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，人们对成纤维细胞生长因子信号转导通路的分子机制和成分知之甚少。由于到目前为止，成纤维细胞生长因子的反应通常包括诱导细胞增殖或分化，因此缺乏一种方便、快速和生理上相关的检测方法，阻碍了对成纤维细胞生长因子信号转导介质的表征。我们的实验室已经开发了一个很好的模型系统，用来定义和表征成纤维细胞生长因子信号和基因表达的调控。该模型系统利用外源导入垂体瘤细胞的成纤维细胞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，成纤维细胞生长因子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，不涉及正常上游的MAPK、RAS和Raf-1激活物。我计划使用这个独特的系统来继续表征成纤维细胞生长因子信号转导的细胞质成分。使用显性-负性、抑制性或活性形式的信号分子和药物抑制剂的瞬时转染法将被用来描述向催乳素启动子传递信号的成纤维细胞生长因子的成分。研究成纤维细胞生长因子信号转导的基本分子机制将为分析成纤维细胞生长因子信号转导在乳腺癌、子宫内膜癌等其他肿瘤中的作用提供重要基础。此外，阐明成纤维细胞生长因子信号通路的组成可能导致识别各种癌症的新的诊断或预后标记物，以及新的治疗干预的潜在靶点。

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.