Merkel cell polyomavirus infection, host response, and viral oncogenic mechanism

项目摘要 默克尔细胞多瘤病毒(MCPyV)是最新发现的肿瘤病毒，可引起高度 侵袭性皮肤癌称为默克尔细胞癌(MCC)。而MCC的发病率有 在过去20年中，转移性MCC的发病率增加了两倍，目前还没有有效的疗法，这突显了 需要更好地了解MCPyV的致癌机制，才能发展得更成功 治疗。MCPyV无症状地感染大多数人，但往往会导致MCC 老年人和免疫功能受损的个人。这些观察表明，宿主免疫力 在控制MCPyV诱导的肿瘤发生中起关键作用。然而，人们对此知之甚少。 MCPyV引起的先天免疫反应。目前也不清楚调节失调的免疫系统是如何 系统在MCC肿瘤的发生中起作用。这在很大程度上是因为MCPyV的向向性以前是 MCPyV的生物学特性尚不清楚，缺乏与生物学相关的培养体系。最近，我们 发现人类真皮成纤维细胞(HDF)支持生产性MCPyV感染和 建立了MCPyV体外和体外感染模型。使用这些系统，我们 研究表明，MCPyV感染激活了刺痛介导的先天性免疫反应，这在 反过来，限制病毒的扩增和传播。此外，我们还发现，斯汀被沉默了 MCPyV(+)MCC肿瘤，表明刺痛功能的丧失是推动MCC肿瘤发生的必要因素。 我们的研究表明，刺痛功能的中断可能会导致病理上的猖獗复制 MCPyV促进病毒基因组整合到宿主基因组，这是MCPyV的关键事件- 推动了肿瘤的发生。此外，刺痛功能的丧失可能会导致MCPyV诱导的癌前病变 以规避其对肿瘤的抑制作用，从而刺激细胞增殖和肿瘤形成。 在这些观察的基础上，我们假设刺痛不仅是一种关键的抗病毒药物 控制MCPyV感染的免疫介质，但也是阻断MCPyV感染的主要肿瘤抑制因子 MCPyV驱动的肿瘤发生。为了验证这一假设，我们将结合体外和体外MCPyV 用3D“人造人类皮肤”在小鼠体内重建感染模型以检查刺痛的影响 MCPyV感染的先天免疫感知通路(目标1)和确定如何干扰 STING信号影响MCPyV驱动的MCC肿瘤发生(目标2)。通过揭示很大程度上 MCPyV和先天免疫系统之间未知的相互作用，我们的最终目标是了解 MCPyV感染控制不善如何导致MCC发展。免疫效应器的识别 正常情况下限制MCPyV传播也可能揭示预防和治疗的新策略 毁灭性的MCC癌症。

Project Summary Merkel cell polyomavirus (MCPyV), the most recently discovered tumor virus, can cause a highly aggressive form of skin cancer called Merkel cell carcinoma (MCC). While the incidence of MCC has tripled over the past twenty years, there is no effective therapy for metastatic MCCs, highlighting the need to better understand MCPyV oncogenic mechanism in order to develop more successful therapies. MCPyV asymptomatically infects most of the human population, but tends to cause MCC in the elderly and immunocompromised individuals. These observations suggest that host immunity plays a critical role in controlling MCPyV-induced tumorigenesis. However, very little is known about the innate immune response elicited by MCPyV. Neither is it clear how a dysregulated immune system contributes to MCC tumorigenesis. This is largely because MCPyV tropism was previously unknown and there was a lack of biologically relevant culture system for MCPyV. Recently, we discovered that human dermal fibroblasts (HDFs) support productive MCPyV infection and established the first in vitro as well as ex vivo infection models for MCPyV. Using these systems, we demonstrated that MCPyV infection activates STING-mediated innate immune responses, which in turn restrict viral amplification and spread. In addition, we discovered that STING is silenced in MCPyV(+) MCC tumors, revealing that loss of STING function is needed to drive MCC tumorigenesis. Our studies suggest that disruption of STING function may cause pathologic rampant replication of MCPyV to promote viral genome integration into the host genome, which is a key event in MCPyV- driven tumorigenesis. In addition, loss of STING function may allow MCPyV-induced pre-cancerous cells to circumvent its tumor suppressive effects, thus stimulating cell proliferation and tumorigenesis. Building on these observations, we hypothesize that STING functions not only as a key antiviral immune mediator for controlling MCPyV infection but also a prime tumor suppressor that blocks MCPyV-driven tumorigenesis. To test this hypothesis, we will combine the in vitro and ex vivo MCPyV infection models with 3D “artificial human skin” reconstructed in mice to examine the impact of STING innate immune sensing pathways on MCPyV infection (Aim 1) and to determine how disruption of STING signaling impacts MCPyV-driven MCC tumorigenesis (Aim 2). Through revealing the largely unknown interplay between MCPyV and the innate immune system, our ultimate goal is to understand how poorly controlled MCPyV infection leads to MCC development. Identification of immune effectors that normally restrict MCPyV propagation could also unveil novel strategies for preventing and treating the devastating MCC cancers.