Role of Epstein-Barr virus LMP2A protein in maintaining oncogenic IgM signaling in EBV+ B cell lymphomas

项目摘要 EB病毒（EBV）引起广泛的淋巴瘤，包括霍奇金淋巴瘤、伯基特淋巴瘤和弥漫性大淋巴瘤。 细胞淋巴瘤（DLBCL）。EBV+淋巴瘤的比例急剧上升，发病率和死亡率也在上升。 尽管联合抗逆转录病毒治疗（cART），但仍有艾滋病毒感染者，这表明未能控制病毒 驱动淋巴瘤。然而，导致EBV驱动的淋巴瘤发生的机制仍然存在， 不太了解。该提案将调查一个概念上新颖的假设，即LMP 2A病毒 癌基因与B细胞受体（BCR）相互作用，用于维持其生长促进IgM同种型。 这一假设预测表达LMP 2A的EBV转化细胞依赖于其组成性表达。 激活抗原诱导的信号传导的细胞介质，因此将对靶向 这种信号级联，而不表达LMP 2A的EBV转化细胞将对这种信号级联产生抗性， 毒品我们的建议源于我们对淋巴母细胞的两个令人兴奋的观察 在一个实施方案中，本发明提供了由缺乏LMP 2A的EBV突变体转化的LCL（LCL LMP 2A-EBV）。首先，我们发现， 与正常LCL相比，ILMP 2A-LCL的生长不依赖于抗原诱导的信号传导介质，如 BLNK和BTK。第二，与正常LCL相反，ILMP 2A-LCL不能维持促进生长的IgM BCR的形式，而是表达IgG-BCR。由于通过IgG-BCR的抗原信号传导促进 分化成分泌高水平抗体但增殖潜力有限的浆细胞， 我们的中心假设是LMP 2A通过促进EBV的生长而促进淋巴瘤的发生 表达促生长IgM-BCR的转化的B淋巴细胞。该提案将分析机械 EBV转化的LCL中的通路和基因表达谱以及人源化细胞中的试验淋巴瘤形成 小鼠，以区分LMP 2A的直接贡献与IgM-BCR介导的直接贡献，以及 评估每一种情况下的治疗脆弱性。具体而言，我们将（1）调查 LMP 2A和BCR IG同种型对B淋巴细胞转化的影响。 LMP 2A表达的存在或不存在，和（3）确定LMP 2A介导的对 信号分子的治疗性抑制。这些研究共同为LMP 2A如何 与BCR相互作用，促进EBV转化，并为治疗提供新的机会。 EBV相关淋巴瘤的干预。

PROJECT SUMMARY Epstein-Barr virus (EBV) causes a wide spectrum of lymphomas including Hodgkin, Burkitt, and diffuse large cell lymphomas (DLBCL). The proportion of EBV+ lymphomas rises sharply as does morbidity and mortality in HIV-infected persons despite combined antiretroviral therapy (cART), suggesting specific failure to control viral driven lymphomas. However, the mechanistic processes contributing to EBV-driven lymphomagenesis remain poorly understood. This proposal will investigate a conceptually novel hypothesis that the LMP2A viral oncogene interacts with the B cell receptor (BCR), serving to maintain it in its growth promoting IgM isotype. This hypothesis predicts that EBV transformed cells expressing LMP2A are dependent upon their constitutive activation of cellular mediators of antigen-induced signaling, and thus will be susceptible to agents that target this signaling cascade, whereas EBV-transformed cells that do not express LMP2A will be resistant to such drugs. Our proposal stems from two exciting observations that we have made about lymphoblastoid cells (LCLs) transformed by an EBV mutant that lacks LMP2A (∆LMP2A-EBV). First, we discovered that, unlike normal LCLs, the growth of ∆LMP2A-LCLs is not dependent on mediators of antigen-induced signaling like BLNK and BTK. Second, in contrast to normal LCLs, ∆LMP2A-LCLs fail to maintain the growth promoting IgM form of the BCR and instead express the IgG-BCR. Since antigen signaling through IgG-BCR promotes differentiation into plasma cells which secrete high levels of antibodies but have limited proliferative potential, our central hypothesis is that LMP2A contributes to lymphomagenesis by facilitating outgrowth of EBV transformed B lymphocytes expressing the growth promoting IgM-BCR. This proposal will analyze mechanistic pathways and gene expression profiles in EBV-transformed LCLs and test lymphoma formation in humanized mice in order to distinguish the direct contributions of LMP2A from those mediated by the IgM-BCR, and assess the therapeutic vulnerability that arise from each. Specifically, we will (1) Investigate intersection of LMP2A and BCR Ig isotype on B lymphocyte transformation, (2) Characterize impact of antigenic stimulation in the presence or absence of LMP2A expression, and (3) Determine LMP2A-mediated susceptibility to therapeutic inhibition of signaling molecules. Together these studies provide a framework for how LMP2A interacts with the BCR to promote EBV transformation and provide new opportunities for therapeutic intervention in EBV-associated lymphomas.