MEK activity controls IL-8 expression in tamoxifen-resistant MCF-7 breast cancer cells

Abstract Background The mechanisms of endocrine resistance are complex, and deregulation of several oncogenic signalling pathways has been proposed. We aimed to investigate the role of the EGFR and Src-mediated STAT3 signalling pathway in tamoxifen-resistant breast cancer cells. Methods The ER-positive luminal breast cancer cell lines, MCF-7 and T47D, were used. We have established an MCF-7-derived tamoxifen-resistant cell line (TamR) by long-term culture of MCF-7 cells with 4-hydroxytamoxifen. Cell viability was determined using an MTT assay, and protein expression levels were determined using western blot. Cell cycle and annexin V staining were analysed using flow cytometry. Results TamR cells showed decreased expression of estrogen receptor and increased expression of EGFR. TamR cells showed an acceleration of the G1 to S phase transition. The protein expression levels of phosphorylated Src, EGFR (Y845), and STAT3 was increased in TamR cells, while phosphorylated Akt was decreased. The expression of p-STAT3 was enhanced according to exposure time of tamoxifen in T47D cells, suggesting that activation of STAT3 can cause tamoxifen resistance in ER-positive breast cancer cells. Both dasatinib (Src inhibitor) and stattic (STAT3 inhibitor) inhibited cell proliferation and induced apoptosis in TamR cells. However, stattic showed a much stronger effect than dasatinib. Knockdown of STAT3 expression by siRNA had no effect on sensitivity to tamoxifen in MCF-7 cells, while that enhanced sensitivity to tamoxifen in TamR cells. There was not a significant synergistic effect of dasatinib and stattic on cell survival. TamR cells have low nuclear p21(Cip1) expression compared to MCF-7 cells and inhibition of STAT3 increased the expression of nuclear p21(Cip1) in TamR cells. Conclusions The EGFR and Src-mediated STAT3 signalling pathway is activated in TamR cells, and inhibition of STAT3 may be a potential target in tamoxifen-resistant breast cancer. An increase in nuclear p21(Cip1) may be a key step in STAT3 inhibitor-induced cell death in TamR cells.

Download Full-text

Differential Response to α-Oxoaldehydes in Tamoxifen Resistant MCF-7 Breast Cancer Cells

PLoS ONE ◽

10.1371/journal.pone.0101473 ◽

2014 ◽

Vol 9 (7) ◽

pp. e101473 ◽

Cited By ~ 14

Author(s):

Norbert Nass ◽

Hans-Jürgen Brömme ◽

Roland Hartig ◽

Sevil Korkmaz ◽

Saadettin Sel ◽

...

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Differential Response ◽

Tamoxifen Resistant ◽

Mcf 7

Download Full-text

Activated Farnesoid X Receptor Inhibits Growth of Tamoxifen-Resistant MCF-7 Breast Cancer Cells, through Down-Regulation of HER2 Expression.

10.1210/endo-meetings.2010.part3.p2.p3-58 ◽

2010 ◽

pp. P3-58-P3-58

Author(s):

C Giordano ◽

D Vizza ◽

S Panza ◽

I Barone ◽

D Bonofiglio ◽

...

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Farnesoid X Receptor ◽

Her2 Expression ◽

Down Regulation ◽

Tamoxifen Resistant ◽

Mcf 7

Download Full-text

A new synthetic HDAC inhibitor, MHY218, induces apoptosis or autophagy-related cell death in tamoxifen-resistant MCF-7 breast cancer cells

Investigational New Drugs ◽

10.1007/s10637-011-9752-z ◽

2011 ◽

Vol 30 (5) ◽

pp. 1887-1898 ◽

Cited By ~ 15

Author(s):

Ji Hye Park ◽

Mee Young Ahn ◽

Tae Hyung Kim ◽

Sungpill Yoon ◽

Keon Wook Kang ◽

...

Keyword(s):

Breast Cancer ◽

Cell Death ◽

Cancer Cells ◽

Hdac Inhibitor ◽

Breast Cancer Cells ◽

Related Cell ◽

Tamoxifen Resistant ◽

Mcf 7

Download Full-text

Narciclasine Targets STAT3 via Distinct Mechanisms in Tamoxifen-Resistant Breast Cancer Cells

10.21203/rs.3.rs-680769/v1 ◽

2021 ◽

Author(s):

Chao Lv ◽

Yun Huang ◽

Rui Huang ◽

Qun Wang ◽

Hongwei Zhang ◽

...

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Sh2 Domain ◽

Breast Cancers ◽

Stat3 Phosphorylation ◽

Er Positive ◽

Tamoxifen Resistant ◽

Mcf 7 ◽

Positive Breast Cancer

Abstract Background: Signal transducer and activator of transcription 3 (STAT3) is constitutively activated in multiple malignant tumors. Compared with regular estrogen receptor (ER)-positive breast cancers, the patients with tamoxifen-resistant breast cancers often exhibit higher level of STAT3 phosphorylation. Narciclasine (Nar) possesses strong inhibiting effects against a variety of cancer cells, however, the underlying antitumor target(s)/mechanism(s) remains barely understood. Methods: Targets prediction of narciclasine was performed by combining connectivity map (CMAP) and drug affinity responsive target stability (DARTS) strategy. Molecular and biochemical methods were used to elucidate the distinct mechanisms of narciclasine targeting STAT3. The narciclasine nano-delivery system was synthesized by thin film hydration method. Xenograft models were established to determine antitumor activity of narciclasine and its liposome in vivo.Results: In this study, we successfully identified the STAT3 was the direct target of Nar through the combination strategies of CMAP and DARTS. In ER-positive breast cancer cells, Nar could suppress phosphorylation, activation, dimerization, and nuclear translocation of STAT3 by directly binding with the STAT3 SH2 domain. Additionally, Nar could also specifically promote total STAT3 degradation via proteasome pathway and reduce the STAT3 protein stability in tamoxifen-resistant breast cancer cells (MCF-7/TR). This distinct mechanism of Nar targeting STAT3 was mainly attributed to the various levels of reactive oxygen species (ROS) in regular and tamoxifen-resistant ER-positive breast cancer cells. Meanwhile, Nar loaded nanoparticles could markedly decrease the protein levels of STAT3 in tumor sites, resulting in significant MCF-7/TR xenograft tumor regression without obvious toxicity. Conclusions: Our findings successfully highlight the STAT3 as the direct therapeutic target of Nar in ER-positive breast cancer cells, especially Nar leaded STAT3 degradation as a promising strategy for the tamoxifen-resistant breast cancer treatment.

Download Full-text

Induced Tamoxifen Resistance is Mediated by Increased Methylation of E-Cadherin in Estrogen Receptor-Expressing Breast Cancer Cells

Scientific Reports ◽

10.1038/s41598-019-50749-1 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Qi Wang ◽

Melisa Gun ◽

Xing-yu Hong

Keyword(s):

Breast Cancer ◽

Estrogen Receptor ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Epithelial To Mesenchymal Transition ◽

Breast Cancers ◽

Mesenchymal Transition ◽

Tamoxifen Resistant ◽

Mcf 7 ◽

E Cadherin

Abstract Estrogen receptor-positive breast cancers are treated with tamoxifen, a drug that competitively inhibits the binding of estrogen to its receptor. Resistance to tamoxifen is a major hurdle in effective management of target breast cancer patient population. A number of dynamic changes within the tumor microenvironment, including the phenomenon of epithelial to mesenchymal transition (EMT), determine the response to endocrine therapy. EMT is marked by silencing or suppression of epithelial marker, E-Cadherin and we found significantly down-regulated E-Cadherin, among other epithelial markers, and a significantly up-regulated mesenchymal marker, Twist, among other mesenchymal markers, in a model system that comprised of tamoxifen sensitive MCF-7 cells and their tamoxifen-resistant counterparts, MCF-7-TAM, developed by chronic and escalating exposure of parental cells to tamoxifen. Further, E-cadherin, but not Twist, was differentially expressed in MCF-7-TAM cells because of differential methylation. Treatment with demethylating agent 5-azacytidine increased the expression of E-cadherin thus verifying a role of methylation in its silencing and, moreover, 5-azacytidine treatment also re-sensitized MCF-7-TAM cells to tamoxifen, as evaluated by assays for viability, apoptosis and migration potential. The 5-azacytidine effects were similar to effects of E-cadherin overexpression in MCF-7-TAM cells. This work describes novel mechanism of E-cadherin downregulation in tamoxifen resistant breast cancer cells. Further studies are needed to exploit this information for betterment of breast cancer therapy.

Download Full-text

Heregulin β1 drives gefitinib-resistant growth and invasion in tamoxifen-resistant MCF-7 breast cancer cells

Breast Cancer Research ◽

10.1186/bcr1754 ◽

2007 ◽

Vol 9 (4) ◽

Cited By ~ 40

Author(s):

Iain R Hutcheson ◽

Janice M Knowlden ◽

Steve E Hiscox ◽

Denise Barrow ◽

Julia MW Gee ◽

...

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Tamoxifen Resistant ◽

Mcf 7

Download Full-text

miR-449a Suppresses Tamoxifen Resistance in Human Breast Cancer Cells by Targeting ADAM22

Cellular Physiology and Biochemistry ◽

10.1159/000493964 ◽

2018 ◽

Vol 50 (1) ◽

pp. 136-149 ◽

Cited By ~ 13

Author(s):

Jun Li ◽

Mingjie Lu ◽

Jiao Jin ◽

Xiyi Lu ◽

Tongpeng Xu ◽

...

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Tamoxifen Resistance ◽

Luciferase Assay ◽

Protein Protein Interaction ◽

Er Positive ◽

Tamoxifen Resistant ◽

Mcf 7 ◽

Positive Breast Cancer

Background/Aims: Most of estrogen receptor positive breast cancer patients respond well initially to endocrine therapies, but often develop resistance during treatment with selective estrogen receptor modulators (SERMs) such as tamoxifen. Altered expression and functions of microRNAs (miRNAs) have been reportedly associated with tamoxifen resistance. Thus, it is necessary to further elucidate the function and mechanism of miRNAs in tamoxifen resistance. Methods: Tamoxifen sensitivity was validated by using Cell Counting Kit-8 in tamoxifen-sensitive breast cancer cells (MCF-7, T47D) and tamoxifen-resistant cells (MCF-7/TAM, T47D/ TAM). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the expression level of miR-449a in tamoxifen-sensitive/-resistant cells and patient serums. Dual-luciferase assay was used to identify the binding of miR-449a and predicted gene ADAM22. The expression level of ADAM22 was determined by qRT-PCR and western blotting in miR-449a +/- breast cancer cells. Subsequently, rescue experiments were carried out to identify the function of ADAM22 in miR-449a-reduced tamoxifen resistance. Finally, Gene ontology (GO) and Protein-protein interaction analyses were performed to evaluate the potential mechanisms of ADAM22 in regulating tamoxifen resistance. Results: MiR-449a levels were downregulated significantly in tamoxifen-resistant breast cancer cells when compared with their parental cells, as well as in clinical breast cancer serum samples. Overexpression of miR-449a re-sensitized the tamoxifen-resistant breast cancer cells, while inhibition of miR-449a conferred tamoxifen resistance in parental cells. Luciferase assay identified ADAM22 as a direct target gene of miR-449a. Additionally, silencing of ADAM22 could reverse tamoxifen resistance induced by miR-449a inhibition in ER-positive breast cancer cells. GO analysis results showed ADAM22 was mainly enriched in the biological processes of cell adhesion, cell differentiation, gliogenesis and so on. Protein-protein interaction analyses appeared that ADAM22 might regulate tamoxifen resistance through PPARG, LGI1, KRAS and LYN. Conclusion: Decreased miR-449a causes the upregulation of ADAM22, which induces tamoxifen resistance of breast cancer cells. These results suggest that miR-449a, functioning by targeting ADAM22, contributes to the mechanisms underlying breast cancer endocrine resistance, which may provide a potential therapeutic strategy in ER-positive breast cancers.

Download Full-text