Biomonitoring DNA Adducts of Cooked Meat Carcinogens in Human Prostate by Nano Liquid Chromatography-High Resolution Tandem Mass Spectrometry: Identification of 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine DNA Adduct

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-methy1-6-phenylimidazo [4,5-b]pyridine (PhIP), 2-amino-9H-pyrido [2,3-b]-indole (AaC), 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 10(9) nucleotides per 2.5 mu g 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 10(9) nucleotides. The dG-C8 adducts of AaC and MeIQx, and the B[a]P adduct, 10-(deoxyguanosin-N-2-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a] pyrene (dG-N-2-B [a] PDE) were not detected in any specimen, whereas N-(deoxyguanosin-8-y1)-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.