Targeting Deubiquitylating Enzymes in Multiple Myeloma

项目总结(见说明)： 正常的细胞动态平衡是通过蛋白质合成和降解的平衡调节来维持的。泛素蛋白酶体系统(UPS)是一种由蛋白酶体全酶、泛素连接酶和脱泛素化酶(DUBS)介导的非溶酶体细胞内蛋白质降解途径。 UPS通路的失控与包括多发性骨髓瘤(MM)在内的多种人类疾病的发病机制有关；因此，UPS通路的抑制剂，无论是在蛋白酶体水平还是泛素化/去泛素化酶水平，都有望成为一种新的治疗策略。在我们的第一个资助期，我们使用我们在骨髓环境中的MM细胞的体外和体内模型，在蛋白酶体水平上表征了多发性骨髓瘤中UPS的靶向性。我们特别阐明了蛋白酶体抑制剂靶向肿瘤细胞、宿主肿瘤相互作用和骨髓微环境克服耐药性的分子和细胞机制。我们的临床前和临床研究导致FDA批准Bortezomib用于复发/难治性和新诊断的MM。虽然Bortezomib是一个重大进步，但并不是所有患者都有反应，那些有反应的患者会复发。因此，我们最近的研究已经确定了蛋白酶体抑制剂的耐药机制和克服它的策略。这项工作一方面导致了第二代蛋白酶体抑制剂，另一方面导致了科学知情的联合疗法，导致了多个正在进行的第三阶段临床试验。我们最近的工作重点是发现和开发UPS的另一个主要组成部分DUBS的小分子抑制剂。我们的初步研究表明，与正常浆细胞相比，Dub USP7在MM细胞中的表达和活性增加，并且它的抑制甚至在对Bortezomib耐药的MM细胞中也会触发细胞凋亡。目前的建议旨在研究一种假说，即在蛋白酶体上游的DUBS水平上抑制UPS可以抑制MM细胞的生长，并克服蛋白酶体抑制剂的耐药性。为了实现这些目标，我们将追求以下具体目标：具体目标1：确定去泛素化酶(DUBS)在MM细胞生长、存活和耐药中的作用。具体目标2：开发选择性DUB抑制剂，并确定其单独或与抗MM药物联合的体外作用机制。 具体目标3：进行DUB抑制剂的临床前体内研究和临床试验，无论是单独还是联合治疗复发的难治性MM。这种在蛋白酶体或去泛素化酶水平针对MM中UPS通路的新范式，不仅有望改变MM的自然历史，而且可以作为其他癌症的靶向治疗的模型。

PROJECT SUMMARY (See instructions): Normal cellular homeostasis is maintained by a balanced regulation of protein synthesis and degradation. The ubiquitin proteasome system (UPS) is a non-lysosomal intracellular protein degradation pathway mediated via proteasome holoenzymes, ubiquitin ligases, and deubiquitylating enzymes (DUBs). Deregulation of the UPS pathway is linked to the pathogenesis of various human diseases including multiple myeloma (MM); therefore, inhibitors of UPS pathways, either at the level of proteasomal or ubiquitylating/deubiquitylating enzymes, offers great promise as a novel therapeutic strategy. In our first funding period, we characterized targeting of UPS in MM at the level of the proteasome using our in vitro and in vivo models of the MM cell in the BM milieu. We specifically elucidated the molecular and cellular mechanisms whereby proteasome inhibitors target tumor cells, host tumor interactions, and the BM microenvironment to overcome drug resistance. Our preclinical and clinical studies led to the FDA approval of Bortezomib for relapsed/refractory and newly diagnosed MM. Although Bortezomib represents a major advance, not all patients respond, and those that respond relapse. Therefore our more recent studies have defined mechanisms of resistance to proteasome inhibitors and strategies to overcome it. This work has led to second-generation proteasome inhibitors on the one hand, and scientifically-informed combination therapies on the other, leading to multiple ongoing phase III clinical trials. Our recent efforts have focused on discovery and development of small molecule inhibitors of another major component of UPS, DUBs. Our Preliminary Studies show increased expression and activity of the DUB USP7 in MM cells versus normal plasma cells, and that its inhibition triggers apoptosis even in Bortezomib resistant MM cells. The current proposal aims to investigate the hypothesis that inhibition of the UPS at the level of DUBs, upstream of the proteasome, can inhibit MM cell growth and overcome proteasome inhibitor resistance. To achieve these goals, we will pursue the following Specific Aims: Specific Aim 1: To characterize the role of deubiquitylating enzymes (DUBs) in MM cell growth, survival, and drug resistance. Specific Aim 2: To develop selective DUB inhibitors and define their in vitro mechanism of action, either alone or in combination with anti-MM agents. Specific Aim 3: To conduct preclinical in vivo studies and clinical trials of DUB inhibitors, either alone or in combination, in relapsed refractory MM. This new paradigm to target UPS pathways in MM, either at the level of proteasome or deubiquitylating enzymes, has great promise not only to change the natural history of MM, but also to serve as a model for targeted therapeutics in other cancers.