Fig. 4.

AHR agonist and antagonist activities of tryptophan metabolites in MDA-MB-468 and MDA-MB-231 breast cancer cells. Cells were treated with (A) tryptamine, (B) indole-3-acetate, or (C) indole, alone or in combination with TCDD for 24 hours. The effects on CYP1A1 mRNA and AHR and CYP1A1 proteins were determined by real-time PCR or Western blot analysis, respectively, as outlined in Materials and Methods. The mRNA data are mean ± S.E. for three replicate determinations, and statistically significant (P < 0.05) induction (*) or inhibition (**) of TCDD-induced responses are indicated.