c-Myc-regulated microRNAs in normal and pathologic cellular physiology

描述（由申请人提供）：本申请旨在竞争性更新一项高产的R01研究项目，该项目专注于阐明microRNA（miRNAs）在驱动肿瘤发生的关键信号通路中的作用。miRNA是18 - 24个核苷酸的RNA分子，其调节部分互补的靶信使RNA的稳定性和翻译效率。在过去的十年中，包括我们在内的许多实验室已经确定，miRNA在癌细胞中经常失调，并且可以影响恶性肿瘤的各个方面，包括增殖增加，细胞凋亡抵抗和转移。此外，我们的工作由该基金资助，证明了miRNA在经典癌基因和肿瘤抑制因子（包括MYC，KRAS和p53）下游提供关键功能。这些发现使我们证明了基于miRNA的治疗策略可以有效地抑制动物模型中的肿瘤发生。然而，许多重要问题仍然没有答案。我们仍然没有完全理解导致肿瘤中异常miRNA表达的机制。此外，我们对miRNAs的功能获得和丧失驱动体内肿瘤发生的分子机制知之甚少。绝大多数现有的功能数据来自于改变细胞系中的miRNA表达，这种方法并不能完全模拟miRNA如何参与肿瘤的发生和发展。在该基金的下一个资助期间，我们计划通过测试以下中心假设来解决这些关键的知识差距：首先，miRNA初级转录本的选择性剪接和序列特异性RNA结合蛋白的结合影响致癌和肿瘤抑制miRNA的表达和活性;第二，抗肿瘤发生的miRNA的活性可以抑制体内早期和晚期肝脏肿瘤发生和淋巴瘤发生。为了检验这些假设，将追求三个具体目标。在目标1中，我们将使用细胞和动物模型来直接确定选择性剪接在发育和疾病背景下（包括肿瘤模型）调节miRNA产生和活性的作用。在目标2中，将研究特异性RNA结合蛋白在调节一组抗肿瘤性miRNA的生物发生中的作用。最后，在目标3中，我们将利用新开发的具有可调控miRNA表达的小鼠模型来研究肝癌和淋巴瘤小鼠模型中miRNA介导的肿瘤抑制的潜在机制。这些目标将利用我们和我们的合作者在体外和体内评估miRNA调控和功能方面的丰富经验。我们预计，这些研究揭示的原理将广泛适用于我们对miRNA在癌症中作用的理解，并可能发现操纵miRNA表达和功能用于治疗目的的新机会。

DESCRIPTION (provided by applicant): This application is for competitive renewal of a highly productive R01 research program focused on elucidating the roles of microRNAs (miRNAs) in key signaling pathways that drive tumorigenesis. miRNAs are 18-24 nucleotide RNA molecules that regulate the stability and translational efficiency of partially complementary target messenger RNAs. Over the last decade, many laboratories including ours have established that miRNAs are frequently dysregulated in cancer cells and can influence all aspects of malignancy including increased proliferation, resistance to apoptosis, and metastasis. Moreover, our work funded by this grant has documented that miRNAs provide crucial functions downstream of classic oncogenes and tumor suppressors including MYC, KRAS, and p53. These findings led to our demonstration that miRNA-based therapeutic strategies can potently inhibit tumorigenesis in animal models. Nevertheless, many important questions remain unanswered. We still do not fully understand the mechanisms that result in abnormal miRNA expression in tumors. Furthermore, we know very little about the molecular mechanisms through which gain- and loss-of-function of miRNAs drives tumorigenesis in vivo. The vast majority of existing functional data has been derived from altering miRNA expression in cell lines, an approach that does not fully model how miRNAs participate in tumor initiation and progression. During the next funding period of this grant, we propose to address these critical knowledge gaps by testing the following central hypotheses: First, that alternative splicing of miRNA primary transcripts and association of sequence-specific RNA binding proteins influences the expression and activity of oncogenic and tumor suppressor miRNAs; and second, that the activity of anti-tumorigenic miRNAs can suppress early- and late-stage liver tumorigenesis and lymphomagenesis in vivo. Three Specific Aims will be pursued in order to test these hypotheses. In Aim 1, we will use cellular and animal models to directly determine the role of alternative splicing in regulating miRNA production and activity in developmental and disease contexts, including tumor models. In Aim 2, the role of specific RNA binding proteins in regulating the biogenesis of a set of anti-tumorigenic miRNAs will be investigated. Finally, in Aim 3, we will utilize a newly-developed mouse model with regulatable miRNA expression to investigate the mechanisms underlying miRNA-mediated tumor suppression in mouse models of liver cancer and lymphoma. These aims will take advantage of our extensive experience, and that of our collaborators, in evaluating miRNA regulation and function in vitro and in vivo. We anticipate that the principles revealed by these studies will be broadly applicable to our understanding of the roles of miRNAs in cancer and may uncover new opportunities to manipulate miRNA expression and function for therapeutic purposes.