Figure 2.

Antiestrogens, but not estrogen, induce NAD(P)H:quinone oxidoreductase enzyme activity in MCF-7 breast cancer cells: Concentration-dependence and time course. (A) Effect of different compounds on QR activity in MCF-7 cells. Cells were treated with different concentrations of E₂, TOT, tamoxifen (TAM), ICI, TBHQ, or TPA. Cells were harvested after 4 days of treatment. (B) Time course of induction of QR activity in MCF-7 breast cancer cells. MCF-7 cells were treated with the indicated concentrations of E₂, TOT, ICI, or TBHQ. Cells were then harvested at the indicated time points. Cytosolic extracts were assayed for QR activity as described. Values are the means ± SE from three separate experiments.