Dissecting and targeting canonical and non-canonical oncogenic functions of EZH2 in cancer

项目摘要/摘要 携带MLL1重排的白血病患者通常表现出非常差的预后，需要新的 治疗策略。多项独立研究已确定EZH2，一种组蛋白甲基转移酶和 多梳抑制复合体2的催化亚基作为MLL1重排的诱人药物靶点 白血病。然而，目前EZH2的催化抑制剂抗肿瘤作用有限。我们的预赛 研究表明，EZH2还与c-myc结合，并在癌基因(如 在MLL1重排的白血病中，它不同于众所周知的PRC2：EZH2驱动的规范 与基因抑制相关的功能。为了同时针对规范和非规范致癌作用，通过 EZH2，我们利用蛋白质水解靶向嵌合体(PROTAC)技术产生了新型的EZH2小分子- 分子降解剂包括MS177。我们广泛的初步研究表明，MS177 有效地降低PRC2：EZH2和EZH2的非PRC2合作伙伴(例如，将EZH2绑定到 激活癌基因)，从而抑制EZH2的典型和非典型致癌活性 肿瘤。重要的是，我们的初步结果还表明，MS177优于所有的酶抑制剂 EZH2治疗MLL1重排白血病因此，我们假设：(1)EZH2具有一个较少研究的、非 规范致癌功能，与PRC2并行作用：依赖于EZH2的功能产生更多 MLL1重排白血病中的侵袭性肿瘤表型；以及(2)针对典型和非典型性白血病 PROTACs对EZH2的规范活性代表了一种新的、优越的治疗策略 鄂州医科大学硕士学位论文S单独酶活。EZH2介导的肿瘤发生和发展机制的剖析 作为候选药物的最佳EZH2 PROTAC的开发将对改进 MLL1重排白血病患者的治疗。为了实现这一目标，我们将进一步表征这样一个新的 EZH2在MLL1重排白血病中的非典型致癌作用(目标1a)及确定EZH2的作用 抑制EZH2的典型和非典型致癌活性的PROTAC(目标1b)。我们会 用多个独立的方法测定EZH2 PROTACs的体内外治疗效果 包括人/鼠癌细胞和患者来源的异种移植(PDX)的MLL1重排白血病模型 (目标2)。最后，我们将优化我们的EZH2 PROTAC线索，使其成为候选药物(目标3)。已完成的 拟议中的研究不仅将为MLL1重排白血病如何发生提供新的机制理解 开发，但也将验证创新的治疗策略并提供有前景的候选治疗方案 用于治疗受影响的癌症患者。

PROJECT SUMMARY/ABSTRACT Leukemia patients bearing MLL1 rearrangement generally display very poor prognosis, demanding new treatment strategies. Multiple independent studies have identified EZH2, a histone methyltransferase and catalytic subunit of Polycomb Repressive Complex 2 (PRC2), as an attractive drug target in MLL1-rearranged leukemias. However, the current catalytic inhibitors of EZH2 have limited anti-tumor effect. Our preliminary studies show that EZH2 also binds c-MYC and has a non-canonical function in activation of oncogenes (such as Cyclin E1) in MLL1-rearranged leukemias, which differs from the well-known PRC2:EZH2-driven canonical function related to gene repression. In order to target both canonical and non-canonical oncogenic actions by EZH2, we used the Proteolysis Targeting Chimera (PROTAC) technology to generate novel EZH2 small- molecule degraders including MS177. Our extensive preliminary studies have demonstrated that MS177 effectively degrades both PRC2:EZH2 and non-PRC2 partners of EZH2 (e.g., c-MYC, which binds EZH2 to activate oncogenes), thus suppressing both canonical and non-canonical oncogenic activities of EZH2 in tumor. Importantly, our preliminary results also show that MS177 is superior to all of enzymatic inhibitors of EZH2 in treating MLL1-rearranged leukemias. Thus, we hypothesize that: (1) EZH2 has a less-studied, non- canonical oncogenic function, which acts in parallel with the PRC2:EZH2-dependent one to produce more aggressive tumor phenotypes seen in MLL1-rearranged leukemias; and (2) targeting both canonical and non- canonical activities of EZH2 by PROTACs represents a novel and superior therapeutic strategy to inhibition of EZH2’s enzymatic activity alone. Dissection of the mechanisms underlying EZH2-mediated oncogenesis and development of an optimal EZH2 PROTAC as a drug candidate will have significant impact on improving treatments for MLL1-rearranged leukemia patients. Towards this goal, we will further characterize such a new non-canonical oncogenic role of EZH2 in MLL1-rearranged leukemias (Aim 1a) and define effects of EZH2 PROTACs on suppressing both canonical and non-canonical oncogenic activities of EZH2 (Aim 1b). We will also determine in vitro and vivo therapeutic effects of EZH2 PROTACs by employing multiple independent MLL1-rearranged leukemia models including human/murine cancer cells and patient-derived xenografts (PDX) (Aim 2). Lastly, we will optimize our EZH2 PROTAC leads into a drug candidate (Aim 3). Completion of the proposed research will not only provide novel mechanistic understanding of how MLL1-rearranged leukemias develop, but will also validate an innovative therapeutic strategy and deliver a promising therapeutic candidate for the treatment of affected cancer patients.