Epidemiological studies have linked aromatic amines (AAs) from tobacco smoke and some occupational exposures with bladder cancer risk. Several epidemiological studies have also reported a plausible role for structurally related heterocyclic aromatic amines present in tobacco smoke or formed in cooked meats with bladder cancer risk. DNA adduct formation is an initial biochemical event in bladder carcinogenesis. We examined paired fresh-frozen (FR) and formalin-fixed paraffin-embedded (FFPE) nontumor bladder tissues from 41 bladder cancer patients for DNA adducts of 4-aminobiphenyl (4-ABP), a bladder carcinogen present in tobacco smoke, and 2-amino-9H-pyrido[2,3-b]indole, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, possible human carcinogens, which occur in tobacco smoke and cooked meats. These chemicals are present in urine of tobacco smokers or omnivores. Targeted DNA adduct measurements were done by ultra-performance liquid chromatography-electrospray ionization multistage hybrid Orbitrap MS. N-(2′-Deoxyguanosin-8-yl)-4-ABP (N-(dG-C8)-4-ABP) was the sole adduct detected in FR and FFPE bladder tissues. Twelve subjects (29%) had N-(dG-C8)-4-ABP levels above the limit of quantification, ranging from 1.4 to 33.8 adducts per 10 9 nucleotides (nt). DNA adducts of other human AA bladder carcinogens, including 2-naphthylamine (2-NA), 2-methylaniline (2-MA), 2,6-dimethylaniline (2,6-DMA), and lipid peroxidation (LPO) adducts, were screened for in bladder tissue, by our untargeted data-independent adductomics method, termed wide-selected ion monitoring (wide-SIM)/MS 2 . Wide-SIM/MS 2 successfully detected N-(dG-C8)-4-ABP, N-(2′-deoxyadenosin-8-yl)-4-ABP and the presumed hydrazo linked adduct, N-(2′-deoxyguanosin-N 2 -yl)-4-ABP, and several LPO adducts in bladder DNA. Wide-SIM/MS 2 detected multiple DNA adducts of 2-NA, 2-MA, and, 2,6-DMA, when calf thymus DNA was modified with reactive intermediates of these carcinogens. However, these AA-adducts were below the limit of detection in unspiked human bladder DNA (<1 adduct per 10 8 nt). Wide-SIM/MS 2 can screen for many types of DNA adducts formed with exogenous and endogenous electrophiles and will be employed to identify DNA adducts of other chemicals that may contribute to the etiology of bladder cancer.
Bibliographical noteFunding Information:
This work is funded by R33CA186795 and R01CA220367 from the National Cancer Institute, R01ES019564 from the National Institute of Environmental Health Sciences, and the National Center for Advancing Translational Sciences of the National Institutes of Health award number UL1TR000114. Mass spectrometry was carried out in the Analytical Biochemistry Shared Resource of the Masonic Cancer Center, University of Minnesota, funded in part by Cancer Center Support grant CA-077598. Salary support for P.W.V. was provided by the National Cancer Institute of the National Institutes of Health under award number R50CA211256. Notes The authors declare no competing financial interest.
© 2018 American Chemical Society.