Figure 5.

Reporter analysis of the transcriptional activity of the estrogen receptor. The MCF-7 (a), MCF-7/Rap (b), and MCF-7/T (c) cells were pretreated with or without 2 mM metformin (MF) for 2 days, then the cells were transfected with the ERE plasmid containing the luciferase reporter gene under the estrogen-responsive element (ERE) and β-galactosidase plasmid. After 3 h the cells were treated for 24 h with the combination of tested drugs as indicated at the diagram. The luciferase and β-galactosidase activities were determined as described in Materials and Methods. Data represent the mean value ± SD of three independent experiments. p < 0.05: * versus respective control, # versus control cells w/o metformin.