Control of Breast Cancer Metastasis by Epstein-Barr Virus microRNA

描述(申请人提供)：作用于RNA的腺苷脱氨酶(ADAR)专门在dsRNA(A-to-I RNA编辑)中将腺苷转化为肌苷。我们的开创性研究表明，A-to-I RNA编辑参与了miRNA的生物发生和功能控制。我们最近发现，EBV(Epstein-Barr-Virus)miRNA miR-BART6的装载被ADAR1对其初级转录产物(pri-miR-BART6)的A-to-I编辑所抑制。此外，在人Dird mRNA3‘UTR中发现了miR-BART6-5p的四个结合位点，揭示了EBV操纵宿主RNAi机制的独特策略。肿瘤转移是包括乳腺癌在内的癌症患者最常见的死亡原因。上皮向间充质转化(EMT)在肿瘤转移中起重要作用。Snail、Slug和Twist已被确定为EMT的主要调节者。除了这些传统的转录因子蛋白外，miRNAs已经成为控制EMT的新的关键因素。最近的研究表明，两个miRNAs，miR-103和miR-107，通过沉默Dester而促进EMT，从而抑制miRNAs的全球合成，包括主要的EMT抑制miR-200。EBV是最常见的人类病毒之一，感染了世界上90%以上的人口，并且潜伏的EBV感染与各种人类癌症，如Burkitt淋巴瘤、霍奇金病和鼻咽癌的相关性已经确立。在人类乳腺癌标本中经常检测到EBV。此外，在高级别(转移性)乳腺癌中更频繁地检测到EBV已有报道。然而，关于EBV与乳腺癌病因，特别是转移的相关性，我们知之甚少。我们最近的研究表明，EBV感染可能在乳腺肿瘤的转移过程中起着重要作用，这一可能性是以前未曾探索过的。我们推测miR-BART6-5p和ADAR1编辑的miR-BART6-5p通过靶向DICER调控EMT，促进EBV阳性乳腺癌的转移。通过这项研究建议获得的信息可能会导致一种新的预防或治疗转移性乳腺癌的干预措施。该项目的长期目标是更好地了解EBV miR-BART6在转移中的功能以及通过A-to-I RNA编辑介导的控制机制。具体来说，我们将确定：1)miR-BART6 RNA在促进人乳腺癌细胞株EMT中的功能；2)RNA编辑在miR-BART6促进EMT功能中的意义；3)miR-BART6在体内通过原位肿瘤移植小鼠模型在乳腺癌转移中的作用；以及4)miR-BART6和ADAR1在人乳腺肿瘤标本中的表达水平及其与转移进展的相关性。

DESCRIPTION (provided by applicant): Adenosine deaminase acting on RNA (ADAR) converts adenosine to inosine specifically in dsRNA (A-to-I RNA editing). Our pioneering studies demonstrated the involvement of A-to-I RNA editing in the control of miRNA biogenesis and function. We recently found that loading of the EBV (Epstein-Barr-virus) miRNA miR- BART6 onto a functional RISC complex is inhibited by A-to-I editing of its primary transcript (pri-miR-BART6) by ADAR1. Moreover, four binding sites of miR-BART6-5p were identified within the human Dicer mRNA 3'UTR, revealing a unique strategy of EBV to manipulate the host RNAi mechanism. Tumor metastasis is the most common cause of death in patients with cancer, including breast cancer. The Epithelial-to-Mesenchymal Transition (EMT) plays an important role in metastasis. Snail, Slug, and Twist have been identified as major regulators of EMT. In addition to these conventional transcription factor proteins, miRNAs have emerged as new key factors that control EMT. Recent studies suggest that two miRNAs, miR- 103 and miR-107, promote the EMT by silencing Dicer and thereby repressing global synthesis of miRNAs, including a major EMT-inhibitory miRNA, miR-200. EBV is one of the most common human viruses, infecting more than 90% of the world's population, and association of latent EBV infection with a variety of human cancers such as Burkitt's lymphoma, Hodgkin's disease, and nasopharyngeal carcinoma is well established. EBV is frequently detected in human breast cancer specimens. Furthermore, more frequent detection of EBV in higher grade (metastatic) breast cancers has been reported. However, very little is known about the relevance of EBV to breast cancer causation and in particular metastasis. Recent studies by us indicate a previously unexplored possibility that EBV infection may play an important role in progression of breast tumors to metastasis. We hypothesize that miR-BART6-5p and its editing by ADAR1 control EMT through targeting Dicer, and contribute to metastasis of EBV positive breast cancer. Information obtained through this research proposal may lead to a new intervention for the prevention or therapeutic treatment of metastatic breast cancer. The long-term goal of this project is to better understand functions of EBV miR-BART6 in metastasis and the control mechanism mediated via A-to-I RNA editing. Specifically, we will determine: 1) the function of miR-BART6 RNAs in promotion of EMT in human breast cancer cell lines; 2) the significance of RNA editing in the EMT promoting function of miR-BART6; 3) the role of miR-BART6 in vivo in breast cancer metastasis using an orthotopic tumor implantation mouse model; and 4) the miR-BART6 and ADAR1 expression levels in human breast tumor specimens and their relevance to metastatic progression.