Diminished carcinogen detoxification is a novel mechanism for hypoxia-inducible factor 1-mediated genetic instability.
The hypoxia-inducible factor 1 (HIF-1) pathway is induced in many tumors and associated with poorer outcome. The hypoxia-responsive transcription factor HIF-1alpha dimerizes with the aryl hydrocarbon receptor nuclear translocator (ARNT), which is also an important binding partner for the aryl hydrocarbon receptor (AhR). AhR is an important mediator in the metabolic activation and detoxification of carcinogens, such as the environmental pollutant benzo[a]pyrene (BaP). We hypothesized that HIF-1alpha activation attenuates BaP-induced AhR-mediated gene expression, which may lead to increased genetic instability and malignant progression. Human lung carcinoma cells (A549) were simultaneously stimulated with CoCl(2), which leads to HIF-1alpha stabilization and varying concentrations of BaP. Both quantitative PCR and immunoblot analysis indicated that induction of the hypoxia response pathway significantly reduced the levels of AhR downstream targets CYP1A1 and CYP1B1 and AhR protein binding to ARNT. We further demonstrate that the BaP-induced hypoxanthine-guanine phosphoribosyltransferase mutation frequency and gamma-H2AX foci were markedly amplified when the HIF-1 pathway was induced. BaP-DNA adducts were only marginally increased, and transient strand breaks were diminished by HIF-1 induction, indicating changes in DNA repair. These data indicate that concurrent exposure of tumor cells to hypoxia and exogenous genotoxins can enhance genetic instability.
Schults
Marten A
MA
Department of Health Risk Analysis and Toxicology, NUTRIM Research Institute, The Netherlands.
Timmermans
Leen
L
Godschalk
Roger W
RW
Theys
Jan
J
Wouters
Bradly G
BG
van Schooten
Frederik J
FJ
Chiu
Roland K
RK
D001189:Aryl Hydrocarbon Hydroxylases; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001564:Benzo(a)pyrene / Q000493:pharmacokinetics*; D015153:Blotting, Western; D002273:Carcinogens / Q000493:pharmacokinetics*; D003035:Cobalt / Q000494:pharmacology; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D018736:DNA Adducts / Q000502:physiology*; D004249:DNA Damage / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics / Q000378:metabolism; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D047468:Immunoprecipitation; D008658:Inactivation, Metabolic; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
D002273:Carcinogens; D018736:DNA Adducts; C468783:H2AX protein, human; C497442:HIF1A protein, human; D006657:Histones; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; C056612:benzo(a)pyrene-DNA adduct; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D001564:Benzo(a)pyrene; D003035:Cobalt; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1; D007041:Hypoxanthine Phosphoribosyltransferase; C018021:cobaltous chloride