Targeting gasdermin D to treat myelodysplastic syndromes

总结 由先天免疫系统失调和炎性小体激活诱导的骨髓炎症是 越来越多地表明在骨髓增生异常综合征（MDS）的发病机制和进展中至关重要。 尽管过去几年在这一领域取得了重大进展，但一个尚未解决的关键问题是： 是介导骨髓炎症发展的主要调节因子。解决这个问题 对于开发治疗MDS和预防其进展的新型免疫疗法至关重要， 仍然是一个严重的未满足的医疗需求。使用Diap 1和Diap 2的双敲除（DKO）小鼠模型， miR 146 a，两者都参与先天免疫信号传导并在MDS患者中显著下调， 我们发现，老年DKO小鼠发生MDS是由于骨髓中促炎细胞因子的上调。 骨髓DKO模型的独特特征之一是，这些小鼠在表型上是正常的， 年轻的年龄，但发展MDS，最终进展为白血病与衰老，这密切表型模仿 在患者中MDS的发展和进展。最近，我们发现，IL-6的遗传缺失在 DKO小鼠显著延迟MDS进展。然而，IL-6是一种高度上调的细胞因子， DKO小鼠和MDS患者。IL-6的缺失不能逆转炎症性骨髓微环境， DKO模型中的许多MDS表型。有必要揭示常见的上游调节器， 介导炎性细胞因子的释放。在这方面，IL-6是众所周知的IL-1 β的下游靶标， 其由炎症诱导的焦萎细胞释放。在炎性小体组装后， 包括NLRP 3，它是NF-κ B B的下游靶点，并通过激活先天性免疫系统而上调。 发信号。NLRP 3的激活是MDS的霍尔标志，与突变状态无关。上调和激活 NLRP 3炎性体激活半胱天冬酶1，半胱天冬酶1又切割gasdermin D。裂解的gasdermin D结果 增加的细胞渗透性、焦亡和包括IL-1家族的细胞因子的释放。鉴于其核心作用 gasdermin D可能参与MDS的发病和进展。因此我们 将DKO小鼠与gasdermin D敲除小鼠杂交。事实上，gasdermin D的缺失显著逆转了MDS， DKO小鼠中的表型。Gasdermin D在MDS患者中也高度上调。我们的初步 研究表明gasdermin D还介导骨髓基质细胞中的炎症。基于这些 数据，我们假设gasdermin D介导的炎症线索和先天免疫调节障碍， 造血细胞和骨髓基质细胞中的信号传导在促进MDS发展中是关键的， 进展为了验证这一假设，我们将在以下三个目标进行实验。在目标1中， 探讨gasdermin D在MDS发生发展中的造血细胞内在机制。 在目标2中，将分析gasdermin D在介导炎症性骨髓微环境中的作用。 目的3将重点放在通过靶向gasdermin D治疗MDS的翻译方面。成功完成 本项目的研究结果将对了解衰老相关骨髓的发病机制产生重要影响。 本发明的目的在于研究MDS中的炎症和开发新的免疫疗法以治疗MDS。

Summary Bone marrow inflammation induced by the dysregulated innate immune system and inflammasome activation is increasingly indicated to be critical in the pathogenesis and progression of myelodysplastic syndromes (MDS). Despite the significant progress in this field in the past few years, one of the key unresolved questions is: what are the major regulators that mediate the development of bone marrow inflammation. Resolving this question will be critical for the development of novel immunotherapies to treat MDS and prevent its progression, which remains to be a critical unmet medical need. Using a mouse model of double knockout (DKO) of Diap1 and miR146a, both are involved in the innate immune signaling and significantly downregulated in patients with MDS, we revealed that the old DKO mice developed MDS due to the upregulation of pro-inflammatory cytokines in the bone marrow. One of the unique features of the DKO model is that these mice are phenotypically normal at younger age but develop MDS that eventually progress to leukemia with aging, which closely phenocopies the development and progression of MDS in patients. More recently, we showed that genetic depletion of IL-6 in the DKO mice significantly delayed MDS progression. However, IL-6 is one of the highly upregulated cytokines in DKO mice and MDS patients. Loss of IL-6 failed to revert the inflammatory bone marrow microenvironment and many MDS phenotypes in the DKO model. It is essential to reveal the common upstream regulator(s) that mediate the release of inflammatory cytokines. In this respect, IL-6 is a well-known downstream target of IL-1, which is released by inflammation induced pyroptotic cells. Pyroptosis is activated upon inflammasome assembly including NLRP3, which is a downstream target of NF-b and upregulated by the activation of the innate immune signaling. Activation of NLRP3 is a hall mark of MDS independent of mutation status. Upregulated and activated NLRP3 inflammasome activates caspase 1, which in turn cleaves gasdermin D. The cleaved gasdermin D results in increased cell permeability, pyroptosis, and the release of cytokines including IL-1 family. Given its central role in pyroptosis, gasdermin D could also be involved in the pathogenesis and progression of MDS. We therefore crossed DKO mice with gasdermin D knockout mice. Indeed, loss of gasdermin D markedly reverted MDS phenotypes in the DKO mice. Gasdermin D is also highly upregulated in patients with MDS. Our preliminary studies indicate that gasdermin D also mediates inflammation in bone marrow stromal cells. Based on these data, we hypothesize that gasdermin D mediated inflammatory cues and dysregulation of innate immune signaling in hematopoietic cells and bone marrow stromal cells are pivotal in facilitating MDS development and progression. To test this hypothesis, we will perform experiments in the following three aims. In aim 1, we will investigate the hematopoietic cell intrinsic mechanisms of gasdermin D in MDS development and progression. In aim 2, the role of gasdermin D in mediating the inflammatory bone marrow microenvironment will be analyzed. Aim 3 will focus on the translational respect through targeting gasdermin D to treat MDS. Successful completion of this project will have an important impact in understanding the pathogenesis of aging associated bone marrow inflammation in MDS and developing novel immunotherapies to treat MDS.