Investigating the functions of the miR-17~92 family of oncogenic microRNA cluster

描述（由申请人提供）：微小RNA是小的非编码RNA，其最近作为后生动物和植物中基因表达的重要调节剂出现。除了在正常发育和分化中发挥重要作用外，一些miRNA已被证明是致癌基因和肿瘤抑制因子。特别是，多条证据表明miR-17~92簇包含至少一个致癌miRNA。在人类B细胞淋巴瘤的一个子集和大量其他人类癌症中经常观察到该簇的扩增和过表达。本课题的目的是研究该簇及其两个旁系同源物miR-106 b ~25和miR-106 a ~363的生物学功能、生理靶点和致癌特性。我们建议使用实验室小鼠作为这些研究的模式生物，并且我们已经产生了携带这三个簇的条件性和组成性功能丧失等位基因的小鼠。这一应用体现在三个具体目标中。目的一：研究miR-17~92及其同源基因在哺乳动物发育中的作用。本研究旨在从遗传学角度剖析miR-17~92簇，并将其编码的6种microRNA赋予特定的生物学功能。此外，它们将使我们能够确定miR-17~92与其两个旁系同源物miR-106~363和miR-106 b ~25之间的功能重叠程度。在目的2中，我们将研究miR-17~92在c-Myc诱导的B细胞淋巴瘤的背景下在肿瘤维持中的作用。这一特定目标的基本原理是基于c-Myc是miR-17~92的有效转录反式激活因子的观察，以及我们自己的初步研究表明miR-17~92的急性缺失导致E5-Myc B淋巴瘤细胞增殖的显著降低。本研究的最终目的是确定miR-17~92的药理学拮抗剂在B细胞淋巴瘤临床前模型中的治疗潜力。目标3的目的是鉴定作为miR-17~92的生理靶点的基因组，并在基于细胞的实验和体内验证它们的功能相关性。这些目标将通过结合计算和实验方法来实现，该方法利用我们最近产生的miR- 17~92的条件性敲除等位基因。我们提出的工作将增加我们对这类重要的非编码基因的生物学功能和作用机制的理解。与人类健康更大的相关性，它将提供对miRNAs在人类癌症发展中的作用的见解，并可能为基于其药理学抑制的新型治疗方法铺平道路。

DESCRIPTION (provided by applicant): MicroRNAs are small non-coding RNAs that have recently emerged as important modulators of gene expression in metazoans and in plants. In addition to playing important roles in normal development and differentiation, some miRNAs have been shown to act as oncogenes and tumor suppressors. In particular, several lines of evidence indicate that the miR-17~92 cluster includes at least one oncogenic miRNA. Amplification and overexpression of this cluster are frequently observed in a subset of human B-cell lymphomas and in a significant number of other human cancers. The goal of this project is to investigate the biological functions, the physiological targets and the oncogenic properties of this cluster and its two paralogs: miR-106b~25 and miR-106a~363. We propose to use the laboratory mouse as the model organism for these studies and we have already generated mice carrying conditional and constitutive loss-of-function alleles of these three clusters. This application is articulated in three specific aims. In aim 1 we will investigate the functions of miR-17~92 and its two paralogs in mammalian development. The experiments proposed in this aim will allow us to genetically dissect the miR-17~92 cluster and to assign specific biological functions to the six microRNAs that it encodes. In addition they will allow us to determine the extent of functional overlap between miR-17~92 and its two paralogs, miR-106~363 and miR-106b~25. In aim 2, we will investigate the role of miR-17~92 in tumor maintenance in the context of c-Myc induced B cell lymphomas. The rationale for this specific aim is based on the observation that c-Myc is a potent transcriptional transactivator of miR-17~92 and on our own preliminary studies showing that acute deletion of miR-17~92 leads to a dramatic reduction in the proliferation of E5-Myc B-lymphoma cells. The ultimate goal of this aim is to determine the therapeutic potential of pharmacological antagonists of miR-17~92 in a preclinical model of B cell lymphomas. The objective of aim 3 is to identify the set of genes that are physiologic targets of miR-17~92 and to validate their functional relevance in cell-based experiments and in vivo. These goals will be achieved by combining a computation and an experimental approached that takes advantage of the conditional knockout allele of miR- 17~92 that we have recently generated. The work we are proposing will increase our understanding of the biological functions and mechanism of action of this important class of non-coding genes. Of even greater relevance for human health, it will provide insights into the role of miRNAs in the development to human cancer and may pave the way for novel therapeutic approaches based on their pharmacological inhibition.