Abstract A20: Dietary ingestion of aristolochic acid: Mechanisms of exposure

Abstract

Abstract Aristolochic acids (AA) are human carcinogens and nephrotoxins found in Aristolochia plants, including herbs used in traditional medicines throughout the world. Aristolochic acids can also be ingested as an environmental contaminant in food, which forms the basis of Balkan endemic nephropathy and associated upper tract urothelial cancer. Aristolactam DNA-adducts, formed after metabolism of AA, are promutagenic and are resistant to repair and readily detected in human tissue sample DNA decades after exposure. Thus, AL-DNA adducts are excellent biomarkers of exposure to this carcinogen. The mutational signature of AA is distinct for an environmental carcinogen and is recognized as Signature 22 in the COSMIC mutational signature database. Molecular epidemiology using the presence of adducts and/or the presence of Signature 22 has implicated AA in the etiology of several cancers, including upper-tract urothelial cancer, bladder cancer, renal cell clear cell carcinoma, hepatocellular carcinoma, and cholangiocarcinomas. In regions of the world reliant on traditional medicines, including much of Asia, the AA contribution to incidence of these cancers is significant. In the Balkan countries of Europe, the route of exposure is thought to occur via contamination of wheat harvests with Aristolochia plant material from weed growth. In endemic villages farming families traditionally have ingested primarily wheat flour milled from their own harvests. An alternative hypothesis is that decaying Aristolochia plants release the chemically stable aristolochic acids into the soil, and these are then taken up and concentrated by food plants. To distinguish between these hypotheses, we have obtained 25 flour samples from individual farms along the Croatia/Bosnia and Herzegovina border. To identify AA-contaminated flour, aristolochic acids were extracted from aliquots of the flour, reduced to aristolactams, and quantitated with an LC-ESI-MS/MS method. Several flour samples were indeed contaminated with AA in the range of 10–100 parts per billion. Secondly, we also extracted DNA from each flour sample. The direct contamination hypothesis predicts the presence of Aristolochia DNA in contaminated flour samples; the indirect contamination via decay hypothesis does not. Using widely accepted plant “barcode” PCR protocols, we amplified a portion of the rbcLa gene with generic primers that amplify the gene from all species. Within this PCR amplicon each plant species has a constellation of specific base-pairs. Thus, the contribution of all plant species to the flour sample can be determined by highly parallel sequencing of the amplicon. We will present the results of this next-gen sequencing to determine the contribution of Aristolochia to Balkan flour samples and correlation with aristolochic acid content. Citation Format: Viktoriya Sidorenko, Robert Rieger, Bojan Jelakovic, Thomas Rosenquist. Dietary ingestion of aristolochic acid: Mechanisms of exposure [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A20.