IDENTIFICATION OF TAMOXIFEN-DNA ADDUCTS FORMED BY ALPHA-SULFATE TAMOXIFEN AND ALPHA-ACETOXYTAMOXIFEN

alpha-Sulfate trans-tamoxifen and alpha-sulfate cis-tamoxifen were syn thesized as proposed active metabolites of tamoxifen that react with D NA. alpha-Acetoxytamoxifen was prepared as a model-activated form to p roduce a reactive carbocation. Calf thymus DNA was reacted with alpha- hydroxytamoxifen or the activated forms of tamoxifen, and tamoxifen-DN A adducts were analyzed by a P-32-postlabeling method. The reactivity of a-sulfate trans-tamoxifen to DNA was much higher than that of alpha -hydroxytamoxifen. The formation of tamoxifen-DNA adducts induced by a lpha-acetoxytamoxifen and alpha-sulfate cis-tamoxifen was 1100- and 16 00-fold, respectively, higher than that of alpha-hydroxytamoxifen. Bot h alpha-sulfate tamoxifens and alpha-acetoxytamoxifen were highly reac tive to 2'-deoxyguanosine. Four reaction products of dG-tamoxifen were isolated by HPLC and characterized by mass- and proton magnetic reson ance spectroscopy. Fractions 1 and 2 that eluted first were identified as the epimers of trans form of dG-N-2-tamoxifen. Fractions 3 and 4 w ere identified as the epimers of cis form of dG-N-2-tamoxifen. When DN A was reacted with alpha-acetoxytamoxifen in vitro, three isomers of d G-N-2-tamoxifen were detected: fraction 2 was the major adduct while f ractions 1 and 3 were minor adducts.