title: Incidence of Harvey ras oncogene point mutations and their expression in methylbenzylnitrosamine-induced esophageal tumorigenesis.
abstract: Activation of the ras oncogene was investigated in esophageal tumors induced by methylbenzylnitrosamine (MBN) in the Sprague-Dawley rat. DNA was extracted from grossly visible carcinogen-induced tumors. H-ras and K-ras gene sequences were then amplified by the polymerase chain reaction. Point mutations in the ras genes were then identified by selective hybridization to allele-specific oligonucleotide probes. A guanine to adenine transition at the 35th nucleotide in the H-ras coding sequence (GGA to GAA in the 12 codon) was observed in 67% (10 of 15) of the papillomas examined. This mutation codes for glutamate instead of glycine as the 12th amino acid of the ras p21 protein. No other H-ras or K-ras mutations were observed. To determine the distribution of this H-ras mutation in esophageal tissues, histological sections of MBN-treated esophagi were stained with a monoclonal antibody (E184) which selectively recognizes the mutated ras p-21 with glutamate substituted for glycine as the 12th amino acid. Expression of the mutant ras p21 protein was observed in 20% of the squamous papillomas, 13.6% of hyperplastic lesions and 10% of dysplastic lesions. Thus, activation of the H-ras oncogene as a result of guanine to adenine point mutation is a frequent event in esophageal tumors induced by MBN, occurring in 67% of squamous papillomas, but expression of the corresponding mutant ras p21 protein is observed in a much smaller proportion of the tumors in this animal model.
authors.affiliation: Department of Medicine, Northwestern University Medical School, Chicago, IL.
authors.forename: D H
authors.initials: DH
authors.lastname: Barch
authors.forename: R F
authors.initials: RF
authors.lastname: Jacoby
authors.forename: T A
authors.initials: TA
authors.lastname: Brasitus
authors.forename: J A
authors.initials: JA
authors.lastname: Radosevich
authors.forename: W P
authors.initials: WP
authors.lastname: Carney
authors.forename: P M
authors.initials: PM
authors.lastname: Iannaccone
mesh_terms: D000225:Adenine / Q000502:physiology; D000818:Animals; D001483:Base Sequence; D002273:Carcinogens; D003062:Codon / Q000235:genetics; D004128:Dimethylnitrosamine / Q000031:analogs & derivatives*; D004938:Esophageal Neoplasms / Q000139:chemically induced / Q000235:genetics*; D004947:Esophagus / Q000187:drug effects / Q000473:pathology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000235:genetics; D011905:Genes, ras / Q000187:drug effects / Q000235:genetics*; D006147:Guanine / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D015689:Oncogene Protein p21(ras) / Q000032:analysis / Q000235:genetics; D010212:Papilloma / Q000139:chemically induced / Q000235:genetics*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D002273:Carcinogens; D003062:Codon; D006147:Guanine; C014707:nitrosobenzylmethylamine; D015689:Oncogene Protein p21(ras); D000225:Adenine; D004128:Dimethylnitrosamine