We have examined messenger RNA (mRNA) expression of estrogen receptor (ER) α wild-type ERβ (mRNA and protein), and ERβ exon 5 deletion variants (ERβ Δ5) in samples of normal human mammary gland obtained from 37 premenopausal subjects undergoing reduction mammoplasty. Comparing individual expressions, ERβ mRNA predominated, expressed in 34 of 37 samples (91%), whereas ERα was found in 21 of 37 cases (57%). Receptor combinations were then analyzed and compared. Most samples either coexpressed ERα with ERβ (54%) or expressed just ERβ (38%). Immunohistochemical analysis revealed that ERβ mRNA expression mirrored that of protein. Immunoreactivity was observed in the nucleus with additional evidence of cytoplastmic staining those epithelial cells lining the breast ducts. Sporadic immunoreactivity was also detected in stromal cells. Expression of wild type and ERβ Δ5 was analyzed, and their expression with ERα was compared. Most samples coexpressed wild-type ERβ and the splice variant (62%; P = 0.05), with 30% exclusively expressing wild-type ERβ. Although samples coexpressing wild type and variant ERβ showed no statistical association with ERα those samples expressing only wild-type ERβ, showed a trend toward associations with ERα (P = 0.07). In conclusion, our data would support a role for ERβ in the normal human mammary gland, where we propose it may be the dominant receptor.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism