Development of the methods to detect enzyme activities of proteins involved in repair of DNA double strand breaks

已知细胞中基因组不稳定性的存在在各种器官的多阶段癌变中起重要作用。DNA双链断裂（DSB）修复途径已经涉及通过抑制染色体重排来维持基因组完整性。DNA依赖性蛋白激酶（DNA-PK）在DNA双链断裂修复中具有重要作用。这项研究的目的是确定未经治疗的癌症患者和无癌症的正常健康志愿者之间的DNA-PK活性如何变化，以及这如何影响癌症风险。正常人外周血淋巴细胞DNA-PK活性为15.84± 4.87pmol，恶性肿瘤患者为12.28± 5.10pmol。两组间有显著性差异（p=0.012）。年龄和吸烟与DNA-PK活性无关。DNA-PK活性与DNA-PKcs、ku 70和ku 86的表达之间无相关性。结果表明，外周血淋巴细胞DNA-PK活性与染色体畸变之间存在一定的相关性。在DNA-PK活性高于16.32pmol的个体中未观察到双着丝粒染色体。随着DNA-PK活性的降低，过量片段的频率增加。我们得出结论，DNA-PK活性与染色体不稳定性有关。PBL中DNA-PK活性与各种癌症的风险相关。因此，PBL中的DNA-PK活性可用作肿瘤标志物，以辅助癌症的诊断和癌症易感性的预测。

The presence of genomic instability in cells is known to play an important role in the multistage carcinogenesis of various organs. The DNA double strand breaks(DSBs) repair pathway has been implicated in maintaining genomic integrity via suppression of chromosomal rearrangements. DNA-dependent protein kinase (DNA-PK) has an important role in DNA DSBs repair. The purpose of this study was to determine how DNA-PK activity varies among untreated cancer patients and cancer-free normal healthy volunteers and how this affects cancer risk. DNA-PK activities of peripheral blood lymphocytes(PBL) in normal volunteers were 15.84±4.87 pmol and those of cancer patients were 12.28±5.10 pmol. There was the significant difference between them (p=0.012). Age and smoking had no association with DNA-PK activity. No association was found between DNA-PK activity and expression of DNA-PKcs, ku70, and ku86. A relationship between DNA-PK acitvity and chromosome aberration in PBL was shown to exist. Dicentric chromosomes were not observed in individuals whose DNA-PK activity was higher than 16.32 pmol. The frequency of excess fragment increased as the DNA-PK activity decreased. We conclude that DNA-PK activity is associated with chromosomal instability. DNA-PK activity in PBL is associated with risk of various kinds of cancer. Therefore, DNA-PK activity in PBL would be useful as a tumor marker to assist in the diagnosis of cancer and in the prediction of cancer susceptibility.