title: Benzo[a]pyrene, but not 2,3,7,8-TCDD, induces G2/M cell cycle arrest, p21CIP1 and p53 phosphorylation in human choriocarcinoma JEG-3 cells: a distinct signaling pathway.
abstract: Maternal cigarette smoking is known to disrupt placental growth and function. The polyaromatic hydrocarbon benzo[a]pyrene (BaP) is a major toxicant in cigarette smoke that has been shown to alter placental cell function. This study compared the effects of the benzo[a]pyrene (BaP) with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the prototype ligand for the aryl hydrocarbon (Ah) receptor, on proliferation and cell cycle progression in the human trophoblastic JEG-3 cell line. BaP, but not TCDD, significantly inhibited proliferation in a dose-dependent manner characterized by G2/M cell cycle phase arrest. No evidence of apoptosis was detected following BaP or TCDD exposure. Immunocytochemistry and Western blot analysis showed that BaP induced expression of nuclear p21CIP1 protein, the major inhibitor of cyclin-dependent kinases. In contrast, CDK1 expression, the main G2 cyclin-dependent kinase, was significantly reduced by 50% with a shift in localization from the nucleus to cytoplasm. Although BaP had no effect on total cellular p53 levels, phosphorylation of p53 at serine 15 (p53 ser-15phos) was markedly increased. The presence of Wortmannin, an inhibitor of PI-3 kinases, decreased BaP-induced p53 ser-15phos, as did the presence of the antioxidant vitamin E. In addition, vitamin E suppressed BaP-induced G2/M arrest without altering the level of induced CYP1A1 protein. Thus, the anti-proliferative effect of BaP involves activation of a p53-dependent pathway involving cell cycle arrest at G2/M, providing evidence of oxidative stress and activation of a DNA damage response pathway in JEG-3 cells.
authors.affiliation: University of Florida, Department of Pharmacology and Therapeutics, 1600 SW Archer Road, P.O. Box 100267, Gainesville, FL 32610-0267, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Drukteinis
authors.forename: T
authors.initials: T
authors.lastname: Medrano
authors.forename: E A
authors.initials: EA
authors.lastname: Ablordeppey
authors.forename: J M
authors.initials: JM
authors.lastname: Kitzman
authors.forename: K T
authors.initials: KT
authors.lastname: Shiverick
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D001564:Benzo(a)pyrene / Q000633:toxicity*; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000096:biosynthesis*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002822:Choriocarcinoma / Q000378:metabolism* / Q000473:pathology*; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004249:DNA Damage; D005260:Female; D006801:Humans; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation; D010920:Placenta / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D011247:Pregnancy; D015398:Signal Transduction / Q000187:drug effects; D012907:Smoking / Q000009:adverse effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014594:Uterine Neoplasms / Q000378:metabolism* / Q000473:pathology*; D014810:Vitamin E / Q000494:pharmacology
chemical_list: D000975:Antioxidants; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D000072317:Polychlorinated Dibenzodioxins; D016159:Tumor Suppressor Protein p53; D014810:Vitamin E; D001564:Benzo(a)pyrene; D016203:CDC2 Protein Kinase