The pattern of p53 mutations caused by PAH o-quinones is driven by 8-oxo-dGuo formation while the spectrum of mutations is determined by biological selection for dominance.
PAHs (polycyclic aromatic hydrocarbons) are suspect lung cancer carcinogens that must be metabolically converted into DNA-reactive metabolites. P4501A1/P4501B1 plus epoxide hydrolase activate PAH to (+/-)- anti-benzo[ a]pyrene diol epoxide ((+/-)- anti-BPDE), which causes bulky DNA adducts. Alternatively, aldo-keto reductases (AKRs) convert intermediate PAH trans-dihydrodiols to o-quinones, which cause DNA damage by generating reactive oxygen species (ROS). In lung cancer, the types or pattern of mutations in p53 are predominantly G to T transversions. The locations of these mutations form a distinct spectrum characterized by single point mutations in a number of hotspots located in the DNA binding domain. One route to the G to T transversions is via oxidative DNA damage. An RP-HPLC-ECD assay was used to detect the formation of 8-oxo-dGuo in p53 cDNA exposed to representative quinones, BP-7,8-dione, BA-3,4-dione, and DMBA-3,4-dione under redox cycling conditions. Concurrently, a yeast reporter system was used to detect mutations in the same cDNA samples. Nanomolar concentrations of PAH o-quinones generated 8-oxo-dGuo (detected by HPLC-ECD) in a concentration dependent manner that correlated in a linear fashion with mutagenic frequency. By contrast, micromolar concentrations of (+/-)- anti-BPDE generated (+)- trans- anti-BPDE-N (2)-dGuo adducts (detected by stable-isotope dilution LC/MS methodology) in p53 cDNA that correlated in a linear fashion with mutagenic frequency, but no 8-oxo-dGuo was detected. Previous studies found that mutations observed with PAH o-quinones were predominately G to T transversions and those observed with (+/-)- anti-BPDE were predominately G to C transversions. However, mutations at guanine bases observed with either PAH-treatment occurred randomly throughout the DNA-binding domain of p53. Here, we find that when the mutants were screened for dominance, the dominant mutations clustered at or near hotspots primarily at the protein-DNA interface, whereas the recessive mutations are scattered throughout the DNA binding domain without resembling the spectra observed in cancer. These observations, if extended to mammalian cells, suggest that mutagenesis can drive the pattern of mutations but that biological selection for dominant mutations drives the spectrum of mutations observed in p53 in lung cancer.
Park
Jong-Heum
JH
Department of Pharmacology, Centers for Excellence in Environmental Toxicology and Cancer Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6084, USA.
Gelhaus
Stacy
S
Vedantam
Srilakshmi
S
Oliva
Andrea L
AL
Batra
Abhita
A
Blair
Ian A
IA
Troxel
Andrea B
AB
Field
Jeffrey
J
Penning
Trevor M
TM
D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA / Q000235:genetics; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D016296:Mutagenesis / Q000187:drug effects*; D009154:Mutation / Q000235:genetics*; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011809:Quinones / Q000737:chemistry* / Q000494:pharmacology*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D011084:Polycyclic Aromatic Hydrocarbons; D011809:Quinones; D016159:Tumor Suppressor Protein p53; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D003849:Deoxyguanosine