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.