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 gene tic alteration observed in a wide variety of human cancers, In this st udy we examined 63 methylcholanthrene (MCA)-induced sarcomas from C57B L/6NxC3H/HeN F-1 (BCF1) or C3H/HeNxC57BL/6N F-1 (CBF1) mice for p53 ge ne mutations and loss of heterozygosity (LOH) of chromosome 11, Mutati on analysis was done on exons 5 to 8 of the p53 gene by polymerase cha in reaction-single strand conformation polymorphism analysis, This ide ntified 53 potential mutations in 45 sarcomas, Mutations were further confirmed by direct sequencing of the region, Forty-nine of the 53 cas es (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 marker s of mouse chromosome 11 revealed LOH in ten cases (22%) among those c arrying p53 mutations, In nine of these 10 cases, the loss involved al l 5 markers, In addition, the loss was biased toward the C57BL allele (9 cases), The present study establishes the pattern of mutation of th e p53 gene in MCA-induced mouse sarcomas.