Fig. (1).

Activity of endogenous steroid receptors in commonly used cell lines. Selected cell lines (COS 7, U2OS, CHO, HEK 293 and K562) were transfected either with pGL4.26-3xERE [luc2/Hygro] or pGL4.26-3xGRE [luc2/Hygro] in the starvation medium and 24 hours after transfection cells were transferred to the white opaque 96-well plate at 2x10⁴ cells/well. Cells transfected with pGL4.26-3xERE [luc2/Hygro] were exposed to different concentrations of 17β-estradiol while cells transfected with pGL4.26-3xGRE [luc2/Hygro] were exposed to different concentrations of cortisol, aldosterone, progesterone, testosterone and mifepristone (RU 486) for another 24 hours. Control cells were exposed only to the diluent (DMSO). Luciferase activity was finally measured using ONE-Glo™ reagent (Promega) and fold induction was calculated as a ratio of the luciferase activity of cells treated with ligands and those treated with DMSO only. For clarity fold inductions are represented in the color scale.