Mass spectrometry-based method development for metabolites and DNA adducts of bisphenol A in liver slices and human breast cancer cells

Bisphenol A (BPA) is a key industrial chemical used in the manufacture of polycarbonate plastics and other products. The estrogen-like endocrine-disrupting chemical may induce persistent epigenetic changes in the developing uterus. The BPA exposure in utero is also associated with an increased risk of breast cancer in women. However, the mechanism of increasing risk of cancer from the BPA exposure is not clear. A hypothesis that BPA may enhance breast cancer risk through metabolic reprogramming has been proposed. This proposal aims to utilize our strong experience in trace analysis with mass spectrometry for investigating in vitro metabolism of BPA for the potential formation of toxic components, with particular focus on whether the metabolites of BPA could be DNA-reactive. We postulate that BPA may be oxidized to phase I metabolite with a -diOH structure and transformed to BPA-quinones, which could form covalent adducts with DNA. To test this hypothesis, BPA metabolism in rat liver slices under different incubation conditions will be investigated. Metabolite identification will be performed by using liquid chromatography (LC) and gas chromatography (GC) coupled with mass spectrometry (MS). The established metabolic pathway will be confirmed and applied in the investigation of human breast cell (MCF- 7) with the comparisons to non-tumorigenic human breast cell (MCF-10A) as well as their controls. Major hydroxylated and oxidized metabolites will be isolated, purified and allowed to react with DNA for the investigation of possible formation of DNA adducts. High resolution mass spectrometry and tandem mass spectrometry as well as other analytical techniques will be applied for the characterization of DNA adducts. We believe that if DNA-adduct formation of BPA could be identified and confirmed, the outcome of this study would provide valuable information for further investigations on whether breast cancer could be attributed from DNA damage with the BPA exposure. The obtained results may also provide useful information for future investigation on BPA toxicities to animals and human.