Project 2: KSHV induces tumorigenesis by harnessing differentiation in hypoxia

总结 缺氧是实体瘤的特征性特征，并且由于其对肿瘤的影响而成为不良预后因素。 肿瘤进展和对治疗的抗性。卡波西肉瘤（KS）优先发展在较低的 身体的四肢，那里的血管通常氧合不良，这表明缺氧也起着重要的作用。 在KS发展中的作用。事实上，KSHV感染内皮细胞或间充质干细胞（MSC） 激活缺氧诱导因子（HIF），一种发育和病理的主要调节因子， 血管生成反过来，缺氧和HIF影响KSHV生物学和KS发展。然而，由于高度 KS肿瘤的血管表型，我们想知道缺氧反应可能不是 低氧条件下，但KSHV适应促进MSC向KS表型分化的策略。 KS病变的特征是增殖的KSHV感染的梭形细胞，密集的血管生成， 浸润的炎性细胞。KS梭形细胞的起源仍然存在争议。最近我们发现了一系列 有证据表明，KS来源于口腔间充质干细胞（MSC），通过间充质- 内皮转变（MEndT）过程（Li等，2018年）。这些发现揭示了新的病毒性肿瘤发生， 当致癌病毒劫持了多能干细胞的分化过程时，癌症可由多能干细胞产生。 受这一令人兴奋的发现的启发，我们试图阐明KSHV驱动的MEndT的机制， 肿瘤发生我们的初步研究表明，KSHV的转录组感染MSCs和KS病变 与缺氧培养的MSC的大部分重叠，提高了KSHV感染利用缺氧的可能性 促进MSC分化的应答导致KS。我们将用三个具体的假设来研究这个假设。 目标如下。(i)我们将确定KSHV如何通过劫持缺氧促进MSC分化 响应系统(ii)我们将确定KSHV和缺氧改变的信号通路，并研究它们的作用。 促进MEndT、血管生成和炎症，从而阐明KSHV的潜在机制 和低氧介导的MEndT。(iii)我们将描述MEndT期间MSC中的表观遗传调控， 揭示KSHV如何改变导致KS的调节。通过这些研究，我们将最终解决 KSHV如何将MSC转化为KS肿瘤。 我们提出的研究具有高度创新性和生物学意义。首先，这项研究将证明 关于KS梭形细胞衍生的卡波西肉瘤的性质和细胞起源的范式转变概念 KSHV感染的间充质干细胞其次，这项研究将揭示一种新的机制， 通过KSHV驱动的MEndT出现KS肿瘤细胞，以及对多灶性和寡克隆性 K的性质。第三，本研究将阐明KSHV如何利用缺氧反应促进MSC 转化为KS，并验证缺氧作为治疗KS的有效治疗靶点。

Summary Hypoxia is a characteristic feature of solid tumors and an adverse prognostic factor owing to its contributions to tumor progression and resistance to therapy. Kaposi's sarcoma (KS) preferentially develops in the lower extremities of the body, where blood vessels are often poorly oxygenated, suggesting that hypoxia also plays roles in KS development. Indeed, KSHV infection of endothelial cells or mesenchymal stem cells (MSCs) activates hypoxia-induced factor (HIF), a master regulator of both developmental and pathological angiogenesis. In turn, hypoxia and HIFs affect KSHV biology and KS development. However, given the highly vascular phenotype of KS tumor, we wonder that the hypoxia response may not be the consequence of hypoxia condition, but a strategy that KSHV adapts to promote MSC differentiation towards KS phenotypes. KS lesions are characterized by proliferating KSHV-infected spindle cells, intensive angiogenesis and infiltrating inflammatory cells. The origin of KS spindle cells remains contentious. Recently we found a series of evidence suggesting that KS derives from oral mesenchymal stem cells (MSCs) through a mesenchymal-to- endothelial transition (MEndT) process (Li et al., 2018). These findings revealed novel viral tumorigenesis that cancer can arise from pluripotential stem cells when an oncogenic virus hijacks their differentiation process. Inspired by the exciting discovery, we attempt to elucidate the mechanism underlying KSHV-driven MEndT and tumorigenesis. Our preliminary study showed that the transcriptomes of KSHV infected MSCs and KS lesions largely overlap with that of hypoxia cultured MSCs, raising a possibility that KSHV infection harnesses hypoxia response to promote MSC differentiation leading to KS. We will investigate this hypothesis with three specific aims as follows. (i) We will determine how KSHV promotes MSC differentiation through the hijacking hypoxia response system. (ii) We will identify signaling pathways altered by KSHV and hypoxia and investigate their contribution to MEndT, angiogenesis and inflammation, therefore elucidating the mechanism underlying KSHV and hypoxia-mediated MEndT. (iii) We will characterize epigenetic regulation in MSCs during MEndT, and reveal how KSHV alters the regulation leading to KS. Through these studies, we will ultimately address the question of how KSHV transforms MSC to KS tumor. Our proposed studies are highly innovative and of biological significance. First, the study will prove a paradigm-shifting concept on the nature and cellular origin of Kaposi's sarcoma that KS spindle cells derive from KSHV-infected mesenchymal stem cells. Second, the study will reveal a novel mechanism underlying the emergence of KS tumor cells through KSHV-driven MEndT and new insights into the multifocal and oligoclonal nature of KS. Third, this study will elucidate how KSHV harnesses hypoxia response to promote MSC transformation to KS and validate hypoxia as an effective therapeutic target for the treatment of KS.