Endosomal ErbB Receptor and Src Signaling in Cancer

描述(由申请人提供)：ErbB受体酪氨酸激酶在调节细胞增殖、分化、存活、迁移和分化以及组织内稳态过程中发挥着重要的生理作用，它们的过度表达和/或过度活跃与许多人类癌症的发生直接相关。ErbB受体的激活也启动了细胞保护信号，限制了放射和/或化疗对肿瘤的杀伤程度，而抑制ErbB受体的激活是肿瘤放射和化疗增敏的重要策略。因此，阐明ErbB受体信号的新方面是癌症生物学的主要目标。与ErbB受体结合的配体可诱导迅速内化为内切体，然后进行分选过程，以使其降解或循环利用。更出人意料的是，最近的研究表明，激活的ErbB受体在内化后继续发出信号。信号内体间隔的性质(S)，发生在内体中的特定信号事件，以及调节激活的ErbB受体传递到这些信号间隔的细胞机制仍不清楚。许多实验结果使我们推测，在内体隔室中，Src酪氨酸激酶作为ErbB信号的正调节和/或介体，具有新的作用。 为了验证我们的假设，我们将比较永生化的、非致瘤的人类乳腺上皮细胞(MECs)及其高表达EGFR或ErbB2的同基因衍生物在有或没有Src的情况下，这一模型模拟了这些酪氨酸激酶在乳腺癌和其他癌症中的共同过度表达。我们将首先确定Src是MEC中ErbB受体信号和生物反应的正向调节因子。然后，我们将使用双色成像和生化分析来确定Src和ErbB2在内吞途径中的共存，并确定它们所在的特定隔室。我们将进行分析，以评估内体ErbB受体-Src复合体是否发出信号，并利用Src激酶抑制和内吞体内转运的扰动来确定此类信号的性质及其生物学后果。我们的假设的验证将代表着当前ErbB受体信号传导模式的重大转变，并将为研究Src过度表达与ErbB受体在乳腺癌和其他上皮性癌症中的作用提供新的生化见解。我们的研究可能确定与ErbBand Src过度表达的人类癌症相关的治疗干预的新靶点。

DESCRIPTION (provided by applicant): ErbB receptor tyrosine kinases play essential physiological roles in mediating cell proliferation, differentiation, survival, migration and differentiation during development and tissue homeostasis, and their overexpression and/or hyperactivity are directly linked to oncogenesis in a number of human cancers. ErbB receptor activation also initiates cytoprotective signaling that limits the extent of tumor killing by radiation and/or chemotherapy, and their inhibition represents an important strategy for radio- and chemo-sensitization of tumors. Elucidating novel aspects of ErbB receptor signaling is therefore a major goal in cancer biology. Ligand binding to ErbB receptors induces rapid intemalization into endosomes followed by a sorting process to target them to lysosomal degradation or for recycling. Rather unexpectedly, recent studies have shown that activated ErbB receptors continue to signal after their internalization. The nature of the signaling endosomal compartment(s), the specific signaling events that take place in endosomes, and the cellular mechanisms that regulate the delivery of activated ErbB receptors into these signaling compartments remain unknown. A number of experimental findings lead us to postulate a novel role for Src tyrosine kinase as a positive regulator and/or mediator of ErbB signaling within the endosomal compartment. To test our hypotheses, we will compare immortalized, non-tumorigenic human mammary epithelial cells (MECs) with their isogenic derivatives overexpressing EGFR or ErbB2 with or without Src, which models the co-overexpression of these tyrosine kinases in breast and other cancers. We will first establish that Src is a positive regulator of ErbB receptor signals and biological responses in MECs. We will then use two-color imaging and biochemical analyses to determine the colocalization of Src and ErbB2 within the endocytic pathway, and identify the specific compartment in which they reside. We will carry out analyses to assess if endosomal ErbB receptor-Src complexes signal and determine the nature of such signals and their biological consequences, using Src kinase inhibition and perturbations of transport within the endocytic compartments. Validation of our hypotheses will represent a major shift in the current paradigm of ErbB receptor signaling, and will provide novel biochemical insights into the role of Src overexpression together with ErbB receptors in breast and other epithelial cancers. Our studies may identify novel targets for therapeutic intervention relevant to ErbBand Src-overexpressing human cancers.