title: A dose threshold for a medium transfer bystander effect for a human skin cell line.
abstract: The existence of radiation-induced bystander effects mediated by diffusible factors is now accepted, but the mechanisms and precise behavior at low doses remain unclear. We exposed cells to gamma-ray doses in the range 0.04 mGy-5 Gy, harvested the culture medium, and transferred it to unirradiated reporter cells. Calcium fluxes and clonogenic survival were measured in the recipients. We show evidence for a dose threshold around 2 mGy for the human skin cell line used with a suggestion of increased survival below that dose. Similar experiments using direct gamma irradiation showed no reduction in survival until the dose exceeded 7 mGy. Preliminary data for neutrons where the gamma-ray dose was kept below the bystander threshold do not show a significant bystander effect in the dose range 1-33 mGy. A lack of a bystander response with neutrons occurred at around 1 Gy, where significant cell killing from direct irradiation was observed. The result may have implications for understanding the role of bystander effects at low doses.
authors.affiliation: Medical Physics and Applied Radiation Sciences Department, McMaster University, Hamilton, Ontario, Canada L8S 4K1. liuz7@mcmaster.ca
authors.forename: Zhengfeng
authors.initials: Z
authors.lastname: Liu
authors.forename: Carmel E
authors.initials: CE
authors.lastname: Mothersill
authors.forename: Fiona E
authors.initials: FE
authors.lastname: McNeill
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Lyng
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Byun
authors.forename: Colin B
authors.initials: CB
authors.lastname: Seymour
authors.forename: William V
authors.initials: WV
authors.lastname: Prestwich
mesh_terms: D024201:Bystander Effect / Q000502:physiology* / Q000528:radiation effects*; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D003470:Culture Media / Q000378:metabolism; D004056:Differential Threshold / Q000502:physiology* / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D011829:Radiation Dosage; D012867:Skin / Q000166:cytology* / Q000528:radiation effects*; D012879:Skin Physiological Phenomena / Q000528:radiation effects*
chemical_list: D003470:Culture Media