FREQUENT P53 GENE-MUTATIONS AND NOVEL ALLELES IN FAMILIAL BREAST-CANCER

Mutations in the p53 gene were detected in 58% of tumor DNAs of patien ts with a family history of breast cancer (FHBC) compared to 13% with sporadic breast cancer. Seven of 18 FHBC tumors contained the same G t o C transversion in codon 156. Novel alleles of altered length were se en in one or more loci on chromosome 17 in U of 18 patients with FHBC but only in a single locus in 8 of 14 patients with sporadic breast ca ncer. The frequency of tumors with mutations in p53, often multiple, a ccompanied by the appearance of multiple altered-length alleles sugges t that DNA replication or repair defects may presage genomic instabili ty in cases with FHBC.