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由于白血病干细胞的活性所致。 (LSCS)。白血病干细胞是一种罕见的能够自我更新的细胞群， 增殖和分化为恶性母细胞。LSC对化疗的抵抗力要强得多， 与祖细胞或原始细胞相比，辐射和针对LSCs的新药理药物是迫切需要的 需要的。多梳抑制复合体1(Prc1)是一种组蛋白H_2A_E3泛素连接酶，具有广泛的生物学活性。 在干细胞种群分化和维持的调节中起着既定的作用。Prc1催化 赖氨酸119通过异二聚体环1b-Bmi1 E3在组蛋白H_2A(H_2AK_119ub)上的单烯基化反应 连接酶。在这个项目中，我们建议开发Ring1b-Bmi1 E3连接酶的小分子抑制剂作为新的 针对白血病干细胞的药理制剂。 由于缺乏明确的定义，用小分子靶向Ring E3连接酶是一项非常具有挑战性的任务 衬底捆绑袋。我们通过使用片段识别与Ring1b-Bmi1结合的小分子。 基于核磁共振波谱的筛选。然后，我们进行了广泛的药物化学优化 这些化合物极大地提高了它们的结合亲和力，从而产生了低微摩尔的抑制剂 细胞中的过氧化氢泛素化。Ring1b-Bmi1抑制剂阻断集落对模型LSC细胞的作用 形成并诱导这些细胞分化。在这个项目中，我们假设强大的Ring1b-Bmi1 抑制剂将损害白血病干细胞的自我更新，并将在体内阻止白血病的发展。 为了实现这一目标，我们建议开发更有效的Ring1b-Bmi1 E3连接酶活性抑制剂 优化了适合体内研究的类药物特性。我们将使用药物化学和结构- 基于设计方法优化Ring1b-Bmi1抑制剂。我们将广泛评估这一机制。 Ring1b-Bmi1抑制剂在模型LSC细胞系和原发患者样本中的作用。这个 优化后的化合物将在体内进行评估，以确定其阻止白血病发展的潜力。我们的研究 将探索一种新的靶向白血病干细胞的方法，并可能导致极具发展价值的 治疗急性白血病的化学探针化合物或新型药理制剂。

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.