Effect of promoter and intron 2 polymorphisms on murine lung K-ras gene expression. Carcinogenesis 1998 Aug;19(8):1503-8
Date
09/23/1998Pubmed ID
9744549DOI
10.1093/carcin/19.8.1503Scopus ID
2-s2.0-0031663096 (requires institutional sign-in at Scopus site) 16 CitationsAbstract
Differences in tumor formation among inbred mouse strains with high (A/J) and low (C3H) susceptibility for lung cancer have been linked to a repetitive element within the second intron of the K-ras gene. The purpose of this investigation was to determine whether differences within the K-ras gene promoter region or the intron 2 polymorphism affect K-ras gene expression in lung tumors and target alveolar type II cells isolated from A/J and C3H mice. Ribonuclease protection assays were performed using RNA isolated from 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumors from each mouse strain and alveolar type II cells isolated from A/J and C3H mice. An 838 bp fragment of the murine K-ras gene promoter region was amplified by PCR, cloned and sequenced from both mouse strains. Promoter regions from both mouse strains were inserted into a luciferase reporter gene vector, with and without the second intron polymorphism, and transfected into sensitive, intermediate and resistant lung tumor cell lines. No significant differences in K-ras gene promoter activity was found between the two strains using these specific reporter gene constructs. Consistent with these results, levels of K-ras expression did not differ between alveolar type II cells, whole lung or tumors induced by NNK in A/J or C3H mice. Moreover, in lung tumor cell lines derived from mice with differing susceptibility for lung cancer, K-ras expression did not correlate with the growth rate of tumors induced in nude mice from these cell lines. These results indicate that factors involved in modulating the rapid clonal expansion of the mutated K-ras allele from A/J mice are not directly linked to expression of this gene. Other genetic changes or losses in conjunction with hypothesized modifier loci, such as the Par1 locus, must play a significant role in establishing the phenotypic strain differences for lung tumor formation.
Author List
Jones-Bolin SE, Johansson E, Palmisano WA, Anderson MW, Wiest JS, Belinsky SAMESH terms used to index this publication - Major topics in bold
3T3 CellsAnimals
Base Sequence
Carcinogens
Gene Expression
Genes, Reporter
Genes, ras
Introns
Lung Neoplasms
Mice
Mice, Inbred A
Mice, Inbred C3H
Mice, Nude
Molecular Sequence Data
Nitrosamines
Polymorphism, Genetic
Promoter Regions, Genetic
Sp1 Transcription Factor
Species Specificity
ras Proteins
