Alpha-hydroxytamoxifen is a substrate of hydroxysteroid (alcohol) sulfotransferase, resulting in tamoxifen DNA adducts.
When alpha-hydroxytamoxifen (alpha-OHTAM) was incubated with rat liver hydroxysteroid (alcohol) sulfotransferase a (STa) and 3'-phosphoadenosine 5'-phosphosulfate, (E)-alpha-OHTAM was found to be a better substrate for STa than (Z)-alpha-OHTAM. To explore the formation of tamoxifen (TAM)-derived DNA adducts, DNA was incubated with STa and either (E)-alpha-OHTAM or (Z)-alpha-OHTAM in the presence of 3'-phosphoadenosine 5'-phosphosulfate. Using 32P-postlabeling analysis, the amount of TAM-DNA adducts resulting from (E)-alpha-OHTAM was 29 times higher than that observed with (E)-alpha-OHTAM alone. Using (Z)-alpha-OHTAM and STa, some TAM-DNA adducts were also detected but at levels 6.5 times lower than that observed with (E)-alpha-OHTAM and STa. When compared with standards of stereoisomers of 2'-deoxyguanosine 3'-monophosphate-N2-tamoxifen, the major tamoxifen adduct was identified chromatographically as an epimer of the trans form of alpha-(N2-deoxyguanosinyl)tamoxifen, and the minor adduct was identified as an epimer of the cis form. In the reaction mixture, a conversion from (E)-alpha-OHTAM to (Z)-alpha-OHTAM through the carbocation intermediate was also detected. These results show that sulfation of alpha-OHTAM catalyzed by STa results in the formation of TAM-DNA adducts.
Shibutani
S
S
Department of Pharmacological Sciences, State University of New York at Stony Brook, 11794-8651, USA.
Dasaradhi
L
L
Terashima
I
I
Banoglu
E
E
Duffel
M W
MW
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D018736:DNA Adducts; D005260:Female; D008956:Models, Chemical; D051381:Rats; D017207:Rats, Sprague-Dawley; D015238:Sulfotransferases / Q000378:metabolism*; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*
D018736:DNA Adducts; C110902:alpha-hydroxytamoxifen; D013629:Tamoxifen; D015238:Sulfotransferases; C028152:alcohol sulfotransferase