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  • 1
    ISSN: 1573-7225
    Keywords: Angiosarcoma of the liver ; chemical carcinogenesis ; p21 protein ; ras gene ; serum biomarker ; vinyl chloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Mutations inras oncogenes and expression of their encoded p21 protein products are believed to play an important role in carcinogenesis in humans. Detection of mutant p21 proteins in serum may be a useful molecular epidemiologic biomarker with which to study this process, and workers with heavy exposure to vinyl chloride (VC) represent a model population for such study. We studied the occurrence of a specificras mutation (Asp 13 c-Ki-ras) by oligonucleotide hybridization and the expression of the corresponding p21 protein in tumor tissue and serum by immunohistochemistry and immunoblotting with monoclonal antibodies in five individuals with heavy exposure to VC and resultant angiosarcomas of the liver (ASL). Four of five (80 percent) of the cases of ASL were found to contain the mutation and to express the corresponding mutant protein in their tumor tissue and serum. Serum expression of the mutant protein also was examined in nine VC-exposed workers with liver angiomas and 45 VC-exposed workers with no evidence of liver neoplasia; eight of nine (89 percent) of the former and 22 of 45 (49 percent) of the latter were also positive for the mutant p21 in their serum. However, serum immunoblotting results for 28 age-gender-race matched, unexposed controls were all negative. Stratification by years of VC exposure showed a significant linear trend (P〈10−5) for the occurrence of the serum mutant p21 protein with increasing duration of exposure. These results suggest that detection of serum mutant p21 protein can be a valid surrogate forras gene expression at the tissue level. Further, serum mutant p21 may be a useful molecular epidemiologic biomarker for the study of chemical carcinogenesis in humans exposed to VC and possibly for the study of other mutantras-related human cancers.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-4943
    Keywords: p53 ; mutation ; vinyl chloride ; molecular dynamics ; immunohistochemistry ; angiosarcoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The tumor suppressor gene p53 has been identified as the most frequent target of genetic alterations in human cancers. Vinyl chloride, a known human carcinogen that induces the rare sentinel neoplasm angiosarcoma of the liver, has been associated with specific A → T transversions at the first base of codons 249 and 255 of the p53 gene. These mutations result in an Arg→Trp amino acid substitution at residue 249 and an Ile→Phe amino acid substitution at residue 255 in a highly conserved region in the DNA-binding core domain of the p53 protein. To determine the effects of these substitutions on the three-dimensional structure of the p53 protein, we have performed molecular dynamics calculations on this core domain of the wild-type and the Trp-249 and Phe-255 mutants to compute the average structures of each of the three forms. Comparisons of the computed average structures show that both mutants differ substantially from the wild-type structure in certain common, discrete regions. One of these regions (residues 204–217) contains the epitope for the monoclonal antibody PAb240, which is concealed in the wild-type structure but accessible in both mutant structures. In order to confirm this conformational shift, tumor tissue and serum from vinyl chloride-exposed individuals with angiosarcomas of the liver were examined by immunohistochemistry and enzyme-linked immunosorbent assay. Individuals with tumors that contained the p53 mutations were found to have detectable mutant p53 protein in their tumor tissue and serum, whereas individuals with tumors without mutations and normal controls did not.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4943
    Keywords: p53 ; mutation ; vinyl chloride ; molecular dynamics ; immunohistochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The tumor suppressor gene p53 has been identified as the most frequent site of genetic alterations in human cancers. Vinyl chloride, a known human carcinogen, has been associated with specific A → T transversions at codons 179, 249, and 255 of the p53 gene. The mutations result in amino acid substitutions of His → Leu at residue 179, Arg → Trp at residue 249, and Ile → Phe at residue 255 in highly conserved regions of the DNA-binding core domain of the p53 protein. We previously used molecular dynamics calculations to demonstrate that the latter two mutants contain certain common regions that differ substantially in conformation from the wild-type structure. In order to determine whether these conformational changes are consistent for other p53 mutants, we have now used molecular dynamics to determine the structure of the DNA-binding core domain of the Leu 179 p53 mutant. The results indicate that the Leu 179 mutant differs substantially from the wild-type structure in certain discrete regions that are similar to those noted previously in the other p53 mutants. One of these regions (residues 204–217) contains the epitope for the monoclonal antibody PAb240, which is concealed in the wild-type structure, but accessible in the mutant structure, and another region (residues 94–110) contains the epitope for the monoclonal antibody PAb1620, which is accessible in the wild-type structure, but concealed in the mutant structure. Immunologic analyses of tumor tissue known to contain this mutation confirmed these predicted conformational shifts in the mutant p53 protein.
    Type of Medium: Electronic Resource
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