{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T09:20:10Z","timestamp":1785403210934,"version":"3.56.0"},"reference-count":51,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,6,28]],"date-time":"2026-06-28T00:00:00Z","timestamp":1782604800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100009687","name":"Wroc\u0142aw Medical Universit","doi-asserted-by":"publisher","award":["SUBK.D150.24.008"],"award-info":[{"award-number":["SUBK.D150.24.008"]}],"id":[{"id":"10.13039\/501100009687","id-type":"DOI","asserted-by":"publisher"}]},{"award":["SUBK.D150.24.008"],"award-info":[{"award-number":["SUBK.D150.24.008"]}],"id":[{"id":"https:\/\/ror.org\/01qpw1b93","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pharmaceuticals"],"abstract":"<jats:p>Background: Breast cancer is the most common malignancy among women and a leading cause of cancer-related deaths globally. Its development involves hormonal, genetic, environmental and inflammatory factors. Among environmental contributors, cadmium (Cd2+), a metalloestrogen known to induce redox imbalance, as well as estrogen metabolites, may exert divergent biological effects. Methods: This study investigated the effects of 17\u03b2-estradiol (E2) and its metabolites\u20142-methoxyestradiol (2-MeOE2) and 4-hydroxyestradiol (4-OHE2)\u2014administered alone or in combination with CdCl2, on estrogen receptor\u2013-positive MCF-7 breast cancer cells and their doxorubicin-resistant cells (MCF-7\/DOX). We evaluated cytotoxicity, interaction profiles (synergism\/antagonism), and redox-related enzymes associated with drug resistance, including superoxide dismutase 1 (SOD1) and glutathione S-transferase pi (GST-pi). There are no known examples of these types of interactions, especially those involving estrogen metabolites with opposing biological activities\u2014anticancer 2-MeOE2 and procarcinogenic\u20144-OHE2 in combination with cadmium. Cell viability was assessed after 48 h exposure to individual and combined treatments of CdCl2. Interaction types (synergism\/antagonism) were determined via the combination index method. Antioxidative enzymes were evaluated by quantitative and immunocytochemical analysis of SOD1, GST and GST-pi expression. Results: All tested compounds reduced cell viability in a concentration-dependent manner, with CdCl2 showing the highest cytotoxicity. MCF-7 cell lines were generally more sensitive to CdCl2, E2, and 2-MeOE2, whereas MCF-7\/DOX cell lines exhibited greater sensitivity to 4-OHE2. Combination studies revealed predominantly antagonistic interactions, particularly for CdCl2 + 2-MeOE2, suggesting a protective redox-modulating effect of this metabolite. Resistant cells consistently displayed higher SOD1 activity and GST-pi expression, indicating enhanced adaptive responses to oxidative stress. Conclusions: Our study underscores the importance of concentration-dependent interactions between environmental Cd2+ and pathways regulated by 17\u03b2-estradiol and its metabolites, particularly in the context of cytotoxicity and redox imbalance relevant to breast cancer progression and therapy resistance.<\/jats:p>","DOI":"10.3390\/ph19071001","type":"journal-article","created":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T00:54:42Z","timestamp":1782694482000},"page":"1001","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Differential Effects of 17\u03b2-Estradiol, Its Metabolites, and Cadmium on Cytotoxicity and Redox-Related Pathways in Doxorubicin-Sensitive and -Resistant Breast Cancer Cell Lines"],"prefix":"10.3390","volume":"19","author":[{"given":"Ewa","family":"Sawicka","sequence":"first","affiliation":[{"name":"Department of Toxicology, Faculty of Pharmacy, Wroclaw Medical University, Borowska 211, 50-556 Wroclaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Katarzyna","family":"Zdybel","sequence":"additional","affiliation":[{"name":"Students\u2019 Scientific Society, Department of Toxicology, Faculty of Pharmacy, Wroclaw Medical University, 50-556 Wroclaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Martyna","family":"Wolniak","sequence":"additional","affiliation":[{"name":"Students\u2019 Scientific Society, Department of Toxicology, Faculty of Pharmacy, Wroclaw Medical University, 50-556 Wroclaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Agnieszka","family":"Piwowar","sequence":"additional","affiliation":[{"name":"Department of Toxicology, Faculty of Pharmacy, Wroclaw Medical University, Borowska 211, 50-556 Wroclaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1097\/SP9.0000000000000032","article-title":"Risk of breast cancer in assisted reproduction technology: A systematic review and meta-analysis protocol","volume":"29","author":"Guo","year":"2024","journal-title":"Int. J. Surg. Protoc."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"2534522","DOI":"10.1080\/07853890.2025.2534522","article-title":"Development and performance of female breast cancer incidence risk prediction models: A systematic review and meta-analysis","volume":"57","author":"Liu","year":"2025","journal-title":"Ann. Med."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"94","DOI":"10.1186\/s12940-017-0287-4","article-title":"State of the evidence 2017: An update on the connection between breast cancer and the environment","volume":"16","author":"Gray","year":"2017","journal-title":"Environ. Health"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"113","DOI":"10.1146\/annurev-publhealth-040617-014101","article-title":"Environmental determinants of breast cancer","volume":"39","author":"Hiatt","year":"2018","journal-title":"Annu. Rev. Public Health"},{"key":"ref_5","first-page":"337","article-title":"The impact of metalloestrogens on the physiology of male reproductive health as a current problem of the XXI century","volume":"70","author":"Jurkowska","year":"2019","journal-title":"J. Physiol. Pharmacol."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Genchi, G., Sinicropi, M.S., Lauria, G., Carocci, A., and Catalano, A. (2020). The effects of cadmium toxicity. Int. J. Environ. Res. Public Health, 17.","DOI":"10.3390\/ijerph17113782"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1007\/s10911-013-9273-9","article-title":"Metals and breast cancer","volume":"18","author":"Byrne","year":"2013","journal-title":"J. Mammary Gland Biol. Neoplasia"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/j.canep.2016.04.002","article-title":"Dietary intake and urinary level of cadmium and breast cancer risk: A meta-analysis","volume":"42","author":"Lin","year":"2016","journal-title":"Cancer Epidemiol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"153","DOI":"10.1136\/oemed-2011-100111","article-title":"Cadmium exposure and cancer mortality in the Third National Health and Nutrition Examination Survey cohort","volume":"69","author":"Adams","year":"2012","journal-title":"Occup. Environ. Med."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"465","DOI":"10.31557\/APJCP.2025.26.2.465","article-title":"Plumbagin inhibits cadmium-induced interleukin-6\/STAT3 signaling in the triple-negative breast cancer cell line","volume":"26","author":"Titiwattanakarn","year":"2025","journal-title":"Asian Pac. J. Cancer Prev."},{"key":"ref_11","first-page":"545","article-title":"Activation of estrogen receptor-alpha by the heavy metal cadmium","volume":"14","author":"Stoica","year":"2000","journal-title":"Mol. Endocrinol."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Lubovac-Pilav, \u017d., Borr\u00e0s, D.M., Ponce, E., and Louie, M.C. (2013). Using expression profiling to understand the effects of chronic cadmium exposure on MCF-7 breast cancer cells. PLoS ONE, 8.","DOI":"10.1371\/journal.pone.0084646"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2414","DOI":"10.1002\/ijc.28565","article-title":"Unbalanced estrogen metabolism in ovarian cancer","volume":"134","author":"Zahid","year":"2014","journal-title":"Int. J. Cancer"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"231","DOI":"10.1016\/j.canlet.2014.04.018","article-title":"Estrogen metabolism and breast cancer","volume":"356","author":"Samvat","year":"2015","journal-title":"Cancer Lett."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"427","DOI":"10.2174\/1389557515666150226121052","article-title":"Role of 2-methoxyestradiol, an endogenous estrogen metabolite, in health and disease","volume":"15","author":"Valencia","year":"2015","journal-title":"Mini-Rev. Med. Chem."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"170","DOI":"10.1161\/01.RES.0000082334.17947.11","article-title":"Modulation of antioxidant enzyme expression and function by estrogen","volume":"93","author":"Strehlow","year":"2003","journal-title":"Circ. Res."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"580245","DOI":"10.4061\/2011\/580245","article-title":"Estradiol modulates membrane-linked ATPases, antioxidant enzymes, membrane fluidity, lipid peroxidation, and lipofuscin in aged rat liver","volume":"2011","author":"Kumar","year":"2011","journal-title":"J. Aging Res."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1113","DOI":"10.1210\/me.2007-0381","article-title":"Effects of Cu\/Zn superoxide dismutase on estrogen responsiveness and oxidative stress in human breast cancer cells","volume":"22","author":"Rao","year":"2008","journal-title":"Mol. Endocrinol."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Zar\u0119ba, N., Wi\u0119c\u0142awik, K., Kizek, R., Hosnedlova, B., and K\u0119pi\u0144ska, M. (2022). The impact of fullerenes as doxorubicin nano-transporters on metallothionein and superoxide dismutase status in MCF-10A cells. Pharmaceutics, 14.","DOI":"10.3390\/pharmaceutics14010102"},{"key":"ref_20","first-page":"867","article-title":"GSTP1 and cancer: Expression, methylation, polymorphisms and signaling (Review)","volume":"56","author":"Cui","year":"2020","journal-title":"Int. J. Oncol."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"11","DOI":"10.1385\/MO:22:1:011","article-title":"Oxidative stress in breast cancer","volume":"22","author":"Tas","year":"2005","journal-title":"Med. Oncol."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2086","DOI":"10.1038\/s41418-019-0276-y","article-title":"Glutathione S-transferase P1 protects breast cancer cells from adriamycin-induced cell death through promoting autophagy","volume":"26","author":"Dong","year":"2019","journal-title":"Cell Death Differ."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Branca, J.J.V., Fiorillo, C., Carrino, D., Paternostro, F., Taddei, N., Gulisano, M., Pacini, A., and Becatti, M. (2020). Cadmium-induced oxidative stress: Focus on the central nervous system. Antioxidants, 9.","DOI":"10.3390\/antiox9060492"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/j.toxlet.2022.03.003","article-title":"Cadmium and Breast Cancer\u2014Current State and Research Gaps in the Underlying Mechanisms","volume":"361","author":"Tarhonska","year":"2022","journal-title":"Toxicol. Lett."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"4646","DOI":"10.3390\/cimb46050282","article-title":"Oxidative stress in breast cancer: A biochemical map of reactive oxygen species production","volume":"46","author":"Dyachenko","year":"2024","journal-title":"Curr. Issues Mol. Biol."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1007\/978-3-319-56895-9_6","article-title":"Estrogen Receptors in Cell Membranes: Regulation and Signaling","volume":"227","author":"Saczko","year":"2017","journal-title":"Adv. Anat. Embryol. Cell Biol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1016\/S0048-9697(03)00190-6","article-title":"Evaluation of Estrogenicity of Major Heavy Metals","volume":"312","author":"Choe","year":"2003","journal-title":"Sci. Total Environ."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"115109","DOI":"10.1016\/j.envres.2022.115109","article-title":"Cadmium Exposure and Risk of Breast Cancer: A Meta-Analysis","volume":"219","author":"Hawkins","year":"2023","journal-title":"Environ. Res."},{"key":"ref_29","first-page":"279","article-title":"The Growth Inhibitory Effects of Cadmium and Copper on the MDA-MB468 Human Breast Cancer Cells","volume":"15","author":"Panjehpour","year":"2010","journal-title":"Rep. Med. Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"152611","DOI":"10.1016\/j.tox.2020.152611","article-title":"Cadmium induces apoptosis via generating reactive oxygen species to activate mitochondrial p53 pathway in primary rat osteoblasts","volume":"446","author":"Zheng","year":"2020","journal-title":"Toxicology"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"4835","DOI":"10.1021\/acs.jproteome.4c00102","article-title":"Proteomic Analysis Reveals Major Proteins and Pathways That Mediate the Effect of 17-\u03b2-Estradiol in Cell Division and Apoptosis in Breast Cancer MCF7 Cells","volume":"23","author":"Zhou","year":"2024","journal-title":"J. Proteome Res."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"e20224","DOI":"10.1016\/j.heliyon.2023.e20224","article-title":"Estrogens and the Risk of Breast Cancer: A Narrative Review of Literature","volume":"9","author":"Awadi","year":"2023","journal-title":"Heliyon"},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"63","DOI":"10.1016\/j.bbcan.2006.03.001","article-title":"Catechol estrogen quinones as initiators of breast and other human cancers: Implications for biomarkers of susceptibility and cancer prevention","volume":"1766","author":"Cavalieri","year":"2006","journal-title":"Biochim. Biophys. Acta Rev. Cancer"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.taap.2015.09.006","article-title":"Cadmium promotes the proliferation of triple-negative breast cancer cells through EGFR-mediated cell cycle regulation","volume":"289","author":"Wei","year":"2015","journal-title":"Toxicol. Appl. Pharmacol."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"1081","DOI":"10.1038\/nm902","article-title":"Cadmium mimics the in vivo effects of estrogen in the uterus and mammary gland","volume":"9","author":"Martin","year":"2003","journal-title":"Nat. Med."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"363","DOI":"10.1016\/S1535-6108(03)00077-1","article-title":"2ME2 Inhibits Tumor Growth and Angiogenesis by Disrupting Microtubules and Dysregulating HIF","volume":"3","author":"Mabjeesh","year":"2003","journal-title":"Cancer Cell"},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Sawicka, E., Saczko, J., Kulbacka, J., Szyde\u0142ko, M., Szyma\u0144ska, B., and Piwowar, A. (2022). The Influence of Interaction beetween Cad mium with 17\u03b2-Estradiol, 2-Methoxyestradiol and 16\u03b1-Hydroxyestrone on Viability and p-Glycoprotein in Ovarian Cancer Cell Line. Int. J. Mol. Sci., 23.","DOI":"10.3390\/ijms23052628"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1016\/j.canlet.2011.09.005","article-title":"Involvement of Reactive Oxygen Species in 2-Methoxyestradiol-Induced Apoptosis in Human Neuroblastoma Cells","volume":"313","author":"Zhang","year":"2011","journal-title":"Cancer Lett."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"90","DOI":"10.1016\/j.bcp.2014.07.017","article-title":"Targeting antioxidants for cancer therapy","volume":"92","author":"Glasauer","year":"2014","journal-title":"Biochem. Pharmacol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"479","DOI":"10.3109\/10715761003667554","article-title":"Reactive oxygen species in cancer","volume":"44","author":"Liou","year":"2010","journal-title":"Free Radic. Res."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Peana, M., Pelucelli, A., Chasapis, C.T., Perlepes, S.P., Bekiari, V., Medici, S., and Zoroddu, M.A. (2023). Biological Effects of Human Exposure to Environmental Cadmium. Biomolecules, 13.","DOI":"10.3390\/biom13010036"},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1016\/j.steroids.2014.08.006","article-title":"Mechanisms of estrogen carcinogenesis: The role of E2\/E1-quinone metabolites suggests new approaches to preventive intervention\u2014A review","volume":"99","author":"Yager","year":"2015","journal-title":"Steroids"},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"48","DOI":"10.3109\/15376516.2014.985353","article-title":"Cadmium induces reactive oxygen species-dependent apoptosis in MCF-7 human breast cancer cell line","volume":"25","author":"Khojastehfar","year":"2015","journal-title":"Toxicol. Mech. Methods"},{"key":"ref_44","doi-asserted-by":"crossref","unstructured":"Singh, R.R., and Reindl, K.M. (2021). Glutathione S-Transferases in Cancer. Antioxidants, 10.","DOI":"10.3390\/antiox10050701"},{"key":"ref_45","doi-asserted-by":"crossref","unstructured":"Kalinina, E. (2024). Glutathione-Dependent Pathways in Cancer Cells. Int. J. Mol. Sci., 25.","DOI":"10.3390\/ijms25158423"},{"key":"ref_46","first-page":"921","article-title":"GST-pi Expression Correlates with Oxidative Stress and Apoptosis in Breast Cancer","volume":"12","author":"Huang","year":"2004","journal-title":"Oncol. Rep."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1106","DOI":"10.1038\/modpathol.2012.60","article-title":"The Prognostic and Predictive Power of Redox Protein Expression for Anthracycline-Based Chemotherapy Response in Locally Advanced Breast Cancer","volume":"25","author":"Woolston","year":"2012","journal-title":"Mod. Pathol."},{"key":"ref_48","doi-asserted-by":"crossref","unstructured":"Gu, X., Mu, C., Zheng, R., Zhang, Z., Zhang, Q., and Liang, T. (2024). The Cancer Antioxidant Regulation System in Therapeutic Resistance. Antioxidants, 13.","DOI":"10.3390\/antiox13070778"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"117360","DOI":"10.1016\/j.taap.2025.117360","article-title":"Interactions between Cadmium and 17\u03b2-Estradiol at Physiologically Relevant Levels Evoke Unsynchronized Events in MCF-7 Breast Cancer Cells: Impaired Cell Growth and Activation of Estrogen Receptor \u03b1-Related Pathways","volume":"500","author":"Kanameda","year":"2025","journal-title":"Toxicol. Appl. Pharmacol."},{"key":"ref_50","first-page":"241","article-title":"Comparison of methods for evaluating drug-drug interaction","volume":"2","author":"Zhao","year":"2010","journal-title":"Front. Biosci."},{"key":"ref_51","doi-asserted-by":"crossref","first-page":"7130","DOI":"10.1016\/S0021-9258(19)42083-8","article-title":"Glutathione S-transferases: The first enzymatic step in mercapturic acid formation","volume":"249","author":"Habig","year":"1974","journal-title":"J. Biol. Chem."}],"container-title":["Pharmaceuticals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8247\/19\/7\/1001\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T00:55:28Z","timestamp":1782694528000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8247\/19\/7\/1001"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6,28]]},"references-count":51,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2026,7]]}},"alternative-id":["ph19071001"],"URL":"https:\/\/doi.org\/10.3390\/ph19071001","relation":{},"ISSN":["1424-8247"],"issn-type":[{"value":"1424-8247","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6,28]]}}}