A beef-derived mutagenesis modulator inhibits initiation of mouse epidermal tumors by 7,12-dimethylbenz[a]anthracene.

Ground beef contains an organic solvent extractable mutagenesis modulator. Crude or partially-purified preparations of the activity were applied to the backs of SENCAR or CD-1 mice 5 min before application of 7,12-dimethylbenz[a]anthracene (DMBA). Controls received solvent (acetone) only prior to DMBA. Following 1-2 week intervals promotion was effected with twice-weekly applications of 12-O-tetradecanoylphorbol-13-acetate. Modulator-treated mice consistently developed fewer papillomas and exhibited lower tumor incidences than did positive control mice.