The two-stage transformation assay increases the sensitivity of cells
to chemicals and permits detection of carcinogens acting as initiating
agents. 1,2-Dibromoethane, a representative halogenated aliphatic, ha
s been tested in the two-stage BALB/c 3T3 cells transformation test at
dosages from 16 mu M to 128 mu M. This dose range is much lower than
those previously found efficient in transforming BALB/c 3T3 cells. Apa
rt from the lowest dose, which induced borderline effects, all the oth
er assayed dosages appeared to induce heritable changes in the traget
cells. The initiated cells were revealed as fully transformed foci bot
h in the combination with a chronic promoting treatment and also by al
lowing cells to perform more rounds of cell replication. The results c
learly show that 1,2-dibromoethane can act as an initiator of cell tra
nsformation.