title: Dose-related changes in the profile of ras mutations in chemically induced CD-1 mouse liver tumors.
abstract: We investigated the role of dosing regimen on ras mutations in chemically induced CD-1 mouse liver tumors. The spectra of ras gene mutations in liver tumors that were induced by 15 daily i.p. injections of 7,12-dimethylbenz[a]anthracene (DMBA), 4-aminoazobenzene (AAB), N-hydroxy-2-acetylaminofluorene (N-OH-AAF) or N-nitrosodiethylamine (DEN) were compared to those previously obtained for tumors induced by a single but higher dose of each carcinogen. The principal assay used was a direct tumor analysis involving sequencing of polymerase chain reaction (PCR)-amplified tumor DNA; additional mutations that were present in only a small fraction of tumor cells were detected using a transfection assay or a PCR-engineered restriction fragment length polymorphism method. Spontaneous liver tumors had a relatively low frequency of ras mutations, all found in Ha-ras codon 61, and most of these mutations were present in only a small fraction of tumor cells. With the exception of multiple-dose DEN, each group of single- and multiple-dose carcinogen-induced tumors exhibited a higher frequency of ras mutations compared with spontaneous tumors. For AAB, N-OH-AAF and DEN, the dosing regimen was found to affect significantly the profile of ras mutations. For each of these carcinogens, the multiple-dose tumor group (versus single-dose group) had fewer Ki-ras and N-ras mutations and more tumors in which the Ha-ras codon 61 (C-->A) mutation was present in a large fraction of cells. Our results demonstrate that the dosing procedure can materially affect the pattern of ras gene mutation in mouse liver tumors.
authors.affiliation: Department of Safety Assessment, Merck Research Laboratories, West Point, PA 19486, USA.
authors.forename: S
authors.initials: S
authors.lastname: Manam
authors.forename: G A
authors.initials: GA
authors.lastname: Shinder
authors.forename: D J
authors.initials: DJ
authors.lastname: Joslyn
authors.forename: A R
authors.initials: AR
authors.lastname: Kraynak
authors.forename: C L
authors.initials: CL
authors.lastname: Hammermeister
authors.forename: K R
authors.initials: KR
authors.lastname: Leander
authors.forename: B J
authors.initials: BJ
authors.lastname: Ledwith
authors.forename: S
authors.initials: S
authors.lastname: Prahalada
authors.forename: M J
authors.initials: MJ
authors.lastname: van Zwieten
authors.forename: W W
authors.initials: WW
authors.lastname: Nichols
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000633:toxicity; D000483:Alleles; D000818:Animals; D002273:Carcinogens / Q000633:toxicity*; D003062:Codon; D004273:DNA, Neoplasm / Q000032:analysis; D004052:Diethylnitrosamine / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D011905:Genes, ras / Q000187:drug effects*; D006881:Hydroxyacetylaminofluorene / Q000633:toxicity; D008113:Liver Neoplasms / Q000139:chemically induced* / Q000235:genetics* / Q000473:pathology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D010128:p-Aminoazobenzene / Q000633:toxicity
chemical_list: D002273:Carcinogens; D003062:Codon; D004273:DNA, Neoplasm; D004052:Diethylnitrosamine; D006881:Hydroxyacetylaminofluorene; D015127:9,10-Dimethyl-1,2-benzanthracene; D010128:p-Aminoazobenzene