| Synthesis and reactivity of a potential carcinogenic metabolite of tamoxifen: 3,4-dihydroxytamoxifen-o-quinone. | |
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MedLine Citation:
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PMID: 10649967 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Although tamoxifen is approved for the treatment of hormone-dependent breast cancer as well as for the prevention of breast cancer in high-risk women, several studies in animal models have shown that tamoxifen is heptocarcinogenic, and in humans, tamoxifen has been associated with an increased risk of endometrial cancer. One potential mechanism of tamoxifen carcinogenesis could involve metabolism of tamoxifen to 3,4-dihydroxytamoxifen followed by oxidation to a highly reactive o-quinone which has the potential to alkylate and/or oxidize cellular macromolecules in vivo. In the study presented here, we synthesized the 3,4-dihydroxytamoxifen, prepared its o-quinone chemically and enzymatically, and studied the reactivity of the o-quinone with GSH and deoxynucleosides. The E (trans) and Z (cis) isomers of 3,4-dihydroxytamoxifen were synthesized using a concise synthetic pathway (four steps). This approach is based on the McMurry reaction between the key 4-(2-chloroethoxy)-3,4-methylenedioxybenzophenone and propiophenone, followed by selective removal of the methylenedioxy ring of (E, Z)-1-[4-[2-(N,N-dimethylamino)ethoxy]phenyl]-1-(3, 4-methylenedioxyphenyl)-2-phenyl-1-butene with BCl(3). Oxidation of 3,4-dihydroxytamoxifen by activated silver oxide or tyrosinase gave 3,4-dihydroxytamoxifen-o-quinone as a mixture of E and Z isomers. The resulting o-quinone has a half-life of approximately 80 min under physiological conditions. Reaction of the o-quinone with GSH gave two di-GSH conjugates and three mono GSH conjugates. Incubation of 3,4-dihydroxytamoxifen with GSH in the presence of microsomal P450 gave the same GSH conjugates which were also detected in incubations with human breast cancer cells (MCF-7). Reaction of 3, 4-dihydroxytamoxifen-o-quinone with deoxynucleosides gave only thymidine and deoxyguanosine adducts; neither deoxyadenosine nor deoxycytosine adducts were detected. Preliminary studies conducted with human breast cancer cell lines showed that 3, 4-dihydroxytamoxifen exhibited cytotoxic potency similar to that of 4-hydroxytamoxifen and tamoxifen in an estrogen receptor negative (ER(-)) cell line (MDA-MB-231); however, in the ER(+) cell line (MCF-7), the catechol metabolite was about half as toxic as the other two compounds. Finally, in the presence of microsomes and GSH, 4-hydroxytamoxifen gave predominantly quinone methide GSH conjugates as reported in the previous paper in this issue [Fan, P. W., et al. (2000) Chem. Res. Toxicol. 13, XX-XX]. However, in the presence of tyrosinase and GSH, 4-hydroxytamoxifen was primarily converted to o-quinone GSH conjugates. These results suggest that the catechol metabolite of tamoxifen has the potential to cause cytotoxicity in vivo through formation of 3,4-dihydroxytamoxifen-o-quinone. |
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Authors:
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F Zhang; P W Fan; X Liu; L Shen; R B van Breeman; J L Bolton |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, P.H.S. |
Journal Detail:
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Title: Chemical research in toxicology Volume: 13 ISSN: 0893-228X ISO Abbreviation: Chem. Res. Toxicol. Publication Date: 2000 Jan |
Date Detail:
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Created Date: 2000-03-10 Completed Date: 2000-03-10 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 8807448 Medline TA: Chem Res Toxicol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 53-62 Citation Subset: IM |
Affiliation:
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Department of Medicinal Chemistry and Pharmacognosy (M/C 781), College of Pharmacy, University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612-7231, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Breast Neoplasms / drug therapy Carcinogens / chemical synthesis*, metabolism, toxicity* Chromatography, High Pressure Liquid Deoxyguanosine / chemistry, metabolism Glutathione / chemistry, metabolism Humans Mass Spectrometry Microsomes, Liver / metabolism Monophenol Monooxygenase / metabolism Nuclear Magnetic Resonance, Biomolecular Oxidation-Reduction Quinones / chemical synthesis*, chemistry, metabolism, toxicity* Rats Tamoxifen / analogs & derivatives*, chemical synthesis, chemistry, metabolism, toxicity* Thymidine / chemistry, metabolism Tumor Cells, Cultured |
| Grant Support | |
ID/Acronym/Agency:
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CA79870/CA/NCI NIH HHS; CA83124/CA/NCI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/3,4-dihydroxytamoxifen; 0/3,4-dihydroxytamoxifen-o-quinone; 0/Carcinogens; 0/Quinones; 10540-29-1/Tamoxifen; 50-89-5/Thymidine; 70-18-8/Glutathione; 961-07-9/Deoxyguanosine; EC 1.14.18.1/Monophenol Monooxygenase |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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