title: Chemical-specific alterations in ras, p53, and beta-catenin genes in hemangiosarcomas from B6C3F1 mice exposed to o-nitrotoluene or riddelliine for 2 years.
abstract: The most prominent neoplastic lesions in mice in the 2-year studies of o-nitrotoluene and riddelliine were hemangiosarcomas. Fifteen o-nitrotoluene-induced hemangiosarcomas of the skeletal muscle, subcutaneous tissue, and mesentery; 12 riddelliine-induced hemangiosarcomas of the liver; and 15 spontaneous subcutaneous hemangiosarcomas were examined for genetic alterations in ras, p53, and beta-catenin genes. Mutations in at least one of these genes were identified in 13 of 15 (87%) of the o-nitrotoluene-induced hemangiosarcomas with missense mutations in p53 exons 5-8 detected in 11 of 15 (73%) of these neoplasms. Seven of 15 (47%) hemangiosarcomas from mice exposed to o-nitrotoluene had deletions at exon 2 splice sites or smaller deletions in the beta-catenin gene. K-ras mutation was detected in only 1 of the 15 (7%) o-nitrotoluene-induced hemangiosarcomas. In contrast to the o-nitrotoluene study, 7/12 (58%) riddelliine-induced hemangiosarcomas had K-ras codon 12 GTT mutations and, when screened by immunohistochemistry, 9/12 (75%) had strong staining for the p53 protein in malignant endothelial cells, the cells of origin of hemangiosarcomas. Riddelliine-induced hemangiosarcomas were negative for the beta-catenin protein. Spontaneous hemangiosarcomas from control mice lacked both p53 and beta-catenin protein expression and ras mutations. Our data indicated that p53 and beta-catenin mutations in the o-nitrotoluene-induced hemangiosarcomas and K-ras mutations and p53 protein expression in riddelliine-induced hemangiosarcomas most likely occurred as a result of the genotoxic effects of these chemicals. It also suggests that these mutations play a role in the pathogenesis of the respective hemangiosarcomas in B6C3F1(1) mice.
mesh_terms: D000818:Animals; D003598:Cytoskeletal Proteins / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D016158:Genes, p53 / Q000187:drug effects*; D011905:Genes, ras / Q000187:drug effects*; D006394:Hemangiosarcoma / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D019042:Muscle Neoplasms / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D016133:Polymerase Chain Reaction; D011763:Pyrrolizidine Alkaloids / Q000633:toxicity*; D017422:Sequence Analysis, DNA; D014050:Toluene / Q000031:analogs & derivatives* / Q000633:toxicity*; D015534:Trans-Activators / Q000235:genetics*; D051176:beta Catenin
chemical_list: C495267:CTNNB1 protein, mouse; D003598:Cytoskeletal Proteins; D004273:DNA, Neoplasm; D011763:Pyrrolizidine Alkaloids; D015534:Trans-Activators; D051176:beta Catenin; C013672:riddelliine; D014050:Toluene; C029955:2-nitrotoluene