Expression of Estrogen Receptor-β in Human Breast Tumors

The expression of a recently described novel estrogen receptor, ER-β, was detected in several human breast tumor biopsy samples and several human breast epithelial cell lines using reverse transcription and polymerase chain reaction (RT-PCR) analysis. Cloning and sequencing of the PCR product from a breast tumor confirmed the identity of the sequence with that of the ER-β mRNA previously reported in human testis. The expression of ER-β was not correlated with that of ER-α, and both ER-α positive and ER-α negative cell lines expressed ER-β mRNA. However, some breast tumors and some cell lines coexpress ER-β and ER-α mRNA. Our data support a possible role for ER-β in human breast cancer.