Targeting the p62 signalosome in leukemia.

项目摘要/摘要 具有某些亚型白血病的患者由于对电流的抵抗而导致悲惨的结局 治疗选择，特别是对于MLL重排的患者。慢性核因子-κB活性在 白血病细胞，特别是在白血病干细胞(LSC)群体中，并被认为是 白血病的发生，包括MLL驱动的白血病。鉴于NF-κB的多效性功能，靶向 迫切需要核因子-κB的白血病特异性功能。然而，白血病的分子机制-- 核因子-κB的具体功能尚不清楚。先前的研究涉及适配器蛋白序列1(也称为 AS p62)是正常造血干/祖细胞(HSPC)功能所必需的。有趣的是，我们发现 P62在白血病细胞中过表达，并与白血病患者肿瘤坏死因子α的升高有关。P62是 通过其ZZ结构域与RIPK1(p62/RIPK1)形成信号体，反应肿瘤坏死因子α，导致核因子-κB 激活。我们的功能研究表明，p62是白血病细胞通过激活NF-κB发挥功能所必需的， 表明HSPC在转化和p62介导的信号转导过程中获得对p62功能的依赖 途径代表了一种激活核因子-κB的白血病特异性机制。我的长期目标是改善 通过确定白血病特有的信号通路和测试新的治疗方法进行靶向治疗。 这项建议的目的是：(1)确定p62对促进白血病的贡献；(2)阐明 P62在白血病中激活NF-κB的分子机制；(3)针对白血病特异性基因的检测 P62信号体与一种小分子化合物作为灭活NF-κB和抑制白血病细胞的手段 LSC，同时保留正常HSPC。我们假设p62通过形成白血病来促进白血病- 激活核因子-κB的特异性p62/RIPK1信号体，特别是考虑到p62支持MLL白血病细胞 生长和NF-κB介导MLL诱导的白血病发生，我们将确定p62在促进中的作用 检测MLL-AF9敲击小鼠白血病前期及p62的白血病表型 缺失(MLL-AF9+/-；p62？/？小鼠)。我们将确定p62是否通过激活NF-κB促进白血病。 此外，我们还将确定p62是否与白血病细胞中的RIPK1结合，以及p62/RIPK1是否 信号小体在核因子-κB的激活和白血病的发生中是必不可少的。此外，我们还将研究ZZ是否 P62上的结构域是形成p62/RIP信号小体、激活NF-κB和促进白血病发生所必需的。 最后，我们将测试一种专门针对p62ZZ结构域的小分子化合物 P62/RIPK1信号小体，失活NF-κB，抑制白血病细胞和LSC，同时保持正常 HSPC。我们预计靶向白血病特异的p62信号小体在没有 破坏正常细胞。这项拟议的研究将影响我们对白血病特异性信号的理解 小路。这项研究的发现将有助于我们设计新的治疗策略，提高特异性 针对侵袭性白血病亚型的靶向治疗。

Project Summary/Abstract Patients with certain subtypes of leukemia are associated with dismal outcomes due to resistance to current treatment options, particularly for those with MLL rearrangements. Chronic NF-κB activity is observed in leukemia cells, especially within the leukemia stem cell (LSC) population, and is implicated as a requirement for leukemogenesis, including the MLL-driven leukemia. Given the pleotropic function of NF-κB, targeting the leukemia-specific function of NF-κB is urgently needed. However, the molecular mechanism of the leukemia- specific function of NF-κB is unclear. Previous studies implicate the adaptor protein Sequestosome 1 (also known as p62) as dispensable for normal hematopoietic stem and progenitor cell (HSPC) function. Intriguingly we find that p62 is overexpressed in leukemia cells, and associated with increased TNFα in leukemia patients. p62 was shown to form a signalosome with RIPK1 (p62/RIPK1) via its ZZ domain in response to TNFα, leading to NF-κB activation. Our functional study reveals that p62 is required for leukemia cell function through activating NF-κB, indicating HSPC acquire a dependency on p62 function during transformation and p62-mediated signaling pathway represents a leukemia-specific mechanism that activates NF-κB. My long-term goal is to improve the targeted therapy by identifying leukemia-specific signaling pathways and testing novel therapeutic approaches. The objectives of this proposal are to: (1) determine the contribution of p62 to promoting leukemia; (2) elucidate the molecular mechanism of p62 in activating NF-κB in leukemia; and (3) test targeting the leukemia-specific p62 signalosome with a small molecule compound as a means to inactive NF-κB and inhibit leukemia cell and LSC while preserving normal HSPC. We hypothesize that p62 promotes leukemia by forming a leukemia- specific p62/RIPK1 signalosome that activates NF-κB. In particular, given that p62 supports MLL leukemia cell growth and NF-κB mediates MLL-driven leukemogenesis, we will determine the contribution of p62 in promoting MLL leukemia by examining preleukemia and leukemia phenotype in Mll-AF9 knockin mice followed by p62 deletion (Mll-AF9+/-;p62?/?mice). We will determine whether p62 promotes leukemia through activating NF-κB. In addition, we will determine whether p62 binds RIPK1 in leukemia cells, and whether the p62/RIPK1 signalosome is essential for NF-κB activation and leukemogenesis. Moreover, we will examine whether the ZZ domain on p62 is required for forming the p62/RIP signalosome, activating NF-κB and promoting leukemia. Finally, we will test a small molecule compound that specifically targets the p62 ZZ domain in disrupting the p62/RIPK1 signalosome, inactivating NF-κB and inhibiting leukemia cells and LSC while preserving normal HSPC. We anticipate that targeting the leukemia-specific p62 signalosome exerts antileukemia effect without damaging normal cells. The proposed study will impact on our understanding on leukemia-specific signaling pathways. The findings from this study will help us design novel therapeutic strategies that improve the specificity of targeted therapy for aggressive subtypes of leukemia.