SEDIMENTATION PROFILES OF THE OESTROGEN RECEPTOR FROM BREAST TUMOURS OF MAN AND RAT USING VERTICAL-TUBE ROTOR CENTRIFUGATION

Abstract

In rat mammary tumours and uteri it was found that reaction time, ionic strength, reproductive state and storage in liquid nitrogen affected the form of the oestrogen receptor detected by sucrose density-gradient analysis using a vertical-tube rotor. A standard method of gradient analysis was defined. The sedimentation profile of the oestrogen receptor was compared in three types of experimental rat mammary tumour of known hormonal sensitivity. These were two lines of ovary-independent transplantable tumours and those tumours induced by dimethylbenz(a)anthracene (DMBA) which are mainly ovary-dependent. In all three types of tumour the 8S receptor was the predominant molecular form (32 out of 36 tumours induced by DMBA and 11 out of 13 transplantable tumours). Sedimentation profiles of the oestrogen receptor were also examined in 46 human breast carcinomata found to be receptor-positive by the dextran-coated charcoal technique. Of these, 17 were found to be receptor-negative by gradient analysis and 28 out of 29 receptor-positive tumours contained 8S receptor. It was concluded that (1) 8S receptor is the predominant molecular form in both human and rat mammary tumours, (2) molecular form of receptor is not related to ovarian dependence in these rat mammary tumours and (3) gradient analysis seems unlikely to provide additional discrimination in the prediction of response to endocrine therapy over that provided by simpler methods.