CHARACTERIZATION OF FGF SIGNALING IN PITUITARY CELLS

成纤维细胞生长因子（FGFs）及其受体在包括垂体、子宫内膜和乳腺在内的多种组织中肿瘤的形成和发展中起着关键作用。FGFs也是肿瘤生长和转移的重要调节因子。然而，令人惊讶的是，关于FGF信号转导途径的分子机制和成分知之甚少。由于迄今为止表征的FGF反应通常涉及诱导细胞增殖或分化，因此缺乏方便、快速和生理相关的检测方法，阻碍了FGF信号传导介质的表征。我们的实验室已经开发了一个优秀的模型系统，用于定义和表征FGF信号和基因表达调控。该模型系统利用外源性导入垂体肿瘤细胞的促生长因子反应性催乳素启动子。使用该系统的初步结果表明，FGF信号转导涉及蛋白激酶C （PKC）和丝裂原活化蛋白激酶（MAPK），但令人惊讶的是，不涉及正常的上游活化因子MAPK， Ras和Raf-1。我计划使用这个独特的系统来继续表征FGF信号转导的细胞质成分。瞬时转染方法，使用显性阴性、抑制性或活性形式的信号分子，以及药理学抑制剂，将被用来描述FGF向催乳素启动子信号传导的成分。明确FGF信号转导的基本分子机制，将为分析FGF信号转导在乳腺癌、子宫内膜癌等其他肿瘤中的作用提供重要基础。此外，对FGF信号通路成分的阐明可能会导致多种癌症的新诊断或预后标记物的鉴定，以及治疗干预的新潜在靶点。

Fibroblast growth factors (FGFs) and their receptors play a critical role in the formation and progression of tumors in a variety of tissues including pituitary, endometrial, and breast. FGFs are also important regulators of neoplastic growth and metastasis. However, surprisingly little is known about the molecular mechanisms and components of the FGF signal transduction pathway. Characterization of the mediators of FGF signaling has been hampered by the lack of a convenient, rapid and physiologically relevant assay since FGF responses characterized to date have typically involved induction of cellular proliferation, or differentiation. Our lab has developed an excellent model system with which to define and characterize FGF signaling and regulation of gene expression. This model system utilizes an FGF-responsive prolactin promoter exogenously introduced into pituitary tumor cells. Preliminary results using this system indicate that FGF signal transduction involves protein kinase C (PKC) and the mitogen-activated protein kinases (MAPK), but surprisingly, does not involve the normal upstream activators of MAPK, Ras and Raf-1. I plan to use this unique system to continue characterizing the cytoplasmic components of FGF signal transduction. A transient transfection approach, using dominant-negative, inhibitory or active forms of signaling molecules, and pharmacological inhibitors will be used to delineate components of FGF signaling to the prolactin promoter. Characterization of the basic molecular mechanisms of FGF signal transduction will provide an important foundation for analyzing the contribution of FGF signal transduction in other cancers such as breast and endometrial cancer. Furthermore, elucidation of the components of the FGF signaling pathway may lead to the identification of novel diagnostic or prognostic markers for a variety of cancers and new potential targets for therapeutic intervention.