Activated oestrogen receptor in human breast cancer: clinical and biochemical correlates

The oestrogen receptor (ER) contains a DNA-binding site, the activity of which can be determined by its binding to oligo(dT)-cellulose. In premenopausal women with breast cancer, 53 per cent of ER-positive tumours were capable of binding to oligo(dT)-cellulose (activated ER): the corresponding proportion in postmenopausal patients was 70 per cent (P less than 0.005). Disease recurrence was significantly increased in patients whose tumours contained non-activated rather than activated ER. The presence of activated ER was associated with a significant increase in the median activity of creatine kinase in premenopausal and postmenopausal patients. In postmenopausal patients the incidence of progesterone receptor was higher in tumours that contained activated ER than in tumours that contained ER not capable of binding to oligo(dT)-cellulose (non-activated). The incidence of activated ER was not related to disease stage or nodal involvement at the time of sampling. The data suggest that ER-positive tumours can be divided, according to the activity of the DNA-binding site, into subgroups with differing biological properties.