Journal Article

Identification of hepatic tamoxifen–DNA adducts in mice: α-(<i>N<sup>2</sup></i>-deoxyguanosinyl)tamoxifen and α-(<i>N<sup>2</sup></i>-deoxyguanosinyl)tamoxifen <i>N</i>-oxide

Atsushi Umemoto, Yasumasa Monden, Masato Suwa, Yoshikazu Kanno, Masanobu Suzuki, Chun-Xing Lin, Yuji Ueyama, Md.Abdul Momen, Anisetti Ravindernath, Shinya Shibutani and Kansei Komaki

in Carcinogenesis

Volume 21, issue 9, pages 1737-1744
Published in print September 2000 | ISSN: 0143-3334
Published online September 2000 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/21.9.1737
Identification of hepatic tamoxifen–DNA adducts in mice: α-(N2-deoxyguanosinyl)tamoxifen and α-(N2-deoxyguanosinyl)tamoxifen N-oxide

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Tamoxifen–DNA adducts detected in the liver of mice treated with tamoxifen have not yet been identified. In the present study a new type of tamoxifen–DNA adduct, four stereoisomers of α-(N2-deoxyguanosinyl)tamoxifen N-oxide 3′-monophosphate (dG3′P-N2-TAM N-oxide) were prepared as standard DNA adducts by reacting 2′-deoxyguanosine 3′-monophosphate with trans-α-acetoxytamoxifen N-oxide in addition to four stereoisomers of α-(N2-deoxyguano- sinyl)tamoxifen 3′-monophosphate (dG3′P-N2-TAM) that was reported previously. Liquid chromatography-electrospray ionization–mass spectrometry of the reaction products gave the most abundant ion at m/z 731 ([M – H]), which corresponded to dG3′P-N2-TAM N-oxide. The modified products digested by alkaline phosphatase corresponded to the isomers of dG-N2-TAM N-oxide whose structures were identified previously by mass spectrometry and nuclear magnetic resonance. Using these standard markers, we analyzed the hepatic DNA adducts of female DBA/2 mice treated with tamoxifen at a dosage of 120 mg/kg/day for 7 days by 32P-post-labeling coupled with an HPLC/radioactive detector. Mixtures of eight isomers of dG3′P-N2-TAM and dG3′P-N2-TAM N-oxide were separated into six peaks, since each of the cis epimers were not separated under the present HPLC conditions. Nine adducts were detected in all liver samples of mice. An epimer of trans-dG3′P-N2-TAM was detected as the principal DNA adduct at a level of 29.0 adducts/108 nucleotides, which accounted for 53.3% of the total tamoxifen–DNA adducts. Lesser amounts of cis-dG3′P-N2-TAM (2.8%) were also observed. An epimer of the trans-dG3′P-N2-TAM N-oxide (3.9 adducts/108 nucleotides) was detected as the third biggest adduct (7.2% of the total). The cis-dG3′P-N2-TAM N-oxide (0.4 adducts/108 nucleotides) accounted for 0.7% of the total. Thus, dG3′P-N2-TAM and dG3′P-N2-TAM N-oxide were identified in tamoxifen-treated mouse liver.

Keywords: dG, 2′-deoxyguanosine; dG3′P, 2′-deoxyguanosine 3′-mono-phosphate; dG3′P-N2-TAM N-oxide, α-(N2-deoxyguanosinyl)tamoxifen N-oxide 3′-monophosphate; dG3′P-N2-TAM, α-(N2-deoxyguanosinyl)tamoxifen 3′-mono-phosphate; dG-N2-TAM N-oxide, α-(N2-deoxyguanosinyl)tamoxifen N-oxide; ESI-MS, electrospray ionization mass spectrometry.

Journal Article.  4447 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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