Proto-oncogene activation in liver tumors of hepatocarcinogenesis-resistant strains of mice.

Abstract

Activation of the ras family of oncogenes occurs frequently in liver tumors of the B6C3F1 mouse, a strain which is highly sensitive to hepatocarcinogenesis. Many other mouse strains are much more resistant to hepatocarcinogenesis; the aim of this study was to determine the frequency and pattern of oncogene activation in spontaneous and chemically induced liver tumors of three such strains, the C57BL/6J, the C57BL/6 x DBA/2 F1 hybrid (B6D2F1) and the C57BL/6 x Balb/c F1 hybrid (B6BCF1). The C57BL/6, DBA/2 and Balb/c strains are all relatively resistant to spontaneous hepatocarcinogenesis (1.5-3.6% of animals develop liver tumors in 2 years); with regard to chemically induced hepatocarcinogenesis the Balb/c is highly resistant, the C57BL/6 has low susceptibility and the DBA/2 has low to moderate susceptibility. The nude mouse tumorigenicity assay was used to search for activated oncogenes in 15 C57BL/6J liver tumors induced by a single neonatal dose of vinyl carbamate (VC, 0.15 mumol/g body weight). Three tumors contained H-ras genes activated by point mutations at codon 61 and one contained a non-ras oncogene. The polymerase chain reaction and allele-specific oligonucleotide hybridization were used to study H-ras mutations in spontaneous and VC-induced tumors from all three strains of mice. The frequency of H-ras codon 61 mutations in tumors induced by 0.15 mumol/g body weight VC in the C57BL/6J mouse (5/37) was similar to that in spontaneous tumors (2/9); surprisingly, tumors induced by a lower dose of VC (0.03 mumol/g body weight) had a higher frequency of H-ras mutations (12/28). The frequencies of H-ras activation detected in VC (0.03 mumol/g body weight)-induced tumors from the two F1 hybrids studied differed markedly. Only one VC-induced B6BCF1 tumor contained a mutated H-ras gene (1/10), whereas the majority of B6D2F1 tumors contained such mutations (23/33). Several spontaneous B6D2F1 liver tumors contained H-ras codon 61 mutations (6/15). Thus, H-ras activation frequency does not determine susceptibility to hepatocarcinogenesis in inbred mice and their F1 hybrids, since a relatively high frequency of H-ras mutations was observed in two resistant strains and a low frequency was found in the other strain.

• Authors: L A Stanley, T R Devereux, J Foley, P G Lord, R R Maronpot, T C Orton, M W Anderson
• Journal: Carcinogenesis (Carcinogenesis) Vol. 13 Issue 12 Pg. 2427-33 (Dec 1992) ISSN: 0143-3334 [Print] England
• PMID: 1361883 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Codon
• DNA, Neoplasm

Topics

• 3T3 Cells
• Animals
• Base Sequence
• Blotting, Southern
• Codon
• DNA, Neoplasm
• Disease Susceptibility
• Gene Expression
• Genes, ras
• Liver Neoplasms, Experimental (genetics)
• Male
• Mice
• Mice, Inbred C57BL
• Mice, Nude
• Molecular Sequence Data
• Point Mutation
• Polymerase Chain Reaction
• Polymorphism, Restriction Fragment Length
• Transfection