QUANTITATIVE STUDIES OF RADIATION TRANSFORMATION WITH THE A31-11 MOUSE BALB-3T3 CELL-LINE

Abstract

A cloned mouse embryo-derived fibroblast cell line was used to study morphological transformation induced by X-rays and 254 nm UV. The transformation frequency increased exponentially with increasing dose from 10-400 rads for X-rays and 1.0-7.5 J/sq m for UV exposure. Split-dose X ray exposures led to an enhancement in transformation at total doses below 100 rads and a reduction at doses of 300-400 rads. The induced transformation frequency varied among serum lots and was very dependent upon the initial cell density. Spontaneous transformants were observed in 10 of 22 consecutive experiments; the spontaneous transformation frequency was generally about 1 to 2 .times. 10-5 as compared to induced frequencies which ranged up to 3 .times. 10-3 for X-rays and 7.5 .times. 10-4 for UV exposure. This cell line apparently has several potential advantages over the mouse 10T1/2 line for studies with relatively weak in vitro carcinogens such as radiation. These include a reduced overall expression time for the appearance of transformed foci (4 wk); a high cloning efficiency (50-60%); and the fact that about 20 times as many viable cells may be plated per dish for optimal results, allowing transformation frequencies as low as 10-5 to be measured easily. There was more variability in the results among experiments with the 3T3 cell line.