Endosomal ErbB Receptor and Src Signaling in Cancer

描述（由申请人提供）：ErbB受体酪氨酸激酶在发育和组织稳态过程中介导细胞增殖、分化、存活、迁移和分化中发挥重要的生理作用，并且它们的过表达和/或过度活性与许多人类癌症中的肿瘤发生直接相关。ErbB受体激活还启动细胞保护信号传导，其限制通过放射和/或化学疗法杀死肿瘤的程度，并且它们的抑制代表肿瘤的放射和化学敏化的重要策略。因此，阐明ErbB受体信号转导的新方面是癌症生物学的主要目标。与ErbB受体结合的配体诱导快速内化到内体中，随后进行分选过程以使其靶向溶酶体降解或再循环。令人意外的是，最近的研究表明，激活的ErbB受体在内化后继续发出信号。信号传导内体隔室的性质、内体中发生的特定信号传导事件以及调节活化的ErbB受体递送到这些信号传导隔室中的细胞机制仍然未知。许多实验结果使我们假设Src酪氨酸激酶作为ErbB信号传导的正调节剂和/或介导剂在内体隔室中的新作用。 为了验证我们的假设，我们将比较永生化的非致瘤性人乳腺上皮细胞（MEC）与其过表达EGFR或ErbB 2（有或无Src）的同基因衍生物，其模拟了这些酪氨酸激酶在乳腺癌和其他癌症中的共过表达。我们将首先建立Src是一个积极的ErbB受体信号和生物反应的MEC调节器。然后，我们将使用双色成像和生化分析，以确定共定位的Src和ErbB 2内吞途径，并确定它们所在的特定隔室。我们将进行分析，以评估是否内体ErbB受体-Src复合物的信号，并确定这些信号的性质及其生物学后果，使用Src激酶抑制和内吞隔室内的运输扰动。验证我们的假设将代表ErbB受体信号传导的当前范式的重大转变，并将提供新的生化见解Src过表达与ErbB受体在乳腺癌和其他上皮癌中的作用。我们的研究可能会确定新的目标，为相关的ErbBand Src过表达的人类癌症的治疗干预。

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.