Mechanisms of Chemo/Radioresistance in Human Gliomas

描述（由申请人提供）：恶性神经胶质瘤是人类肿瘤中最难治愈且最耐化疗和放射的肿瘤。在先前的研究中，我们和其他人确定了多功能生长因子（SF/HGF）及其受体c-Met在人类胶质瘤中的表达随着肿瘤从低级别进展到恶性而显著增加。我们已经发现SF/HGF在体外保护人胶质母细胞瘤细胞免受DNA损伤剂诱导的细胞毒性，并且在体内保护免受辐射诱导的胶质瘤细胞凋亡。我们已经确定SF/HGF激活c-Met的细胞保护/抗凋亡作用部分通过PI 3-激酶-> AKT第二信使途径发生。更多的下游或平行的信号通路，基因表达和生化效应物参与SF/HGF对人脑胶质瘤的细胞保护和抗凋亡反应仍然未知。本申请提出鉴定SF/HGF通过其刺激人胶质母细胞瘤细胞中的化疗和放射抗性的特定分子途径。目的#1将鉴定参与SF/HGF介导的胶质瘤细胞保护作用的新的差异表达基因产物。我们将证实并扩展我们的研究，初步暗示胶质瘤细胞特异性模式的SF/HGF诱导的基因表达的细胞保护机制。目的#2将确定DNA损伤诱导的凋亡的生化效应机制和SF/HGF对人脑胶质瘤细胞的抑制作用。我们将重点讨论鞘脂信号，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剂-IAP和SMAC。目的#3将检查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如何改变转录因子活化/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介导的细胞保护和目标#1和#2中发现的其他分子/生化抗凋亡终点中的作用。目的#4将确定抑制内源性自分泌SF/HGF：c-Met信号传导或目的#1-3中鉴定的其下游抗凋亡效应物是否增强人胶质瘤异种移植物对放射和/或化学疗法的治疗反应。这些研究将确定人脑胶质瘤化学和放射抗性的机制，确定加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.