title: Aristolochic acid-induced carcinogenesis examined by ACB-PCR quantification of H-Ras and K-Ras mutant fraction.
abstract: Aristolochic acid (AA) is a strong cytotoxic nephrotoxin and carcinogen associated with the development of urothelial cancer in humans. AA induces forestomach, kidney and urothelial tract tumours in rats and mice. This study was conducted to characterise AA's carcinogenic mechanism of action and compare allele-specific competitive blocker-polymerase chain reaction (ACB-PCR)-based early detection of carcinogenic effect using two different tumour-relevant endpoints. H-Ras codon 61 CAA→CTA mutation was analysed because it is found in rodent forestomach tumours and A:T→T:A transversion is the predominant mutational specificity induced by AA. K-Ras codon 12 GGT→GAT mutation was analysed because it is a common spontaneous mutation present in various rodent tissues and may be a useful generic biomarker for carcinogenic effect. DNA samples from Big Blue rats treated with 0, 0.1, 1.0 or 10.0 mg AA/kg body weight (bw) by gavage, 5 days/week for 12 weeks were used in ACB-PCR in order to examine the induction of the two specific mutations. A significant dose-dependent induction of H-Ras mutant fraction (MF) was observed in liver and kidney. Statistically significant correlations were observed between AA-induced DNA adduct levels or cII mutant frequencies (previously measured in the same rats) and H-Ras MF measurements. No correlation between AA dose and K-Ras MF was found in liver or kidney, although there was a significant induction of K-Ras mutation in kidneys exposed to 0.1 mg/kg bw AA relative to controls. Thus, the data establish a straightforward dose-related increase in H-Ras MF due to fixation of AA-induced DNA adducts, whereas the common spontaneous K-Ras mutation showed a non-monotonic dose-response, consistent with loss of non-targeted mutation at cytotoxic doses.
authors.affiliation: Division of Genetic and Molecular Toxicology, National Center for Toxicological Research, US Food and Drug Administration, HFT-120, 3900 NCTR Road, Jefferson, AR 72079, USA. yiying.wang@fda.hhs.gov
authors.forename: Yiying
authors.initials: Y
authors.lastname: Wang
authors.forename: Fanxue
authors.initials: F
authors.lastname: Meng
authors.forename: Volker M
authors.initials: VM
authors.lastname: Arlt
authors.forename: Nan
authors.initials: N
authors.lastname: Mei
authors.forename: Tao
authors.initials: T
authors.lastname: Chen
authors.forename: Barbara L
authors.initials: BL
authors.lastname: Parsons
mesh_terms: D000483:Alleles; D000818:Animals; D034341:Aristolochic Acids / Q000494:pharmacology / Q000633:toxicity*; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced* / Q000235:genetics*; D003062:Codon; D018736:DNA Adducts; D011905:Genes, ras; D008297:Male; D009154:Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D051381:Rats; D055647:Rats, Transgenic
chemical_list: D034341:Aristolochic Acids; D003062:Codon; D018736:DNA Adducts