EGF SIGNAL TRANSDUCTION AND RADIATION RESPONSE

大量的恶性人类肿瘤含有高水平的 生长因子受体表皮生长因子受体（EGF-R） 已经报道了几种人的过表达或改变的表达， 肿瘤，特别是鳞状细胞癌。我们发现表皮 生长因子（EGF）是鳞状细胞癌（SC）的放射增敏剂 过度表达EGF-R的细胞。我们假设EGF暴露 防止过表达EGF-R的辐射细胞建立一个 通过调节或竞争， 共同的信号通路。 我们将研究重要的生化过程或分子事件 参与EGF信号转导和信号的汇聚 与辐射损伤有关。我们建议确定 EGF诱导的放射增敏作用，通过调查和比较 两种SC细胞系：A431，其被EGF放射增敏，和SiHa， EGF对皮肤没有辐射敏感性。将包括A431细胞（A43 l-R）， 使EGF诱导的放射增敏作用与生长效应分离 EGF在未辐照的A431和SiHa细胞中的初步结果显示， 表面EGF-R密度和程度的显着差异， 蛋白质酪氨酸磷酸化的动力学。我们在辐射中发现 A431细胞认为EGF信号转导与细胞凋亡有一定的汇合点， 经典的辐射诱导的G2期阻滞，以及辐射对 EGF诱导的G1期阻滞我们将扩大这些初步研究， 比较酪氨酸和丝氨酸/苏氨酸的程度和动力学 磷酸化级联反应，特异性丝裂原反应的活性， 激酶，以及特定细胞周期控制活动的变化 EGF诱导的放射增敏作用的分析中的蛋白质 以及同步A431、A431-R和SiHa培养物。候选 放射增敏事件将是那些显著不同于 在细胞系中定量或定性地。 这些研究将提供深入了解信号的基本机制， 引起生化变化和基因表达的变化， EGF与EGF最终，这些信息可能会用于设计 放射增敏策略，利用特定的信号转导 肿瘤细胞中的通路。

A significant number of malignant human tumors contain high levels of growth factor receptors. Epidermal growth factor receptor (EGF-R) overexpression or altered expression has been reported for several human tumors, particularly squamous carcinomas. We discovered that epidermal growth factor (EGF) is a radiation sensitizer of squamous carcinoma (SC) cells that overexpress the EGF-R. We hypothesize that EGF exposure prevents irradiated cells that overexpress the EGF-R from establishing an effective response to radiation-induced damage by modulating or competing for common signaling pathways. We will investigate important biochemical processes or molecular events involved in the convergence of EGF signal transduction and signals associated with radiation damage. We propose to identify components of EGF-induced radiosensitization by investigating and comparing events in two SC cell lines: A431, which is radiosensitized by EGF, and SiHa, which is not radiosensitized by EGF. A431 cells (A43l-R) will be included that allow EGF-induced radiosensitization to be separated from growth effects of EGF. Preliminary results in nonirradiated A431 and SiHa cells show significant differences in surface EGF-R density and the extent and kinetics of protein tyrosine phosphorylation. We have found in irradiated A431 cells that EGF signal transduction has points of convergence with the classical radiation-induced G2 arrest and with the effect of radiation on an EGF-induced G1 arrest. We will extend these preliminary studies and compare the extent and kinetics of tyrosine and serine/threonine phosphorylation cascades, the activities of specific mitogen-responsive kinases, and changes in the activities of specific cell-cycle control proteins in an analysis of EGF-induced radiosensitization in asynchronous and synchronous A431, A431-R, and SiHa cultures. Candidate radiosensitizing events will be those that differ significantly either quantitatively or qualitatively among the cell lines. These studies will provide insight into basic mechanisms of signaling that cause biochemical changes and changes in gene expression in response to radiation and EGF. Ultimately, this information may be used in the design of radiosensitizing strategies that exploit specific signal transduction pathways in tumor cells.