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

存在显著百分比的缺氧细胞（10 - 25%） 在动物和人类肿瘤中， 放疗和化疗。 虽然缺氧分数在 动物肿瘤常随体积增大，无肿瘤特征 例如组织学、大小体积倍增时间、生长部位或 已经发现分化程度可以预测 在人肿瘤中缺氧细胞或缺氧部分的存在。 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 通过允许放射治疗和 化疗应根据患者的特点进行个体化 每个病人的肿瘤。 辐射诱发的有两类 DNA损伤，其形成表现出类似于 辐射诱导的细胞杀伤。 O2依赖性 DNA-蛋白质交联（DPC）的形成实际上是 辐射诱导细胞杀伤的O2依赖性图像。 的 辐射诱导的DNA链断裂（SB）的形成具有O2 依赖性几乎与辐射的O2依赖性相同- 诱导细胞死亡。 这两种现象都会导致 在碱性洗脱过程中从过滤器中去除DNA。 后 给定洗脱体积，保留在过滤器上的DNA量为 与缺氧细胞的百分比呈线性相关， 辐照组织。 本研究的目标是：1）确定 SB和DCPC的碱性洗脱试验可以可靠地测量 小鼠和人肿瘤的缺氧分数，2）提供数据， 正确选择辐射剂量和采样程序， 使用该测定的动物和人体试验，以及3）表征 通过该DNA测定测量的DPC的化学性质和位置 作为O2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种人结肠肿瘤（克隆A， HCT-15，WiDR）在裸鼠中作为异种移植物生长， 实现这些目标。 所处DPC的化学性质 在核基质附近或染色质中， 采用GC/MSD技术。 如果，1）SB和DPC的诱导是 受生物和生理因素影响最小 比染色质附近的O2浓度，以及2）测定 可靠地预测实验小鼠的缺氧分数， 人类肿瘤，研究将开始在临床上测试其 在预测头颈部放射反应中的作用 肿瘤或宫颈癌，并在实验室中验证 检测和定量缺氧细胞的非侵入性技术 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.