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以治愈和最具化疗和放射抗性的肿瘤之一。在之前的研究中，我们和其他人发现，随着肿瘤从低度向恶性发展，多功能生长因子（SF/HGF）及其受体c-Met在人类胶质瘤中的表达显著增加。我们发现SF/HGF在体外可保护人胶质瘤细胞免受dna损伤剂诱导的细胞毒性，在体内可保护辐射诱导的胶质瘤细胞凋亡。我们已经确定，SF/HGF活化c-Met的细胞保护/抗凋亡作用部分通过pi3 -激酶-> AKT第二信使通路发生。更多的下游或平行信号通路、基因表达和生化效应在SF/HGF对人类胶质瘤细胞保护和抗凋亡反应中的参与尚不清楚。该应用旨在确定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将鉴定参与SF/ hgf介导的胶质瘤细胞保护的新型差异表达基因产物。我们将证实和扩展我们的研究，初步暗示胶质瘤细胞特异性模式的SF/ hgf诱导的基因表达在细胞保护机制中。目的2将确定DNA损伤诱导细胞凋亡的生化效应机制以及SF/HGF对人类胶质瘤细胞的抑制作用。我们将重点关注鞘脂信号，死亡受体信号，线粒体损伤，半胱天冬酶和半胱天冬酶激活的调节因子- 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、核易位、DNA结合和基因表达，并确定特定转录因子在SF/HGF介导的细胞保护和其他在Aims #1和#2中发现的分子/生化抗凋亡终点中的作用。Aim #4将确定是否抑制内源性自分泌SF/HGF:c-Met信号或其下游抗凋亡效应物在Aims #1-3中发现增强人类胶质瘤异种移植物对放疗和/或化疗的治疗反应。这些研究将确定人类胶质瘤的化学机制，并确定增强脑肿瘤细胞毒性治疗的新方法。

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.