Cytochrome P450 expression and metabolic activation of cooked food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in MCF10A breast epithelial cells

Thomas, Ronald D.; Green, Mario R.; Wilson, Cornelia M.; Weckle, Amy; Duanmu, Zhengbo; Kocarek, Thomas A.; Runge‐Morris, Melissa

doi:10.1016/j.cbi.2006.01.007

Cited by 26 publications

(18 citation statements)

References 42 publications

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“…In comparison, in an earlier study in which we profiled the expression of cytochrome P450 transcripts in MCF10A cells, two cytochromes P450, CYP1A1 and CYP1S1, were expressed in preconfluent MCF10A cells but not in confluent MCF10A cells (Thomas et al, 2006). Because both of these cytochromes P450 are transcriptional targets of the AhR (Rivera et al, 2002), this finding suggests that the AhR is active in preconfluent MCF10A cells but inactive in confluent MCF10A cells.…”

Section: Introductionmentioning

confidence: 48%

“…As described in the Introduction, confluence-mediated SULT1E1 up-regulation is mirrored by down-regulation of two cytochromes P450, CYP1A1 and CYP1S1, that are known transcriptional targets of the AhR (Thomas et al, 2006), suggesting that the AhR might provide the mechanistic link between these phenomena. Using real-time RT-PCR, we confirmed that CYP1A1 mRNA content was significantly higher in preconfluent MCF10A cells than in confluent cells (Fig.…”

Section: Resultsmentioning

confidence: 94%

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Regulation of Estrogen Sulfotransferase Expression by Confluence of MCF10A Breast Epithelial Cells: Role of the Aryl Hydrocarbon Receptor

Fu¹,

Fang²,

Paulsen³

et al. 2011

J Pharmacol Exp Ther

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Estrogen sulfotransferase (SULT1E1) catalyzes the sulfonation of estrogens, which limits estrogen mitogenicity. We recently reported that SULT1E1 expression is low in preconfluent MCF10A human breast epithelial cells but increases when the cells become confluent. Pulse-chase labeling experiments with 5-bromouridine demonstrated that the confluence-mediated increase in SULT1E1 expression was due to increased mRNA synthesis. Because aryl hydrocarbon receptor (AhR) activation has been shown to suppress SULT1E1 expression and loss of cell-cell contact has been shown to activate the AhR in other cell types, we tested whether the confluence-associated changes in SULT1E1 expression were mediated by the AhR. Relative to confluent MCF10A cells, preconfluent cells had higher levels of CYP1A1 mRNA and greater activation of an AhR-responsive luciferase reporter, demonstrating that the AhR was active in the preconfluent cells. AhR and aryl hydrocarbon receptor nuclear translocator mRNA and protein levels were also higher in preconfluent than in confluent cultures. Treatment of preconfluent cells with the AhR antagonist, 3Ј-methoxy-4Ј-nitroflavone (MNF), or AhR knockdown significantly increased SULT1E1 expression. MCF10A cells stably transfected with a luciferase reporter containing ϳ7 kilobases of the SULT1E1 5Ј-flanking region showed both MNF-and confluence-inducible luciferase expression. Preconfluent cells transiently transfected with the reporter showed both MNF treatment-and AhR knockdown-mediated luciferase induction, but mutation of a computationally predicted dioxin response element (DRE) at nucleotide (nt) Ϫ3476 did not attenuate these effects. These results demonstrate that SULT1E1 expression in MCF10A cells is transcriptionally regulated by confluence through a suppressive action of the AhR, which is not mediated through a DRE at nt Ϫ3476.

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Section: Introductionmentioning

confidence: 48%

Section: Resultsmentioning

confidence: 94%

Regulation of Estrogen Sulfotransferase Expression by Confluence of MCF10A Breast Epithelial Cells: Role of the Aryl Hydrocarbon Receptor

Fu¹,

Fang²,

Paulsen³

et al. 2011

J Pharmacol Exp Ther

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“…CYP1A1 has a higher catalytic efficiency than CYP1A2 and CYP1B1 for PhIP metabolism [39]. CYP1A1 and CYP1B1 are present or are inducible in extrahepatic tissues including cells derived from the mammary gland, in which bioactivation of PhIP may contribute to the formation of mutagenic DNA lesions [40]. Our current data show that both the increased level of AhR expression in LTEE MCF-7 cells and the activation of the AhR by TCDD are associated with increased levels of PhIP:DNA adducts formed in vitro .…”

Section: Discussionmentioning

confidence: 99%

Genetic and epigenetic regulation of AHR gene expression in MCF-7 breast cancer cells: Role of the proximal promoter GC-rich region

Englert¹,

Turesky²,

Han³

et al. 2012

Biochemical Pharmacology

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The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, contributes to carcinogenesis through its role in the regulation of cytochrome P450 1 (CYP1)-catalyzed metabolism of carcinogens. Here, we investigated genetic and epigenetic mechanisms that affect AhR expression. Analyses of the human AHR proximal promoter in MCF-7 human breast cancer cells using luciferase assays and electrophoretic mobility shift assays revealed multiple specificity protein (Sp) 1 binding sequences that are transcriptional activators in vitro. The regulation of AhR expression was evaluated in long-term estrogen exposed (LTEE) MCF-7 cells, which showed increased AhR expression, enhanced CYP1 inducibility, and increased capacity to form DNA adducts when exposed to the dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. The increased AhR expression in LTEE cells was found not to result from increased mRNA stability, differential RNA processing, or decreased DNA methylation. Analysis of the AHR proximal promoter region using chromatin immunoprecipitation confirmed that enhanced expression of AhR in LTEE cells involves changes in histone modifications, notably decreased trimethylation of histone 3, lysine 27. Upon further examination of the GC-rich Sp1-binding region, we confirmed that it contains a polymorphic (GGGGC)n repeat. In a population of newborns from New York State, the allele frequency of (GGGGC)n was n = 4>5≫6, 2. Circular dichroism spectroscopy revealed the ability of sequences of this GC-rich region to form guanine-quadruplex structures in vitro. These studies revealed multiple levels at which AhR expression may be controlled, and offer additional insights into mechanisms regulating AhR expression that can ultimately impact carcinogenesis.

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“…There have been conflicting reports of cytochrome P450 expression in MCF10A cells (Guo et al, 2001;Thomas et al, 2006). Thus, we tested if treatment with physiological concentrations of E 2 and downregulation of QR can lead to an increase in the levels of reactive estrogen metabolites.…”

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confidence: 99%

Protective roles of quinone reductase and tamoxifen against estrogen-induced mammary tumorigenesis

et al. 2006

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We previously reported that antiestrogen-liganded estrogen receptor b (ERb) transcriptionally activates the major detoxifying enzyme quinone reductase (QR) (NAD(P)H:-quinone oxidoreductase). Further studies on the functional role of ERb-mediated upregulation of antioxidative enzymes indicated protective effects against estrogeninduced oxidative DNA damage (ODD). We now report on in vivo and in vitro studies that show that ERbmediated upregulation of QR are involved in the protection against estrogen-induced mammary tumorigenesis. Using the August Copenhagen Irish (ACI) model of estrogen-induced carcinogenesis, we observed that increased ODD and decreased QR expression occur early in the process of estrogen-induced mammary tumorigenesis. Prevention of ACI mammary gland tumorigenesis by tamoxifen was accompanied by decreased ODD and increased QR levels. These correlative findings were supported by our findings that downregulation of QR levels led to increased levels of estrogen quinone metabolites and enhanced transformation potential of 17b-estradiol treated MCF10A non-tumorigenic breast epithelial cells. Concurrent expression of ERb and treatment with 4-hydroxytamoxifen decreased tumorigenic potential of these MCF10A cells. We conclude that upregulation of QR, through induction by tamoxifen, can inhibit estrogen-induced ODD and mammary cell tumorigenesis, representing a possible novel mechanism of tamoxifen prevention against breast cancer.

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Cytochrome P450 expression and metabolic activation of cooked food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in MCF10A breast epithelial cells

Cited by 26 publications

References 42 publications

Regulation of Estrogen Sulfotransferase Expression by Confluence of MCF10A Breast Epithelial Cells: Role of the Aryl Hydrocarbon Receptor

Regulation of Estrogen Sulfotransferase Expression by Confluence of MCF10A Breast Epithelial Cells: Role of the Aryl Hydrocarbon Receptor

Genetic and epigenetic regulation of AHR gene expression in MCF-7 breast cancer cells: Role of the proximal promoter GC-rich region

Protective roles of quinone reductase and tamoxifen against estrogen-induced mammary tumorigenesis

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