Detection of activated proto-oncogenes in N-nitrosodiethylamine-induced liver tumors: a comparison between B6C3F1 mice and Fischer 344 rats.
DNA from B6C3F1 mouse and Fischer 344 rat liver tumors induced by N-nitrosodiethylamine (DEN) were examined for the ability to induce morphological transformation of NIH3T3 cells. DNAs from 14 of 33 of the mouse liver tumors induced by a single injection of DEN at 12 or 15 days of age were positive in this assay while DNA from only one of 28 DEN-induced rat liver tumors was active. Southern blot analysis of the NIH3T3 transformants derived from the mouse liver tumors revealed amplified and/or rearranged restriction fragments homologous to the H-ras proto-oncogene. DNA from two independent foci induced by the rat tumor DNA did not hybridize to probes for members of the ras gene family or c-raf. Activating mutations in the H-ras genes from the DEN-induced mouse liver tumors were characterized by selective oligonucleotide hybridization and the detection of a new XbaI restriction site by Southern blot analysis. In activated H-ras genes from the DEN-induced mouse liver tumor DNA, seven of 14 had a CG----AT transversion at the first base of the 61st codon, three of 14 had an AT----GC transition and four of 14 had the AT----TA transversion at the second base of codon 61. This spectrum of mutations is very similar to that recently observed in activated H-ras genes found in spontaneously occurring B6C3F1 mouse liver tumors. Taken together, the data suggest that the DEN-induced rat and mouse liver carcinogenesis may involve genetic targets other than or in addition to the H-ras gene.
Stowers
S J
SJ
National Institute of Environmental Health Sciences, Laboratory of Biochemical Risk Analysis, Research Triangle Park, NC 27709.
Wiseman
R W
RW
Ward
J M
JM
Miller
E C
EC
Miller
J A
JA
Anderson
M W
MW
Eva
A
A
D000818:Animals; D002471:Cell Transformation, Neoplastic; D003062:Codon; D004262:DNA Restriction Enzymes; D004273:DNA, Neoplasm / Q000235:genetics*; D004052:Diethylnitrosamine; D008114:Liver Neoplasms, Experimental / Q000139:chemically induced / Q000235:genetics*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009154:Mutation; D009693:Nucleic Acid Hybridization; D011519:Proto-Oncogenes; D051381:Rats; D011916:Rats, Inbred F344; D014162:Transfection
D003062:Codon; D004273:DNA, Neoplasm; D004052:Diethylnitrosamine; D004262:DNA Restriction Enzymes