Novel small molecule USP7 Inhibitors for p53 activation and cancer therapy

项目总结： 该项目的长期目标是开发一种新的针对人类癌症的靶向治疗方法，通过 重新激活肿瘤抑制通路。尽管在几乎50%的人类中p53经常发生突变 癌症，许多人类肿瘤保留野生型P53，但其活性通过多个 机械装置。灭活MDM2是治疗保留野生型人类癌症的有效方法 通过重新激活P53的肿瘤抑制功能。经过近二十年的紧张努力，一批 抑制MDM2-P53相互作用的高效小分子抑制剂和多肽(也称为MDM2 抑制剂)已被成功开发并在体外验证，其中几种MDM2抑制剂已经 已经转移到人体临床试验中进行体内验证。然而，一些严峻的挑战仍然存在 地址。主要的问题是剂量限制毒性，因为低疗效和对正常的严重毒性。 随着这些MDM2抑制剂剂量的增加，组织中的DNA含量增加。此外，在癌症中出现P53突变 患者在最初使用MDM2抑制剂治疗后产生了高度耐药性。因此，额外的癌症 显然，为了达到更有效的治疗目的，需要针对这一途径的靶点。在此应用程序中，我们 计划表征新的小分子USP7抑制剂在激活p53和癌症治疗中的作用。这个 脱泛素酶USP7(又称Hausp)是第一批发挥特殊作用的脱泛素酶(DUBS)之一 在体内调节蛋白质的稳定性。我们实验室和其他实验室之前的研究表明，抑制 USP7通过破坏MDM2和MDMX的稳定而导致P53的激活。值得注意的是，USP7抑制剂也能够 体内诱导非P53依赖的肿瘤抑制功能。例如，我们确定了N-Myc，这是一个主要驱动因素 在神经母细胞瘤中，肿瘤发生是USP7的关键靶点。最近，我们发现PD-L1是另一种 USP7的重要目标。综上所述，这些研究表明，USP7抑制剂具有更好的疗效，因为 USP7抑制通过下调MDM2和MDMX激活P53介导的肿瘤抑制 通过破坏N-Myc和PD-L1的稳定性，诱导非p53依赖性的肿瘤生长抑制。此外，这些肿瘤 高水平的N-Myc或PD-L1即使在p53基因突变的情况下也可能不会产生耐药性。这个 这里要检验的主要假设是，USP7抑制剂是否更有效、更好的治疗剂 用于治疗人类癌症。在目标1中，我们将进一步表征从以下途径获得的新型USP7抑制剂 我们的高通量筛选试验同时通过P53激活和N-Myc抑制肿瘤生长 人类神经母细胞瘤的不稳定。在目标2中，我们将检查USP7抑制剂是否能够 通过下调人类癌细胞中的PD-L1来促进免疫治疗。

Project Summary: The long-term objective of this project is to develop a novel targeted therapy for human cancers by reactivating the tumor suppression pathways. Although p53 is frequently mutated in almost 50% of human cancers, many human tumors retain wild-type p53 but its activities are downregulated through multiple mechanisms. Inactivation of Mdm2 is a validated approach for the treatment of human cancer retaining wild-type p53 by reactivating the p53 tumor suppressor function. Through nearly two decades of intense efforts, a number of highly potent small-molecule inhibitors and peptides that inhibit the MDM2–p53 interaction (also called Mdm2 inhibitors) have been successfully developed and validated in vitro, and several of these Mdm2 inhibitors have been moved to human clinical trials for in vivo validation. Nevertheless, some serious challenges remain to be addressed. The major issue is the dose-limiting toxicity because of low efficacy and severe toxicity to normal tissues with increasing dosage of these Mdm2 inhibitors. Moreover, emergence of p53 mutations in cancer patients developed highly resistance after the initial treatment with Mdm2 inhibitors. Thus, additional cancer targets aiming at this pathway are clearly needed for more effective therapeutic purpose. In this application, we plan to characterize novel small molecule USP7 inhibitors in activating p53 and cancer therapy. The deubiquitinase USP7 (also called HAUSP) was one of the first deubiquitinases (DUBs) that exhibit a specific role in regulating protein stability in vivo. Previous studies from our lab and others demonstrated that inhibition of USP7 leads to p53 activation by destabilizing both Mdm2 and Mdmx. Notably, USP7 inhibitors are also able to induce p53-independent tumor suppression functions in vivo. For example, we identified N-Myc, a major driver in neuroblastoma tumorigenesis as a critical target for USP7. Recently, we discovered PD-L1 as another important target of USP7. Taken together, these studies reveal that USP7 inhibitors have better efficacy because USP7 inhibition activates p53-mediated tumor suppression by downregulating both Mdm2 and Mdmx and also induces p53-independent tumor growth suppression by destabilizing N-Myc and PD-L1. Moreover, the tumors with high levels of N-Myc or PD-L1 may not develop drug resistance even when the p53 gene is mutated. The major hypothesis to be tested here is whether USP7 inhibitors are more effective and better therapeutic agents for the treatment of human cancers. In Aim 1, we will further characterize novel USP7 inhibitors obtained from our high-through-put screening assays in suppressing tumor growth through both p53 activation and N-Myc destabilization in human neuroblastomas. In Aim 2, we will examine whether the USP7 inhibitor is able to promote immunotherapy by downregulating PD-L1 in human cancer cells.