Mutagenesis of the K-ras protooncogene in mouse lung tumors induced by N-ethyl-N-nitrosourea or N-nitrosodiethylamine.
The role of ras gene activation in the development of lung tumors induced by N-ethyl-N-nitrosourea (ENU) and N-nitrosodiethylamine (DEN) was evaluated in the A/J mouse, a strain susceptible to chemically induced lung tumors. DNAs isolated from both ENU- and DEN-induced lung tumors were screened for activating mutations in the K-ras gene by utilizing the polymerase chain reaction (PCR) and direct sequence analysis. Mutations in the K-ras gene were detected in 11 of 11 ENU-induced tumors and 23 of 28 DEN-induced tumors. In ENU-induced tumors, there were three GC----AT transitions in the second base of codon 12, and seven AT----GC transitions and one AT----TA transversion in the second base of codon 61. A similar spectrum of K-ras mutations was observed in DEN-induced lung tumors: five GC----AT transitions and two GC----TA transversions in the second base of codon 12, and sixteen AT----GC transitions at the second base of codon 61. Ninety-one percent (31/34) of the observed mutations are consistent with the formation of the promutagenic O4-ethylthymine and O6-ethylguanine adducts in DNA. Therefore, lung tumors from the A/J mouse induced by DEN and ENU could be initiated by the interaction of reactive metabolites with specific sites in the K-ras gene. This is the first clear example of activation of the K-ras gene by ethylating agents in a rodent lung tumor system.
You
M
M
Department of Pathology, Medical College of Ohio, Toledo 43699.
Wang
Y
Y
Lineen
A M
AM
Gunning
W T
WT
Stoner
G D
GD
Anderson
M W
MW
D000818:Animals; D004052:Diethylnitrosamine / Q000633:toxicity*; D005038:Ethylnitrosourea / Q000633:toxicity*; D005260:Female; D011905:Genes, ras; D008175:Lung Neoplasms / Q000139:chemically induced / Q000235:genetics*; D008297:Male; D051379:Mice; D016296:Mutagenesis; D016133:Polymerase Chain Reaction; D011519:Proto-Oncogenes
D004052:Diethylnitrosamine; D005038:Ethylnitrosourea