RADIOSENSITIVITY OF HUMAN GLIOMAS

除了手术，放射治疗是治疗恶性肿瘤最有效的方法。 脑瘤 尽管如此，约20%的多形性胶质母细胞瘤（GBM）进展 在放射治疗过程中，这表明这些病变是 抗辐射。 使用手术中获得的组织，我们将 开发用于识别这些肿瘤的实验室方法，并将 量化他们对辐射的反应 哺乳动物的辐射敏感性 在实验室中通过测量细胞杀伤来确定细胞的存活率。 然而，在这方面， 对于原发性肿瘤组织，这种方法存在问题，因为低 电镀效率和由此产生的选择研究一个非常小的 原始肿瘤细胞群的分数。 尝试开发 以脑肿瘤细胞存活率为终点的预测性分析， 失败. 我们认为，关键是要确定其他 定量测量可用于预测肿瘤对辐射的反应 疗法 我们建议评估固有的辐射反应的方法 更适合用于原发性肿瘤样本：DNA双链测定 脉冲场凝胶电泳显示链断裂; NA超螺旋变化 通过类核晕测定;和测量染色体断裂， 使用荧光原位杂交技术进行交换。 我们将 使用彗星试验测定所选肿瘤中的缺氧分数。 我们 将确定这些检测中的哪一个提供相关信息 关于人类脑肿瘤细胞的辐射反应，并建立 预测分析。 由于研究辐射敏感性的固有问题， 在自然环境之外的肿瘤中，我们将研究 低剂量放射治疗恶性脑肿瘤的可行性 术中能量X射线源，并间隔采集组织， 测量DNA损伤和修复以及肿瘤缺氧。 这可能是理想的 研究单个肿瘤对辐射敏感性的方法。 我们 具体目标是：1）确定最佳实验条件， 定量检测人脑肿瘤DNA损伤修复和缺氧分数 作为异种移植物模型生长的组织; 2）确定哪种测定 目的1中研究的结果显示，作为一种预测性试验， 异种移植模型中的体内辐射反应性; 3）测量DNA 新鲜GBM中的损伤和修复以及染色体断裂和交换 使用所选检测试剂盒的最佳条件检测样本; 4） 研究在手术中照射人脑肿瘤的可行性 允许能量X射线源和收获肿瘤组织用于分析 缺氧分数和DNA损伤和修复;以及，5）将缺氧分数与DNA损伤和修复相关联。 目标3中获得的结果，肿瘤的BUdR标记指数和 潜在倍增时间，遗传畸变，DNA修复活性 酶O/6-AT，并具有既定的临床预后指标，以及 放射治疗结果的临床测量。

Next to surgery, radiation is the most effective treatment for malignant brain tumors. Nonetheless, -20% of glioblastoma multiforme (GBM) progress during the course of radiation therapy, suggesting that these lesions are resistant to radiation. Using tissues obtained during surgery, we will develop laboratory methodologies for identifying these tumors, and will quantify their response to radiation. Radiation sensitivity of mammalian cells is determined in the laboratory by measuring cell killing. However, for primary tumor tissue this approach is problematic because of low plating efficiencies and the resultant selection for study of a very small fraction of the original tumor cell population. Attempts to develop predictive assays based on brain tumor cell survival as the end-point have failed. We believe that it is crucial to determine whether other quantitative measures can be used to predict tumor response to radiation therapy. We propose to assess intrinsic radiation response with methods more suitable for use in primary tumor samples: measurement of DNA double strand breaks by pulsed field gel electrophoresis; NA supercoiling changes by the nucleoid halo assay; and measurement of chromosomal breaks and exchanges using fluorescence in situ hybridization techniques. We will determine hypoxic fraction in selected tumors using the comet assay. We will determine which of these assays provides relevant information regarding the radiation response of human brain tumor cells and establish predictive assays. Because of the problems inherent in studying radiation sensitivity of explanted tumors outside of their natural milieu, we will study the feasibility of irradiating malignant brain tumors in situ with a low energy X-ray source intraoperatively and harvesting tissue at intervals to measure DNA damage and repair and tumor hypoxia. This may be the ideal way to study the individual tumor's sensitivity to radiation. Our specific aims are: 1) to define the optimal experimental conditions to quantify DNA damage and repair and hypoxic fraction in human brain tumor tissue grown as a xenograft model; 2) to determine which of the assays studied in Aim 1 show(s) the most promise as a predictive assay for in vivo radiation responsiveness in xenograft models; 3) to measure DNA damage and repair and chromosome breaks and exchanges in fresh GBM specimens using optimal conditions for the chosen assay(s); 4) to investigate the feasibility of irradiating human brain tumors at surgery with allow energy X-ray source and harvesting tumor tissue for assays of hypoxic fraction and DNA damage and repair; and, 5) to correlate the results obtained in Aim 3 with the tumor's BUdR labeling index and potential doubling time, genetic aberrations, activity of the DNA repair enzyme O/6-AT, and with established clinical indicators of prognosis, and clinical measures of radiation therapy outcome.