p53 allele losses, mutations and expression in breast cancer and their relationship to clinico‐pathological parameters

The p53 locus on the short arm of chromosome 17 at 17p 13.1 was examined for loss of heterozygosity, mutation, mRNA and protein expression in 60 primary breast cancers. Allele loss around the p53 locus was detected in 19/45 informative tumours (42%). p53 mutations in the evolutionarily conserved exons 5 to 9 were detected in 17/60 (28%) by amplification mismatch and confirmed by direct DNA sequencing. p53 mRNA expression was detected by Northern blot in 36/59 (61%) of tumours, and p53 protein expression using antibody 1801 on frozen‐tissue sections in 13/44 of the tumours examined. p53 mutation was significantly associated with oestrogen‐receptor‐poor tumours (p < 0.01) and hence with poor prognosis, but not with other clinical or pathological parameters. There was no statistical correlation between loss of heterozygosity around the p53 locus at 17p 13.1 and p53 mutation. Furthermore, p53 mutation was not associated with p53 expression detected by immunohistochemical staining with antibody 1801 or as p53 mRNA. In addition, events on 17p (allele losses, p53 mutation, p53 expression) were independent of c‐erb B‐2 expression. In breast cancer, by contrast with colorectal, lung and ovarian cancer, there appears‐to be no clear association between p53 DNA abnormalities and p53 expression.