title: Benzo(a)pyrene quinones increase cell proliferation, generate reactive oxygen species, and transactivate the epidermal growth factor receptor in breast epithelial cells.
abstract: Polycyclic aromatic hydrocarbons, such as benzo(a)pyrene (BaP), are known mammary carcinogens in rodents and may be involved in human breast cancer. We have reported previously that BaP can mimic growth factor signaling and increase cell proliferation in primary human mammary epithelial cells and the human mammary epithelial cell line MCF-10A. BaP-quinones (BPQs) are important metabolites of BaP that have been associated with the production of reactive oxygen species. Using a model of epidermal growth factor (EGF) withdrawal in MCF-10A, we hypothesized that production of reactive oxygen species by BPQs could lead to the activation of the EGF receptor (EGFR). Here, we demonstrate through electron paramagnetic resonance spectroscopy and flow cytometry that 1,6-BPQ and 3,6-BPQ produce superoxide anion and hydrogen peroxide in MCF-10A cells. Furthermore, we show that BPQs increase EGFR, Akt, and extracellular signal-regulated kinase activity, leading to increased cell number in the absence of EGF. The BPQ-induced EGFR activity and associated cell proliferation were attenuated by the EGFR inhibitor AG1478, as well as by the antioxidant N-acetyl cysteine. Overexpression of catalase, but not Cu/Zn superoxide dismutase, reduced the extent of BPQ-dependent increased cell number and EGFR pathway activation. Moreover, the direct treatment of MCF-10A cells with hydrogen peroxide enhanced EGFR, Akt, and extracellular-regulated kinase phosphorylation that could be similarly inhibited by AG1478, N-acetyl cysteine, and catalase. Taken together, these data indicate that BPQs, through the generation of hydrogen peroxide, activate the EGFR in MCF-10A cells, leading to increased cell number under EGF-deficient conditions.
authors: College of Pharmacy Toxicology Program, The University of New Mexico, 2502 Marble NE, Albuquerque, NM 87131, USA.
authors: Andrew D
authors: AD
authors: Burdick
authors: John W
authors: JW
authors: Davis
authors: Ke Jian
authors: KJ
authors: Liu
authors: Laurie G
authors: LG
authors: Hudson
authors: Honglian
authors: H
authors: Shi
authors: Michael L
authors: ML
authors: Monske
authors: Scott W
authors: SW
authors: Burchiel
mesh_terms: D001580:Benzopyrenes / Q000633:toxicity*; D001940:Breast / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D001943:Breast Neoplasms / Q000139:chemically induced / Q000378:metabolism; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D004578:Electron Spin Resonance Spectroscopy; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000172:deficiency; D066246:ErbB Receptors / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018384:Oxidative Stress; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D015533:Transcriptional Activation
chemical_list: D001580:Benzopyrenes; D011518:Proto-Oncogene Proteins; D017382:Reactive Oxygen Species; C030233:benzo(a)pyrene-1,6-quinone; D004815:Epidermal Growth Factor; D006861:Hydrogen Peroxide; C018003:benzo(a)pyrene-3,6-quinone; D066246:ErbB Receptors; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases