The Effect of Radiation on Ascites Tumour Cells

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Abstract
Mouse ascites tumour cells, which grow freely suspended in the abdominal cavity of the animals, can be considered an anaplastic form in contrast to the more differentiated spindle cells from which they are derived. On explanation into tissue culture and on subcutaneous injection in vivo the free round cells become transformed into spindle cells. T2146 and S37 ascites tumour cells were exposed in vitro to γ radiation before and after establishment of the spindle forms in tissue culture and injected subcutaneously into C3H mice immediately after radiation. The radiation effect on the tissue cultures, as measured by the number of tumours obtained from irradiated grafts of cultures, was the same in both tumour strains and independent of whether the cells were exposed as round or spindle forms. Exposure to γ radiation in vitro of S37 ascites tumour cells and S37 spindle cells derived from subcutaneous tumours showed the former to be much more radiosensitive. The MLD was 500 r units for the ascites form and 2600 r units for the subcutaneous sarcoma. It is tentatively suggested that the great radiosensitivity of the ascites tumour cells may be related (1) to the fact that many of these cells do not reconstruct fully after mitosis and be due to an action of radiation similar to that seen on premitotic cells in other tissues, and (2) to their low metabolic activity.