Heterocyclic aromatic amines (HAAs) formed in tobacco smoke or cooked meat have been linked to human cancers. We studied the biotransformation of these carcinogens, and characterized DNA and protein adducts with low resolution mass spectrometry (MS), such as triple quadrupole (TQ) or ion trap (IT) MS. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is an abundant HAA formed in cooked meat. PhIP is a rodent prostate and possible human carcinogen. We have shown that TQ-MS can be employed to quantify PhIP in human hair and urine, and that IT multistage-MS (MSn) can measure DNA-PhIP adducts in animals and serum albumin (SA)-PhIP adducts ex vivo. However, our attempts to migrate such analytical methods to human samples were often unsuccessful because of the insufficient selectivity of the instruments. For example, the detection of PhIP in hair treated with permanent dye was impeded by isobaric interferences in the dye matrix. In response to these analytical challenges, we developed highly sensitive methods by coupling ultra-performance liquid chromatography to Orbitrap high-resolution (HR)-MSn. Hitherto, we have successfully measured PhIP in hair of healthy volunteers using hair dye and in patients with colorectal adenoma. Similarly, the low levels of adduct formation and the paucity of tissue limited our ability to measure adducts of carcinogens in humans by TQ- or IT-MS. We measured acid-labile SA-PhIP adducts in human volunteers administered a dietary-relevant dose of 14C-PhIP or a semi-controlled diet of well-done cooked meat. We identified DNA adducts of PhIP, but not other HAAs, in fresh-frozen prostatectomy samples and matching formalin-fixed tissues from prostate cancer patients, using HR-MSn. We are developing methods to screen for multiple exogenous and endogenous DNA adducts by untargeted MSn scanning. HR-MS instrumentation has greatly expanded our ability to measure biomarkers of dietary carcinogens, and can be employed to understand exposures and the etiological role of HAAs in human cancers.

Advances in human biomonitoring of heterocyclic aromatic amines by high resolution accurate mass spectrometry

254th National Meeting (2017)

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