title: Proton-HZE-particle sequential dual-beam exposures increase anchorage-independent growth frequencies in primary human fibroblasts.
abstract: The radiation field in deep space contains high levels of high-energy protons and substantially lower levels of high-atomic-number, high-energy (HZE) particles. Calculations indicate that cellular nuclei of human space travelers will be hit during a 3-year Mars mission by approximately 400 protons and approximately 0.4 HZE particles. Thus most cells in astronauts will be hit by a proton(s) before being hit by an HZE particle. To investigate effects of dual ion irradiations on human cells, we irradiated primary human neonatal fibroblasts with protons (1 GeV/nucleon, 20 cGy) followed from 2.5 min to 48 h later by iron or titanium ions (1 GeV/nucleon, 20 cGy) and then measured clonogenic survival and frequency of anchorage-independent growth. This frequency depends on the interval between hydrogen- and iron-ion irradiation, with a critical window between 2.5 min and 1 h producing about three times more anchorage-independent colonies per survivor than expected from simple addition of the two ions separately. The hydrogen-titanium-ion dual-beam irradiation produced similar increases that persisted to approximately 6 h. At longer intervals, anchorage-independent growth frequencies were similar to those expected for additivity. However, irradiation of cells with either an iron or a titanium particle first followed by protons produced only additive levels.
authors.affiliation: Biology Department, Brookhaven National Laboratory, Upton, NY 11973-5000, USA.
authors.forename: Guangming
authors.initials: G
authors.lastname: Zhou
authors.forename: Paula V
authors.initials: PV
authors.lastname: Bennett
authors.forename: Noelle C
authors.initials: NC
authors.lastname: Cutter
authors.forename: Betsy M
authors.initials: BM
authors.lastname: Sutherland
mesh_terms: D002448:Cell Adhesion / Q000528:radiation effects; D049109:Cell Proliferation / Q000528:radiation effects; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D003359:Cosmic Radiation; D004307:Dose-Response Relationship, Radiation; D004781:Environmental Exposure; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D020450:Heavy Ions; D006801:Humans; D011522:Protons; D011829:Radiation Dosage
chemical_list: D011522:Protons