The Role of miRNAs in Glioma Stem Cell and Glioma Biology

在肿瘤中过度表达的microRNA可能会降低肿瘤细胞中 靶向肿瘤抑制基因，而下调的microRNA可能抑制致癌基因 有助于肿瘤形成过程（oncomirs）。此外，miRNAs通常位于 杂合性缺失区域、扩增区域或共同断裂点区域，以及 它们已经被鉴定为调节几种肿瘤相关基因的表达， 包括GBM的肿瘤。迄今为止，已经发表了几项分析miRNA表达的研究 使用不同的检测方法在正常脑和脑肿瘤中的分布。分析 小鼠和人脑miRNA显示miR-9、-101、-124和-132的不同表达 还有其他的已经发现miRNAs-10 b和-21在星形细胞肿瘤中表达上调， 前者作为癌基因减少恶性细胞的凋亡，而 miRNA-124和-137下调并参与促进神经元分化 脑肿瘤起始细胞（BTIC）和GBM细胞周期阻滞。然而， 关于星形胶质细胞中miRNAs的表达水平和靶基因调控的参与， 脑肿瘤或BTIC。为了更好地理解miRNAs在GBM调节中的作用，我们 已经开始使用基因芯片生成和比较365种miRNAs的全球表达谱， 基于定量逆转录酶聚合酶链反应（qRT-PCR）的试验， GBM和BTIC以及神经干细胞和已建立的胶质瘤细胞 在增殖和分化条件下， 改变。这项分析揭示了在细胞中统计学上显著的下调miRNAs， 肿瘤以及BTIC与非肿瘤样品的比较。此外，该表达谱是 证实BTIC是研究星形胶质细胞脑肿瘤在miRNA水平上的更好模型 比已建立的神经胶质瘤细胞系，正如我们先前所描述的，基于它们的 基因组/基因表达谱。我们也在确定表达之间的关联 我们的研究中包括的miRNAs和特定的CNA或拷贝数改变 （缺失/扩增的区域）。不一致的miRNAs CNA/表达水平表明可能的表观遗传调控，这可能将它们指向 有趣的治疗靶点。这一初步概况正以两种方式使用。一 另一方面，miRNA分析将扩展到GMDI收集的脑肿瘤中， 有价值的信息，我们已经从他们那里获得了大量的数据。另一方面，生物 证实参与胶质瘤形成、细胞增殖或特定的细胞侵袭， miRNAs及其特异性靶基因也在我们的BTIC体外模型中进行 作为体内小鼠模型。

MicroRNAs that are over expressed in tumors might diminish the level of expression of targeted tumor suppressor genes whereas microRNAs down regulated might repress oncogenic genes contributing to the neoplasic process (oncomirs). Also, miRNAs are frequently located in regions of loss of heterozygosity, regions of amplification, or common breakpoint regions and they have been identified to regulate the expression of tumor-associated genes in several tumors including GBM. Several studies have been published to date analyzing miRNA expression profiles in normal brain and brain tumors using different detection methods. Analysis of murine and human brain miRNA indicated distinctive expression of miR-9,-101,-124 and -132 among others. miRNAs -10b and -21 have been found upregulated in astrocytic tumors appearing the former to work as an oncogene decreasing apoptosis in the malignant cells, whereas miRNA-124 and -137 were down regulated and involved in promotion of neuronal differentiation of brain tumor initiating cells (BTIC) and GBM cell cycle arrest. However, little is know about the expression levels and involvement by target genes regulation of miRNAs in astrocytic brain tumors or BTIC. To better understand the role of miRNAs in the regulation of GBM, we have started generating and comparing the global profile of expression of 365 miRNAs using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) based assays in primary GBM and BTIC derived from them, as well as neuronal stem cells and established glioma cell lines in proliferating and differentiating conditions, to identify specific miRNAs alterations. This analysis is revealing statistically significant downregulation miRNAs in tumors as well as in BTIC vs. non-tumor samples. Furthermore, this expression profile is corroborating BTIC as better models at miRNA level for the study of astrocytic brain tumors than established glioma cell lines, as we have previously described based on their genomic/gene expression profiles. We are also determining the correlation between expression of the miRNAs included in our study and the particular CNA or copy number alterations (deleted/amplified regions) of our tumor/ BTISC samples. miRNAs with non concordant CNA/expression level indicate a possible epigenetic regulation, that could point them as interesting therapeutics targets. This preliminary profile is being used in two ways. On one hand, miRNA analysis will be extended to GMDI collection of brain tumors adding highly valuable information to our already extensive data from them. On the other hand, biological validation of the involvement in gliomagenesis, cell proliferation or invasion of particular miRNAs and their specific targeted genes is being performed in our BTIC in vitro model as well as in vivo mouse models.