Control of Breast Cancer Metastasis by Epstein-Barr Virus microRNA

描述（由申请人提供）：作用于RNA的腺苷脱氨酶（阿达尔）在dsRNA中特异性地将腺苷转化为肌苷（A至I RNA编辑）。我们的开创性研究证明了A-to-IRNA编辑参与了miRNA生物发生和功能的控制。我们最近发现，EBV（EB病毒）miRNA miR-BART 6加载到功能性RISC复合物上受到ADAR 1对其初级转录物（pri-miR-BART 6）的A至I编辑的抑制。此外，在人Dicer mRNA 3 'UTR内鉴定了miR-BART 6 - 5 p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死亡的最常见原因。上皮间质转化（EMT）在肿瘤转移中起重要作用。Snail、Slug和Twist已被确定为EMT的主要调节器。除了这些传统的转录因子蛋白质，miRNA已成为控制EMT的新的关键因子。最近的研究表明，两种miRNA，miR- 103和miR-107，通过沉默Dicer从而抑制miRNA的整体合成来促进EMT，包括主要的EMT抑制性miRNA，miR-200。EBV是最常见的人类病毒之一，感染超过90%的世界人口，并且潜伏EBV感染与多种人类癌症如伯基特淋巴瘤、霍奇金病和鼻咽癌的相关性已得到充分证实。EB病毒经常在人类乳腺癌标本中检测到。此外，已经报道了在更高级别（转移性）乳腺癌中更频繁地检测到EBV。然而，关于EBV与乳腺癌病因，特别是转移的相关性知之甚少。我们最近的研究表明，以前未探索的可能性，EBV感染可能在乳腺肿瘤转移的进展中发挥重要作用。我们推测miR-BART 6 - 5 p及其通过ADAR 1编辑通过靶向Dicer控制EMT，并有助于EBV阳性乳腺癌的转移。通过本研究计划获得的信息可能会导致转移性乳腺癌预防或治疗的新干预措施。该项目的长期目标是更好地了解EBV miR-BART 6在转移中的功能以及通过A-to-I RNA编辑介导的控制机制。具体而言，我们将确定：1）miR-BART 6 RNA在人乳腺癌细胞系中促进EMT的功能; 2）RNA编辑在miR-BART 6的EMT促进功能中的意义; 3）使用原位肿瘤植入小鼠模型，体内miR-BART 6在乳腺癌转移中的作用;和4）人乳腺肿瘤标本中miR-BART 6和ADAR 1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.