Epidemiologic studies have reported an association between frequent consumption of well-done cooked meats and prostate cancer risk. However, unambiguous physiochemical markers of DNA damage from carcinogens derived from cooked meats, such as DNA adducts, have not been identified in human samples to support this paradigm. We have developed a highly sensitive nano-LC-Orbitrap MSn method to measure DNA adducts of several carcinogens originating from well-done cooked meats, tobacco smoke, and environmental pollution, including 2-amino-1- methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-9H-pyrido[2,3-b]- indole (AαC), 2-amino-3,8-dimethylimidazo[4,5-f ]quinoxaline (MeIQx), benzo[a]pyrene (B[a]P), and 4-aminobiphenyl (4-ABP). The limit of quantification (LOQ) of the major deoxyguanosine (dG) adducts of these carcinogens ranged between 1.3 and 2.2 adducts per 109 nucleotides per 2.5 μg of DNA assayed. The DNA adduct of PhIP, N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP) was identified in 11 out of 35 patients, at levels ranging from 2 to 120 adducts per 109 nucleotides. The dG-C8 adducts of AαC and MeIQx, and the B[a]P adduct, 10-(deoxyguanosin-N2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (dG-N2-B[a]PDE) were not detected in any specimen, whereas N-(deoxyguanosin-8-yl)-4-ABP (dG-C8-4-ABP) was identified in one subject (30 adducts per 109 nucleotides). PhIP-DNA adducts also were recovered quantitatively from formalin fixed paraffin embedded (FFPE) tissues, signifying FFPE tissues can serve as biospecimens for carcinogen DNA adduct biomarker research. Our biomarker data provide support to the epidemiological observations implicating PhIP, one of the most mass-abundant heterocyclic aromatic amines formed in well-done cooked meats, as a DNA-damaging agent that may contribute to the etiology of prostate cancer.
Bibliographical noteFunding Information:
We thank Dr. Badrinath Konety, MD, Department of Urology, University of Minnesota, for his interest and support of this project; Drew Sciacca, Department of Laboratory Medicine and Pathology, who handled the prostatectomy specimens and dissected appropriate tissue; and Beth Fenske and Carla Heinke, from BioNet Tissue Procurement, for collection of the prostate biospecimens. Dr. Frederick A. Beland from the National Center for Toxicology Research/U.S. FDA kindly provided PhIP, 4-ABP, and B[a]P-treated CT DNA. This work is supported by R01CA122320 (R.J.T.) and R33CA186795 (R.J.T.) from the National Cancer Institute of the National Institutes of Health. 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.