ACB‐PCR measurement of spontaneous and furan‐induced H‐ras Codon 61 CAA to CTA and CAA to AAA mutation in B6C3F1 mouse liver

Furan is a rodent liver carcinogen, but the mode of action for furan hepatocarcinogenicity is unclear. H‐ras codon 61 mutations have been detected in spontaneous liver tumors of B6C3F1 mice, and the fraction of liver tumors carrying H‐ras codon 61 CAA to AAA mutation increased in furan‐treated mice. Allele‐specific competitive blocker PCR (ACB‐PCR) has been used previously to quantify early, carcinogen‐induced increases in tumor‐associated mutations. The present pilot study investigated whether furan drives clonal expansion of pre‐existing H‐ras mutant cells in B6C3F1 mouse liver. H‐ras codon 61 CAA to CTA and CAA to AAA mutations were measured in DNA isolated from liver tissue of female mice treated with 0, 1, 2, 4, or 8 mg furan/kg body weight, five days per week for three weeks, using five mice per treatment group. Spontaneous levels of mutation were low, with two of five control mice having an H‐ras codon 61 CTA or AAA mutant fraction (MF) greater than 10^?5. Several furan‐treated mice had H‐ras codon 61 AAA or CTA MFs greater than those measured in control mice and lower bound estimates of induced MF were calculated. However, no statistically‐significant differences were observed between treatment groups. Therefore, while sustained exposure to furan is carcinogenic, at the early stage of carcinogenesis examined in this study (three weeks), there was not a significant expansion of H‐ras mutant cells. Environ. Mol. Mutagen. 54:659–667, 2013. © 2013 Wiley Periodicals, Inc.