scholarly journals Induction of multidrug resistance associated protein 2 in tamoxifen-resistant breast cancer cells

2007 ◽  
Vol 14 (2) ◽  
pp. 293-303 ◽  
Author(s):  
Hoo Kyun Choi ◽  
Jin Won Yang ◽  
Sang Hee Roh ◽  
Chang Yeob Han ◽  
Keon Wook Kang
Keyword(s):  
Breast Cancer ◽  
Multidrug Resistance ◽  
Cancer Cells ◽  
Transcriptional Activation ◽  
Breast Cancer Cells ◽  
Pregnane X Receptor ◽  
Pi3 Kinase ◽  
Gene Promoters ◽  
Breast Cancer Patients ◽  
Mcf 7

Acquired resistance to tamoxifen (TAM) is a serious therapeutic problem in breast cancer patients. The transition from chemotherapy-responsive breast cancer cells to chemotherapy-resistant cancer cells is mainly accompanied by the increased expression of multidrug resistance-associated proteins (MRPs). In this study, it was found that TAM-resistant MCF-7 (TAMR-MCF-7) cells expressed higher levels of MRP2 than control MCF-7 cells. Molecular analyses using MRP2 gene promoters supported the involvement of the pregnane X receptor (PXR) in MRP2 overexpression in TAMR-MCF-7 cells. Although CCAAT/enhancer-binding protein β was overexpressed continuously in TAMR-MCF-7 cells, this might not be responsible for the transcriptional activation of the MRP2 gene. In addition, the basal activities of phosphatidylinositol 3-kinase (PI3-kinase) were higher in the TAMR-MCF-7 cells than in the control cells. The inhibition of PI3-kinase significantly reduced both the PXR activity and MRP2 expression in TAMR-MCF-7 cells. Overall, MRP2 induction plays a role in the additional acquisition of chemotherapy resistance in TAM-resistant breast cancer.

scholarly journals ERβ-induced MFN2 inhibits the migration and invasiveness of breast cancer cells by inhibiting the P-AKT signaling pathway

2020 ◽  
Author(s):  
Mengyu Wei ◽  
Jun Hao ◽  
Xiaomei Liao ◽  
Yinfeng Liu ◽  
Ruihuan Fu ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Breast Cancer Cells ◽  
Akt Pathway ◽  
Cancer Cell Migration ◽  
Breast Cancer Patients ◽  
Human Breast ◽  
Mcf 7

Abstract Background Mitofusin 2 (MFN2) is localized on the outer membrane of mitochondria and is closely related to the migration of malignant tumor cells. Estrogen receptor β (ERβ) plays an anticancer role in breast cancer. Our previous experiments showed that ERβ can induce MFN2 expression, which then inhibits breast cancer cell migration. However, the exact mechanism by which ERβ-induced MFN2 inhibits breast cancer cell migration is unknown. Methods In this study, immunohistochemistry was first used to detect the expression of MFN2 in breast cancer tissues, and its relationship with the clinicopathological characteristics and prognosis of breast cancer patients was analyzed. MCF-7 and MDA-MB-231 cells were transfected with ERβ and MFN2 knockdown or expression plasmids. Western blot was used to detect the effects of ERβ on MFN2 and MFN2 on P-AKT473 and MMP2; the P-AKT pathway inhibitor LY294002 was administered to cells transfected with MFN2 knockdown plasmids, Western blot, immunocytofluorescence, and a wound healing assay revealed the effect of MFN2 on its downstream signaling pathway and the migration of breast cancer cells. Results This study found that the expression of MFN2 is related to the molecular type and prognosis of breast cancer patients ( P <0.05). The positive expression rate of MFN2 in triple-negative breast cancer was significantly lower than that in the HER2 + and luminal types. However, MFN2 expression was unrelated to age, tumor size, lymph node metastasis, TNM stage, histological type and grade ( P >0.05); ERβ positively regulated MFN2 expression and reduced the migration of both MCF-7 and MDA-MB-231 cells, while MFN2 knockdown increased the expression of P-AKT473 and MMP2. In contrast, the overexpression of MFN2 inhibited the expression of P-AKT473 and MMP2. These results showed that in MFN2 knockdown cells treated with LY294002, P-AKT473 and MMP2 expression levels were reversed. The reversal of P-AKT473 and MMP2 expression levels inhibits the invasiveness of human breast cancer cells. Conclusion MFN2 is related to the molecular subtype and prognosis of breast cancer. In human breast cancer MCF-7 and MDA-MB-231 cells, ERβ-induced MFN2 can inhibit the P-AKT pathway, which inhibits the invasiveness and migration of both breast cancer cell lines.

scholarly journals miR-200 affects tamoxifen resistance in breast cancer cells through regulation of MYB

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yu Gao ◽  
Wenzhi Zhang ◽  
Chengwen Liu ◽  
Guanghua Li
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Tamoxifen Resistance ◽  
Breast Cancer Patients ◽  
Over Expression ◽  
Er Positive ◽  
Emt Markers ◽  
Mcf 7 ◽  
Positive Breast Cancer

AbstractResistance to tamoxifen is a major clinical challenge. Research in recent years has identified epigenetic changes as mediated by dysregulated miRNAs that can possibly play a role in resistance to tamoxifen in breast cancer patients expressing estrogen receptor (ER). We report here elevated levels of EMT markers (vimentin and ZEB1/2) and reduced levels of EMT-regulating miR-200 (miR-200b and miR-200c) in ER-positive breast cancer cells, MCF-7, that were resistant to tamoxifen, in contrast with the naïve parental MCF-7 cells that were sensitive to tamoxifen. Further, we established regulation of c-MYB by miR-200 in our experimental model. C-MYB was up-regulated in tamoxifen resistant cells and its silencing significantly decreased resistance to tamoxifen and the EMT markers. Forced over-expression of miR-200b/c reduced c-MYB whereas reduced expression of miR-200b/c resulted in increased c-MYB We further confirmed the results in other ER-positive breast cancer cells T47D cells where forced over-expression of c-MYB resulted in induction of EMT and significantly increased resistance to tamoxifen. Thus, we identify a novel mechanism of tamoxifen resistance in breast tumor microenvironment that involves miR-200-MYB signaling.

scholarly journals 4sUDRB-sequencing for genome-wide transcription bursting quantification in breast cancer cells

2020 ◽  
Author(s):  
William F. Beckman ◽  
Miguel Ángel Lermo Jiménez ◽  
Perry D. Moerland ◽  
Hans V. Westerhoff ◽  
Pernette J. Verschure
Keyword(s):  
Breast Cancer ◽  
Gene Expression ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Burst Size ◽  
Mrna Levels ◽  
Gene Promoters ◽  
Genome Wide ◽  
A Genome ◽  
Mcf 7

AbstractEpigenetics maintains cell-identity specific gene-expression patterns. However, within a population of isogenic cells of the same identity, a substantial variability in gene expression and responsiveness is still observed. Transcription bursting is a substantial source of this gene-expression variability or ‘noise’, contributing to phenotypic heterogeneity and potentially driving both physiological and pathological processes such as differentiation or tumorigenesis and drug resistance. Identification of transcription-bursting dynamics at a genome-wide scale has been restricted to inferring bursts in mRNA production computationally from the heterogeneity of mRNA levels in single cell transcriptomic data. Systematic characterisation of the genomic and epigenetic chromatin context of genes with defined transcription bursting behaviour has been incomplete. Here, we measured the bursting of transcription itself by genome-wide nascent RNA sequencing of breast cancer MCF-7 cells upon synchronisation of transcription with a transcription elongation inhibitor and by calibration using live cell imaging of nascent PP7-tagged GREB1 transcription. Comparing across the entire genome, we find transcription bursting to be ubiquitous, with burst sizes of up to 160 transcripts. Transcription bursting attributes ~85% to a trend in the variation in steady state gene expression between genes, whereas both burst frequency and nascent transcript degradation attribute minimally. Individual genes deviate strongly from this trend and engage both in anomalous burst size and frequency. We find that the presence of the TATA box or Inr sequence within gene promoters significantly predicts a larger burst size, as do promoter-associated YY1 and E2F1 transcription-factor binding motifs. Enrichment of the transcription start site with epigenetic marks such as H3K79me2 and H3Kl4ac is also strongly associated with the transcription burst size. Finally, we show that in these MCF-7 breast-cancer cells, genes with a larger transcription burst size exhibit a larger immediate transcriptional response following endocrine drug treatment. Our genome-wide transcription-bursting analysis method paves the way to elucidate the dynamic role of epigenetic regulation on dynamic transcription in pathophysiology.

Angiotensin II/angiotensin II type I receptor (AT1R) signaling promotes MCF-7 breast cancer cells survival via PI3-kinase/Akt pathway

2010 ◽  
Vol 225 (1) ◽  
pp. 168-173 ◽  
Author(s):  
Yanbin Zhao ◽  
Xuesong Chen ◽  
Li Cai ◽  
Yanmei Yang ◽  
Guangjie Sui ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Angiotensin Ii ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Pi3 Kinase ◽  
Akt Pathway ◽  
Type I ◽  
Mcf 7
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