Despite intensive research over the last two decades, there are still no specific markers of endogenous lipid hydroperoxide-mediated DNA damage. We recently demonstrated that heptanoneetheno-2-deoxyguanosine adducts are formed in the DNA of rat intestinal epithelial cells that stably express cyclooxygenase-2. Heptanone-etheno adducts can only arise from the reaction of lipid hydroperoxide-derived 4-oxo-2(E)-nonenal with DNA. This raised the possibility that similar adducts would be formed in

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... o in settings where cyclooxygenase-2 expression is increased. Therefore, DNA-adduct formation was studied in C57BL/6JAPC min mice, a colorectal cancer mouse model in which cyclooxygenase-2 is up-regulated. 15(S)-Hydroperoxy-5Z,8Z,11Z,13E-eicosatetraenoic acid is the major lipid hydroperoxide produced endogenously by cyclooxygenase-2. It undergoes homolytic decomposition to the DNA-reactive bifunctional electrophile 4-oxo-2(E)-nonenal, which forms heptanone-etheno adducts with DNA. A quantitative comparison was made of the heptanone-etheno-DNA adducts present in C57BL/6J and C57BL/6JAPC min mice. Using highly specific and sensitive methodology based on stable isotope dilution liquid chromatography/tandem mass spectrometry, we have detected the endogenous formation of heptanone-etheno adducts in mammalian tissue DNA for the first time. In addition, we found that there were statistically significant increased levels of the heptanoneetheno-2-deoxyguanosine and heptanone-etheno-2-deoxycytidine adducts in the C57BL/6JAPC min mice when compared with the control C57BL/6J mice. Colorectal cancer is the second leading cause of cancer-related deaths in the United States. Each year ϳ130,000 people are diagnosed with colorectal cancer, and ϳ56,000 will die from the disease. Multiple large epidemiological studies showed that regular use of NSAIDs 2 was associated with a reduction in the risk of cancer (1, 2). Furthermore, for individuals with inherited familial adenomatous polyposis, NSAID intake was associated with a reduction in polyp number and size (1, 3, 4).