Hypoxia and ERα Transcriptional Crosstalk Is Associated with Endocrine Resistance in Breast Cancer
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PROVIDER: PRJNA438527 | ENA |
REPOSITORIES: ENA
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Project description:Estrogen receptor-alpha (ERα) is the driving transcription factor in 70% of breast cancers and its activity is associated with hormone dependent tumor cell proliferation and survival. Given the recurrence of hormone resistant relapses, understanding the etiological factors fueling resistance is of major clinical interest. Hypoxia, a frequent feature of the solid tumor microenvironment, has been described to promote endocrine resistance by triggering ERα down-regulation in both in vitro and in vivo models. Yet, the consequences of hypoxia on ERα genomic activity remain largely elusive. In the present study, transcriptomic analysis shows that hypoxia regulates a fraction of ERα target genes, underlying an important regulatory overlap between hypoxic and estrogenic signaling. This gene expression reprogramming is associated with a massive reor-ganization of ERα cistrome, highlighted by a massive loss of ERα binding sites. Profiling of en-hancer acetylation revealed a hormone independent enhancer activation at the vicinity of genes harboring hypoxia inducible factor (HIFα) binding sites, the major transcription factors governing hypoxic adaptation. This activation counterbalances the loss of ERα and sustains hor-mone-independent gene expression. We describe hypoxia in luminal ERα (+) breast cancer as a key factor interfering with endocrine therapies, associated with poor clinical prognosis in breast cancer patients.
2022-10-06 | GSE111914 | GEO
Project description:Background: The constitutively active ESR1 Y537S mutation is associated with endocrine therapy resistance and progression of metastatic breast cancer through its effects on estrogen receptor (ERα) gene regulatory functions. However, the complex relationship between ERα and the progesterone receptor (PR), known as ERα/PR crosstalk, has yet to be characterized in the context of the ERα Y537S mutation. This study aimed to elucidate the effects of the ERα Y537S mutation on ERα/PR crosstalk and resultant transcriptional activity and to identify potential therapeutic sensitivities that may offer novel treatment options to patients with endocrine therapy-resistant breast cancer. Methods: Proximity-based interactions of ERα and PR were assessed via proximity ligation assay (PLA). Gene expression in MCF7 and T47D cells was assessed by RNA-seq analysis with comparison to publicly available patient tumor transcriptome data. Chromatin immunoprecipitation (ChIP)-qPCR and immunoblotting were used to assess ERα/PR-associated gene expression and protein expression, respectively. Data were analyzed by ordinary two-way ANOVA (α = 0.05) with Tukey’s multiple comparisons tests. Results: Physical interaction of ERα and PR was increased in the context of the ERα Y537S mutation, including in the nucleus where this interaction may translate to altered gene expression. As such, more than 30 genes were differentially expressed in both patient tumor and cell line data (MCF7 and/or T47D cells) in the context of the ERα Y537S mutation compared to ERα WT. Of these, IRS1 stood out as a gene of interest, and ERα and PR occupancy at chromatin binding sites along IRS1 were uniquely altered in the context of ERα Y537S. Furthermore, siRNA knockdown of IRS1 or treatment with the IRS1 inhibitor NT-157 indicated a significant anti-proliferative effect of IRS1 depletion or inhibition in ERα Y537S cell lines. Conclusions: Previous research has characterized gene regulatory changes associated with the ERα Y537S mutation from the viewpoint of ERα. Here, we identify consequential changes to both ERα and PR transcription factor activity, including at chromatin binding sites for the signaling adaptor protein IRS1. We identified a significant dependence of ERα Y537S-expressing cells on IRS1 for proliferation, implicating IRS1 as a potential therapeutic target for restoring treatment sensitivity to patients with breast cancers harboring ERα Y537S mutations.
2023-09-20 | GSE243454 | GEO
Project description:Estrogen receptor-alpha (ERα) is the driving transcription factor in 70% of breast cancers and its activity is associated with hormone dependent tumor cell proliferation and survival. Given the recurrence of hormone resistant relapses, understanding the etiological factors fueling resistance is of major clinical interest. Hypoxia, a frequent feature of the solid tumor microenvironment, has been described to promote endocrine resistance by triggering ERα down-regulation in both in vitro and in vivo models. Yet, the consequences of hypoxia on ERα genomic activity remain largely elusive. In the present study, transcriptomic analysis shows that hypoxia regulates a fraction of ERα target genes, underlying an important regulatory overlap between hypoxic and estrogenic signaling. This gene expression reprogramming is associated with a massive reorganization of ERα cistrome, highlighted by a massive loss of ERα binding sites. Profiling of enhancer acetylation revealed a hormone independent enhancer activation at the vicinity of genes harboring hypoxia inducible factor (HIFα) binding sites, the major transcription factors governing hypoxic adaptation. This activation counterbalances the loss of ERα and sustains hormone-independent gene expression. We describe hypoxia in luminal ERα (+) breast cancer as a key factor interfering with endocrine therapies, associated with poor clinical prognosis in breast cancer patients.
| S-EPMC9563995 | biostudies-literature
Project description:Estrogen receptor alpha (ERα) expression in breast cancer is predictive of response to endocrine therapy, however resistance is common in ERα-positive tumors that over-express the growth factor receptor ERBB2. Even in the absence of estrogen, ERα can be activated by growth factors including the epidermal growth factor (EGF). EGF induces a transcriptional program distinct from estrogen, however the mechanism of the stimulus-specific response is unknown. Here we show that the EGF-induced ERα genomic targets, its cistrome, are distinct from those induced by estrogen in a process dependent on the transcription factor AP-1. The EGF-induced ERα cistrome specifically regulates genes found over-expressed in ERBB2-positive human breast cancers. This provides a potential molecular explanation for the endocrine therapy resistance seen in ERα-positive breast cancers that over-express ERBB2. These results suggest a central role for ERα in hormone-refractory breast tumors dependent on growth factor pathway activation and favors the development of therapeutic strategies completely antagonizing ERα as opposed to blocking its estrogen responsiveness alone.
2010-12-29 | GSE26081 | GEO
Project description:Abstract Several endocrine therapy (ET) resistance mechanisms for ER-positive (ER+) breast cancer (BC) have been proposed, including acquired ESR1 (ERα gene) mutations. The two most common ESR1 mutations are Y537S and D538G, which give rise to a constitutively active receptor with reduced affinity for agonists and antagonists. The discovery of new effective therapies remains a significant challenge in treating mutated ER+ BC. In this context, Poly (ADP-ribose) polymerase-1 (PARP-1) has captured considerable interest as a target for therapeutic inhibitors in specific types of cancers. Here, we report that crosstalk between PARP-1 and ERα may represent a novel therapeutic approach for ER+ BC. We have demonstrated that the up-regulation of PARP-1 expression, stimulated by 17-β estradiol (E2), was blocked by treatment with fulvestrant (Ful), a potent ERα antagonist, or ESR1 siRNA in ER+ MCF7 and T47D BC cell models that express both wild type ERα and the Y537S mutation, indicating that ERα regulates the expression of PARP-1. In addition, ERα-mediated transcriptional activity depended on PARP-1 activity in these models, as confirmed by ERα target gene expression and ERE reporter gene analyses +/- niraparib (Nira). Notably, PARP-1 modulates the estrogen-dependent genomic binding of ERα and FoxA1, which play a crucial role in the proliferation of ER+ BC. We also showed that PARP-1 inhibition prevented proliferation and cell cycle activities of ERα WT and ERα Y537S cells upon ERα activation. In vivo, Nira and lasofoxifene (Laso), an ERα antagonist, significantly reduced primary tumor growth versus vehicle, both as single agents and in combination. Moreover, RNA-seq analyses demonstrated the downregulation of ERα signaling in the mammary glands of mice treated with Nira versus Vehicle. Our results provide novel insights into the molecular events through which PARP-1 may serve as a more comprehensive therapeutic approach to target ET BC resistance in women with advanced ER+ BC.
2024-09-30 | GSE277883 | GEO
Project description:ERα/PR crosstalk is altered in the context of the ERα Y537S mutation and contributes to endocrine therapy-resistant tumor proliferation
| PRJNA1018519 | ENA
Project description:Resistance to endocrine therapy represents a major threat to patients with estrogen receptor α positive (ERα+) breast cancer. The development of resistance is mainly through activating E2F signaling. However, the mechanisms that govern E2F1 activity in these resistant cells remain poorly understood. Here, we identify Actin Gamma 1 Pseudogene 25 (AGPG) as a lncRNA whose expression is driven by epigenomic activation of enhancer in endocrine resistant breast cancer cells. High expression of AGPG is associated with poor survival of ERα+ breast cancer, especially in patients receiving endocrine therapy. Stable knockdown and overexpression of AGPG demonstrate that AGPG promotes endocrine resistance, cell cycle progression, cell proliferation in vitro and in vivo. AGPG functions by direct binding purine rich element binding protein α (PURα), a transcription factor repressing E2F1 signaling and sensitized ERα+ breast cancer cells to endocrine therapy. Via binding to the region responsible for PURα/E2F1 interaction in PURα protein, AGPG releases E2F1 from PURα, leading to activation of E2F1 signaling in ERα+ breast cancer cells. Clinically, E2F1 target genes are strongly correlated with AGPG and PURα expression. Thus, our study reveals AGPG as a promising biomarker and potential therapeutic target in breast cancer.
2023-07-12 | GSE218130 | GEO
Project description:Why breast cancers become resistant to tamoxifen despite continued expression of the estrogen receptor alpha (ERα) and what factors are responsible for high HER2 expression in these tumors remains an enigma. HOXB7 ChIP analysis followed by validation showed that HOXB7 physically interacts with ERα, and that the HOXB7-ERα complex enhances transcription of many ERα target genes including HER2. Investigating strategies for controlling HOXB7, our studies revealed that MYC, stabilized via phosphorylation mediated by EGFR-HER2 signaling, inhibits transcription of miRNA-196a, a HOXB7 repressor. This leads to increased expression of HOXB7, ER-target genes and HER2. Repressing MYC using small molecule inhibitors reverses these events, and causes regression of breast cancer xenografts. The MYC-HOXB7-HER2 signaling pathway is eminently targetable in endocrine-resistant breast cancer.
2014-11-25 | GSE63607 | GEO
Project description:The molecular mechanisms of endocrine resistance in breast cancer remain poorly understood. Here we used PRO-seq to map the location of hundreds of genes and thousands of distal enhancers whose activities differ between endocrine sensitive and resistant MCF-7 cells. Our genome-wide screen identified a 16-fold transcriptional increase in glial-cell line derived neurotrophic factor (GDNF), a RET tyrosine kinase receptor ligand, which is both necessary and sufficient for resistance in MCF-7 cells. GDNF causes endocrine resistance by switching the active state of a bi-stable feedback loop from ERα signaling to GDNF-RET signaling. To catalyze this switch, we found that GDNF directly downregulates ERα transcription and activates the transcription factor EGR1, which, in turn, induces GDNF expression. Remarkably, both MCF-7 cells and ER+ primary tumors appear poised for endocrine resistance via the RET signaling pathway, but lack robust RET ligand expression and only develop resistance upon expression of GDNF or other RET ligands.
2018-02-22 | GSE93229 | GEO
Project description:The Notch signaling pathway regulates several differentiation and developmental processes. Reduction of oxygen availability, a condition referred to as hypoxia, impacts on the Notch response. Here we made use of RNA-Seq and ChIP-Seq analysis to investigate the Notch/hypoxia crosstalk at genomic level.
2022-07-07 | GSE194003 | GEO