7471

WNT1

INT1;wingless-type MMTV integration site family, member 1;WNT1;wingless-type MMTV integration site family, member 1

proto-oncogene Int-1 homolog|proto-oncogene Wnt-1|wingless-type MMTV integration site family, member 1 (oncogene INT1)

12q13

protein-coding

The WNT/beta-catenin pathway is involved in numerous human cancers. mutations ofthe CTNNB1 (beta-catenin) gene have also been detected in a subset of pediatric Wilms tumors, but the target genes of the deregulated WNT/beta-catenin pathway in these tumors have yet to be identified. To compare gene expression profiles of Wilms tumors with and without mutations of CTNNB1, we used 11.5-k cDNA microarrays. Most of the tumors (86%) had received preoperative chemotherapy as mandated by the European SIOP protocol. The comparison between Wilms tumors withand without CTNNB1 mutations revealed several target genes specifically deregulated in CTNNB1-mutated Wilms tumors. Among these, PITX2, APCDD1, and two members of the endothelin axis (EDN3 and EDNRA) are directly activated downstream targets of the WNT/beta-catenin pathway that may enhance proliferation of these tumor cells. In addition, several upstream inhibitors of WNT/beta-catenin signaling like WIF1 and PRDC were also strongly up-regulated in the CTNNB1-mutated Wilms tumors. This overexpression may be a negative feedback mechanism in tumors with uncontrolled WNT signaling. Moreover, we identified deregulated genes in both the retinoic acid and the RAS pathways, such as ATX/ENPP2 and RIS1, suggesting an association between these two pathways with that of WNT. In addition, the strong representation of muscle-related genes in the expression profile of CTNNB1-mutated Wilms tumors corresponded to histologically detectable areas of myomatous cells in these tumors that displayed intense and preferential nuclear beta-catenin antibody staining. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat.#CI- (c) 2006 Wiley-Liss, Inc.

Neuroblastoma (NB) is a frequently lethal tumor of childhood. MYCN amplificationaccounts for the aggressive phenotype in a subset while the majority have no consistently identified molecular aberration but frequently express MYC at high levels. We hypothesized that activated Wnt/beta-catenin (CTNNB1) signaling mightaccount for this as MYC is a beta-catenin transcriptional target and multiple embryonal and neural crest malignancies have oncogenic alterations in this pathway. NB cell lines without MYCN amplification express higher levels of MYC and beta-catenin (with aberrant nuclear localization) than MYCN-amplified cell lines. Evidence for aberrant beta-catenin-TCF transcriptional activity was demonstrated using expression profiles from 73 primary NBs. Findings included increased WNT ligands (WNT1, WNT6, WNT7A, WNT10B), DVL1 and TCF7 expression in high-risk NBs without MYCN amplification, consistent with canonical beta-cateninsignaling. More directly, Patterns of Gene expression and Gene Set Enrichment Analyses demonstrated beta-catenin target genes (for example, MYC, PPARD, NRCAM,CD44, TCF7) as coordinately upregulated in high-risk NBs without MYCN amplification in comparison to high-risk MYCN-amplified or intermediate-risk NBs, supporting pathway activation in this subset. Thus, high-risk NBs without MYCN amplification may deregulate MYC and other oncogenic genes via altered beta-catenin signaling providing a potential candidate pathway for therapeutic inhibition.

Survival rates of pediatric brain tumor patients have significantly improved over the years due to developments in diagnostic techniques, neurosurgery, chemotherapy, radiotherapy, and supportive care. However, brain tumors are stillan important cause of cancer-related deaths in children. Prognosis is still highly dependent on clinical characteristics, such as the age of the patient, tumor type, stage, and localization, but increased knowledge about the genetic and biological features of these tumors is being obtained and might be useful tofurther improve outcome for these patients. It has become clear that the deregulation of signaling pathways essential in brain development, for example, sonic hedgehog (SHH), Wnt, and Notch pathways, plays an important role in pathogenesis and biological behavior, especially for medulloblastomas. More recently, data have become available about the cells of origin of brain tumors and the possible existence of brain tumor stem cells. Newly developed array-based techniques for studying gene expression, protein expression, copy number aberrations, and epigenetic events have led to the identification of other potentially important biological abnormalities in pediatric medulloblastomas andependymomas.

Medulloblastoma (MB) is the most common malignant pediatric brain tumor. Dysregulation of WNT signaling occurs in up to 20% of cases. Using a genome-wideapproach, we identified the secreted frizzled-related protein 1, 2 and 3 (SFRP1,SFRP2 and SFRP3) family of WNT inhibitors as putative tumor suppressor genes silenced by promoter region methylation in MB. SFRP1, SFRP2 and SFRP3 expressionincreased after 5-aza-2'-deoxycytidine treatment. SFRP1, SFRP2 and SFRP3 methylation was identified in 23.5, 3.9 and 15.7% of primary MB specimens, respectively, by methylation-specific PCR. Stable SFRP1, SFRP2 and SFRP3 expression reduced phospho-DVL2 levels and hindered MB cell proliferation and colony formation in soft agar in vitro. In 60% of primary tumors, SFRP1 was expressed at levels twofold lower than that in normal cerebellum. SFRP1 expression impaired tumor formation in vivo in flank and orthotopic intracerebellar xenograft models and conferred a significant survival advantage (P<0.0001). We identify for the first time tumor suppressor gene function of SFRP genes in MB, and suggest that loss of WNT pathway inhibition due to SFRP gene silencing is an additional mechanism that may contribute to excessive WNT signaling in this disease.

Sonic Hedgehog, Wnt and PI3K/Akt are three developmental signalling cascades that ALL have crucial functions during normal brain development. The activation of one or several of these cascades is also found in the majority of medulloblastoma, the most common pediatric malignant tumor of the central nervous system. The aberrant expression of key molecules in developmental signalling pathways or inhibition of the activity of proteins regulating the activity of these cascadesis important for medulloblastoma proliferation and survival. These developmentalsignal transduction pathways transfer signals from the cell membrane to transcription factors in the nucleus, resulting in an altered gene expression. Molecular cross-talks between these developmental cascades have been described in several cancers and may have important functions in tumorigenesis. One common kinase for these three signalling cascades is GSK-3beta, which seems to be the glue that links these cascades together. Medulloblastoma cells display many characteristics that are interrelated to the progenitor cells of the embryonic brain where these developmental cascades are essential for proper development. Hence, understanding the relationship between normal brain development and medulloblastoma molecular pathogenesis is essential for more efficient, less toxic tailored therapies to be developed and implemented.#CI- (c) 2010 Landes Bioscience

Rhabdomyosarcoma is a primitive neoplasm with a poorly understood etiology that exhibits features of fetal skeletal muscle. It represents the most frequent malignant soft tissue sarcoma affecting the pediatric population and is often treated very aggressively. Embryonal rhabdomyosarcoma (ERMS) and alveolar rhabdomyosarcoma constitute the two major subtypes and exhibit different molecular features. We investigated one potential molecular basis for ERMS by using cells derived from tumors produced in p53(-/-)/c-fos(-/-) mice. This modelclosely recapitulates the timing, location, molecular markers, and histology seen in human ERMS. A combined chromatin immunoprecipitation/promoter microarray approach was used to identify promoters bound by the c-Jun-containing AP-1 complex in the tumor-derived cells that lacked c-Fos. Identification of the Wnt2gene and its overexpression in ERMS cells was confirmed in human rhabdomyosarcoma cell lines and prompted further analysis of the Wnt signaling pathway. Contrary to our expectations, the canonical Wnt/beta-catenin signaling pathway was down-regulated in ERMS cells compared with normal myoblasts, and activating thispathway promoted myogenic differentiation. Furthermore, the identification of both survivin and sfrp2 through promoter and expression analyses suggested that increased resistance to apoptosis was associated with the inhibition of the Wnt signaling pathway. These results suggest that altered AP-1 activity that leads to the down-regulation of the Wnt pathway may contribute to the inhibition of myogenic differentiation and resistance to apoptosis in ERMS cases.

Medulloblastoma encompasses a collection of clinically and molecularly diverse tumour subtypes that together comprise the most common malignant childhood braintumour. These tumours are thought to arise within the cerebellum, with approximately 25% originating from granule neuron precursor cells (GNPCs) after aberrant activation of the Sonic Hedgehog pathway (hereafter, SHH subtype). The pathological processes that drive heterogeneity among the other medulloblastoma subtypes are not known, hindering the development of much needed new therapies. Here we provide evidence that a discrete subtype of medulloblastoma that contains activating mutations in the WNT pathway effector CTNNB1 (hereafter, WNT subtype)arises outside the cerebellum from cells of the dorsal brainstem. We found that genes marking human WNT-subtype medulloblastomas are more frequently expressed in the lower rhombic lip (LRL) and embryonic dorsal brainstem than in the upper rhombic lip (URL) and developing cerebellum. Magnetic resonance imaging (MRI) and intra-operative reports showed that human WNT-subtype tumours infiltrate the dorsal brainstem, whereas SHH-subtype tumours are located within the cerebellar hemispheres. Activating mutations in Ctnnb1 had little impact on progenitor cellpopulations in the cerebellum, but caused the abnormal accumulation of cells on the embryonic dorsal brainstem which included aberrantly proliferating Zic1(+) precursor cells. These lesions persisted in ALL mutant adult mice; moreover, in 15% of cases in which Tp53 was concurrently deleted, they progressed to form medulloblastomas that recapitulated the anatomy and gene expression profiles of human WNT-subtype medulloblastoma. We provide the first evidence, to our knowledge, that subtypes of medulloblastoma have distinct cellular origins. Our data provide an explanation for the marked molecular and clinical differences between SHH- and WNT-subtype medulloblastomas and have profound implications forfuture research and treatment of this important childhood cancer.

PURPOSE: Medulloblastoma is a rare primary brain tumor in adults, whereas it constitutes the most common malignant brain tumor in children. Integrated genomics approaches revealed at least four distinct disease variants in children. The aim of this study was to investigate molecular subtypes and their prognosticimplication in a large cohort of adult medulloblastomas as the biology in this age group remains poorly understood. PATIENTS AND METHODS: We combined transcriptome and DNA copy number analyses for 28 adult medulloblastomas. Statistical and bioinformatic tools were applied to discover distinct molecular variants. Clinical and molecular characteristics of each biologic subtype were validated using immunohistochemistry on a tissue microarray derived from an independent patient cohort of adult medulloblastomas (n = 103). RESULTS: Gene expression profiles revealed three distinct molecular variants with stable subtype separation using the 300 most varying transcripts. Distinct demographics, genetics, transcriptome, and prognosis were noted for each subtype of adult medulloblastoma. Immunohistochemistry revealed aberrant activation of the sonic hedgehog (SHH) pathway in over half of adult medulloblastomas constituting a promising molecular therapeutic target. In contrast, subtype C tumors, which comprise a robust subtype in childhood medulloblastoma are only exceptionally seen in adult cohorts. Notably, adult subtype D and Wnt/wingless tumors were associated with worse prognosis than pediatric cohorts, whereas survival for SHHtumors was similar for both age groups. CONCLUSION: The transcriptome of adult medulloblastomas differs considerably from pediatric counterparts, both in termsof tumor biology and prognostic impact. Therefore, age-specific classification is required and must be adapted for use in clinical trials of adult medulloblastoma.

Although loss of p53 function and activation of canonical Wnt signaling cascadesare frequently coupled in cancer, the links between these two pathways remain unclear. We report that p53 transactivated microRNA-34 (miR-34), which consequently suppressed the transcriptional activity of beta-catenin-T cell factor and lymphoid enhancer factor (TCF/LEF) complexes by targeting the untranslated regions (UTRs) of a set of conserved targets in a network of genes encoding elements of the Wnt pathway. Loss of p53 function increased canonical Wnt signaling by alleviating miR-34-specific interactions with target UTRs, and miR-34 depletion relieved p53-mediated Wnt repression. Gene expression signatures reflecting the status of beta-catenin-TCF/LEF transcriptional activity in breastcancer and pediatric neuroblastoma patients were correlated with p53 and miR-34 functional status. Loss of p53 or miR-34 contributed to neoplastic progression by triggering the Wnt-dependent, tissue-invasive activity of colorectal cancer cells. Further, during development, miR-34 interactions with the beta-catenin UTR affected Xenopus body axis polarity and the expression of Wnt-dependent patterning genes. These data provide insight into the mechanisms by which a p53-miR-34 network restrains canonical Wnt signaling cascades in developing organisms and human cancer.

pediatric medulloblastoma is considered a highly heterogeneous disease and a newstrategy of risk stratification to optimize therapeutic outcomes is required. Weaimed to investigate a new risk-stratification approach based on expression profiles of medulloblastoma cohorts. We analyzed gene expression profiles of 30 primary medulloblastomas and detected strong evidence that poor survival outcomewas significantly associated with mRNA expression profiles of 17p loss. However,it was not supported in independent cohorts from previously published data (n = 100). We speculated that this discrepancy might come from complex conditions of two important prognostic determinants: loss of tumor suppressors (chromosome 17p) and high expression of oncogenes c-myc (MYCC) or N-myc (MYCN). When patients were stratified into 5 or 7 subgroups based on simultaneous consideration of these 2 factors while defining the Wnt group as independent, obviously different survival expectancies were detected between the subgroups. For instance, predicted 5-yearsurvival probabilities ranged from 19% to 81% in the 5 subgroups. We also found that age became a significant prognostic marker after adjusting for 17p, MYCC, and MYCN status. Diminished survival in age <3 years was more substantial in subgroups with high expression of MYCC, MYCN, or 17p loss but not in other subgroups, indicating that poor survival outcome might be synergistically affected by these 3 factors. Here we suggest a more tailored subgrouping system based on expression profiles of chromosome 17p, MYCC, and MYCN, which could provide the basis for a novel risk-stratification strategy in pediatric medulloblastoma.

Medulloblastoma is the most common malignant brain tumor in childhood. Molecularstudies from several groups around the world demonstrated that medulloblastoma is not one disease but comprises a collection of distinct molecular subgroups. However, ALL these studies reported on different numbers of subgroups. The current consensus is that there are only four core subgroups, which should be termed WNT, SHH, Group 3 and Group 4. Based on this, we performed a meta-analysis of ALL molecular and clinical data of 550 medulloblastomas brought together fromseven independent studies. ALL cases were analyzed by gene expression profiling and for most cases SNP or array-CGH data were available. Data are presented for ALL medulloblastomas together and for each subgroup separately. For validation purposes, we compared the results of this meta-analysis with another large medulloblastoma cohort (n = 402) for which subgroup information was obtained by immunohistochemistry. Results from both cohorts are highly similar and show how distinct the molecular subtypes are with respect to their transcriptome, DNA copy-number aberrations, demographics, and survival. Results from these analyseswill form the basis for prospective multi-center studies and will have an impacton how the different subgroups of medulloblastoma will be treated in the future.

Medulloblastoma is the most common malignant brain tumor of childhood, accounting for nearly 25% to 30% of primary central nervous system tumors in children younger than 18 years of age. Risk stratification into low and high risk categories has been based on age of clinical presentation, extent of postsurgical residual tumor, and disease dissemination. The World Health Organization (WHO) in 2007 recognized 5 histological subtypes as classic, anaplastic, large cell, desmoplastic/nodular, and medulloblastoma with extensive nodularity. Recent workwith gene expression profiling along with histological classification has generated a novel combined histopathological and molecular stratification schemeinto 4 subgroups (Wnt, Shh, group 3, and group 4). This could now help to identify patients who might benefit from dose escalation and de-escalation of therapy. Restratification brings optimism in treating these patients as scholarsnow have the ability to profile a more targeted therapy approach. This review discusses the literature regarding this new research endeavor.

Medulloblastoma (WHO grade IV) is a rare, malignant, invasive, embryonal tumor which mainly occurs in children and represents less than 1% of ALL adult brain tumors. Systematic comprehensive genetic analyses on medulloblastomas are rare but necessary to provide more detailed information. Therefore, we performed comprehensive cytogenetic analyses (blood and tissue) of two pediatric and one adult medulloblastoma, using trypsin-Giemsa staining, spectral karyotyping (tissues only), SNP-arrays, and gene expression analyses. We confirmed frequently detected chromosomal aberrations in medulloblastoma, such as +7q, -8p/q, -9q, -11q, -12q, and +17q and identified novel genetic events. Applying SNP-array, weidentified constitutional de novo losses 5q21.1, 15q11.2, 17q21.31, 19p12 (pediatric medulloblastoma), 9p21.1, 19p12, 19q13.3, 21q11.2 (adult medulloblastoma) and gains 16p11.1-16p11.2, 18p11.32, Yq11.223-Yq11.23 (pediatric medulloblastoma), Xp22.31 (adult medulloblastoma) possibly representing inherited causal events for medulloblastoma formation. We show evidence for somatic segmental uniparental disomy in regions 1p36, 6q16.3, 6q24.1, 14q21.2, 17p13.3, and 17q22 not previously described for primary medulloblastoma. Gene expression analysis supported classification of the adult medulloblastoma to the WNT-subgroup and classification of pediatric medulloblastomas to group 3 tumors.Analyses of tumors and matched normal tissues (blood) with a combination of complementary techniques will help to further elucidate potentially causal genetic events for medulloblastomas.#CI- Copyright (c) 2013 Elsevier GmbH. ALL rights reserved.