GAMMA RAY-INDUCED DNA DAMAGE--DETECTOR OF HYPOXIC CELLS

存在相当大比例的低氧细胞(10-25%) 在动物和人类中，肿瘤可以影响两者的结果 放射治疗和化疗。虽然低氧组分中 动物肿瘤常随体积增大而增大，无肿瘤特征 例如组织学、体积倍增时间、生长部位或 研究发现，分化程度可以预测 在人类肿瘤中存在低氧细胞或低氧部分。 因此，一种快速、准确的检测和定量方法 人类肿瘤中的低氧细胞可能会对 癌症的治疗通过允许放射治疗和 化疗要根据患者的特点进行个体化 每个病人的肿瘤。有两种类型的辐射诱导 DNA损伤，其形成表现出类似于 用于辐射诱导的细胞杀伤。对氧气的依赖 DNA-蛋白质交联(DPC)的形成实际上是一面镜子 辐射诱导的细胞死亡依赖氧气的图像。这个 辐射诱导的DNA链断裂(SBS)的形成有O2 对辐射的依赖与对氧气的依赖几乎相同- 诱导细胞杀伤。这两种现象都会导致大脑发育迟缓。 在碱性洗脱过程中从过滤器中去除DNA。在.之后 给定洗脱液的体积，过滤器上剩余的DNA量为 与低氧细胞所占的百分比呈线性关系 受辐射的组织。 拟议研究的目标是：1)确定是否存在 碱洗脱法可以可靠地测定SBS和DCPC 小鼠和人肿瘤的低氧组分，2)为 适当选择辐射剂量和采样程序 使用这种分析方法的动物和人体试验，以及3)表征 DNA测定法测定的DPC的化学性质和位置 作为氧气浓度、代谢状态、 增殖状态和辐射暴露之间的时间。三 小鼠肿瘤(RIF、SCCVII、KHT)和3例人结肠肿瘤(克隆A、 HCT-15，WiDR)作为裸鼠移植瘤生长，将用于 实现这些目标。DPC的化学性质位于 在核基质附近或在染色质中将被确定 使用GC/MSD技术。IF，1)SBS和DPC的诱导 受生物和生理因素的影响最小 而不是染色质附近的O2浓度，以及2)检测 可靠地预测实验小鼠的低氧分数和 人类肿瘤的研究将在临床上开始，以测试其 预测头颈部放射反应的价值 肿瘤或宫颈癌，并在实验室进行验证 缺氧细胞的非侵入性检测和定量技术 在肿瘤和正常组织中。

The presence of a significant percentage of hypoxic cells (10-25%) in animal and human tumors can influence the outcome of both radiotherapy and chemotherapy. Although the hypoxic fraction in animal tumors often increases with size, no tumor characteristic such as histology, size volume doubling time, site of growth, or degree of differentiation has been found to predict either the presence of hypoxic cells or the hypoxic fraction in human tumors. Thus, a rapid, accurate method for detecting and quantitating hypoxic cells in human tumors could make a substantial impact on the treatment of cancer by allowing both radiotherapy and chemotherapy to be individualize based on he characteristics of each patient's tumor. There are two classes of radiation-induced DNA damage whose formation exhibits an oxygen dependency similar to that for radiation-induced cell killing. The O2 dependency for formation of DNA-protein crosslinks (DPCs) is virtually the mirror image of the O2 dependency for radiation-induced cell kill. The formation of radiation-induced DNA strand breaks (SBs) has an O2 dependency virtually identical to the O2 dependency for radiation- induced cell kill. Both phenomena lead to a retardation in the removal of DNA from the filter during alkaline elution. After a given volume of elution, the amount DNA remaining on the filter is linearly related to the percentage of hypoxic cells in the irradiated tissue. The goals of the proposed research are to: 1) determine if an alkaline elution assay for SBs and DCPCs can reliably measure the hypoxic fraction of mouse and human tumors, 2) provide the data to properly select the radiation dose and sampling procedures for animal and human trials using this assays, and 3) characterize the chemical nature and location of the DPCs measured by this DNA assay as a function of the O2 concentration, metabolic state, proliferative state and time between radiation exposures. Three mouse tumors (RIF, SCCVII, KHT) and 3 human colon tumors (clone A, HCT-15, WiDR) grown as xenografts in nude mice will be used to achieve these objectives. The chemical nature of the DPCs located near the nuclear matrix or in the chromatin will be determined using GC/MSD techniques. If, 1) induction of SBs and DPCs is minimally influenced by biological and physiological factors other than the O2 concentration near the chromatin, and 2) the assay reliably predicts the hypoxic fraction of experimental mouse and human tumors, studies will be started in the clinic to test its usefulness in predicting the radiation responded of head and neck tumors or cervical carcinoma, and in the lab to validate noninvasive techniques for detecting and quantitating hypoxic cells in tumors and normal tissue.