Pan-cancer analysis of super-enhancer-induced LINC00862 and validation as a SIRT1-promoting factor in cervical cancer and gastric cancer

Immune checkpoints inhibitors are effective but it needs more precise biomarkers for patient selection. We explored the biological significance of LINC00862 in pan-cancer by bioinformatics. And we studied its regulatory mechanisms using chromatin immunoprecipitation and RNA immunoprecipitation assays etc. TCGA and single-cell sequencing data analysis indicated that LINC00862 was overexpressed in the majority of tumor and stromal cells, which was related with poor prognosis. LINC00862 expression was related with immune cell infiltration and immune checkpoints expression, and had a high predictive value for immunotherapy efficacy. Mechanistically, LINC00862 competitively bound to miR-29c-3p to unleash SIRT1's tumor-promoting function. SIRT1 inhibitor-EX527 were screened by virtual screening and verified by in vitro and vivo assays. Notably, acetyltransferase P300-mediated super-enhancer activity stimulated LINC00862 transcription. Collectively, LINC00862 could be a diagnostic and prognostic biomarker. LINC00862 could also be a predictive biomarker for immunotherapy efficacy. Super-enhancer activity is the driver for LINC00862 overexpression in cervical cancer and gastric cancer.

Super-enhancer mediated upregulation of MYEOV suppresses ferroptosis in lung adenocarcinoma

Super-enhancers (SEs) exerted a crucial role in regulating the transcription of oncogenes across various malignancies while the roles of SEs driven genes and the core regulatory elements remain elusive in LUAD. In this study, cancer-specific-SE-genes of lung adenocarcinoma (LUAD) were profiled through H3K27ac ChIP-seq data of cancer cell lines and normal lung tissues, which enriched in in biological processes and pathways integral to the pathophysiology of LUAD. Based on this study, LUAD cells were susceptible to SEs inhibitors, with a reduction of cell proliferation as well as an elevation of apoptosis upon JQ1 or THZ1 intervention. Moreover, the integration of SEs landscapes, CRISPRi, ChIP-PCR, Hi-C data analysis and dual-luciferase reporter assays revealed that myeloma overexpressed gene (MYEOV) was aberrantly overexpressed in LUAD via transcriptional activation by the core SE elements. Functionally, the knockdown of MYEOV undermined cell proliferation in vitro and tumor growth in vivo. In addition, the knockdown of MYEOV generated a prominent ferroptotic phenotype, characterized by elevation of intracellular ferrous iron, reactive oxygen species and lipid peroxidation, together with alteration in marker proteins (SLC7A11, GPX4, FTH1, and ACSL4). Instead, the overexpression of MYEOV accelerated cell proliferation and abrogated ferroptosis. Clinically, the overexpression of MYEOV was observed in LUAD tissues indicating a poor prognosis in patients with LUAD. Mechanistically, SMPD1-induced autophagic degradation of GPX4 assumed a crucial role in the process of ferroptosis triggered by MYEOV knockdown. Serving as an oncogene repressing ferroptosis, promoting proliferation as well as shortening survival in LUAD, SEs-mediated activation of MYEOV might distinguish as a promising therapeutic target.

CDK5RAP3 is a novel super-enhancer-driven gene activated by master TFs and regulates ER-Phagy in neuroblastoma

Super enhancers (SEs) are genomic regions comprising multiple closely spaced enhancers, typically occupied by a high density of cell-type-specific master transcription factors (TFs) and frequently enriched in key oncogenes in various tumors, including neuroblastoma (NB), one of the most prevalent malignant solid tumors in children originating from the neural crest. Cyclin-dependent kinase 5 regulatory subunit-associated protein 3 (CDK5RAP3) is a newly identified super-enhancer-driven gene regulated by master TFs in NB; however, its function in NB remains unclear. Through an integrated study of publicly available datasets and microarrays, we observed a significantly elevated CDK5RAP3 expression level in NB, associated with poor patient prognosis. Further research demonstrated that CDK5RAP3 promotes the growth of NB cells, both in vitro and in vivo. Mechanistically, defective CDK5RAP3 interfered with the UFMylation system, thereby triggering endoplasmic reticulum (ER) phagy. Additionally, we provide evidence that CDK5RAP3 maintains the stability of MEIS2, a master TF in NB, and in turn, contributes to the high expression of CDK5RAP3. Overall, our findings shed light on the molecular mechanisms by which CDK5RAP3 promotes tumor progression and suggest that its inhibition may represent a novel therapeutic strategy for NB.

Global research hotspots, development trends and prospect discoveries of phase separation in cancer: a decade-long informatics investigation

Liquid-liquid phase separation (LLPS) is a complex and subtle phenomenon whose formation and regulation take essential roles in cancer initiation, growth, progression, invasion, and metastasis. This domain holds a wealth of underutilized unstructured data that needs further excavation for potentially valuable information. Therefore, we retrospectively analyzed the global scientific knowledge in the field over the last decade by using informatics methods (such as hierarchical clustering, regression statistics, hotspot burst, and Walktrap algorithm analysis). Over the past decade, this area enjoyed a favorable development trend (Annual Growth Rate: 34.98%) and global collaboration (International Co-authorship: 27.31%). Through unsupervised hierarchical clustering based on machine learning, the global research hotspots were divided into five dominant research clusters: Cluster 1 (Effects and Mechanisms of Phase Separation in Drug Delivery), Cluster 2 (Phase Separation in Gene Expression Regulation), Cluster 3 (Phase Separation in RNA-Protein Interaction), Cluster 4 (Reference Value of Phase Separation in Neurodegenerative Diseases for Cancer Research), and Cluster 5 (Roles and Mechanisms of Phase Separation). And further time-series analysis revealed that Cluster 5 is the emerging research cluster. In addition, results from the regression curve and hotspot burst analysis point in unison to super-enhancer (a=0.5515, R2=0.6586, p=0.0044) and stress granule (a=0.8000, R2=0.6000, p=0.0085) as the most potential star molecule in this field. More interestingly, the Random-Walk-Strategy-based Walktrap algorithm further revealed that "phase separation, cancer, transcription, super-enhancer, epigenetics"(Relevance Percentage[RP]=100%, Development Percentage[DP]=29.2%), "stress granule, immunotherapy, tumor microenvironment, RNA binding protein"(RP=79.2%, DP=33.3%) and "nanoparticle, apoptosis"(RP=70.8%, DP=25.0%) are closely associated with this field, but are still under-developed and worthy of further exploration. In conclusion, this study profiled the global scientific landscape, discovered a crucial emerging research cluster, identified several pivotal research molecules, and predicted several crucial but still under-developed directions that deserve further research, providing an important reference value for subsequent basic and clinical research of phase separation in cancer.

Evolution of the enhancer-rich regulatory region of the gene for the cell-type specific transcription factor POU1F1

Precise spatio-temporal expression of genes in organogenesis is regulated by the coordinated interplay of DNA elements such as promoter and enhancers present in the regulatory region of a given locus. POU1F1 transcription factor plays a crucial role in the development of somatotrophs, lactotrophs and thyrotrophs in the anterior pituitary gland, and in maintaining high expression of growth hormone, prolactin and TSH. In mouse, expression of POU1F1 is controlled by a region fenced by two CTCF sites, containing 5 upstream enhancer elements, designated E-A (5' to 3'). Elements C, B and A correspond to elements shown previously to play a role in pituitary development and hormonal expression; functional roles for elements E and D have not been reported. We performed comparative sequence analysis of this regulatory region and discovered that three elements, B, C and E, are present in all vertebrate groups except Agnatha. One very long (>2 kb) element (A) is unique to mammals suggesting a specific change in regulation of the gene in this group. Using DNA accessibility assay (ATAC-seq) we showed that conserved elements in anterior pituitary of four non-mammals are open, suggesting functionality as regulatory elements. We showed that, in many non-mammalian vertebrates, an additional upstream exon closely follows element E, leading to alternatively spliced transcripts. Here, element E functions as an alternative promoter, but in mammals this feature is lost, suggesting conversion of alternative promoter to enhancer. Our work shows that regulation of POU1F1 changed markedly during the course of vertebrate evolution, use of a low number of enhancer elements combined with alternative promoters in non-mammalian vertebrates being replaced by use of a unique combination of regulatory units in mammals. Most importantly, our work suggests that evolutionary conversion of alternate promoter to enhancer could be one of the evolutionary mechanisms of enhancer birth.

The immunoglobulin heavy chain super enhancer controls class switch recombination in developing B cells

Class switch recombination (CSR) plays an important role in adaptive immune response by enabling mature B cells to replace the initial IgM by another antibody class (IgG, IgE or IgA). CSR is preceded by transcription of the IgH constant genes and is controlled by the super-enhancer 3' regulatory region (3'RR) in an activation-specific manner. The 3'RR is composed of four enhancers (hs3a, hs1-2, hs3b and hs4). In mature B cells, 3'RR activity correlates with transcription of its enhancers. CSR can also occur in primary developing B cells though at low frequency, but in contrast to mature B cells, the transcriptional elements that regulate the process in developing B cells are ill-known. In particular, the role of the 3'RR in the control of constant genes' transcription and CSR has not been addressed. Here, by using a mouse line devoid of the 3'RR and a culture system that highly enriches in pro-B cells, we show that the 3'RR activity is indeed required for switch transcription and CSR, though its effect varies in an isotype-specific manner and correlates with transcription of hs4 enhancer only.

Comment on "A novel super-enhancer-related gene signature predicts prognosis and immune microenvironment for breast cancer"

The primary aim of this study is to critically evaluate and comment on the research presented in the article titled "A Novel Super-Enhancer-Related Gene Signature Predicts Prognosis and Immune Microenvironment for Breast Cancer" by Wu et al. Our specific objectives include assessing the methodology employed by the authors, particularly in regard to the utilization of a super-enhancer-related gene signature for breast cancer prognosis prediction. We propose the necessity of subgroup analysis to effectively address the heterogeneity in breast cancer subtypes, which is crucial for the applicability of the SERGs across diverse breast cancer cases. Additionally, we suggest conducting a more comprehensive immune panel study to deepen the understanding of how the immune microenvironment impacts breast cancer prognosis. Our commentary seeks to provide valuable insights into the strengths and weaknesses of the study, contributing to a more comprehensive understanding of its findings and potential clinical implications.

Genomic and epigenetic characterization of the arsenic-induced oncogenic microRNA-21

As one of the first identified oncogenic microRNAs, the precise details concerning the transcriptional regulation and function of microRNA-21 (miR-21) are still not completely established. The miR-21 gene is situated on chromosome 17q23.2, positioned at the 3'-UTR of the gene that encodes vacuole membrane protein-1 (VMP1). In this current study, we presented evidence indicating that miR-21 possesses its own gene promoter, which can be found in the intron 10 of the VMP1 gene. Chromatin immunoprecipitation followed by global DNA sequencing (ChIP-seq) revealed the presence of a broad H3K4me3 peak spanning the entire gene body of the primary miR-21 and the existence of super-enhancer clusters in the close proximity to both the miR-21 gene promoter and the transcription termination site in arsenic (As3+)-induced cancer stem-like cells (CSCs) and human induced pluripotent stem cells (hiPSCs). In non-transformed human bronchial epithelial cells (BEAS-2B), As3+ treatment enhanced Nrf2 binding to both the host gene VMP1 of miR-21 and the miR-21 gene. Knockout of Nrf2 inhibited both the basal and As3+-induced expressions of miR-21. Furthermore, the As3+-enhanced Nrf2 peaks in ChIP-seq fully overlap with these super-enhancers enriched with H3K4me1 and H3K27ac in the miR-21 gene, suggesting that Nrf2 may coordinate with other transcription factors through the super-enhancers to regulate the expression of miR-21 in cellular response to As3+. These findings demonstrate the unique genetic and epigenetic characteristics of miR-21 and may provide insights into understanding the novel mechanisms linking environmental As3+ exposure and human cancers.

The landscape of super-enhancer regulates remote target gene transcription through loop domains in adipose tissue of pig

Background

A super-enhancer (SE) is a huge cluster of multiple enhancers that control the key genes for cell identity and function. The rise of advanced chromatin immunoprecipitation sequencing (ChIP-seq) technology such as Cleavage Under Targets and Tagmentation (CUT&Tag) allows more SEs to be discovered. However, SE studies in Luchuan and Duroc pigs are very rare in animal husbandry.

Results

We used the CUT&Tag technique to identify 145 and 378 SEs from the adipose tissues of Luchuan and Duroc pigs, respectively. There were significant differences in the peak coverage ratio of SE peaks in the gene promoter region between the two breeds. Not only that, peak signals at the start and end point of the SE peak profile showed obvious spikes. The proximal target genes of SE were highly expressed compared with the background genes and the typical enhancer target genes. Subsequently, in conjoint analysis with high-throughput chromosome conformation capture sequencing (Hi-C seq) data, we predicted the remote regulatory genes of SE and found that their expression level was related to the distance of SE extended to the loop's anchor, but not the length of loops. According to our prediction model, SEs can maintain promoter accessibility of partial remote target genes through loop domains. Finally, a batch of SEs closely related to fat metabolism traits were obtained by performing a coalition analysis of quantitative trait loci and SE data.

Conclusions

This work enabled us to obtain hundreds of SEs from Luchuan and Duroc pigs. Our model provides a new method for predicting the SE remote target genes based on loop domains, and to further explore the potential role of super-enhancer in the regulation of fat metabolism.

Prognostic and predictive value of super-enhancer-derived signatures for survival and lung metastasis in osteosarcoma

BACKGROUND

Risk stratification and personalized care are crucial in managing osteosarcoma due to its complexity and heterogeneity. However, current prognostic prediction using clinical variables has limited accuracy. Thus, this study aimed to explore potential molecular biomarkers to improve prognostic assessment.

METHODS

High-throughput inhibitor screening of 150 compounds with broad targeting properties was performed and indicated a direction towards super-enhancers (SEs). Bulk RNA-seq, scRNA-seq, and immunohistochemistry (IHC) were used to investigate SE-associated gene expression profiles in osteosarcoma cells and patient tissue specimens. Data of 212 osteosarcoma patients who received standard treatment were collected and randomized into training and validation groups for retrospective analysis. Prognostic signatures and nomograms for overall survival (OS) and lung metastasis-free survival (LMFS) were developed using Cox regression analyses. The discriminatory power, calibration, and clinical value of nomograms were evaluated.

RESULTS

High-throughput inhibitor screening showed that SEs significantly contribute to the oncogenic transcriptional output in osteosarcoma. Based on this finding, focus was given to 10 SE-associated genes with distinct characteristics and potential oncogenic function. With multi-omics approaches, the hyperexpression of these genes was observed in tumor cell subclusters of patient specimens, which were consistently correlated with poor outcomes and rapid metastasis, and the majority of these identified SE-associated genes were confirmed as independent risk factors for poor outcomes. Two molecular signatures were then developed to predict survival and occurrence of lung metastasis: the SE-derived OS-signature (comprising LACTB, CEP55, SRSF3, TCF7L2, and FOXP1) and the SE-derived LMFS-signature (comprising SRSF3, TCF7L2, FOXP1, and APOLD1). Both signatures significantly improved prognostic accuracy beyond conventional clinical factors.

CONCLUSIONS

Oncogenic transcription driven by SEs exhibit strong associations with osteosarcoma outcomes. The SE-derived signatures developed in this study hold promise as prognostic biomarkers for predicting OS and LMFS in patients undergoing standard treatments. Integrative prognostic models that combine conventional clinical factors with these SE-derived signatures demonstrate substantially improved accuracy, and have the potential to facilitate patient counseling and individualized management.

Super-enhancers: Implications in gastric cancer

Gastric cancer (GC) is the fifth most prevalent malignancy and the third leading cause of cancer-related mortality globally. Despite intensive efforts to enhance the efficiencies of various therapeutics (chemotherapy, surgical interventions, molecular-targeted therapies, immunotherapies), the prognosis for patients with GC remains poor. This might be predominantly due to the limited understanding of the complicated etiology of GC. Importantly, epigenetic modifications and alterations are crucial during GC development. Super-enhancers (SEs) are a large cluster of adjacent enhancers that greatly activate transcription. SEs sustain cell-specific identity by enhancing the transcription of specific oncogenes. In this review, we systematically summarize how SEs are involved in GC development, including the SE landscape in GC, the SE target genes in GC, and the interventions related to SE functions for treating GC.

Super-enhancer-associated SNHG15 cooperating with FOSL1 contributes to bladder cancer progression through the WNT pathway

Small nucleolar RNA host gene 15 (SNHG15) plays an oncogenic role in many cancers. However, the role of SNHG15 in bladder cancer (BLCA) remains unclear. In this study, the regulation of SNHG15 on the activities of BLCA cells (T24 and RT112) was investigated. In detail, super-enhancers (SEs), differentially expressed genes, and functional enrichment were detected by bioinformatic analyses. Mutant cell lines lacking SNHG15-SEs were established using CRISPR-Cas9. Relative gene expression was detected by quantitative polymerase chain reaction (qPCR), western blot, in situ hybridization, and immunohistochemistry assays. Cell senescence, apoptosis, viability, and proliferation were measured. Chromatin immunoprecipitation (ChIP)-qPCR and luciferase reporter gene assays were conducted to analyze the interactions between genes. A novel super-enhancer of SNHG15 (SNHG15-SEs) was discovered in several BLCA datasets. The deletion of SNHG15-SEs resulted in a significant downregulation of SNHG15. Mechanistically, the core active region of SNHG15-SEs recruited the transcription factor FOSL1 to facilitate the SNHG15 transcription, thereby inducing the proliferation and metastasis of BLCA cells. Deletion of SNHG15-SEs inhibited the growth and metastasis of T24 and RT112 cells by inactivating the WNT/CTNNB1 pathway activation. Overexpression of FOSL1 in SNHG15-SEs restored the cell proliferation and metastasis. Next, a xenograft mouse model showed that SNHG15-SEs deletion inhibited the proliferation and metastasis of BLCA cells in vivo. Collectively, our data indicate that SNHG15-SEs recruit FOSL1 to promote the expression of SNHG15 which interacts with CTNNB1 in the nucleus to activate the transcription of ADAM12, leading to the malignance of BLCA cells.

Chromatin dynamics and subnuclear gene positioning for transcriptional regulation

Plants have been found to exhibit diverse characteristics and functions of chromatin organization, showing both similarities and differences to animals. It is becoming clear how chromatin organization is linked to transcriptional regulation in response to environmental stresses. Regulation of specific chromatin positions in the nuclear space is important for transcription, and the mechanisms that enable such chromatin dynamics are gradually being unveiled. Genes move between subdomains responsible for transcriptional activation or suppression in the subnuclear space in a gene repositioning cycle. We propose a model of localized chromatin interaction in nuclear subdomains, in which the dynamics of local chromatin interactions have a more important impact on the regulation of gene expression than large-scale chromatin organization. In this mini-review, we highlight recent findings on chromatin dynamics, particularly involving transcriptional regulation, and discuss future directions in the study of chromatin organization in plants.

A novel super-enhancer-related gene signature predicts prognosis and immune microenvironment for breast cancer

BACKGROUND

This study targeted at developing a robust, prognostic signature based on super-enhancer-related genes (SERGs) to reveal survival prognosis and immune microenvironment of breast cancer.

METHODS

RNA-sequencing data of breast cancer were retrieved from The Cancer Genome Atlas (TCGA), 1069 patients of which were randomly assigned into training or testing set in 1:1 ratio. SERGs were downloaded from Super-Enhancer Database (SEdb). After which, a SERGs signature was established based on the training set, with its prognostic value further validated in the testing set. Subsequently, we identified the potential function enrichment and tumor immune infiltration of the model. Moreover, in vitro experiments were completed to further explore the biological functions of ZIC2 gene (one of the risk genes in the prognostic model) in breast cancer.

RESULTS

A risk score system of prognostic value was constructed with 6 SERGs (ZIC2, NFE2, FOXJ1, KLF15, POU3F2 and SPIB) to find patients in high-risk group with significantly worse prognosis in both training and testing sets. In addition, a multivariate regression was established via integrating the 6 genes with age and N stage, indicating well performance by calibration, time-dependent receiver operating characteristic (ROC) analysis and decision curve analysis (DCA). Further analysis demonstrated that tumor-associated pathological processes and pathways were significantly enriched in the high-risk group. In general, the novel SERGs signature could be applied to screen breast cancer with immunosuppressive microenvironment for the risk score was negatively correlated with ESTIMATE score, tumor-infiltration lymphocytes (such as CD4 + and CD8 + T cell), immune checkpoints and chemotactic factors. Furthermore, down-regulation of ZIC2 gene expression inhibited the cell viability, cellular migration and cell cycle of breast cancer cells.

CONCLUSIONS

The novel SERGs signature could predict the prognosis of breast cancer; and SERGs might serve as potential therapeutic targets for breast cancer.

Super-enhancers complexes zoom in transcription in cancer

Super-enhancers (SEs) consist of multiple typical enhancers enriched at high density with transcription factors, histone-modifying enzymes and cofactors. Oncogenic SEs promote tumorigenesis and malignancy by altering protein-coding gene expression and noncoding regulatory element function. Therefore, they play central roles in the treatment of cancer. Here, we review the structural characteristics, organization, identification, and functions of SEs and the underlying molecular mechanism by which SEs drive oncogenic transcription in tumor cells. We then summarize abnormal SE complexes, SE-driven coding genes, and noncoding RNAs involved in tumor development. In summary, we believe that SEs show great potential as biomarkers and therapeutic targets.

SENet: A deep learning framework for discriminating super- and typical enhancers by sequence information

Super-enhancers are large domains on the genome where multiple short typical enhancers within a specific genomic distance are stitched together. Typically, they are cell type-specific and responsible for defining cell identity and regulating gene transcription. Numerous studies have demonstrated that super-enhancers are enriched for trait-associated variants, and mutations in super-enhancers are possibly related to known diseases. Recently, several machine learning-based methods have been used to distinguish super-enhancers from typical enhancers by using high-throughput data from various experimental methods. The acquisition of such experimental data is usually costly and time-consuming. In this paper, we innovatively proposed SENet, a groundbreaking method based on a deep neural network model, for discriminating between the two categories solely utilizing sequence information. SENet employs dna2vec feature embedding, convolution for local feature extraction, attention pooling for refined feature retention, and Transformer for contextual information extraction. Experiments demonstrate that SENet outperforms all current state-of-the-art computational methods and shows satisfactory performance in cross-species validation. Our method pioneers the distinction between super-enhancers and typical ones using only sequence information. The source code and datasets are stored in https://github.com/lhy0322/SENet.

Super-enhancer-driven TOX2 mediates oncogenesis in Natural Killer/T Cell Lymphoma

BACKGROUND

Extranodal natural killer/T-cell lymphoma (NKTL) is an aggressive type of non-Hodgkin lymphoma with dismal outcome. A better understanding of disease biology and key oncogenic process is necessary for the development of targeted therapy. Super-enhancers (SEs) have been shown to drive pivotal oncogenes in various malignancies. However, the landscape of SEs and SE-associated oncogenes remain elusive in NKTL.

METHODS

We used Nano-ChIP-seq of the active enhancer marker histone H3 lysine 27 acetylation (H3K27ac) to profile unique SEs NKTL primary tumor samples. Integrative analysis of RNA-seq and survival data further pinned down high value, novel SE oncogenes. We utilized shRNA knockdown, CRISPR-dCas9, luciferase reporter assay, ChIP-PCR to investigate the regulation of transcription factor (TF) on SE oncogenes. Multi-color immunofluorescence (mIF) staining was performed on an independent cohort of clinical samples. Various function experiments were performed to evaluate the effects of TOX2 on the malignancy of NKTL in vitro and in vivo.

RESULTS

SE landscape was substantially different in NKTL samples in comparison with normal tonsils. Several SEs at key transcriptional factor (TF) genes, including TOX2, TBX21(T-bet), EOMES, RUNX2, and ID2, were identified. We confirmed that TOX2 was aberrantly overexpressed in NKTL relative to normal NK cells and high expression of TOX2 was associated with worse survival. Modulation of TOX2 expression by shRNA, CRISPR-dCas9 interference of SE function impacted on cell proliferation, survival and colony formation ability of NKTL cells. Mechanistically, we found that RUNX3 regulates TOX2 transcription by binding to the active elements of its SE. Silencing TOX2 also impaired tumor formation of NKTL cells in vivo. Metastasis-associated phosphatase PRL-3 has been identified and validated as a key downstream effector of TOX2-mediated oncogenesis.

CONCLUSIONS

Our integrative SE profiling strategy revealed the landscape of SEs, novel targets and insights into molecular pathogenesis of NKTL. The RUNX3-TOX2-SE-TOX2-PRL-3 regulatory pathway may represent a hallmark of NKTL biology. Targeting TOX2 could be a valuable therapeutic intervene for NKTL patients and warrants further study in clinic.

Integrative analysis of a novel super-enhancer-associated lncRNA prognostic signature and identifying LINC00945 in aggravating glioma progression

BACKGROUND

Super-enhancers (SEs), driving high-level expression of genes with tumor-promoting functions, have been investigated recently. However, the roles of super-enhancer-associated lncRNAs (SE-lncRNAs) in tumors remain undetermined, especially in gliomas. We here established a SE-lncRNAs expression-based prognostic signature to choose the effective treatment of glioma and identify a novel therapeutic target.

METHODS

Combined analysis of RNA sequencing (RNA-seq) data and ChIP sequencing (ChIP-seq) data of glioma patient-derived glioma stem cells (GSCs) screened SE-lncRNAs. Chinese Glioma Genome Atlas (CGGA) and The Cancer Genome Atlas (TCGA) datasets served to construct and validate SE-lncRNA prognostic signature. The immune profiles and potential immuno- and chemotherapies response prediction value of the signature were also explored. Moreover, we verified the epigenetic activation mechanism of LINC00945 via the ChIP assay, and its effect on glioma was determined by performing the functional assay and a mouse xenograft model.

RESULTS

6 SE-lncRNAs were obtained and identified three subgroups of glioma patients with different prognostic and clinical features. A risk signature was further constructed and demonstrated to be an independent prognostic factor. The high-risk group exhibited an immunosuppressive microenvironment and was higher enrichment of M2 macrophage, regulatory T cells (Tregs), and Cancer-associated fibroblasts (CAFs). Patients in the high-risk group were better candidates for immunotherapy and chemotherapeutics. The SE of LINC00945 was further verified via ChIP assay. Mechanistically, BRD4 may mediate epigenetic activation of LINC00945. Additionally, overexpression of LINC00945 promoted glioma cell proliferation, EMT, migration, and invasion in vitro and xenograft tumor formation in vivo.

CONCLUSION

Our study constructed the first prognostic SE-lncRNA signature with the ability to optimize the choice of patients receiving immuno- and chemotherapies and provided a potential therapeutic target for glioma.

Expression of integrin β-7 is epigenetically enhanced in multiple myeloma subgroups with high-risk cytogenetics

BACKGROUND

Oncogenic overexpression of integrin-β7 (ITGB7) in cases of high-risk multiple myeloma (MM) was reported to promote enhanced interactions between neoplastic plasma-B cells and stromal cells to develop cell-adhesion mediated drug resistance.

METHODS

Expression profiles of adhesion related genes were analyzed in a cohort of MM patients containing major IgH translocations or hyperdiploidies (HY), diagnosed at the premalignant monoclonal gammopathy of undetermined significance (MGUS; n = 103), smoldering multiple myeloma; (SMM; n = 190) or MM (MM; n = 53) stage. Differential expression was integrated with loci-specific alterations in DNA-methylation and chromatin marks in MM patients. A CRISPR-based targeted induction of DNA-methylation at the ITGB7 super-enhancer (SE) in MM.1S cells was employed to intersect the impact of cis-regulatory elements on ITGB7 expression.

RESULTS

ITGB7 was significantly (p < 0.05) upregulated in patients with t(14;16) and t(14;20) subgroups in all MGUS, SMM and MM stages, but sporadically upregulated in t(4;14) subgroup at the MM stage. We demonstrate a predetermined enhancer state on ITGB7 in primary-B cells that is maintained under bivalent chromatin, which undergoes a process of chromatin-state alterations and develops into an active enhancer in cases of the t(4;14) subgroup or SE in cases of the t(14;16) subgroup. We also demonstrate that while targeted induction of DNA-methylation at the ITGB7-SE further upregulated the gene, inhibition of ITGB7-SE-associated transcription factor bromodomain-4 downregulated expression of the gene.

CONCLUSIONS

Our findings suggest an epigenetic regulation of oncogenic overexpression of ITGB7 in MM cells, which could be critical in MM progression and an attractive therapeutic target.

Twist1-YY1-p300 complex promotes the malignant progression of HCC through activation of miR-9 by forming phase-separated condensates at super-enhancers and relieved by metformin

Hepatocellular carcinoma (HCC) is one of the leading causes of death, which deserves further study to reveal the underlying molecular mechanisms. Studies have shown that miR-9 in associated with poor prognosis in HCC patients. However, the mechanisms of transcriptional activation regulation of miR-9 and its role in the malignant progression of HCC have been rarely investigated. Some transcriptional coactivators can form phase-separated condensates at super-enhancers that compartmentalize and concentrate the transcription apparatus to drive robust gene expression. Here, we demonstrate that Twist1 and YY1 could form a transcriptional complex with p300, creating local high-concentration phase-separated interaction hubs at the super-enhancers of miR-9 and activate its expression to promote the malignant progression of HCC by stimulating the migration and invasion of hepatocellular carcinoma cells. Twist1-YY1-p300 phase-separated condensates were disrupted by metformin (Met) and thus reduce miR-9 expression, thereby inhibiting the malignant progression of HCC. Our study demonstrates that the Twist1 transcriptional factor complex involved in the malignant progression of HCC can form phase separation condensates at super-enhancers of miR-9 to promote the expression of oncogenes in HCC cells. It provides a potential target for the therapy of HCC and offers insights into the mechanism of Met in HCC inhibition.

E2F1 combined with LINC01004 super-enhancer to promote hepatocellular carcinoma cell proliferation and metastasis

INTRODUCTION

Super-enhancer-associated lncRNAs play important roles in the occurrence and development of malignant tumors, including hepatocellular carcinoma (HCC).

OBJECTIVES

The current work aimed to identify and characterize super-enhancer-associated lncRNAs in the pathogenesis of HCC.

METHODS

H3K27ac ChIP-seq data from HepG2 cell line and two HCC tissues were used to identify super-enhancer-associated lncRNAs in HCC. JQ-1 treatment and CRISPR-dCas9 system were performed to confirm super-enhancer activity. Quantitative real-time PCR (qPCR), ChIP-qPCR, and dual-luciferase reporter system assay demonstrated the regulation of E2F1 on super-enhancer. Functional loss experiment was used to identify the function of LINC01004.

RESULTS

In this study, we identified and characterized LINC01004, a novel super-enhancer-associated lncRNA, as a crucial oncogene in HCC. LINC01004 was upregulated in liver cancer tissues and was associated with poor patient prognosis. Moreover, LINC01004 promoted cell proliferation and metastasis of HCC. The binding of E2F1 to the super-enhancer could promote the transcription of LINC01004, while the inhibition of super-enhancer activity decreased LINC01004 expression.

CONCLUSION

This finding might provide mechanistic insights into the molecular mechanisms underlying hepatocarcinogenesis and the biological function of super-enhancer. LINC01004 can serve as a potential therapeutic target for HCC patient.

Harnessing the MYB-dependent TAL1 5'super-enhancer for targeted therapy in T-ALL

The acquisition of genetic abnormalities engendering oncogene dysregulation underpins cancer development. Certain proto-oncogenes possess several dysregulation mechanisms, yet how each mechanism impacts clinical outcome is unclear. Using T-cell acute lymphoblastic leukemia (T-ALL) as an example, we show that patients harboring 5'super-enhancer (5'SE) mutations of the TAL1 oncogene identifies a specific patient subgroup with poor prognosis irrespective of the level of oncogene dysregulation. Remarkably, the MYB dependent oncogenic 5'SE can be targeted using Mebendazole to induce MYB protein degradation and T-ALL cell death. Of note Mebendazole treatment demonstrated efficacy in vivo in T-ALL preclinical models. Our work provides proof of concept that within a specific oncogene driven cancer, the mechanism of oncogene dysregulation rather than the oncogene itself can identify clinically distinct patient subgroups and pave the way for future super-enhancer targeting therapy.

Bioinformatics Pipelines for Identification of Super-Enhancers and 3D Chromatin Contacts

Precise regulation of gene expression is integral in development. Emerging studies have highlighted that super-enhancers (SEs), which are clusters of multiple enhancers, play critical roles in regulating cell type-specific gene expression via 3D chromatin, thereby defining the cellular identities of given cells. Here we provide optimized bioinformatics pipelines to identify SEs and 3D chromatin contacts. Our pipelines encompass the processing of chromatin immunoprecipitation sequencing (ChIP-seq) data to identify SEs and the processing of genome-wide chromosome conformation capture (Hi-C) data. We can then infer long-range chromatin contacts between SEs and other genomic regions. This integrative computational approach, which can be applied to CUT&RUN and CUT&Tag, alternative technologies to ChIP-seq, allows us to identify genomic locations of SEs and their 3D genome configuration, whereby multiple SEs act in concert. We show an analysis of mouse spermatogenesis as an example of this application.

IL-6 production through repression of UBASH3A gene via epigenetic dysregulation of super-enhancer in CD4+ T cells in rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is associated with immune dysfunction. UBASH3A as a negative regulator of T cell receptors (TCRs) signaling is a susceptible factor in RA. The aim of this study was to determine the role of UBASH3A in RA pathogenesis, by assessing the role of super-enhancer (SE) in the control of UBASH3A expression in CD4⁺ T cells and the contribution of the latter in proinflammatory cytokine production in patients with RA.

Methods

UBASH3A mRNA and protein levels were quantified by PCR and western blotting, respectively. The cells were treated with a locked nucleic acid to inhibit enhancer RNA (eRNA) expression. Chromatin immunoprecipitation was used to identify the factors recruited to UBASH3A loci displaying SE architecture. CD4⁺ T cells were transfected with UBASH3A plasmids, and cytokine levels were measured by a cytometric bead array.

Results

UBASH3A was extracted as a RA susceptibility gene associated with SNPs in the SEs that are highly expressed in CD4⁺ T cells by in silico screening. UBASH3A mRNA and protein expression levels were lower in CD4⁺ T cells of RA patients than in the control. eRNA_1 and eRNA_3 knockdown reduced UBASH3A mRNA levels. RA patients exhibited accumulation of BTB and CNC homology 2 (BACH2), the silencing transcription factor, at the UBASH3A loci in CD4⁺ T cells, but not the SE-defining factor, mediator complex subunit 1 (MED1)/bromodomain 4 (BRD4). However, opposite changes were observed in the control. Stimulation of TCRs expressed on CD4⁺ T cells of RA patients resulted in interleukin (IL)-6 production, while UBASH3A over-expression significantly inhibited the production.

Conclusions

In RA, transcription of UBASH3A is suppressed via epigenetic regulation of SE in CD4⁺ T cells. Low UBASH3A levels result in excessive TCR signal activation with subsequent enhancement of IL-6 production.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41232-022-00231-9.

Super-enhancer hijacking LINC01977 promotes malignancy of early-stage lung adenocarcinoma addicted to the canonical TGF-β/SMAD3 pathway

BACKGROUND

Lung adenocarcinoma (LUAD) is the leading cause of death worldwide. However, the roles of long noncoding RNAs (lncRNAs) hijacked by super-enhancers (SEs), vital regulatory elements of the epigenome, remain elusive in the progression of LUAD metastasis.

METHODS

SE-associated lncRNA microarrays were used to identify the dysregulated lncRNAs in LUAD. ChIP-seq, Hi-C data analysis, and luciferase reporter assays were utilized to confirm the hijacking of LINC01977 by SE. The functions and mechanisms of LINC01977 in LUAD were explored by a series of in vitro and in vivo assays.

RESULTS

We found that LINC01977, a cancer-testis lncRNA, was hijacked by SE, which promoted proliferation and invasion both in vitro and in vivo. LINC01977 interacted with SMAD3 to induce its nuclear transport, which facilitated the interaction between SMAD3 and CBP/P300, thereby regulating the downstream target gene ZEB1. Additionally, SMAD3 up-regulated LINC09177 transcription by simultaneously binding the promoter and SE, which was induced by the infiltration of M2-like tumor-associated macrophages (TAM2), subsequently activating the TGF-β/SMAD3 pathway. Moreover, LINC01977 expression was positively correlated with TAM2 infiltration and SMAD3 expression, especially in early-stage LUAD. Higher chromatin accessibility in the SE region of LINC01977 was observed with high expression of TGF-β. Early-stage LUAD patients with high LIN01977 expression had a shorter disease-free survival.

CONCLUSIONS

TAM2 infiltration induced a rich TGF-β microenvironment, activating SMAD3 to bind the promoter and the SE of LINC01977, which up-regulated LINC01977 expression. LINC01977 also promoted malignancy via the canonical TGF-β/SMAD3 pathway. LINC01977 hijacked by SE could be a valuable therapeutic target, especially for the treatment of early-stage LUAD.

IL-2/IL-2R signaling and IL-2Rα-targeted therapy in anaplastic large cell lymphoma

Anaplastic large cell lymphoma (ALCL) is a CD30-positive non-Hodgkin's T‑cell lymphoma. Despite the implementation of CD30 antibody-drug conjugate-targeted therapy into front-line treatment regimens, the prognosis of some subtypes of the disease remains unsatisfactory. In the relapsed/refractory setting, effective second-line treatment options are still lacking. However, it has been reported that blockade of direct downstream targets of activator protein‑1 (AP-1) transcription factors, which are highly dysregulated in ALCL, results in complete and sustained remission in late-stage relapsed/refractory anaplastic lymphoma kinase (ALK)-positive ALCL patients. Moreover, it has been identified that involvement of the BATF3/AP‑1 module promotes lymphomagenesis via oncogenic BATF3/IL-2/IL-2R signaling through hyperphosphorylation of ERK1/2, STAT1, and STAT5 in ALCL cells regardless of their ALK status. Therefore, targeting BATF3/IL-2/IL-2R signaling may represent a novel therapeutic alternative for ALCL patients.

BRD4 inhibitor GNE987 exerts anti-cancer effects by targeting super-enhancers in neuroblastoma

Background

Neuroblastoma (NB) is a common extracranial malignancy with high mortality in children. Recently, super-enhancers (SEs) have been reported to play a critical role in the tumorigenesis and development of NB via regulating a wide range of oncogenes Thus, the synthesis and identification of chemical inhibitors specifically targeting SEs are of great urgency for the clinical therapy of NB. This study aimed to characterize the activity of the SEs inhibitor GNE987, which targets BRD4, in NB.

Results

In this study, we found that nanomolar concentrations of GNE987 markedly diminished NB cell proliferation and survival via degrading BRD4. Meanwhile, GNE987 significantly induced NB cell apoptosis and cell cycle arrest. Consistent with in vitro results, GNE987 administration (0.25 mg/kg) markedly decreased the tumor size in the xenograft model, with less toxicity, and induced similar BRD4 protein degradation to that observed in vitro. Mechanically, GNE987 led to significant downregulation of hallmark genes associated with MYC and the global disruption of the SEs landscape in NB cells. Moreover, a novel candidate oncogenic transcript, FAM163A, was identified through analysis of the RNA-seq and ChIP-seq data. FAM163A is abnormally transcribed by SEs, playing an important role in NB occurrence and development.

Conclusion

GNE987 destroyed the abnormal transcriptional regulation of oncogenes in NB by downregulating BRD4, which could be a potential therapeutic candidate for NB.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-022-00769-8.

Super enhancers as master gene regulators in the pathogenesis of hematologic malignancies

Transcriptional deregulation of multiple oncogenes, tumor suppressors and survival pathways is a cancer cell hallmark. Super enhancers (SE) are long stretches of active enhancers in close linear proximity that ensure extraordinarily high expression levels of key genes associated with cell lineage, function and survival. SE landscape is intrinsically prone to changes and reorganization during the course of normal cell differentiation. This functional plasticity is typically utilized by cancer cells, which remodel their SE landscapes to ensure oncogenic transcriptional reprogramming. Multiple recent studies highlighted structural genetic mechanisms in non-coding regions that create new SE or hijack already existing ones. In addition, alterations in abundance/activity of certain SE-associated proteins or certain viral infections can elicit new super enhancers and trigger SE-driven transcriptional changes. For these reasons, SE profiling emerged as a powerful tool for discovering the core transcriptional regulatory circuits in tumor cells. This, in turn, provides new insights into cancer cell biology, and identifies main nodes of key cellular pathways to be potentially targeted. Since SEs are susceptible to inhibition, their disruption results in exponentially amassing 'butterfly' effect on gene expression and cell function. Moreover, many of SE elements are druggable, opening new therapeutic opportunities. Indeed, SE targeting drugs have been studied preclinically in various hematologic malignancies with promising effects. Herein, we review the unique features of SEs, present different cis- and trans-acting mechanisms through which hematologic tumor cells acquire SEs, and finally, discuss the potential of SE targeting in the therapy of hematologic malignancies.

CDK7-dependent transcriptional addiction in bone and soft tissue sarcomas: Present and Future

Cancer arises from genetic alterations that invariably contribute to dysregulated transcriptional programs. These dysregulated programs establish and maintain specific cancer cell states, leading to an intensive dependence on a set of certain regulators of gene expression. The CDK7 functions as the core of transcription, and governs RNA polymerase II and the downstream oncogenes expression in cancers. CDK7 inhibition leads to reduced recruitment of super-enhancers-driven oncogenic transcription factors, and the depression of these associated oncogenes expression, which indicates the dependence of transcriptional addiction of cancers on CDK7. Given that specified oncoproteins of sarcomas commonly function at oncogenic transcription, targeting CDK7-denpendent transcriptional addiction may be of guiding significance for the treatment of sarcomas. In this review, we summarize the advances in mechanism of targeted CDK7-dependent transcriptional addiction and discuss the path ahead to potential application discovery in bone and soft tissue sarcomas, providing theoretical considerations for bio-orthogonal therapeutic strategies.

Super-enhancer-associated TMEM44-AS1 aggravated glioma progression by forming a positive feedback loop with Myc

Background

Long non-coding RNAs (lncRNAs) have been considered as one type of gene expression regulator for cancer development, but it is not clear how these are regulated. This study aimed to identify a specific lncRNA that promotes glioma progression.

Methods

RNA sequencing (RNA-seq) and quantitative real-time PCR were performed to screen differentially expressed genes. CCK-8, transwell migration, invasion assays, and a mouse xenograft model were performed to determine the functions of TMEM44-AS1. Co-IP, ChIP, Dual-luciferase reporter assays, RNA pulldown, and RNA immunoprecipitation assays were performed to study the molecular mechanism of TMEM44-AS1 and the downstream target.

Results

We identified a novel lncRNA TMEM44-AS1, which was aberrantly expressed in glioma tissues, and that increased TMEM44-AS1 expression was correlated with malignant progression and poor survival for patients with glioma. Expression of TMEM44-AS1 increased the proliferation, colony formation, migration, and invasion of glioma cells. Knockdown of TMEM44-AS1 in glioma cells reduced cell proliferation, colony formation, migration and invasion, and tumor growth in a nude mouse xenograft model. Mechanistically, TMEM44-AS1 is directly bound to the SerpinB3, and sequentially activated Myc and EGR1/IL-6 signaling; Myc transcriptionally induced TMEM44-AS1 and directly bound to the promoter and super-enhancer of TMEM44-AS1, thus forming a positive feedback loop with TMEM44-AS. Further studies demonstrated that Myc interacts with MED1 regulates the super-enhancer of TMEM44-AS1. More importantly, a novel small-molecule Myc inhibitor, Myci975, alleviated TMEM44-AS1-promoted the growth of glioma cells.

Conclusions

Our study implicates a crucial role of the TMEM44-AS1-Myc axis in glioma progression and provides a possible anti-glioma therapeutic agent.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02129-9.

Phase separation in transcription factor dynamics and chromatin organization

Studies over the past decade have highlighted the key role of liquid-liquid phase separation in cellular organization and function. Dynamic compartmentalization of transcription factors and coactivators by such phase-separated condensates regulates the assembly of transcriptional machinery at genomic loci. Although rapid advances in microscopy have demonstrated the ubiquity of such condensates, a rigorous characterization of the physics of phase separation in transcription remains to be carried out. In this review, we discuss theoretical and experimental evidence for biomolecular condensates as dynamic regulators of transcription. Looking beyond, we highlight functional consequences for transcription factor dynamics and gene expression and discuss potential pitfalls of misclassifying biomolecular condensates as liquid droplets in the absence of a rigorous physical description.

Histone H3K4me1 strongly activates the DNase I hypersensitive sites in super-enhancers than those in typical enhancers

Super-enhancers (SEs), which consist of multiple enhancer elements, are occupied by master transcription factors and co-activators, such as Mediator, and are highly acetylated at histone H3K27. Here, we have characterized the SEs in terms of DNase I hypersensitive sites (DHSs) by analyzing publicly available chromatin immunoprecipitation (ChIP)-seq and DNase-seq data of K562 cells and compared with the DHSs in typical enhancers (TEs). DHSs in the SEs were highly marked by histone H3K4me1 than DHSs in TEs. Loss of H3K4me1 by the deletion of catalytic domains in histone methyltransferases MLL3 and MLL4 remarkably decreased histone H3K27ac and histone H3 depletion at SE DHSs than at TE DHSs. The levels of enhancer RNA (eRNA) transcripts and mRNA transcripts from the putative target genes were notably reduced at and near SE DHSs than TE DHSs following H3K4me1 loss. These results indicate that histone H3K4me1 is a marker for DHSs in SEs and that this modification has a more significant impact on the activation of SE DHSs than TE DHSs.

Super-enhancer-driven Sorting Nexin 5 expression promotes dopaminergic neuronal ferroptosis in Parkinson's disease models

Parkinson's disease (PD) is the second most prevalent neurodegenerative disease worldwide. Recent studies revealed that the ferroptosis pathway is involved in the death process of dopaminergic neurons in PD. The aberrant endosomal sorting pathway, which results in aberrant iron level in eukaryotic cells, may serve a role in the ferroptosis pathway in PD condition. However, its specific molecular mechanisms remained unclear. In the present study, we performed chromatin immunoprecipitation (ChIP) assay, the rank ordering of super-enhancers (ROSE) algorithm, and RNA interference (RNAi) to explore the regulatory mechanism of PD-specific super-enhancer (SE) in the endosomal sorting pathway and ferroptosis pathway of 6-OHDA-lesioned rats and cells. The ChIP assay and ROSE algorithm results showed that there are specific SEs expression in 6-OHDA-lesioned SNc of PD rats, and the most significant expression gene is Sorting Nexin 5 (SNX5). SNX5 silencing by RNAi experiments significantly decreased the level of ferroptosis in 6-OHDA-lesioned PC12 cells, suggesting the correlation between the SNX5, ferroptosis, and PD. In conclusion, this study investigated the mechanism by which PD-specific SE driven SNX5 promoted the ferroptosis level in PD models. This study further improved the understanding of the mechanism of ferroptosis during PD injury and provided potential therapeutic targets and clinical diagnostic markers in PD condition.

Super-enhancers: a new frontier for epigenetic modifiers in cancer chemoresistance

Although new developments of surgery, chemotherapy, radiotherapy, and immunotherapy treatments for cancer have improved patient survival, the emergence of chemoresistance in cancer has significant impacts on treatment effects. The development of chemoresistance involves several polygenic, progressive mechanisms at the molecular and cellular levels, as well as both genetic and epigenetic heterogeneities. Chemotherapeutics induce epigenetic reprogramming in cancer cells, converting a transient transcriptional state into a stably resistant one. Super-enhancers (SEs) are central to the maintenance of identity of cancer cells and promote SE-driven-oncogenic transcriptions to which cancer cells become highly addicted. This dependence on SE-driven transcription to maintain chemoresistance offers an Achilles' heel for chemoresistance. Indeed, the inhibition of SE components dampens oncogenic transcription and inhibits tumor growth to ultimately achieve combined sensitization and reverse the effects of drug resistance. No reviews have been published on SE-related mechanisms in the cancer chemoresistance. In this review, we investigated the structure, function, and regulation of chemoresistance-related SEs and their contributions to the chemotherapy via regulation of the formation of cancer stem cells, cellular plasticity, the microenvironment, genes associated with chemoresistance, noncoding RNAs, and tumor immunity. The discovery of these mechanisms may aid in the development of new drugs to improve the sensitivity and specificity of cancer cells to chemotherapy drugs.

Super-enhancer-mediated core regulatory circuitry in human cancer

Super-enhancers (SEs) are congregated enhancer clusters with high level of loading of transcription factors (TFs), cofactors and epigenetic modifications. Through direct co-occupancy at their own SEs as well as each other's, a small set of so called "master" TFs form interconnected core regulatory circuitry (CRCs) to orchestrate transcriptional programs in both normal and malignant cells. These master TFs can be predicted mathematically using epigenomic methods. In this Review, we summarize the identification of SEs and CRCs in cancer cells, the mechanisms by which master TFs and SEs cooperatively regulate cancer-type-specific expression programs, and the cancer-type- and subtype-specificity of CRC and the significance in cancer biology.

Super-enhancers for RUNX3 are required for cell proliferation in EBV-infected B cell lines

Epstein-Barr virus nuclear antigens 2 (EBNA2) mediated super-enhancers, defined by in silico data, localize near genes associated with B cell transcription factors including RUNX3. However, the biological function of super-enhancer for RUNX3 gene (seR3) remains unclear. Here, we show that two seR3s, tandemly-located at 59- and 70-kb upstream of RUNX3 transcription start site, named seR3 -59h and seR3 -70h, are required for RUNX3 expression and cell proliferation in Epstein-Barr virus (EBV)-positive malignant B cells. A BET bromodomain inhibitor, JQ1, potently suppressed EBV-positive B cell growth through the reduction of RUNX3 and MYC expression. Excision of either or both seR3s by employing CRISPR/Cas9 system resulted in the decrease in RUNX3 expression and the subsequent suppression of cell proliferation and colony forming capability. The expression of MYC was also reduced when seR3s were deleted, probably due to the loss of trans effect of seR3s on the super-enhancers for MYC. These findings suggest that seR3s play a pivotal role in expression and biological function of both RUNX3 and MYC. seR3s would serve as a potential therapeutic target in EBV-related widespread tumors.

Disruption of super-enhancer-driven tumor suppressor gene RCAN1.4 expression promotes the malignancy of breast carcinoma

Background

Super-enhancers (SEs) play a crucial role in cancer, which is often associate with activated oncogenes. However, little is known about how SEs facilitate tumour suppression. Individuals with Down syndrome exhibit a remarkably reduced incidence of breast cancer (BC), moving the search for tumor suppressor genes on human chromosome 21 (HSA21). In this study, we aim to identify and explore potential mechanisms by which SEs are established for tumor suppressor RCAN1.4 on HSA21 in BC.

Methods

In silico analysis and immunohistochemical staining were used to assess the expression and clinical relevance of RCAN1.4 and RUNX3 in BC. Function experiments were performed to evaluate the effects of RCAN1.4 on the malignancy of breast carcinoma in vitro and in vivo. ChIP-seq data analysis, ChIP-qPCR, double-CRISPR genome editing, and luciferase reporter assay were utilized to confirm RUNX3 was involved in regulating RCAN1.4-associated SE in BC. The clinical value of co-expression of RCAN1.4 and RUNX3 was evaluated in BC patients.

Results

Here, we characterized RCAN1.4 as a potential tumour suppressor in BC. RCAN1.4 loss promoted tumour metastasis to bone and brain, and its overexpression inhibited tumour growth by blocking the calcineurin-NFATc1 pathway. Unexpectedly, we found RCAN1.4 expression was driven by a ~ 23 kb-long SE. RCAN1.4-SE^distal was sensitive to BRD4 inhibition, and its deletion decreased RCAN1.4 expression by over 90% and induced the malignant phenotype of BC cells. We also discovered that the binding sites in the SE region of RCAN1.4 were enriched for consensus sequences of transcription factor RUNX3. Knockdown of RUNX3 repressed the luciferase activity and also decreased H3K27ac enrichment binding at the SE region of RCAN1.4. Furthermore, abnormal SE-driven RCAN1.4 expression mediated by RUNX3 loss could be physiologically significant and clinically relevant in BC patients. Notably, we established a prognostic model based on RCAN1.4 and RUNX3 co-expression that effectively predicted the overall survival in BC patients.

Conclusions

These findings reveal an important role of SEs in facilitating tumour suppression in BC. Considering that the combination of low RCAN1.4 and low RUNX3 expression has worse prognosis, RUNX3-RCAN1.4 axis maybe a novel prognostic biomarker and therapeutic target for BC patients.

HOXB13 controls cell state through super-enhancers

Expression of the homeodomain transcription factor HOXB13 has been demonstrated in several malignancies but its role in tumorigenesis remains elusive. We observed high levels of HOXB13 in poorly differentiated pediatric tumors including a highly aggressive childhood neoplasm - malignant rhabdoid tumor. In a xenograft model of rhabdoid tumor, knockout of HOXB13 diminished tumor growth while partial knockdown of HOXB13 promoted differentiation of tumor cells into bone. These results suggest that HOXB13 enhances rhabdoid malignancy by interfering with mesenchymal stem cell differentiation. Consistent with this hypothesis, overexpression of HOXB13 in mesenchymal progenitor cells inhibited adipogenic, myogenic, and osteogenic differentiation. Mechanistically, we demonstrated that HOXB13 binds to super-enhancer regions regulating genes involved in differentiation and tumorigenesis.

Oncogenic seRNA functional activation: a novel mechanism of tumorigenesis

seRNA is a noncoding RNA (ncRNA) transcribed from active super-enhancer (SE), through which SE exerts biological functions and participates in various physiological and pathological processes. seRNA recruits cofactor, RNA polymerase II and mediator to constitute and stabilize chromatin loop SE and promoter region, which regulates target genes transcription. In tumorigenesis, DNA insertion, deletion, translocation, focal amplification and carcinogen factor mediate oncogenic SE generation, meanwhile, oncogenic SE transcribes into tumor-related seRNA, termed as oncogenic seRNA. Oncogenic seRNA participates in tumorigenesis through activating various signal-pathways. The recent reports showed that oncogenic seRNA implicates in a widespread range of cytopathological processes in cancer progression including cell proliferation, apoptosis, autophagy, epithelial-mesenchymal transition, extracellular matrix stiffness and angiogenesis. In this article, we comprehensively summarized seRNA’s characteristics and functions, and emphatically introduced inducible formation of oncogenic seRNA and its functional mechanisms. Lastly, some research strategies on oncogenic seRNA were introduced, and the perspectives on cancer therapy that targets oncogenic seRNA were also discussed.

Long non-coding RNA MANCR is a target of BET bromodomain protein BRD4 and plays a critical role in cellular migration and invasion abilities of prostate cancer

Androgen receptor (AR)-negative castration-resistant prostate cancer (CRPC) is highly aggressive and is resistant to most of the current therapies. Bromodomain and extra terminal domain (BET) protein BRD4 binds to super-enhancers (SEs) that drive high expression of oncogenes in many cancers. A BET inhibitor, JQ1, has been found to suppress the malignant phenotypes of prostate cancer cells, however, the target genes of JQ1 remain largely unknown. Here we show that SE-associated genes specific for AR-negative CRPC PC3 cells include genes involved in migration and invasion, and that JQ1 impairs migration and invasion of PC3 cells. We identified a long non-coding RNA, MANCR, which was markedly down-regulated by JQ1, and found that BRD4 binds to the MANCR locus. MANCR knockdown led to a significant decrease in migration and invasion of PC3 cells. Furthermore, RNA sequencing analysis revealed that expression of the genes involved in migration and invasion was altered by MANCR knockdown. In summary, our data demonstrate that MANCR plays a critical role in migration and invasion of PC3 cells.

[Enhancer hijacking via disease-specific chromosomal translocation in blastic plasmacytoid dendritic cell neoplasm]

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a hematological malignancy, which seems to originate from the precursor of plasmacytoid dendritic cells. Because BPDCN has an aggressive course and poor prognosis, development of new treatment strategies is essential. Next-Generation Sequencing, a recently evolved technology, reveals new molecular mechanism of BPDCN development. Here I will discuss the recent research on the treatment of BPDCN, including the relationship between chromosomal translocation and enhancer hijacking in BPDCN.

A super-enhancer controls TGF- β signaling in pancreatic cancer through downregulation of TGFBR2

Pancreatic cancer is one of the most lethal malignant tumors due to a late diagnosis and highly invasion and metastasis. Transforming growth factor-β (TGF-β) signaling plays a vital role in the progression of pancreatic cancer. The delicate activity of TGF-β signaling is particular important for the development of aggression and metastasis which must be fine-tuned. Here, we investigated the role of super-enhancers in regulating the expression of TGF-β signaling pathway in pancreatic cancer. TGFBR2 owns the modification of H3K27Ac around the gene in pancreatic cancer cells. Inhibition of BRD4 by JQ1 robustly blocked the expression of TGFBR2 in a dose dependent manner. We successfully mapped a super-enhancer in TGFBR2 by sgRNA. Deletion of the super-enhancer in TGFBR2 (sgTGFBR2-SEΔ) significantly reduced the expression of TGFBR2 in pancreatic cancer cells. TGF-β-induced p-SMAD2/3 was greatly impaired in TGFBR2 super-enhancer deleted cells. Both migration and EMT induced by TGF-β in pancreatic cancer cells were impaired after deleting the super-enhancer of TGFBR2. Our data suggest a novel molecular mechanism by which a super-enhancer regulates TGFBR2, affecting the activity of TGF-β as well as its function in pancreatic cancer progression.

Investigating the role of super-enhancer RNAs underlying embryonic stem cell differentiation

BACKGROUND

Super-enhancer RNAs (seRNAs) are a kind of noncoding RNA transcribed from super-enhancer regions. The regulation mechanism and functional role of seRNAs are still unclear. Although super-enhancers play a critical role in the core transcriptional regulatory circuity of embryonic stem cell (ESC) differentiation, whether seRNAs have similar properties should be further investigated.

RESULTS

We analyzed cap analysis gene expression sequencing (CAGE-seq) datasets collected during the differentiation of embryonic stem cells (ESCs) to cardiomyocytes to identify the seRNAs. A non-negative matrix factorization algorithm was applied to decompose the seRNA profiles and reveal two hidden stages during the ESC differentiation. We further identified 95 and 78 seRNAs associated with early- and late-stage ESC differentiation, respectively. We found that the binding sites of master regulators of ESC differentiation, including NANOG, FOXA2, and MYC, were significantly observed in the loci of the stage-specific seRNAs. Based on the investigation of genes coexpressed with seRNA, these stage-specific seRNAs might be involved in cardiac-related functions such as myofibril assembly and heart development and act in trans to regulate the co-expressed genes.

CONCLUSIONS

In this study, we used a computational approach to demonstrate the possible role of seRNAs during ESC differentiation.

Cyclin-dependent kinase 7 inhibitor THZ1 in cancer therapy

Current cancer therapies have encountered adverse response due to poor therapeutic efficiency, severe side effects and acquired resistance to multiple drugs. Thus, there are urgent needs for finding new cancer-targeted pharmacological strategies. In this review, we summarized the current understanding with THZ1, a covalent inhibitor of cyclin-dependent kinase 7 (CDK7), which demonstrated promising anti-tumor activity against different cancer types. By introducing the anti-tumor behaviors and the potential targets for different cancers, this review aims to provide more effective approaches to CDK7 inhibitor-based therapeutic agents and deeper insight into the diverse tumor proliferation mechanisms.

Inhibition of super enhancer downregulates the expression of KLF5 in basal-like breast cancers

The transcription factor KLF5 (Krüpple-like factor 5) is highly expressed in basal-like breast cancer (BLBC), which promotes cell proliferation, survival, migration and stemness, serving as a potential therapeutic target. In the current study, a super-enhancer (SE) was identified to be located downstream of the KLF5 gene in BLBC cell lines, HCC1806 and HCC1937. JQ-1, a BRD4 inhibitor, inhibits the expression and activity of KLF5 in both HCC1806 and HCC1937 cells in a time- and dose-dependent manner. Compound 870, an in-house BRD4 inhibitor, exhibited higher potency than JQ-1 to inhibit KLF5 and BLBC growth by arresting cells in G1 phase. Additionally, THZ1, a CDK7 inhibitor, also inhibits KLF5 and BLBC growth in a similar manner. Our findings suggested that KLF5 is regulated by SE, and modulation of SE could be an effective therapeutic strategy for treating BLBC.

The SNP of rs6854845 suppresses transcription via the DNA looping structure alteration of super-enhancer in colon cells

Single-nucleotide polymorphisms (SNPs) identified by Genome-Wide Association Studies (GWASs) have been determined to closely connect with multiple diseases. Previous studies revealed one underlying mechanism that SNPs located within the regulatory elements could affect the encoding gene expression through long-range regulation. SNP rs6854845 was suggested to be a risk of colon cancer in human population. Nevertheless, the underlying molecular mechanism for colon carcinogenesis remains largely unknown. In present study, rs6854845 with G > T mutation in situ in FHC, HCT-116 and SW-480 cells were generated by Crispr/Cas9. The nearby chromatin organization was investigated by chromatin conformation capture (3C). And the expression of coding gene regulated by super-enhancer (SE) was detected by real-time PCR. We observed a significantly different pattern of the genome organization upon rs6854845 generation in colon epithelial cells but not in colon cancer cells. Moreover, we observed the shifted enrichment of H3K4me1 and H3K27ac at the SE (chr4:75.7M-76.0 M) where rs6854845 located. Furthermore, we observed that the transcription of the gene clusters regulated by SE were affected by rs6854845 in colon cells. Overall, our results demonstrated that SNP rs6854845 located in SE could destroy the long-range chromosomal interaction between SE and target gene clusters thereby affecting the transcription of these genes.

BRCA1 mutations attenuate super-enhancer function and chromatin looping in haploinsufficient human breast epithelial cells

Background

BRCA1-associated breast cancer originates from luminal progenitor cells. BRCA1 functions in multiple biological processes, including double-strand break repair, replication stress suppression, transcriptional regulation, and chromatin reorganization. While non-malignant cells carrying cancer-predisposing BRCA1 mutations exhibit increased genomic instability, it remains unclear whether BRCA1 haploinsufficiency affects transcription and chromatin dynamics in breast epithelial cells.

Methods

H3K27ac-associated super-enhancers were compared in primary breast epithelial cells from BRCA1 mutation carriers (BRCA1^mut/+) and non-carriers (BRCA1^+/+). Non-tumorigenic MCF10A breast epithelial cells with engineered BRCA1 haploinsufficiency were used to confirm the H3K27ac changes. The impact of BRCA1 mutations on enhancer function and enhancer-promoter looping was assessed in MCF10A cells.

Results

Here, we show that primary mammary epithelial cells from women with BRCA1 mutations display significant loss of H3K27ac-associated super-enhancers. These BRCA1-dependent super-enhancers are enriched with binding motifs for the GATA family. Non-tumorigenic BRCA1^mut/+ MCF10A cells recapitulate the H3K27ac loss. Attenuated histone mark and enhancer activity in these BRCA1^mut/+ MCF10A cells can be partially restored with wild-type BRCA1. Furthermore, chromatin conformation analysis demonstrates impaired enhancer-promoter looping in BRCA1^mut/+ MCF10A cells.

Conclusions

H3K27ac-associated super-enhancer loss is a previously unappreciated functional deficiency in ostensibly normal BRCA1 mutation-carrying breast epithelium. Our findings offer new mechanistic insights into BRCA1 mutation-associated transcriptional and epigenetic abnormality in breast epithelial cells and tissue/cell lineage-specific tumorigenesis.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1132-1) contains supplementary material, which is available to authorized users.

Pan-cancer analysis on microRNA-associated gene activation

Background

While microRNAs (miRNAs) were widely considered to repress target genes at mRNA and/or protein levels, emerging evidence from in vitro experiments has shown that miRNAs can also activate gene expression in particular contexts. However, this counterintuitive observation has rarely been reported or interpreted in in vivo conditions.

Methods

We systematically explored the positive correlation between miRNA and gene expressions and its potential implications in tumorigenesis, based on 8375 patient samples across 31 major human cancers from The Cancer Genome Atlas (TCGA).

Findings

We found that positive miRNA-gene correlations are surprisingly prevalent and consistent across cancer types, and show distinct patterns than negative correlations. The top-ranked positive correlations are significantly involved in the immune cell differentiation and cell membrane signaling related processes, and display strong power in stratifying patients in terms of survival rate. Although intragenic miRNAs generally tend to co-express with their host genes, a substantial portion of miRNAs shows no obvious correlation with their host gene plausibly due to non-conservation. A miRNA can upregulate a gene by inhibiting its upstream suppressor, or shares transcription factors with that gene, both leading to positive correlation. The miRNA/gene sites associated with the top-ranked positive correlations are more likely to form super-enhancers compared to randomly chosen pairs. Wet-lab experiments revealed that positive correlations partially remain in in vitro condition.

Interpretation

Our study brings new insights into the critical role of miRNA in gene regulation and the complex mechanisms underlying miRNA functions, and reveals both biological and clinical significance of miRNA-associated gene activation.

A new class of constitutively active super-enhancers is associated with fast recovery of 3D chromatin loops

Background

Super-enhancers or stretch enhancers are clusters of active enhancers that often coordinate cell-type specific gene regulation during development and differentiation. In addition, the enrichment of disease-associated single nucleotide polymorphism in super-enhancers indicates their critical function in disease-specific gene regulation. However, little is known about the function of super-enhancers beyond gene regulation.

Results

In this study, through a comprehensive analysis of super-enhancers in 30 human cell/tissue types, we identified a new class of super-enhancers which are constitutively active across most cell/tissue types. These ‘common’ super-enhancers are associated with universally highly expressed genes in contrast to the canonical definition of super-enhancers that assert cell-type specific gene regulation. In addition, the genome sequence of these super-enhancers is highly conserved by evolution and among humans, advocating their universal function in genome regulation. Integrative analysis of 3D chromatin loops demonstrates that, in comparison to the cell-type specific super-enhancers, the cell-type common super-enhancers present a striking association with rapidly recovering loops.

Conclusions

In this study, we propose that a new class of super-enhancers may play an important role in the early establishment of 3D chromatin structure.

Electronic supplementary material

The online version of this article (10.1186/s12859-019-2646-3) contains supplementary material, which is available to authorized users.

The hyper-activation of transcriptional enhancers in breast cancer

Background

Activation of transcription enhancers, especially super-enhancers, is one of the critical epigenetic features of tumorigenesis. However, very few studies have systematically identified the enhancers specific in cancer tissues.

Methods

Here, we studied the change of histone modifications in MMTV-PyVT breast cancer model, combining mass spectrometry-based proteomics and ChIP-seq-based epigenomics approaches. Some of the proteomic results were confirmed with western blotting and IHC staining. An inhibitor of H3K27ac was applied to study its effect on cancer development.

Results

H3K27ac and H4K8ac are elevated in cancer, which was confirmed in patient tissue chips. ChIP-seq revealed that H4K8ac is co-localized with H3K27ac on chromatin, especially on distal enhancers. Epigenomic studies further identified a subgroup of super-enhancers marked by H3K4me3 peaks in the intergenic regions. The H3K4me3-enriched regions enhancers are associated with higher level of H3K27ac and H4K8ac compared with the average level of conventional super-enhancers and are associated with higher transcription level of their adjacent genes. We identified 148 H3K4me3-enriched super-enhancers with higher gene expression in tumor, which may be critical for breast cancer. One inhibitor for p300 and H3K27ac, C646, repressed tumor formation probably through inhibiting Vegfa and other genes.

Conclusions

Taken together, our work identifies novel regulators and provides important resource to the genome-wide enhancer studies in breast cancer and raises the possibility of cancer treatment through modulating enhancer activity.

Electronic supplementary material

The online version of this article (10.1186/s13148-019-0645-x) contains supplementary material, which is available to authorized users.