Expression of the pS2 Protein and Its Relation with Estrogen and Progesterone Receptor in Breast Cancer

ABSTRACT

Expression of the pS2 protein in breast carcinoma is a useful guide to evaluate the prognosis and response to tamoxifen. The pS2 protein is an estrogen-regulated 60 amino acid protein which was originally discovered following the screening of cDNA libraries in MCF-7 breast carcinoma cells and is induced through estrogen-dependent transcription of the pS2 gene. The presence of the pS2 protein in breast cancer is considered as valuable as the receptor status, or even more so, in predicting the response to hormonal therapy. We have investigated the pS2 protein expression in 62 cases of primary breast cancer in order to know the relationship between the expression rate of the pS2 protein and hormonal receptor status using immunohistochemical procedures on formalin-fixed and paraffin-embedded tissues. Concomitantly, both the estrogen receptors (ER) and progesterone receptors (PR) were examined using the immunohistochemical technique. Positive staining for the pS2 was seen in forty-nine cases (79%) of the tumors. Forty three cases (88%) of the pS2 positive tumors were ER positive and forty one cases (84%) of the pS2 positive tumors were PR positive ; forty six cases (93%) of pS2 positive tumors were positive for ER and/or PR. The pS2 status correlated significantly with the ER (p<0.0001) and PR (p<0.001). The results reveal a close association between the pS2 protein and either or both the ER and PR status.