Oestrogen receptors alpha and beta differ in normal human breast and breast carcinomas

The identification of a second oestrogen receptor, oestrogen receptor (ER) beta, has led to a need to assess the relative importance of the classical MY and ERbeta in human breast and breast carcinomas. ERalpha and ERbeta mRNA was assessed in 61 carcinomas, 8 benign breast lesions, and 30 samples of normal breast using reverse transcriptase (RT)-nested polymerase chain reaction (PCR). Immunohistochemical analysis of ERalpha and ERbeta was performed in 62 carcinomas, the 38 non-malignant breast tissues, and 32 normal breast samples with menstrual cycle data. Me mRNA was detected in 9217'c of breast cancers, with ER mRNA (wild-type and/or variant form) in 85%; 72% had ERa protein, 62% progesterone receptor (PgR), and 32% ERbeta. ERalpha protein had a strong correlation sitli grade, ERbeta did not, although it was present in three of four grade 1 carcinomas and in special types. There was no correlation between the presence of ERalpha and ERbeta protein. In non-malignant breast, similar expression of ERalpha and beta was observed, apart from expression of ERbeta in stromal cells and myoepithelium, the latter being confirmed by RT-PCR and western blotting. There were differences in ERalpha in relation to the menstrual cycle but not PgR or ERbeta. The findings indicate a need to understand the role and regulation of ERbeta in normal breast and the reason for its down-reguIation in mammary carcinogenesis. Copyright (C) 2002 John Wiley Sons, Ltd.