Targeting Endocytic Recycling of EGF Receptor in Cancer

描述(申请人提供)：EGF受体和ErbB受体酪氨酸激酶(RTK)家族的其他成员在上皮组织的发育和维持中发挥着重要的生理作用，它们通过对特定配体的反应产生细胞增殖、存活、分化和迁移信号。ErbB受体的激活也与人类癌症的发生和发展有关。这些RTK已经成为抗受体抗体和激酶抑制剂的重要治疗靶点，尽管这两种治疗方式都遭遇了快速的耐药性发展，需要替代ErbB靶向治疗方法。细胞对EGFR和其他RTK配体的反应的一个基本先决条件是细胞表面必须显示一个具有激活能力的RTK池。ErbB受体的过表达增加了这个激活就绪池。足够高水平的ErbB受体过表达诱导非配体依赖的激活，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，新合成的和配体内化的受体经历了一个分选过程，这决定了它们是回到细胞表面进行配体结合和信号传递，还是作为溶酶体降解的靶标。我们和其他人已经证明，泛素连接酶Cbl家族是溶酶体命运的重要调节者。在本资助期间，其他人和我们进行的研究导致了一个新的假设，即C末端Eps15同源(EH)结构域(EHD)蛋白家族的成员是受体循环命运的关键调节因子。在这个相互竞争的更新应用中，我们将使用来自这些动物的独特的EHD基因敲除小鼠模型和细胞试剂，以及已经产生的各种免疫学、生化和细胞试剂来验证假设：依赖EHD蛋白的内吞循环是控制EGFR细胞表面显示和循环命运的关键因素；EHD功能的丧失将减弱EGFR在体外传播致癌信号的能力，并将在体内消除由EGFR驱动的肿瘤生成；取消内吞再循环将增强具有抑制性抗体的EGFR靶向治疗的疗效。因此，这项建议将评估EGFR的内吞循环作为EGFR驱动的癌症的新治疗靶点。从这些研究中获得的见解将进一步加深我们对RTK致癌信号的分子和细胞生物学调节的理解，并有助于验证RTK的内吞循环作为合理设计抗癌药物以加强现有RTK靶向治疗的新途径。

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.