Low dose hyper-radiosensitivity and increased radioresistance in mammalian cells.

This manuscript reviews the low-dose survival work using the DMIPS cell analyser that has been carried out at the Gray Laboratory in the U.K. and the British Columbia Cancer Research Centre in Canada. It describes low dose hyper-radiosensitivity (HRS) detected after single doses of X-rays less than approximately 0.3 Gy and the subsequent increased radioresistant response (IRR) seen as the dose increases up to 1 Gy. Work is summarized from studies in V79 cells, normal human and human tumour cell lines and mutant cell lines deficient in DNA repair. The data are considered in light of the hypothesis that hyper-radiosensitivity and increased radioresistance reflect the existence of an inducible protective mechanism, possibly triggered by DNA damage.