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.
Highlights
Epithelial to mesenchymal transition (EMT) is associated with the basal-like breast cancer phenotypes
The inhibition of EMT correlates with an ERb1-mediated up-regulation of miR-200a/b/ 429 and the subsequent repression of ZEB1 and SIP1, which results in increased expression of E-cadherin
Downregulation of the basal marker epidermal growth factor receptor (EGFR) through stabilization of the ubiquitin ligase c-Cbl complexes and subsequent ubiquitylation and degradation of the activated receptor is involved in the ERb1-mediated repression of EMT and induction of EGFR signaling abolished the ability of ERb1 to sustain the epithelial phenotype
Summary
Epithelial 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 (ERb1). It is still unclear whether the ERb expression is related to EMT, invasion and metastasis in breast cancer. An integrated analysis of copy number and gene expression split the intrinsic and CK17 [1,4] They show partial overlap with the triple-negative breast cancers that are characterized by a lack of HER2 gene amplification and estrogen and progesterone receptor expression. 75% of triple-negative breast cancers are classified as basal-like tumors on the basis of their overall gene-expression profile. Recent studies have suggested a correlation between the basal phenotypes and epithelial to mesenchymal transition (EMT) [7]
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