Modeling hematologic malignancy and self-renewal with gain-of-function MLL1

利用功能获得 MLL1 模拟血液恶性肿瘤和自我更新

• 批准号: 8974958
• 负责人: Patricia Ernst
• 金额: $ 20.43万
• 依托单位: UNIVERSITY OF COLORADO DENVER
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-15 至 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8974958
• 关键词: Modeling; hematologic; malignancy; self; renewal

DESCRIPTION (provided by applicant): Epigenetic regulators have recently received increasing attention as participants in pathogenic processes in human disease, as well as exciting new drug targets due to their enzymatic activities. A goal of this proposal is to generate an animal model in which a paradigmatic epigenetic regulator, MLL1, can be modulated to study a wide variety of human diseases in which this broadly-expressed protein plays an important role. This animal model utilizes Flp recombinase-directed integration to introduce an epitope-tagged, full-length MLL1 cDNA into embryonic stem cells in which doxycycline addition induces MLL1 cDNA expression. Roles for MLL1 in T-cell memory, neural stem cell specification, hematopoiesis, autism spectrum/cognitive disorders, Weideman- Steiner syndrome, skin and muscle stem cell function, neuroepithelial and hematologic cancers, vascular and craniofacial development have been established through a variety of individual approaches, however, the animal models to study the disease mechanisms have been lacking. In this proposal, we will generate an animal model that can accelerate discoveries in all of these fields. This model will be utilized by the co-PIs to test two major hypotheses. The proto-oncogene MLL1 is disrupted by chromosomal translocations or amplification in several types of leukemia with particularly poor prognosis. In contrast, loss of MLL1 in the hematopoietic system results in loss of self-renewal and proliferation defects in hematopoietic stem cells (HSCs). Based on our preliminary data, we will test the hypothesis that transient induction of MLL1 protein can enhance self-renewal in fetal and/or adult HSCs in a manner that could be clinically useful. Thus, the functional consequences of increased MLL1 levels will be determined using this model, particularly the effect on self- renewal and differentiation of HSCs. The impact on epigenetic modification of MLL1 target genes instrumental in self-renewal will be also be determined. The discovery of pathways that enhance self-renewal in HSCs may be directly relevant to efforts to treat umbilical cord blood or pluripotent sources of hematopoietic cells for transplantation. The second hypothesis is that chronic, sustained expression of wild-type MLL1 protein will lead to a myelodysplastic syndrome or leukemia. Our preliminary data illustrate that this Flp-mediated strategy using MLL1-fusion oncoproteins is feasible and can yield novel insights not possible with traditional retroviral- mediated MLL1-fusion leukemia models. Currently, there are no animal models in which MLL1 expression can be sustained in a manner that reflects gene amplification, thus no pre-clinical model for testing novel therapeutic strategies that may be effective in acute leukemia harboring MLL1 amplifications. Establishing the sufficiency of sustained MLL1 expression in myelodysplastic syndrome/leukemia will set the stage for testing the role of this epigenetic regulator in conjunction with other common mutations that occur in acute leukemia.

描述（由申请人提供）：表观遗传调节剂最近因参与人类疾病的致病过程而受到越来越多的关注，以及由于其酶促活性而令人兴奋的新药物靶标。该提议的目标是产生 可以调节范式表观遗传调节剂MLL1的动物模型，以研究多种人类疾病，其中这种广泛表达的蛋白质起着重要作用。该动物模型利用FLP重组酶指导的整合来将表位标记的全长MLL1 cDNA引入胚胎干细胞中，其中强力霉素添加诱导MLL1 cDNA表达。 MLL1在T细胞记忆中的作用，神经干细胞的规格，造血，自闭症谱/认知障碍，Weideman-Steiner综合征，皮肤和肌肉干细胞功能，神经上皮和血液学癌症，血管癌，血管和颅面的发展已经通过各种动物模型来建立，这些动物已经建立了各种动物模型。在此提案中，我们将生成一个动物模型，该模型可以在所有这些领域中加速发现。该模型将由Co-Pis利用来检验两个主要假设。原始癌基因MLL1被染色体易位或在预后较差的几种类型的白血病中受到破坏。相反，造血系统中MLL1的损失导致造血干细胞（HSC）中自我更新和增殖缺陷的丧失。根据我们的初步数据，我们将测试以下假设：MLL1蛋白的短暂诱导可以以临床上有用的方式增强胎儿和/或成人HSC的自我更新。因此，将使用该模型确定增加MLL1水平的功能后果，尤其是对HSC自我更新和分化的影响。还将确定对MLL1靶基因在自我更新中的表观遗传修饰的影响。在HSC中增强自我更新的途径的发现可能与治疗造血细胞的脐带血或多能来源的努力直接相关。第二个假设是野生型MLL1蛋白的慢性表达将导致骨髓增生综合征或白血病。我们的初步数据表明，使用MLL1融合癌蛋白的FLP介导的策略是可行的，并且传统的逆转录病毒介导的MLL1融合白血病模型无法产生新的见解。当前，没有动物模型可以以反映基因扩增的方式维持MLL1表达，因此没有用于测试新型治疗策略的临床前模型，这些模型可能在具有MLL1扩增的急性白血病中有效。建立在骨髓增生综合征/白血病中持续的MLL1表达的充分性将为测试该表观遗传调节剂与急性白血病中其他常见突变的作用奠定阶段。