Regulation of Asymmetric Cellular Division in Glioma Stem Cells

描述(申请人提供)：胶质母细胞瘤(GBM)是最常见和最恶性的原发脑肿瘤。最近的研究表明，被称为胶质瘤干细胞(GSCs)的一小部分肿瘤细胞可能控制着GBM的生物学行为。GSCs具有自我更新、多潜能和高致瘤性等特性。到目前为止，它们都是通过CD133、Sox2和Nestin等特定标记的表达来鉴定的，但导致茎样行为的分子机制还没有明确定义，茎/非茎平衡的调节也没有明确的定义。这项提议旨在定义赋予GSCs类似茎的性质的分子机制，并丰富它们在GBM中的存在。在果蝇神经系统中引导不对称细胞分裂和干样行为的途径已经被很好地描述，并可能为研究恶性胶质瘤的干细胞特性和干细胞/非干细胞平衡提供线索。果蝇脑瘤(Brat)基因产物通过分离到注定要分化的子细胞来调节不对称细胞分裂，在那里它的功能是翻译抑制Myc。在Brat突变体中，不对称分裂和神经分化没有发生，导致大量扩大的幼虫脑含有高度增殖的具有肿瘤特性的未分化神经母细胞。果蝇幼虫的人类同源物Trim3在超过25%的GBM中显示等位基因丢失，在几乎所有GBM中表达减少。在目前的提案中，我们假设TriM3或其相互作用蛋白的表达减少对于定义人类GSCs的干细胞性至关重要，因为它有利于失去不对称的细胞分裂和丰富干细胞室。我们建议研究TRM3在人脑胶质瘤中的表达，以确定其在人脑胶质瘤中的表达是否下调；TRM3是否调节体内外c-Myc蛋白的表达和活性；TRM3是否在GBM神经球培养和GBM切除标本中调节人类的干细胞样特性；是否遗传和缺氧机制调节TriM3在肿瘤进展过程中的作用；以及TRM3是否调节动物模型中GBM的体内生长特性。 公共卫生相关性：胶质母细胞瘤(GBM)是一种高度恶性的脑肿瘤，通常在18个月内致命。尽管对GBM遗传学和生物学有了先进的了解，但新的治疗方法并未导致存活率的实质性改善，这突显了揭示驱动生物学机制的必要性。胶质瘤干细胞(GSCs)最近被鉴定为具有生物学功能的GBM细胞亚群，但其特化特性的机制尚不清楚。目前的提案试图定义GBM中GSC特性的基础机制，这可能会导致更好的治疗方法。

DESCRIPTION (provided by applicant): Glioblastoma (GBM) is the most common and most malignant primary brain tumor. Recent studies suggest that a small subset of neoplastic cells, referred to as Glioma Stem Cells (GSCs), may govern the biologic behavior of GBM. GSCs have properties of self-renewal, pluripotency and high tumorigenicity. They have thus far been identified by the expression of specific markers, such as CD133, Sox2 and nestin, yet molecular mechanisms responsible for stem-like behavior have not been clearly defined, nor have regulators of the stem/non-stem equilibrium. This proposal aims to define molecular mechanisms that confer stem-like qualities to GSCs and enriches their presence in GBMs. Pathways that direct asymmetric cellular division and stem-like behavior in the Drosophila melanogaster nervous system have been well described and may provide clues to stem cell properties and the stem/non-stem balance in malignant gliomas. The Drosophila brain tumor (brat) gene product regulates asymmetric cell division through its segregation into the daughter cell destined for differentiation, where it functions to translationally repress Myc. In brat mutants, asymmetric division and neural differentiation do not occur, leading to a massively enlarged larval brain containing highly proliferative undifferentiated neuroblastic cells with neoplastic properties. The human homolog of Drosophila brat, Trim3, shows allelic loss in over 25% of GBMs and reduced expression in nearly all. In the current proposal, we hypothesize that reduced expression of Trim3, or its interacting proteins, is critical in defining stem-like properties in human GSCs by favoring a loss of asymmetric cell division and enriching the stem cell compartment. We propose to investigate Trim3 in human gliomas in order to determine if its expression is downregulated in human GBMs; if Trim3 regulates c-Myc protein expression and activity in vitro and in vivo; if Trim3 regulates stem like properties of human in GBM neurosphere cultures and GBM resection specimens; if genetic and hypoxic mechanisms regulate Trim3 during tumor progression; and if Trim3 regulates the in vivo growth properties of GBM in animal models. PUBLIC HEALTH RELEVANCE: Glioblastoma (GBM) is a highly malignant brain tumor that is generally fatal within 18 months. Despite advanced understanding of GBM genetics and biology, new therapies have not led to substantial improvement in survival, highlighting the need to uncover driving biological mechanisms. Glioma stem cells (GSCs) have recently been identified as a biologically potent subset of GBM cells, yet mechanisms underlying their specialized properties are not understood. The current proposal attempts to define mechanisms that underlie GSC properties in GBM, which could lead to better therapies.