Considering indicated antiproliferative activity of compounds in ERα-positive MCF-7 breast cancer cells, ERα was analyzed as a possible target for these synthetic steroids. For this purpose the luciferase reporter assay was used to determine ERα activity in MCF-7 cells. The ERα-mediated reporter constructs were provided to express luciferase under the control of the promoter containing estrogen responsive elements (ERE-TK-LUC). Thus, ERα activity was correlated to luciferase activity measured in treated or control cells.