Immunocytochemical localization of sex steroid hormone receptors in normal human mammary gland

Abstract

The sex steroids, estrogens, progesterone, and androgens, all play a role in mammary development and function. To precisely identify the sites of action of these steroids, we studied the localization of the estrogen receptor alpha (ERalpha) and ERbeta, the progesterone receptor A (PRA) and PRB, and androgen receptors (AR) in the normal human mammary gland. Immunocytochemical localization of ERalpha, ERbeta, PRA, PRB, and AR was performed with reduction mammoplasty specimens from premenopausal women. ERalpha, PRA, PRB, and AR were localized mostly to the inner layer of epithelial cells lining acini and intralobular ducts, as well as to myoepithelial cells scattered in the external layer of interlobular ducts. AR was also found in some stromal cells. ERbeta staining was more widespread, resulting in epithelial and myoepithelial cells being labeled in acini and ducts as well as stromal cells. These results suggest that all sex steroids can directly act on epithelial cells to modulate development and function of the human mammary gland. Estrogens and androgens can also indirectly influence epithelial cell activity by an action on stromal cells.

Figure 1

Immunolocalization of ERα (A,B), ERβ (C,D), and AR (E,F) in human mammary gland. ERα nuclear staining is found in the inner layer in acini (A) and the outer layer in an interlobular duct (B). ERβ staining is observed in nuclei of epithelial cells in both inner and outer layers in acini and ducts (C,D), as well as in stromal cells. The cytoplasm of epithelial cells is also clearly labeled. AR immunoreactivity is detected in nuclei of epithelial cells in the inner layer of acini (E) and outer layer of interlobular duct (F). A few stromal cells are also immunostained. E, epithelial cells; S, stromal cells. Bar = 20 μm.

Figure 2

Immunolocalization of PRA (A,B) and PRB (C,D) in human mammary gland. PRA-immunostained nuclei are found in the inner layer of acini and the outer layer of interlobular ducts. Cytoplasmic labeling is also detected in the PRA-expressing cells. PRB staining is restricted to nuclei. As for PRA, the immunopositive cells and the inner layer of acini and outer layer of interlobular ducts are observed. No stromal cells were labeled with either antiserum. E, epithelial cells. Bar = 20 μm.