ABSTRACT
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
ABSTRACT
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
ABSTRACT
TGF-ß/Activin induces epithelial-to-mesenchymal transition and stemness in pancreatic ductal adenocarcinoma (PDAC). However, the microRNAs (miRNAs) regulated during this response have remained yet undetermined. Here, we show that TGF-ß transcriptionally induces MIR100HG lncRNA, containing miR-100, miR-125b and let-7a in its intron, via SMAD2/3. Interestingly, we find that although the pro-tumourigenic miR-100 and miR-125b accordingly increase, the amount of anti-tumourigenic let-7a is unchanged, as TGF-ß also induces LIN28B inhibiting its maturation. Notably, we demonstrate that inactivation of miR-125b or miR-100 affects the TGF-ß-mediated response indicating that these miRNAs are important TGF-ß effectors. We integrate AGO2-RIP-seq with RNA-seq to identify the global regulation exerted by these miRNAs in PDAC cells. Transcripts targeted by miR-125b and miR-100 significantly overlap and mainly inhibit p53 and cell-cell junctions' pathways. Together, we uncover that TGF-ß induces an lncRNA, whose encoded miRNAs, miR-100, let-7a and miR-125b play opposing roles in controlling PDAC tumourigenesis.
Subject(s)
Carcinoma, Pancreatic Ductal/genetics , MicroRNAs/genetics , Pancreatic Neoplasms/genetics , RNA-Binding Proteins/genetics , Transforming Growth Factor beta1/metabolism , Animals , Carcinogenesis/genetics , Carcinoma, Pancreatic Ductal/pathology , Cell Line, Tumor , Datasets as Topic , Disease Progression , Female , Gene Expression Regulation, Neoplastic , Humans , Introns/genetics , Mice , Mice, Nude , MicroRNAs/antagonists & inhibitors , MicroRNAs/metabolism , Pancreas/pathology , Pancreatic Neoplasms/pathology , RNA, Small Interfering/metabolism , RNA-Binding Proteins/metabolism , Signal Transduction/genetics , Up-Regulation , Xenograft Model Antitumor AssaysABSTRACT
Endocrine therapies target the activation of the oestrogen receptor alpha (ERα) via distinct mechanisms, but it is not clear whether breast cancer cells can adapt to treatment using drug-specific mechanisms. Here we demonstrate that resistance emerges via drug-specific epigenetic reprogramming. Resistant cells display a spectrum of phenotypical changes with invasive phenotypes evolving in lines resistant to the aromatase inhibitor (AI). Orthogonal genomics analysis of reprogrammed regulatory regions identifies individual drug-induced epigenetic states involving large topologically associating domains (TADs) and the activation of super-enhancers. AI-resistant cells activate endogenous cholesterol biosynthesis (CB) through stable epigenetic activation in vitro and in vivo. Mechanistically, CB sparks the constitutive activation of oestrogen receptors alpha (ERα) in AI-resistant cells, partly via the biosynthesis of 27-hydroxycholesterol. By targeting CB using statins, ERα binding is reduced and cell invasion is prevented. Epigenomic-led stratification can predict resistance to AI in a subset of ERα-positive patients.
Subject(s)
Breast Neoplasms/genetics , Cholesterol/biosynthesis , Drug Resistance, Neoplasm/genetics , Epigenesis, Genetic/genetics , Estrogen Receptor alpha/metabolism , Animals , Antineoplastic Agents, Hormonal/pharmacology , Antineoplastic Agents, Hormonal/therapeutic use , Aromatase Inhibitors/pharmacology , Aromatase Inhibitors/therapeutic use , Biosynthetic Pathways/drug effects , Biosynthetic Pathways/genetics , Blotting, Western , Breast Neoplasms/drug therapy , Breast Neoplasms/pathology , Chromatin Immunoprecipitation , Drug Resistance, Neoplasm/drug effects , Female , Humans , Hydroxycholesterols , Hydroxymethylglutaryl-CoA Reductase Inhibitors/pharmacology , Immunohistochemistry , In Vitro Techniques , MCF-7 Cells , Mice , Mice, SCID , Neoplasm Invasiveness , Neoplasm Transplantation , Real-Time Polymerase Chain Reaction , Up-RegulationABSTRACT
Estrogen receptor α (ERα) is the key transcriptional driver in a large proportion of breast cancers. We report that APOBEC3B (A3B) is required for regulation of gene expression by ER and acts by causing C-to-U deamination at ER binding regions. We show that these C-to-U changes lead to the generation of DNA strand breaks through activation of base excision repair (BER) and to repair by non-homologous end-joining (NHEJ) pathways. We provide evidence that transient cytidine deamination by A3B aids chromatin modification and remodelling at the regulatory regions of ER target genes that promotes their expression. A3B expression is associated with poor patient survival in ER+ breast cancer, reinforcing the physiological significance of A3B for ER action.
Subject(s)
Breast Neoplasms/genetics , Cytidine Deaminase/genetics , Cytidine/metabolism , DNA End-Joining Repair , Estrogen Receptor alpha/genetics , Gene Expression Regulation, Neoplastic , Binding Sites , Breast Neoplasms/metabolism , Breast Neoplasms/mortality , Breast Neoplasms/pathology , Cell Line, Tumor , Cell Proliferation , Cytidine Deaminase/antagonists & inhibitors , Cytidine Deaminase/metabolism , DNA/genetics , DNA/metabolism , DNA Damage , Deamination , Estrogen Receptor alpha/metabolism , Female , Humans , Minor Histocompatibility Antigens , Prognosis , Protein Binding , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Signal Transduction , Survival Analysis , Transcription, Genetic , Trefoil Factor-1 , Tumor Suppressor Proteins/genetics , Tumor Suppressor Proteins/metabolismABSTRACT
Over 30% of ERα breast cancer patients develop relapses and progress to metastatic disease despite treatment with endocrine therapies. The pioneer factor PBX1 translates epigenetic cues and mediates estrogen induced ERα binding. Here we demonstrate that PBX1 plays a central role in regulating the ERα transcriptional response to epidermal growth factor (EGF) signaling. PBX1 regulates a subset of EGF-ERα genes highly expressed in aggressive breast tumours. Retrospective stratification of luminal patients using PBX1 protein levels in primary cancer further demonstrates that elevated PBX1 protein levels correlate with earlier metastatic progression. In agreement, PBX1 protein levels are significantly upregulated during metastatic progression in ERα-positive breast cancer patients. Finally we reveal that PBX1 upregulation in aggressive tumours is partly mediated by genomic amplification of the PBX1 locus. Correspondingly, ERα-positive breast cancer patients carrying PBX1 amplification are characterized by poor survival. Notably, we demonstrate that PBX1 amplification can be identified in tumor derived-circulating free DNA of ERα-positive metastatic patients. Metastatic patients with PBX1 amplification are also characterized by shorter relapse-free survival. Our data identifies PBX1 amplification as a functional hallmark of aggressive ERα-positive breast cancers. Mechanistically, PBX1 amplification impinges on several critical pathways associated with aggressive ERα-positive breast cancer.
Subject(s)
Breast Neoplasms/metabolism , Breast Neoplasms/pathology , DNA-Binding Proteins/metabolism , Estrogen Receptor alpha/metabolism , Proto-Oncogene Proteins/metabolism , Biomarkers, Tumor/genetics , Biomarkers, Tumor/metabolism , Breast Neoplasms/genetics , Cell Line, Tumor , DNA-Binding Proteins/genetics , Disease Progression , Female , Gene Amplification , Humans , MCF-7 Cells , Neoplasm Metastasis , Pre-B-Cell Leukemia Transcription Factor 1 , Prognosis , Proto-Oncogene Proteins/genetics , Signal Transduction , Survival AnalysisABSTRACT
The acquisition of endocrine therapy resistance in estrogen receptor α (ERα) breast cancer patients represents a major clinical problem. Notch signalling has been extensively linked to breast cancer especially in patients who fail to respond to endocrine therapy. Following activation, Notch intracellular domain is released and enters the nucleus where activates transcription of target genes. The numerous steps that cascade after activation of the receptor complicate using Notch as biomarker. Hence, this warrants the development of reliable indicators of Notch activity. DMXL2 is a novel regulator of Notch signalling not yet investigated in breast cancer. Here, we demonstrate that DMXL2 is overexpressed in a subset of endocrine therapy resistant breast cancer cell lines where it promotes epithelial to mesenchymal transition through hyper-activation of Notch signalling via V-ATPase dependent acidification. Following DMXL2 depletion or treatment with Bafilomycin A1, both EMT targets and Notch signalling pathway significantly decrease. We show for the first time that DMXL2 protein levels are significantly increased in ERα positive breast cancer patients that progress after endocrine therapy. Finally, we demonstrate that DMXL2 is a transmembrane protein with a potential extra-cellular domain. These findings identify DMXL2 as a novel, functional biomarker for ERα positive breast cancer.
