Molecular Targeting of MLL and Associated Factors

描述(由申请人提供)：混合血统白血病(MLL)基因编码一种组蛋白甲基酶，在人类白血病中，该甲基酶经常因染色体易位而突变，临床结果较差。本申请中提出的研究解决了一种假设，即MLL癌蛋白的致白血病作用严重依赖于最近发现的与MLL或其融合伙伴相关的蛋白质，并且这些相关因子的活性或相互作用构成了分子治疗的潜在靶点。这一假说是基于大量的初步研究，这些研究已经导致了含有MLL或其主要融合伙伴的多蛋白复合体的纯化，并鉴定了与野生型和/或突变型MLL蛋白相关的蛋白质。 最近发现的MLL相关蛋白之一是MEN1肿瘤抑制基因的产物Menin。Menin是MLL复合体的重要组成部分，是维持HOX基因表达所必需的，也与致癌的MLL融合蛋白相互作用。第一个特定目标的研究将确定薄荷素在临床前和细胞系转化模型系统中使用遗传学方法启动和维持MLL介导的白血病发生中的作用。这些研究还将确立以MLL-薄荷素相互作用为靶点作为分子治疗策略的可行性。 第二个目标的研究将利用遗传和生化方法来确定与MLL转化关键域相互作用的其他未知因素，确定它们在白血病发生中的特定作用，并确定它们作为分子治疗靶点的可行性。第三个特定目标的研究是基于我们发现的AF4多蛋白质复合体，其中包含MLL融合伙伴ENL等蛋白质。这一新的复合体将MLL融合伙伴的两个主要家族连接在一个共同的生化途径上。这些观察结果将通过进一步表征AF4/ENL途径的分子性质，确定其对转录调控的一般意义，并确定其在MLL介导的白血病发生中的作用，来扩展这些观察。针对在MLL白血病中具有致病作用的AF4复杂成分的活性或相互作用的治疗价值将使用临床前转化模型进行询问。

DESCRIPTION (provided by applicant): The Mixed Lineage Leukemia (MLL) gene codes for a histone methylase, which is frequently mutated by chromosomal translocations in human leukemias associated with a poor clinical outcome. The studies proposed in this application address the hypothesis that the leukemogenic actions of MLL oncoproteins are critically dependent on proteins recently discovered to associate with MLL or its fusion partners, and that the activities or interactions of these associated factors constitute potential targets for molecular therapies. This hypothesis is based on substantial preliminary studies that have resulted in the purification of multi-protein complexes containing MLL or its major fusion partners, and identification of proteins that associate with wild type and/or mutant MLL proteins. One of the recently identified MLL-associated proteins is menin, a product of the MEN1 tumor suppressor gene. Menin is an essential component of the MLL complex, is required for maintenance of Hox gene expression, and also interacts with oncogenic MLL fusion proteins. Studies in the first specific aim will determine the role of menin in the initiation and maintenance of MLL-mediated leukemogenesis using genetic approaches in pre-clinical and cell line transformation model systems. These studies will also establish the feasibility of targeting MLL-menin interactions as a molecular therapeutic strategy. Studies in the second aim will employ genetic and biochemical approaches to identify additional unknown factors that interact with transformation critical domains of MLL, establish their specific roles in leukemogenesis, and determine their feasibility as molecular therapeutic targets. Studies in the third specific aim are based on our discovery of an AF4 multi-protein complex that contains among other proteins the MLL fusion partner ENL. This novel complex links the two major families of MLL fusion partners on a common biochemical pathway. These observations will be extended by further characterizing the molecular nature of the AF4/ENL pathway, determining its implications for transcriptional regulation in general, and establishing its role in MLL-mediated leukemogenesis. The therapeutic value of targeting the activities or interactions of AF4 complex components with pathogenic roles in MLL leukemias will be interrogated using preclinical transformation models.