FIGURE 3.

TPSF inhibits E₂ and OHT-induced gene expression in a tamoxifen-stimulated cell line. A and B, MCF7ERαHA cells maintained in 6× CD-FBS (22, 37) were treated for 24 h with 0.5 μg/ml Dox to induce ERα expression (37) and 100 pm E₂ and 10 μm TPSF (A) or 500 pm OHT and 10 μm TPSF (B) as indicated. PI-9 mRNA levels were measured by qRT-PCR. PI-9 mRNA in control MCF7ERαHA cells not treated with Dox, E₂, or OHT was set equal to 1. The high level of ERα in Dox-treated cells results in ligand-independent transactivation of PI-9 (23). Data are the average, with the range shown, for two experiments for E₂ and three experiments ± S.E. for OHT.