[Promoting action of tetradecanoylphorbol acetate on the phenotypic expression of the mutation for the acquisition of resistance to diphtheria toxin in cultured human cells].

Stable spontaneous mutants resistant to the protein synthesis inhibitor diphtheria toxin (DT) have been selected in human cell line eue at a very low frequency (8 x 10(-6)). We have studied in this system the effect of the promoting agent phorbol-12-myristate-13-acetate (TPA) on mutagenesis induced by benzo(a)pyrene (BP). TPA did not increase the mutation frequencies induced by BP, but it showed a trend to make shorter the expression time.