Prognostic value of cytosolic p53 protein in breast cancer

The prognostic value of cytosolic p53 protein was evaluated in 458 operable breast carcinomas by immunoblotting using the monoclonal antibody PAb 1801. Two hundred and five carcinomas (45%) showed positive p53 accumulation and 55% were p53 negative. When comparing p53 positivity and other clinicopathological parameters, significant differences were found with younger age (p = 0.017), premenopausal status (p = 0.003), increasing tumor size (p = 0.026), negative estrogen receptor (p = 0.003) and negative progesterone receptor (p = 0.047), but not with histologic grade, axillary lymph node status, stage or erbB-2 expression. With a median follow-up of 34 months (range 3-70), relapse has occurred in 73 patients. Disease-free survival curves showed that patients with p53-positive tumors had a significantly shorter disease-free survival than patients with p53-negative carcinomas (log-rank test, p = 0.027). A multivariate analysis of disease-free survival showed that p53, tumor size, histologic grade and progesterone receptor had significant independent prognostic value. The immunoblotting technique was controlled with p53 immunohistochemistry in 94 paired samples. We obtained a statistically significant correlation (p = 0.0004) between the two methods. Our results show that the immunoblotting technique offers an alternative approach in evaluating the p53 status of breast biopsy material using cytosolic extracts, and confirm that p53 accumulation is a significant independent indicator of a poor prognosis in operable breast carcinoma.