p53 Gene Mutation and Loss of Heterozygosity of Chromosome 11 in Methylcholanthrene‐induced Mouse Sarcomas

Mutations of the p53 tumor suppressor gene are the most prevalent genetic alteration observed in a wide variety of human cancers. In this study we examined 63 methylcholanthrene (MCA)‐induced sarcomas from C57BL/6N×C3H/HeN F(1) (BCF(1)) or C3H/HeN×C57BL/6N F(1) (CBF(1)) mice for p53 gene mutations and loss of heterozygosity (LOH) of chromosome 11. Mutation analysis was done on exons 5 to 8 of the p53 gene by polymerase chain reaction‐single strand conformation polymorphism analysis. This identified 53 potential mutations in 45 sarcomas. Mutations were further confirmed by direct sequencing of the region. Forty‐nine of the 53 cases (94%) were missense mutations, while the rest included two nonsense mutations, one silent mutation and one insertional mutation. Spectra of base substitutions were: 25 cases (47%) of G:C→T:A transversion, 13 cases (25%) of G:C→A:T transition (CpG site 15%), 13 cases (24%) of G:C→C:G transversion, a case (2%) of A:T→T:A transversion and a case (2%) of insertion. In addition, analysis of 5 polymorphic markers of mouse chromosome 11 revealed LOH in ten cases (22%) among those carrying p53 mutations. In nine of these 10 cases, the loss involved all 5 markers. In addition, the loss was biased toward the C57BL allele (9 cases). The present study establishes the pattern of mutation of the p53 gene in MCA‐induced mouse sarcomas.