EXPRESSION OF PS2 PROTEIN IN BREAST-CANCER

The pS2 protein was first detected in the oestrogen-dependent breast c ancer cell line MCF-7. It may have prognostic value for primary breast cancer, and could be used to predict clinical responsiveness to endoc rine therapy. In a retrospective study, the concentrations of pS2 prot ein were determined in 434 cytosol specimens using an immunoradiometri c assay. The median values (4, 6 and 3 ng/mg protein) and the third qu artiles (27, 26 and 29 ng/mg) in benign breast tumours (n=17), and in primary (n=325) and recurrent (n=37) breast carcinomas were of the sam e order of magnitude. In primary breast cancer, high pS2 values (>26 n g/mg) correlated significantly with a positive oestrogen receptor (ER) status and a high grade of tumour differentiation (P=0.01). As many a s 85% of the pS2 positive tumours were ER positive. A marginally signi ficant correlation (P=0.06) was also found between pS2 status and the quantitative expression of the ER. However, the pS2 values in ER posit ive endometrial carcinomas (n=12) as well as in other benign and malig nant genital tumours (n=43) were more than 30 times lower than those m easured in breast tumours. The results reveal a close association betw een pS2 protein and ER status which appears to be limited to breast ca ncer.