Evaluation of oestrogen receptor β wild-type and variant protein expression, and relationship with clinicopathological factors in breast cancers

We addressed the clinicopathological significance of the oestrogen receptor (ER) β protein, including an ERβ variant, ERβcx, in normal human breast and breast cancer. The reverse transcriptase-polymerase chain reaction (RT-PCR) showed that wild-type ERβ (ERβw) mRNA expression was higher in normal than cancer tissues, and that ERβcx mRNA was higher in cancer than in normal tissues. Immunohistochemistry of 22 normal breast tissues and 57 breast cancers was performed with three different ERβ antibodies and one ERβcx antibody. All normal breast samples showed staining with the three ERβ antibodies, suggesting that ERβw might have a physiological role in oestrogen signalling in the normal breast. In breast cancer, expression of the ERβw protein correlated well with the expression of the ERα and progesterone receptor (PgR), as well as histological grade (HG), and tended to indicate a better prognosis than when ERβw was absent. Thirty-one (54%) breast cancer samples contained ERβcx, whereas the corresponding tissue for normal breast samples stained positive in only two (9%).