title: Cisplatin sensitizes cancer cells to ionizing radiation via inhibition of nonhomologous end joining.
abstract: The combination of cisplatin and ionizing radiation (IR) treatment represents a common modality for treating a variety of cancers. These two agents provide considerable synergy during treatment, although the mechanism of this synergy remains largely undefined. We have investigated the mechanism of cisplatin sensitization to IR using a combination of in vitro and in vivo experiments. A clear synergistic interaction between cisplatin and IR is observed in cells proficient in nonhomologous end joining (NHEJ) catalyzed repair of DNA double-strand breaks (DSB). In contrast, no interaction between cisplatin and IR is observed in NHEJ-deficient cells. Reconstituted in vitro NHEJ assays revealed that a site-specific cisplatin-DNA lesion near the terminus results in complete abrogation of NHEJ catalyzed repair of the DSB. These data show that the cisplatin-IR synergistic interaction requires the DNA-dependent protein kinase-dependent NHEJ pathway for joining of DNA DSBs, and the presence of a cisplatin lesion on the DNA blocks this pathway. In the absence of a functional NHEJ pathway, although the cells are hypersensitive to IR, there is no synergistic interaction with cisplatin.
authors.affiliation: Department of Biochemistry and Molecular Biology, Wright State University School of Medicine, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA.
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Boeckman
authors.forename: Kelly S
authors.initials: KS
authors.lastname: Trego
authors.forename: John J
authors.initials: JJ
authors.lastname: Turchi
mesh_terms: D000818:Animals; D001483:Base Sequence; D002384:Catalysis; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002945:Cisplatin / Q000494:pharmacology*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects* / Q000528:radiation effects*; D004260:DNA Repair / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000235:genetics* / Q000473:pathology; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D011995:Recombination, Genetic / Q000187:drug effects* / Q000235:genetics
chemical_list: D011838:Radiation-Sensitizing Agents; D004247:DNA; D002945:Cisplatin