New biomonitoring methodologies to measure DNA adducts in human tissues

University Of Minnesota, Minneapolis MN

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Abstract

DESCRIPTION (provided by applicant): The objective of this proposal is to develop new biomonitoring methodologies designed to measure DNA adducts in tissues of humans exposed to chemical carcinogens. Our chemical model for this project is structurally related nitro-phenanthrene carboxylic acids, a class of human carcinogens and nephrotoxicants that include aristolochic acids (AA). These compounds are universally present in herbs of the genus Aristolochia, used for medicinal purposes throughout the world for 2000 years. The nephrotoxicity and carcinogenicity of herbs containing AA are very well documented. Epidemiologic studies reveal AA to be the causal agent for the clinical syndromes known as Chinese herb and Balkan endemic nephropathies. In the latter, exposure to AA involves ingestion of bread prepared from flour contaminated with seeds of Aristolochia clematitis. Due to their toxicities, importation of traditional Chinese herbs containing AA are banned in some, but not all countries. Despite the Food and Drug Administration's warnings concerning the safety of botanical remedies containing AA, these herbs are still widely distributed in the United States via the Internet, and the incidence of chronic renal failure and urothelial cancer worldwide attributed to exposure to AA remains very high. Recently, we provided unequivocal evidence for the presence of AA-DNA adducts in the renal cortex of patients affected by BEN, using a novel, multi-stage ion trap mass spectrometry (MSn) method. Quantitative MS methods are essential for measuring DNA adduct biomarkers of this devastating and uniformally fatal disease. The biomonitoring methods will be used in translational research studies conducted in Balkan countries where the residents have dietary exposure to AA. A critical technological advance in DNA adduct screening methodologies will be achieved by extending the analysis of AA-DNA adducts from freshly frozen tissue samples to archived, formalin-fixed renal tissues, an untapped but rich source of material for toxico- logical research. Finally, a novel screening method will be established, employing an automated chip-based infusion nano-electrospray tandem MS method. This technique will provide a rapid throughput and cost- effective method to screen for DNA adducts in population-based studies. Traditional herbal remedies containing carcinogenic AA are used worldwide and are a global health problem. Recent epidemiological studies have linked herbs containing AA with renal failure and cancer. Rapid and quantitative analytical MS data to screen for AA-DNA adducts are needed to assess the exposure and the causal role of AA in nephropathy and upper urothelial cancer risk. The AA-DNA adducts also serve as critical biomarkers in studies of genetic susceptibility to Balkan endemic nephropathy and its associated upper urothelial cancer. The novel biomonitoring techniques established in this application can be appllied to examine the role of other chemical carcinogens in the etiology of human cancer.