Discovery of Genotoxic Biomarkers in Urine for Cancer

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DESCRIPTION (provided by applicant): This project seeks to develop a new methological procedure that has the potential for improving the quality of cancer epidemiological research. The new procedure involves the use of mass spectrometry (MS) to analyze DNA adducts inherent to or derived from urine. The "inherent DNA adducts" will be analyzed for two purposes: (1) as potential biomarkers for human exposure to carcinogens, and (2) as potential biomarkers for the presence and tissue location of cancer. This latter hypothesis is suggested by bringing together the following observations by others: (1) each tissue has a unique pattern of lipophilic, apparently endogenous DNA adducts (as detected by 32P-post-labeling/HPLC); (2) some tissue DNA is spilled into the blood (increasingly so in cancer), and (3) some of the free DNA in the blood ends up in the urine. The "derived DNA adducts" will be obtained by following a published method in which genotoxic chemicals are extracted from smoker's urine and reacted in the presence of an S9 metabolic activation system with calf thymus DNA. Previous investigators have considered the genotoxic chemicals in smoker's urine to be the same as the mutagens, which are present. Detection in this project of the three types of DNA adducts (inherentexogenous, inherent-endogenous and derived) will be accomplished by using a method that we have recently developed in which the adducts, after isolation, are labeled with an imidazole substituted mass tag followed by use of matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS). Our new technique is very sensitive and measures the exact masses of a broad range of known and unknown DNA adducts simultaneously, unlike any prior analytical method for DNA adducts. Along with urine samples from control subjects and smokers, urine from patients with renal and bladder cancer will be tested. Urine is an attractive sample for epidemiological studies. The project initiates a collaboration between an analytical chemist and a molecular biologist.