EphA2 Agonists as Novel Inhibitors of Tumor Progression

EphA2 激动剂作为肿瘤进展的新型抑制剂

• 批准号: 6470384
• 负责人: Bingcheng Wang
• 金额: $ 30.64万
• 依托单位: CASE WESTERN RESERVE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-04-01 至 2006-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6470384
• 关键词: X ray crystallography; athymic mouse; carcinogenesis inhibitor; cell migration; cell motility; enzyme inhibitors; fluorescence; fluorescent dye /probe; focal adhesion kinase; green fluorescent proteins; metastasis; mitogen activated protein kinase; neoplasm /cancer transplantation; neoplastic cell; neoplastic process; peptide library; prostate neoplasms; protein structure function; protein tyrosine kinase; whole body imaging /scanning

The overall objective of this proposal is to test whether EphA2 kinase agonists can inhibit prostate cancer progression through novel negative signaling pathways identified in the applicant's laboratory. There are two basic steps in tumor metastasis: one is tumor cell dissemination and the other is growth at distal sites. Cell motility is central to tumor cell dissemination, while metastatic growth is governed by autocrine and paracrine factors that frequently converge on Ras/MAPK signaling pathway. Therefore, agents that can inhibit either cell motility or suppress MAPK activation are potential candidates for anti-cancer drug discovery. The applicant's laboratory demonstrates that EphA2 receptor tyrosine kinase (RTK) can inhibit cell migration by targeting integrins and focal adhesion kinase, and attenuate Ras/MAPK cascade by lowering Ras GTP loading. Moreover, in both human and canine prostate cancer (PCa), EphA2 expression is correlated with tumor progression. These data suggest that EphA2 is a novel target to prevent progression of PCa. To this end, a small EphA2-binding peptide (EP1) has been isolated from phage display libraries. Functionally, EP1 mirrors ephrin-A1 in its ability to suppress cell motility and growth, establishing the feasibility of targeting EphA2 with small molecules. The aims of this proposal are: 1) To validate EphA2 as an anti-cancer progression target in vivo. Initial studies will assess how EphA2 agonists affect subcutaneous tumor growth of green fluorescence protein (GFP)- tagged PC-3 cells. In the second phase studies, GFP-PC-3 cells will be implanted orthotopically to determine the effects of EphA2 agonists on metastasis, which will be monitored in part by whole body imaging in live animals, and by organ imaging at necropsy using fluorescence stereomicroscope. 2) To determine X- ray crystallographic structure of EphA2 ligand-binding domain in complex with ephrin-A1 or EP-1 peptide. The structural information will be used to guide the selection of smaller and more potent peptide agonists. 3) To identify the effectors which mediate the inhibitory effects of EphA2 activation on Ras/MAPK pathway. Completion of the proposed studies can lead to new mechanism-based therapeutic agents and strategies for prostate cancer.

本提案的总体目标是测试EphA2激酶激动剂是否可以通过申请人实验室发现的新型负信号通路抑制前列腺癌的进展。肿瘤转移有两个基本步骤：一是肿瘤细胞播散，二是肿瘤远端生长。细胞运动是肿瘤细胞传播的核心，而转移性生长受自分泌和旁分泌因素控制，这些因素经常聚集在Ras/MAPK信号通路上。因此，能够抑制细胞运动或抑制MAPK激活的药物是发现抗癌药物的潜在候选者。申请人的实验室证明，EphA2受体酪氨酸激酶（RTK）可以通过靶向整合素和局灶黏附激酶来抑制细胞迁移，并通过降低Ras GTP负荷来减弱Ras/MAPK级联。此外，在人和犬前列腺癌（PCa）中，EphA2的表达与肿瘤进展相关。这些数据表明，EphA2是一个新的靶点，以防止前列腺癌的进展。为此，从噬菌体展示文库中分离出一个小的epha2结合肽（EP1）。在功能上，EP1与ephrin-A1一样具有抑制细胞运动和生长的能力，这就建立了小分子靶向EphA2的可行性。本课题的目的是：1)在体内验证EphA2作为抗癌进展靶点。初步研究将评估EphA2激动剂如何影响绿色荧光蛋白（GFP）标记的PC-3细胞的皮下肿瘤生长。在第二阶段的研究中，GFP-PC-3细胞将被原位植入，以确定EphA2激动剂对转移的影响，这将部分通过活体动物全身成像和荧光立体显微镜尸检器官成像来监测。2)测定EphA2配体结合域与ephrin-A1或EP-1肽复合物的X射线晶体结构。结构信息将用于指导选择更小和更有效的肽激动剂。3)鉴定介导EphA2活化对Ras/MAPK通路抑制作用的效应因子。这些研究的完成可能会导致新的基于机制的前列腺癌治疗药物和策略。