RT Journal Article SR Electronic T1 FORMATION OF TAMOXIFEN-DNA ADDUCTS VIA O-SULFONATION, NOT O-ACETYLATION, OF α-HYDROXYTAMOXIFEN IN RAT AND HUMAN LIVERS JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 1673 OP 1678 DO 10.1124/dmd.105.005330 VO 33 IS 11 A1 Sung Yeon Kim A1 Y. R. Santosh Laxmi A1 Naomi Suzuki A1 Kenichiro Ogura A1 Tadashi Watabe A1 Michael W. Duffel A1 Shinya Shibutani YR 2005 UL http://dmd.aspetjournals.org/content/33/11/1673.abstract AB Tamoxifen (TAM) is used as the standard endocrine therapy for breast cancer patients and as a chemopreventive agent for women at high risk for this disease. Unfortunately, treatment of TAM increases the incidence of endometrial cancer; this may be due to the genotoxic damage induced by TAM metabolites. Formation of TAM-DNA adducts in rat liver correlates with the development of hepatocarcinoma. TAM-DNA adducts are proposed to be formed through O-sulfonation and/or O-acetylation of α-hydroxylated TAM and its metabolites. However, the role of O-sulfonation and O-acetylation in the formation of TAM-DNA adducts has not been extensively investigated. Rat or human hydroxysteroid sulfotransferases (HST), acetyltransferases, and liver cytosol were incubated with calf thymus DNA, α-OHTAM, and either 3′-phosphoadenosine 5′-phosphosulfate (PAPS) or acetyl coenzyme A (acetyl-CoA) as a cofactor and analyzed for TAM-DNA adduct formation, using 32P postlableling/polyacrylamide gel electrophoresis analysis. TAM-DNA adduct was formed when PAPS, not acetyl-CoA, was used. No TAM-DNA adducts were produced using human N-acetyltransferase I and II. HST antibody inhibited approximately 90% of TAM-DNA adduct formation generated by the cytosol or HST, suggesting that HST is primarily involved in the formation of TAM-DNA adducts. The formation of TAM-DNA adducts with rat liver cytosol and HST was much higher than that of human liver cytosol and HST. Our results indicate that TAM-DNA adducts are formed via O-sulfonation, not O-acetylation, of α-hydroxylated TAM and its metabolites. The American Society for Pharmacology and Experimental Therapeutics