Enzyme-linked immunosorbent assay of pS2 in breast cancers, benign tumors, and normal breast tissues. Correlation with prognosis and adjuvant hormone therapy.

An enzyme-linked immunosorbent assay using monoclonal and polyclonal antibodies against recombinant pS2 was devised. It was used to measure pS2 concentration in the cytosol of 339 breast cancer, 15 fibroadenomas, 16 cases of benign breast disease, and 6 normal breast tissues. The mean value of pS2 concentration was higher in cancer, but the protein could be detected readily in benign tumors and even in normal breast. The concentration of pS2 was significantly lower in postmenopausal women and tumors of differentiation Grade 3. The pS2 concentration was correlated strongly with the presence of estrogen receptors (ER) and progesterone receptors (PR). No correlation was observed with the size, histologic type of the tumor, and lymph node status. The prognostic value of pS2 appeared relatively limited. It was clear cut only for a relatively small group of patients (approximately 15%), who had low concentrations of pS2 (less than or equal to 0.32 ng/mg of protein). These patients had a shorter disease-free interval and overall survival time. The most striking correlation was observed with the outcome of adjuvant hormone therapy. pS2 concentration was shown to be the most potent prognostic factor, preceding even ER.