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FIG. 3. Transactivational potencies and efficacies of DES, E2, and phytoestrogens in Ishikawa cells stably expressing human ER (Ishikawa-hER ) or ERß (Ishikawa-hERß). Transcriptional activity was measured on reporter vectors containing three copies of (A and B) the consensus ERE (3x ERE) or (C and D) the human C3 promoter. Relative potency was calculated by 100 x EC50 (DES)/EC50 (test compound) and is indicated next to each column. DES was set to 100. EC50 values (ligand concentration yielding half-maximal activation) were derived by nonlinear curve-fitting from transactivation curves obtained in Ishikawa-hER or Ishikawa-hERß cells (e.g., Fig. 2) and are given as mean ± standard deviation of at least three independent experiments. Please note (A and C) the logarithmic scale of EC50 values. Relative efficacy was calculated by 100 x efficacy (DES)/efficacy (test compound). DES was set to 100. (B and D) Efficacies (maximum fold induction over control) were determined from transactivation curves obtained in Ishikawa-hER or Ishikawa-hERß cells (e.g., Fig. 2) and are given as mean ± standard deviation of at least three independent experiments. *EC50 value could not be determined; therefore, the highest dose tested is given in parentheses.
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