癌症化放联合治疗中低能电子对DNA多重损伤的机制研究

Improving cancer therapy is a significant social, economic and scientific issue in public health. Owing to basic research by the applicant and other groups, it has been shown that in Radiotherapy the secondary low energy electrons (LEE), which are major initial products of high energy radiation, can interact strongly and destructively within subcellular ranges with the DNA of cancer cells, effectively breaking its chemical bonds, leading to complex damages and cell death. Despite these advances, the most detrimental damages induced by LEE during radiotherapy are still unidentified. Modification of LEE-DNA interactions and numbers provides a novel strategy to effectively promote nanoscale magnification of radiation damage in cancer cells. Hence, the objective of the proposed research is to understand the mechanisms of these most detrimental damages occuring in irradiated living cells, to serve as guideline in the optimization of cancer radiotherapy and chemoradiation therapy (CRT). Clustered lesions will be analysed in real time under vacuum by techniques of micro-analysis and surface physics, and ex-vacuo, with DNA repair enzymatic treatment, HPLC, LC/MS, sequencing and conformal gel electrophoresis, to obtain the energy dependence of effective yields. Enhancement of clustered DNA damages by the presence of fluorouracil, platinum-chemotherapeutic agents and radiosensitizing gold nanoparticles will be investigated. This project has the potential for the fabrication of novel radiosensitizers, as well as the achievement of more efficient CRT protocols, from understanding the synergy mechanisms between drugs and radiation, so as to optimize primary DNA damages and patient treatment.

如何提高癌症治疗效率是有关公共健康的重大科学问题。前期研究显示在放射治疗中高能电离辐射产生的大量低能电子（LEE）能高效导致DNA化学键破坏，并引发难以修复多重损伤的发生。但这些LEE造成的破坏性损伤还未被检测和系统研究。本课题拟从纳米尺度调控LEE与DNA作用的全新角度，通过LEE导致细胞DNA最致命多重损伤的理解，揭示增强肿瘤细胞死亡的有效途径，以期获得目前最广泛使用癌症化放联合治疗（CRT）最优临床治疗方案的制定指南。采用真空内表面物理实时微分析监测以及真空外的细胞修复酶、HPLC、LC/MS、测序电泳等方法，系统分析DNA多重损伤种类、电子产率和能量关系；考察氟脲嘧啶、铂类化疗药物和金纳米粒子对多重损伤的辐射增强因子，阐明典型辐射致敏剂化放协同作用机制。该研究对分子水平上揭示电离辐射-药物对有机体有效损伤的作用机制、指导新型辐射致敏剂的设计具有重要的理论和实际意义。

由电离辐射产生的大量低能电子之作用机制是理解辐射初始过程和辐射生物学的重要课题。化放联合治疗（CRT）作为最主要的癌症治疗手段，其协同作用机制不明是阻碍其治疗效率提高的瓶颈问题。课题从纳米尺度调控低能电子与DNA作用的全新角度出发，成功建立了低能电子与生物分子作用、损伤分析的实验系统；获得了1-20eV电子对DNA和顺铂-DNA复合物的各种损伤量子产率-能量关系；阐明了单个电子导致DNA多重损伤的本质机理；在分子水平上揭示了单个电子导致铂类化疗药物-DNA复合物多重损伤的辐射增敏协同作用机制。通过对低能电子导致细胞最致命DNA多重损伤的本质理解，揭示了高能电离辐射增强肿瘤细胞死亡的有效途径，阐明铂类化疗药物在化放联合治疗中的分子协同作用机制。研究在分子水平上提供了电离辐射-药物联合作用导致DNA有效损伤产率、增强因子的重要数据，对指导、制定高效化放联合治疗的临床应用，开发、设计新型铂化疗药物和辐射致敏剂等都具有重要的理论意义和应用价值。