Levels of Kras Codon 12 Mutations in Mouse Ovary Measured by ACB-PCR Were Not Increased by Transplacental Exposure to benzo[a]pyrene or Impacted by Gclm Genotype

Abstract No. Title Levels of Kras codon 12 mutations in mouse ovary measured by ACB-PCR were not increased by transplacental exposure to benzo[a]pyrene or impacted by Gclm genotype Abstract ACB-PCR, a sensitive DNA-based method for quantifying cancer-driver mutations, has been used to demonstrate: 1) relatively high levels of KRAS mutations are frequently present in normal rodent and human tissues, 2) human tumors frequently carry KRAS mutant subpopulations, thus KRAS mutation contributes to a greater fraction of human cancers than is recognized, and 3) increased levels of Kras mutation may occur following short-term exposure to carcinogens. KRAS is the fourth most frequently mutated gene in ovarian cancer, with two specific mutations accounting for 73% of those reported (G12D, 41%; G12V, 32%). This study investigated the utility of ACB-PCR in evaluating the transplacental mutagenesis of benzo[a]pyrene, in the presence and absence of Gclm-deficiency. Our prior study showed Gclm-/- mice have increased sensitivity to ovarian tumorigenesis induced by prenatal benzo[a]pyrene exposure. Gclm is the modifier subunit of glutamate cysteine ligase, which catalyzes the rate limiting step in glutathione biosynthesis. C57Bl/6J (Gclm heterozygous) dams were gavaged with 2 mg/kg/day benzo[a]pyrene or the sesame oil vehicle on gestational days 6.5-15.5. Ovaries of female offspring (Gclm+/ +, Gclm +/-, and Gclm-/-) were harvested at first vaginal estrus (postnatal day 34-46) and Kras codon 12 GAT and GTT mutations (G12D and G12V, respectively) were quantified. Measureable levels of Kras mutation were present in all ovarian DNA samples, with geometric mean mutant fractions (MFs) of 6.11 x 10 -5 and 1.07 x 10 -4 for G12D and G12V in Gclm+/+ vehicle control mice, respectively. No significant changes in Kras MF were observed due to benzo[a]pyrene-treatment, Gclm genotype, or their interaction. Sponsor First Name Malathi Sponsor Last Name Banda Sponsor Affiliation National Center for Toxicological Research Approval Confirm Presentation Poster only Categories Mutagenesis and Carcinogenesis 2nd choice Environmental Mutagenesis Student/New investigator New investigator Award application No Affiliations (1) National Center for Toxicological Research, US FDA, Jefferson, AR, United States (2) University of California,Irvine, Irvine, CA, United States Authors Barbara L. Parsons (1)