Mechanisms of Chemo/Radioresistance in Human Gliomas

描述(由申请人提供)：恶性胶质瘤是人类肿瘤中最难治愈、最耐化疗和耐放射的肿瘤之一。在以前的研究中，我们和其他人证实了多功能生长因子(SF/HGF)及其受体c-Met在人脑胶质瘤中的表达随着肿瘤从低级别向恶性发展而显着增加。我们发现，SF/HGF在体外可保护人胶质母细胞瘤细胞免受DNA损伤剂的细胞毒作用，在体内可保护辐射诱导的胶质瘤细胞凋亡。我们已经证实，SF/HGF激活c-Met的细胞保护/抗凋亡作用部分是通过PI3-激酶--&GT；AKT第二信使途径实现的。更多下游或平行的信号通路、基因表达和生化效应在人脑胶质瘤对SF/HGF的细胞保护和抗凋亡反应中的参与尚不清楚。这项应用旨在确定SF/HGF刺激人胶质母细胞瘤细胞化疗和放射耐药的特定分子途径。目的1筛选新的差异表达基因产物，参与SF/HGF介导的胶质瘤细胞保护作用。我们将证实和扩展我们的研究，初步揭示了SF/HGF诱导的胶质瘤细胞特异性基因表达在细胞保护机制中的作用。目的研究DNA损伤诱导人脑胶质瘤细胞凋亡的生化效应机制及SF/HGF对其的抑制作用。我们将集中于鞘磷脂信号、死亡受体信号、线粒体损伤、caspase以及caspase激活的调节因子-IAPs和Smac。目的#3将研究SF/HGF介导的胶质瘤细胞保护的转录调节因子。我们将确定SF/HGF如何改变转录因子激活/磷酸化、核转位、DNA结合和基因表达，并确定特定转录因子在SF/HGF介导的细胞保护和AIMS#1和#2中发现的其他分子/生化抗凋亡终点中的作用。AIM#4将确定抑制内源性自分泌SF/HGF：C-Met信号或其下游抗凋亡效应是否增强了AIMS#1-3中确定的人胶质瘤异种移植瘤对放射和/或化疗的治疗反应。这些研究将确定人类胶质瘤化疗和放射耐药的机制，确定加强脑瘤细胞毒治疗的新方法。

DESCRIPTION (provided by applicant): Malignant gliomas are among the least curable and most chemo- and radioresistant of human tumors. In prior studies we and others established that expression of the multifunctional growth factor (SF/HGF) and its receptor c-Met in human gliomas increases significantly with tumor progression from low grade to malignant. We have found that SF/HGF protects human glioblastoma cells from cytotoxicity induced by DNA-damaging agents in vitro and protects against radiation-induced glioma cell apoptosis in vivo. We have established that the cytoprotective/anti-apoptotic action of c-Met activation by SF/HGF occurs, in part, through the PI3-kinase--> AKT second messenger pathway. The involvement of more downstream or parallel signaling pathways, gene expression, and biochemical effectors in the human glioma cytoprotective and anti-apoptotic response to SF/HGF remain unknown. This application proposes to identify specific molecular pathways through which SF/HGF stimulates chemo- and radio resistance in human glioblastoma cells. Aim #1 will identify novel differentially expressed gene products involved in SF/HGF-mediated cytoprotection of glioma cells. We will confirm and expand on our studies that have preliminarily implicated glioma cell- specific patterns of SF/HGF-induced gene expression in the cytoprotective mechanism. Aim #2 will determine the biochemical effector mechanisms of DNA damage-induced apoptosis and their inhibition by SF/HGF in human glioma cells. We will focus on sphingolipid signaling, death receptor signaling, mitochondrial damage, caspases and the regulators of caspase activation - IAPs and SMAC. Aim #3 will examine transcriptional regulators of SF/HGF-mediated glioma cell protection. We will determine how SF/HGF alters transcription factor activation/phosphorylation, nuclear translocation, DNA binding, and gene expression and determine the role of specific transcription factors in SF/HGF-mediated cytoprotection and other molecular/biochemical anti-apoptotic endpoints found in Aims #1 and #2. Aim #4 will determine if inhibiting endogenous autocrine SF/HGF:c-Met signaling or its downstream anti-apoptotic effectors identified in Aims #1-3 enhances the therapeutic response of human glioma xenografts to radiation and/or chemotherapy. These studies will determine mechanisms of human glioma chemo-and radio resistance identify new approaches to enhancing brain tumor cytotoxic therapy.