p53 gene mutation, tumor p53 protein overexpression, and serum p53 autoantibody generation in patients with breast cancer

Objectives: Autoantibodies against the p53 tumor suppressor protein have be en detected in the serum of a proportion of patients with various cancers. The generation of such antibodies has been proposed to be due to either tum or p53 protein accumulation or to the type of p53 gene mutation. These hypo theses are examined in the present study. Design and methods: Using immunofluorometric assays, we studied 195 patient s with primary breast cancer for the presence of p53 antibodies in serum an d p53 protein accumulation in the corresponding tumor. Seventeen patients ( 9%) were p53 antibody-positive and 77 (40%) overexpressed p53. Ten of the 1 7 p53 antibody-positive patients had tumor p53 accumulation and 7 were nega tive for p53. Statistical analysis revealed a weak association between the presence of p53 antibodies and p53 protein accumulation (p = 0.05). Direct DNA sequencing of exons 1-11 of the p53 gene was performed for 16 p53 antib ody-positive and 16 p53 antibody-negative patients. Results: Five of the seropositive and eight of the seronegative patients ha d a p53 gene mutation. Four of the five mutations in the p53 antibody-posit ive patients affected a Tyr residue, whereas none of the gene abnormalities in the seronegative patients had such an effect. Conclusions: We conclude that p53 antibodies tend to develop in patients wi th tumor p53 accumulation, but p53 accumulation is neither sufficient nor n ecessary for the generation of the immune response. Further, p53 antibody-p ositive patients do not have higher frequency of p53 gene mutations than p5 3 antibody-negative patients, but the former patient group is associated wi th a Tyr substitution in the protein product. Copyright (C) 2000 The Canadi an Society of Clinical Chemists.