Formation of depurinating N3Adenine and N7Guanine adducts by MCF-10F cells cultured in the presence of 4-hydroxyestradiol
✍ Scribed by Muhammad Saeed; Eleanor Rogan; Sandra V. Fernandez; Fathima Sheriff; Jose Russo; Ercole Cavalieri
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- French
- Weight
- 200 KB
- Volume
- 120
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
Abstract
Metabolic conversion of endogenous estrogens, estradiol (E~2~) and estrone (E~1~), to the catechol estrogens 4‐hydroxyE~1~(E~2~) [4‐OHE~1~(E~2~)] has been implicated in the initiation of cancer in rodents and humans. Evidence collected in our laboratories has shown that 4‐OHE~1~(E~2~) are enzymatically oxidized to E~1~(E~2~)‐3,4‐quinones [E~1~(E~2~)‐3,4‐Q], which have the potential to damage DNA by forming predominantly depurinating adducts, 4‐OHE~1~(E~2~)‐1‐N3Ade and 4‐OHE~1~(E~2~)‐1‐N7Gua, leading to the accumulation of mutations and probably cell transformation. The human breast epithelial cell line MCF‐10F has been transformed by treatment with E~2~ or 4‐OHE~2~. We have used MCF‐10F cells to study the presence of adducts and conjugates after treatment with 4‐OHE~2~. To mimic the intermittent exposure of breast cells to endogenous estrogens, MCF‐10F cells were treated with 1 μM 4‐OHE~2~ for a 24‐h period at 72, 120, 192 and 240 h postplating. Culture media were collected at each point, extracted by solid‐phase extraction and analyzed by HPLC connected with a multichannel electrochemical detector and/or ultraperformance liquid chromatography/tandem mass spectrometry. Media from successive treatments with 4‐OHE~2~ showed the formation of methoxy and cysteine conjugates, and the depurinating adducts 4‐OHE~1~(E~2~)‐1‐N3Ade. The amount of 4‐OHE~1~(E~2~)‐1‐N3Ade adducts was higher after the third treatment; smaller amounts of the 4‐OHE~1~(E~2~)‐1‐N7Gua adducts were detected after the second and third treatments. These results demonstrate that MCF‐10F cells oxidize 4‐OHE~2~ to E~1~(E~2~)‐3,4‐Q, which react with DNA to form the depurinating N3Ade and N7Gua adducts. This DNA damage can play an important role in the 4‐OHE~2~‐induced mutations and transformation of MCF‐10F cells to malignant cells. © 2007 Wiley‐Liss, Inc.