SIRT5 inhibitors and degraders as novel treatments for Ewing sarcoma

摘要 摘要尤文肉瘤是一种发生在儿童和青少年的软组织和骨组织中的侵袭性肿瘤。 成年人。EWS的治疗方法包括细胞毒性化疗、局部放射治疗和/或手术治疗。 局限性疾病患者的总体存活率较好。然而，仍有一个紧迫的问题 需要新的治疗方法来治疗EWS。转移性或复发性EWS患者有非常多的 预后不良。此外，目前的EWS治疗与许多短期和长期的 后遗症，例如加速的心血管疾病和继发性癌症。EWS-FLI1是融合 癌蛋白存在于大多数EWS病例中。它作为先锋转录因子发挥作用，影响 许多靶基因的表达。异常的EWS转录组代表了一种潜在的治疗方法 EWS中的目标。这项建议将sirtuin SIRT5作为治疗EWS的新靶点。SIRT5 在整个细胞中都存在，并通过负性移除来调节不同途径中的蛋白质靶标 对赖氨酸残基进行带电修饰，包括琥珀酸化。尽管正常的细胞类型和整体 小鼠耐受具有最低表型的SIRT5丢失，我们发现特定的癌症，特别是 包括EWS在内，都非常依赖于SIRT5，并在SIRT5之后迅速经历细胞凋亡 耗尽。我们已经将这种效应与SIRT5在核组蛋白脱琥珀酸化中的作用联系起来，从而 调控EWS中的基因表达。我们和其他人已经证明，SIRT5原则上服从于 用小分子选择性抑制或降解。我们的长期目标是将SIRT5评估为 EWS的潜在治疗靶点。这项提议的目标是产生新的生物学见解。 SIRT5在EWS中的功能，并表征SIRT5抑制剂和基于SIRT5 PROTAC的降解物。 这一应用的中心假设是：1)SIRT5是EWS细胞通过组蛋白生存所必需的 脱琥珀酸化和基因表达的调节；以及2)SIRT5抑制剂和降解物将代表 用于研究SIRT5生物学的有用工具化合物，以及未来潜在EWS的起点 治疗学。这个应用程序基本原理是EWS Cells对SIRT5表现出极大的脆弱性 功能丧失，而其他类型的细胞和整个小鼠没有表现出重大的不良影响。因此，SIRT5抑制 在临床上可能耐受性良好。这项工作将在两个具体目标的背景下进行。第一, 我们将使用MASS来阐明SIRT5和KSucc对组蛋白和基因表达的影响 光谱以及转录组和表观基因组学方法。第二，我们将优化和优化 使用药物化学方法验证SIRT5抑制剂和降解剂，部分基于 SIRT5-抑制物共晶结构。该应用程序具有创新性，因为目前还没有发布数据 将SIRT5与EWS联系起来，目前还没有有效和选择性的SIRT5抑制剂或PROTAC 描述。这项工作意义重大，因为对改善EWS治疗的临床需求尚未得到满足。

Abstract Ewing sarcoma (EWS) is an aggressive tumor arising in soft tissue and bone of children and young adults. EWS is treated with a combination of cytotoxic chemotherapy, local radiation, and/or surgery. Patients with localized disease show a favorable overall survival rate. However, there is still a pressing need for new therapeutic approaches for EWS. Patients with metastatic or recurrent EWS have a very poor prognosis. Moreover, current EWS treatments are associated with many short- and long-term sequelae, e.g. accelerated cardiovascular disease and secondary cancers. EWS-FLI1 is the fusion oncoprotein present in most cases of EWS. It functions as a pioneer transcription factor to affect expression of many target genes. The aberrant EWS transcriptome represents a potential therapeutic target in EWS. This proposal focuses on the sirtuin SIRT5 as a novel therapeutic target in EWS. SIRT5 is found throughout the cell, and regulates protein targets in diverse pathways by removing negatively charged modifications on lysine residues, including succinylation. Although normal cell types and whole mice tolerate loss of SIRT5 with minimal phenotypes, we have found that specific cancers, notably including EWS, are exquisitely dependent on SIRT5, and rapidly undergo apoptosis following SIRT5 depletion. We have linked this effect to a role for SIRT5 in desuccinylating nuclear histones, thereby modulating gene expression in EWS. We and others have shown that SIRT5 is in principle amenable to selective inhibition or degradation with small molecules. Our long-term goal is to evaluate SIRT5 as a potential therapeutic target for EWS. The objective of this proposal is to generate new biological insights into SIRT5 function in EWS, and characterize SIRT5 inhibitors and SIRT5 PROTAC-based degraders. The central hypotheses of this application are that: 1) SIRT5 is required for EWS cell survival via histone desuccinylation and regulation of gene expression; and 2) SIRT5 inhibitors and degraders will represent useful tool compounds to interrogate SIRT5 biology, and a starting point for potential future EWS therapeutics. The rationale for this application is that EWS cells show exquisite vulnerability to SIRT5 loss-of-function, while other cell types and whole mice show no major ill effects. Hence, SIRT5 inhibition would likely be well tolerated clinically. The work will take place in the context of two Specific Aims. First, we will elucidate the impact of SIRT5 and Ksucc on histones and gene expression, using mass spectrometry along with transcriptomic and epigenomic approaches. Second, we will optimize and validate SIRT5 inhibitors and degraders, using medicinal chemistry approaches and based in part on SIRT5-inhibitor co-crystal structures. The application is innovative, in that no published data currently link SIRT5 to EWS, and no potent and selective SIRT5 inhibitors or PROTACs have as yet been described. The work is significant, since there is an unmet clinical need for improved therapies for EWS.