Pathogenesis of Cancer - Role of EGF Receptor Endocytosis

表皮生长因子(EOF)受体(EGFR)在肿瘤的发生发展中起重要作用 许多人类上皮性癌与预后不良有关，已成为主要的预后因素 多种癌症的标志物和治疗靶点。阐明细胞的生理调节机制 因此，EGFR是理解其致癌活性和致癌机制的关键。 削弱了EGFR疗法的潜力。生长因子与EGFR结合触发复杂的 信号转导过程的阵列。受体的激活也通过包被分子筛蛋白引起快速的内吞作用。 溶酶体中配体-受体复合体的凹坑和降解。因此，细胞内转运决定了 细胞中活跃的EGFR的数量，因此，信号过程的强度和持续时间。 内吞作用也在EGFR信号的时空调节中发挥作用，这可能控制着 信号传递过程的动态和特定模式。然而，EGFR内吞作用的机制 而且它与正常细胞和癌细胞中的信号传递过程之间的相互作用仍然知之甚少。主 这项建议的目的是描绘EGFR内吞作用的机制，并确定 肿瘤发生发展过程中的内吞作用。在本项目的前一个资金周期内 我们已经确定了控制网状蛋白介导的内化的生理途径的关键蛋白质 EGFR。我们的研究还证明了EGFR信号复合体在内体中的定位以及 内吞作用对信号的重要性。我们开发了新的EGFR定量分析方法 活细胞中的复合体和一种分析EGFR内吞作用的新方法 高效的RNA干扰。这些重要的进展使得现在可以开发一种 癌细胞中EGFR内吞作用如何调节以及内吞过程如何的综合模型 调控癌变。在这个项目中，我们重点分析头颈癌(HNC) EGFR经常过度表达，被认为是一个重要的治疗靶点。具体目标 主要研究内容如下：1)通过网织蛋白包被的小孔，确定EGFR内吞作用的分子机制。这一目标将在 具体地说，使用新的质谱学方法确定泛素化在EGFR内吞作用中的作用； 2)测试内皮细胞转运受损的新的EGFR突变体是否会产生信号模式的改变 并影响HNC移植瘤的体内成瘤特性；3)检测HNC细胞是否发生改变 调节EGFR及可能其他致癌受体酪氨酸内吞作用的蛋白表达 激酶在体外影响EGFR信号转导和体内影响HNC异种移植瘤的致瘤特性。成功者 该提案目标的完成将为设计治疗和预防方案开辟新的途径 EGFR表达肿瘤的治疗策略。

Epidermal growth factor (EOF)receptor (EGFR) is important for the development and progression of many human epithelial cancers, associated with poor prognosis and has become the major prognostic marker and therapeutic target in a variety of these cancers. Elucidation of the physiological regulation of EGFR is, therefore, a key to understanding of the mechanisms causing its oncogenic activation and impairing the potential of EGFR therapeutics. Growth factor binding to the EGFR triggers a complicated array of signal transduction processes. Receptor activation also causes rapid endocytosis via clathrin-coated pits and degradation of the ligand-receptor complexes in lysosomes. Thus, endocytic trafficking determines the number of active EGFRs in the cell and,therefore, the intensity and duration of signaling processes. Endocytosis also plays role in spatial and temporal regulation of EGFR signaling, which may control the dynamics and the specific pattern of signaling processes. However, the mechanisms of EGFR endocytosis and its cross-talks with signaling processes in normal and cancer cells remain poorly understood. The main goal of this proposal is to delineate the mechanisms of EGFR endocytosis, and to define the role of endocytosis in the development and progression of cancer. During the previous funding cycle of this project we have identified key proteins that control the physiological pathway of clathrin-mediated internalization of EGFR. Our studies also demonstrated localization of EGFR signaling complexes in endosomes and the importance of endocytosis for signaling. We have developed novel quantitative methods of analysis of EGFR complexes in living cells and a novel methodology of the functional analysis of EGFR endocytosis using highly efficient RNA interference. These important advances make it now feasible to develop a comprehensive model of how EGFR endocytosis is regulated in cancer cells and how endocytic processes regulate cancerigenesis. In this project we focus on the analysis of head-and-neck cancer (HNC) where EGFR is frequently overexpressed and considered to be an important therapeutic target. The specific aims are: 1) Define the molecular mechanisms of EGFR endocytosis through clathrin coated pits. This aim will, in particular, define the role of ubiquitylation in EGFR endocytosis using novel methods of mass-spectrometry; 2) Test whether new EGFR mutants with impaired endocytic trafficking produce altered patterns of signaling in HNC cells in vitro and affect tumorigenic properties of HNC xenografts in vivo; 3) Test whether altered expression of proteins regulating endocytosis of EGFR and possibly other oncogenic receptor tyrosine kinases affect EGFR signaling in vitro and tumorigenic properties of HNC xenografts in vivo. The successful completion of the aims of the proposal will open new avenues to design of therapeutic and preventive strategies in treatment of EGFR expressing cancers.