Epstein-Barr Virus-Enhanced Tumor Progression

描述（由申请人提供）：在与人类癌症病原学相关的人类病毒中，Epstein Barr病毒（EBV）是不寻常的，因为它与多种恶性肿瘤相关，如果只是零星的。我们的长期目标是了解一种普遍存在的、持续存在的病毒病原体是如何在初次感染数年后与宿主保持持久关系的。新出现的可能性更充分地承认EBV在终身携带者状态下的机会主义，包括病毒进入更容易感染的细胞的再激活，以及由于先前存在的分子改变而增强的EBV恶性进展。在这里，我们在一个新的概念框架内研究EBV的肿瘤发生，即肿瘤细胞被宿主内源性病毒偶然感染，在EBV促进肿瘤生长后，一些肿瘤可能会丢失病毒DNA。目的1将利用EBV在人类肿瘤活检中的分布和克隆模式，通过激光捕获显微解剖和单细胞定量PCR识别，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EBV末端重复（TR）序列，包括LMP2A基因的第一个内含子，如何控制EBV癌蛋白的表达水平。由于TRs是一种常用的肿瘤克隆性的病毒标记物，所获得的信息可能暗示了TR数本身在细胞选择过程中驱动了从少数肿瘤细胞的多锥感染到LMP2A最高表达亚群的单克隆生长的转变。目标3将定义EBV冗余和损失的基因组学。在一个新设计的体外短暂感染系统中，我们将确定EBV通过细胞是否产生表观遗传基因沉默，作为多步骤癌变过程的一个组成部分。这项研究的公共卫生意义在于，它将回答EBV与不断扩大的人类肿瘤之间不稳定联系的本质的基本生物学问题。EBV是否有能力启动目前基于EBV克隆性的假设所发现的每一种肿瘤，或者它是否有助于疾病的晚期阶段，进入更容易感染和恶性进展的细胞，通过先前的分子事故？获得的信息将进一步阐明EBV在人类癌症中的作用，其预后意义和未来的治疗方法。

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.