Studies on oestrogen receptor-alpha and -beta mRNA in breast cancer

The oestrogen receptor (ER) is widely used to predict response to tamoxifen in patients with breast cancer. Recently a new form of ER known as ER-beta was discovered, the original ER is now designated ER-alpha. In this invest igation, ER-alpha and ER-beta were measured in 107 breast carcinomas and 22 fibroadenomas. Using reverse transcriptase-polymerase chain reaction (RT-P CR), ER-beta mRNA, but not ER-alpha mRNA was expressed more frequently in f ibroadenomas than carcinomas. In the carcinomas, ER-beta mRNA was present i n a greater proportion of samples positive for ER-alpha mRNA than in those locking this form of tile receptor. ER-alpha, but not ER-beta mRNA, was sig nificantly associated with ER protein-positivity in the cancers. ER-alpha m RNA was also positively related to progesterone receptors (PR), but ER-beta mRNA showed an inverse relationship with PR. We conclude that the presentl y used enzyme-linked immunosorbent assay (ELISA) for ER appears to be mostl y measuring ER-alpha and is unlikely to be detecting ER-beta. (C) 2001 Else vier Science Ltd. All rights reserved.