Suppression of calbindin D28K in estrogen-induced hamster renal tumors

The Journal of Steroid Biochemistry and Molecular Biology

2008

Self Cite

Estrogen metabolism is suggested to play an important role in estrogen-induced breast carcinogenesis. Epidemiologic studies suggest that diets rich in phytoestrogens are associated with a reduced risk of breast cancer. Phytoestrogens are biologically-active plant compounds that structurally mimic 17β-estradiol (E 2 ). We hypothesize that phytoestrogens, may provide protection against breast carcinogenesis by altering the expression of estrogen-metabolizing enzymes cytochrome P450 1A1 (Cyp1A1) and 1B1 (Cyp1B1). Cyp1A1 and Cyp1B1 are responsible for the metabolism of E 2 to generate 2-hydroxyestradiol (2-OHE 2 ) and 4-hydroxyestradiol (4-OHE 2 ), respectively. Studies suggest that 2-OHE 2 and 2-methoxyestradiol may protect against breast carcinogenesis, while 4-OHE 2 is carcinogenic in rodent models. Thus, agents that increase the metabolism of E 2 by Cyp1A1 to produce 2-OHE 2 may have chemoprotective properties. The human immortalized non-neoplastic breast cell line MCF10F was treated with quercetin at 10 and 50 µM concentrations for time-points ranging from 3 to 48 hours. Total RNA and protein were isolated. Real-time PCR was used to measure the expression of Cyp1A1 and Cyp1B1 mRNA. Quercetin treatment produced differential regulation of Cyp1A1 and Cyp1B1 mRNA expression in a time-and dose-dependent manner. Treatment with 10 and 50 µM doses of quercetin produced 6-and 11-times greater inductions of Cyp1A1 mRNA over Cyp1B1 mRNA, respectively. Furthermore, quercetin dramatically increased Cyp1A1 protein levels and only slightly increased Cyp1B1 protein levels in MCF10F cells. Thus, our data suggest that phytoestrogens may provide protection against breast cancer by modulating expression of estrogen-metabolizing genes such that production of the highly carcinogenic estrogen metabolite 4-OHE 2 by Cyp1B1 is reduced and the production of the less genotoxic 2-OHE 2 by Cyp1A1 is increased.

Section: Reverse Transcription and Real-time Pcrmentioning

confidence: 99%

Section: Reverse Transcription and Real-time Pcrmentioning

confidence: 99%

Preferential induction of cytochrome P450 1A1 over cytochrome P450 1B1 in human breast epithelial cells following exposure to quercetin

Mense

Chhabra

The Journal of Steroid Biochemistry and Molecular Biology

2008

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“…Data were analyzed from at least 5 different animals from each group using BioRad iQ5 optical system software version 2.0. The expression of cyclophilin, a housekeeping gene, was used for quantification and standardization purposes whose expression has previously been shown not to be altered by estrogen treatment [67]. The expression of gene of interest relative to cyclophilin was determined by dividing the number of cDNA molecules for the gene of interest by the number of cyclophilin cDNA molecules.…”

Section: Methodsmentioning

confidence: 99%

“…The expression of gene of interest relative to cyclophilin was determined by dividing the number of cDNA molecules for the gene of interest by the number of cyclophilin cDNA molecules. Standards were created for each gene and a standard curve was run on each plate to allow for accurate quantification of cDNA, as reported previously [67].…”

Section: Methodsmentioning

confidence: 99%

Partial Inhibition of Estrogen-Induced Mammary Carcinogenesis in Rats by Tamoxifen: Balance between Oxidant Stress and Estrogen Responsiveness

Singh

2011

PLoS ONE

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Epidemiological and experimental evidences strongly support the role of estrogens in breast tumor development. Both estrogen receptor (ER)-dependent and ER-independent mechanisms are implicated in estrogen-induced breast carcinogenesis. Tamoxifen, a selective estrogen receptor modulator is widely used as chemoprotectant in human breast cancer. It binds to ERs and interferes with normal binding of estrogen to ERs. In the present study, we examined the effect of long-term tamoxifen treatment in the prevention of estrogen-induced breast cancer. Female ACI rats were treated with 17β-estradiol (E2), tamoxifen or with a combination of E2 and tamoxifen for eight months. Tissue levels of oxidative stress markers 8-iso-Prostane F2α (8-isoPGF2α), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase, and oxidative DNA damage marker 8-hydroxydeoxyguanosine (8-OHdG) were quantified in the mammary tissues of all the treatment groups and compared with age-matched controls. Levels of tamoxifen metabolizing enzymes cytochrome P450s as well as estrogen responsive genes were also quantified. At necropsy, breast tumors were detected in 44% of rats co-treated with tamoxifen+E2. No tumors were detected in the sham or tamoxifen only treatment groups whereas in the E2 only treatment group, the tumor incidence was 82%. Co-treatment with tamoxifen decreased GPx and catalase levels; did not completely inhibit E2-mediated oxidative DNA damage and estrogen-responsive genes monoamine oxygenase B1 (MaoB1) and cell death inducing DFF45 like effector C (Cidec) but differentially affected the levels of tamoxifen metabolizing enzymes. In summary, our studies suggest that although tamoxifen treatment inhibits estrogen-induced breast tumor development and increases the latency of tumor development, it does not completely abrogate breast tumor development in a rat model of estrogen-induced breast cancer. The inability of tamoxifen to completely inhibit E2-induced breast carcinogenesis may be because of increased estrogen-mediated oxidant burden.

“…The Pierce BCA Protein Assay kit was used to determine protein concentration of each sample (Pierce, Rockford IL). Eighty microgram total protein was size fractionated on a 12% SDS-polyacrylamide gel, and transferred onto a PVDF membrane (Millipore Corp., Billerica, MA) under standard conditions (Bhat and Epelboym, 2004; Mense et al , 2008a). PVDF membranes were blocked in 5% dry non-fat milk/PBS/0.5% Tween-20 at room temperature for 2 hours.…”

Section: Methodsmentioning

confidence: 99%

Dietary quercetin exacerbates the development of estrogen-induced breast tumors in female ACI rats

Singh

Mense

Toxicology and Applied Pharmacology

et al. 2010

Self Cite

Phytoestrogens are plant compounds that structurally mimic the endogenous estrogen 17β-estradiol (E2). Despite intense investigation, the net effect of phytoestrogen exposure on the breast remains unclear. The objective of the current study was to examine the effects of quercetin on E2-induced breast cancer in vivo. Female ACI rats were given quercetin (2.5 g/kg food) for 8 months. Animals were monitored weekly for palpable tumors, and at the end of the experiment, rats were euthanized, breast tumor and different tissues excised so that they could be examined for histopathologic changes, estrogen metabolic activity and oxidant stress. Quercetin alone did not induce mammary tumors in female ACI rats. However, in rats implanted with E2 pellets, co-exposure to quercetin did not protect rats from E2-induced breast tumor development with 100% of the animals developing breast tumors within 8 months of treatment. No changes in serum quercetin levels were observed in quercetin and quercetin + E2-treated groups at the end of the experiment. Tumor latency was significantly decreased among rats from the quercetin + E2 group relative to those in the E2 group. Catechol-O-methyltransferase (COMT) activity was significantly downregulated in quercetin exposed mammary tissue. Analysis of 8-isoprostane F2α (8-iso-PGF2α) levels as a marker of oxidant stress showed that quercetin did not decrease E2-induced oxidant stress. These results indicate that quercetin (2.5 g/kg food) does not confer protection against breast cancer, does not inhibit E2-induced oxidant stress and may exacerbate breast carcinogenesis in E2-treated ACI rats. Inhibition of COMT activity by quercetin may expose breast cells chronically to E2 and catechol estrogens. This would permit longer exposure times to the carcinogenic metabolites of E2 and chronic exposure to oxidant stress as a result of metabolic redox cycling to estrogen metabolites, and thus quercetin may exacerbate E2-induced breast tumors in female ACI rats.