Development of Inhibitors of the Leukemia Fusion Protein CBFbeta-SMMHC

描述（由申请人提供）：编码CBF 2（CBFB）的基因被16号染色体倒位[inv（16）（p13 q22）]破坏，与约12%的人类急性髓性白血病相关，导致融合蛋白含有与平滑肌肌球蛋白重链（SMMHC）卷曲螺旋尾区融合的大部分CBF 2。CBF 2- SMMHC融合蛋白作为CBF功能的显性阻遏物，结合RUNX 1并失调正常造血所需的多个基因的表达。目前使用细胞毒性化疗的治疗导致45-65%的五年总生存率，但对于60岁以上的患者仅为20%。这些数据清楚地表明，可以改善inv（16）AML患者治疗反应的靶向治疗是必不可少的。新出现的文献表明，目前的疗法无法治愈癌症可能归因于所谓的癌症干细胞或癌症起始细胞的群体，这些细胞具有长期自我更新潜力，并且可以在复发时完全重现肿瘤表型。我们的假设是，抑制CBF 2-SMMHC与RUNX 1的Runt结构域相互作用的小分子可能是诱导凋亡和/或分化并根除白血病起始细胞群的有效治疗药物，从而实现更好的长期存活。 我们已经确定了抑制CBF 2-SMMHC和RUNX 1之间蛋白质-蛋白质相互作用的初始先导物。我们建议使用基于结构的药物设计和药物化学方法进一步优化这种先导化合物的效力。将测试化合物缓解CBF 2-SMMHC介导的抑制和影响白血病细胞系的生长、凋亡和分化的能力。将在充分表征的inv（16）白血病小鼠模型中对选定的化合物进行体内试验。 抑制CBF 2和CBF 2-SMMHC功能两者（如目的1中提出的抑制剂）可能会导致毒性或缺乏功效，因此我们提出开发对CBF 2-SMMHC的选择性超过CBF 2的小分子抑制剂。将测试化合物缓解CBF 2-SMMHC介导的抑制和影响白血病细胞系的生长、凋亡和分化的能力。将在充分表征的inv（16）白血病小鼠模型中对选定的化合物进行体内试验。 我们假设有效的抑制剂应该特异性地影响表达CBF 2-SMMHC的前白血病祖细胞的分化和细胞死亡，而骨髓中的正常干细胞和早期祖细胞的改变最小。我们建议研究所选化合物在正常造血中的体内作用。将优先考虑对正常造血作用具有最小影响或无影响的化合物，以研究其对表达CBF 2-SMMHC的敲入小鼠中白血病前祖细胞减少/根除的影响。 公共卫生相关性：我们建议开发融合蛋白CBF 2- SMMHC的小分子抑制剂，该融合蛋白是一种类型的急性髓系白血病（AML）的致病剂。这种靶向抑制剂具有通过消除导致复发发生的白血病细胞群体来改善患有这种白血病的患者的长期存活的潜力。这些抑制剂也有可能比标准化疗毒性更小，从而减少治疗的副作用。

DESCRIPTION (provided by applicant): The gene encoding CBF2 (CBFB) is disrupted by the chromosome 16 inversion [inv(16)(p13q22)], associated with ~12% of acute myeloid leukemia in humans, resulting in a fusion protein containing most of the CBF2 fused to the coiled-coil tail region of smooth muscle myosin heavy chain (SMMHC). The CBF2- SMMHC fusion protein acts as a dominant repressor of CBF function, binding RUNX1 and dysregulating the expression of multiple genes required for normal hematopoiesis. Current treatment utilizing cytotoxic chemotherapy results in 45-65% five year overall survival but only 20% for patients older than 60. These data clearly indicate that targeted therapies that can improve the therapeutic response for inv(16) AML patients is essential. Emerging literature suggests that inability to cure cancers with current therapies may be attributed to a population of so-called cancer stem cells or cancer initiating cells that have long term self-renewal potential and can fully recapitulate tumor phenotype at time of relapse. Our hypothesis is that small molecules that inhibit the interaction of CBF2-SMMHC with the Runt domain of RUNX1 could be effective therapeutic drugs that induce apoptosis and/or differentiation and eradicate the leukemia initiating cell population, thereby achieving better long term survival. We have identified an initial lead that inhibits the protein-protein interaction between CBF2-SMMHC and RUNX1. We are proposing to further optimize the potency of this lead using structure-based drug design and medicinal chemistry approaches. Compounds will be tested for their ability to relieve CBF2-SMMHC mediated repression and affect the growth, apoptosis, and differentiation of leukemia cell lines. Selected compounds will be tested in vivo in a well-characterized mouse model of inv(16) leukemia. It is possible that inhibiting both CBF2 and CBF2-SMMHC function, as the inhibitors proposed in Aim 1 will do, could result in toxicity or a lack of efficacy, therefore we are proposing to develop small molecule inhibitors which are selective for CBF2-SMMHC over CBF2. Compounds will be tested for their ability to relieve CBF2-SMMHC mediated repression and affect the growth, apoptosis, and differentiation of leukemia cell lines. Selected compounds will be tested in vivo in a well-characterized mouse model of inv(16) leukemia. We hypothesize that effective inhibitors should specifically affect differentiation and cell death of pre- leukemic progenitor cells expressing CBF2-SMMHC with minimal alteration of the normal stem and early progenitor cells in the bone marrow. We propose to study the effect of selected compounds in vivo in normal hematopoiesis. Compounds with minimal or no effect on normal hematopoiesis will be prioritized to study their effect on the reduction/eradication of pre-leukemic progenitors in knock-in mice expressing CBF2-SMMHC. PUBLIC HEALTH RELEVANCE: We are proposing to develop small molecule inhibitors of the fusion protein CBF2- SMMHC which is a causative agent in one type of acute myeloid leukemia (AML). Such targeted inhibitors have the potential to improve the long term survival of patients with this leukemia by eliminating the population of leukemia cells which cause relapse to occur. These inhibitors also have the potential to be less toxic than standard chemotherapy, resulting in reduced side effects from treatment.