Effect of WY-14643 on CYP1B1 expression in MCF-7 cells. (A) Effect of WY-14643 on CYP1B1 protein levels. Cells were treated with WY-14643 (100–200 μM) or TCDD (10 nM) for 24 h and CYP1B1 protein levels were analyzed by immunoblotting of cell lysates using an anti-hCYP1B1 antibody. (B) Cells were cultured with 200 μM WY-14643 for 6, 12, 24, or 48 h and CYP1B1 protein levels were analyzed by immunoblotting of cell lysates using an anti-hCYP1B1 antibody. (C) Effect of WY-14643 on CYP1B1 mRNA levels. Cells were treated with WY-14643 (100–200 μM) or TCDD (10 nM) for 24 h, then lysed; total RNA was prepared for PCR analysis of CYP1B1 mRNA levels, relative to the level of GAPDH. (D) Cells were cultured with 200 μM WY-14643 for 6, 12, 24, or 48 h or TCDD (10 nM) for 48 h, then lysed; total RNA was prepared for PCR analysis of CYP1B1 mRNA levels, relative to the level of GAPDH. (E) Effect of WY-14643 on CYP1B1 promoter activity. Cells transfected with CYP1B1-Luc (−910/+25) were treated with WY-14643 (100–200 μM) or TCDD (10 nM) for 24 h. Cells were harvested and assayed for luciferase activity, which was normalized to the activity of β-galactosidase. Bars are means ± standard deviations of three independent experiments performed in triplicate. * p < 0.01, significantly different from the control.