Related Experiment Videos
Miscoding potential of tamoxifen-derived DNA adducts: alpha-(N2-deoxyguanosinyl)tamoxifen
1Department of Pharmacological Sciences, State University of New York at Stony Brook, Stony Brook, New York 11794-8651, USA. shinya@pharm.som.sunysb.edu
Abstract:
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.
Insights
Tamoxifen treatment for breast cancer increases endometrial cancer risk due to DNA adducts. These tamoxifen-DNA adducts (dG-N2-tamoxifen) cause significant DNA miscoding, leading to mutations during replication.
Area of Science:
- Molecular Biology
- Cancer Research
- Toxicology
Background:
- Tamoxifen is a widely used breast cancer treatment.
- Tamoxifen use is linked to an increased risk of endometrial cancer.
- Tamoxifen-DNA adducts, specifically alpha-(N2-deoxyguanosinyl)tamoxifen (dG-N2-tamoxifen), are implicated in its carcinogenicity.
Purpose of the Study:
- To investigate the miscoding properties of tamoxifen-DNA adducts (dG-N2-tamoxifen).
- To quantify base substitutions and deletions induced by these adducts using various DNA polymerases.
- To understand how different DNA polymerases interact with tamoxifen-DNA adducts.
Main Methods:
- Preparation of site-specifically modified oligodeoxynucleotides containing epimers of dG-N2-tamoxifen.
- In vitro primer extension assays using mammalian DNA polymerases alpha, beta, and delta.
- Quantification of base incorporation (substitutions) and deletions opposite the modified guanine base.
Main Results:
- DNA polymerases alpha, beta, and delta exhibited varying miscoding specificities and frequencies when encountering dG-N2-tamoxifen adducts.
- DNA polymerase alpha incorporated incorrect bases (dCMP, dAMP) opposite all adduct forms.
- DNA polymerase delta preferentially incorporated the correct base (dCMP), but some adducts caused dTMP incorporation; deletions were also observed with polymerases alpha and beta.
Conclusions:
- Tamoxifen-derived DNA adducts (dG-N2-tamoxifen) possess high miscoding potentials.
- The specific DNA polymerase involved influences the type and frequency of mutations induced by these adducts.
- Understanding these miscoding properties is crucial for assessing tamoxifen's carcinogenic risk.