title: Germanium oxide enhances the radiosensitivity of cells.
abstract: We investigated here the combined effect of GeO(2) and radiation on cell viability. Cells were treated with 0 to 22 mM GeO(2) for 12 h followed by 1 Gy X irradiation. A synergistic cytotoxic effect was observed for the combined treatment with a dose-dependent reduction of cell viability. Complete survival curves showed a 2.3- and 2.75-fold increase in radiosensitivity for 50% cell death in the presence of 5 and 15 mM GeO(2), respectively. The increased radiosensitivity also occurred when GeO(2) was given either 4 h prior to irradiation or immediately after radiation exposure. GeO(2) did not affect the total soluble thiol content or the activities of catalase and glutathione S-transferase. Analysis of the production of reactive oxygen species (ROS) revealed that the combined treatment dramatically increased the synthesis of ROS. Addition of N-acetyl cysteine (NAC, 20 mM) decreased the production of ROS in cells. NAC, however, increased cell viability only slightly after treatment with GeO(2) and radiation. Thus increased production of ROS makes little or no contribution to the observed death. The combination of GeO(2) and X radiation, however, significantly increased the frequency of DNA double-strand breaks (DSBs). Notably, the presence of GeO(2) also reduced the efficiency of DNA repair. We conclude that treatment with GeO(2) followed by X irradiation increases DNA DSBs and cell death.
authors.affiliation: Institute of Radiation Biology and Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Shu-Jun
authors.initials: SJ
authors.lastname: Chiu
authors.forename: Ming-Yao
authors.initials: MY
authors.lastname: Lee
authors.forename: Wen-Gang
authors.initials: WG
authors.lastname: Chou
authors.forename: Lih-Yuan
authors.initials: LY
authors.lastname: Lin
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D016587:Antimutagenic Agents / Q000494:pharmacology; D016466:CHO Cells; D002374:Catalase / Q000378:metabolism; D002470:Cell Survival / Q000528:radiation effects*; D006224:Cricetinae; D004249:DNA Damage / Q000528:radiation effects*; D004260:DNA Repair; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D016166:Free Radical Scavengers / Q000494:pharmacology; D005857:Germanium / Q000494:pharmacology*; D005982:Glutathione Transferase / Q000378:metabolism; D011836:Radiation Tolerance / Q000187:drug effects*; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds / Q000378:metabolism / Q000494:pharmacology; D013997:Time Factors; D014965:X-Rays
chemical_list: D016587:Antimutagenic Agents; D016166:Free Radical Scavengers; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D005857:Germanium; C040516:germanium oxide; D002374:Catalase; D005982:Glutathione Transferase; D000111:Acetylcysteine