Abstract:
DNA mismatch repair (MMR) plays an important role in preserving genomic stability
and reducing cancer risk. Environmental exposures to polycyclic aromatic hydrocarbons
(PAHs) are believed to contribute significantly to carcinogenesis. PAHs are found in
food, air, water and soil and upon bioactivation can form diol epoxides which are
electrophilic in nature and can adduct to DNA, creating bulky PAH-DNA lesions.
Preliminary data in the Buermeyer laboratory demonstrated that mutations induced by
benzo[a]pyrene diol epoxide (BPDE) occur at higher rates in MLH1-deficient HCT
116+Ch2 cell line (30±7 mutations per 100 nM BPDE) versus a genetically matched
MLH1-proficient line HCT 116+Ch3 cell line (10±4 mutations per 100 nM BPDE). I
hypothesized that the role for MMR in suppressing mutation is a phenomenon
generalizable to other cell lines. I measured BPDE-induced mutation rates in the parent
cell line HCT 116, and in another genetically matched MSH6-proficient and -deficient
set. I found an induced mutation rate of 30±5 mutations per 100 nM BPDE using HCT
116 cells, not significantly different from the induced mutation rate with HCT 116+Ch2
cells. In addition, we characterized mutants from HCT 116+Ch2 clones and identified 25
individual mutations with the predominance of G→T transversions.
