title: X irradiation induces the proapoptotic state independent of the loss of clonogenic ability in Chinese hamster V79 cells.
abstract: The clonogenic ability (reproductive cell death) of Chinese hamster V79 cells was measured after treatment with X radiation and a newly developed anti-cancer drug, 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)cytosine (ECyd, TAS106). Amplification in the loss of clonogenicity was observed compared to that obtained for cells exposed to X rays alone. Addition of benzyloxycarbonyl-val-ala-asp-fluoromethylketone (Z-VAD-FMK), a broad-spectrum caspase inhibitor, attenuated the increased lethality, but the dose-response curve obtained was found to merely revert to that obtained for cells exposed to X rays alone. Flow cytometric analysis showed that the number of cells arrested at the G2/M phase by X irradiation was decreased by co-treatment with TAS106, and instead the number of cells in the sub-G1 phase increased. Western blot analysis proved that TAS106 treatment down-regulated the expression of the G2/M arrest-related proteins cyclin B1, phospho-CDC2 and WEE1. From these results, it was concluded that (1) no apoptosis was included in the dose-response curve obtained from cells exposed to X rays alone, (2) X radiation induced a potentially apoptotic (proapoptotic) state in cells independent of the loss of their clonogenic ability, and (3) TAS106 enhanced the loss of their clonogenic ability by converting the proapoptotic cells to apoptotic cells through the abrogation of arrest at the G2/M phase.
authors.affiliation: Laboratory of Radiation Biology, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, 060-0818, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Iizuka
authors.forename: Osamu
authors.initials: O
authors.lastname: Inanami
authors.forename: Akira
authors.initials: A
authors.lastname: Matsuda
authors.forename: Ikuo
authors.initials: I
authors.lastname: Kashiwakura
authors.forename: Taketoshi
authors.initials: T
authors.lastname: Asanuma
authors.forename: Mikinori
authors.initials: M
authors.lastname: Kuwabara
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects*; D002455:Cell Division / Q000187:drug effects* / Q000528:radiation effects*; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D003562:Cytidine / Q000008:administration & dosage* / Q000031:analogs & derivatives*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005347:Fibroblasts / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects*; D011836:Radiation Tolerance / Q000187:drug effects*; D011838:Radiation-Sensitizing Agents / Q000008:administration & dosage; D014965:X-Rays
chemical_list: C103084:1-(3-C-ethynylribopentofuranosyl)cytosine; D011838:Radiation-Sensitizing Agents; D003562:Cytidine