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Methyleugenol DNA adducts in human liver are associated with SULT1A1 copy number variations and expression levels


Methyleugenol is a rodent hepatocarcinogen occurring in many herbs and spices as well as essential oils used for flavoring. Following metabolic activation by cytochromes P450 (CYPs) and sulfotransferases (SULTs), methyleugenol can form DNA adducts. Previously, we showed that DNA adduct formation by methyleugenol in mouse liver is dependent on SULT1A1 expression and that methyleugenol DNA adducts are abundant in human liver specimens. In humans, SULT1A1 activity is affected by genetic polymorphisms, including single-nucleotide polymorphisms (SNPs) and copy number variations (CNVs). Here we investigated the relationship between individual methyleugenol DNA adduct levels and SULT1A1 in human liver samples. Using isotope-dilution ultraperformance liquid chromatography coupled with tandem mass spectrometry, we quantified methyleugenol DNA adducts in 121 human surgical liver samples. Frequent CNVs, including deletions (f = 3.3%) and duplications (f = 36.4%) of SULT1A1, were identified using qPCR and TaqMan assays in the donors’ genomic DNA. SULT1A1 mRNA and protein levels were quantified using microarray data and Western blot analysis, respectively. Methyleugenol DNA adducts were detected in all 121 liver samples studied. Their levels varied 122-fold between individuals and were significantly correlated to both mRNA and protein levels of SULT1A1 (r s = 0.43, and r s = 0.44, respectively). Univariate and multivariate statistical analysis identified significant associations of SULT1A1 CNVs with mRNA (p = 1.7 × 10−06) and protein (p = 4.4 × 10− 10) levels as well as methyleugenol DNA adduct levels (p = 0.003). These data establish the importance of SULT1A1 genotype for hepatic methyleugenol DNA adducts in humans, and they confirm a strong impact of SULT1A1 CNVs on SULT1A1 hepatic phenotype.

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The study was supported by the Robert Bosch Foundation, Stuttgart, Germany, and the German Federal Institute for Risk Assessment, Berlin, Germany (Grant FK-3-1329.421.1 + 2). R.T. was partially supported by a European Commission Horizon 2020 UPGx grant (668353). Britta Klumpp and Igor Liebermann are gratefully acknowledged for excellent technical assistance. We also thank Dr. Stefan Winter for expert advice concerning statistical analysis.

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Correspondence to Ulrich M. Zanger.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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R. Tremmel and K. Herrmann contributed equally to this study.

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Tremmel, R., Herrmann, K., Engst, W. et al. Methyleugenol DNA adducts in human liver are associated with SULT1A1 copy number variations and expression levels. Arch Toxicol 91, 3329–3339 (2017).

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  • Copy number variation
  • DNA adducts
  • Human liver
  • Methyleugenol
  • Pharmacogenetics/genomics
  • SULT1A1 expression