title: Bracken fern-induced malignant tumors in rats: absence of mutations in p53, H-ras and K-ras and no microsatellite instability.
abstract: Bracken fern (genus Pteridium) has been shown to induce tumors in domestic and experimental animals. Epidemiological studies have also shown an association between human exposure to bracken toxins and increased risk for the development of upper gastrointestinal tract tumors. Our aim in this study was to investigate possible genomic alterations in bracken fern-induced tumors of experimental animals searching for molecular markers that might be used for human epidemiological studies. Using human colorectal carcinogenesis as a molecular model, we examined eight malignant bracken fern-induced tumors of rats for mutations in the genes associated with the "classic pathway" of colorectal cancer, i.e. p53 and ras, and also in the "mutator pathway" by evaluating microsatellite instability. Exons 5-9 of the p53 gene and exons 1 and 2 of the K-ras and H-ras genes were examined by DNA sequencing and no mutations were found in any of the eight tumors. Amplification of five previously validated microsatellite loci (one with mono-, three with di- and one with tetra-nucleotide repeat motifs) in the malignant tumors and in the surrounding normal tissue did not reveal any instability. The involvement of epigenetic alterations or of mutations in other tumor suppressor genes or oncogenes should be further investigated in the search for human epidemiological markers.
authors.affiliation: Departamento de Nutrição Clínica e Social, ENUT/UFOP, Morro do Cruzeiro, MG 35400-000, Ouro Preto, Brazil.
authors.forename: Renata N
authors.initials: RN
authors.lastname: Freitas
authors.forename: Geraldo
authors.initials: G
authors.lastname: Brasileiro-Filho
authors.forename: Marcelo E
authors.initials: ME
authors.lastname: Silva
authors.forename: Sérgio D J
authors.initials: SD
authors.lastname: Pena
mesh_terms: D000818:Animals; D002273:Carcinogens / Q000009:adverse effects*; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism; D016147:Genes, Tumor Suppressor / Q000502:physiology; D016158:Genes, p53 / Q000235:genetics*; D011905:Genes, ras / Q000235:genetics*; D018895:Microsatellite Repeats / Q000235:genetics*; D009154:Mutation; D010936:Plant Extracts / Q000009:adverse effects*; D016133:Polymerase Chain Reaction; D051381:Rats; D017208:Rats, Wistar; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism
chemical_list: D002273:Carcinogens; D017931:DNA Primers; D004273:DNA, Neoplasm; D010936:Plant Extracts