Immunoradiometric measurement of pS2 in breast cancer - Correlation with steroid receptors and plasminogen activators

pS2 was measured by radioimmunometric assay in tumour extracts from 197 bre ast cancer patients. Values ranged from 0 to 50 ng/mg protein (mean 9.6 and median 3 ng/mg). We found no correlation with age, menopausal status, noda l metastases, disease stage or tumour histology. There was, however, a line ar relationship with both ER (p < 0.0001) (particularly nuclear ER) and PR (p < 0.0001) expression determined by enzyme immunoassay (ELISA), as well a s a good correlation when high and low expressors were stratified on the ba sis of combined ER/PR expression using consensus cut-off points. Only 15% o f ER - ve/PR - ve patients were classified as pS2 + ve compared with 83% of those who were ER + ve/PR + ve. pS2 was also directly correlated with high expression of tPA and inversely with uPA. Comparison with previous studies showed that the current ELISA method produced consistent results, in contr ast to other methods, particularly those based on immunohistochemical detec tion. The close relationship between pS2 and both steroid receptors suggest s that pS2 may be important in terms of defining hormone-responsive patient s who are likely to benefit from endocrine therapy.