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Breast cancer anti-estrogen resistance 3 inhibits transforming growth factor ?/Smad signaling and associates with favorable breast cancer disease outcomes.

ABSTRACT: This study helps to define the implications of breast cancer anti-estrogen resistance 3 (BCAR3) in breast cancer and extends the current understanding of its molecular mechanism of action. BCAR3 has been shown to promote cell proliferation, migration and attachment to extracellular matrix components. However, in a cohort of metastatic breast cancer patients who received tamoxifen treatment, high BCAR3 mRNA levels were associated with favorable progression-free survival outcome. These results suggest that, besides its established roles, BCAR3 may have additional mechanisms of action that regulate breast cancer aggressive phenotype. In this study, we investigated whether BCAR3 is a novel antagonist of the canonical transforming growth factor ? (TGF?) pathway, which induces potent migration and invasion responses in breast cancer cells.We surveyed functional genomics databases for correlations between BCAR3 expression and disease outcomes of breast cancer patients. We also studied how BCAR3 could regulate the TGF?/Smad signaling axis using Western blot analysis, coimmunoprecipitation and luciferase assays. In addition, we examined whether BCAR3 could modulate TGF?-induced cell migration and invasion by using an automated imaging system and a confocal microscopy imaging-based matrix degradation assay, respectively.Relatively low levels of BCAR3 expression in primary breast tumors correlate with poor distant metastasis-free survival and relapse-free survival outcomes. We also found a strong correlation between the loss of heterozygosity at BCAR3 gene alleles and lymph node invasion in human breast cancer, further suggesting a role for BCAR3 in preventing disease progression. In addition, we found BCAR3 to inhibit Smad activation, Smad-mediated gene transcription, Smad-dependent cell migration and matrix digestion in breast cancer cells. Furthermore, we found BCAR3 to be downregulated by TGF? through proteasome degradation, thus defining a novel positive feedback loop mechanism downstream of the TGF?/Smad signaling pathway.BCAR3 is considered to be associated with aggressive breast cancer phenotypes. However, our results indicate that BCAR3 acts as a putative suppressor of breast cancer progression by inhibiting the prometastatic TGF?/Smad signaling pathway in invasive breast tumors. These data provide new insights into BCAR3's molecular mechanism of action and highlight BCAR3 as a novel TGF?/Smad antagonist in breast cancer.

SUBMITTER: Guo J

PROVIDER: S-EPMC4311507 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Breast cancer anti-estrogen resistance 3 inhibits transforming growth factor β/Smad signaling and associates with favorable breast cancer disease outcomes.

Guo Jimin J Canaff Lucie L Rajadurai Charles Vincent CV Fils-Aimé Nadège N Tian Jun J Dai Meiou M Korah Juliana J Villatoro Manuel M Park Morag M Ali Suhad S Lebrun Jean-Jacques JJ

Breast cancer research : BCR 20141213 6

<h4>Introduction</h4>This study helps to define the implications of breast cancer anti-estrogen resistance 3 (BCAR3) in breast cancer and extends the current understanding of its molecular mechanism of action. BCAR3 has been shown to promote cell proliferation, migration and attachment to extracellular matrix components. However, in a cohort of metastatic breast cancer patients who received tamoxifen treatment, high BCAR3 mRNA levels were associated with favorable progression-free survival outco ...[more]

PMID: 25499443

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Project description:BackgroundEstrogen receptor β (ERβ) has been reported to play an anti-cancer role in breast cancer, but the regulatory mechanism by which ERβ exerts this effect is not clear. Claudin-6 (CLDN6), a tight junction protein, acts as a tumor suppressor gene in breast cancer. Our previous studies have found that 17β-estradiol (E2) induces CLDN6 expression and inhibits MCF-7 cell migration and invasion, but the underlying molecular mechanisms are still unclear. In this study, we aimed to investigate the role of ERβ in this process and the regulatory mechanisms involved.MethodsPolymerase chain reaction (PCR) and western blot were used to characterize the effect of E2 on the expression of CLDN6 in breast cancer cells. Chromatin immunoprecipitation (ChIP) assays were carried out to confirm the interaction between ERβ and CLDN6. Dual luciferase reporter assays were used to detect the regulatory role of ERβ on the promoter activity of CLDN6. Wound healing and Transwell assays were used to examine the migration and invasion of breast cancer cells. Western blot, immunofluorescence and transmission electron microscopy (TEM) were performed to detect autophagy. Xenograft mouse models were used to explore the regulatory effect of the CLDN6-beclin1 axis on breast cancer metastasis. Immunohistochemistry (IHC) was used to detect ERβ/CLDN6/beclin1 expression in breast cancer patient samples.ResultsHere, E2 upregulated the expression of CLDN6, which was mediated by ERβ. ERβ regulated CLDN6 expression at the transcriptional level. ERβ inhibited the migration and invasion of breast cancer cells through CLDN6. Interestingly, this effect was associated with CLDN6-induced autophagy. CLDN6 positively regulated the expression of beclin1, which is a key regulator of autophagy. Beclin1 knockdown reversed CLDN6-induced autophagy and the inhibitory effect of CLDN6 on breast cancer metastasis. Moreover, ERβ and CLDN6 were positively correlated, and the expression of CLDN6 was positively correlated with beclin1 in breast cancer tissues.ConclusionOverall, this is the first study to demonstrate that the inhibitory effect of ERβ on the migration and invasion of breast cancer cells was mediated by CLDN6, which induced the beclin1-dependent autophagic cascade.

Project description:We have previously demonstrated that endoxifen is the most important tamoxifen metabolite responsible for eliciting the anti-estrogenic effects of this drug in breast cancer cells expressing estrogen receptor-alpha (ER?). However, the relevance of ER? in mediating endoxifen action has yet to be explored. Here, we characterize the molecular actions of endoxifen in breast cancer cells expressing ER? and examine its effectiveness as an anti-estrogenic agent in these cell lines.MCF7, Hs578T and U2OS cells were stably transfected with full-length ER?. ER? protein stability, dimer formation with ER? and expression of known ER target genes were characterized following endoxifen exposure. The ability of various endoxifen concentrations to block estrogen-induced proliferation of MCF7 parental and ER?-expressing cells was determined. The global gene expression profiles of these two cell lines was monitored following estrogen and endoxifen exposure and biological pathway analysis of these data sets was conducted to identify altered cellular processes.Our data demonstrate that endoxifen stabilizes ER? protein, unlike its targeted degradation of ER?, and induces ER?/ER? heterodimerization in a concentration dependent manner. Endoxifen is also shown to be a more potent inhibitor of estrogen target genes when ER? is expressed. Additionally, low concentrations of endoxifen observed in tamoxifen treated patients with deficient CYP2D6 activity (20 to 40 nM) markedly inhibit estrogen-induced cell proliferation rates in the presence of ER?, whereas much higher endoxifen concentrations are needed when ER? is absent. Microarray analyses reveal substantial differences in the global gene expression profiles induced by endoxifen at low concentrations (40 nM) when comparing MCF7 cells which express ER? to those that do not. These profiles implicate pathways related to cell proliferation and apoptosis in mediating endoxifen effectiveness at these lower concentrations.Taken together, these data demonstrate that the presence of ER? enhances the sensitivity of breast cancer cells to the anti-estrogenic effects of endoxifen likely through the molecular actions of ER?/? heterodimers. These findings underscore the need to further elucidate the role of ER? in the biology and treatment of breast cancer and suggest that the importance of pharmacologic variation in endoxifen concentrations may differ according to ER? expression.

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Breast cancer anti-estrogen resistance 3 inhibits transforming growth factor ?/Smad signaling and associates with favorable breast cancer disease outcomes.

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Breast cancer anti-estrogen resistance 3 inhibits transforming growth factor β/Smad signaling and associates with favorable breast cancer disease outcomes.

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