title: Alterations in heat-induced radiosensitization accompanied by nuclear structure alterations in Chinese hamster cells.
abstract: This paper examined heat-induced radiosensitization in two Chinese hamster heat-resistant cell lines, HR-1 and OC-14, that were isolated from the same wild-type HA-1 cell line. It found a reduction of the magnitude of heat-induced radiosensitization after exposure to 43 degrees C in both HR-1 and OC-14 cells and a similar reduction after exposure to 45 degrees C in HR-1 cells, but not in OC-14 cells. The effect of heat exposure on a class of ionizing radiation-induced DNA damage that inhibits the ability of nuclear DNA to undergo super-coiling changes was also studied using the fluorescent halo assay in these three cell lines. Wild type cells exposed to either 43 or 45 degrees C before irradiation had a DNA rewinding ability that was intermediate between control and unheated cells, a phenomenon previously described as a masking effect. This masking effect was significantly reduced in HR-1 cells exposed to either 43 or 45 degrees C or in OC-14 cells exposed to 43 degrees C under conditions that heat-induced radiosensitization was reduced. In contrast, the masking effect was not altered in OC-14 cells exposed to 45 degrees C, conditions under which heat-induced radiosensitization was similar to that observed in wild-type HA-1 cells. These results suggest that a reduction in the masking effect is associated with a reduction of the magnitude of heat-induced radiosensitization in the HR-1 and OC-14 heat-resistant cell lines. The reduction of the masking effect in the cell lines resistant to heat-induced radiosensitization was associated with neither a reduction in the magnitude of the heat-induced increase in total nuclear protein content nor major differences in the protein profiles of the nucleoids isolated from heated cells.
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO 63108, USA. laszlo@wustl.edu
authors.forename: Andrei
authors.initials: A
authors.lastname: Laszlo
authors.forename: Teri
authors.initials: T
authors.lastname: Davidson
authors.forename: Amanda
authors.initials: A
authors.lastname: Harvey
authors.forename: Julia E
authors.initials: JE
authors.lastname: Sim
authors.forename: Robert S
authors.initials: RS
authors.lastname: Malyapa
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Spitz
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Roti Roti
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004249:DNA Damage; D006979:Hyperthermia, Induced; D009687:Nuclear Proteins / Q000096:biosynthesis; D011836:Radiation Tolerance
chemical_list: D009687:Nuclear Proteins