Kim S H, Um J H, Dong-Won B, Kwon B H, Kim D W, Chung B S, Kang C D
Department of Biochemistry, College of Medicine, Pusan National University, South Korea.
Leuk Res. 2000 Nov;24(11):917-25. doi: 10.1016/s0145-2126(00)00061-8.
DNA-dependent protein kinase (DNA-PK) is activated by DNA strand breaks and participates in DNA repair. Its regulatory subunit, Ku autoantigen, binds to DNA and recruits the catalytic subunit (DNA-PKcs). We show here a new role of DNA-PK in the development of multidrug resistance (MDR). The Ku-DNA binding activity, the levels of Ku70/Ku80 and DNA-PKcs in MDR variants, CEM/VLB(10-2), CEM/VLB(55-8) and CEM/VLB100 were higher than those in their parental drug-sensitive CEM cells in a drug resistance-dependent fashion. Also, CEM/VLB100 cells showed about 3-fold increase of DNA-PK enzyme activity as compared with CEM cells. Similar results were observed in another MDR cell line, FM3A/M mouse mammary carcinoma cells. Moreover, we observed that CEM/VLB100 cells were about 11-fold sensitive to wortmannin, which inhibits DNA-PK, compared with the CEM cells, and sensitized the MDR cells when combined with either bleomycin or vincristine, but have a little effect on CEM cells. Wortmannin was shown to inhibit DNA-PK and Ku-DNA binding activity in CEM/VLB100 cells dose dependently but had a little or no effect on their parental cells. Our results suggested that enhanced expression of DNA-PK participates in the development of MDR, and the use of DNA-PK inhibitors such as wortmannin is likely to improve the effectiveness of anticancer drugs and thus could partially overcome drug resistance in MDR cells, through its ability to inhibit Ku/DNA-PK activity.
DNA依赖性蛋白激酶（DNA-PK）可被DNA链断裂激活，并参与DNA修复。其调节亚基Ku自身抗原可与DNA结合，并募集催化亚基（DNA-PKcs）。我们在此展示了DNA-PK在多药耐药（MDR）发展中的新作用。MDR变体CEM/VLB(10-2)、CEM/VLB(55-8)和CEM/VLB100中Ku与DNA的结合活性、Ku70/Ku80及DNA-PKcs的水平以耐药依赖性方式高于其亲本药物敏感的CEM细胞。此外，与CEM细胞相比，CEM/VLB100细胞的DNA-PK酶活性增加了约3倍。在另一种MDR细胞系FM3A/M小鼠乳腺癌细胞中也观察到了类似结果。此外，我们观察到，与CEM细胞相比，CEM/VLB100细胞对抑制DNA-PK的渥曼青霉素的敏感性约高11倍，且渥曼青霉素与博来霉素或长春新碱联合使用时可使MDR细胞致敏，但对CEM细胞影响较小。渥曼青霉素在CEM/VLB100细胞中呈剂量依赖性抑制DNA-PK及Ku与DNA的结合活性，但对其亲本细胞影响较小或无影响。我们的结果表明，DNA-PK的表达增强参与了MDR的发展，使用诸如渥曼青霉素之类的DNA-PK抑制剂可能会提高抗癌药物的疗效，从而通过其抑制Ku/DNA-PK活性的能力部分克服MDR细胞中的耐药性。
