Mycn and Medulloblastoma

描述（申请人提供）：髓母细胞瘤是一种发生在中枢神经系统的肿瘤，是儿童期常见且经常致命的肿瘤。Sonic Hedgehog （SHH）和无翼信号的异常与遗传有关，然而这些途径仅在少数肿瘤中存在。原癌基因Mycn是发育中的小脑中驱动增殖的主要因素，在shh相关的髓母细胞瘤中高水平表达。在没有SHH异常的情况下，Mycn在成神经管细胞瘤的发病机制中所起的作用得到了三个独立研究的支持，这些研究表明，大多数人成神经管细胞瘤表达Mycn，而Mycn在胎儿期后的正常小脑中不表达。我们假设Mycn的异常表达与成神经管细胞瘤的发病机制有关，针对Mycn的靶向治疗将对该疾病有疗效。我们的长期目标是阐明Mycn在成神经管细胞瘤的发生和发展中的作用，并确定针对Mycn的治疗对小鼠和人成神经管细胞瘤的影响。我们将对我们实验室开发的髓母细胞瘤基因工程小鼠（GEM）模型进行表征，该模型在中枢神经系统中共同表达Mycn和荧光素酶，与现有的髓母细胞瘤GEM模型不同的是，p53突变（在人类肿瘤中不常见）不需要获得高外显率。Mycn通过激活脂质激酶PI3K来稳定。我们已经证明，PI3K的小分子抑制剂在体外和体内导致这种癌蛋白的降解。因此，我们将测试Mycn在维持肿瘤和支持肿瘤血管系统中的作用，通过使用多西环素转录关闭Mycn治疗Mycn驱动的髓母细胞瘤，或使用小分子PI3K抑制剂降解Mycn。我们将比较小鼠和人类肿瘤之间的遗传和表观遗传异常，包括microRNA分析，我们将治疗来自原发性人髓母细胞瘤的培养和异种移植肿瘤球，以评估Mycn作为人髓母细胞瘤治疗靶点的重要性。目的1。Glt1-tTA:TRE-MYCN/Luc转基因小鼠作为人髓母细胞瘤模型的评价。目标2。Glt1-tTA:TREMYCN/Luc转基因小鼠和人髓母细胞瘤肿瘤球中PI3K亚型选择性抑制剂的临床前检测目标3。使用PI3K抑制剂解决Mycn和Mycn调控的microRNA靶点在维持体内成神经管细胞瘤血管生成中的作用。公共卫生相关性：髓母细胞瘤是儿童常见且经常致命的肿瘤，目前的治疗方法往往无效。转录因子Mycn在大多数这些肿瘤中表达，我们假设这一事件与肿瘤形成有关。本应用程序的长期目标是表征我们实验室开发的髓母细胞瘤小鼠模型，并由MYCN驱动，以阐明MYCN作为该疾病治疗靶点的重要性。我们还确定了MYCN的小分子抑制剂，将在该模型和衍生模型中进行测试。这项研究将阐明Mycn作为髓母细胞瘤治疗靶点的重要性，并将评估Mycn抑制剂可能转化为患有这种重要肿瘤的儿童。

DESCRIPTION (provided by applicant): Medulloblastoma, a tumor of the central nervous system, is a common and frequently lethal tumor of childhood. Abnormalities in Sonic Hedgehog (SHH) and Wingless signaling contribute to genetics, however these pathways are represented in a minority of tumors. The proto-oncogene Mycn is the major factor driving proliferation in the developing cerebellum, and is expressed at high levels in SHH-associated medulloblastoma. A role for Mycn in the pathogenesis of medulloblastoma in the absence of SHH aberrations is supported by three independent studies showing a majority of human medulloblastomas express Mycn, whereas Mycn is not expressed in normal cerebellum after fetal stages. We hypothesize that aberrant expression of Mycn contributes to the pathogenesis of medulloblastoma, and that targeted therapies against Mycn will show efficacy in this disease. Our long term objectives are to clarify the role of Mycn in the initiation and progression of medulloblastoma, and to determine the impact of therapies directed against Mycn in murine and human medulloblastoma. We will characterize a genetically engineered mouse (GEM) model for medulloblastoma developed in our laboratory that co-expresses both Mycn and luciferase in the CNS, and that differs from existing GEM models for medulloblastoma in that p53 mutation (which is uncommon in human tumors) is not required to achieve high penetrance. Mycn is stabilized through activation of the lipid kinase PI3K. We have shown that small molecule inhibitors of PI3K lead to degradation of this oncoprotein in-vitro and in-vivo. We will therefore test the role of Mycn in maintaining tumors and in supporting tumor vasculature by treating MYCN-driven medulloblastomas using doxycyline to turn off MYCN transcriptionally, or using small molecule PI3K) inhibitors to degrade Mycn. We will compare genetic and epigenetic abnormalities between murine and human tumors, including microRNA profiling, and we will treat cultured and xenotransplated tumorspheres derived from primary human medulloblastomas to assess the importance of Mycn as a therapeutic target in human medulloblastoma. Aim 1. Evaluation of mice transgenic for Glt1-tTA:TRE-MYCN/Luc as a model for human medulloblastoma. Aim 2. Preclinical testing of isoform-selective PI3K inhibitors in mice transgenic for Glt1-tTA:TREMYCN/Luc, and in human medulloblastoma tumorspheres. Aim 3. Use of PI3K inhibitors to address a role for Mycn and microRNA targets regulated by Mycn, in maintaining medulloblastoma angiogenesis in vivo. PUBLIC HEALTH RELEVANCE: Medulloblastoma is a common and frequently lethal tumor of children, for which current therapies are often ineffective. The transcription factor Mycn is expressed in the majority of these tumors, an event we hypothesize is linked to tumor formation. The long term objective of this application is to characterize a mouse model for medulloblastoma developed in our laboratory and driven by MYCN, to clarify the importance of Mycn as a therapeutic target in this disease. We have also identified a small molecule inhibitor of MYCN, that will be tested in this and derivative models. This study will clarify the importance of Mycn as a therapeutic target in medulloblastoma, and will evaluate a Mycn inhibitor that could potentially be translated to children with this important tumor.