Induction of retrovirus gene expression by aflatoxin B1 and 2-acetylaminofluorene

The abilities of 2-acetylaminofluorene (AAF) and aflatoxin B1 (AFB) to induce the expression of endogenous murine retrovirus in AKR mouse embryo fibroblasts were examined. AFB was able to induce virus expression at concentrations as low as 0.067 microM, although the induction efficiency was increased at higher doses. AAF gave somewhat more variable results. In some experiments induction was observed with as little as 0.1 microM while in other experiments induction was not observed at concentrations as high as 100 microM. Addition of an S9 metabolizing system enhanced the ability of AAF to induce virus expression but also increased the background induction frequency. These results are discussed in relation to the mechanism of virus induction and the potential usefulness of virus induction as an assay for carcinogenic potential.