Molecular characteristics of catechol estrogen quinones in reactions with deoxyribonucleosides

Estrogens can have two roles in the induction of cancer: stimulating proliferation of cells by receptor-mediated processes, and generating electrophilic species that can covalently bind to DNA. The latter role is thought to proceed through catechol estrogen metabolites, which can be oxidized to o-quinones that bind to DNA. Four estrogen-deoxyribonucleoside adducts were synthesized by reaction of estrone 3,4-quinone (E₁-3,4-Q), 17β-estradiol 3,4-quinone (E₂-3,4-Q), or estrone 2,3-quinone (E₁-2,3-Q) with deoxyguanosine (dG) or deoxyadenosine (dA) in CH₃CO₂H/H₂O (1:1). Reaction of E₁-3,4-Q or E₂-3,4-Q with dG produced specifically 7-[4-hydroxyestron-1(α,β,)-yl]guanine (4-OHE₁-1(α,β)-N7Gua) or 7-[4-hydroxyestradiol-1(α,β)-yl]guanine (4-OHE₂-1(α,β)-N7Gua), respectively, in 40% yield, with loss of deoxyribose. These two quinones did not react with dA, deoxycytidine, or thymidine. When E₁-2,3-Q was reacted with dG or dA, N²-(2-hydroxyestron-6-yl)deoxyguanosine (2-OHE₁-6-N²dG, 10% yield) and N⁶-(2-hydroxyestron-6-yl)deoxyadenosine (2-OHE₁-6-N⁶dA, 80% yield), respectively, were formed. These adducts provide insight into the type of DNA damage that can be caused by o-quinones of the catechol estrogens. The estrogen 3,4-quinones are expected to produce depurinating guanine adducts that are lost from DNA, generating apurinic sites, whereas the 2,3-quinones would form stable adducts that remain in DNA, unless repaired. The adducts reported here will be used as references in studies to elucidate the structure of estrogen adducts in biological systems.