Veuger Stephany J, Curtin Nicola J, Richardson Caroline J, Smith Graeme C M, Durkacz Barbara W
Northern Institute for Cancer Research, Medical School, University of Newcastle, Newcastle upon Tyne, United Kingdom.
Cancer Res. 2003 Sep 15;63(18):6008-15.
The DNA repair enzymes, DNA-dependent protein kinase (DNA-PK) and poly(ADP-ribose) polymerase-1 (PARP-1), are key determinants of radio- and chemo-resistance. We have developed and evaluated novel specific inhibitors of DNA-PK (NU7026) and PARP-1 (AG14361) for use in anticancer therapy. PARP-1- and DNA-PK-deficient cell lines were 4-fold more sensitive to ionizing radiation (IR) alone, and showed reduced potentially lethal damage recovery (PLDR) in G(0) cells, compared with their proficient counterparts. NU7026 (10 micro M) potentiated IR cytotoxicity [potentiation factor at 90% cell kill (PF(90)) = 1.51 +/- 0.04] in exponentially growing DNA-PK proficient but not deficient cells. Similarly, AG14361 (0.4 micro M) potentiated IR in PARP-1(+/+) (PF(90) = 1.37 +/- 0.03) but not PARP-1(-/-) cells. When NU7026 and AG14361 were used in combination, their potentiating effects were additive (e.g., PF(90) = 2.81 +/- 0.19 in PARP-1(+/+) cells). Both inhibitors alone reduced PLDR approximately 3-fold in the proficient cell lines. Furthermore, the inhibitor combination completely abolished PLDR. IR-induced DNA double strand break (DNA DSB) repair was inhibited by both NU7026 and AG14361, and use of the inhibitor combination prevented 90% of DNA DSB rejoining, even 24-h postirradiation. Thus, there was a correlation between the ability of the inhibitors to prevent IR-induced DNA DSB repair and their ability to potentiate cytotoxicity. Thus, individually, or in combination, the DNA-PK and PARP-1 inhibitors act as potent radiosensitizers and show potential as tools for anticancer therapeutic intervention.
DNA修复酶，即DNA依赖性蛋白激酶（DNA-PK）和聚（ADP-核糖）聚合酶-1（PARP-1），是放射抗性和化学抗性的关键决定因素。我们已研发并评估了用于抗癌治疗的新型DNA-PK特异性抑制剂（NU7026）和PARP-1特异性抑制剂（AG14361）。与功能正常的细胞系相比，PARP-1和DNA-PK缺陷的细胞系对单独的电离辐射（IR）敏感性高4倍，并且在G(0)期细胞中潜在致死性损伤修复（PLDR）降低。NU7026（10微摩尔）增强了指数生长的DNA-PK功能正常而非缺陷细胞的IR细胞毒性[90%细胞杀伤时的增强因子（PF(90)）= 1.51±0.04]。同样，AG14361（0.4微摩尔）增强了PARP-1(+/+)细胞的IR（PF(90) = 1.37±0.03），但对PARP-1(-/-)细胞无效。当联合使用NU7026和AG14361时，它们的增强作用是相加的（例如，PARP-1(+/+)细胞中PF(90) = 2.81±0.19）。两种抑制剂单独使用时，均使功能正常的细胞系中的PLDR降低约3倍。此外，抑制剂联合使用完全消除了PLDR。NU7026和AG14361均抑制IR诱导的DNA双链断裂（DNA DSB）修复，并且即使在照射后24小时，使用抑制剂联合也能阻止90%的DNA DSB重新连接。因此，抑制剂阻止IR诱导的DNA DSB修复的能力与其增强细胞毒性的能力之间存在相关性。因此，DNA-PK和PARP-1抑制剂单独或联合使用时，均作为有效的放射增敏剂，并且显示出作为抗癌治疗干预工具的潜力。
