IMMUNOHISTOCHEMICAL AND BIOCHEMICAL-ANALYSIS OF THE ESTROGEN-REGULATED PROTEIN PS2, AND ITS RELATION WITH ESTROGEN-RECEPTOR AND PROGESTERONE-RECEPTOR IN BREAST-CANCER

Aims-(i) To assess the validity of an immunocytochemical technique for detecting pS2 protein in paraffin wax embedded tissue; (ii) to provid e further data on the relation between pS2 protein and oestrogen recep tor (ER) and progesterone receptor (PgR). Methods-Breast cancer excisi on biopsy specimens were obtained from 35 previously untreated patient s. An immunoradiometric assay was compared with an immunohistochemical method for measuring pS2 protein. ER and PgR were measured in cytosol fractions by enzyme immunoassay and the relation between the presence of these receptors and pS2 protein was assessed before and after subd ivision of the women into groups of over or under 50 years of age. Res ults-A good correlation was seen between the immunoradiometric and imm unohistochemical methods for pS2 protein measurement (r = 0.84; p = 0. 0001). Log-transformed data showed a significant correlation between i ncreasing values of ER and pS2 protein (r = 0.45; p = 0.006) and to a lesser extent between pS2 protein and PgR (r = 0.38; p = 0.03). Correl ations were also shown between pS2+ and PgR+ status (p = 0.01), and be tween ER and PgR positivity (p 0.05; Fisher's exact test). pS2+ protei n status was only associated with ER+ status in patients aged 50 years or less. Conclusions-The two methods for pS2 analysis are virtually i nterchangeable. This provides strong support for using immunohistochem istry for pS2 in paraffin wax embedded tissue. The association with ER positivity and pS2+ protein status only in the premenopausal patients may be due to the higher levels of oestrogenic stimuli in that group.