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Analyse the differently expressed genes in tamoxifen resistant breast cancer cells

ABSTRACT: Tamoxifen resistance has been a major clinical problem and is accountable for relapse in about one third of ER positive breast cancer patients. Most of the recurrent patients will eventually receive chemotherapy. However, the chemosensitivity of these tamoxifen-resistant breast cancer patients has never been explored. In this study, we demonstrate that tamoxifen-resistant breast cancer cells express significantly more BARD1 and BRCA1, which results in the resistance to DNA-damaging chemotherapy including cisplatin and adriamycin , but not to paclitaxel. Silencing BARD1 or BRCA1 expression or inhibition of BRCA1 phosphorylation by Dinaciclib restored the sensitivity to cisplatin in tamoxifen-resistant cells. In addition, we identified that activated PI3K/AKT pathway in tamoxifen-resistant cells was responsible for the upregulation of BARD1 and BRCA1. PI3K inhibitors, BKM120 and BYL719, decreased the expression of BARD1 and BRCA1 in tamoxifen-resistant cells and re-sensitized them to cisplatin both in vitro and in xenografted mice. Higher BARD1 and BRCA1 expression was associated with poor prognosis of early breast cancer patients, especially the ones received radiotherapy, indicating the potential use of PI3K inhibitors to reverse chemoresistance and radioresistance in ER positive breast cancer patients.

ORGANISM(S): Homo sapiens

PROVIDER: GSE111926 | GEO | 2021/03/15

REPOSITORIES: GEO

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Project description:Tamoxifen, an antagonist to estrogen receptor (ER), is a first line drug used in breast cancer treatment. However, this therapy is complicated by the fact that a substantial number of patients exhibit either de novo or acquired resistance. To characterize the signaling mechanisms underlying the resistance to tamoxifen, we established a tamoxifen-resistant cell line by treating the MCF7 breast cancer cell line with tamoxifen for over 6 months. We showed that this cell line exhibited resistance to tamoxifen both in vitro and in vivo. In order to quantify the phosphorylation alterations associated with tamoxifen resistance, we performed SILAC-based quantitative phosphoproteomic profiling on the resistant and vehicle-treated sensitive cell lines where we identified >5,600 unique phosphopeptides. We found phosphorylation levels of 1,529 peptides were increased (>2 fold) and 409 peptides were decreased (<0.5-fold) in tamoxifen resistant cells compared to tamoxifen sensitive cells. Gene set enrichment analysis revealed that focal adhesion pathway was the top enriched signaling pathway activated in tamoxifen resistant cells. We observed hyperphosphorylation of the focal adhesion kinases FAK1 and FAK2 in the tamoxifen resistant cells. Of note, FAK2 was not only hyperphosphorylated but also transcriptionally upregulated in tamoxifen resistant cells. Suppression of FAK2 by specific siRNA knockdown could sensitize the resistant cells to the treatment of tamoxifen. We further showed that inhibiting FAK activity using the small molecule inhibitor PF562271 repressed cellular proliferation in vitro and tumor formation in vivo. More importantly, our survival analysis revealed that high expression of FAK2 significantly associated with short metastasis-free survival of ER-positive breast cancer patients treated with tamoxifen-based hormone therapy. Our studies suggest that FAK2 is a great potential target for the development of therapy for the treatment of hormone refractory breast cancers.

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Analyse the differently expressed genes in tamoxifen resistant breast cancer cells

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