title: Mechanism of metformin action in MCF-7 and MDA-MB-231 human breast cancer cells involves oxidative stress generation, DNA damage, and transforming growth factor β1 induction.
abstract: The participation of oxidative stress in the mechanism of metformin action in breast cancer remains unclear. We investigated the effects of clinical (6 and 30 μM) and experimental concentrations of metformin (1000 and 5000 μM) in MCF-7 and in MDA-MB-231 cells, verifying cytotoxicity, oxidative stress, DNA damage, and intracellular pathways related to cell growth and survival after 24 h of drug exposure. Clinical concentrations of metformin decreased metabolic activity of MCF-7 cells in the MTT assay, which showed increased oxidative stress and DNA damage, although cell death and impairment in the proliferative capacity were observed only at higher concentrations. The reduction in metabolic activity and proliferation in MDA-MB-231 cells was present only at experimental concentrations after 24 h of drug exposition. Oxidative stress and DNA damage were induced in this cell line at experimental concentrations. The drug decreased cytoplasmic extracellular signal-regulated kinases 1 and 2 (ERK1/2) and AKT and increased nuclear p53 and cytoplasmic transforming growth factor β1 (TGF-β1) in both cell lines. These findings suggest that metformin reduces cell survival by increasing reactive oxygen species, which induce DNA damage and apoptosis. A relationship between the increase in TGF-β1 and p53 levels and the decrease in ERK1/2 and AKT was also observed. These findings suggest the mechanism of action of metformin in both breast cancer cell lineages, whereas cell line specific undergoes redox changes in the cells in which proliferation and survival signaling are modified. Taken together, these results highlight the potential clinical utility of metformin as an adjuvant during the treatment of luminal and triple-negative breast cancer.
authors.affiliation: Laboratory of Molecular Pathology, State University of Londrina, Rodovia Celso Garcia Cid, PR445, Km 380 Campus Universitário, Londrina, CEP 86051-990, Paraná, Brazil.
authors.forename: Poliana Camila
authors.initials: PC
authors.lastname: Marinello
authors.affiliation: Laboratory of Pathophysiology and Muscle Adaptation, State University of Londrina, Londrina, PR, Brazil.
authors.forename: Thamara Nishida Xavier
authors.initials: TN
authors.lastname: da Silva
authors.affiliation: Laboratory of Pathophysiology and Free Radicals, State University of Londrina, Londrina, PR, Brazil.
authors.forename: Carolina
authors.initials: C
authors.lastname: Panis
authors.affiliation: Laboratory of Molecular Pathology, State University of Londrina, Rodovia Celso Garcia Cid, PR445, Km 380 Campus Universitário, Londrina, CEP 86051-990, Paraná, Brazil.
authors.forename: Amanda Fouto
authors.initials: AF
authors.lastname: Neves
authors.affiliation: Laboratory of Molecular Pathology, State University of Londrina, Rodovia Celso Garcia Cid, PR445, Km 380 Campus Universitário, Londrina, CEP 86051-990, Paraná, Brazil.
authors.forename: Kaliana Larissa
authors.initials: KL
authors.lastname: Machado
authors.affiliation: Laboratory of Pathophysiology and Free Radicals, State University of Londrina, Londrina, PR, Brazil.
authors.forename: Fernando Henrique
authors.initials: FH
authors.lastname: Borges
authors.affiliation: Laboratory of Pathophysiology and Muscle Adaptation, State University of Londrina, Londrina, PR, Brazil.
authors.forename: Flávia Alessandra
authors.initials: FA
authors.lastname: Guarnier
authors.affiliation: Laboratory of Molecular Pathology, State University of Londrina, Rodovia Celso Garcia Cid, PR445, Km 380 Campus Universitário, Londrina, CEP 86051-990, Paraná, Brazil.
authors.forename: Sara Santos
authors.initials: SS
authors.lastname: Bernardes
authors.affiliation: Brazilian National Cancer Institute, INCA, Rio de Janeiro, Brazil.
authors.forename: Júlio Cesar Madureira
authors.initials: JC
authors.lastname: de-Freitas-Junior
authors.affiliation: Brazilian National Cancer Institute, INCA, Rio de Janeiro, Brazil.
authors.forename: José Andrés
authors.initials: JA
authors.lastname: Morgado-Díaz
authors.affiliation: Laboratory of Molecular Pathology, State University of Londrina, Rodovia Celso Garcia Cid, PR445, Km 380 Campus Universitário, Londrina, CEP 86051-990, Paraná, Brazil.
authors.forename: Rodrigo Cabral
authors.initials: RC
authors.lastname: Luiz
authors.affiliation: Laboratory of Pathophysiology and Free Radicals, State University of Londrina, Londrina, PR, Brazil.
authors.forename: Rubens
authors.initials: R
authors.lastname: Cecchini
authors.affiliation: Laboratory of Molecular Pathology, State University of Londrina, Rodovia Celso Garcia Cid, PR445, Km 380 Campus Universitário, Londrina, CEP 86051-990, Paraná, Brazil. alcecchini@yahoo.com.
authors.forename: Alessandra Lourenço
authors.initials: AL
authors.lastname: Cecchini
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004249:DNA Damage / Q000187:drug effects; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D061986:MCF-7 Cells; D008687:Metformin / Q000008:administration & dosage*; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D053773:Transforming Growth Factor beta1 / Q000096:biosynthesis* / Q000235:genetics; D064726:Triple Negative Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000235:genetics
chemical_list: D017382:Reactive Oxygen Species; C508960:TGFB1 protein, human; C495901:TP53 protein, human; D053773:Transforming Growth Factor beta1; D016159:Tumor Suppressor Protein p53; D008687:Metformin
keywords: Breast cancer; MCF-7; MDA-MB-231; Metformin; Oxidative stress