title: Potentiation of chemosensitivity in multidrug-resistant human leukemia CEM cells by inhibition of DNA-dependent protein kinase using wortmannin.
abstract: 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.
authors.affiliation: Department of Biochemistry, College of Medicine, Pusan National University, South Korea. ksh7738@hyowon.pusan.ac.kr
authors.forename: S H
authors.initials: SH
authors.lastname: Kim
authors.forename: J H
authors.initials: JH
authors.lastname: Um
authors.forename: B
authors.initials: B
authors.lastname: Dong-Won
authors.forename: B H
authors.initials: BH
authors.lastname: Kwon
authors.forename: D W
authors.initials: DW
authors.lastname: Kim
authors.forename: B S
authors.initials: BS
authors.lastname: Chung
authors.forename: C D
authors.initials: CD
authors.lastname: Kang
mesh_terms: D000730:Androstadienes / Q000494:pharmacology*; D000818:Animals; D034961:Antigens, Nuclear; D000970:Antineoplastic Agents / Q000633:toxicity*; D001761:Bleomycin / Q000633:toxicity; D002460:Cell Line; D004265:DNA Helicases; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000235:genetics; D018432:Drug Resistance, Multiple; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D006801:Humans; D000072200:Ku Autoantigen; D007938:Leukemia; D008325:Mammary Neoplasms, Experimental; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D014407:Tumor Cells, Cultured; D014750:Vincristine / Q000633:toxicity; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D034961:Antigens, Nuclear; D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D009687:Nuclear Proteins; D001761:Bleomycin; D014750:Vincristine; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; C000606511:Xrcc6 protein, rat; D000072200:Ku Autoantigen; D000077191:Wortmannin