Molecular Targeting of MLL and Associated Factors

描述（由申请人提供）：混合谱系白血病（MLL）基因编码组蛋白甲基转移酶，该酶经常因与不良临床结果相关的人类白血病中的染色体易位而突变。在这项竞争性更新申请中提出的研究提出了这样的假设：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标。 这一假设基于当前颁奖期间的重大发现，这些发现极大地增进了我们对 MLL 白血病分子机制的理解。我们已经证明，menin（一种肿瘤抑制蛋白和 MLL 相关因子）对于 MLL 介导的白血病发生来说是矛盾的。 Menin 作为 MLL 癌蛋白的转录辅助因子发挥作用，通过这种能力，我们证明了它的唯一作用是促进与新发现的 MLL 相关蛋白 LEDGF/p75 的相互作用。后者是一种染色质相关蛋白，具有共激活剂活性，但分子功能未知，以前与白血病和艾滋病毒发病机制有关。 第一个具体目标的研究将在临床前和细胞系转化模型系统中使用生化和遗传方法来表征 MLL 介导的白血病发生所需的 LEDGF/p75 的分子功能。这些研究将确定 LEDGF/p75 假定的甲基赖氨酸识别基序的潜在配体，并确定拮抗它们的相互作用作为分子治疗策略的可行性。 第二个目标的研究将采用遗传和生化技术来确定白血病中染色体易位导致 LEDGF/p75 本身致癌激活的分子机制，并确定其在通过 MLL 和/或 Myc 转录途径介导的白血病发生中的特定作用。 第三个具体目标的研究基于我们对多蛋白复合物 (AEP) 的发现，该复合物包含多个 MLL 融合伴侣和 P-TEFb 转录延伸因子。这种新型复合物由 MLL 癌蛋白的子集与 MLL 白血病细胞中的关键靶基因结合，但其对白血病发生所需的分子贡献尚未完全确定。我们的研究将进一步表征 AEP 复合物、其关键酶活性、其对 MLL 转录调控的总体影响及其在 MLL 介导的白血病发生中的作用。将使用临床前转化模型来探讨针对 AEP 成分的活性或相互作用与 MLL 白血病致病作用的治疗价值。 公共健康相关性：本申请旨在研究导致造血细胞癌症的关键分子过程。高度精细的遗传和生化模型系统将用于研究正常干细胞及其癌性对应物和后代中与癌症相关的途径。更好地了解正常干细胞和癌症干细胞之间的相似性和差异将有助于选择性地针对后者，同时保留前者以实现更有效的治疗。

DESCRIPTION (provided by applicant):The Mixed Lineage Leukemia (MLL) gene codes for a histone methyltransferase that is frequently mutated by chromosomal translocations in human leukemias associated with a poor clinical outcome. The studies proposed in this competitive renewal 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 major discoveries during the current award period that have substantially advanced our understanding of the molecular mechanisms of MLL leukemias. We have shown that menin, a tumor suppressor protein and MLL- associated factor, is paradoxically required for MLL-mediated leukemogenesis. Menin functions as a transcriptional co-factor for MLL oncoproteins, and in this capacity we demonstrated that its only role is to promote interactions with a newly discovered MLL- associated protein known as LEDGF/p75. The latter is a chromatin-associated protein with co-activator activity but unknown molecular function, previously implicated in leukemia and HIV pathogenesis. Studies in the first specific aim will characterize the molecular functions of LEDGF/p75 required for MLL-mediated leukemogenesis using biochemical and genetic approaches in pre-clinical and cell line transformation model systems. These studies will identify a potential ligand for the putative methyl-lysine recognition motif of LEDGF/p75 and also establish the feasibility of antagonizing their interactions as a molecular therapeutic strategy. Studies in the second aim will employ genetic and biochemical techniques to determine the molecular mechanisms that underlie oncogenic activation of LEDGF/p75 itself by chromosomal translocations in leukemias, and establish its specific roles in leukemogenesis mediated through the MLL and/or Myc transcriptional pathways. Studies in the third specific aim are based on our discovery of a multi-protein complex (AEP) that contains several MLL fusion partners and the P-TEFb transcription elongation factor. This novel complex is tethered by a subset of MLL oncoproteins to critical target genes in MLL leukemia cells, however its molecular contributions required for leukemogenesis have not been fully defined. Our studies will further characterize the AEP complex, its critical enzymatic activities, its implications for MLL transcriptional regulation in general, and its role in MLL-mediated leukemogenesis. The therapeutic value of targeting the activities or interactions of AEP components with pathogenic roles in MLL leukemia will be interrogated using preclinical transformation models. PUBLIC HEALTH RELEVANCE: This application proposes to investigate the critical molecular processes that cause cancers of blood-forming cells. Highly refined genetic and biochemical model systems will be employed to study cancer-associated pathways in normal stem cells as well as their cancerous counterparts and progeny. A greater understanding of the similarities and differences among normal and cancer stem cells will facilitate efforts to selectively target the latter while sparing the former to achieve more efficacious therapies.