Miscoding potential of tamoxifen-derived DNA adducts: alpha-(N2-deoxyguanosinyl)tamoxifen.
The treatment of tamoxifen, widely used as adjuvant chemotherapy for breast cancer, increases significantly the risk of developing endometrial cancer. The miscoding properties of tamoxifen-derived DNA adducts, alpha-(N2-deoxyguanosinyl)tamoxifens (dG-N2-tamoxifen), have been explored, using an in vitro experimental system to quantify base substitutions and deletions. Site-specifically modified oligodeoxynucleotides containing an epimer of trans- and cis-forms of dG-N2-tamoxifens were prepared postsynthetically and used as templates in primer extension reactions catalyzed by mammalian DNA polymerases alpha, beta, and delta. Pol alpha catalyzed incorporation of dCMP and dAMP opposite all four stereoisomers of dG-N2-tamoxifen, accompanied by lesser amounts of dGMP. In contrast, pol delta catalyzed preferential incorporation of dCMP, a correct base, opposite the lesions; one of the trans-forms of dG-N2-tamoxifens only promoted incorporation of dTMP. Using pol beta, preferential incorporation of dCMP, along with small amounts of incorporation of dAMP and dGMP, was detected. One- and two base deletions were also observed with pol alpha and pol beta. The miscoding specificities and frequencies of dG-N2-tamoxifens varied depending on the DNA polymerase used. In addition, with pol alpha and pol beta, large amounts of 5-base deletions were preferentially formed at the cis-forms of dG-N2-tamoxifen, but not at the trans-forms of dG-N2-tamoxifen. We conclude that dG-N2-tamoxifen adducts have high miscoding potentials.
Shibutani
S
S
Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794-8651, USA. shinya@pharm.som.sunysb.edu
Dasaradhi
L
L
D000818:Animals; D001483:Base Sequence; D018736:DNA Adducts / Q000737:chemistry*; D004256:DNA Polymerase I / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism; D019951:DNA Polymerase beta / Q000378:metabolism; D017931:DNA Primers; D003838:Deoxyadenine Nucleotides / Q000378:metabolism; D003843:Deoxycytidine Monophosphate / Q000378:metabolism; D008322:Mammals; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000737:chemistry; D013698:Templates, Genetic
D018736:DNA Adducts; D017931:DNA Primers; D003838:Deoxyadenine Nucleotides; D009838:Oligodeoxyribonucleotides; C105083:alpha-(N(2)-deoxyguanosinyl)tamoxifen; D013629:Tamoxifen; D003843:Deoxycytidine Monophosphate; C012873:2'-deoxy-5'-adenosine monophosphate; D004256:DNA Polymerase I; D004258:DNA Polymerase III; D019951:DNA Polymerase beta