title: The aryl hydrocarbon receptor-dependent deregulation of cell cycle control induced by polycyclic aromatic hydrocarbons in rat liver epithelial cells.
abstract: Disruption of cell proliferation control by polycyclic aromatic hydrocarbons (PAHs) may contribute to their carcinogenicity. We investigated role of the aryl hydrocarbon receptor (AhR) in disruption of contact inhibition in rat liver epithelial WB-F344 'stem-like' cells, induced by the weakly mutagenic benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF) and by the strongly mutagenic benzo[a]pyrene (BaP). There were significant differences between the effects of BaA and BbF, and those of the strongly genotoxic BaP. Both BaA and BbF increased percentage of cells entering S-phase and cell numbers, associated with an increased expression of Cyclin A and Cyclin A/cdk2 complex activity. Their effects were significantly reduced in cells expressing a dominant-negative AhR mutant (dnAhR). Roscovitine, a chemical inhibitor of cdk2, abolished the induction of cell proliferation by BbF. However, neither BaA nor BbF modulated expression of the principal cdk inhibitor involved in maintenance of contact inhibition, p27(Kip1), or pRb phosphorylation. The strongly mutagenic BaP induced apoptosis, a decrease in total cell numbers and significantly higher percentage of cells entering S-phase than either BaA or BbF. Given that BaP induced high levels of Cyclin A/cdk2 activity, downregulation of p27(Kip1) and hyperphosphorylation of pRb, the accumulation of cells in S-phase was probably due to cell proliferation, although S-phase arrest due to blocked replication forks can not be excluded. Both types of effects of BaP were significantly attenuated in dnAhR cells. Transfection of WB-F344 cells with siRNA targeted against AhR decreased induction of Cyclin A induced by BbF or BaP, further supporting the role of AhR in proliferative effects of PAHs. This suggest that activation of AhR plays a significant role both in disruption of contact inhibition by weakly mutagenic PAHs and in genotoxic effects of BaP possibly leading to enhanced cell proliferation. Thus, PAHs may increase proliferative rate and the likelihood of fixation of mutations.
authors.affiliation: Laboratory of Cytokinetics, Institute of Biophysics, 612 65 Brno, Czech Republic.
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Andrysík
authors.forename: Jan
authors.initials: J
authors.lastname: Vondrácek
authors.forename: Miroslav
authors.initials: M
authors.lastname: Machala
authors.forename: Pavel
authors.initials: P
authors.lastname: Krcmár
authors.forename: Lenka
authors.initials: L
authors.lastname: Svihálková-Sindlerová
authors.forename: Anne
authors.initials: A
authors.lastname: Kranz
authors.forename: Carsten
authors.initials: C
authors.lastname: Weiss
authors.forename: Dagmar
authors.initials: D
authors.lastname: Faust
authors.forename: Alois
authors.initials: A
authors.lastname: Kozubík
authors.forename: Cornelia
authors.initials: C
authors.lastname: Dietrich
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001483:Base Sequence; D001551:Benz(a)Anthracenes / Q000633:toxicity; D001564:Benzo(a)pyrene / Q000633:toxicity; D002453:Cell Cycle / Q000187:drug effects* / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D019925:Cyclin A / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005449:Fluorenes / Q000633:toxicity; D015870:Gene Expression / Q000187:drug effects; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D046912:Multiprotein Complexes; D009153:Mutagens / Q000633:toxicity; D009154:Mutation; D011084:Polycyclic Aromatic Hydrocarbons / Q000633:toxicity*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001551:Benz(a)Anthracenes; D018797:Cell Cycle Proteins; D019925:Cyclin A; D005449:Fluorenes; D046912:Multiprotein Complexes; D009153:Mutagens; D011084:Polycyclic Aromatic Hydrocarbons; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D018336:Receptors, Aryl Hydrocarbon; D001564:Benzo(a)pyrene; C030935:benz(a)anthracene; D019363:Cytochrome P-450 CYP1A1; C495892:Cdk2 protein, rat; D051357:Cyclin-Dependent Kinase 2; C006703:benzo(b)fluoranthene