Frequency and pattern of p53 gene mutation in a cohort of Spanish women with node-negative breast cancer

Ethnic, racial and regional differences in the frequency and pattern of p53 gene mutations have been well documented. Some of these differences have b een shown to have an impact on the survival of patients with breast cancer. In this study we explored the frequency and pattern of p53 abnormality in a cohort of Spanish women with node-negative breast cancer using PCR, subcl oning and DNA sequencing of archival tumors. One hundred and seventy-eight cases of breast cancer diagnosed between 1981 and 1986 at the University of Oviedo Hospital in Oviedo, Spain were subjects of this study. Sequence ana lysis of exons 5 through 8 of p53 was performed on subcloned PCR-amplified DNA, extracted from formalin-fixed, paraffin-embedded tumors. Appropriate p ositive, negative, PCR, and polymerase controls were utilized and evaluated . Duplicate samples of the genomic DNA were re-evaluated on all cases showi ng more than one mutation. One hundred and five out of 178 breast cases (59 %) carried one or more p53 gene mutations. Mutations were distributed rando mly from codon 128 to 305. There were 123 (88%) transition, 10 (7%) transve rsion, 5 (3.5%) splice junction mutations, and 2 (1.5%) deletions. Eighty-t hree cases (61.5%) had missense mutation, 45 (33.5%) silent, 5 (3.5%) nonse nse and 2 (1.5%) frameshifts. Eighty (75%) of 120 transitions were G:C to A :T, 11 (25%) of which occurred at CpG sites. Sixteen mutations were in nove l codons not reported in breast cancers previously. Codons with the highest frequency of mutations in this group were 278, 273, 213 and 227. We also d etected 27 tumors with more than one mutation within a single exon or in di fferent exons in the same patient. These findings suggest that the frequenc y and pattern of p53 mutations in this group of Spanish women with breast c ancer is different than those reported in the United States and Northern Eu rope.