27-hydroxycholesterol and the expression of three estrogen-sensitive proteins in MCF7 cells

The principal aim of this study was to analyze in estrogen receptor-positive MCF7 cells the response of three estrogen-dependent proteins to 27-hydroxycholesterol (27OHC), a major circulating cholesterol metabolite. Immunofluorescence, immunoblotting and immunogold labelling analyses of MCF7 cells exposed for up to 72 h to 2 nM estradiol (E-2) or to 2 mu M 27OHC demonstrated similar responses in the expression of MnSOD and ER beta compared to the non-stimulated cells. Thus, the results confirm 27OHC's function as a novel selective estrogen receptor modulator (SERM). The epithelial to mesenchymal transition (EMT), observed in MCF7 cells stimulated for longer than 48 h with 2 mu M 27OHC, was accompanied by lower immunoreactive levels of nuclear FOXM1 in comparison to E-2-treated cells. The results presented in this study are discussed taking into consideration the relationship of hypercholesterolemia, 27OHC production, ROS synthesis and macrophage infiltration, potentially occurring in obese patients with ER alpha-positive, infiltrated mammary tumors.