title: 4-Hydroxyestradiol induces mammary epithelial cell transformation through Nrf2-mediated heme oxygenase-1 overexpression.
abstract: Estrogen (17β-estradiol, E2) undergoes oxidative metabolism by CYP1B1 to form 4-hydroxyestradiol (4-OHE2), a putative carcinogenic metabolite of estrogen. Our previous study showed that 4-OHE2-induced production of reactive oxygen species contributed to neoplastic transformation of human breast epithelial (MCF-10A) cells. In this study, 4-OHE2, but not E2, increased the expression of heme oxygenase-1 (HO-1), a sensor and regulator of oxidative stress, in MCF-10A cells. Silencing the HO-1 gene in MCF-10A cells suppressed 4-OHE2-induced cell proliferation and transformation. In addition, subcutaneous administration of 4-OHE2 markedly enhanced the growth of the MDA-MB-231 human breast cancer xenografts, which was retarded by zinc protoporphyrin, a pharmacological inhibitor of HO-1. 4-OHE2-induced HO-1 expression was mediated by NF-E2-related factor 2 (Nrf2). We speculate that an electrophilic quinone formed as a consequence of oxidation of 4-OHE2 binds directly to Kelch-like ECH-associated protein 1 (Keap1), an inhibitory protein that sequesters Nrf2 in the cytoplasm. This will diminish association between Nrf2 and Keap1. 4-OHE2 failed to interrupt the interaction between Keap1 and Nrf2 and to induce HO-1 expression in Keap1-C273S or C288S mutant cells. Lano-LC-ESI-MS/MS analysis in MCF-10A-Keap1-WT cells which were treated with 4-OHE2 revealed that the peptide fragment containing Cys288 gained a molecular mass of 287.15 Da, equivalent to the addition of a single molecule of 4-OHE2-derived ortho-quinones.
authors.affiliation: Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 08826, South Korea.
authors.forename: Sin-Aye
authors.initials: SA
authors.lastname: Park
authors.affiliation: Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 08826, South Korea.
authors.forename: Mee-Hyun
authors.initials: MH
authors.lastname: Lee
authors.affiliation: Department of Food and Nutrition, College of Human Ecology, Sungshin Women's University, Seoul 136-742, South Korea.
authors.forename: Hye-Kyung
authors.initials: HK
authors.lastname: Na
authors.affiliation: Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 08826, South Korea.|Department of Molecular Medicine and Biopharmaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, South Korea.|Cancer Research Institute, Seoul National University, Seoul 110-799, South Korea.
authors.forename: Young-Joon
authors.initials: YJ
authors.lastname: Surh
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000209:etiology* / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000235:genetics* / Q000378:metabolism*; D004195:Disease Models, Animal; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D002393:Estrogens, Catechol / Q000009:adverse effects*; D005260:Female; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D051547:Heme Oxygenase-1 / Q000235:genetics* / Q000378:metabolism; D064593:Heterografts; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D020218:Response Elements; D047368:Tumor Burden
chemical_list: D002393:Estrogens, Catechol; D051267:NF-E2-Related Factor 2; C014036:4-hydroxyestradiol; D051547:Heme Oxygenase-1
keywords: 4-hydroxyestradiol; Nrf2; breast cancer; catechol estrogen; heme oxygenase-1