Co-expression of estrogen receptor-alpha and targets of estrogen receptor action in proliferating monkey mammary epithelial cells

INTRODUCTION: Failure to detect co-expression of estrogen receptor-alpha (ERα) and proliferation 'markers' such as Ki67 in human mammary epithelium led to the view that estrogen acts indirectly to stimulate mammary epithelial proliferation. The mitotic index was so low in prior studies, however, that transient co-expression of ERα and Ki67 during the cell cycle could have been below detection limits. METHODS: Immunohistochemistry was used on mammary tissue sections from estrogen treated rhesus monkeys to investigate co-expression of ERα and the proliferation antigen Ki67. Using the same methods, we investigated the cell localization of proteins involved in estrogen-induced proliferation, including cyclin D1, stromal cell-derived factor (SDF)-1, and MYC. RESULTS: ERα was co-expressed with the proliferation marker Ki67 as well as with SDF-1, MYC and cyclin D1 in mammary epithelial cells from estrogen-treated monkeys. CONCLUSION: ERα is expressed in proliferating mammary epithelial cells together with the estrogen-induced proteins MYC, cyclin D1 and SDF-1, consistent with a direct mitogenic action by estrogen in primate mammary epithelium

Co-localization of estrogen receptor (ER)α and Ki67 in primate mammary epithelial cells

<p><b>Copyright information:</b></p><p>Taken from "Co-expression of estrogen receptor-alpha and targets of estrogen receptor action in proliferating monkey mammary epithelial cells"</p><p>Breast Cancer Research 2006;8(1):R10-R10.</p><p>Published online 3 Jan 2006</p><p>PMCID:PMC1413986.</p><p>Copyright © 2006 Dimitrakakis et al.; licensee BioMed Central Ltd.</p> ERα and Ki67 immunostaining (brown) are detected in the same epithelial cells on serial sections (3 μm) of primate mammary tissue, for example, cells 4–7. Bar = 20 μm

Colocalization of estrogen receptor (ER)α and cyclin D1 in mammary epithelial cells

<p><b>Copyright information:</b></p><p>Taken from "Co-expression of estrogen receptor-alpha and targets of estrogen receptor action in proliferating monkey mammary epithelial cells"</p><p>Breast Cancer Research 2006;8(1):R10-R10.</p><p>Published online 3 Jan 2006</p><p>PMCID:PMC1413986.</p><p>Copyright © 2006 Dimitrakakis et al.; licensee BioMed Central Ltd.</p> Double immunofluorescence in the same tissue section shows: ERα, green nuclear staining; cyclinD1, red nuclear staining; ERα and cyclinD1: yellow nuclear staining. Arrows indicate cells co-expressing ERα and cyclinD1. Bar = 20 μm