Suppression of gamma- and neutron-induced neoplastic transformation by ascorbic acid in Balb/c 3T3 cells

The effects of ascorbic acid on the neoplastic transformation induced by 60Co gamma-rays or 252Cf fission neutrons were studied. The transformation induced by each of the radiations was markedly suppressed when ascorbic acid was added daily to the culture medium during the first 8 days of the post-irradiation period. If ascorbic acid was added for a total of 8 days as mentioned above, but with 1 day interruption in the middle, the suppression of transformation was decreased. Ascorbic acid also suppressed the promotion of radiation transformation by 12-O-tetradecanoylphorbol-13-acetate (TPA) when both chemicals were added to the medium together. However, promotion of radiation transformation by TPA was observed if both the chemicals were added sequentially during the post-irradiation period, i.e. ascorbic acid for the first 7 days followed by TPA. These results suggest that continuous administration of ascorbic acid for a certain number of days is needed to suppress the radiation transformation, and also suggest that it acts on the promotion stage of transformation.