2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) promotes the transformation of C3H/10T1/2 cells.

Continuous treatment of C3H/10T1/2 cells with low concentrations (greater than or equal to 4 pM) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) enhanced focus production in cultures pretreated with N-methyl-N'-nitro-N-nitrosoguanidine. Maximal enhancement occurred at 40 pM TCDD, a concentration 10 000-fold lower than that required to produce an optimal response with 12-O-tetradecanoylphorbol-13-acetate. Single treatments with 0.06 nM-5 microM TCDD did not transform C3H/10T1/2 cells or initiate the process of transformation in cultures subsequently exposed to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate. Promotion of transformation is thus the predominant effect of TCDD in the C3H/101/2 cell transformation system.