Modulation of Apoptosis by IRF-4 in EBV transformation

EB病毒(Epstein-Barr Virus，EBV)感染是艾滋病患者发生淋巴瘤的重要原因，尤其是中枢神经系统淋巴瘤。EBV在体外转化人原代B细胞，其过程被认为类似于艾滋病相关中枢神经系统淋巴瘤体内EBV转化。EBV如何调节细胞基因以实现转化尚不清楚。干扰素调节因子-4(IRF-4)是IRF家族中具有致癌潜能的成员。在体外EBV转化的原代B细胞中，IRF-4高表达，在原发性中枢神经系统淋巴瘤中，IRF-4的高表达与EBV相关。此外，下调IRF-4导致EBV转化细胞的凋亡，恢复IRF-4的表达可阻止内源性IRF4-Kncokdown细胞的生长抑制。因此，IRF-4是EBV转化过程中的一个关键因子，也是EBV相关肿瘤体内潜在的治疗靶点；然而，IRF-4在EBV转化中的抗凋亡机制尚不清楚。我们的长期目标是了解细胞因子在病毒转化中的作用。这项应用的更直接的目标是确定IRF-4在EBV转化的B淋巴细胞中的抗凋亡机制。细胞凋亡大致分为内源性和外源性两种途径。EBV可诱导一些抗凋亡的Bcl2家族成员，这些成员能够阻止固有的细胞凋亡途径，并利用多种病毒蛋白阻断潜在的内在途径诱导物P53的功能。因此，我们推测，在EBV转化过程中，IRF-4可能激活并阻断了一条内在的凋亡途径。我们将检测IRF-4基因敲除后线粒体的完整性和一些标志性的caspase活性，以区分这两条途径。是否特定的半胱氨酸天冬氨酸酶的抑制剂和其他关键分子参与的凋亡拯救IRF-4基因敲除细胞的凋亡将被检测。这些实验可能会鉴定细胞的凋亡。这些实验可能确定IRF-4用来防止EBV转化细胞凋亡的关键机制。

Epstein-Barr virus (EBV) infection is an important cause of lymphomas in AIDS patients, especially in central nervous system lymphoma (CNS lymphoma). EBV transforms human primary B cells in vitro, the process of which is believed to resemble EBV transformation in vivo in AIDS-associated CNS lymphoma. How EBV regulates cellular genes to achieve the transformation remains unclear. Interferon regulatory factor-4 (IRF-4) is a member of the IRF family that has oncogenic potential. IRF-4 is highly expressed in EBV-transformed primary B cells in vitro, and high IRF-4 expression is associated with EBV in primary CNS lymphomas. Furthermore, down-regulation of IRF-4 results in apoptosis in EBV-transformed cells, and restore the IRF-4 expression prevented the growth inhibition of endogenous IRF4-kncokdown cells. Thus, IRF-4 is a critical factor involved in EBV-transformation, and a potential therapeutic target for EBV-associated tumors in vivo; however, the anti-apoptotic mechanism of IRF-4 in EBV transformation is unknown. Our long-term goal is to understand the role of cellular factors in viral transformation. The more immediate goal of this application is to determine the anti-apoptotic mechanisms of IRF-4 in EBV-transformed B lymphocytes. Apoptosis is roughly classified as intrinsic and extrinsic pathways. EBV induces some anti-apoptotic Bcl-2 family members that are capable of prevention of the intrinsic apoptosis pathway, and uses several viral proteins to block the functions of p53, a potential intrinsic pathway inducer. We thus hypothesize that an intrinsic apoptosis pathway may be activated but blocked by IRF-4 during EBV transformation. We will determine the mitochondria integrity and some hallmark caspase activities after IRF-4-knockdown to distinguish the two pathways. Whether specific inhibitors of caspases and other critical molecules involved in apoptosis rescue IRF-4-knockdown cells from apoptosis will be examined. These experiments may identify the apoptosis. These experiments may identify critical mechanisms that IRF-4 uses to prevent apoptosis in EBV-transformed cells.