Heat Shock Transcription Factor 1 Specifically Regulates AML Stem Cell Self-Renewal

项目概要/摘要 急性髓性白血病（AML）由少数自我更新的白血病干细胞（LSC）维持。 定义和靶向特异性调节LSC的关键分子可能会根除AML。热休克 转录因子1（HSF 1）已知调节热休克蛋白（HSPs）的表达以保护细胞 由错误折叠的蛋白质引起的蛋白毒性应激。虽然HSF 1不是致癌基因，但它使癌细胞 为了适应信号传导的不平衡以及DNA、蛋白质和能量代谢的改变， 这种现象被称为“非癌基因成瘾”。目前正在探索AML中的靶向HSP， 结果然而，靶向HSPs诱导增加HSF 1活性的反馈，这可能损害 治疗效果因此，直接靶向HSF 1可能是更有吸引力的替代方案。但鉴于 HSF 1在维持正常细胞内稳态中的关键作用，靶向HSF 1可能会不利地影响 正常的造血功能出乎意料的是，我们的初步数据显示，HSF 1是正常的， 造血，但特别需要LSC的自我更新。从机制上讲，HSF 1的缺失 破坏氨基酸代谢和线粒体氧化磷酸化（OXPHOS），这在 在调节LSC功能中的作用，以及参与LSC干性的多方面基因的失调。另外我们 确定肝细胞核因子4a（HNF 4a）为HSF 1的直接靶点。HNF 4a过度表达 重建HSF 1诱导的LSC功能受损的缺失。基于这些观察，我们假设 HSF 1通过调节白血病能量代谢，是LSC自我更新所必需的 （主要是OXPHOS），并且是AML中的潜在治疗靶标。我们提出以下两个具体目标 来验证我们的假设目的1：确定HSF 1特异性需要的潜在机制 LSC自我更新我们将确定1）HSF 1消融对LSC频率，增殖和 OXPHOS; 2）通过转录组基因的综合分析， 表达、染色质可及性和染色质免疫沉淀（ChIP）测序， 3）HNF 4a如何重建HSF 1消融诱导的LSC缺陷，特别是HNF 4a的作用。 HNF 4a对OXPHOS的作用;和4）如果HSF 1的缺失在机制上损害不同类型的AML。目标2： 确定靶向HSF 1是否有效消除人类LSC。我们将确定1）HSF 1的影响 抑制人LSC增殖、凋亡、自我更新和氧化磷酸化; 2）HSF 1- 人LSC中的依赖性调节回路;以及3）如果HSF 1蛋白的表达与AML相关 治疗反应和复发。这一全面分析的预期成果是确定 HSF 1特异性调节LSC自我更新的机制，为靶向提供了理论基础 HSF 1和使用HSF 1监测AML进展。

Project Summary/Abstract Acute myeloid leukemia (AML) is maintained by a small minority of self-renewing leukemic stem cells (LSCs). Defining and targeting the key molecules that specifically regulate LSCs might eradicate AML. Heat shock transcription factor 1 (HSF1) is known to regulate the expression of heat shock proteins (HSPs) to protect cells from misfolded protein-induced proteotoxic stress. Although HSF1 is not an oncogene, it enables cancer cells to accommodate imbalances in signaling and alterations in DNA, protein, and energy metabolism, a phenomenon called “non-oncogene addiction”. Targeting HSPs in AML is being explored with promising results. However, targeting HSPs induces feedback that increases HSF1 activity, which may compromise treatment effects. Therefore, targeting HSF1 directly may be a more attractive alternative. However, given the critical roles of HSF1 in the maintenance of normal cellular homeostasis, targeting HSF1 could adversely affect normal hematopoiesis. Unexpectedly, our preliminary data show that HSF1 is dispensable for normal hematopoiesis, but specifically required for the self-renewal of LSCs. Mechanistically, deletion of HSF1 disrupts amino acid metabolism and mitochondrial oxidative phosphorylation (OXPHOS), which plays a critical role in regulating LSC function, and dysregulates multifaceted genes involved in LSC stemness. In addition, we identified that hepatocyte nuclear factor 4a (HNF4a) as a direct HSF1 target. Overexpression of HNF4a largely reconstitutes deletion of HSF1-induced impaired LSC function. Based on these observations, we hypothesize that HSF1 is specifically required for LSC self-renewal through regulating leukemic energy metabolism (mainly OXPHOS) and is a potential therapeutic target in AML. We propose the following two specific aims to test our hypothesis. Aim 1: To determine the underlying mechanism whereby HSF1 is specifically required for LSC self-renewal. We will determine 1) the impact of HSF1 ablation on LSC frequencies, proliferation and OXPHOS; 2) the HSF1 transcriptional targets in LSCs by comprehensive analysis of transcriptomic gene expression, chromatin accessibility and chromatin immunoprecipitation (ChIP) sequencing in the presence or absence of HSF1; 3) how HNF4a reconstitutes HSF1 ablation-induced LSC defects, especially the effect of HNF4a on OXPHOS; and 4) if deletion of HSF1 impairs mechanistically different types of AML. Aim 2: To determine if targeting HSF1 effectively eliminate human LSCs. We will determine 1) the impact of HSF1 inhibition on human LSC proliferation, apoptosis, self-renewal and oxidative phosphorylation; 2) the HSF1- dependent regulatory circuitry in human LSCs; and 3) if the expression of HSF1 protein correlates with AML therapeutic response and relapse. The expected outcomes of this comprehensive analysis are identification of the mechanism whereby HSF1 specifically regulates LSC self-renewal, providing the rationale for targeting HSF1 and using HSF1 to monitor AML progression.