P53 expression in breast cancer

Abstract

Immunohistochemical evaluation of 200 primary breast cancers with the anti-p53 mouse monoclonal antibody (MAb) PAb421 showed positivity in nuclei of malignant cells in 31 cases (15.5%). PAb421⁺ cases were significantly more frequently epidermal growth factor receptor (EGF-R)-positive (67.7%; p < 0.001) and estrogen receptor (ER)-negative (73.3%; p < 0.001); they displayed surface histocompatibility class-1 (80.6%; p < 0.01) and II (74.2%; p < 0.05) antigens. Low values for progesterone receptor (mean 67.20 ± 25.2 fmol/mg; p < 0.05) and a high number of cells positive for the proliferationassociated antigen Ki-67 (log mean 6.88 ± 0.33; p < 0.01) were found in PAb421⁺ tumors as well as a high number of grade-3 infiltrating duct carcinomas (70%; p = 0.01). Of the 200 cases of mammary carcinoma, 88 were further analyzed using another human specific anti-p53 MAb PAb1801, and 40 (45.5%) were found positive. This MAb stained all the PAb421⁺ cases and was significantly associated with negative ER status (39.5%; p < 0.05) and high Ki-67 scores (log mean 6.93 ± 0.24; p = 0.001). Analysis of PAb1801⁺/Pab421⁻ cases for HLA antigens, EGF-R and ER showed a phenotype similar to that of the p53⁻ve/ER⁺ carcinomas, except for the high Ki-67 score. No differences in age of the patient, number of involved nodes, tumor size, ploidy or labelling index scores were evident between p53⁺ and ⁻ carcinomas. We concluded that p53 in mammary carcinomas is associated with ER-negative, growth factor receptor-positive, high-grade tumors, and is a promising new parameter to evaluate the cellular biology and prognosis of breast cancer.