Inhibition of β-catenin to overcome endocrine resistance in tamoxifen-resistant breast cancer cell line

Hye Sung Won, Kyung Mee Lee, Ju Eon Oh, Eun Mi Nam, Kyoung Eun Lee

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19 Scopus citations

Abstract

Background: The β-catenin signaling is important in cell growth and differentiation and is frequently dysregulated in various cancers. The most well-known mechanism of endocrine resistance is cross-talk between the estrogen receptor (ER) and other growth factor signaling, such as phosphatidylinositol-3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) signaling pathway. In the present study, we investigated whether β-catenin could be a potential target to overcome endocrine resistance in breast cancer. Methods: We established tamoxifen-resistant (TamR) cell line via long-term exposure of MCF-7 breast cancer cells to gradually increasing concentrations of tamoxifen. The levels of protein expression and mRNA transcripts were determined using western blot analysis and real-time quantitative PCR. The transcriptional activity of β-catenin was measured using luciferase activity assay. Results: TamR cells showed a mesenchymal phenotype, and exhibited a relatively decreased expression of ER and increased expression of human epidermal growth factor receptor 2 and the epidermal growth factor receptor. We confirmed that the expression and transcriptional activity of β-catenin were increased in TamR cells compared with control cells. The expression and transcriptional activity of β-catenin were inhibited by β-catenin small-molecule inhibitor, ICG-001 or β-catenin siRNA. The viability of TamR cells, which showed no change after treatment with tamoxifen, was reduced by ICG-001 or β-catenin siRNA. The combination of ICG-001 and mTOR inhibitor, rapamycin, yielded an additive effect on the inhibition of viability in TamR cells. Conclusion: These results suggest that β-catenin plays a role in tamoxifen-resistant breast cancer, and the inhibition of β-catenin may be a potential target in tamoxifen-resistant breast cancer.

Original languageEnglish
Article numbere0155983
JournalPLoS ONE
Volume11
Issue number5
DOIs
StatePublished - 1 May 2016

Bibliographical note

Publisher Copyright:
© 2016 Won et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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