Mutagenic properties of estrogen quinone-derived DNA adducts in simian kidney cells

DNA damage caused by catechol estrogens has been shown to play an etiologic role in tumor formation. Catechol estrogens are reactive to DNA and form s everal DNA adducts via their quinone forms. To explore the mutagenic proper ties of 2-hydroxyestrogen-derived DNA adducts in mammalian cells, N-2-(2-hy droxyestrogen-6-yl)-2 ' -deoxyguanosine and N-6-(2-hydroxyestrogen-6-yl)-2 ' -deoxyaden adducts induced by quinones of 2-hydroxyestrone, 2-hydroxyestr adiol, or 2-hydroxyestriol were incorporated site-specifically into the oli godeoxynucleotides (5 ' TCCTCCTC (X) under bar CCTCTC, where X is dG, dA, 2 -OHEN2-dG, or 2-OHE-N-6-dA). The modified oligodeoxynucleotides were insert ed into single-stranded phagemid vectors followed by transfection into simi an kidney (COS-7) cells. Preferential incorporation of dCMP, the correct ba se, was observed opposite all 2-OHE-N-2-dG adducts. Only targeted G --> T t ransversions were detected; the highest mutation frequency (18.2%) was obse rved opposite the 2-OHE2-N-2-dG adduct, followed by 2-OHE1-N-2-dG (4.4%) an d 2-OHE3-N-2-dC (1.3%). When 2-OHE-N6-dA adducts were used, preferential in corporation of dTMP, the correct base, was observed. Targeted mutations rep resenting A --> T transversions were detected, accompanied by small numbers of A --> G transitions. The highest mutation frequencies were observed wit h 2-OHE1-N-6-dA and 2-OHE3-N-6-dA (14.5 and 14.1%, respectively), while 2-O HE2-N-6-dA exhibited a mutation frequency of only 6.0%. No mutations were d etected with vectors containing unmodified oligodeoxynucleotides. Thus, 2-O HE quinone-derived DNA adducts are mutagenic, generating primarily G --> T and A --> T mutations in mammalian cells. The mutational frequency varied d epending on the nature of the 2-OHE moiety.