Estrogen Receptor Functional Activity Changes during Differentiation of Mammary Epithelial Cells

Abstract

Mammary gland development involves complex cycles of proliferation, differentiation, and morphogenesis, regulated by hormones including estrogens, prolactin (PRL), and epidermal growth factor (EGF). The mouse mammary epithelial cell line HC11 has been shown to be valuable for investigations of differentiation of mammary gland. In this study, we show that HC11 cells express estrogen receptor (ER)alpha and ER beta proteins at all developmental stages. We have established two different stable HC11 cell lines; H-estrogen response element (ERE) containing an ERE-reporter and H-Bc containing a beta-casein reporter. Transcription of the ERE-reporter was activated only in proliferating cells in the presence of EGF. When the cells entered the differentiation program, in the absence of EGF, estradiol-induced transcription of the ERE reporter was repressed, and similar results were obtained when MAPK signaling was inhibited in proliferating cells. We propose that these findings are related to changes in ER corepressor levels, regulated by EGF. We also report that the beta-casein reporter was activated in terminally differentiated cells and that this induction was effectively repressed by estradiol treatment. Finally, we show a physical interaction between endogenous ER alpha and signal transducer and activator of transcription 5 in differentiated HC11 cells. In summary, our results show that ER functional activity changes during differentiation of HC11 cells.

3-Methylcholanthrene Displays Dual Effects on Estrogen Receptor (ER) α and ERβ Signaling in a Cell-Type Specific Fashion

“…HC11 cells and stably transfected 3xERE HC11 cells (H-ERE; described previously in Faulds et al, 2004) were maintained in RPMI 1640 medium (Invitrogen, Carlsbad, CA) supplemented with 8% fetal calf serum (FCS; Invitrogen), L-glutamine (Invitrogen), 50 g/ml gentamicin (Invitrogen), 10 ng/ml epidermal growth factor (Sigma), and 5 g/ml insulin (Sigma). HepG2 and CV-1 cells were routinely maintained in Dulbecco's modified Eagle's medium supplemented with 10% FCS and penicillin (100U/ml) and streptomycin (100 g/ml).…”

The WNT-controlled transcriptional regulator LBH is required for mammary stem cell expansion and maintenance of the basal lineage

“…Conversely, LBH was stably introduced into murine HC11 (Fig. 7D), one of the few normal MEC lines with luminal characteristics and endogenous ERα expression (Faulds et al, 2004).…”

Crosstalk between steroid receptors and the c-Src-receptor tyrosine kinase pathways: implications for cell proliferation

“…Genes stimulated in the absence of canonical PREs or EREs include important physiological targets such as cyclin D1, p21, and the E2-sensitive PR promoters (Schlegel et al, 1999;Petz and Nardulli, 2000;Petz et al, 2002). An increasing number of steroidresponsive genes have been identified that are regulated via ER interactions with Sp1 (Stoner et al, 2004), the signal transducers and activators of transcription (STAT) family of transcription factors (Faulds et al, 2001(Faulds et al, , 2004 and proteins on AP1 sites (Kushner et al, 2000), as well as by PR interactions with AP-1 binding proteins (Bamberger et al, 1996). There is some isoform selectivity for these responses, as only ERa can stimulate genes via the Sp1 pathway (Saville et al, 2000), and the two ER isoforms are differentially regulated by E2 and antiestrogens at AP1 sites (Paech et al, 1997 In reproductive tissues such as uterus and breast, estrogen, IGF-1, and EGF are all mitogenic, and may play an important role in the growth of tumors in these tissues.…”