Development of small molecules targeting Ring1B-Bmi1 E3 ligase in leukemia

项目摘要 新的证据表明，急性白血病的复发是白血病干细胞活性的结果 （LSC）。白血病干细胞代表了一种罕见的细胞群体，它们能够自我更新， 增殖并分化为恶性母细胞。LSC对化疗更有抵抗力， 当与祖细胞或胚细胞相比时， needed. Polycomb Repressive Complex 1（PRC 1）是一种组蛋白H2 A E3泛素连接酶， 在调节干细胞群的分化和维持方面发挥着既定的作用。PRC 1催化 通过异源二聚体Ring 1B-Bmi 1 E3在组蛋白H2 A（H2 AK 119 ub）处的赖氨酸119的单二酰化 连接酶在这个项目中，我们建议开发Ring 1B-Bmi 1 E3连接酶的小分子抑制剂， 靶向白血病干细胞的药物。 用小分子靶向环E3连接酶是一项非常具有挑战性的任务，这是由于缺乏明确的靶向酶。 基质结合袋。我们通过使用片段- 基于NMR光谱的筛选。然后，我们进行了广泛的药物化学优化， 这些化合物大大提高了它们的结合亲和力，导致低微摩尔的 细胞中的H2 A泛素化。用Ring 1B-Bmi 1抑制剂处理模型LSC细胞系阻断集落 形成并诱导这些细胞的分化。在这个项目中，我们假设有效的Ring 1B-Bmi 1 抑制剂将损害白血病干细胞的自我更新，并将阻断白血病在体内的发展。 为了实现这一目标，我们建议开发更有效的Ring 1B-Bmi 1 E3连接酶活性抑制剂， 优化的药物样性质适合于体内研究。我们会用药物化学和结构- 的设计方法来优化Ring 1B-Bmi 1抑制剂。我们将广泛评估 Ring 1B-Bmi 1抑制剂在模型LSC细胞系和原代患者样品中的作用。的 将在体内评价优化的化合物阻断白血病发展的潜力。我们的研究 将探索一种靶向白血病干细胞的新方法，并可能导致开发高价值的 用于急性白血病的化学探针化合物或新的药理学试剂。

Project Summary Emerging evidence shows that recurrence of the acute leukemia results from the activity of leukemia stem cells (LSCs). Leukemic stem cells represent a rare population of cells, which are capable of self-renewal, proliferation and differentiation into malignant blasts. LSCs are much more resistant to chemotherapy and radiation when compared to progenitors or blasts and new pharmacological agents targeting LSCs are urgently needed. Polycomb Repressive Complex 1 (PRC1) is a histone H2A E3 ubiquitin ligase and has a well- established role in the regulation of differentiation and maintenance of stem cell populations. PRC1 catalyzes the monoubiquitylation of lysine 119 at histone H2A (H2AK119ub) through heterodimeric Ring1B-Bmi1 E3 ligase. In this project we propose to develop small molecule inhibitors of the Ring1B-Bmi1 E3 ligase as new pharmacologic agents targeting leukemia stem cells. Targeting the Ring E3 ligases with small molecules is a very challenging task due to the lack of well-defined substrate binding pockets. We identified small molecules that bind to Ring1B-Bmi1 by employing fragment- based screening using NMR spectroscopy. We then performed extensive medicinal chemistry optimization of these compounds and very substantially improved their binding affinity, resulting in low micromolar inhibitors of the H2A ubiquitination in cells. Treatment of model LSC cell lines with Ring1B-Bmi1 inhibitors blocks colony formation and induces differentiation of these cells. In this project we hypothesize that potent Ring1B-Bmi1 inhibitors will impair self-renewal of leukemia stem cells and will block development of leukemia in vivo. Towards this goal, we propose to develop more potent inhibitors of the Ring1B-Bmi1 E3 ligase activity with optimized drug-like properties suitable for in vivo studies. We will employ medicinal chemistry and structure- based design approach to optimize Ring1B-Bmi1 inhibitors. We will extensively evaluate the mechanism of action of the Ring1B-Bmi1 inhibitors in the model LSC cell lines and in the primary patient samples. The optimized compounds will be assessed in vivo for their potential to block development of leukemia. Our studies will explore a new approach to target leukemia stem cells and may lead to development of highly valuable chemical probe compounds or novel pharmacologic agents for acute leukemia.