Cellular Mechanisms of PTLD in Transplant Recipients

描述（由申请方提供）：移植后淋巴组织增生性疾病（PTLD）描述了实体器官和骨髓移植的一种形态异质性并发症，范围从良性B细胞增生到恶性淋巴瘤。PTLD的标志是发展为Epstein巴尔病毒（EBV）相关的B细胞淋巴瘤。目前，PTLD还没有确定的治疗方法，报告的死亡率通常超过50%。已经使用多种策略来治疗患有PTLD的患者，例如抗病毒药物、B细胞特异性抗体（包括抗CD 20（利妥昔单抗））和过继细胞免疫疗法。然而，这些方法中的每一种都具有明显的局限性。我们广泛的长期目标是确定对PTLD相关的EBV+ B细胞淋巴瘤的生长和存活至关重要的细胞和病毒蛋白，目的是鉴定治疗靶向的新候选物。我们推测EBV通过选择宿主细胞通路来促进B细胞肿瘤的生长和存活。为了支持这一假设，我们已经确定了一种新的途径，通过该途径潜伏周期EBV蛋白，潜伏膜蛋白1（LMP 1）诱导感染的B细胞中人IL-10（hIL-10）的产生。hIL-10作为一种有效的自分泌生长因子在多种EBV+相关的恶性肿瘤，包括PTLD。我们还确定了由病毒蛋白潜伏膜蛋白2A（LMP 2A）激活的脾酪氨酸激酶（Syk）对PTLD相关B细胞系的存活至关重要。此外，我们的初步数据表明，Syk的小分子抑制剂显著抑制PTLD衍生细胞系的生长和存活。最后，我们证明LMP 1通过NF：B依赖性途径，通过赋予对CTL和NK细胞消除病毒感染和转化细胞所利用的关键死亡受体（DR）效应器机制的抗性来破坏宿主免疫。我们的研究结果暗示细胞蛋白，cFLIP在抵抗DR诱导的细胞凋亡。在本提案中，我们将靶向由关键病毒蛋白LMP 1和LMP 2a诱导的已鉴定的信号转导途径和细胞蛋白，目的是抑制PTLD相关B细胞淋巴瘤的生长。为了实现这些目标，我们提出了三个具体目标。具体目标1将研究PTLD相关的EBV+ B细胞淋巴瘤的存活对Syk的需求，并在NOD/SCID模型中测试靶向Syk作为潜在治疗策略的价值。具体目标2将定义LMP 1介导的PI 3 K/AKT信号传导轴的激活及其在hIL-10诱导中的作用。此外，干预该途径的策略将作为体内抑制肿瘤生长的手段进行测试。在特定目标3中，我们将靶向LMP 1诱导的细胞蛋白cFLIP，目的是增强宿主CTL消除EBV感染的B细胞淋巴瘤的能力。我们预计这些方法将揭示新的，有效的，治疗PTLD的治疗选择。 公共卫生相关性：爱泼斯坦巴尔病毒相关的B细胞淋巴瘤的发展仍然是一个严重的，往往是致命的，实体器官和骨髓移植的并发症。目前，还没有确定的治疗这种疾病的疗法。因此，识别和定义抑制肿瘤生长的新靶点的研究可能会导致新的诊断和治疗药物，用于预防这种毁灭性疾病。

DESCRIPTION (provided by applicant): Post-transplant lymphoproliferative disease (PTLD) describes a morphologically heterogeneous complication of solid organ and bone marrow transplantation that ranges from benign B cell hyperplasia to malignant lymphoma. The hallmark of PTLD is the development of Epstein Barr Virus (EBV)-associated B cell lymphomas. Currently, there are no established therapies for PTLD and reported mortality rates commonly exceed 50%. Multiple strategies have been utilized to treat patients with PTLD such as anti-viral drugs, B cell specific antibodies including anti-CD20 (Rituximab) and adoptive cellular immunotherapy. However, each of these approaches has distinct limitations. Our broad, long term objective has been to determine the cellular and viral proteins that are essential to the growth and survival of PTLD-associated EBV+ B cell lymphomas with the intent to identify novel candidates for therapeutic targeting. We hypothesize that EBV co-opts host cellular pathways to promote growth and survival of B cell tumors. In support of this hypothesis, we have defined a novel pathway by which the latent cycle EBV protein, latent membrane protein 1 (LMP1) induces production of human IL-10 (hIL-10) in infected B cells. hIL-10 acts as a potent autocrine growth factor in a variety of EBV+- associated malignancies including PTLD. We have also determined that the spleen tyrosine kinase (Syk), activated by the viral protein latent membrane protein 2A (LMP2A), is critical to the survival of PTLD- associated B cell lines. Moreover, our preliminary data indicate that a small molecule inhibitor of Syk significantly inhibits the growth and survival of PTLD-derived cell lines. Finally we demonstrate that LMP1 subverts host immunity through an NF:B-dependent pathway by conferring resistance to key death-receptor (DR) effector mechanisms utilized by CTL and NK cell to eliminate virally-infected and transformed cells. Our findings implicate the cellular protein, cFLIP in the resistance to DR-induced apoptosis. In this proposal we will target identified signal transduction pathways, and cellular proteins, induced by the key viral proteins LMP1 and LMP2a with the goal of inhibiting growth of PTLD-associated B cell lymphomas. To achieve these objectives we propose three specific aims. Specific Aim 1 will investigate the requirement for Syk in survival of PTLD-associated EBV+ B cell lymphomas and test, in a NOD/SCID model, the value of targeting Syk as a potential therapeutic strategy. Specific Aim 2 will define the LMP1-mediated activation of the PI3K/AKT signaling axis and its role in hIL-10 induction. Further, strategies to intervene in this pathway will be tested as a means to inhibit tumor growth in vivo. In Specific Aim 3, we will target the LMP1-induced cellular protein, cFLIP with the intent to boost the ability of host CTL to eliminate EBV-infected B cell lymphomas. We anticipate that these approaches will reveal novel, and effective, therapeutic options for the treatment of PTLD.7. PUBLIC HEALTH RELEVANCE: The development of Epstein Barr Virus-associated B cell lymphomas remains a serious, and often fatal, complication of solid organ and bone marrow transplantation. Currently, there are no established therapies for treatment of this disease. Thus, studies that identify and define novel targets for inhibiting tumor growth could lead to new diagnostic and therapeutic agents for prevention of this devastating disease.