Novel small molecule USP7 Inhibitors for p53 activation and cancer therapy

项目概要： 该项目的长期目标是开发一种新的靶向治疗人类癌症的方法， 重新激活肿瘤抑制通路。尽管p53在近50%的人类中经常发生突变， 在癌症中，许多人类肿瘤保留野生型p53，但其活性通过多种途径下调。 机制等Mdm 2的失活是治疗保留野生型的人癌症的经验证的方法 p53肿瘤抑制因子的功能。经过近20年的艰苦努力， 抑制MDM 2-p53相互作用的高效小分子抑制剂和肽（也称为Mdm 2 抑制剂）已经成功地开发并在体外验证，并且这些Mdm 2抑制剂中的几种已经 已转移到人体临床试验进行体内验证。然而，一些严重的挑战仍然有待解决。 处理。主要的问题是剂量限制性毒性，因为疗效低，对正常人的毒性严重 这些Mdm 2抑制剂的剂量增加。此外，癌症中p53突变的出现 在用Mdm 2抑制剂进行初始治疗后，患者产生了高度耐药性。因此，额外的癌症 为了更有效的治疗目的，显然需要针对该途径的靶点。在本申请中，我们 计划表征新型小分子USP 7抑制剂在激活p53和癌症治疗中的作用。的 去泛素化酶USP 7（也称为HAUSP）是第一个表现出特异性作用的去泛素化酶（DUB）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的先前研究表明， USP 7通过使Mdm 2和Mdmx两者失稳而导致p53活化。值得注意的是，USP 7抑制剂也能够 在体内诱导p53非依赖性肿瘤抑制功能。例如，我们确定了N-Myc， 在神经母细胞瘤肿瘤发生中作为USP 7的关键靶点。最近，我们发现PD-L1是另一种 USP 7的重要目标。总之，这些研究表明USP 7抑制剂具有更好的功效，因为 USP 7抑制通过下调Mdm 2和Mdmx激活p53介导的肿瘤抑制， 通过使N-Myc和PD-L1不稳定来诱导p53非依赖性肿瘤生长抑制。此外，肿瘤 即使p53基因突变，N-Myc或PD-L1水平高的患者也可能不会产生耐药性。的 这里要检验的主要假设是USP 7抑制剂是否是更有效和更好的治疗剂 用于治疗人类癌症。在目标1中，我们将进一步表征从以下获得的新型USP 7抑制剂： 我们通过p53激活和N-Myc抑制肿瘤生长的高通量筛选试验 在人类神经母细胞瘤中的不稳定性。在目标2中，我们将检查USP 7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.