The major concern regarding estrogen replacement therapy (ERT) is the significant increase in the risk of breast cancer that accompanies long-term use. The most commonly used formulation for ERT is Premarin, a preparation consisting largely of B-ring unsaturated estrogens including conjugated forms of equilin (Eq) and equilenin (Eqn). Our preliminary studies show Ah-receptor-regulated metabolism of Eqn to 4-hydroxylated metabolites in several human breast-derived cell lines expressing cytochrome P4501B1 (CYP1Bl). Semiquinones and quinones derived from these 4-hydroxy metabolites, which are adductive and lead to free radical production, may be involved in carcinogenesis. We hypothesize that estrogens are involved in both the initiation and promotion phases of carcinogenesis, and that aromaticity of the B-ring of steroidal estrogens increases carcinogenic potency. Our broad, long-term goal is to determine whether steroidal estrogens, including the B-ring unsaturated estrogens, Eq and Eqn, are carcinogenic through metabolic activation via catechol estrogens.
0ur Specific Aims are to: 1) Characterize Eq and Eqn metabolism in a series of immortalized tumor- and non-tumor-derived human breast-cell lines. Pathways of Eq and Eqn bioactivation involving hydrolysis of conjugates, reduction to 17beta-dihydro forms and hydroxyation to catechol estrogens will be investigated. 2) Determine the catechol synthetic activities of human cytochromes P450 of the CYP1, CYP2, and CYP3 families with Eq, Eqn, and their 17alpha- and 17beta-dihydro forms as substrates. 3) Establish transgenic mouse lines expressing human CYP1B1 in the mammary epithelium, 4) Determine the effects of treatment with Eq and Eqn on DNA damage and the incidence of mammary-gland tumors in human CYP1B1-transgenic mice. The studies described here will provide novel results regarding the metabolism of the B-ring unsaturated estrogens by human enzymes in breast epithelial cells, and may provide mechanistic data supporting a role of metabolic activation of Eq, Eqn, and endogenous in the initiation of carcinogenesis in the human breast.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA081243-03
Application #
6489301
Study Section
Special Emphasis Panel (ZRG1-SSS-N (01))
Program Officer
Yang, Shen K
Project Start
2000-01-07
Project End
2003-12-31
Budget Start
2002-01-01
Budget End
2002-12-31
Support Year
3
Fiscal Year
2002
Total Cost
$233,720
Indirect Cost
Name
Wadsworth Center
Department
Type
DUNS #
110521739
City
Menands
State
NY
Country
United States
Zip Code
12204
Spink, Barbara C; Bloom, Michael S; Wu, Susan et al. (2015) Analysis of the AHR gene proximal promoter GGGGC-repeat polymorphism in lung, breast, and colon cancer. Toxicol Appl Pharmacol 282:30-41
Spink, Barbara C; Bennett, James A; Lostritto, Nicole et al. (2013) Expression of the aryl hydrocarbon receptor is not required for the proliferation, migration, invasion, or estrogen-dependent tumorigenesis of MCF-7 breast cancer cells. Mol Carcinog 52:544-54
Englert, Neal A; Turesky, Robert J; Han, Weiguo et al. (2012) Genetic and epigenetic regulation of AHR gene expression in MCF-7 breast cancer cells: role of the proximal promoter GC-rich region. Biochem Pharmacol 84:722-35
Weng, Yan; Xie, Fang; Xu, Li et al. (2010) Analysis of testosterone and dihydrotestosterone in mouse tissues by liquid chromatography-electrospray ionization-tandem mass spectrometry. Anal Biochem 402:121-8
Xu, Li; Spink, David C (2008) Analysis of steroidal estrogens as pyridine-3-sulfonyl derivatives by liquid chromatography electrospray tandem mass spectrometry. Anal Biochem 375:105-14
Spink, David C; Wu, Susan J; Spink, Barbara C et al. (2008) Induction of CYP1A1 and CYP1B1 by benzo(k)fluoranthene and benzo(a)pyrene in T-47D human breast cancer cells: roles of PAH interactions and PAH metabolites. Toxicol Appl Pharmacol 226:213-24
Xu, Li; Spink, David C (2007) 1,2-Dimethylimidazole-4-sulfonyl chloride, a novel derivatization reagent for the analysis of phenolic compounds by liquid chromatography electrospray tandem mass spectrometry: application to 1-hydroxypyrene in human urine. J Chromatogr B Analyt Technol Biomed Life Sci 855:159-65
Spink, Barbara C; Cole, Richard W; Katz, Barbara H et al. (2006) Inhibition of MCF-7 breast cancer cell proliferation by MCF-10A breast epithelial cells in coculture. Cell Biol Int 30:227-38
Oenga, Gideon N; Spink, David C; Carpenter, David O (2004) TCDD and PCBs inhibit breast cancer cell proliferation in vitro. Toxicol In Vitro 18:811-9
Spink, David C; Katz, Barbara H; Hussain, Mirza M et al. (2003) Estrogen regulates Ah responsiveness in MCF-7 breast cancer cells. Carcinogenesis 24:1941-50

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