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 F₁ (BCF₁) or C3H/HeN×C57BL/6N F₁ (CBF₁) 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.