Interplay between PDGFRA, oxygen-regulated translation and KSHV in Kaposi's sarcomagenesis

尽管我们对KSHV的发病机制和合理设计的治疗方法的实施有所了解 基于这些进展，晚期KS大多是一种不治之症，许多最有希望的新疾病 在抗逆转录病毒治疗的背景下，治疗仍然存在重大障碍和实施问题。我们已经展示了 1)KSHV裂解基因，特别是vGPCR癌基因可以诱导PDGF介导的活化 PDGFRA是AIDS-KS中最显著激活的RTK，是致癌的驱动因素和一种 KS的治疗靶点。2)我们鉴定了PDGFRA(+)间充质干细胞为KS祖细胞； PDGFRA在血管生成的KS样环境中作为KSHV肿瘤发生的启动子，我们开发了一种 新的KSHV感染到肿瘤发生系统，允许解剖血管生成的影响 微环境和病毒和宿主机制对肿瘤发生的贡献3)我们发现 调节氧气感应机制的病毒允许病毒选择受低氧调节的替代方案 翻译起始机制eIF4EH由HIF2A激活，并由EIF4E2替代帽结合介导。这 对于KSHV复制、逃脱病毒阻断以及PDGFRA在MSCs中的致病作用是必不可少的。 这一发现的重要性在于，通过它对氧气感应机械的调节， 病毒获得翻译启动可塑性，定义为KSHV交替启动的能力 使用PI3K-调节的带有帽结合的起始复合体eIF4E合成蛋白质- AKT-mTOR-HIF1a(eIF4E1帽结合)轴或受HIF2A调控的eIF4EH(EIF4E2帽结合)。 我们假设这为病毒提供了几个我们将研究的适应性优势：1)允许 病毒在与各种组织和病理生理相对应的不同氧气水平下最大限度地复制 条件，它可能允许病毒绕过应激和先天免疫相关的以eIF2a为靶点的激酶 抑制2)它可能被病毒癌基因，如vGPCR和/或其宿主细胞信号媒介所利用 如PDGFRA用于增殖和诱导直接和旁分泌肿瘤发生3)可以允许 转化的宿主细胞在针对PDGFRA的AIDS-KS疗法的背景下是可塑性和适应性的，例如 伊马替尼，已知靶向PDGFRA-AKT-mTOR-E1-HIF1a途径。我们将聘用MSC 基于新的致癌和致瘤模型、诱导再激活模型和两种自然感染 系统和来自不同储存库的AIDS-KS样本来验证这些假设。目标1：研究KSHV如何 氧敏感机制(O2SM)的调节导致HIF2A翻译起始的激活 EIF4EH有助于KSHV的复制和先天免疫逃避。目标2：研究KSHV EIF4EH对氧敏感机制的调节导致hif2a的翻译启动 有助于KSHV在小鼠MSC和人MSCs中的致癌作用。目标3：翻译启动可塑性的作用 在介导对PDGFRA靶向治疗的耐药性方面。

In spite of our understanding of KSHV pathogenesis and the implementation of rationally designed therapies based on these advances, advanced KS is mostly an incurable disease and many of the most promising new therapies continue to have major roadblocks and implementation problems in the setting of ART. We have shown that 1) KSHV lytic genes; and particularly the vGPCR oncogene can induce- PDGF mediated activation of PDGFRA and that this is the most prominently activated RTK in AIDS-KS and it is an oncogenic driver and a therapeutic target in KS. 2) We identified PDGFRA (+) mesenchymal stem cells as KS progenitors; and PDGFRA, as an enabler of KSHV oncogenesis in an angiogenic KS like environment and we developed of a new KSHV infection-to-tumorigenesis system that allows to dissect the effect of the angiogenic microenvironment and the contribution of viral and host mechanisms to oncogenesis 3) We found that the ability of the virus to regulate the oxygen sensing machinery allowed the virus to coopt the hypoxia-regulated alternative translation initiation machinery eIF4EH activated by HIF2a and mediated by eIF4E2 alternative cap-binding. This was essential for KSHV replication, for escaping the viral shut-off and for PDGFRA driven pathogenesis in MSCs. The importance of this discovery is that through its regulation of the oxygen sensing machinery the virus access to translation initiation plasticity, defined as the ability for KSHV to alternatively initiate protein synthesis using both the initiation complex eIF4E bearing a cap-binding regulated by the PI3K- AKT-mTOR -HIF1a (eIF4E1 cap-binding) axis or the eIF4EH (eIF4E2 cap-binding) regulated by the HIF2a. We hypothesize that this provides the virus with several adaptive advantages that we will study: 1) Allows the virus to maximize replication in different oxygen levels corresponding to variety of tissues and pathophysiological conditions and it may allow the virus to bypass the stress and innate immunity-related kinases targeting eIF2a inhibition 2) It may be employed by viral oncogenes such as vGPCR and/or by its host-cell signaling mediators such as PDGFRA for proliferation and the induction of direct and paracrine oncogenesis 3) Could allow the transformed host cell to be plastic and adaptive in the context of AIDS-KS therapies targeting PDGFRA such as Imatinib, which are known to target the PDGFRA-AKT-mTOR-E1-HIF1a pathway. We will employ the MSC based de novo oncogenesis to tumorigenesis models, an induction reactivation model and two natural infections systems and AIDS-KS samples from different repositories to test these hypotheses. Aim 1: Study how KSHV regulation of the oxygen sensing machinery (O2SM) leading to HIF2a activation of translational initiation by eIF4EH contributes to KSHV replication and innate immunity evasion. Aim 2: Study mechanisms whereby KSHV regulation of the oxygen sensing machinery leading to HIF2a activation of translational initiation by eIF4EH contributes to KSHV oncogenesis in mouse MSC and human MSCs. Aim 3: Role of translation initiation plasticity in mediating resistance to PDGFRA targeted therapies.