Research Papers: Breast CancerDietary extra-virgin olive oil and corn oil differentially modulate the mRNA expression of xenobiotic-metabolizing enzymes in the liver and in the mammary gland in a rat chemically induced breast cancer modelManzanares, Miguel Á.a,*; Solanas, Montserrata,*; Moral, Raquela; Escrich, Raquela; Vela, Elenaa; Costa, Irmgarda,b; Escrich, EduardaAuthor Information aDepartment of Cell Biology, Physiology and Immunology, Medical Physiology Unit, School of Medicine, Universitat Autònoma de Barcelona, Barcelona bDepartment of Pathology, Corporació Sanitària Parc Taulí, Sabadell, Spain * Miguel Á. Manzanares and Montserrat Solanas contributed equally to this work. Correspondence to Eduard Escrich, PhD, Department of Cell Biology, Physiology and Immunology, Medical Physiology Unit, School of Medicine, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain Tel: +34 935 811 423; fax: +34 935 812 986; e-mail: email@example.com Received February 6, 2014 Accepted March 12, 2014 European Journal of Cancer Prevention: May 2015 - Volume 24 - Issue 3 - p 215-222 doi: 10.1097/CEJ.0000000000000032 Buy Metrics Abstract High extra-virgin olive oil (EVOO) and corn oil diets differentially modulate experimental mammary carcinogenesis. We have investigated their influence on the initiation stage through the modulation of the expression of xenobiotic-metabolizing enzymes (XMEs) in the liver and the mammary gland. Female Sprague–Dawley rats were fed a low-fat (LF), high corn oil (HCO), or high EVOO (HOO) diet from weaning and gavaged with 7,12-dimethylbenz(a)anthracene (DMBA). The HCO diet increased the mRNA levels of the phase I enzymes CYP1A1, CYP1A2 and, to a lesser extent, CYP1B1, in the liver. The Aryl hydrocarbon receptor (AhR) seemed to be involved in this upregulated CYP1 expression. However, a slight trend toward an increase in the mRNA levels of the phase II enzymes GSTP1 and NQO1 was observed with the HOO diet. At least in the case of GSTP1, this effect was linked to an increased Nrf2 transactivation activity. This different regulation of the XMEs expression led, in the case of the HCO diet, to a balance between the production of active carcinogenic compounds and their inactivation tilted toward phase I, which would stimulate DMBA-induced cancer initiation, whereas the HOO diet was associated with a slower phase I metabolism accompanied by a faster phase II detoxification, thus reducing the output of the active compounds to the target tissues. In the mammary gland, the differential effects of diets may be conditioned by the state of cell differentiation, sexual maturity, and hormone metabolism. Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.