. Group 4 is the most frequent MB and represents 35% of all MBs. These findings suggest that MB is a heterogeneous disease, and that MB subgroups have distinct molecular, demographic, and clinical characteristics. The molecular classification of MBs is redefining the risk stratification of patients with MB, and has the potential to identify new therapeutic strategies for the treatment of MB.

Molecular subgroups of adult medulloblastoma: a long-term single-institution study

BACKGROUND

Recent transcriptomic approaches have demonstrated that there are at least 4 distinct subgroups in medulloblastoma (MB); however, survival studies of molecular subgroups in adult MB have been inconclusive because of small sample sizes. The aim of this study is to investigate the molecular subgroups in adult MB and identify their clinical and prognostic implications in a large, single-institution cohort.

METHODS

We determined gene expression profiles for 13 primary adult MBs. Bioinformatics tools were used to establish distinct molecular subgroups based on the most informative genes in the dataset. Immunohistochemistry with subgroup-specific antibodies was then used for validation within an independent cohort of 201 formalin-fixed MB tumors, in conjunction with a systematic analysis of clinical and histological characteristics.

RESULTS

Three distinct molecular variants of adult MB were identified: the SHH, WNT, and group 4 subgroups. Validation of these subgroups in the 201-tumor cohort by immunohistochemistry identified significant differences in subgroup-specific demographics, histology, and metastatic status. The SHH subgroup accounted for the majority of the tumors (62%), followed by the group 4 subgroup (28%) and the WNT subgroup (10%). Group 4 tumors had significantly worse progression-free and overall survival compared with tumors of the other molecular subtypes.

CONCLUSIONS

We have identified 3 subgroups of adult MB, characterized by distinct expression profiles, clinical features, pathological features, and prognosis. Clinical variables incorporated with molecular subgroup are more significantly informative for predicting adult patient outcome.

Outcomes of adult medulloblastoma treated with a multimodality approach: A tertiary cancer center experience

OBJECTIVES

Adult medulloblastoma (AMB) is a rare central nervous system tumor. We aimed to analyze the treatment outcomes of AMB treated at our institute with surgery followed by craniospinal irradiation (CSI) and adjuvant chemotherapy.

METHODS

We retrospectively evaluated the treatment charts of 31 patients of AMB treated from 2003-2011. The patient demography, treatment details and survival data were collected in a predesigned proforma. Kaplan Meier method was used to analyze disease free survival (DFS) and the impact of prognostic factors was determined by univariate analysis (log rank test).

RESULTS

Male: Female ratio was 21:10. Cerebrospinal fluid dissemination was noted in 16% cases. CSI (36 Gray at 1.8 Gray/fraction to entire neuraxis and 20 Gray at 2 Gray/fraction boost to posterior fossa) was used in all cases. 26 patients received adjuvant chemotherapy (carboplatin plus etoposide). Median follows up was 26.85 months (9.47-119.73 months). The estimated 3 and 5 years DFS was found to be 84.9% and 50.7% respectively. On univariate analysis, tumor located laterally had a trend towards better DFS (HR 3.04; 95%CI 0.722 to 12.812; P = 0.07) compared to midline tumors. Other factors like adjuvant chemotherapy, age, gender, surgical extent had no statistically significant impact on survival.

CONCLUSION

The results of our study (largest series from India) show that the regimen of surgery, adjuvant CSI and chemotherapy is feasible and confers descent survival. AMB patients should be treated with a multimodality approach in a tertiary care centre.

PI-3K Inhibitors Preferentially Target CD15+ Cancer Stem Cell Population in SHH Driven Medulloblastoma

Sonic hedgehog (SHH) medulloblastoma (MB) subtype is driven by a proliferative CD15+ tumor propagating cell (TPC), also considered in the literature as a putative cancer stem cell (CSC). Despite considerable research, much of the biology of this TPC remains unknown. We report evidence that phosphatase and tensin homolog (PTEN) and phosphoinositide 3-kinase (PI-3K) play a crucial role in the propagation, survival and potential response to therapy in this CD15+ CSC/TPC-driven malignant disease. Using the ND2-SmoA1 transgenic mouse model for MB, mouse genetics and patient-derived xenografts (PDXs), we demonstrate that the CD15+TPCs are 1) obligately required for SmoA1Tg-driven tumorigenicity 2) regulated by PTEN and PI-3K signaling 3) selectively sensitive to the cytotoxic effects of pan PI-3K inhibitors in vitro and in vivo but resistant to chemotherapy 4) in the SmoA1Tg mouse model are genomically similar to the SHH human MB subgroup. The results provide the first evidence that PTEN plays a role in MB TPC signaling and biology and that PI-3K inhibitors target and suppress the survival and proliferation of cells within the mouse and human CD15+ cancer stem cell compartment. In contrast, CD15+ TPCs are resistant to cisplatinum, temozolomide and the SHH inhibitor, NVP-LDE-225, agents currently used in treatment of medulloblastoma. These studies validate the therapeutic efficacy of pan PI-3K inhibitors in the treatment of CD15+ TPC dependent medulloblastoma and suggest a sequential combination of PI-3K inhibitors and chemotherapy will have augmented efficacy in the treatment of this disease.

MB3W1 is an orthotopic xenograft model for anaplastic medulloblastoma displaying cancer stem cell- and Group 3-properties

Background

Medulloblastoma is the most common malignant brain tumor in children and can be divided in different molecular subgroups. Patients whose tumor is classified as a Group 3 tumor have a dismal prognosis. However only very few tumor models are available for this subgroup.

Methods

We established a robust orthotopic xenograft model with a cell line derived from the malignant pleural effusions of a child suffering from a Group 3 medulloblastoma.

Results

Besides classical characteristics of this tumor subgroup, the cells display cancer stem cell characteristics including neurosphere formation, multilineage differentiation, CD133/CD15 expression, high ALDH-activity and high tumorigenicity in immunocompromised mice with xenografts exactly recapitulating the original tumor architecture.

Conclusions

This model using unmanipulated, human medulloblastoma cells will enable translational research, specifically focused on Group 3 medulloblastoma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2170-z) contains supplementary material, which is available to authorized users.

Posterior Fossa Intra-Axial Tumors in Adults

BACKGROUND

The posterior fossa is the site of many types of tumors, and brain metastases are the most common malignancies in that location among adults. Other brain tumors, such as ependymomas, medulloblastomas, and juvenile pilocytic astrocytomas, mostly occur during childhood and are relatively rare in adults. Most primary malignant brain tumors, such as gliomas and lymphomas, tend to be located in the supratentorial compartment.

METHODS

This review summarizes prognostic factors, therapeutic management, and molecular data of intra-axial posterior fossa tumors in adults, including ependymomas, medulloblastomas, and pilocytic astrocytomas.

RESULTS

The literature on intra-axial posterior fossa tumors in adults relies mainly on limited retrospective clinical studies, and such studies employ a wide range of treatment approaches that are usually based on therapies developed specifically for children or for supratentorial brain tumors.

CONCLUSIONS

The clinical course and surgical outcome of adult patients with intra-axial brain tumors in the posterior fossa are summarized in this review. The prognostic factors and therapeutic management of patients with these tumors are controversial because of their rarity, their heterogeneity, and the lack of sufficient data in the literature.

p53 and Meduloblastoma

Our understanding of medulloblastoma biology has increased dramatically over the past decade, in part a result of the recognition that there exists tremendous intertumoral heterogeneity not apparent by morphology alone. A particular area that significantly changed our approach to medulloblastoma has been an increased understanding of the role of p53. A role for p53 in medulloblastoma has been established over the past 20 years, however, not until recently has its significance been identified. Recent developments in the understanding of intertumor heterogeneity has clarified the role of TP53 mutations, as the importance of TP53 mutations is highly dependent on the molecular subgroup of medulloblastoma, with TP53 mutant Sonic Hedgehog medulloblastomas forming an extremely high-risk group of patients. As such, there is now a tremendous push to understand the role that p53 plays in treatment resistance of medulloblastoma. In this review, we will summarize the current understanding of p53 in medulloblastoma drawn primarily from recent advances in integrated genomics.

Shedding light on adult medulloblastoma: current management and opportunities for advances

Few evidence-based guidelines are available for the treatment of adult medulloblastoma, an extremely rare disease. Therapeutic regimens, typically modeled following pediatric protocols, consist of surgical resection followed by radiotherapy with or without adjuvant chemotherapy. Because of the rarity of this disease in adults, any treatment undertaken is based mainly on small and retrospective studies. Unlike pediatric patients, adults with medulloblastoma have been treated according to risk-adapted therapeutic strategies in only a few prospective studies. Overall, approximately 30% of patients experience recurrence and die of disease-related causes. Although the patients could respond to second-line treatments, the prognosis of patients with recurrence remains dismal. An important challenge for the future will be the biologic characterization of medulloblastoma in adults, with the identification of specific genetic patterns of patients with different prognosis and different response to targeted treatments.

A microRNA-1280/JAG2 network comprises a novel biological target in high-risk medulloblastoma

Over-expression of PDGF receptors (PDGFRs) has been previously implicated in high-risk medulloblastoma (MB) pathogenesis. However, the exact biological functions of PDGFRα and PDGFRβ signaling in MB biology remain poorly understood. Here, we report the subgroup specific expression of PDGFRα and PDGFRβ and their associated biological pathways in MB tumors. c-MYC, a downstream target of PDGFRβ but not PDGFRα, is involved in PDGFRβ signaling associated with cell proliferation, cell death, and invasion. Concurrent inhibition of PDGFRβ and c-MYC blocks MB cell proliferation and migration synergistically. Integrated analysis of miRNA and miRNA targets regulated by both PDGFRβ and c-MYC reveals that increased expression of JAG2, a target of miR-1280, is associated with high metastatic dissemination at diagnosis and a poor outcome in MB patients. Our study may resolve the controversy on the role of PDGFRs in MB and unveils JAG2 as a key downstream effector of a PDGFRβ-driven signaling cascade and a potential therapeutic target.

Biomarker-driven stratification of disease-risk in non-metastatic medulloblastoma: Results from the multi-center HIT-SIOP-PNET4 clinical trial

PURPOSE

To improve stratification of risk-adapted treatment for non-metastatic (M0), standard-risk medulloblastoma patients by prospective evaluation of biomarkers of reported biological or prognostic significance, alongside clinico-pathological variables, within the multi-center HIT-SIOP-PNET4 trial.

METHODS

Formalin-fixed paraffin-embedded tumor tissues were collected from 338 M0 patients (>4.0 years at diagnosis) for pathology review and assessment of the WNT subgroup (MBWNT) and genomic copy-number defects (chromosome 17, MYC/MYCN, 9q22 (PTCH1) and DNA ploidy). Clinical characteristics were reviewed centrally.

RESULTS

The favorable prognosis of MBWNT was confirmed, however better outcomes were observed for non-MBWNT tumors in this clinical risk-defined cohort compared to previous disease-wide clinical trials. Chromosome 17p/q defects were heterogeneous when assessed at the cellular copy-number level, and predicted poor prognosis when they occurred against a diploid (ch17(im)/diploid(cen)), but not polyploid, genetic background. These factors, together with post-surgical tumor residuum (R+) and radiotherapy delay, were supported as independent prognostic markers in multivariate testing. Notably, MYC and MYCN amplification were not associated with adverse outcome. In cross-validated survival models derived for the clinical standard-risk (M0/R0) disease group, (ch17(im)/diploid(cen); 14% of patients) predicted high disease-risk, while the outcomes of patients without (ch17(im)/diploid(cen)) did not differ significantly from MBWNT, allowing re-classification of 86% as favorable-risk.

CONCLUSIONS

Biomarkers, established previously in disease-wide studies, behave differently in clinically-defined standard-risk disease. Distinct biomarkers are required to assess disease-risk in this group, and define improved risk-stratification models. Routine testing for specific patterns of chromosome 17 imbalance at the cellular level, and MBWNT, provides a strong basis for incorporation into future trials.

Integrating Molecular Subclassification of Medulloblastomas into Routine Clinical Practice: A Simplified Approach

Medulloblastoma (MB) is composed of four molecular subgroups viz. WNT, SHH, groups 3 and 4, identified using various high-throughput methods. Translation of this molecular data into pathologist-friendly techniques that would be applicable in laboratories all over the world is a major challenge. Ninety-two MBs were analyzed using a panel of 10 IHC markers, real-time PCR for mRNA and miRNA expression, and FISH for MYC amplification. β-catenin, GAB1 and YAP1 were the only IHC markers of utility in classification of MBs into three subgroups viz. WNT (9.8%), SHH (45.6%) and non-WNT/SHH (44.6%). mRNA expression could further classify some non-WNT/SHH tumors into groups 3 and 4. This, however, was dependent on integrity of RNA extracted from FFPE tissue. MYC amplification was seen in 20% of non-WNT/SHH cases and was associated with the worst prognosis. For routine diagnostic practice, we recommend classification of MBs into three subgroups: WNT, SHH and non-WNT/SHH, with supplementation by prognostic markers like MYC for non-WNT/SHH tumors. Using this panel, we propose a new three-tier risk stratification system for MBs. Molecular subgrouping with this limited panel is rapid, economical, works well on FFPE tissue and is reliable as it correlates significantly with clinicopathological parameters and patient survival.

New perspectives in the treatment of adult medulloblastoma in the era of molecular oncology

Medulloblastoma is the most common central nervous system tumor in children, while it is extremely rare in adults. Multimodal treatment involving surgery, radiotherapy and chemotherapy can improve the prognosis of this disease, and recent advances in molecular biology have allowed the identification of molecular subgroups (WNT, SHH, Groups 3 and 4), each of which have different cytogenetic, mutational and gene expression signatures, demographics, histology and prognosis. The present review focuses on the state of the art for adult medulloblastoma treatment and on novel molecular advances and their future implications in the treatment of this disease.

Medulloblastoma: toward biologically based management

Medulloblastoma is the most common malignant brain tumor in children and, as such, has been the focus of tremendous efforts to genomically characterize it. What was once thought to be a single disease has been divided into multiple, molecularly unique subgroups through gene expression profiling. Each subgroup is not only unique in its origin and pathogenesis but also in the prognosis and potential therapeutic options. Targeted therapy of malignancies has long been the goal of clinical oncology. The progress made in the classification of medulloblastoma should be used as a model for future studies. With the evolution of epigenetic and genomic sequencing, especially when used in tandem with high-throughput pharmacologic screening protocols, the potential for subgroup-specific targeting is closer than ever. This review focuses on the development of the molecular classification system and its potential use in developing prognostic models as well as for the advancement of targeted therapeutic interventions.

Medulloblastoma subgroups remain stable across primary and metastatic compartments

Medulloblastoma comprises four distinct molecular variants with distinct genetics, transcriptomes, and outcomes. Subgroup affiliation has been previously shown to remain stable at the time of recurrence, which likely reflects their distinct cells of origin. However, a therapeutically relevant question that remains unanswered is subgroup stability in the metastatic compartment. We assembled a cohort of 12-paired primary-metastatic tumors collected in the MAGIC consortium, and established their molecular subgroup affiliation by performing integrative gene expression and DNA methylation analysis. Frozen tissues were collected and profiled using Affymetrix gene expression arrays and Illumina methylation arrays. Class prediction and hierarchical clustering were performed using existing published datasets. Our molecular analysis, using consensus integrative genomic data, establishes the unequivocal maintenance of molecular subgroup affiliation in metastatic medulloblastoma. We further validated these findings by interrogating a non-overlapping cohort of 19 pairs of primary-metastatic tumors from the Burdenko Neurosurgical Institute using an orthogonal technique of immunohistochemical staining. This investigation represents the largest reported primary-metastatic paired cohort profiled to date and provides a unique opportunity to evaluate subgroup-specific molecular aberrations within the metastatic compartment. Our findings further support the hypothesis that medulloblastoma subgroups arise from distinct cells of origin, which are carried forward from ontogeny to oncology.

Medulloblastoma subgroup-specific outcomes in irradiated children: who are the true high-risk patients?

BACKGROUND

The advent of integrated genomics has fundamentally changed our understanding of medulloblastoma. Although survival differences exist among the 4 principal subgroups, this has yet to be elucidated in a North American cohort of irradiated patients.

METHODS

Ninety-two consecutive patients between the ages of 3 and 17 treated with surgery, craniospinal irradiation, and chemotherapy were identified at the Hospital for Sick Children. Molecular subgrouping was performed using nanoString.

RESULTS

Two treatment periods were identified: prior to 2006 as per the protocols of the Children's Oncology Group, and after 2006 per the St Jude Medulloblastoma 03 protocol. Five-year progression-free survival (PFS) over the entire cohort was 0.801 (95% CI: 0.692-0.875) with no significant difference between treatment protocols. Strikingly, we found that Group 4 patients had excellent 5-year PFS of 0.959 (95% CI: 0.744-0.994) for average risk and 0.887 (95% CI: 0.727-0.956) across all Group 4 patients. Group 3 patients had 5-year PFS of 0.733 (95% CI: 0.436-0.891). Sonic hedgehog patients did poorly across both treatment protocols, with 5-year PFS of 0.613 (95% CI: 0.333-0.804), likely owing to a high proportion of TP53 mutated patients in this age group.

CONCLUSIONS

In a cohort of irradiated patients over 3 years of age, PFS for Group 4 patients was significantly improved compared with initial reports. The impact of subgroup affiliation in these children needs to be assessed in large prospectively treated cooperative protocols to determine if more than just WNT patients can be safely selected for de-escalation of therapy.

Deregulated proliferation and differentiation in brain tumors

Neurogenesis, the generation of new neurons, is deregulated in neural stem cell (NSC)- and progenitor-derived murine models of malignant medulloblastoma and glioma, the most common brain tumors of children and adults, respectively. Molecular characterization of human malignant brain tumors, and in particular brain tumor stem cells (BTSCs), has identified neurodevelopmental transcription factors, microRNAs, and epigenetic factors known to inhibit neuronal and glial differentiation. We are starting to understand how these factors are regulated by the major oncogenic drivers in malignant brain tumors. In this review, we will focus on the molecular switches that block normal neuronal differentiation and induce brain tumor formation. Genetic or pharmacological manipulation of these switches in BTSCs has been shown to restore the ability of tumor cells to differentiate. We will discuss potential brain tumor therapies that will promote differentiation in order to reduce treatment resistance, suppress tumor growth, and prevent recurrence in patients.

Foretinib is effective therapy for metastatic sonic hedgehog medulloblastoma

Medulloblastoma is the most common malignant pediatric brain tumor, with metastases present at diagnosis conferring a poor prognosis. Mechanisms of dissemination are poorly understood and metastatic lesions are genetically divergent from the matched primary tumor. Effective and less toxic therapies that target both compartments have yet to be identified. Here, we report that the analysis of several large nonoverlapping cohorts of patients with medulloblastoma reveals MET kinase as a marker of sonic hedgehog (SHH)-driven medulloblastoma. Immunohistochemical analysis of phosphorylated, active MET kinase in an independent patient cohort confirmed its correlation with increased tumor relapse and poor survival, suggesting that patients with SHH medulloblastoma may benefit from MET-targeted therapy. In support of this hypothesis, we found that the approved MET inhibitor foretinib could suppress MET activation, decrease tumor cell proliferation, and induce apoptosis in SHH medulloblastomas in vitro and in vivo. Foretinib penetrated the blood-brain barrier and was effective in both the primary and metastatic tumor compartments. In established mouse xenograft or transgenic models of metastatic SHH medulloblastoma, foretinib administration reduced the growth of the primary tumor, decreased the incidence of metastases, and increased host survival. Taken together, our results provide a strong rationale to clinically evaluate foretinib as an effective therapy for patients with SHH-driven medulloblastoma.

BET bromodomain protein inhibition is a therapeutic option for medulloblastoma

Medulloblastoma is the most common malignant brain tumor of childhood, and represents a significant clinical challenge in pediatric oncology, since overall survival currently remains under 70%. Patients with tumors overexpressing MYC or harboring a MYC oncogene amplification have an extremely poor prognosis. Pharmacologically inhibiting MYC expression may, thus, have clinical utility given its pathogenetic role in medulloblastoma. Recent studies using the selective small molecule BET inhibitor, JQ1, have identified BET bromodomain proteins, especially BRD4, as epigenetic regulatory factors for MYC and its targets. Targeting MYC expression by BET inhibition resulted in antitumoral effects in various cancers. Our aim here was to evaluate the efficacy of JQ1 against preclinical models for high-risk MYC-driven medulloblastoma. Treatment of medulloblastoma cell lines with JQ1 significantly reduced cell proliferation and preferentially induced apoptosis in cells expressing high levels of MYC. JQ1 treatment of medulloblastoma cell lines downregulated MYC expression and resulted in a transcriptional deregulation of MYC targets, and also significantly altered expression of genes involved in cell cycle progression and p53 signalling. JQ1 treatment prolonged the survival of mice harboring medulloblastoma xenografts and reduced the tumor burden in these mice. Our preclinical data provide evidence to pursue testing BET inhibitors, such as JQ1, as molecular targeted therapeutic options for patients with high-risk medulloblastomas overexpressing MYC or harboring MYC amplifications.

The G protein α subunit Gαs is a tumor suppressor in Sonic hedgehog-driven medulloblastoma

Medulloblastoma, the most common malignant childhood brain tumor, exhibits distinct molecular subtypes and cellular origins. Genetic alterations driving medulloblastoma initiation and progression remain poorly understood. Herein, we identify GNAS, encoding the G-protein Gsα, as a potent tumor suppressor gene that defines a subset of aggressive Sonic Hedgehog (Shh)-driven human medulloblastomas. Ablation of the single Gnas gene in anatomically-distinct progenitors is sufficient to induce Shh-associated medulloblastomas, which recapitulate their human counterparts. Gsα is highly enriched at the primary cilium of granule neuron precursors and suppresses Shh-signaling by regulating both the cAMP-dependent pathway and ciliary trafficking of Hedgehog pathway components. Elevation of a Gsα effector, cAMP, effectively inhibits tumor cell proliferation and progression in Gnas mutants. Thus, our gain- and loss-of-function studies identify a previously unrecognized tumor suppressor function for Gsα that acts as a molecular link across Shh-group medulloblastomas of disparate cellular and anatomical origins, illuminating G-protein modulation as a potential therapeutic avenue.

Patterns of care in adult medulloblastoma: results of an international online survey

The literature on medulloblastoma in adults is generally limited to case reports and retrospective series, and there is no accepted standard of care. The Cooperative Trials Group for Neuro-Oncology (COGNO) sought to determine the range and consistency of clinicians' approaches to management as a basis for future trials. We aimed to identify current treatment strategies for adult medulloblastoma through an online survey launched at the 2012 Society of Neuro-Oncology meeting and by email invitation. Clinicians who had treated at least one adult patient with medulloblastoma, primitive neuroectodermal tumor (PNET), or pineoblastoma in the preceding year were asked about their most recent patient and invited to discuss their approach to a typical clinical scenario. Between November 2012 and January 2013, 45 clinicians (11 medical oncologists, 8 radiation oncologists, 5 pediatric oncologists, and 21 others) from Australia (24), United States (3), Europe (4) and other countries (14) completed the survey. Responding clinicians had treated 54 cases in the past 12 months. The most common histological type was medulloblastoma (64%), then PNET (20%). Most patients were male (68%), and had high-risk disease (65%). Complete surgical resection in 56 and 32% had molecular testing. Radiotherapy was predominantly cranio-spinal (92%) and given mostly post-resection (80%). Combination chemotherapy was more common than single-agent chemotherapy. The choice of chemotherapy varied considerably. There is substantial variation in the treatment of adult medulloblastoma, most pronounced in the choice of chemotherapeutic agents, highlighting the need for further collaborative research to guide evidence-based treatment strategies.

Prognostic significance of clinical, histopathological, and molecular characteristics of medulloblastomas in the prospective HIT2000 multicenter clinical trial cohort

This study aimed to prospectively evaluate clinical, histopathological and molecular variables for outcome prediction in medulloblastoma patients. Patients from the HIT2000 cooperative clinical trial were prospectively enrolled based on the availability of sufficient tumor material and complete clinical information. This revealed a cohort of 184 patients (median age 7.6 years), which was randomly split at a 2:1 ratio into a training (n = 127), and a test (n = 57) dataset in order to build and test a risk score for this population. Independent validation was performed in a non-overlapping cohort (n = 83). All samples were subjected to thorough histopathological investigation, CTNNB1 mutation analysis, quantitative PCR, MLPA and FISH analyses for cytogenetic variables, and methylome analysis. By univariable analysis, clinical factors (M-stage), histopathological variables (large cell component, endothelial proliferation, synaptophysin pattern), and molecular features (chromosome 6q status, MYC amplification, subgrouping) were found to be prognostic. Molecular consensus subgrouping (WNT, SHH, Group 3, Group 4) was validated as an independent feature to stratify patients into different risk groups. When comparing methods for the identification of WNT-driven medulloblastoma, this study identified CTNNB1 sequencing and methylation profiling to most reliably identify these patients. After removing patients with particularly favorable (CTNNB1 mutation, extensive nodularity) or unfavorable (MYC amplification) markers, a risk score for the remaining “intermediate molecular risk” population dependent on age, M-stage, pattern of synaptophysin expression, and MYCN copy-number status was identified, with speckled synaptophysin expression indicating worse outcome. Test and independent validation of the score confirmed significant discrimination of patients by risk profile. Methylation subgrouping and CTNNB1 mutation status represent robust tools for the risk stratification of medulloblastoma. A simple clinico-pathological risk score was identified, which was confirmed in a test set and by independent clinical validation.

Duration of the pre-diagnostic interval in medulloblastoma is subgroup dependent

BACKGROUND

Children presenting with medulloblastoma have a wide range of initial presenting symptoms. However, the influence of underlying tumor biology on the initial presentation of medulloblastoma is currently unknown. In light of the recent discovery of distinct medulloblastoma subgroups, we sought to define the initial presentation of childhood medulloblastoma in a subgroup specific manner.

PROCEDURE

We assembled a cohort of 126 medulloblastoma cases at the Hospital for Sick Children between 1994 and 2012 and determined subgroup affiliation using nanoString. Clinical details pertaining to the initial presentation were determined through a retrospective chart review.

RESULTS

The median pre-diagnostic interval across all medulloblastoma cases was 4 weeks (IQR: 4-12 weeks). Strikingly, when the pre-diagnostic interval was then determined in a subgroup specific manner, cases with WNT and Group 4 tumors showed significantly longer median pre-diagnostic intervals of 8 weeks compared to 2 weeks for SHH and 4 weeks for Group 3 (P = 0.0001). Younger age was significantly associated with a prolonged pre-diagnostic interval (P = 0.02 for all). When stratifying by subgroup the association with age was only significant in Group 4 (P = 0.04 for Group 4). Improved survival was significantly associated with a longer pre-diagnostic interval (P = 0.02), however is no longer significant when controlling for subgroup (P = 0.07).

CONCLUSIONS

The duration of the pre-diagnostic interval in childhood medulloblastoma is highly subgroup dependent, further highlighting the clinical heterogeneity and biological relevance of the four principle subgroups of medulloblastoma.

An adult multifocal medulloblastoma with diffuse acute postoperative cerebellar swelling: immunohistochemical and molecular genetics analysis

Medulloblastoma (MB), the most common malignant tumor typically affecting children, occurs only exceptionally in adults. Multifocal presentation of this malignancy in adulthood is even much rarer—only four cases with favorable postoperative course have been reported, so far. The study illustrates a very rare rapid postoperative clinical deterioration due to diffuse cerebellar swelling (DCS) in an adult multifocal MB (MMB). To the best of their knowledge, authors for the first time performed genetic analysis of MMB and demonstrated expression patterns of selected markers that put the patient within the sonic hedgehog (SHH) molecular subgroup and at least partially explain her unsatisfactory clinical course. Herein, authors summarized the relevant literature concerning this issue with the aim to determine features that would facilitate diagnosis and therapy of such a scarce clinical entity.

Neuroradiology and histopathology in two cases of adult medulloblastoma

Medulloblastoma (MB) is the most common central nervous system neoplasm in children and only rarely presents in the adult population. Recent molecular biology findings have characterized MB as a heterogeneous neoplasm distinguished by well-defined tumour subsets each with specific histologic and molecular features. Available immunohistochemical stains can now be used to differentiate the distinct molecular types of MB. This report analyzed the histopathologic and neuroradiologic features of two new cases of adult MB. Imaging studies in these patients revealed the morphological appearance of high-grade, well-circumscribed heterogeneous tumours with necrosis, located laterally within the posterior cranial fossa. Histopathology of resected samples demonstrated high-grade tumours (WHO grade IV) containing sheets of undifferentiated neural cells with high mitotic activity and evidence of necrosis. The histopathologic and molecular characteristics of these cases of MB are reviewed for potential applications in new molecular methods of imaging.

The 'omics' of adrenocortical tumours for personalized medicine

Pan-genomic analyses of genetic and epigenetic alterations and gene expression profiles are providing important new insights into the pathogenesis and molecular classification of cancers. The technologies and methods used for these studies are rapidly diversifying and improving. The use of such methodologies for the analysis of adrenocortical tumours has revealed clear transcriptomic (mRNA and microRNA expression profiles), epigenomic (DNA methylation profiles) and genomic (DNA mutations and chromosomal alterations) differences between benign and malignant tumours. Interestingly, genomic studies of adrenal cancers have also identified subtypes of malignant tumours, which demonstrate distinct patterns of molecular alterations and are associated with different clinical outcomes. These discoveries have created the opportunity for classifying adrenocortical tumours on the basis of molecular analyses. Following these genomic studies, efforts to develop new molecular tools that improve diagnosis and prognostication of patients with adrenocortical tumours have also been made. This Review describes the progress that has been made towards classification of adrenocortical tumours to date based on key genomic approaches. In addition, the potential for the development and use of various molecular tools to personalize the management of patients with adrenocortical tumours is discussed.

The WIP1 oncogene promotes progression and invasion of aggressive medulloblastoma variants

Recent studies suggest that medulloblastoma, the most common malignant brain tumor of childhood, is comprised of four disease variants. The WIP1 oncogene is overexpressed in Group 3 and 4 tumors, which contain medulloblastomas with the most aggressive clinical behavior. Our data demonstrate increased WIP1 expression in metastatic medulloblastomas, and inferior progression-free and overall survival of patients with WIP1 high-expressing medulloblastoma. Microarray analysis identified up-regulation of genes involved in tumor metastasis, including the G protein-coupled receptor CXCR4, in medulloblastoma cells with high WIP1 expression. Stimulation with the CXCR4 ligand SDF1ααactivated PI-3 kinase signaling, and promoted growth and invasion of WIP1 high-expressing medulloblastoma cells in a p53-dependent manner. When xenografted into the cerebellum of immunodeficient mice, medulloblastoma cells with stable or endogenous high WIP1 expression exhibited strong expression of CXCR4 and activated AKT in primary and invasive tumor cells. WIP1 or CXCR4 knock-down inhibited medulloblastoma growth and invasion. WIP1 knock-down also improved the survival of mice xenografted with WIP1 high-expressing medulloblastoma cells. WIP1 knock-down inhibited cell surface localization of CXCR4 by suppressing expression of the G protein receptor kinase 5, GRK5. Restoration of wild-type GRK5 promoted Ser339 phosphorylation of CXCR4 and inhibited the growth of WIP1-stable medulloblastoma cells. Conversely, GRK5 knock-down inhibited Ser339 phosphorylation of CXCR4, increased cell surface localization of CXCR4, and promoted the growth of medulloblastoma cells with low WIP1 expression. These results demonstrate cross-talk among WIP1, CXCR4, and GRK5, which may be important for the aggressive phenotype of a subclass of medulloblastomas in children.

Cytogenetic prognostication within medulloblastoma subgroups

PURPOSE

Medulloblastoma comprises four distinct molecular subgroups: WNT, SHH, Group 3, and Group 4. Current medulloblastoma protocols stratify patients based on clinical features: patient age, metastatic stage, extent of resection, and histologic variant. Stark prognostic and genetic differences among the four subgroups suggest that subgroup-specific molecular biomarkers could improve patient prognostication.

PATIENTS AND METHODS

Molecular biomarkers were identified from a discovery set of 673 medulloblastomas from 43 cities around the world. Combined risk stratification models were designed based on clinical and cytogenetic biomarkers identified by multivariable Cox proportional hazards analyses. Identified biomarkers were tested using fluorescent in situ hybridization (FISH) on a nonoverlapping medulloblastoma tissue microarray (n = 453), with subsequent validation of the risk stratification models.

RESULTS

Subgroup information improves the predictive accuracy of a multivariable survival model compared with clinical biomarkers alone. Most previously published cytogenetic biomarkers are only prognostic within a single medulloblastoma subgroup. Profiling six FISH biomarkers (GLI2, MYC, chromosome 11 [chr11], chr14, 17p, and 17q) on formalin-fixed paraffin-embedded tissues, we can reliably and reproducibly identify very low-risk and very high-risk patients within SHH, Group 3, and Group 4 medulloblastomas.

CONCLUSION

Combining subgroup and cytogenetic biomarkers with established clinical biomarkers substantially improves patient prognostication, even in the context of heterogeneous clinical therapies. The prognostic significance of most molecular biomarkers is restricted to a specific subgroup. We have identified a small panel of cytogenetic biomarkers that reliably identifies very high-risk and very low-risk groups of patients, making it an excellent tool for selecting patients for therapy intensification and therapy de-escalation in future clinical trials.

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.