(PQB5) Epigenetic Drivers of Hematopoietic Stem Cell Transformation

描述（由申请人提供）：本申请涉及PQB-5：突变或表观遗传变化发生的顺序如何改变癌症表型或影响靶向治疗的疗效？最近发表的来自癌症基因组图谱（TCGA）的急性髓性白血病（AML）基因组测序数据表明，>80%的AML克隆含有至少两个突变，44%包括DNA甲基化相关基因的突变，支持表观遗传调控在AML发展中起关键作用。目前尚不清楚这些突变或表观遗传变化的获得顺序如何影响AML表型和对靶向治疗的反应。由于必须对肿瘤进行连续采样和对致瘤前细胞群进行前瞻性鉴定，因此直接在人体中研究突变的组合获得具有挑战性。为了应对这一挑战，我们设计了一种基于体外的建模系统，以准确描述AML中突变的顺序获得的后果。使用该系统，我们将依次和组合诱导DNA甲基化机制中常见的复发性突变（DNMT 3A和TET 2）和FLT 3中频繁相关的激活突变（FLT 3-ITD）。我们将确定DNMT 3A，TET 2和FLT 3突变的获得顺序如何改变白血病表型，并建立预测起始突变身份的增强子活性特征。我们将测试我们的假设，即活性增强子区域可以作为识别AML起始突变的关键生物标志物，并且这些生物标志物预测对靶向DNA甲基化抑制剂地西他滨（DAC）的反应。我们的研究结果将对癌症研究产生广泛的影响，直接证明突变的获得顺序（1）改变癌症表型，（2）可以通过表观遗传生物标志物预测，（3）是治疗决策的关键因素。

DESCRIPTION (provided by applicant): This application addresses PQB-5: How does the order in which mutations or epigenetic changes occur alter cancer phenotypes or affect the efficacy of targeted therapies? Recently published genome sequencing data for acute myeloid leukemia (AML) from The Cancer Genome Atlas (TCGA) has demonstrated that >80% of AML clones contain at least two mutations, and 44% include mutations in DNA-methylation-related genes, supporting that epigenetic regulation plays a key role in AML development. It currently remains completely unknown how the order of acquisition of these mutations or epigenetic changes impacts AML phenotype and response to targeted therapy. Studying combinatorial acquisition of mutations directly in humans is challenging due to the necessity of sequential sampling of tumors and prospective identification of pre-tumorigenic cell populations. To meet this challenge, we have devised an in vitro-based modeling system to accurately depict the consequences of sequential acquisition of mutations in AML. Using this system, we will sequentially and combinatorially induce common, recurrent mutations in the DNA methylation machinery (DNMT3A and TET2) and a frequently associated activating mutation in FLT3 (FLT3-ITD). We will determine how the order of acquisition of mutations in DNMT3A, TET2 and FLT3 alters leukemia phenotype, and establish signatures of enhancer activity that are predictive of the identity of the initiating mutation. We will test our hypothesis that active enhancer regions can serve as key biomarkers for the identification of initiating mutations in AML and that these predict response to the targeted DNA methylation inhibitor decitabine (DAC). Our results will have broad impact on cancer research by direct demonstration that the order of acquisition of mutations (1) alters cancer phenotype, (2) can be predicted by epigenetic biomarkers, and (3) is a key factor for therapeutic decisions.