Role of PTEN and PI-3 Kinase in Medulloblastomagenesis

髓母细胞瘤（MB）是一种发生在小脑的癌症，是最常见的恶性脑肿瘤 儿童肿瘤目前依靠放疗和化疗的治疗只能治愈60%的患者， 并且在幸存者中具有严重的长期神经认知后遗症，因此开发未满足的医疗需求 更有效，毒性更小的治疗方法恶性脑瘤包括音刺猬 (SHH)MB的亚组由表达细胞的肿瘤增殖细胞（癌症干细胞; CSC）驱动 表面糖蛋白CD 15。一个知识缺口存在于控制CSC和非CSC的分子机制中， CSC表型描述不佳。该提议的中心假设是PI 3 K/PTEN 信号传导轴对SHH MB中的CSC表型施加控制，因此代表了治疗的靶点。 利用PI 3 K抑制剂。重要的是，我们实验室的工作表明， 在MB的Smo转基因（SHH途径）小鼠模型的CSC区室中，表达受到抑制。 我们的发现强调了PTEN缺陷Smo转基因小鼠模型的临床相关性， 人类MB中PTEN表达缺失，并且观察到PTEN表达缺失与MB的生存率低下相关 患者我们的拨款建议，根据我们的初步数据，提出了3个具体目标：1）确定是否遗传 PTEN或PI 3 K特异性亚型的改变对于SHH驱动的CSC表型是必要的和/或足够的 2）利用高通量激酶组文库筛选和小鼠的基因组谱分析， 人MB CSC和非CSC以鉴定分子特征和合成致死效应， 预测对PI-3 K抑制剂的敏感性或抗性。3)阐明了PTEN是通过其表观遗传机制， 在人SHH PDX模型和SmoTg GEMM模型的CSC隔室中调节;重点关注 PTEN特异性miRNA调控网络。我们将使用Math 1creER重组酶来产生 正常小脑颗粒神经元前体细胞中PTEN、p110 β和/或p110 β的条件性缺失 在某些实施方案中，本发明涉及在GNP（GNP）或CSC隔室中的细胞内表达MB和CSC，并确定对MB和CSC表型的发育的影响。 在目标2中，我们将扩展我们最近的报告，证明PI 3 K抑制剂BKM 120的活性 包括与其他靶向药物和常规药物的合成致死性筛选 化疗药物我们应用的一个创新部分是最近发现了一种新的miRNA 在CSC区室中表观遗传调节与CSC相关的PTEN的网络 表型将在我们的GEMM、MB PDX模型和人MB肿瘤中探索该观察结果 以确定这些miRNA在调节PTEN、PI 3 K和CSC表型中的作用 包括肿瘤起始活性。所提出的工作是重要的，因为它将：1）建立PTEN的作用， p110 β和p110 β在MB 2中CSC生物学中的应用）鉴定了与PI 3 K抑制相结合的新的合成致死性 和3）阐明了miRNA网络在控制PTEN和CSC表型中的作用。

Medulloblastoma (MB) is a cancer arising within the cerebellum, and is the most common malignant brain tumor in children. Current care which relies on radiotherapy and chemotherapy, only cures 60% of patients, and has serious long-term neurocognitive sequelae in survivors, hence the unmet medical need to develop more efficacious, less toxic therapies for this disease. Malignant brain tumors including the sonic hedgehog (SHH) subgroup of MB are driven by tumor propagating cells (cancer stem cells; CSCs) expressing the cell surface glycoprotein CD15. A knowledge gap exist in that the molecular mechanisms controlling CSC and non CSC phenotypes are poorly delineated. The central hypothesis for this proposal is that the PI3K/PTEN signaling axis exerts control over the CSC phenotype in SHH MB and hence represents a target for therapeutic exploitation with PI3K inhibitors. Importantly, work from our laboratory has demonstrated that PTEN expression is suppressed in the CSC compartment of the Smo transgenic (SHH pathway) mouse model of MB. The clinical relevance of the PTEN deficient Smo transgene mouse model is highlighted by our finding that PTEN expression is lost in human MB, and the observation that PTEN loss correlates with poor survival in MB patients. Our grant proposal, guided by our preliminary data proposes 3 specific aims: 1) Determine if genetic alterations in PTEN or specific isoforms of PI3K are necessary and/or sufficient for SHH driven CSC phenotype and tumorigenesis 2) Utilize high throughput kinome library screens and genomic profiling of mouse and human MB CSCs and non CSCs to identify a molecular signature and synthetic lethality effects which will predict sensitivity or resistance to a PI-3K inhibitor. 3) Elucidate the epigenetic mechanism by which PTEN is regulated in the CSC compartment in human SHH PDX models and the SmoTg GEMM model; Focused on PTEN specific miRNA regulatory networks. We will use the Math1creER recombinase to generate the conditional deletion of PTEN, p110 and/or p110 in normal cerebellar granule neuronal precursor cells (GNPs) or in the CSC compartment and determine the effects on the development of MB and CSC phenotype. In Aim 2, we will expand upon our recent report demonstrating the activity of the PI3K inhibitor, BKM120 against CSCs to include synthetic lethality screens with other targeted agents and conventional chemotherapeutics. An innovative component of our application is the recent discovery of a novel miRNA network which epigenetically regulates PTEN in the CSC compartment which is associated with the CSC phenotype. This observation will be explored in our GEMMs , MB PDX models and in human MB tumor samples to determine the role of these miRNAs in the regulation of PTEN, PI3K and the CSC phenotypes including tumor initiating activity. The proposed work is significant in that it will: 1) establish a role for PTEN, p110 and p110 in CSC biology in MB 2) identify novel synthetic lethalities in combination with PI3K inhibition in MB CSCs and 3) elucidate a role for miRNA networks in the control of PTEN and CSC phenotypes.