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

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Abstract
The identification of a second oestrogen receptor, oestrogen receptor (ER) β, has led to a need to assess the relative importance of the classical ERα and ERβ in human breast and breast carcinomas. ERα and ERβ 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 ERα and ERβ was performed in 62 carcinomas, the 38 non-malignant breast tissues, and 32 normal breast samples with menstrual cycle data. ERα mRNA was detected in 92% of breast cancers, with ERβ mRNA (wild-type and/or variant form) in 85%; 72% had ERα protein, 62% progesterone receptor (PgR), and 32% ERβ. ERα protein had a strong correlation with grade; ERβ did not, although it was present in three of four grade I carcinomas and in special types. There was no correlation between the presence of ERα and ERβ protein. In non-malignant breast, similar expression of ERα and β was observed, apart from expression of ERβ in stromal cells and myoepithelium, the latter being confirmed by RT-PCR and western blotting. There were differences in ERα in relation to the menstrual cycle but not PgR or ERβ. The findings indicate a need to understand the role and regulation of ERβ in normal breast and the reason for its down-regulation in mammary carcinogenesis. Copyright © 2002 John Wiley & Sons, Ltd.