EZH2 in cancer biology and novel inhibitors

Zest2的增强子(EZH2)，多梳抑制复合体2的组蛋白甲基转移酶亚单位 (PrC2)，催化组蛋白3(H3K27)上赖氨酸残基27的甲基化。H3K27甲基化抑制 通过阻止基因激活所必需的蛋白质的募集来转录邻近的基因。这个 PRC2复合体及其调控的组蛋白修饰在正常细胞中受到严格控制，但可以 在癌症中变得失调，以异常地激活或抑制基因表达。在过去的十年里，许多人 独立研究证实，EZH2在许多癌症和复发的肿瘤中高度表达 在其他几个基因中发生了突变。EZH2的过度表达与侵袭性进展和不良相关 预后。我们最近证实，EZH2的过度表达是导致肺腺癌的原因。 老鼠。同样，激活EZH2的体细胞突变在B细胞淋巴瘤和恶性肿瘤中也被发现 黑色素瘤。我们建立了小鼠模型来表达EZH2的功能获得突变体在B细胞或 黑素细胞，分别导致高外显性淋巴瘤或黑色素瘤。我们对小白鼠的研究 表达EZH2功能获得突变体的模型表明，EZH2 Y641F诱导淋巴瘤和 黑色素瘤通过大量的染色质结构重组诱导抑制和激活 PrC2调控的基因座。将EZH2活性与癌症联系起来的广泛证据引发了人们对 潜在的生物学机制，包括与肿瘤免疫环境的联系。 因此，我们开发了一种新型的EZH2小分子抑制剂JQEZ5，它可以有效地阻断酶 野生型和突变型EZH2的功能，并减少H3K27的甲基化。黄连蛋白的抑制活性 JQEZ5抑制培养的癌细胞以及肺癌、淋巴瘤和小鼠模型中癌细胞的生长 黑色素瘤。从机制上讲，JQEZ5是一种非共价抑制剂，它竞争天然辅助因子S-腺苷 蛋氨酸(SAM)与EZH2结合。目前所有EZH2抑制剂的SAM竞争性很大程度上 限制了它们在体内的效力，这可能会限制它们在癌症治疗中的使用。 为了提高EZH2抑制剂的体内疗效并减少靶外毒性，我们建议开发和 一类可与独特半胱氨酸残基(C663)不可逆结合的新型共价EZH2抑制剂的表征 存在于人和小鼠的EZH2中。我们假设这种新型抑制剂的不可逆结合可以 克服现有非共价抑制剂的关键限制，提高体内效力和选择性。我们 将使用新的共价EZH2抑制剂来进一步研究EZH2抑制肺内的肿瘤生物学 癌症，包括抑制EZH2的免疫调节作用。我们将利用我们的细胞培养和小鼠 探讨EZH2不可逆抑制对EZH2基因表达和基因表达的影响 推动共价EZH2抑制剂的点击到领先优化的肿瘤免疫微环境 促使临床研究充分发掘EZH2抑制剂的翻译潜力。

Enhancer of zeste 2 (EZH2), a histone methyl transferase subunit of the Polycomb Repressive Complex 2 (PRC2), catalyzes the methylation of lysine residue 27 on histone 3 (H3K27). Methylation of H3K27 inhibits the transcription of nearby genes by blocking the recruitment of the proteins necessary for gene activation. The PRC2 complex and the histone modifications that it regulates are tightly controlled in normal cells but can become dysregulated in cancer to aberrantly activate or repress gene expression. Over the last decade, many independent studies have established that EZH2 is highly expressed in numerous cancers and recurrently mutated in several others. Overexpression of EZH2 is associated with aggressive progression and poor prognosis. We recently demonstrated that overexpression of EZH2 is causative of lung adenocarcinoma in mice. Likewise, activating somatic mutations of EZH2 have been identified in B cell lymphoma and malignant melanoma. We developed mouse models to express the gain-of-function mutant of EZH2 in B cells or melanocytes, which caused high-penetrance lymphoma or melanoma, respectively. Our studies with mouse models that express the gain-of-function mutant of EZH2 suggest that EZH2Y641F induces lymphoma and melanoma through a vast reorganization of chromatin structure inducing both repression and activation of PRC2-regulated loci. The extensive evidence linking EZH2 activity to cancer has prompted interest in the underlying biological mechanisms, including the link to the tumor immune environment. As such, we developed a novel EZH2 small molecule inhibitor, JQEZ5, that can efficiently block the enzymatic function of both wild-type and mutant EZH2 and reduce the methylation of H3K27. The inhibitory activity of JQEZ5 impedes the growth of cancer cells in culture and in mouse models of lung cancer, lymphoma and melanoma. Mechanistically, JQEZ5 is a non-covalent inhibitor that competes off natural co-factor S-adenosine methionine (SAM) from binding with EZH2. The SAM-competitive nature of all current EZH2 inhibitors largely limited their in vivo potency, which could potentially limit their usage in cancer therapy. To improve the in vivo efficacy of EZH2 inhibitors and reduce off-target toxicity, we propose to develop and characterize a new class of covalent EZH2 inhibitors that can irreversibly bind to unique cysteine residue (C663) present in human and mouse EZH2. We hypothesize that the irreversible biding of this new class inhibitors can overcome key limitations of the existing non-covalent inhibitors, and improve in vivo potency and selectivity. We will employ the new covalent EZH2 inhibitors to further investigate cancer biology of EZH2 inhibition in lung cancer, including the immunomodulatory effects of EZH2 inhibition. We will utilize our cell culture and mouse models of EZH2-driven cancer to explore the impact of irreversible inhibition of EZH2 on gene expression and the tumor immune microenvironment while driving hit-to-lead optimization of covalent EZH2 inhibitors that can prompt clinical investigation to fully explore the translational potential of EZH2 inhibitors.