Kasten-Pisula U, Tastan H, Dikomey E
Laboratory of Radiobiology & Experimental Radiooncology, Clinic of Radiotherapy and Radiooncology, University of Medical Center Hamburg-Eppendorf, Hamburg, Germany.
Int J Radiat Biol. 2005 Jun;81(6):409-19. doi: 10.1080/09553000500140498.
The DNA double-strand break (DSB) repair capacity of normal human fibroblasts was compared with that of cell lines with different genetic alterations. These cell lines are affected either in non-homologous end-joining (180BR), homology directed repair (C2352, C2395), base excision repair (CS1TAN, 46BR) or signalling (AT3, AT2BE, LFS2675, LFS2800, 95P558). Cellular radiosensitivity was determined by colony formation assay, DSB by constant-field gel electrophoresis and apoptosis was detected by caspase3 activity. For the mutated cell lines, the survival fraction at 2 Gy (SF2) varied between 0.013 and 0.49 in contrast to a variation of only 0.15-0.53 for normal fibroblasts. There was no variation in the number of initial DSB and only a small variation in the number of DSB remaining 24 h after irradiation. At 100 Gy, the latter number varied between 2 and 5 Gy-equivalents for normal fibroblasts and only between 3 and 7 Gy-equivalents for the mutated cell lines, corresponding to repair capacities of 95-98 and 93-97%, respectively. There were, however, two outliers (LFS2800, 180BR) where the number of remaining DSB was much higher with 22 and 30 Gy-equivalents, respectively. This elevated number resulted from a delayed repair and apoptotic cells. For all but these two cell lines, the relationship between the number of DSB remaining 24 h after irradiation and SF2 could be described by an identical correlation (r2 = 0.86, p < 0.0001). This result indicates that the relationship between DSB repair capacity and cellular radiosensitivity appears to be the same for normal and mutated cell lines, and that in both cases huge differences in cellular radiosensitivity result from only a very small variation in DSB repair capacity.
将正常人成纤维细胞的DNA双链断裂（DSB）修复能力与具有不同基因改变的细胞系进行了比较。这些细胞系在非同源末端连接（180BR）、同源定向修复（C2352、C2395）、碱基切除修复（CS1TAN、46BR）或信号传导（AT3、AT2BE、LFS2675、LFS2800、95P558）方面受到影响。通过集落形成试验测定细胞放射敏感性，通过恒定电场凝胶电泳测定DSB，通过caspase3活性检测细胞凋亡。对于突变细胞系，2 Gy时的存活分数（SF2）在0.013至0.49之间变化，而正常成纤维细胞仅在0.15至0.53之间变化。初始DSB的数量没有变化，照射后24小时剩余DSB的数量仅有很小的变化。在100 Gy时，后者的数量对于正常成纤维细胞在2至5 Gy当量之间变化，对于突变细胞系仅在3至7 Gy当量之间变化，分别对应95 - 98%和93 - 97%的修复能力。然而，有两个异常值（LFS2800、180BR），其中剩余DSB的数量分别高达22和30 Gy当量，显著更高。这个升高的数量是由修复延迟和凋亡细胞导致的。对于除这两个细胞系之外的所有细胞系，照射后24小时剩余DSB的数量与SF2之间的关系可以用相同的相关性来描述（r2 = 0.86，p < 0.0001）。这一结果表明，DSB修复能力与细胞放射敏感性之间的关系在正常和突变细胞系中似乎是相同的，并且在这两种情况下，细胞放射敏感性的巨大差异仅源于DSB修复能力的非常小的变化。
