Targeting Endocytic Recycling of EGF Receptor in Cancer

描述（由申请人提供）：EGF受体和受体酪氨酸激酶（RTK）ErbB家族的其他成员通过响应特定配体产生细胞增殖、存活、分化和迁移信号，在上皮组织的发育和维持中发挥重要的生理作用。ErbB受体的激活也与人类癌症的发生和发展有关。这些RTK已成为抗受体抗体和激酶抑制剂的重要治疗靶标，尽管这两种治疗方式都遭受快速耐药性发展，需要替代ErbB靶向治疗的方法。对EGFR和其他RTK配体的细胞应答的基本先决条件是RTK的活化能力库必须展示在细胞表面上。ErbB受体过表达增加了这个激活就绪池。足够高水平的ErbB受体过表达诱导配体非依赖性激活，这也可以通过癌症相关的激活突变来实现。RTK功能的一个基本特征是新合成的以及配体内化的受体经历分选过程，该分选过程确定它们是否将再循环回到细胞表面用于配体结合和信号传导，或者将被靶向用于溶酶体降解。我们和其他人已经表明，Cbl家族的泛素连接酶是溶酶体命运的重要调节因子。其他人和我们在当前资助期间进行的研究导致了一种新的假设，即C-末端Eps 15-同源（EH）结构域（EHD）蛋白家族成员作为受体回收命运的关键调节因子发挥作用。 在这一竞争性更新申请中，我们将采用独特的EHD敲除小鼠模型和源自这些动物的细胞试剂，以及大量的免疫学、生物化学和细胞试剂，这些试剂已被产生以测试以下假设：EHD蛋白依赖性内吞再循环是EGFR的细胞表面展示和再循环命运的关键控制器; EHD功能的丧失将减弱EGFR在体外传播致癌信号的能力，并将消除EGFR驱动的体内肿瘤发生;并且消除内吞再循环将增强用抑制性抗体进行EGFR靶向治疗的功效。因此，该提议将评估EGFR作为EGFR驱动的癌症中的新型治疗靶点的内吞再循环。从这些研究中获得的见解应进一步加深我们对RTK致癌信号传导的分子和细胞生物学调节因子的理解，并有助于验证RTK的内吞再循环作为合理设计抗癌药物以增强现有RTK靶向治疗的新方法。

DESCRIPTION (provided by applicant): EGF receptor and other members of the ErbB family of receptor tyrosine kinases (RTKs) play essential physiological roles in development and maintenance of epithelial tissues by generating cell proliferation, survival, differentiation, and migration signals in response to specific ligands. Activation of ErbB receptors is also linked to the initiation and progression of human cancers. These RTKs have emerged as important therapeutic targets of anti-receptor antibodies and kinase inhibitors, although both therapeutic modalities suffer from rapid resistance development, necessitating alternate approaches to ErbB-targeted therapy. An essential pre-requisite for cellular response to EGFR and other RTK ligands is that an activation-competent pool of RTKs must be displayed on the cell surface. ErbB receptor overexpression increases this activation-ready pool. Sufficiently high levels of ErbB receptor overexpression induce ligand-independent activation, which can also be achieved by cancer-associated activating mutations. A fundamental feature of RTK function is that the newly synthesized as well as ligand-internalized receptors undergo a sorting process that determines whether they will recycle back to the cell surface for ligand binding and signaling or will be targeted for lysosomal degradation. We, and others, have shown that Cbl family of ubiquitin ligases are essential regulators of the lysosomal fate. Studies carried out by others and by us during the current funding period have led to a novel hypothesis that members of the C-terminal Eps15-homology (EH) domain-containing (EHD) protein family function as key regulators of the recycling fate of receptors. In this competing renewal application, we will employ unique EHD knockout mouse models and cellular reagents derived from these animals together with a vast array of immunological, biochemical and cellular reagents that have been generated to test the hypotheses: EHD protein-dependent endocytic recycling is a key controller of the cell surface display and recycling fate of EGFR; loss of EHD function will attenuate the ability of EGFR to propagate oncogenic signals in vitro and will abrogate EGFR-driven oncogenesis in vivo; and abrogation of endocytic recycling will enhance the efficacy of EGFR targeted therapy with an inhibitory antibody. Thus, this proposal will evaluate the endocytic recycling of EGFR as a novel therapeutic target in EGFR-driven cancer. Insights gained from these studies should further our understanding of the molecular and cell biological regulators of oncogenic signaling by RTKs, and help validate the endocytic recycling of RTKs as a new approach to rationally design anti-cancer agents to potentiate existing RTK-targeted therapies.