Effect of repair gene inhibitor with radiation on tumor cells

采用染色体早凝技术（PCC）和荧光原位杂交技术（FISH）研究了ATM和NBS1在辐射诱导DNA损伤修复中的作用。众所周知，ATM和NBS1在细胞周期检查点控制中都起着重要作用，由于缺乏这种功能，AT和NBS1缺陷细胞被认为对电离辐射高度敏感。在非生长的G0期，AT和NBS1细胞对辐射非常敏感。为了理解这一机制，我们研究了G0和G1条件下的染色体畸变。我们使用的细胞有正常人成纤维细胞、ATM缺陷细胞、NBS1缺陷细胞和人骨肉瘤细胞。将未生长的细胞辐照后立即进行修复或传代培养，发现正常成纤维细胞、NBS1细胞和肿瘤细胞的存活率均高于直接镀膜条件。为了进一步研究修复的效率和保真度，在G0和G1细胞上应用了PCC和FISH技术。正常成纤维细胞和肿瘤细胞在G0条件下的修复保真度明显高于G1条件，而AT细胞在两种细胞生长条件下的修复保真度相似。G0条件下NBS1细胞的保真度较高，但精度低于正常细胞。当细胞被ATM抑制剂预处理时，在正常细胞中观察到类似AT细胞的现象。由于G1和G0细胞通过非同源末端连接修复双链断裂，ATM似乎具有修复NHEJ保真度的功能。我们研究了重离子束对PLDR的影响。结果发现，即使是正常细胞，G0和G1之间的修复保真度也表现出相似的不准确。结果表明，即使在G0条件下，高let诱导的DNA损伤也不能准确修复。抑制G0肿瘤细胞的ATM和NBS1可能导致更多的肿瘤细胞死亡。进一步的小鼠研究正在进行中。少

We have studied the function of ATM and NBS1 on the repair of radiation-induced DNA damage by using the technique of premature chromosome condensation (PCC) and the fluorescence in situ hybridization (FISH). It is known that both ATM and NBS1 have important roles on cell cycle checkpoint control and, due to the lack of this function, AT and NBS1 deficient cells are thought to be hyper-sensitive to ionizing radiation. It is also demonstrated that AT and NBS1 cells are very radio-sensitive under non-growing G0 phase. To understand this mechanism we have studied chromosome aberrations under G0 and G1 conditions. The cells we used are normal human fibroblast cells, ATM deficient cells, NBS1 deficient cells and human osteosarcoma cells. When non growing cells were irradiated and either allowed to repair or subculture immediately after irradiation, it was found that normal fibroblast cells, NBS1 cells and tumor cells showed higher survival rate compared to immediate plating condition. To stu … More dy the efficiency and the fidelity of repair, PCC and FISH technique were applied on G0 and G1 cells. The normal fibroblast cells and tumor cells showed much higher fidelity under G0 condition compared to G1 growing condition, whereas AT cells show similar low fidelity of repair under each cell growth condition. NBS1 cells showed more fidelity under G0 condition but less accurate than normal cells. Similar phenomena like AT cells were observed in normal cells when cells when cells were pretreated with ATM inhibitor. Since G1 and G0 cells repair double strand breaks through non-homologous end joining, ATM seems to have function of repair fidelity of NHEJ. We have studied the effect of heavy ion beams on PLDR. It was found that even normal cells showed similar inaccurate fidelity of repair between G0 and G1 repair. It shows that high-LET induced DNA damage can not be accurately repaired even under G0 condition. ATM and NBS1 inhibition of G0 tumor cells may result in more tumor cell death. Further studies using mice are undergoing. Less