Title: Recovery of low-dose hyper-radiosensitivity following a small priming dose depends on priming dose-rate

Authors: Nina Jeppesen Edin, Dag Rune Olsen, Trond Stokke, Erik Olai Pettersen

Addresses: Department of Physics, Group of Biophysics and Medical Physics, University of Oslo, P.B. 1048, Blindern, 0316 Oslo, and Department of Radiation Biology and Centre for Research and Training in Radiation Therapy, The Norwegian Radium Hospital, 0310 Oslo, Norway. ' Department of Physics, Group of Biophysics and Medical Physics, University of Oslo, P.B. 1048, Blindern, 0316 Oslo, and Department of Radiation Biology and Centre for Research and Training in Radiation Therapy, The Norwegian Radium Hospital, 0310 Oslo, Norway. ' Department of Radiation Biology and Centre for Research and Training in Radiation Therapy, The Norwegian Radium Hospital, 0310 Oslo, Norway. ' Department of Physics, Group of Biophysics and Medical Physics, University of Oslo, P.B. 1048, Blindern, 0316 Oslo, Norway

Abstract: T-47D human breast cancer cells were irradiated with ⁶⁰Co γ-radiation and radiation response was measured by loss of ability of single-cells to form colonies. The influence of the dose-rate on the ability of priming irradiation to abolish Low-Dose Hyper-Radiosensitivity (LDHRS) was investigated. In agreement with previous reports, the LDHRS was abolished by an acute priming dose of 0.3 Gy given 6 h prior to the challenge dose. When the interval between the priming- and challenge-doses was increased to 24 h, LDHRS was restored. However, when the priming dose was delivered at a low dose-rate (0.3 Gy/h), the abolition of LDHRS that again appeared 6 h following the priming dose, now persisted for intervals of up to 14 weeks between doses even after 28 passages during the 14 weeks.

Keywords: ⁶⁰Co γ-radiation; human breast cancer; cancer cells; low dose hyper-radiosensitivity; LDHRS; dose rate; priming irradiation; low radiation.

DOI: 10.1504/IJLR.2007.014491

International Journal of Low Radiation, 2007 Vol.4 No.1, pp.69 - 86

Published online: 11 Jul 2007 *

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