Leveraging Vulnerabilities Induced by STING Activation in Pancreatic Cancer

项目概要/摘要 干扰素基因刺激因子（Stimulator of interferon genes，STING）是治疗实体瘤的新靶点。调查 STING激动剂的治疗相关性主要集中在免疫调节作用 在肿瘤微环境中通过STING激活依赖性诱导I型干扰素（IFN）介导。 然而，由STING激动剂诱导的IFN信号传导如何影响恶性细胞信号传导和代谢是未知的。 人们对这些作用了解甚少，而且还没有研究这些作用是否可以在治疗上加以利用。数据 显示STING在胰腺导管腺癌（PDAC）中高度过表达， 它在PDAC恶性细胞中的活化导致IFN-信号依赖性肿瘤生长受损， 方式因此，阐明STING驱动的IFN信号传导的后果在PDAC中特别相关。 这是美国癌症相关死亡率的第三大原因，总生存率低于1 年初步的代谢组学和蛋白质组学分析表明， PDAC细胞中受IFN信号传导影响的过程：（i）核苷酸代谢，这通过PDAC细胞中的IFN信号传导来证明。 脱氧核糖核苷酸三磷酸（dNTP）和烟酰胺腺嘌呤二核苷酸（NAD）池的耗尽;和 (ii)共济失调毛细血管扩张介导的DNA复制应激反应信号通路的激活， Rad 3相关蛋白（ATR）。该提议旨在检验STING驱动的dNTP和 恶性细胞中的NAD耗竭是由SAM结构域和HD结构域的转录上调引起的。 含蛋白1（SAMHD 1），一种强大的dNTP磷酸水解酶，和多聚- ADP-核糖聚合酶（PARP）家族（PARP 9/10/14），其分别增加NAD消耗。它将 进一步测试恶性细胞参与特定适应机制来抵消这些的假设。 因此，可以确定代谢改变，并且它们的抑制将与STING激动剂协同作用。目标1中的研究将 研究原位PDAC细胞系和患者来源的异种移植物中STING活化的后果 模型，并将调查STING激活和 复制应力目标2的研究将测试合理设计的联合疗法，阻断两种主要的协同作用。 PDAC细胞中STING激活引起的依赖性：（i）ATR调节的复制应激反应 和（ii）烟酰胺磷酸核糖基转移酶（NAMPT）介导的烟酰胺再循环。研究目的3 将采用免疫活性植入和自体PDAC模型来测试靶向概念 在正在进行的临床试验的背景下，在目标1和2中确定了共同依赖性，其中STING 激动剂与免疫检查点阻断剂组合。总的来说，本申请中提出的研究是 旨在增加对STING/IFN信号传导、核苷酸/NAD之间相互作用的理解， 代谢和复制压力，最终目标是发现关键漏洞， 通过新的治疗方法来对抗这种极具侵略性和难以治疗的恶性肿瘤。

PROJECT SUMMARY/ABSTRACT Stimulator of interferon genes (STING) is an emerging target for the treatment of solid tumors. Investigations of the therapeutic relevance of STING agonists have primarily focused on the immunomodulatory effects mediated by STING-activation dependent induction of type I interferons (IFN) in the tumor microenvironment. However, how IFN signaling induced by STING agonists impacts malignant cell signaling and metabolism is poorly understood and, whether these effects can be therapeutically exploited has not been investigated. Data are presented showing that STING is highly over-expressed in pancreatic ductal adenocarcinoma (PDAC) and that its activation in PDAC malignant cells results in impaired tumor growth in an IFN-signaling dependent manner. Thus, elucidating the consequences of STING-driven IFN signaling is particularly relevant in PDAC which is the third-leading cause of cancer-related mortality in the U.S. with an overall survival of less than one year. Preliminary metabolomic and proteomic analyses point to two major interconnected biochemical processes impacted by IFN signaling in PDAC cells: (i) nucleotide metabolism, which is evidenced by the depletion of deoxyribonucleotide triphosphate (dNTP) and nicotinamide adenine dinucleotide (NAD) pools; and (ii) activation of the DNA replication stress response signaling pathway mediated by Ataxia Telangiectasia and Rad3-related protein (ATR). This proposal is designed to test the hypothesis that STING-driven dNTP and NAD depletion in malignant cells result from the transcriptional upregulation of SAM domain and HD domain- containing protein 1 (SAMHD1), a powerful dNTP phosphohydrolase, and of specific members of the poly- ADP-ribose-polymerase (PARP) family (PARP9/10/14) which increase NAD consumption, respectively. It will further test the hypothesis that malignant cells engage specific adaptive mechanisms to counteract these metabolic alterations and that their inhibition will synergize with STING agonists. Studies in Aim 1 will investigate the consequences of STING activation in orthotopic PDAC cell line and patient-derived xenograft models from a pre-existing repository and will investigate mechanistic links between STING activation and replication stress. Studies in Aim 2 will test rationally designed combination therapies that block two major co- dependencies elicited by STING activation in PDAC cells: (i) the ATR-regulated replication stress response and (ii) nicotinamide phosphoribosyltransferase (NAMPT)-mediated nicotinamide recycling. Studies in Aim 3 will employ immunocompetent implantation and autochthonous PDAC models to test the concept of targeting co-dependencies identified in Aims 1 and 2 in the context provided by ongoing clinical trials in which STING agonists are combined with immune checkpoint blockade. Collectively, studies proposed in this application are designed to increase the understanding of the interplay between STING/IFN signaling, nucleotide/NAD metabolism and replication stress in PDAC with the ultimate goal of uncovering critical vulnerabilities to be exploited by new therapeutic approaches against this extremely aggressive and difficult to treat malignancy.