Targeting EphA2 in Glioblastoma

 描述(申请人提供)胶质母细胞瘤(GBM)仍然是一种很大程度上无法治愈的疾病，5年生存率不到10%。迫切需要有效的靶向治疗，以补充已经达到的最大放疗和化疗。越来越多的证据表明，EphA2受体是GBM的一个有吸引力的靶点。PI的实验室和其他人最近发现了EphA2在肿瘤病因学和恶性进展中的双重作用。当与配体结合时，EphA2是一种肿瘤抑制因子，并抑制GBM细胞中ERK和Akt的活性。然而，在缺乏配体的情况下，EphA2被丝氨酸897上的AGC激酶包括Akt和P90-RSK磷酸化，S897磷酸化将EphA2从肿瘤抑制因子转化为致癌蛋白，在体外促进胶质瘤细胞的迁移和在体内促进胶质瘤干细胞(GSC)的颅内侵袭。PS897-EphA2表达水平与肿瘤分级有关。在缺乏配体的情况下，pS897-EphA2在机制上调节GSCs的干细胞属性并促进胶质瘤的形成。相反，在配体刺激下，EphA2诱导GSC分化并抑制肿瘤的发展。基于这一系列的观察，我们认为EphA2的配体模拟小分子激动剂可以成为治疗GBM的新型药物。这些激动剂有望：1)恢复EphA2固有的肿瘤抑制功能；2)破坏原癌基因Akt/RSK-EphA2信号轴；3)诱导GSC分化。通过结构导向的虚拟筛选和基于细胞的分析，我们报道了临床上仍在用于治疗高血压的α1受体拮抗剂多沙唑嗪(DZ)是一种真正的EphA2激动剂。DZ以EphA2依赖的方式抑制ERK和Akt，并抑制肿瘤细胞的扩散。更多有效的DZ衍生物已经通过药物化学进行了表征，包括BW27，它在临床前模型中抑制GBM，并能够穿越血脑屏障(BBB)。这项建议的首要目标是将这些基础和临床前的发现转化为新的GBM治疗剂。BW27将接受针对所有四种人GBM分子亚型的系统临床前测试。BW27的靶向效应将使用基因工程小鼠模型进行研究。最终确定EphA2与BW27形成的配合物的X射线共晶结构，以指导下一代(S)EphA2激动剂的设计。这些研究的完成可能导致新的基于机制的小分子药物(S)用于治疗基底膜的干预。

 DESCRIPTION (provided by applicant) Glioblastoma (GBM) remains a largely incurable disease, with a 5 year survival rate of less than 10%. Effective targeted therapies to complement already maximal radiation and chemotherapy are urgently needed. Converging evidence shows that the EphA2 receptor is an attractive target for GBM. The PI's lab and others recently uncovered dual roles of EphA2 in tumor etiology and malignant progression. When engaged with ligands (ephrin-As), EphA2 is a tumor suppressor and inhibits both ERK and Akt activities in GBM cells. However, in the absence of ligands, EphA2 is phosphorylated by AGC kinases including Akt and p90-RSK on serine 897, and S897 phosphorylation converts EphA2 from a tumor suppressor into an oncogenic protein that promotes glioma cell migration in vitro and intracranial invasion of glioma stem cells (GSC) in vivo. Moreover level of pS897-EphA2 is correlated with tumor grades. Mechanistically pS897- EphA2 regulates the stem properties of GSCs and promotes gliomagenesis in the absence of ligands. In contrast, upon ligand stimulation, EphA2 induces GSC differentiation and inhibits tumor development. Based on this series of observations, we propose that ligand-mimicking small molecule agonists of EphA2 can be novel therapeutic agents for GBM. Such agonists are expected to i) restore the intrinsic tumor suppressor functions of EphA2, ii) disrupt the pro- oncogenic Akt/RSK-EphA2 signaling axis, and iii) induce differentiation of GSCs. Using structure- guided virtual screening and cell-based assays, we reported that doxazosin (DZ), an α1- adrenoceptor antagonist still in clinical use for hypertension, is a bona fide EphA2 agonist. DZ inhibits ERK and Akt and suppresses tumor cell dissemination in an EphA2-dependent manner. Much more potent derivatives of DZ have been characterized through medicinal chemistry, including BW27, which suppressed GBM in preclinical models and was capable of crossing the blood-brain barrier (BBB). The overarching goal of this proposal is to translate these basic and preclinical discoveries into nove GBM therapeutic agents. BW27 will be subject to systemic preclinical test across all four molecular subtypes of human GBM. The on-target effects of BW27 will be investigated using the genetically engineered mouse model. Finally the X-ray co-crystal structure of EphA2 in complex with BW27 will be determined to guide the design of next generation(s) of EphA2 agonists. Completion of the studies could lead to new mechanism-based small molecule drug(s) for therapeutic intervention of GBM.