| First Author | Malkinson AM | Year | 1993 |
| Journal | Mouse Genome | Volume | 91 |
| Issue | 1 | Pages | 130-32 |
| Mgi Jnum | J:4253 | Mgi Id | MGI:52749 |
| Citation | Malkinson AM, et al. (1993) Correlation of Kras-2 protooncogene structure with susceptibility to urethane-induced lung cancer in CXB recombinant inbred strains. Mouse Genome 91(1):130-32 |
| abstractText | Full text of Mouse Genome contribution: CORRELATION OF KRAS-2 PROTOONCOGENE STRUCTURE WITH SUSCEPTIBILITY TO URETHANE-INDUCED LUNG CANCER IN CXB RECOMBINANT INBRED STRAINS. Alvin M. Malkinson and Tobias D. Barker. Molecular Toxicology Program and Colorado Cancer Center, School of Pharmacy, University of Colorado, Box C238, 4200 East Ninth Avenue, Denver, CO 80262. A polymorphism in the structure of the Kras-2 protooncogene exists among mouse strains (1), due to the presence or absence of a sequence of 37 nucleotides which forms the second half of a tandem repeat in the second intron (2). A 5'-untranslated exon, exon 0, has been found in Kras-2 (3), so the first intron actually separates exons 0 and 1, and what was formerly considered to be the first intron is actually the second intron (2). The nature of the Kras-2 allele can be determined by restriction fragment length polymorphism (RFLP) analysis using either EcoRI (1) or KPNI (4) restriction endonucleases. Among 13 inbred and 36 recombinant inbred (RI) AXB, BXA strains tested, the nature of the polymorphism correlates with susceptibility to urethane-induced lung tumor development (1, 5). The presence of this stretch of base pairs renders mice resistant to tumor development. The range of tumor multiplicities among the susceptible strains that lack this region confirms the idea that more than one Pulmonary Adenoma Susceptibility or Pas gene (6) regulates lung tumor predisposition. Lung tumor multiplicity following urethane injection has been determined among the 7 CXB RI strains derived from the susceptible BALB/cByJ and resistant C57BL/6J progenitors (7, 8). The strain distribution pattern of susceptibility suggested linkage with Mup-1 on chromosome 4 (8). The Kras-2 polymorphism may possibly not contribute to susceptibility in these RI lines since the structural gene for Kras-2 maps to chromosome 6 (9). We herein examine the Kras-2 alleles in these strains. DNA was prepared from mice of each CXB RI strain and their progenitors, cleaved with KPNI, and a Southern blot was probed with a Kras cDNA probe as described (1) (Fig. 1). The G and K tumor- resistant strains had the same Kras allele as the resistant C57BL/6J progenitor, while the 4 strains which developed lung tumors displayed the allele of the susceptible BALB/cByJ progenitor (Table 1). CXB D mice contained both Kras alleles (Fig. 1), most likely because this strain has suffered genetic contamination (10). Figure 1. (Legend). RFLP in the Kras-2 protooncogene among the CXB RI strains using Southern analysis. Table l. (Legend). Comparison of the urethane induced lung tumor multiplicity and the size of the KPNI RFLP fragment derived from the Kras -2 protooncogene. Strain: Inbred Progenitors: BALB/cBy: Tumor No., a Mean +/- SEM: 1.80 +/- 0.30; Size of RFLP fragment (Kb): 22. C57BL/6By: Tumor No., a Mean +/- SEM: 0.58 +/- 0.24; Size of RFLP fragment (Kb): 9. Strain: RI strains: D: Tumor No., a Mean +/- SEM: 0.65 +/- 0.17; Size of RFLP fragment (Kb): 9 + 22. E: Tumor No., a Mean +/- SEM: 2.30 +/- 0.68; Size of RFLP fragment (Kb): 22. G: Tumor No., a Mean +/- SEM: 5.40 +/- 0.89; Size of RFLP fragment (Kb): 22. H: Tumor No., a Mean +/- SEM: 5.70 +/- 1.10; Size of RFLP fragment (Kb): 22. I: Tumor No., a Mean +/- SEM: 0.07 +/- 0.07; Size of RFLP fragment (Kb): 9. J: Tumor No., a Mean +/- SEM: 3.10 +/- 0.54; Size of RFLP fragment (Kb): 22. K: Tumor No., a Mean +/- SEM: 0.42 +/- 0.15; Size of RFLP fragment (Kb): 9. The CXB RI mice are similar to all other strains tested in that mice with a complete nucleotide sequence in the first intron of Kras-2 do not develop lung tumors. Since Kras -2 is often the transforming gene in these tumors (11), this suggests that the presence or absence of these bases regulates susceptibility to subsequent mutation at codons 12 (first exon) or 61 (second exon) in this gene. It is evident from Table 1 that more than one gene determines the number of tumors that will arise in an animal with the Kras-2 intronic deletion, since CXB G and CXB H mice have significantly higher tumor multiplicities than do strains CXB E and CXB J. The presence or absence of this 37bp stretch determines whether lung tumors develop, but other Pas genes influence the number of tumors that will appear in a strain that lacks this sequence. Among the RI series whose urethane-induced lung tumor multiplicities have been ascertained, tumor multiplicities intermediate to the progenitor phenotypes were described for AXB, BXA (6) and SWXL (5) mice. The apparent association of susceptibility with Mup-1 (8) illustrates the caution one should take in interpreting recombination data using only a few RI strains, as has been pointed out (12). Some correlation between human lung cancer susceptibility with variable tandem repeat polymorphisms of ras family genes has been observed (13). A gene near Mup-1 may be one of the Pas genes, and indeed a tumor suppressor gene on chromosome 4 which may regulate lung tumor susceptibility has been noted (14), but the Kras-2 gene is surely a major genetic determinant. Acknowledgements. We thank Drs. Vince Wilson and Qi Wei for technical advice. This work was supported by USPHS grant ES02370. References. (1) Ryan, J., Barker, P.E., Nesbitt, M.N. and Ruddle, F.H. (1987) J. Natl. Cancer Inst. 79: 1351-1357. (2) You, M., Wang, Y., Stoner, G., You, L,, Maronpot, R., Reynolds, S.H., and Anderson M. (1992) Proc. Natl. Acad. Sci. USA 89: 5804-5808. (3) Hoffman, E.K., Trosko, S.P., Freeman, N.A. and George, D.L. (1987) Mol. Cell Biol. 7: 2592-2596. (4) You, M., pers. commun. (5) Malkinson, A.M. Toxicology (1989) 54: 241-271. (6) Malkinson, A.M., Nesbitt, M.N. and Skamene, E. (1985) J. Natl. Cancer Inst. 75: 971-974. (7) Malkinson, A.M. and Beer, D.S. (1984) J. Natl. Cancer Inst. 73: 925-933. (8) Moriwaki, K. and Miyashita, N. (1989) Proc. Am. Assoc. Cancer Res. 30: 803. (9) Cahilly, L.A. and George, D.L. (1985) Cytogenet. Cell Genet. 39: 140-144. (10) Mobraaten, L.E., pers. commun. (11) You, M., Candrian, J., Maronpot, R.R., Stoner, G.D., and Anderson, M.W. (1989) Proc. Natl. Acad. Sci. USA 86: 3070-3074. (12) Silver, J. and Buckler, C.E. (1986) Proc. Natl. Acad. Sci. USA 83: 1423-1427. (13) Sugimura, H., Caporaso, N.E., Modali, R.V., Hoover, R.N., Resau, J.H., Trump, B.F., Lonergan, J.A., Krontiris, T.G., Mann, D.L., Weston, A., and Harris, C.C. (1990) Cancer Res. 50: 1857-1862. (14) Wiseman, R.W. and Barrett, J.C. (1990) Proc. Am. Assoc. Cancer Res. 31: 317. |
