P53 GENE ALTERATIONS IN SPECIAL TYPES OF BREAST-CARCINOMA - A MOLECULAR AND IMMUNOHISTOCHEMICAL STUDY IN ARCHIVAL MATERIAL

The p53 locus on the short arm of chromosome 17 at 17p13.1 was examined for small genomic deletions and mutations in 23 formalin-fixed, paraffin-embedded cases of special types of breast carcinoma (six medullary, seven apocrine, five differentiated tubular, and five papillary). p53 mutations in the evolutionarily conserved exons 5-9 were detected in 11 cases (four apocrine, two papillary, two medullary, and three differentiated tubular), using the novel non-radioactive PCR-based Hydrolink mutation detection enhancement (MDE) method, and confirmed by direct sequencing of the PCR products. Missense mutations causing amino acid substitutions were evenly distributed among exons. One case of apocrine carcinoma showed a polymorphism at codon 213 (CGA-->CGG). Twelve out of 23 cases were found to express a strong nuclear signal against CM-1 and DO-7, two anti-p53-specific antibodies. Small genomic deletions in the vicinity of the p53 locus were detected in 11 tumours (three papillary, three differentiated tubular, two medullary, and three apocrine carcinomas), using the multiplex PCR method. No statistical correlation was found between deletions at 17p13.1 and p53 mutations (P<0 . 5). In addition, p53 mutations and immunoexpression correlated with the c-erbB-2 gene product, an oncogenic protein that has been implicated in cell cycle control (P<0 . 001). Our findings suggest that genomic alterations of the p53 gene are quite common events associated with special types of breast carcinoma, particularly of the apocrine subtype, but the prognostic value is unlikely to be of clinical importance.