Genetic dissection and inhibitor targeting of Rac signaling in pancreatic cancer.

描述(申请人提供)：胰腺癌(PDAC)是一种致命的疾病，5年存活率为4%，目前的治疗方案很少，而且无效。因此，仍然迫切需要针对这种癌症的新的靶向治疗方法。最近的研究表明，激活RAC小GTP酶的信号通路在PDAC肿瘤的发生、生长和侵袭中具有重要作用。因此，我们假设RAC信号的抑制剂将是治疗PDAC的有效策略。然而，虽然RAC和其他小的GTP酶(如RAS)被证实是关键的疾病驱动因素，但目前并不被认为是癌症治疗的有吸引力或可用药的靶点。虽然最近已经建立了合成致命性基因筛查来鉴定RAS致癌的关键成分，但还没有对RAC进行这样的哺乳动物细胞检测。因此，需要新的方法。我们已经建立、验证和执行了一种基于线虫的新的正选择功能筛选，用于(A)识别其功能对RAC活性至关重要的基因和(B)高通量化学文库筛选以确定RAC致死性的小分子抑制物。在我们的模型中，线虫中RAC同源基因CED-10的结构性激活会导致100%的致死率，从而为我们的遗传和药物筛选提供积极的选择。这种模式结合了遗传适宜性、低成本和与全基因组遗传兼容的培养条件和在整个动物环境中的高通量化学筛选。我们应用这个线虫模型，结合哺乳动物细胞培养和小鼠模型进行验证和进一步分析，可能会发现在PDAC中阻断RAC的新方法。如果成功，我们的概念验证研究将表明，基于线虫的模型可以有效地用于药物发现，并将激发人们对靶向小GTP酶和开发其他基于生物体的药物发现功能筛选的新兴趣。为了实现这一目标，我们提出了三个目标：(1)确定其干扰特定地抑制激活的CED-10/RAC的基因，(2)识别抑制CED-10/RAC致死性的小分子抑制剂，以及(3)应用基于细胞和小鼠的验证遗传定义的RAC信号组件和小分子抑制剂。相关性：胰腺癌是一种致命的疾病，5年生存率为4%，有效的治疗选择很少，而且无效。传统的药物发现方法在解决这一问题上并不有效。我们建议我们应用一种创新的新模型系统进行药物发现，重点放在这种致命疾病的有效新治疗靶点上。 公共卫生相关性：胰腺癌是一种致命的疾病，5年生存率为4%，有效的化疗选择很少，而且无效。传统的药物发现方法在解决这一问题上并不有效。我们建议研究一个新的靶点，RAC小GTP酶，并将线虫模型应用于全基因组遗传和高通量化学筛选，以确定胰腺癌新的RAC特异性靶点和治疗方法。

DESCRIPTION (provided by applicant): Pancreatic cancer (PDAC) is a lethal disease with 5-year survival of 4% and current therapeutic options are few and ineffective. Therefore, there remains a dire need for novel targeted therapies for this cancer. Recent studies have implicated the importance of signaling pathways that activate the Rac small GTPase in PDAC tumorigenic growth and invasion. We therefore hypothesize that inhibitors of Rac signaling will be an effective strategy for PDAC treatment. However, while well validated as key disease drivers, Rac and other small GTPases (e.g. Ras) are not currently considered to be attractive or druggable targets for cancer treatment. While recent synthetic lethality genetic screens have been established to identify key components of Ras oncogenesis, no such mammalian cell assay has been identified for Rac. Therefore, novel approaches are needed. We have established, validated and performed a novel C. elegans-based positive-selection functional screen for (a) identifying genes whose functions are critical for Rac activity and (b) high-throughput chemical library screening to identify small molecule inhibitors of Rac lethality. In our model, constitutive activation of the Rac ortholog in C. elegans, CED-10, causes 100% lethality, thus providing positive selection for our genetic and pharmacologic screens. This model combines genetic amenability, low cost and culture conditions compatible with genome wide genetic and high-throughput chemical screening in a whole animal context. Our application of this C. elegans model, when coupled with mammalian cell culture and mouse models for validation and further analyses, may identify novel approaches for blocking Rac in PDAC. If successful, our proof-of-concept studies will show that C. elegans-based models can be effective for drug discovery and will stimulate renewed interest both in targeting small GTPases and in development of other organism-based functional screens for drug discovery. We propose three aims to accomplish this goal: (1) identify the genes whose disruption specifically suppressed activated CED-10/Rac, (2) identify small molecule inhibitors that suppress CED-10/Rac lethality, and (3) apply cell- and mouse-based validation of genetically defined Rac signaling components and small molecule inhibitors. Relevance: Effective therapeutic options for pancreatic cancer, a lethal disease with 5-year survival of 4%, are few and ineffective. Traditional drug discovery approaches have not been effective in addressing this problem. We propose our application of an innovative new model system for drug discovery focused on a validated new therapeutic target for this deadly disease PUBLIC HEALTH RELEVANCE: Effective chemotherapeutic options for pancreatic cancer, a lethal disease with 5-year survival of 4%, are few and ineffective. Traditional drug discovery approaches have not been effective in addressing this problem. We propose the study of a novel target, the Rac small GTPase, and the application of a C. elegans nematode model for genome-wide genetic and high-throughput chemical screens to identify novel Rac-specific targets and therapies for pancreatic cancer.