Benzo[a]pyrene-induced mutagenesis of p53 hot-spot codons 248 and 249 in human hepatocytes.
Human tobacco-related cancers show a high frequency of G-to-T transversions in several mutation hot-spot regions of the p53 tumor suppressor gene, probably the result of specific mutagens in tobacco smoke, most notably benzo[a]pyrene. To gain insight into the mechanism of formation of these G-to-T transversions in tobacco-associated carcinogenesis, we studied the mutagenesis of p53 codons 247-250 by benzo[a]pyrene in human hepatocellular carcinoma cells by restriction fragment length polymorphism-polymerase chain reaction genotypic analysis. Benzo[a]pyrene preferentially induced G-to-T transversion in the second and third positions of codon 248 and C-to-A transversion in the first position of codon 248. However, benzo[a]pyrene did not induce base-pair changes in codon 249, which is a mutational hot-spot in aflatoxin-related hepatocarcinogenesis, in which predominantly G-to-T transversion in the third position of codon 249 is observed. The benzo[a]pyrene-induced G-to-T transversion in the middle position of codon 248, in which arginine is changed into leucine, is frequently observed in tumors of the lung. The other two benzo[a]pyrene-induced base-pair changes in codon 248, namely the C-to-A transversion in the first position and G-to-T transversion in the third position, do not lead to a change in the amino-acid composition of the p53 protein. These mutations are silent and therefore are not selected in tumors. It follows that benzo[a]pyrene-induced mutability on the DNA level in p53 codons 247-250 correlates well with the type of mutation found in tumors of the lung. Therefore, our results support the hypothesis that benzo[a]pyrene is the etiological agent in tobacco-related cancers.
Cherpillod
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Department of Pathology, University of Maryland, Baltimore 21201-1192, USA.
Amstad
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D001482:Base Composition; D001483:Base Sequence; D001564:Benzo(a)pyrene / Q000493:pharmacokinetics / Q000633:toxicity*; D001711:Biotransformation; D006528:Carcinoma, Hepatocellular; D003062:Codon / Q000187:drug effects*; D005069:Evaluation Studies as Topic; D016158:Genes, p53 / Q000187:drug effects*; D005838:Genotype; D006801:Humans; D015151:Immunoblotting; D008099:Liver / Q000166:cytology* / Q000187:drug effects* / Q000502:physiology*; D008113:Liver Neoplasms; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D014407:Tumor Cells, Cultured
D003062:Codon; D001564:Benzo(a)pyrene