Multiple molecular alterations in mouse lung tumors

Abstract

Twenty-five mouse lung tumors induced by a single urethan treatment in female A/J, BALB/c, and (A/J x C3H/He)F1 (AC3) mice were analyzed for the presence of mutations at codon 61 of the Ki-ras gene and for the expression of the surfactant protein A (SP-A), retinoblastoma (Rb), growth arrest-specific-3 (gas-3), p53, c-myc, and thymidylate synthase (TS) genes. Ki-ras codon 61 mutations were detected in 22 of 25 tumor samples without differences among strains. In comparison with normal lungs, all the tumors showed increased SP-A mRNA levels, indicating their derivation from alveolar type II pneumocytes or Clara cells. Rb and gas-3 transcripts were instead found in all tumors at about tenfold and about 20-fold reduced levels, respectively. No apparent structural alterations or loss of heterozygosity at the Rb locus was detected in any tumors. The p53 mRNA was observed without variation in quantity or size in lung tumors and normal tissue. A threefold to fivefold c-myc overexpression was observed, without amplification of the gene. TS expression was only slightly increased, indicating no great differences in cell proliferation between lung tumors and normal tissue. Our data suggest that the pathogenesis of urethan-induced lung tumors in mice involves specific and recurrent molecular alterations (Ki-ras mutations, decrease of Rb and gas-3 expression, and increase of c-myc expression) that could represent different steps in lung carcinogenesis.

Roles of the Pas1 and Par2 genes in determination of the unique, intermediate susceptibility of BALB/cByJ mice to urethane-induction of lung carcinogenesis: Differential effects on tumor multiplicity, size and Kras2 mutations

“…In the vast majority of Kras2-activated mouse lung tumors induced by urethane or its metabolite, vinyl carbamate, the activation is speci®cally caused by an A to G transition or an A to T transversion at the second position of codon 61 (You et al, 1989(You et al, , 1992Re et al, 1992;Ohmori et al, 1992). Since these point mutations create a novel TaqI or XbaI restriction site, respectively (George et al, 1985), we analysed their allelic preference in lung tumors of (C3H6BALB)F 1 mice using a polymerase chain reaction (PCR)-based, nonisotopic restriction fragment length polymorphism (RFLP) method (Lee and Drinkwater, 1995a).…”

“…The BALB and A/J allele of Kras2 has a ScaI site in intron 3, but the C3H allele does not tumors, taken from di erent BALB Kras2-positive backcross mice, contained the TaqI or XbaI RFLP, in contrast to none of 17 tumors from the negative mice. A very small percentage of urethane-induced mouse lung tumors were reported to carry an A to T or an A to C conversion at the third position of Kras2 codon 61 (Re et al, 1992;Ohmori et al, 1992). Since these point mutations create a novel RcaI or MaeIII restriction site, respectively, we also analysed the tumor-derived PCR products for RcaI and MaeIII RFLPs.…”

“…Most mouse lung tumors induced by urethane have been reported to possess Kras2 oncogenes activated by A to T or G conversions at the second position of codon 61 (You et al, 1989(You et al, , 1992Re et al, 1992;Ohmori et al, 1992). Since such conversions create XbaI or TaqI restriction sites, respectively (George et al, 1985), we non-isotopically tested for activating point mutations utilizing the restric-tion length polymorphism (Lee and Drinkwater, 1995a and KrasR2 (5'-TTAAACCCACCTATAATGG-3') ( Figure 4), with lung tumor DNA as the template.…”

“…A very small percentage of urethane-induced mouse lung tumors were reported to carry an A to T or an A to C conversion at the third position of Kras2 codon 61 (Re et al, 1992;Ohmori et al, 1992). Since these point mutations create a novel RcaI or MaeIII restriction site, respectively (George et al, 1985), the PCR products were also analysed for RcaI and MaeIII RFLPs in some cases.…”

Differential expression of cyclin G2, cyclin-dependent kinase inhibitor 2C and peripheral myelin protein 22 genes during adipogenesis

“…Moreover, the high expression of PMP22 in the lung of the human, mouse and pig may also be important for normal function in the quiescent state of lung cells, because expression of PMP22 was reported to be down-regulated in lung tumors of mice (Re et al, 1992). Finally, the high mRNA expression and low protein expression of CCNG2 in lung and intestine may indicate that some post-transcriptional mechanisms are involved in the regulation of this gene and that CCNG2 may not be the major regulator of cell cycle inhibition in these tissues.…”