Analysis of active and inactive EGFR conformations

描述（由申请人提供）：受体酪氨酸激酶（RTK）的表皮生长因子受体（EGFR）家族在许多人类癌症中很重要，并且是几种FDA批准的治疗药物的靶点。目前使用的EGFR靶向抗体治疗剂被特别选择以抑制EGF结合和受体的EGF依赖性活化。然而，现在很清楚，许多EGFR依赖性癌症是由EGFR中的致癌突变引起的，这些突变促进了配体非依赖性信号传导-这可能不会被西妥昔单抗等抗体阻断。对肺癌患者致癌激活EGFR的研究是推进对EGFR激酶结构域如何调节的理解的关键。在胶质母细胞瘤和其他癌症中，在所有EGFR家族成员的细胞外区域中鉴定出越来越多的突变。这为充分理解细胞外区域的调控提供了类似的机会-这是一个重要的目标，因为目前基于结构的EGFR受体激活模型不能解释（或预测）这些体细胞突变中的哪一个将激活受体。在这个建议中，我们首先问如何致癌突变的EGFR细胞外区域可以促进配体非依赖性激活的受体，也完善我们的理解，EGFR的细胞外区域是如何保持在其非活性状态。在第二个目标，我们问什么是最有效的策略，以抑制致癌激活的EGFR使用抗体治疗。单纯阻断配体结合的药物（如西妥昔单抗）可能不是致癌突变激活受体的有效抑制剂。我们将比较不同EGFR靶向抗体和新型单链抗体基药物（VHH结构域）抑制癌症中突变EGFR变体的组成性（配体非依赖性）信号传导的能力。我们将结合联合收割机细胞的研究，在体外和EGFR胞外区的结构分析，调查这些问题。我们的具体目标是：一曰：了解哪些分子内相互作用有助于EGFR的细胞外自身抑制，以及它们如何通过癌症患者中发现的配体结合和体细胞突变逆转。第二章：检验EGFR中已知致癌突变对EGFR靶向抗体和新型VHH结构域药物的抑制活性有差异影响的假设。总之，这些研究将揭示致癌突变引起EGFR和其他ErbB受体组成性激活的机制，同时还确定了能够独特地阻断EGFR突变体的配体非依赖性激活的新抗体。这些药物将是未来临床开发的高度优先事项。

DESCRIPTION (provided by applicant): The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases (RTKs) is important in many human cancers, and is the target of several FDA-approved therapeutic agents. Currently-used EGFR-targeted antibody therapeutics were specifically selected to inhibit EGF binding and EGF-dependent activation of the receptor. However, it is now clear that many EGFR-dependent cancers arise from oncogenic mutations in EGFR that promote ligand-independent signaling - which may not be blocked by antibodies such as cetuximab. Studies of oncogenically activated EGFR from lung cancer patients have been key in advancing understanding of how the EGFR kinase domain is regulated. An increasing number of mutations are being identified in the extracellular region of all EGFR family members, in glioblastoma and other cancers. These open up a similar opportunity for fully understanding regulation of the extracellular region - an important goal since current structure-based models of EGFR receptor activation do not explain (or predict) which of these somatic mutations will activate the receptors. In this proposal we first ask how oncogenic mutations in the EGFR extracellular region can promote ligand-independent activation of the receptor, and also refine our understanding of how the extracellular region of EGFR is maintained in its inactive state. In a second aim, we ask what are the most effective strategies to inhibit oncogenically-activated EGFR using antibody therapeutics. Agents (such as cetuximab) that simply block ligand binding may not be effective inhibitors of receptors that are activated by oncogenic mutation. We will compare the ability of different EGFR-targeted antibodies and novel single chain antibody-based agents (VHH domains) to inhibit constitutive (ligand-independent) signaling by mutated EGFR variants found in cancers. We will combine cellular studies with in vitro and structural analyses of the EGFR extracellular region to investigate these questions. Our Specific Aims are: 1: To understand which intramolecular interactions contribute to extracellular autoinhibition of EGFR, and how they are reversed by ligand binding and somatic mutations found in cancer patients. 2: To test the hypothesis that known oncogenic mutations in EGFR differentially affect the inhibitory activity of EGFR-targeted antibodies and of novel VHH domain agents. In sum, these studies will shed important new light on the mechanisms through which oncogenic mutations cause constitutive activation of EGFR and other ErbB receptors, while also identifying new antibodies that are uniquely able to block ligand-independent activation of EGFR mutants. Such agents will be of high priority for future clinical development.