scholarly journals The Estrogen Receptor α Signaling Pathway Controls Alternative Splicing in the Absence of Ligands in Breast Cancer Cells

Cancers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 6261
Author(s):  
Jamal Elhasnaoui ◽  
Giulio Ferrero ◽  
Valentina Miano ◽  
Santina Cutrupi ◽  
Michele De De Bortoli
Keyword(s):  
Breast Cancer ◽  
Estrogen Receptor ◽  
Alternative Splicing ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Disease Free Survival ◽  
Estrogen Receptor Α ◽  
Functional Enrichment ◽  
Expression Change ◽  
Mesenchymal Transition

Background: The transcriptional activity of estrogen receptor α (ERα) in breast cancer (BC) is extensively characterized. Our group has previously shown that ERα controls the expression of a number of genes in its unliganded form (apoERα), among which a large group of RNA-binding proteins (RBPs) encode genes, suggesting its role in the control of co- and post-transcriptional events. Methods: apoERα-mediated RNA processing events were characterized by the analysis of transcript usage and alternative splicing changes in an RNA-sequencing dataset from MCF-7 cells after siRNA-induced ERα downregulation. Results: ApoERα depletion induced an expression change of 681 RBPs, including 84 splicing factors involved in translation, ribonucleoprotein complex assembly, and 3′end processing. ApoERα depletion results in 758 isoform switching events with effects on 3′end length and the splicing of alternative cassette exons. The functional enrichment of these events shows that post-transcriptional regulation is part of the mechanisms by which apoERα controls epithelial-to-mesenchymal transition and BC cell proliferation. In primary BCs, the inclusion levels of the experimentally identified alternatively spliced exons are associated with overall and disease-free survival. Conclusion: Our data supports the role of apoERα in maintaining the luminal phenotype of BC cells by extensively regulating gene expression at the alternative splicing level.

scholarly journals An alternative splicing switch in FLNB promotes the mesenchymal cell state in human breast cancer

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Ji Li ◽  
Peter S Choi ◽  
Christine L Chaffer ◽  
Katherine Labella ◽  
Justin H Hwang ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Alternative Splicing ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Human Cancer ◽  
Mesenchymal Cell ◽  
Actin Binding ◽  
Mesenchymal Transition ◽  
Cell State ◽  
A Genome

Alternative splicing of mRNA precursors represents a key gene expression regulatory step and permits the generation of distinct protein products with diverse functions. In a genome-scale expression screen for inducers of the epithelial-to-mesenchymal transition (EMT), we found a striking enrichment of RNA-binding proteins. We validated that QKI and RBFOX1 were necessary and sufficient to induce an intermediate mesenchymal cell state and increased tumorigenicity. Using RNA-seq and eCLIP analysis, we found that QKI and RBFOX1 coordinately regulated the splicing and function of the actin-binding protein FLNB, which plays a causal role in the regulation of EMT. Specifically, the skipping of FLNB exon 30 induced EMT by releasing the FOXC1 transcription factor. Moreover, skipping of FLNB exon 30 is strongly associated with EMT gene signatures in basal-like breast cancer patient samples. These observations identify a specific dysregulation of splicing, which regulates tumor cell plasticity and is frequently observed in human cancer.

scholarly journals Identification of a Novel Estrogen Receptor-α Variant and Its Upstream Splicing Regulator

2010 ◽  
Vol 24 (5) ◽  
pp. 914-922 ◽  
Author(s):  
Kazufumi Ohshiro ◽  
Prakriti Mudvari ◽  
Qing-chang Meng ◽  
Suresh K. Rayala ◽  
Aysegul A. Sahin ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Estrogen Receptor ◽  
Alternative Splicing ◽  
Cyclin D1 ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Estrogen Receptor Α ◽  
Mrna Splicing ◽  
Human Breast ◽  
Alternative Mrna Splicing

Abstract Alternative splicing of precursor mRNA is a fundamental mechanism to generate multiple proteins from a single gene. Although constitutive and alternative mRNA splicing is temporally and spatially regulated, deregulation of mRNA splicing could cause development, progression, and metastasis of tumors. Through yeast two-hybrid screening of a human breast cDNA library using estrogen receptor-α (ERα) as bait, we identified a novel nuclear receptor box containing full-length protein, nuclear protein E3-3 (NPE3-3). Our results revealed that NPE3-3 associates with not only ERα but also with splicing factors, serine/arginine-rich protein (SRp)-30c, SRp40, and splicing factor SC-35, suggesting that NPE3-3 is likely to be involved in regulation of mRNA splicing. Accordingly, transient expression of NPE3-3 in cells resulted in expected splicing of the CD44 control minigene. We also discovered that NPE3-3-overexpressing clones produced a novel, previously unrecognized, alternatively spliced variant of ERα (termed ERαV), which had a molecular size of 37 kDa composed of only exons 1, 2, 7, and 8. ERαV was expressed and sequestered in the cytoplasm in MCF-7 cells stably overexpressing NPE3-3, suggesting its involvement in nongenomic hormone signaling. NPE3-3 clones exhibited up-regulation of ERK1/2 signaling, cyclin D1, and cathepsin D and enhanced tumor cell proliferation, migration, and tumorigenicity. Moreover, direct expression of the ERαV in breast cancer cells stimulated ERK1/2 up-regulation and cyclin D1 expression. We found that ERαV physically interacted with MAPK kinase (MEK)-1/2, and thus, an ERαV and MEK1/2 complex could lead to the activation of the ERK1/2 pathway. Interestingly, NPE3-3 was up-regulated in human breast tumors. These findings revealed a role for NPE3-3 in alternative splicing and suggest that ERα is a physiological target of NPE3-3, leading to a constitutive nongenomic signaling pathway in breast cancer cells.

Abstract PD15-07: Myc regulates alternative splicing through a network of RNA binding proteins in breast cancer

2021 ◽  
Author(s):  
Laura Urbanski ◽  
Brittany Angarola ◽  
Mattia Brugiolo ◽  
Marina Yurieva ◽  
Sunghee Park ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Alternative Splicing ◽  
Binding Proteins ◽  
Rna Binding ◽  
Rna Binding Proteins

scholarly journals Hypoxia-induced TGF-β–RBFOX2–ESRP1 axis regulates human MENA alternative splicing and promotes EMT in breast cancer

NAR Cancer ◽  
2020 ◽  
Vol 2 (3) ◽  
Author(s):  
Neha Ahuja ◽  
Cheemala Ashok ◽  
Subhashis Natua ◽  
Deepak Pant ◽  
Anna Cherian ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Alternative Splicing ◽  
Transcriptional Repression ◽  
Rna Binding ◽  
Epithelial Mesenchymal Transition ◽  
Global Changes ◽  
Invasion And Metastasis ◽  
New Paradigm ◽  
Mesenchymal Transition ◽  
Splicing Regulator

Abstract Hypoxic microenvironment heralds epithelial–mesenchymal transition (EMT), invasion and metastasis in solid tumors. Deregulation of alternative splicing (AS) of several cancer-associated genes has been instrumental in hypoxia-induced EMT. Our study in breast cancer unveils a previously unreported mechanism underlying hypoxia-mediated AS of hMENA, a crucial cytoskeleton remodeler during EMT. We report that the hypoxia-driven depletion of splicing regulator ESRP1 leads to skipping of hMENA exon 11a producing a pro-metastatic isoform, hMENAΔ11a. The transcriptional repression of ESRP1 is mediated by SLUG, which gets stimulated via hypoxia-driven TGF-β signaling. Interestingly, RBFOX2, an otherwise RNA-binding protein, is also found to transcriptionally repress ESRP1 while interacting with SLUG. Similar to SLUG, RBFOX2 gets upregulated under hypoxia via TGF-β signaling. Notably, we found that the exosomal delivery of TGF-β contributes to the elevation of TGF-β signaling under hypoxia. Moreover, our results show that in addition to hMENA, hypoxia-induced TGF-β signaling contributes to global changes in AS of genes associated with EMT. Overall, our findings reveal a new paradigm of hypoxia-driven AS regulation of hMENA and insinuate important implications in therapeutics targeting EMT.

scholarly journals Expression of ER-α36, a Novel Variant of Estrogen Receptor α, and Resistance to Tamoxifen Treatment in Breast Cancer

2009 ◽  
Vol 27 (21) ◽  
pp. 3423-3429 ◽  
Author(s):  
Liang Shi ◽  
Bin Dong ◽  
Zhongwu Li ◽  
Yunwei Lu ◽  
Tao Ouyang ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Estrogen Receptor ◽  
Tamoxifen Resistance ◽  
Disease Free Survival ◽  
Estrogen Receptor Α ◽  
Tamoxifen Treatment ◽  
Free Survival ◽  
Novel Variant ◽  
Disease Free ◽  
Disease Specific

Purpose Recently, a 36-kDa variant of estrogen receptor α (ER-α66), ER-α36, has been identified and cloned. ER-α36 predominantly localizes on the plasma membrane and in the cytoplasm and mediates a membrane-initiated “nongenomic” signaling pathway. Here, we investigate the association between ER-α36 expression and tamoxifen resistance in patients with breast cancer. Patients and Methods ER-α36 protein expression in tumors from 896 women (two independent cohorts, 1 and 2) with operable primary breast cancer was assessed using an immunohistochemistry assay. Results In the first cohort of 710 consecutive patients, overexpression of ER-α36 was associated with poorer disease-free survival (DFS) and disease-specific survival (DSS) in patients with ER-α66–positive tumors who received tamoxifen treatment (chemotherapy plus tamoxifen or tamoxifen alone, n = 307). In contrast, ER-α36 was not associated with survival in patients with ER-α66–positive tumors who did not receive tamoxifen (chemotherapy alone, n = 129) and in patients with ER-α66–negative tumors whether they received tamoxifen (n = 73) or not (n = 149). In the second cohort of 186 patients who only received tamoxifen as adjuvant therapy, overexpression of ER-α36 was significantly associated with poorer DFS and DSS in 156 ER-α66–positive patients from this cohort, and ER-α36 remained an independent unfavorable factor for both DFS and DSS in these 156 patients by a multivariate analysis (DFS: hazard ratio [HR] = 5.47; 95% CI, 1.81 to 16.51; P =. 003; DSS: HR = 13.97; 95% CI, 1.58 to 123.53; P = .018). Conclusion Women with ER-α66–positive tumors that also express high levels of ER-α36 are less likely to benefit from tamoxifen treatment.

scholarly journals Estrogen Receptor α Mediates Doxorubicin Sensitivity in Breast Cancer Cells by Regulating E-Cadherin

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaoqing Wan ◽  
Jiaxin Hou ◽  
Shurong Liu ◽  
Yanli Zhang ◽  
Wenqing Li ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Estrogen Receptor ◽  
Cell Lines ◽  
Epithelial Mesenchymal Transition ◽  
Estrogen Receptor Α ◽  
Mesenchymal Transition ◽  
Mouse Breast Cancer ◽  
Mcf 7 ◽  
Positive Breast Cancer ◽  
E Cadherin

Anthracyclines resistance is commonly seen in patients with estrogen receptor α (ERα) positive breast cancer. Epithelial-mesenchymal transition (EMT), which is characterized with the loss of epithelial cell polarity, cell adhesion and acquisition of new invasive property, is considered as one of the mechanisms of chemotherapy-induced drug resistance. In order to identify factors that associated with doxorubicin resistance, we performed in vitro and in vivo experiments using human and mouse breast cancer cell lines with different ERα status. Cell survival experiments revealed that ERα-positive cells (MCF-7 and MCF-7/ADR cell lines), were less sensitive to doxorubicin than ERα-negative (MDA-MB-231, MDA-MB-468) cells, and mouse mammary carcinoma cells (4T-1). The expression of E-cadherin reduced in low-invasive ERα-positive MCF-7 cells after treatment with doxorubicin, indicating epithelial mesenchymal transition. In contrast, the expression of E-cadherin was upregulated in high-invasive ERα-negative cells, showing mesenchymal-epithelial transition (MET). Moreover, it was found that the growth inhibition of 4T-1 cells by doxorubicin was positively correlated with the expression of E-cadherin. In a mouse breast cancer xenograft model, E-cadherin was overexpressed in the primary tumor tissues of the doxorubicin-treated mice. In ERα-positive MCF-7 cells, doxorubicin treatment upregulated the expression of EMT-related transcription factors Snail and Twist, that regulate the expression of E-cadherin. Following overexpression of ERα in ERα-negative cells (MDA-MB-231 and MDA-MB-468), doxorubicin enhanced the upregulation of Snail and Twist, decreased expression of E-cadherin, and decreased the sensitivity of cells to doxorubicin. In contrast, inhibition of ERα activity increased the sensitivity to doxorubicin in ERα-positive MCF-7 cells. These data suggest that the regulation of Snail and/or Twist varies depends on different ERα status. Therefore, doxorubicin combined with anti-estrogen receptor α therapy could improve the treatment efficacy of doxorubicin in ERα-positive breast cancer.

scholarly journals MCPIP1-mediated NFIC alternative splicing inhibits proliferation of triple-negative breast cancer via cyclin D1-Rb-E2F1 axis

2021 ◽  
Vol 12 (4) ◽  
Author(s):  
Fengxia Chen ◽  
Qingqing Wang ◽  
Xiaoyan Yu ◽  
Ningning Yang ◽  
Yuan Wang ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Overall Survival ◽  
Alternative Splicing ◽  
Cyclin D1 ◽  
Triple Negative Breast Cancer ◽  
Triple Negative ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Negative Regulator ◽  
Breast Epithelial Cell

AbstractTriple-negative breast cancer (TNBC) is the most aggressive subtype with the worst prognosis and the highest metastatic and recurrence potential, which represents 15–20% of all breast cancers in Chinese females, and the 5-year overall survival rate is about 80% in Chinese women. Recently, emerging evidence suggested that aberrant alternative splicing (AS) plays a crucial role in tumorigenesis and progression. AS is generally controlled by AS-associated RNA binding proteins (RBPs). Monocyte chemotactic protein induced protein 1 (MCPIP1), a zinc finger RBP, functions as a tumor suppressor in many cancers. Here, we showed that MCPIP1 was downregulated in 80 TNBC tissues and five TNBC cell lines compared to adjacent paracancerous tissues and one human immortalized breast epithelial cell line, while its high expression levels were associated with increased overall survival in TNBC patients. We demonstrated that MCPIP1 overexpression dramatically suppressed cell cycle progression and proliferation of TNBC cells in vitro and repressed tumor growth in vivo. Mechanistically, MCPIP1 was first demonstrated to act as a splicing factor to regulate AS in TNBC cells. Furthermore, we demonstrated that MCPIP1 modulated NFIC AS to promote CTF5 synthesis, which acted as a negative regulator in TNBC cells. Subsequently, we showed that CTF5 participated in MCPIP1-mediated antiproliferative effect by transcriptionally repressing cyclin D1 expression, as well as downregulating its downstream signaling targets p-Rb and E2F1. Conclusively, our findings provided novel insights into the anti-oncogenic mechanism of MCPIP1, suggesting that MCPIP1 could serve as an alternative treatment target in TNBC.

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