Ligand Binding of Safrole to Cytochrome P-450

Safrole, a hepatocarcinogen, is converted by the microsomal mono-oxygenase system to a reactive intermediate which interacts with cytochrome P-450 to form a ligand complex. The formation of this complex is accompanied by loss of mono-oxygenase activity. The present study describes the interaction of the safrole reactive intermediate with microsomes from phenobarbital, 3-methylcholanthrene and safrole pretreated animals

Early microRNA and other non-coding RNA biomarkers for rodent non-genotoxic carcinogens

Several studies have revealed characteristic gene expression alterations after short-term treatment of rodents with non-genotoxic hepatocarcinogens. These may partly be regulated by epigenetic perturbations induced early after compound treatment. One goal of the IMI-MARCAR (bioMARkers and molecular tumour classification for non-genotoxic CARcinogenesis) consortium is to find early biomarkers for drug-induced rodent non-genotoxic carcinogenesis by using integrated molecular profiling including epigenetic parameters (mRNA, microRNA and other non-coding RNA and DNA methylation) of rodent liver in shorter term studies. MicroRNAs, as RNAs in general, are measurable with established methods and thus lend themselves as easily accessible biomarkers for both mechanistic and diagnostic investigations. A time course study with the well-characterized rodent liver tumour promoter phenobarbital in mice for total 13 weeks revealed progressive increases in hepatic expression of long non-coding RNAs and microRNAs originating from the Dlk1-Dio3 imprinted gene cluster, for which in vivo genetic dependence on constitutive androstane receptor and _-catenin could be shown with corresponding knock out and humanized mouse models. Altered expression from the Dlk1-Dio3 locus may be relevant for hepatocarcinogenicity based on recently observed associations with stem cell pluripotency in mice and various neoplasms in humans. Potential importance of this locus for rodent non-genotoxic hepatocarcinogenesis is being assessed by measuring microRNAs from this locus in mouse and rat liver after 2Ð4 weeks treatment with a selection of rodent non-genotoxic hepatocarcinogens. These studies will also include evaluations of other microRNAs suggested from 2-week rat studies and/or described in the literature as potential early biomarkers for cancer risk assessment