Epstein-Barr Virus-Enhanced Tumor Progression

描述(申请人提供)：在与人类癌症相关的人类病毒中，爱泼斯坦-巴尔病毒(EBV)是不寻常的，因为它与多种恶性肿瘤有关，即使只是零星的。我们的长期目标是了解一种普遍存在的持久病毒病原体是如何在初次感染数年后变得致病的，这种病原体通常与宿主保持着持久的融洽关系。在终生携带者状态的背景下，更充分地承认EBV机会主义的新出现的可能性包括病毒重新激活，进入更容易感染的细胞，以及EBV通过先前存在的分子变化而增强的恶性进展。在这里，我们在一个新的概念框架内研究了EBV肿瘤的发生，即宿主内源性病毒偶然感染肿瘤细胞，在EBV对生长做出贡献后，一些肿瘤可能会丢失病毒DNA。目的1利用激光捕获显微切割和单细胞定量聚合酶链式反应所识别的人类肿瘤活检组织中EBV的分布和克隆性模式，建立感染、随后的克隆进化和EBV DNA丢失的时间框架。目的2将确定可变重复的EBV末端重复序列(包括LMP2A基因的第一内含子)如何控制这种EBV癌蛋白的表达水平。由于TRS是一种常用的肿瘤克隆性病毒标记物，所获得的信息本身可能涉及到细胞选择过程，该过程推动了少数肿瘤细胞的多角体感染向具有最高LMP2A表达的亚群的单克隆性生长的转变。目标3将定义EBV冗余和丢失的基因组学。在一个新设计的体外瞬时感染系统中，我们将确定EBV通过细胞是否会产生表观遗传基因沉默，作为多步骤致癌过程的一个组成部分。这项研究的公共卫生相关性在于，它将回答有关EBV与不断扩大的人类肿瘤阵列的不稳定联系的性质的基本生物学问题。EBV是否有能力启动目前基于EBV克隆性预先假定的每一种肿瘤，或者它是否反而有助于疾病的晚期，进入更容易感染和因先前的分子事故而恶性进展的细胞？所获得的信息将进一步阐明EBV在人类癌症中的作用、其预后意义以及未来的治疗方法。

DESCRIPTION (provided by applicant): Among human viruses etiologically linked to human cancer, the Epstein Barr virus (EBV) is unusual because of the diverse assortment of malignancies with which it is associated, if only sporadically. Our long term objective is to understand how a ubiquitous and persistent viral pathogen that normally achieves a lasting rapport with its host becomes pathogenic years after primary infection. Emerging possibilities that more fully acknowledge EBV opportunism in the context of the life-long carrier state include viral reactivation with entry into cells made more prone to infection and EBV-enhanced malignant progression by pre-existing molecular alterations. Here, we examine EBV tumorigenesis within a new conceptual framework of chance infection of neoplastic cells by virus endogenous to the host, with possible viral DNA loss from some tumors after EBV contribution to growth has been made. Aim 1 will use the pattern of EBV distribution and clonality in human tumor biopsies, as discerned by laser capture microdissection and single cell quantitative PCR, to establish a time frame for infection, subsequent clonal evolution, and EBV DNA loss. Aim 2 will determine how variably reiterated EBV terminal repeat (TR) sequences, comprising the first intron of the LMP2A gene, govern expression levels of this EBV oncoprotein. With TRs a commonly employed viral marker of tumor clonality, information obtained may implicate TR number per se in a process of cell selection that drives the transition from polyconal infection of a few tumor cells to monoclonal outgrowth of a subset with the highest LMP2A expression. Aim 3 will define the genomics of EBV redundancy and loss. In a newly devised in vitro system of transient infection, we will establish whether EBV transit through a cell produces epigenetic gene silencing as a component of the multistep process of carcinogenesis. The public health relevance of this research is that it will answer fundamental biological questions on the nature of EBV's erratic association with an ever expanding array of human tumors. Does EBV have the capability to initiate every tumor in which it is found as currently presupposed on the basis of EBV clonality or does it contribute instead to late stages of disease, entering cells more prone to infection and malignant progression by prior molecular mishaps? The information gained will further elucidate EBV's role in human cancer, its prognostic significance, and future therapeutic approaches.