A Strategy for Reactivating p53 in Cancer Stem Cells Using a Novel HdmX Inhibitor

使用新型 HdmX 抑制剂重新激活癌症干细胞中 p53 的策略

• 批准号: 8568176
• 负责人: MARK W. JACKSON
• 金额: $ 20.68万
• 依托单位: CASE WESTERN RESERVE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-07-01 至 2015-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8568176
• 关键词: Adverse effects; Apoptosis; Binding; Biological Assay; Breast Cancer Cell; Breast Cancer Model; Cancer Patient; Cell Cycle Checkpoint; Cells; Characteristics; Clinical Trials; Combined Modality Therapy; Complex; DNA Damage; Data; Development; Disease; Dose-Limiting; Epithelial Cells; Exhibits; Feedback; Future; Genetic Transcription; Goals; Growth; Hdmx protein; Homologous Gene; Hormone Receptor; Human; In Vitro; Malignant Neoplasms; Mammary gland; Mediating; Microarray Analysis; Modeling; Mutation; Names; Normal Cell; Oncologist; Patients; Pattern; Pharmaceutical Preparations; Phenotype; Protein p53; Proteins; Reading; Recurrence; Regimen; Research Personnel; Resistance; Risk; Role; Series; Signal Pathway; Specificity; Stem cells; Suppressor Mutations; Testing; Time; Up-Regulation; Xenograft Model; base; cancer stem cell; cell transformation; chemotherapy; combat; fight against; high throughput screening; in vivo; inhibitor/antagonist; killings; malignant breast neoplasm; mutant; novel; nutlin 3; overexpression; prevent; public health relevance; response; small molecule; stem cell population; therapeutic target; triple-negative invasive breast carcinoma; tumor; tumor growth

DESCRIPTION (provided by applicant): The number of treatment options available to oncologists has dramatically increased in recent years due to major advances in our understanding of the signaling pathways that drive cancer development. A critical cell cycle checkpoint regulator is the p53 tumor suppressor, which is kept in check in normal cells by HdmX and Hdm2. Not surprisingly, p53 is inactivated in most human cancers, either by mutation or overexpression of Hdm2 or HdmX. Given its recently described role in suppressing a cancer stem cell (CSC) transcriptional profile, which is a hallmark of triple-negative breast cancer (TNBC) subtypes, we are proposing a new strategy aimed at reactivating p53 for the benefit of TNBC patients. Using a TNBC model, our preliminary studies have identified high levels of HdmX protein in the CSC population. Currently, DNA-damaging chemotherapy is the first-line therapy for TNBC. However, the side effects from this approach are significant and often dose limiting because DNA damage is unable to activate mutant p53 or sufficiently release wild-type p53 from HdmX. Moreover, an increased proportion of CSC compared to other breast cancer subtypes makes rapid recurrence a significant issue. The most advanced molecules currently in clinical trials for reactivating p53 include the Hdm2 antagonist Nutlin-3 and the mutant p53 reactivating compound PRIMA-1. However, Nutlin-3 specifically disrupts Hdm2-p53 but not HdmX-p53 interactions. Thus, the initial excitement over Nutlin-3 has been dampened by observations that tumors harboring high levels of HdmX are resistant to Nutlin-3 treatment. We propose TNBC CSC will not respond to Nutlin-3, or other Hdm2-specific molecules. Towards identifying HdmX- specific inhibitors to help combat TNBC, we established an assay to detect p53 activation in the presence of high-level HdmX expression and performed a high-throughput screen. We describe here the discovery of a selective inhibitor of HdmX named CTX1. The hypothesis of this proposal is that HdmX is a key regulator of CSC in TNBC, and that combined suppression of HdmX and Hdm2 will efficiently kill TNBC CSC and prevent tumor growth. We have devised two aims for the current study. In AIM 1, we will determine the mechanism and efficacy of CTX1-mediated growth suppression in TNBC. We will test whether suppression of both HdmX and Hdm2 by combined CTX1/Nutlin-3 therapy results in the sustained activation of wild-type p53, as well as mutant p53 reactivated by PRIMA-1. In AIM 2, we will examine the suppression of TNBC stem cells by combination therapy involving CTX1 and Nutlin-3 using xenograft models of CSC generated in vitro and CSC isolated from primary triple-negative breast cancers. In summary, CTX1 is an excellent compound for further studies as it exhibits high anti-cancer activity, high specificity for HdmX, and a synergy with the Hdm2 inhibitor Nutlin-3. Moreover, because TNBC patients have an increased risk of metastatic disease, respond poorly to current chemotherapeutic regimens, have a short time to recurrence, and poor overall survival, they are the ideal candidates who could benefit most from combined p53-reactivation therapy, as described here.

描述（由申请人提供）：近年来，由于我们对驱动癌症发展的信号通路的理解取得了重大进展，肿瘤学家可用的治疗选择数量急剧增加。一个关键的细胞周期检查点调节因子是p53肿瘤抑制因子，它在正常细胞中由HdmX和Hdm 2控制。毫不奇怪，p53在大多数人类癌症中是失活的，无论是通过Hdm 2或HdmX的突变或过表达。鉴于其最近描述的抑制癌症干细胞（CSC）转录谱的作用，这是三阴性乳腺癌（TNBC）亚型的标志，我们提出了一种新的策略，旨在重新激活p53，使TNBC患者受益。使用TNBC模型，我们的初步研究已经在CSC群体中鉴定出高水平的HdmX蛋白。目前，DNA损伤化疗是TNBC的一线治疗。 然而，这种方法的副作用是显著的，并且通常是剂量限制性的，因为DNA损伤不能激活突变型p53或从HdmX充分释放野生型p53。此外，与其他乳腺癌亚型相比，CSC的比例增加使得快速复发成为一个重要问题。目前在临床试验中用于重新激活p53的最先进的分子包括Hdm 2拮抗剂Nutlin-3和突变型p53重新激活化合物PRIMA-1。然而，Nutlin-3特异性地破坏Hdm 2-p53而不是HdmX-p53相互作用。因此，最初对Nutlin-3的兴奋已经被观察到的携带高水平HdmX的肿瘤对Nutlin-3治疗具有抗性而减弱。我们提出TNBC CSC将不响应Nutlin-3或其他Hdm 2特异性分子。为了鉴定HdmX特异性抑制剂以帮助对抗TNBC，我们建立了在高水平HdmX表达存在下检测p53活化的测定法并进行了高通量筛选。我们在这里描述了一种名为CTX 1的HdmX选择性抑制剂的发现。该提议的假设是HdmX是TNBC中CSC的关键调节剂，并且HdmX和Hdm 2的组合抑制将有效地杀死TNBC CSC并防止肿瘤生长。我们为目前的研究设定了两个目标。在AIM 1中，我们将确定CTX 1介导的TNBC生长抑制的机制和功效。我们将测试通过联合CTX 1/Nutlin-3治疗抑制HdmX和Hdm 2是否导致野生型p53的持续激活，以及通过PRIMA-1再激活的突变型p53。在AIM 2中，我们将使用体外产生的CSC和从原发性三阴性乳腺癌分离的CSC的异种移植模型，检查通过涉及CTX 1和Nutlin-3的组合疗法对TNBC干细胞的抑制。总之，CTX 1是一种用于进一步研究的优秀化合物，因为它表现出高抗癌活性，对HdmX的高特异性，以及与Hdm 2抑制剂Nutlin-3的协同作用。此外，由于TNBC患者转移性疾病的风险增加，对目前的化疗方案反应不佳，复发时间短，总体生存率低，因此他们是理想的候选人，可以从联合p53再激活治疗中获益最多，如本文所述。