MOLECULAR MECHANISMS OF HEAT-INDUCED RADIOSENSITIZATION

热疗越来越多地与放射治疗相结合。 治疗人类的恶性肿瘤。将这两者结合起来的基本原理 治疗癌症的临床方案的模式取决于 观察到热能优先杀死对辐射敏感的细胞 能抵抗单独的辐射。对分子的解释 热放射增敏的潜在机制(S)可能提供信息 对开发这种联合治疗方案很有用。《长河》 因此，本提案的长期目标是确定 热诱导现象背后的分子过程 放射增敏并阐明其作用机制(S)。中环 这一建议所依据的假设是热使细胞对 增加DNA双链转化几率的辐射 断裂(DSB)致死的染色体异常。中的增强 DNADSB转化为染色体异常的概率假设为 是由染色质结构和功能的改变引起的，已知 在急性暴露于高温后发生，和/或通过减少 修复的功效。染色质结构和功能的改变， 用来解释辐射前照射引起的放射增敏 在43-45.5摄氏度的高温下，可能会导致结构不稳定 辐射后的DNA分子，或导致可获得性降低 辐射诱导DNA DSB修复酶导致 残留的染色体损伤。修复系统的有效性降低 主要用来解释辐射后暴露的放射增敏作用 加热至41-43摄氏度。 DNADSB在热放射增敏中的重要性将通过 对辐射敏感的突变体显示修复损伤的能力降低， 而DNA DSB转化为染色体损伤的变化将 一方面，通过测量DNA DSB的诱导和修复来评估 使用不解卷过滤洗脱技术或脉冲场凝胶 另一方面，染色体的诱导和修复 应用早熟染色体技术对间期细胞的损伤 冷凝(PCC)。具体地说，将进行试验，以 CHO辐射敏感突变体的热辐射增敏研究 (XRS-5)和V-79(IRS-1，IRS-2，IRS-3)细胞表现出不同的能力 修复DNA DSB，在细胞水平上观察到的效果将是 与修复缺陷的程度和效果有关 对DNA和染色体修复的影响。此外，实验将是 对维修人员进行热辐射增敏调查 细胞，并关联热对诱导的影响，特别是 DNA(DSB)和染色体辐射损伤的修复。 所获得的结果有望评估DNA DSB在 热辐射增敏现象与将其结合起来构建 这一现象背后的分子过程模型。

Hyperthermia is increasingly used in conjunction with radiotherapy for the treatment of human malignancy. The rationale for combining these two modalities in clinical protocols for the treatment of cancer rests on the observation that heat radiosensitizes and kills preferentially cells that are resistant to radiation alone. Elucidation of the molecular mechanism(s) underlying heat radiosensitization might provide information useful in the development of such combined treatment protocols. The long term objective of the present proposal is, therefore, to identify the molecular processes that underlie the phenomenon of heat induced radiosensitization and to elucidate the mechanism(s) involved. The central hypothesis on which this proposal rests is that heat sensitizes cells to radiation by increasing the probability of conversion of DNA double strand breaks (dsb) to lethal chromosome aberrations. The enhancement in the conversion probability of DNA dsb to chromosome aberrations is assumed to be caused either by alterations in chromatin structure and function, known to occur after acute exposures to heat, and/or by a reduction in the efficacy of repair. Alterations in chromatin structure and function, invoked to explain radiosensitization induced by pre-irradiation exposure to heat at 43-45.5 degrees C, may lead either to structural instability of irradiated DNA molecules, or to a decrease in the accessibility of radiation induced DNA dsb to repair enzymes that results in an increase in residual chromosome damage. Reduction in the efficacy of the repair system is mainly invoked to explain radiosensitization by postirradiation exposure to heat at 41-43 degrees C. The importance of DNA dsb in heat radiosensitization will be evaluated with radiation sensitive mutants showing reduced ability to repair this lesion, whereas alterations in the conversion of DNA dsb to chromosome damage will be assessed by measuring, on the one hand, induction and repair of DNA dsb using the non-unwinding filter elution technique or pulse field gel electrophoresis and, on the other hand, induction and repair of chromosome damage in interphase cells using the technique of premature chromosome condensation (PCC). Specifically, experiments will be carried out to investigate heat radiosensitization in radiation sensitive mutants of CHO (xrs-5) and V-79 (irs-1, irs-2, irs-3) cells that show different ability to repair DNA dsb, and the effect observed at the cell level will be correlated with the degree of repair deficiency as well as with the effect of heat on DNA and chromosome repair. Furthermore, experiments will be carried out to investigate heat radiosensitization in repair proficient cells and to correlate the effect of heat on the induction and particularly on the repair of radiation damage in the DNA (dsb) and the chromosomes. The results obtained are expected to evaluate the importance of DNA dsb in the phenomenon of heat radiosensitization and will be combined to construct models of the molecular processes underlying this phenomenon.