Probing cytosolic nucleic acid sensing pathways in cancer

摘要 哺乳动物细胞引发炎症的能力是许多过程的核心，包括胚胎发生， 伤口愈合、组织再生和癌症转移。炎症信号的一个主要来源是 细胞质中双链(DS)核酸的异常存在。哺乳动物细胞进化到了高度- Ly保守的机制是检测胞浆核酸作为一种抗病毒防御。在正常细胞中，cGAS(Cy- CLIC GMP-AMP合成酶)及其下游信号效应因子STIN(干扰素基因刺激物) 被认为是I型干扰素信号转导和下游免疫激活的重要介质。 然而，我们已经表明，在具有染色体不稳定(CIN)的癌细胞中，没有证据表明I型 尽管存在胞浆DNA和cGAS和STIN的结构性激活，但干扰素信号转导。相反， 癌细胞重新连接STING下游的信号通路，选择性地抑制干扰素信号，并使其他信号通路发挥作用。 ER促转移途径，如NF-κB。三项重要证据使埃森-埃森- CGAS-STING通路在促进抗肿瘤免疫中的作用 癌症中核酸感知的冗余和上下文相关性：1)染色体不稳定癌 细胞对胞浆dsRNA保持干扰素反应性。2)含有CIN的癌细胞仍然可以诱导出一种强大的抗肿瘤 对胞浆dsDNA的免疫应答，其方式独立于cGAS刺痛和I型干扰素。3)表达 核酸感受器和下游炎症通路在不同肿瘤亚群中的差异很大 以及转移细胞状态--在这种状态下，从干细胞样到更坚定的上皮祖细胞的连续体被观察到- 上菜了。总之，这些发现挑战了当前的观点，即cGAS-STING信号是通用的媒介- 胞浆dsDNA对炎症反应的TOR。在这里，我们的目标是了解功能冗余和 跨胞质核酸传感通路的相互作用及其转录输出如何随TU-2的变化而变化 MOR细胞分化状态。我们将系统地询问关键的核酸传感器及其下游 三种同基因小鼠模型中的效应器，其特征是转移潜能增加和高水平的 CIN。我们将在实验中操纵CIN比率来鉴定胞浆核酸依赖，但cGAS- 非刺痛免疫激活机制(目标1)。然后我们将把高吞吐量的单细胞 组合CRISPR介导的关键胞质核酸感受器基因失活和测序 肿瘤转移启动干细胞中SOX2表达与分化程度更高的效应分子的区别 对应的，以映射该途径的细胞状态特定的调控逻辑(目标2)。解开背景-- 对这一极其重要和多功能的信号级联的依赖有可能改变我们的 思考癌症的慢性炎症，揭示染色体不稳定的治疗脆弱性-- 否则对cGAS刺痛信号具有抵抗力的癌细胞。

ABSTRACT The ability of mammalian cells to elicit inflammation is central to many processes including embryogenesis, wound healing, tissue regeneration, and cancer metastasis. A major source of inflammatory signaling is the aberrant presence of double-stranded (ds) nucleic acids in the cytoplasm. Mammalian cells have evolved high- ly conserved mechanisms to detect cytosolic nucleic acids as an anti-viral defense. In normal cells, cGAS (cy- clic GMP-AMP synthase) and its downstream signaling effector STING (stimulator of interferon genes) have been proposed as essential mediators of type I interferon (IFN) signaling and downstream immune activation. We have shown however, that in cancer cells with chromosomal instability (CIN), there is no evidence of type I IFN signaling despite the presence of cytosolic DNA and constitutive activation of cGAS and STING. Instead, cancer cells rewire their signaling downstream of STING to selectively suppress IFN signaling and enable oth- er pro-metastatic pathways such as NF-κB. Three important pieces of evidence bring into question the essen- tiality of the cGAS-STING pathway in promoting anti-tumor immunity and suggest heretofore unappreciated redundancies and context dependence of nucleic acid sensing in cancer: 1) chromosomally unstable cancer cells retain IFN-responsiveness to cytosolic dsRNA. 2) Cancer cells with CIN can still elicit a robust, anti-tumor immune response to cytosolic dsDNA, in a manner independent of cGAS-STING and type I IFN. 3) Expression of nucleic acid sensors and downstream inflammatory pathways is highly variable across tumor subpopulations and metastatic cell states – in which a continuum of stem-like to more committed epithelial progenitors is ob- served. Together, these findings challenge the current view that cGAS-STING signaling is the universal media- tor of inflammation in response to cytosolic dsDNA. Herein, we aim to understand functional redundancies and interactions across cytosolic nucleic acid sensing pathways and how their transcriptional outputs vary with tu- mor cell differentiation status. We will systematically interrogate key nucleic acid sensors and their downstream effectors in three syngeneic mouse models characterized by increased metastatic potential and high levels of CIN. We will experimentally manipulate CIN rates to identify cytosolic nucleic acid-dependent, but cGAS- STING-independent mechanisms of immune activation (Aim 1). We will then couple high-throughput single-cell sequencing with combinatorial CRISPR-mediated gene inactivation of key cytosolic nucleic acid sensors and effectors in metastasis-initiating stem cells distinguished by SOX2 expression, versus their more differentiated counterparts, to map the cell state-specific regulatory logic of this pathway (Aim 2). Unraveling the context- dependence of this extremely important and versatile signaling cascade has the potential to transform our thinking about chronic inflammation in cancer and to reveal therapeutic vulnerabilities in chromosomally unsta- ble cancer cells that are otherwise resistant to cGAS-STING signaling.