The miR-17/92 Polycistron Is Up-regulated in Sonic Hedgehog-Driven Medulloblastomas and Induced by N-myc in Sonic Hedgehog-Treated Cerebellar Neural Precursors

Division of Neurosurgery, Arthur and Sonia Labatt Brain Tumour Research Centre, Program in Developmental and Stem Cell Biology, Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Cancer Research (Impact Factor: 9.33). 05/2009; 69(8):3249-55. DOI: 10.1158/0008-5472.CAN-08-4710
Source: PubMed


Medulloblastoma is the most common malignant pediatric brain tumor, and mechanisms underlying its development are poorly understood. We identified recurrent amplification of the miR-17/92 polycistron proto-oncogene in 6% of pediatric medulloblastomas by high-resolution single-nucleotide polymorphism genotyping arrays and subsequent interphase fluorescence in situ hybridization on a human medulloblastoma tissue microarray. Profiling the expression of 427 mature microRNAs (miRNA) in a series of 90 primary human medulloblastomas revealed that components of the miR-17/92 polycistron are the most highly up-regulated miRNAs in medulloblastoma. Expression of miR-17/92 was highest in the subgroup of medulloblastomas associated with activation of the sonic hedgehog (Shh) signaling pathway compared with other subgroups of medulloblastoma. Medulloblastomas in which miR-17/92 was up-regulated also had elevated levels of MYC/MYCN expression. Consistent with its regulation by Shh, we observed that Shh treatment of primary cerebellar granule neuron precursors (CGNP), proposed cells of origin for the Shh-associated medulloblastomas, resulted in increased miR-17/92 expression. In CGNPs, the Shh effector N-myc, but not Gli1, induced miR-17/92 expression. Ectopic miR-17/92 expression in CGNPs synergized with exogenous Shh to increase proliferation and also enabled them to proliferate in the absence of Shh. We conclude that miR-17/92 is a positive effector of Shh-mediated proliferation and that aberrant expression/amplification of this miR confers a growth advantage to medulloblastomas.

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Available from: Timothy E Van Meter, May 22, 2014
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    • "Human primary medulloblastomas were profiled on Affymetrix Genechip Human Exon 1.0ST arrays at The Centre for Applied Genomics in Toronto, Canada ( Expression analysis was performed using Affymetrix Expression Console (Version 1.1) as previously described [26]. Additional, publically available medulloblastoma expression data sets were obtained from NCBI Gene Expression Omnibus and used to validate our findings [9,27]. "
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    ABSTRACT: 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. Electronic supplementary material The online version of this article (doi:10.1186/s40478-014-0085-y) contains supplementary material, which is available to authorized users.
    07/2014; 2(1):85. DOI:10.1186/PREACCEPT-1860372034135162
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    • "Multiple miRs can regulate the phenotype of tumor cells in these stages. The oncogenic miR-17-92 cluster can be up-regulated by c-Myc, E2F and Hedgehog [55, 56] and suppresses thrombospondin 1, thereby promoting angiogenesis [57]. Let-7 and miR-126 can inhibit proliferation through HMGA2 and PIK3 signaling [58, 59], while the hypoxia-inducible miR-210 is involved in mitochondria stabilization and regulation of cell survival/proliferation (reviewed by [60]). "
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    ABSTRACT: Oligometastasis is a cancer disease state characterized by a limited number of metastatic tumors involving single or few organs and with biological properties that make them potentially amenable to locoregional antitumor therapy. Current clinical data show that they are potentially curable with surgical resection or/and radiotherapy. Yet, mechanisms of progression from primary tumor to oligometastasis, rather than to polymetastases, is lacking in detail. In the current review we focus on the role of micro-RNAs in the regulation of metastases development and the role they may play in the differentiation of oligometastatic from polymetastatic progression. We also discuss the analyses of metastatic samples from oligo-and polymetastatic patients, which suggest that oligometastasis is a distinct biologic entity regulated in part by micro-RNAs. In addition, a review of the known functions of oligometastatic-specific micro-RNAs suggest that they regulate multiple steps in the metastatic cascade, including epithelial-mesenchymal transition, tumor invasion, intravasation, distant vascular extravasation and proliferation in a distant organ. Understanding the role of micro-RNAs and their target genes in oligometastatic disease may allow for the development of targeted therapies to effectively conrol the spread of metastases.
    Clinical and Experimental Metastasis 06/2014; 31(6). DOI:10.1007/s10585-014-9664-3 · 3.49 Impact Factor
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    • "MiRs encoded by the miR-17∼92 cluster are overexpressed in both mouse and human tumors (Uziel et al., 2009; Northcott et al., 2009). We previously found that enforced expression of the miR-17∼92 cluster collaborates with SHH signaling to induce SHH-MB (Uziel et al., 2009). "
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    ABSTRACT: The miR-17∼92 cluster family is composed of three members encoding microRNAs that share seed sequences. To assess their role in cerebellar and medulloblastoma (MB) development, we deleted the miR-17∼92 cluster family in Nestin-positive neural progenitors and in mice heterozygous for the Sonic Hedgehog (SHH) receptor Patched 1 (Ptch1(+/-)). We show that mice in which we conditionally deleted the miR-17∼92 cluster (miR-17∼92(floxed/floxed); Nestin-Cre(+)) alone or together with the complete loss of the miR-106b∼25 cluster (miR-106b∼25(-/-)) were born alive but with small brains and reduced cerebellar foliation. Remarkably, deletion of the miR-17∼92 cluster abolished the development of SHH-MB in Ptch1(+/-) mice. Using an orthotopic transplant approach, we showed that granule neuron precursors (GNPs) purified from the cerebella of postnatal day 7 (P7) Ptch1(+/-); miR-106b∼25(-/-) mice and overexpressing Mycn induced MBs in the cortices of naïve recipient mice. In contrast, GNPs purified from the cerebella of P7 Ptch1(+/-); miR-17∼92(floxed/floxed); Nestin-Cre(+) animals and overexpressing Mycn failed to induce tumors in recipient animals. Taken together, our findings demonstrate that the miR-17∼92 cluster is dispensable for cerebellar development, but required for SHH-MB development.
    Biology Open 06/2014; 3(7). DOI:10.1242/bio.20146734 · 2.42 Impact Factor
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