Mechanisms of novel cancer targets in ARF-mediated tumor suppression

ARF 介导的肿瘤抑制中新癌症靶点的机制

• 批准号: 9121484
• 负责人: Wei Gu
• 金额: $ 33.2万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9121484
• 关键词: 26S proteasome; Binding; Biochemical; Cancer Cell Growth; Cells; Excision; Exhibits; Feedback; Goals; Growth; Human; Knockout Mice; Lead; Malignant Neoplasms; Mediating; Mediator of activation protein; Messenger RNA; Methods; Mutant Strains Mice; Null Lymphocytes; Oncogenic; Pathway interactions; Play; Protein p53; RNA; Role; Stress; TP53 gene; Testing; Therapeutic; Transcript; Tumor Suppression; Tumor Suppressor Proteins; Ubiquitination; cancer cell; cancer therapy; in vivo; inhibitor/antagonist; knock-down; mouse model; novel; nutlin 3; overexpression; restoration; small molecule inhibitor; tumor; tumorigenesis; ubiquitin ligase; ubiquitin-protein ligase

DESCRIPTION (provided by applicant): The E3 ubiquitin ligase Mdm2 acts as a key factor in the degradation of p53 tumor suppressor in human cancer cells and inhibition of Mdm2 activity is a validated approach to activate p53 function in cancer therapy. Nevertheless, inhibitors of Mdm2 such as Nutlin-3 has many limitations, suggesting that additional targets in this pathway need to be further elucidated. The proposed studies aim to dissect the mechanisms of two newly identified ubiquitin ligases critically involved in ARF/p53-mediated tumor suppression and provide the unequivocal evidence for "proof of concept" to develop the inhibitors of these two potential critical targets in cancer therapy. ARF was originally identified as an alternative transcript of the Ink4a/ARF tumor suppressor locus. It is well accepted that ARF plays a major role in activating p53 function, specifically, in respond to oncogenic stress. Surprisingly, by usig a mouse model in which p53 status can be reversibly switched in vivo between functional and inactive states, it has been found that the protection from tumorigenesis is absolutely dependent on ARF-mediated p53 activation in vivo. Thus, ARF apparently plays a much more important role in suppressing tumorigenesis in general, than originally anticipated. Restoration of the ARF-p53 function remains an important goal in the quest for more effective cancer therapeutics. Indeed, like ARF, Nutlin-3, a small molecule inhibitor of Mdm2, is able to activate p53, and exhibits antitumor efficacy in cancer cells that express wild-type p53. Nevertheless, although Nutlin-3 can effectively block the interaction of Mdm2 and p53, Nutlin-3 is also very effective at increasing the synthesis of Mdm2 mRNA and protecting Mdm2 from degradation. These effects of Nutlin-3 on Mdm2 lead to a rapid restore of cancer cell growth upon temporary removal of the compound, sabotaging the efficacy of nutlin-3 in cancer therapy. Thus additional cancer targets aiming at this pathway are clearly needed for more effective therapeutic purpose. Our preliminary studies reveal that targeting two novel ubiquitin ligases (ARF-BP1 and ULF) in the ARF-p53 pathway represents a particularly attractive approach to activate ARF-mediated tumor suppression in cancer therapy. The central hypothesis to be tested here is that inactivation of ARF-BP1 or ULF can effectively activate ARF-mediated function and suppress tumorigenesis in vivo. It includes the following two specific aims. In Aim 1, we will investigate whether inactivatin of ULF activity is sufficient to suppress tumorigenesis by using mouse models. In Aim 2, to validate whether ARF-BP1 is indeed a potential cancer target, we will use the ARF-BP1 mutant mice to examine whether inhibition of ARF-BP1 suppresses tumorigenesis in vivo in a manner reminiscent of ARF activation.

描述（由申请人提供）：E3泛素连接酶MDM2是人类癌细胞中p53肿瘤抑制剂降解和MDM2活性抑制的关键因素，是激活癌症治疗中p53功能的验证方法。然而，MDM2（例如Nutlin-3）的抑制剂有许多局限性，这表明该途径中的其他靶标需要进一步阐明。拟议的研究旨在剖析两个新发现的泛素连接酶的机制，这些泛素连接酶严格涉及ARF/p53介导的肿瘤抑制，并为“概念证明”提供了明确的证据，以开发这两个潜在的关键靶标在癌症治疗中的抑制剂。 ARF最初被鉴定为INK4A/ARF肿瘤抑制基因座的替代转录本。众所周知，ARF在激活p53功能方面起着重要作用，特别是在响应致癌应力方面。令人惊讶的是，通过USIG，小鼠模型可以在功能状态和非活动状态之间在体内可逆地切换p53状态，已经发现，对肿瘤发生的保护绝对取决于ARF介导的p53在体内激活。因此，ARF显然在抑制肿瘤发生的过程中起着比最初预期的更重要的作用。恢复ARF-P53功能仍然是寻求更有效癌症治疗剂的重要目标。确实，像ARF一样，MDM2的小分子抑制剂Nutlin-3也能够激活p53，并在表达野生型p53的癌细胞中表现出抗肿瘤功效。然而，尽管Nutlin-3可以有效地阻断MDM2和p53的相互作用，但Nutlin-3在增加MDM2 mRNA的合成并保护MDM2免受降解方面也非常有效。 Nutlin-3对MDM2的这些影响导致临时去除该化合物后，癌细胞的生长迅速恢复，破坏了Nutlin-3在癌症治疗中的功效。因此，对于更有效的治疗目的，显然需要针对该途径的其他癌症靶标。我们的初步研究表明，针对ARF-P53途径的两种新型的泛素连接酶（ARF-BP1和ULF）是一种特别有吸引力的方法，是激活ARF介导的癌症治疗中抑制ARF介导的肿瘤。这里要检验的中心假设是，ARF-BP1或ULF的失活可以有效地激活ARF介导的功能并抑制体内肿瘤发生。它包括以下两个特定目标。在AIM 1中，我们将研究ULF活性的灭活素是否足以通过使用小鼠模型抑制肿瘤发生。在AIM 2中，为了验证ARF-BP1是否确实是一个潜在的癌症靶标，我们将使用ARF-BP1突变小鼠检查ARF-BP1的抑制是否会以一种让人联想的ARF激活的方式抑制体内的肿瘤发生。