Identification of new markers of alcohol-derived dna damage in humans

Alcohol consumption is a risk factor for the development of several cancers, including those of the head and neck and the esophagus. The underlying mechanisms of alcohol-induced car-cinogenesis remain unclear; however, at these sites, alcohol-derived acetaldehyde seems to play a major role. By reacting with DNA, acetaldehyde generates covalent modifications (adducts) that can lead to mutations. Previous studies have shown a dose dependence between levels of a major acet-aldehyde-derived DNA adduct and alcohol exposure in oral-cell DNA. The goal of this study was to optimize a mass spectrometry (MS)-based DNA adductomic approach to screen for all acetalde-hyde-derived DNA adducts to more comprehensively characterize the genotoxic effects of acetal-dehyde in humans. A high-resolution/-accurate-mass data-dependent constant-neutral-loss-MS³ methodology was developed to profile acetaldehyde-DNA adducts in purified DNA. This resulted in the identification of 22 DNA adducts. In addition to the expected N²-ethyldeoxyguanosine (after NaBH3CN reduction), two previously unreported adducts showed prominent signals in the mass spectra. MSⁿ fragmentation spectra and accurate mass were used to hypothesize the structure of the two new adducts, which were then identified as N⁶-ethyldeoxyadenosine and N⁴-ethyldeoxycyti-dine by comparison with synthesized standards. These adducts were quantified in DNA isolated from oral cells collected from volunteers exposed to alcohol, revealing a significant increase after the exposure. In addition, 17 of the adducts identified in vitro were detected in these samples con-firming our ability to more comprehensively characterize the DNA damage deriving from alcohol exposures.