Abstract

Effects of 27-hydroxycholesterol on the expression of estrogen receptors (ERs) and MnSOD in mammary tumor cells Pamela Cruz 1, María E. Ramírez 1, María José Epuñán 1, Cristian G. Torres 2, Luis E. Valladares 1, Walter D. Sierralta 1 1 Laboratorio de Nutrición y Regulación Metabólica, INTA-Universidad de Chile. 2 Laboratorio de Medicina Experimental, Escuela de Medicina Veterinaria, Universidad Andrés Bello, Santiago. Introduction: We have previously reported that stimulation with 27-hydroxycholesterol (27OHC, a novel selective estrogen receptor modulator, SMER) induces the proliferation of estrogen receptor (ER) positive MCF7 cells. The mitogenic activation is followed by an epithelial-mesenchymal transition (EMT) of the tumor cells within 72h. Both processes requires increased metabolic activity. Some groups have detected estrogen receptor alpha and ER beta in mitochondria from MCF7 cells, showing that the signaling of estradiol (E2) through the mitochondrial ERs (mERs) comprise the activation of protective mitochondrial enzymes, particularly Manganese superoxide dismutase (MnSOD). This impelled us to analyze the response of mERs and of MnSOD upon E2 or 27OHC stimulation. Hypothesis: The stimulation by 27OHC affects the immunoreactivity of ERs and Mn-superoxide dismutase (Mn-SOD) in MCF7 cells. Methods: The expression of MnSOD and ERs in non-stimulated and E2- or 27OHC-stimulated MCF7 cells was analyzed using and indirect immunofluorescence and westernblotting with appropiated primary antibodies. The mitochondrial activity was qualitatively assessed with Mitotracker. Results: Enhanced immunoreactivity of MnSOD in mitochondria was observed upon stimulation of MCF7 cells with either 27OHC or E2. Under the oxysterol, augmented expression of ER beta but not of ER alpha was seen. Conclusions: In MCF7 cells, 27OHC -a novel SERM- increased the expression of MnSOD and the immunoreactivity of ER beta; probably these responses are part of a mechanism protecting from the ROS produced by the augmented mitochondrial activity associated to proliferation and EMT. Acknowledgement: Funded by Fondecyt # 1090057.