Fig. 2.

Effects of LTEE on PhIP:DNA adduct formation and CYP1 inducibility in MCF-7 cells. MCF-7 cells were cultured for 35 or more passages in DC₅ (Control) or DC₅ containing 1 nM E₂ (LTEE). Cells were then seeded in DC₅ medium and were exposed for 24 h to the DMSO vehicle or 10 µM PhIP with or without 10 nM TCDD, as indicated. (A) DNA was isolated and hydrolyzed, and PhIP adducts were analyzed by LC-ESI/MS³. Data shown are the means ± SE; n = 3. Significant differences between control and LTEE cells exposed to TCDD and PhIP (***, P < 0.001) and between LTEE cells treated with and without TCDD (###, P < 0.001) are indicated. (B) EROD activities were determined, and the data shown are the means ± SE; n = 5. Significant differences between control and LTEE cells with identical treatments are indicated (***, P < 0.001). (C) Dose-response curves for inhibition of TCDD-induced EROD activity of control and LTEE cells by PhIP, with the addition of PhIP coincident with TCDD exposure (upper) or during the EROD assay (lower). Data shown are the means ± SE; n = 5. Significant differences are indicated between LTEE cells treated with TCDD alone and TCDD plus the indicated concentration of PhIP (***, P < 0.001).