ERβ1 represses basal-like breast cancer epithelial to mesenchymal transition by destabilizing EGFR

Abstract

IntroductionEpithelial to mesenchymal transition (EMT) is associated with the basal-like breast cancer phenotypes. Sixty percent of basal-like cancers have been shown to express wild-type estrogen receptor beta (ERβ1). However, it is still unclear whether the ERβ expression is related to EMT, invasion and metastasis in breast cancer. In the present study, we examined whether ERβ1 through regulating EMT can influence invasion and metastasis in basal-like cancers.MethodsBasal-like breast cancer cells (MDA-MB-231 and Hs578T), in which ERβ1 was either overexpressed or down-regulated were analyzed for their ability to migrate and invade (wound-healing assay, matrigel-coated Transwell assay) as well as for the expression of EMT markers and components of the EGFR pathway (immunoblotting, RT-PCR). Co-immunoprecipitation and ubiquitylation assays were employed to examine whether ERβ1 alters epidermal growth factor receptor (EGFR) protein degradation and the interaction between EGFR and the ubiquitin ligase c-Cbl. The metastatic potential of the ERβ1-expressing MDA-MB-231 cells was evaluated in vivo in a zebrafish xenotransplantation model and the correlation between ERβ1 and E-cadherin expression was examined in 208 clinical breast cancer specimens by immunohistochemistry.ResultsHere we show that ERβ1 inhibits EMT and invasion in basal-like breast cancer cells when they grow either in vitro or in vivo in zebrafish. The inhibition of EMT correlates with an ERβ1-mediated up-regulation of miR-200a/b/429 and the subsequent repression of ZEB1 and SIP1, which results in increased expression of E-cadherin. The positive correlation of ERβ1 and E-cadherin expression was additionally observed in breast tumor samples. Down-regulation of the basal marker EGFR through stabilization of the ubiquitin ligase c-Cbl complexes and subsequent ubiquitylation and degradation of the activated receptor is involved in the ERβ1-mediated repression of EMT and induction of EGFR signaling abolished the ability of ERβ1 to sustain the epithelial phenotype.ConclusionsTaken together, the results of our study strengthen the association of ERβ1 with the regulation of EMT and propose the receptor as a potential crucial marker in predicting metastasis in breast cancer.

Estrogen receptor β sustains epithelial differentiation by regulating prolyl hydroxylase 2 transcription

“…The transcriptional regulation of a specific prolyl hydroxylase by ERβ is relevant to our understanding of how this receptor contributes to epithelial biology and cancer. Specifically, ERβ has been implicated in the differentiation of epithelial cells as indicated by the data presented here and previous studies (9,10,12). We argue that the ERβ regulation of PHD2-mediated HIF-1α degradation is a major factor in the ability of ERβ to prevent dedifferentiation and an EMT.…”

“…In the prostate, the discovery of ERβ (4, 5) has generated intense interest in the roles played by this ER in several tissues including prostate and breast epithelia (6)(7)(8)(9)(10)(11). Increasing evidence supports the hypothesis that ERβ functions to maintain epithelial differentiation in the prostate and breast (9,10,12,13). In the normal prostate, ERβ contributes to epithelial differentiation as evidenced by the observation that ERβ knockout mice exhibit altered differentiation in the ventral prostate, whereas the glands of ERα knockout mice lack these lesions and appear to be normal (12).…”

Lapatinib induces p27Kip1-dependent G₁ arrest through both transcriptional and post-translational mechanisms

“…27,28 Furthermore, ERβ1 inhibits epithelial-mesenchymal transition (EMT) and invasion in basal-like breast cancer cells. 29 ERβ2 appears to be a powerful prognostic indicator in breast cancer, and nuclear and cytoplasmic expression differentially affect outcome. Nuclear ERβ2 immunoreactivity was shown to be significantly associated with better overall survival, while cytoplasmic ERβ2 was significantly associated with high-grade tumors.…”

ERβ Regulates NSCLC Phenotypes by Controlling Oncogenic RAS Signaling

“…S2). The ligand-independent antitumorigenic function of ERb1 that was observed in NSCLC cells has also been previously described in breast, colon, and prostate cancer cells (23,24,27,28). Interestingly, the effect of ERb1 was more potent in H1299 and A549 cells that express mutant RAS compared with H661 cells that carry wild-type RAS, suggesting that ERb1 may suppress the growth of NSCLC cells by targeting oncogenic RAS signaling (Fig.…”

“…Nuclear and cytoplasmic extracts were prepared as described before (24). The lysates were subjected to SDS-PAGE and the proteins were transferred onto nitrocellulose membranes.…”