GERMLINE P53 MUTATION AT CODON-133 IN A CANCER-PRONE FAMILY

We identified four families in which we suspected the presence of gene tic factors predisposing them to cancer. We examined one family with f eatures suggesting Li-Fraumeni syndrome for the presence of a germline p53 mutation in 13 of its members. To detect germline p53 mutations w e performed polymerase chain reaction/nonradioisotopic single-strand c onformation polymorphism and DNA sequencing analysis on exons 4-9 of t he p53 gene. Mutated polymerase chain reaction-restriction fragment le ngth polymorphism analysis was also performed on exon 5 to confirm the mutation identified by the sequencing analysis. A novel germline p53 mutation was identified at codon 133 (ATG-->AGG) in exon 5, resulting in the substitution of arginine for methionine, in all four cancer-aff ected individuals and in three apparently healthy individuals. We also analyzed tumor specimens for additional p53 mutations in the wild-typ e alleles using the same methods. However, heterozygosity was retained , and no other additional mutations in the wild-type allele were ident ified in any of the tumor tissues. It is possible that additional muta tions in the wild-type allele are not always necessary for the loss of tumor suppressor functions. This study presents serious clinical and ethical problems about the predictive value of identifying germline p5 3 mutations in presymptomatic carriers. However, accurate predictive t esting will be very useful in identifying unaffected individuals who a re at increased risk of developing cancer and in detecting cancer at a n early stage.