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Expression profile of the endocrine therapy sensitive breast cancer cells MCF7 depleted of PBX1

ABSTRACT: Effect of PBX1 silencing on global gene expression of MCF7 cells stimulated with EGF. The hypothesis tested was that PBX1 is essential for EGF signaling in ERa positive breast cancer cells. Total RNA was obtained from MCF7 cells treated with siRNA directed at PBX1 or an siControl for 72h. Cells were then stimulated with estradiol (EGF) for 3h prior to RNA extraction.

ORGANISM(S): Homo sapiens

SUBMITTER: Magnani L

PROVIDER: S-ECPF-GEOD-39417 | biostudies-other | 2013 Apr

REPOSITORIES: biostudies-other

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Project description:IntroductionResistance to anti-estrogen therapies is a major cause of disease relapse and mortality in estrogen receptor alpha (ERα)-positive breast cancers. Tamoxifen or estrogen withdrawal increases the dependence of breast cancer cells on Notch signalling. Here, we investigated the contribution of Nicastrin and Notch signalling in endocrine-resistant breast cancer cells.MethodsWe used two models of endocrine therapies resistant (ETR) breast cancer: tamoxifen-resistant (TamR) and long-term estrogen-deprived (LTED) MCF7 cells. We evaluated the migratory and invasive capacity of these cells by Transwell assays. Expression of epithelial to mesenchymal transition (EMT) regulators as well as Notch receptors and targets were evaluated by real-time PCR and western blot analysis. Moreover, we tested in vitro anti-Nicastrin monoclonal antibodies (mAbs) and gamma secretase inhibitors (GSIs) as potential EMT reversal therapeutic agents. Finally, we generated stable Nicastrin overexpessing MCF7 cells and evaluated their EMT features and response to tamoxifen.ResultsWe found that ETR cells acquired an epithelial to mesenchymal transition (EMT) phenotype and displayed increased levels of Nicastrin and Notch targets. Interestingly, we detected higher level of Notch4 but lower levels of Notch1 and Notch2 suggesting a switch to signalling through different Notch receptors after acquisition of resistance. Anti-Nicastrin monoclonal antibodies and the GSI PF03084014 were effective in blocking the Nicastrin/Notch4 axis and partially inhibiting the EMT process. As a result of this, cell migration and invasion were attenuated and the stem cell-like population was significantly reduced. Genetic silencing of Nicastrin and Notch4 led to equivalent effects. Finally, stable overexpression of Nicastrin was sufficient to make MCF7 unresponsive to tamoxifen by Notch4 activation.ConclusionsETR cells express high levels of Nicastrin and Notch4, whose activation ultimately drives invasive behaviour. Anti-Nicastrin mAbs and GSI PF03084014 attenuate expression of EMT molecules reducing cellular invasiveness. Nicastrin overexpression per se induces tamoxifen resistance linked to acquisition of EMT phenotype. Our finding suggest that targeting Nicastrin and/or Notch4 warrants further clinical evaluation as valid therapeutic strategies in endocrine-resistant breast cancer.

Project description:BackgroundMicroRNAs (miRs) regulate gene expression through translation inhibition of target mRNAs. One of the most promising approaches for cancer therapy is through mimicking or antagonizing the action of miRs. In this report, we analyzed the miRnome profile of several human breast cancer cell lines to determine the influence of estrogen receptor (ER) silencing previously shown to result in epithelial to mesenchymal transition (EMT) and enhanced tumor invasion.MethodsMicroRNA extracted from MDA-MB-231 (de novo ER-) and ER-silenced (acquired ER-) pII and IM-26 or ER-expressing (YS1.2) siRNA transfected derivatives of MCF7 cells was deep sequenced on Illumina NextSeq500. Respective miRnomes were compared with edgeR package in R and Venny2.1 and target prediction performed with miRTarBase. Mimics and inhibitors of selected differentially expressed miRs associated with EMT mediators (miR-200c-3p targeting ZEB1, miR-449a targeting δ-catenin and miR-29a-3p) were transfected into pII cells and mRNA targets, as well as E-cadherin and keratin 19 (epithelial and mesenchymal markers respectively) were measured using taqman PCR.ResultsEach cell line expressed about 20% of the total known human miRnome; There was a high degree of similarity between the 3 tested ER-lines. Out of these expressed miRs, 50-60% were significantly differentially expressed between ER- and ER + lines. Transfection of miR-200c-3p mimic into pII cells down regulated ZEB1 and vimentin, and increased E-cadherin and keratin 19 with accompanying morphological changes, and reduced cell motility, reflecting a reversal back into an epithelial phenotype. On the other hand, transfecting pII with miR-449a inhibitor reduced cell invasion but did not induce EMT. Transfecting pII cell line with the mimic or inhibitor of miR-29a-3p showed no change in EMT markers or cell invasion suggesting that the EMT induced by loss of ER function can be reversed by blocking some but not just any random EMT-associated genes.ConclusionsThese data suggest that differences in miR expression can be exploited not only as mediators (using mimics) and targets (using miR antagonists) for general cancer therapies aimed at regulating either individual or multiple mRNAs, but also to re-sensitize endocrine resistant breast cancers by turning them back into a type that will be susceptible to endocrine agents.

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Expression profile of the endocrine therapy sensitive breast cancer cells MCF7 depleted of PBX1

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