REPAIR OF RADIATION DAMAGE IN VITRO AND VIVO

本研究的目的是了解 在诱导和随后的损伤修复之间 在哺乳动物细胞暴露于电离辐射后的DNA中， 在细胞到组织水平上观察到的放射生物学因素， 被认为对人类癌症放射治疗很重要。 这些 包括细胞恢复机制，O2张力的作用， 辐射时间和辐射敏感性的可能差异 肿瘤细胞和正常细胞之间的差异。 这些方法 测试模型中这些关系的特定方面的问题 系统，最初在体外暴露的DNA修复缺陷细胞中， 然后在小鼠模型肿瘤中进行体内照射。 拟议 研究分为三个具体目标。 一是隔离 并鉴定中国人辐射敏感突变细胞系 仓鼠细胞，使不同的酶途径参与， 可以确定辐射诱导的DNA损伤的修复。 的 维修缺陷的性质将根据 突变株系重新连接单-和双- 链断裂。 DNA水平上的修复差异将是 与线路修复子和 潜在的致命伤害 目标2涉及确定 辐射引起的DNA损伤及其作用的评价 在细胞杀伤中。 炔基和中性基团的新修饰 过滤技术将被用来分析光谱的变化， 在不同氧分压下诱导的损伤，并检查 来自aim 1的用于不同类型修复缺陷的突变系 链断裂。 最后，在目标3中， 增殖和非增殖细胞之间的修复动力学 将在骨髓、睾丸和小鼠中进一步表征 乳腺癌细胞在体内照射 碱性洗脱结合荧光和放射性DNA 测定。 希望这些调查的结果 最终提供有助于改善治疗的知识， 人类癌症的辐射。

The goal of this research is to understand the relationships between the induction and subsequent repair of the lesions produced in DNA after exposure of mammalian cells to ionizing radiation, and radiobiological factors observed at the cell to tissue level which are thought to be important to human cancer radiotherapy. These include cell recovery mechanisms, the role of 02 tension at the time of irradiation, and possible differences in radiosensitivity between tumor cells and normal cells. The approach to these questions testing specific aspects of these relationships in model systems, initially in DNA-repair deficient cells exposed in vitro, and then in mouse model tumors irradiated in vivo. The proposed studies are divided into 3 specific aims. The first is to isolate and characterize radiation-sensitive mutant cell lines of Chinese hamster cells so that the different enzymatic pathways involved in the repair of radiation-induced DNA damage can be determined. The nature of the repair defects will be examined in terms of the relative ability of the mutant lines to rejoin single- and double- strand breaks. Differences in repair at the DNA level will be compared to the ability of the lines to repair sub- and potentially-lethal damage. Aim 2 involves an identification of radiation-induced lesions in DNA and an evaluation of their role in cell killing. New modifications of the alkine and neutral filter techniques will be used to assay changes in the spectrum of lesions induced under different oxygen tensions and examine the mutant lines from aim 1 for defects in repair of different types of strand breaks. Finally, in aim 3, possible differences in repair kinetics between proliferating and non-proliferating cells will be further characterized in bone marrow, testes and mouse mammary adenocarcinoma tumors cells irradiated in vivo using alkaline elution coupled with both fluorometic and radioactive DNA assays. Hopefully, the results of these investigations may ultimately provide knowledge useful for improving the treatment of human cancer by radiation.