Radiotherapeutic Effects on Mammalian Tumour Cells: 1. Modification of Leukaemia L1210 Growth Kinetics with X-irradiation

SummaryThe effect of x-irradiation on the growth kinetics of mammalian tumour cells has been examined using the murine leukaemia L1210 system. After single doses of radiation, the surviving cells were found to have decreased virulence compared with single normal leukaemic cells as measured by the survival-time of recipient mice. Studies on cloned sub-lines demonstrated their capacity for continuous division resulting in death of inoculated animals, although the rate of proliferation determined from growth curves was significantly slower. These in vivo experiments confirm the in vitro observations that ionizing radiation produces a type of non-lethal hereditable damage which results in modification of cell-growth rates.