Identification of tamoxifen-DNA adducts induced by alpha-acetoxy-N-desmethyltamoxifen.
Treatment with tamoxifen increased the risk of endometrial cancers in breast cancer patients and women participating in the chemoprevention study. In our laboratory, tamoxifen-DNA adducts, including alpha-(N(2)-deoxyguanosinyl)tamoxifen (dG-N(2)-TAM), were detected in the endometrium of women taking tamoxifen [Shibutani, S., et al. (1999) Chem. Res. Toxicol. 12, 646-653]. On the basis of recent animal studies, deoxyguanosinyl-N-desmethyltamoxifen (dG-N-desmethylTAM) adducts are also suspected to be formed in the liver. In the study presented here, we synthesized alpha-acetoxy-N-desmethyltamoxifen as a model activated metabolite of N-desmethyltamoxifen. The overall yield of alpha-acetoxy-N-desmethyltamoxifen from alpha-hydroxytamoxifen was approximately 42%. alpha-Acetoxy-N-desmethyltamoxifen was highly reactive to 2'-deoxyguanosine, as was similarly observed for tamoxifen alpha-sulfate. The two reaction products were identified as a mixture of epimers of the trans form or cis form of alpha-(N(2)-deoxyguanosinyl)-N-desmethyltamoxifen (dG-N(2)-N-desmethylTAM) by mass and proton magnetic resonance spectroscopy. In addition, the trans and cis forms of dG 3'-monophosphate-N(2)-N-desmethylTAM were prepared as standard markers for (32)P-postlabeling/HPLC analysis. Using this technique, dG-N(2)-N-desmethylTAM adducts were detected in calf thymus DNA reacted with alpha-acetoxy-N-desmethyltamoxifen.
Kitagawa
M
M
Laboratory of Chemical Biology, Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794-8651, USA.
Ravindernath
A
A
Suzuki
N
N
Rieger
R
R
Terashima
I
I
Umemoto
A
A
Shibutani
S
S
D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D018736:DNA Adducts / Q000032:analysis / Q000378:metabolism*; D004965:Estrogen Antagonists / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D011522:Protons; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism*
D018736:DNA Adducts; D004965:Estrogen Antagonists; D011522:Protons; C105083:alpha-(N(2)-deoxyguanosinyl)tamoxifen; D013629:Tamoxifen