The proposal will address modes of action for tumor induction in liver by the food contaminant furan, which is formed by processing of food resulting in widespread human exposure. There is uncertainty regarding the relevance of tumors induced in rodents to human risk assessment because the mechanisms are unclear. The research will address the role of DNA and protein binding of furan, oxidative DNA damage, non-genotoxic alteration of proliferation and apoptosis, cytogenetics and cytotoxicity in furan-mediated liver toxicity and carcinogenicity. A combination of in vivo and in vitro systems, analytical chemistry, cell biology and “omics” technologies will be applied. In rodents in vivo, extent and dose-dependence of covalent binding to DNA, cytogenetic changes and geno- and cytotoxicity in target cells in the liver will be addressed after oral administration of furan. In addition, the induction of oxidative DNA-modifications and mechanisms of mutations will be investigated in genetically modified rodent models. These in vivo studies will characterize the mode of action of furan and also address irreversible metaplasia, changes in cell signaling and inflammation. The interaction of these effects with possible genetic changes in liver cells including aspects of forced cell proliferation will be included. The in vivo work will be complemented by studying mode of mutation of furan and its metabolite cis-2-butene-1,4-dial in cell culture models resembling the target cells. The content of furan in food will be determined and human exposures will be assessed using probabilistic modeling. Mechanisms of formation of furan in food may open ways to reduce exposures. The results will provide data on the mode-of-action of furan induced liver carcinogenesis as a basis for a conclusive assessment of health risks in humans due to dietary exposure. Combining these findings will provide a risk/benefit analysis and a scientific basis to justify limits for human furan exposures.