Abstract
We have mapped sites of tamoxifen adduct formation, in the loci gene using the polymerase STOP assay, following reaction in vitro with alpha-acetoxytamoxifen and horseradish peroxidase (HRP)/ H2O2 activated 4-hydroxytamoxifen For both compounds, most adduct formation occurred on guanines. However, one adenine, within a run of guanines, generated a strong polymerase STOP site with activated 4-hydroxytamoxifen, and a weaker STOP site with alpha-acetoxytamoxifen at the same location. In Escherichia coil the lac I gene reacted with 4-hydroxytamoxifen was more likely to be mutated (2 orders of magnitude) than when reacted with alpha-acetoxytamoxifen, despite the greater DNA adduct formation by a-acetoxytamoxifen. This correlates with the greater predicted ability of activated 4-hydroxytamoxifen adducts to disrupt DNA structure than alpha-acetoxytamoxifen adducts. For lac I reacted with activated 4-hydroxytamoxifen, a hot spot of base mutation was located in the region of the only adenosine adduct. No mutational hot spots were observed with alpha-acetoxytamoxifen, Our data clearly shows a lack of correlation between gross adduct number, as assayed by P-32-postlabeling and mutagenic potential. These data indicate the importance of minor adduct formation in mutagenic potential and further that conclusions regarding the mutagenicity of a chemical may not be reliably derived from the gross determination of adduct formation.
Original language | English |
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Pages (from-to) | 10989-10996 |
Number of pages | 8 |
Journal | Biochemistry |
Volume | 38 |
Issue number | 34 |
DOIs | |
Publication status | Published - 24 Aug 1999 |
Keywords
- ALPHA-HYDROXYTAMOXIFEN
- IN-VITRO
- METABOLIC-ACTIVATION
- TRANSGENIC RATS
- BREAST-CANCER
- LIVER
- IDENTIFICATION
- REPLICATION
- HEPATOCYTES
- 4-HYDROXYTAMOXIFEN
- alpha-hydroxytamofixen
- in-vitro
- metabolic-activation
- transgenic rats
- breast-cancer
- liver
- identification
- replication
- hepatocytes
- 4-hydroxytamoxifen