Stress and Proliferation States Impact MicroRNA-Mediated Regulation in Cancer

描述(申请人提供)：microRNAs被预测调节人类细胞中的大多数基因，一些miRNAs的过度表达和缺失与不同癌细胞的恶性表型有关。MiRNA活性的降低是最常见的观察结果，可能对肿瘤细胞的可塑性在分化状态之间的转换和在不同的利基环境中生长至关重要。这项建议的主要目的之一是研究miRNAs亚群在促进肿瘤细胞特性方面的功能，特别是这些细胞对应激反应的能力。许多癌症的治疗方法由于DNA损伤、未折叠蛋白质的存在、生存信号的剥夺和氧气的存在而导致应激。我们发现，miRNA调控的丧失使许多类型的癌细胞对这种应激剂高度敏感。例如，在许多癌细胞中缺失DICER，这是合成大多数miRNAs所需的双链内切酶，可以产生活细胞，这些细胞实际上可以在异种移植挑战中产生肿瘤，但对压力非常敏感。尚未观察到DICER缺失的人类癌症，但最近在几种不同类型的人类癌症中对单倍体DICER基因进行测序发现了一个特定点突变，该突变使一个RNaseIII结构域失活。这表明，这些肿瘤细胞被强烈地选择用于丢失miRNAs的子集和保留其他miRNAs。表达该突变的细胞缺乏let-7miRNA家族的表达，但表达接近正常水平的其他miRNAs。这项提案的四个具体目标建立在过去四年的进展基础上。首先，我们将进一步研究针对DICER空细胞中特定RNA序列的ArgAerte 2(Ago2)因子的性质。我们还将研究这种靶向如何通过共同结合miRNA来提高沉默的数量水平。其次，我们将表征由特定功能突变产生的miRNAs的子集，并确定这些子集的表达对肿瘤表型和应激反应的影响。第三，我们将测试DICER的抑制剂是否应该被认为是与化疗相结合的治疗癌症的药物开发的有前途的目标。第四，我们将研究对于合成miRNAs有缺陷的胚胎干细胞的生存所必需的ArgAerte功能，即DICER为空。

DESCRIPTION (provided by applicant): MicroRNAs are predicted to regulate a majority of genes in human cells and both overexpression and loss of expression of some miRNAs are correlated with malignant phenotypes in different cancer cells. A decrease in miRNA activity is most commonly observed and may be important for the plasticity of tumor cells to undergo transitions between differentiation states and to grow in different niches. One of the major objectives of this proposal is to investigate the functions of subsets of miRNAs in contributing to the properties of tumor cells and specifically to the ability of these cells to respond to stress. Many therapeutic treatments of cancer induce stress due to DNA damage, presence of unfolded proteins, deprivation of survival signals, and oxygen. We found that loss of miRNA regulation renders many types of cancer cells hypersensitive to such stress agents. For example, deletion of Dicer, a double strand endonuclease required for synthesis of most miRNAs, in many cancer cells yields viable cells that can in fact produce tumors in xenograft challenges but are hypersensitive to stress. Dicer- null human cancers have not been observed but recently sequencing of a haploid Dicer gene in several different types of human cancers identified a specific point mutation that inactivated one RNase III domain. This indicates that these tumor cells are being strongly selected for loss of a subset of miRNAs and for retention of other miRNAs. Cells expressing this mutant Dicer are defective for expression of the let-7 miRNA family but express near normal levels of other miRNAs. The four specific aims of this proposal build from progress over the past four years. First, we will further investigate the nature of factors targeting Argonaute 2 (Ago2) to specific RNA sequences in Dicer null cells. We will also investigate how this targeting enhances the quantitative level of silencing by co-binding miRNA. Second, we will characterize the subset of miRNAs generated by mutations of specific functions of Dicer and determine the consequences of expression of these subsets on tumor phenotype and response to stress. Third we will test if an inhibitor of Dicer should be considered as a promising objective for drug development to treat cancer in conjunction with chemotherapy. And fourth, we will investigate the function of Argonaute that is essential for viability in embryonic stem cells defective for synthesis of miRNAs, i.e. null for Dicer.