SNHG3 regulates NEIL3 via transcription factor E2F1 to mediate malignant proliferation of hepatocellular carcinoma

The involvement of small nucleolar RNA host gene 3 (SNHG3) in cancer regulation has been reported. This study attempted to deeply investigate the molecular regulatory mechanism of SNHG3 on malignant progression of hepatocellular carcinoma (HCC). According to TCGA analysis, high SNHG3 expression was a risk factor for poor prognosis of HCC patients. Therefore, we further detected the mRNA level of SNHG3 in HCC tissue and cells. It was found that SNHG3 was upregulated in HCC tissue and cells. Afterwards, CCK-8 and flow cytometry assays further proved that silencing SNHG3 inhibited HCC cell proliferation while inducing cell apoptosis and G0/G1 phase arrest. It was also attested in vivo experiments that silencing SNHG3 could reduce the volume and weight of tumors and downregulate the Ki-67 expression to suppress HCC tumor growth. Next, it was discovered that SNHG3 increased the binding of E2F1 and NEIL3 promoter region, thereby activating the transcription feature of NEIL3. Lastly, rescue assays indicated that NEIL3 participated in SNHG3-mediated HCC cell cycle, apoptosis and proliferation. All in all, this study revealed the specific regulatory mechanism of SNHG3 in HCC to enable SNHG3 a hopeful marker for HCC diagnosis and treatment.

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.

Oncogenic lncRNA MALAT-1 recruits E2F1 to upregulate RAD51 expression and thus promotes cell autophagy and tumor growth in non-small cell lung cancer

INTRODUCTION

LncRNA MALAT-1 expression is involved in regulating activities of non-small-cell lung cancer (NSCLC) cells. This study aimed to investigate the effects of lncRNA MALAT-1 on chemosensitivity of NSCLC cells by regulating autophagy.

METHODS

We first validated the expression of lncRNA MALAT-1 in NSCLC cell lines. NSCLC cell lines with high lncRNA MALAT-1 expression were exposed to doxorubicin (DOX) to assess chemosensitivity. Further LncMAP database retrieval and ChIP, RIP and luciferase activity assays were conducted to explore interplay between lncRNA MALAT-1, RAD51, and E2F1. Immunofluorescence staining was performed to evaluate formation of autophagosomes in NSCLC cells. Ectopic expression and knockdown methods were used for in vitro mechanism experiments and in vivo substantiation.

RESULTS

LncRNA MALAT-1 was overexpressed in NSCLC cells, and could promote NSCLC cell autophagy and inhibit its chemosensitivity. In vitro cell mechanism verification experiments showed that lncRNA MALAT-1 could recruit transcription factor E2F1 to bind to the promoter of RAD51, so as to promote the transcriptional expression of RAD51. In addition, cell function experiments in vitro showed that ectopically expressed lncRNA MALAT-1 promoted NSCLC cell autophagy and inhibited its chemosensitivity, while RAD51 knockdown negated its effect. Finally, in vivo animal experiments confirmed that lncRNA MALAT-1 silencing could impede the tumor growth.

CONCLUSIONS

Taken together, this study revealed that silencing lncRNA MALAT-1 enhanced chemosensitivity of NSCLC cells by promoting autophagy, highlighting a feasible approach to prevent chemoresistance in NSCLC treatment.

β-arrestin1-E2F1-ac axis regulates physiological apoptosis and cell cycle exit in cellular models of early postnatal cerebellum

Development of the cerebellum is characterized by rapid proliferation of cerebellar granule cell precursors (GCPs) induced by paracrine stimulation of Sonic hedgehog (Shh) signaling from Purkinje cells, in the external granular layer (EGL). Then, granule cell precursors differentiate and migrate into the inner granular layer (IGL) of the cerebellum to form a terminally differentiated cell compartment. Aberrant activation of Sonic hedgehog signaling leads to granule cell precursors hyperproliferation and the onset of Sonic hedgehog medulloblastoma (MB), the most common embryonal brain tumor. β-arrestin1 (ARRB1) protein plays an important role downstream of Smoothened, a component of the Sonic hedgehog pathway. In the medulloblastoma context, β-arrestin1 is involved in a regulatory axis in association with the acetyltransferase P300, leading to the acetylated form of the transcription factor E2F1 (E2F1-ac) and redirecting its activity toward pro-apoptotic gene targets. This axis in the granule cell precursors physiological context has not been investigated yet. In this study, we demonstrate that β-arrestin1 has antiproliferative and pro-apoptotic functions in cerebellar development. β-arrestin1 silencing increases proliferation of Sonic hedgehog treated-cerebellar precursor cells while decreases the transcription of E2F1-ac pro-apoptotic targets genes, thus impairing apoptosis. Indeed, chromatin immunoprecipitation experiments show a direct interaction between β-arrestin1 and the promoter regions of the pro-apoptotic E2F1 target gene and P27, indicating the double role of β-arrestin1 in controlling apoptosis and cell cycle exit in a physiological context. Our data elucidate the role of β-arrestin1 in the early postnatal stages of cerebellar development, in those cell compartments that give rise to medulloblastoma. This series of experiments suggests that the physiological function of β-arrestin1 in neuronal progenitors is to directly control, cooperating with E2F1 acetylated form, transcription of pro-apoptotic genes.

DTL is a Novel Downstream Gene of E2F1 that Promotes the Progression of Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC), one of the world's most prevalent malignancies, accounts for 90% of primary liver cancer cases. Recent studies have shown an increased expression of denticles E3 ubiquitin protein ligase homolog (DTL) in several different tumor types, but its function and regulatory mechanisms remain unclear.

AIMS

This study aimed to investigate the expressions of the Cullin4 (CUL4) complex in HCC and elucidate the roles of DTL in HCC cells.

METHODS

The relative expression of the CUL4 complex and its clinical significance were analyzed with The Cancer Genome Atlas (TCGA) data, and the level of DTL was confirmed by immunohistochemistry. The functions of DTL1 and upstream E2F1 were evaluated by a Western blot, MTT, transwell, and xenograft in HCC cell lines.

RESULTS

The elevated mRNA expression of the CUL4 complex, including CUL4B, DDB1 (Damage Specific DNA Binding Protein 1), and DTL, was associated with the overall survival of HCC patients. We also found that the DTL protein was elevated in HCC tissues, and patients with highly expressed DTL and nucleus-located DTL had a poorer survival time. DTL knockdown significantly inhibited cancer proliferation, migration, and invasion. Further experiments showed that E2F1 was an upstream regulatory molecule of DTL, which was bound to the promoter of DTL, promoting the expression of DTL.

CONCLUSION

The study results demonstrate that E2F1-DTL signaling promotes the growth, migration, and invasion of HCC cells, which provides new insights and a potential biological target for future HCC therapies.

BET Inhibitors Induce p53-Independent Growth Arrest in HCT116 Cells via Epigenetic Control of the E2F1/c-MYC Axis

Although bromodomain and extraterminal (BET) inhibitors (BETis) have anti-tumor potential, the underlying molecular mechanism is poorly understood. We found that BETis effectively repressed cell growth via G1/S arrest and migration of HCT116 cells in a p53-independent manner. BETis increased the expression of p21WAF1 and repressed the expression of E2F target genes. Consistent with this, retinoblastoma protein (Rb) phosphorylation was downregulated by BETis, supporting E2F inactivation. To investigate the epigenetic mechanism, chromatin immunoprecipitation (ChIP) assays were employed using the E2F1 target gene c-MYC. Following BETi treatment, recruitment of phosphorylated Rb, BRD2, and MLL2 to the c-MYC promoter was reduced, whereas recruitment of unphosphorylated Rb and EZH2 was increased. Consequently, decreased H4K5/K12ac and H3K4me3 accumulation but increased H3K27me3 accumulation were observed. Overall, this study suggests that BETis may be useful for the treatment of colorectal cancer via epigenetic regulation of the E2F1/c-MYC axis, leading to growth arrest in a p53-independent manner.

The transcript NR 134251.1 of lncRNA APTR with an opposite function to all transcripts inhibits proliferation and induces apoptosis by regulating proliferation and apoptosis-related genes

Arsenic (As) exposure has been a global public health concern for hundreds of millions worldwide. LncRNA APTR (Alu-mediated p21 transcriptional regulator) plays an essential role in tumor growth and development. However, its function in arsenic-induced toxicological responses is still unknown. In this study, we found that the expressions of all transcripts and the transcript NR 134251.1 of APTR were increased in a dose-dependent manner in 16HBE cells treated with sodium arsenite (NaAsO₂). Silencing the transcript NR 134251.1 of APTR inhibited cell proliferation and induced apoptosis. However, silencing all transcripts of APTR had the opposite function to the transcript NR 134251.1. Then we examined the protein level of the proliferation and apoptosis-related genes after silencing the transcript NR 134251.1 of APTR. The results showed that silencing the transcript NR 134251.1 of APTR up-regulated the expression of transcription factor E2F1 and regulated its downstream genes involved in proliferation and apoptosis, including p53, phospho-p53-S392, phospho-p53-T55, p21, Cyclin D1, PUMA, Fas, Bim, BIK, Caspase-3, Caspase-7, and Cyt-c. In conclusion, arsenic induced APTR expression and the transcript NR 134251.1 of APTR have an opposite function to all transcripts, providing a theoretical basis for the prevention and treatment of arsenic exposure.

Drug Repurposing at the Interface of Melanoma Immunotherapy and Autoimmune Disease

Cancer cells have a remarkable ability to evade recognition and destruction by the immune system. At the same time, cancer has been associated with chronic inflammation, while certain autoimmune diseases predispose to the development of neoplasia. Although cancer immunotherapy has revolutionized antitumor treatment, immune-related toxicities and adverse events detract from the clinical utility of even the most advanced drugs, especially in patients with both, metastatic cancer and pre-existing autoimmune diseases. Here, the combination of multi-omics, data-driven computational approaches with the application of network concepts enables in-depth analyses of the dynamic links between cancer, autoimmune diseases, and drugs. In this review, we focus on molecular and epigenetic metastasis-related processes within cancer cells and the immune microenvironment. With melanoma as a model, we uncover vulnerabilities for drug development to control cancer progression and immune responses. Thereby, drug repurposing allows taking advantage of existing safety profiles and established pharmacokinetic properties of approved agents. These procedures promise faster access and optimal management for cancer treatment. Together, these approaches provide new disease-based and data-driven opportunities for the prediction and application of targeted and clinically used drugs at the interface of immune-mediated diseases and cancer towards next-generation immunotherapies.

Adipose-derived mesenchymal stem cell-secreted extracellular vesicles alleviate non-alcoholic fatty liver disease via delivering miR-223-3p

Increasing studies have identified the potential of mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) in non-alcoholic fatty liver disease (NAFLD) treatment. Hence, we further focused on the potential of adipose-derived MSC (ADSC)-EVs in NAFLD by delivering miR-223-3p. The uptake of isolated ADSC-EVs by hepatocytes was assessed, and the expression of miR-223-3p in ADSC-EVs and hepatocytes was characterized. It was established that miR-223-3p, enriched in ADSC-EVs, could be delivered by ADSC-EVs into hepatocytes. Using co-culture system and gain-of-function approach, we evaluated the effect of ADSC-EVs carrying miR-223-3p on lipid accumulation and liver fibrosis in pyrrolizidine alkaloids (PA)-induced hepatocytes and a high-fat diet-induced NAFLD mouse model. Bioinformatics websites and dual-luciferase reporter gene assay were performed to determine the interactions between miR-223-3p and E2F1, which was further validated by rescue experiments. ADSC-EVs containing miR-223-3p displayed suppressive effects on lipid accumulation and liver fibrosis through E2F1 inhibition, since E2F1 was demonstrated as a target gene of miR-223-3p. The protective role of ADSC-EVs by delivering miR-223-3p was then confirmed in the mouse model. Collectively, this study elucidated that ADSC-EVs delayed the progression NAFLD through the delivery of anti-fibrotic miR-223-3p and subsequent E2F1 suppression, which may suggest miR-223-3p-loaded ADSC-EVs to be a potential therapeutic approach for NAFLD.

E2F1 regulates miR-215-5p to aggravate paraquat-induced pulmonary fibrosis via repressing BMPR2 expression

Background

Pulmonary fibrosis is considered to be an irreversible lung injury, which can be caused by paraquat (PQ) poisoning. MiRNAs have been demonstrated crucial roles in pulmonary fibrosis caused by numerous approaches including PQ induction. The purpose of this study was to investigate the role and the underlying mechanism of miR-215 in PQ-induced pulmonary fibrosis.

Methods

The cell and animal models of pulmonary fibrosis were established through PQ intervention. Cell viability was performed to test by MTT assay. Immunofluorescence assay was used to detect COL1A1 expression and its location. The relationships among E2F1, miR-215-5p, and BMPR2 were validated by dual luciferase reporter gene assay, chromatin immunoprecipitation and RNA-binding protein immunoprecipitation. Lung morphology was evaluated by hematoxylin and eosin staining.

Results

MiR-215-5p was upregulated in PQ-induced pulmonary fibrosis in vitro and in vivo. MiR-215-5p silencing relieved PQ-induced pulmonary fibrosis progression by enhancing cell viability and reducing the expression of fibrosis-related markers (COL1A1, COL3A1, and α-SMA). Mechanistically, miR-215-5p directly targeted BMRP2. BMPR2 knockdown abolished the suppressive effects of miR-215-5p knockdown on PQ-induced pulmonary fibrosis. In addition, E2F1 interacted with miR-215-5p promoter and positively regulated miR-215-5p expression. E2F1 downregulation reduced miR-215-5p level and promoted BMPR2 level via regulating TGF-β/Smad3 pathway, and then suppressed PQ-induced pulmonary fibrosis, whereas these effects were compromised by miR-215-5p sufficiency.

Conclusion

MiR-215-5p was activated by E2F1 to repress BMPR2 expression and activate TGF-β/Smad3 pathway, which aggravated PQ-induced pulmonary fibrosis progression. Targeting the E2F1/miR-215-5p/BMPR2 axis might be a new approach to alleviate PQ-induced pulmonary fibrosis.

DJ-1 promotes osteosarcoma progression through activating CDK4/RB/E2F1 signaling pathway

Osteosarcoma (OS) is a primary malignant tumor of the bone characterized by poor prognosis due to chemotherapy resistance and high recurrence rates. DJ-1 (PARK7) is known as an oncogene and its abnormal expression is related to the poor prognosis of various types of malignant tumors. It was found in this study that upregulated expression of DJ-1 was closely correlated with the prognosis of OS patients by promoting the proliferation, migration and chemotherapy resistance of OS cells in vitro through regulating the activity of CDK4 but not through the oxidation mechanism or AKT pathway. The combination of DJ-1 and CDK4 promoted RB phosphorylation, leading to the dissociation of E2F1 into the nucleus to regulate the expression of cell cycle-related genes. The tumor xenograft mouse model demonstrated that DJ-1 knockout suppressed tumor growth in vivo. All these findings indicate that DJ-1 can affect the occurrence and progression of OS by regulating the CDK/RB/E2F1axis, suggesting a novel therapeutic opportunity for OS patients.

Disulfiram/Copper Suppresses Cancer Stem Cell Activity in Differentiated Thyroid Cancer Cells by Inhibiting BMI1 Expression

Differentiated thyroid carcinomas (DTCs), which have papillary and follicular types, are common endocrine malignancies worldwide. Cancer stem cells (CSCs) are a particular type of cancer cells within bulk tumors involved in cancer initiation, drug resistance, and metastasis. Cells with high intracellular aldehyde hydrogenase (ALDH) activity are a population of CSCs in DTCs. Disulfiram (DSF), an ALDH inhibitor used for the treatment of alcoholism, reportedly targets CSCs in various cancers when combined with copper. This study reported for the first time that DSF/copper can inhibit the proliferation of papillary and follicular DTC lines. DSF/copper suppressed thyrosphere formation, indicating the inhibition of CSC activity. Molecular mechanisms of DSF/copper involved downregulating the expression of B lymphoma Mo-MLV insertion region 1 homolog (BMI1) and cell cycle-related proteins, including cyclin B2, cyclin-dependent kinase (CDK) 2, and CDK4, in a dose-dependent manner. BMI1 overexpression diminished the inhibitory effect of DSF/copper in the thyrosphere formation of DTC cells. BMI1 knockdown by RNA interference in DTC cells also suppressed the self-renewal capability. DSF/copper could inhibit the nuclear localization and transcriptional activity of c-Myc and the binding of E2F1 to the BMI1 promoter. Overexpression of c-Myc or E2F1 further abolished the inhibitory effect of DSF/copper on BMI1 expression, suggesting that the suppression of c-Myc and E2F1 by DSF/copper was involved in the downregulation of BMI1 expression. In conclusion, DSF/copper targets CSCs in DTCs by inhibiting c-Myc- or E2F1-mediated BMI1 expression. Therefore, DSF is a potential therapeutic agent for future therapy in DTCs.

Metformin alleviates bone loss in ovariectomized mice through inhibition of autophagy of osteoclast precursors mediated by E2F1

Background

Postmenopausal bone loss, mainly caused by excessive bone resorption mediated by osteoclasts, has become a global public health burden. Metformin, a hypoglycemic drug, has been reported to have beneficial effects on maintaining bone health. However, the role and underlying mechanism of metformin in ovariectomized (OVX)-induced bone loss is still vague.

Results

In this study, we demonstrated for the first time that metformin administration alleviated bone loss in postmenopausal women and ovariectomized mice, based on reduced bone resorption markers, increased bone mineral density (BMD) and improvement of bone microstructure. Then, osteoclast precursors administered metformin in vitro and in vivo were collected to examine the differentiation potential and autophagical level. The mechanism was investigated by infection with lentivirus-mediated BNIP3 or E2F1 overexpression. We observed a dramatical inhibition of autophagosome synthesis and osteoclast formation and activity. Treatment with RAPA, an autophagy activator, abrogated the metformin-mediated autophagy downregulation and inhibition of osteoclastogenesis. Additionally, overexpression of E2F1 demonstrated that reduction of OVX-upregulated autophagy mediated by metformin was E2F1 dependent. Mechanistically, metformin-mediated downregulation of E2F1 in ovariectomized mice could downregulate BECN1 and BNIP3 levels, which subsequently perturbed the binding of BECN1 to BCL2. Furthermore, the disconnect between BECN1 and BCL2 was shown by BNIP3 overexpression.

Conclusion

In summary, we demonstrated the effect and underlying mechanism of metformin on OVX-induced bone loss, which could be, at least in part, ascribed to its role in downregulating autophagy during osteoclastogenesis via E2F1-dependent BECN1 and BCL2 downregulation, suggesting that metformin or E2F1 inhibitor is a potential agent against postmenopausal bone loss.

An Expanded Interplay Network between NF-κB p65 (RelA) and E2F1 Transcription Factors: Roles in Physiology and Pathology

Transcription Factors (TFs) are the main regulators of gene expression, controlling among others cell homeostasis, identity, and fate. TFs may either act synergistically or antagonistically on nearby regulatory elements and their interplay may activate or repress gene expression. The family of NF-κB TFs is among the most important TFs in the regulation of inflammation, immunity, and stress-like responses, while they also control cell growth and survival, and are involved in inflammatory diseases and cancer. The family of E2F TFs are major regulators of cell cycle progression in most cell types. Several studies have suggested the interplay between these two TFs in the regulation of numerous genes controlling several biological processes. In the present study, we compared the genomic binding landscape of NF-κB RelA/p65 subunit and E2F1 TFs, based on high throughput ChIP-seq and RNA-seq data in different cell types. We confirmed that RelA/p65 has a binding profile with a high preference for distal enhancers bearing active chromatin marks which is distinct to that of E2F1, which mostly generates promoter-specific binding. Moreover, the RelA/p65 subunit and E2F1 cistromes have limited overlap and tend to bind chromatin that is in an active state even prior to immunogenic stimulation. Finally, we found that a fraction of the E2F1 cistrome is recruited by NF-κΒ near pro-inflammatory genes following LPS stimulation in immune cell types.

E2F1 promotes cell cycle progression by stabilizing spindle fiber in colorectal cancer cells

BACKGROUND

E2F1 is a transcription factor that regulates cell cycle progression. It is highly expressed in most cancer cells and activates transcription of cell cycle-related kinases. Stathmin1 and transforming acidic coiled-coil-containing protein 3 (TACC3) are factors that enhance the stability of spindle fiber.

METHODS

The E2F1-mediated transcription of transforming acidic coiled-coil-containing protein 3 (TACC3) and stathmin1 was examined using the Cancer Genome Atlas (TCGA) analysis, quantitative polymerase chain reaction (qPCR), immunoblotting, chromatin immunoprecipitation (ChIP), and luciferase reporter. Protein-protein interaction was studied using co-IP. The spindle structure was shown by immunofluorescence. Phenotype experiments were performed through MTS assay, flow cytometry, and tumor xenografts. Clinical colorectal cancer (CRC) specimens were analyzed based on immunohistochemistry.

RESULTS

The present study showed that E2F1 expression correlates positively with the expression levels of stathmin1 and TACC3 in colorectal cancer (CRC) tissues, and that E2F1 transactivates stathmin1 and TACC3 in CRC cells. Furthermore, protein kinase A (PKA)-mediated phosphorylation of stathmin1 at Ser16 is essential to the phosphorylation of TACC3 at Ser558, facilitating the assembly of TACC3/clathrin/α-tubulin complexes during spindle formation. Overexpression of Ser16-mutated stathmin1, as well as knockdown of stathmin1 or TACC3, lead to ectopic spindle poles including disorganized and multipolar spindles. Overexpression of wild-type but not Ser16-mutated stathmin1 promotes cell proliferation in vitro and tumor growth in vivo. Consistently, a high level of E2F1, stathmin1, or TACC3 not only associates with tumor size, lymph node metastasis, TNM stage, and distant metastasis, but predicts poor survival in CRC patients.

CONCLUSIONS

E2F1 drives the cell cycle of CRC by promoting spindle assembly, in which E2F1-induced stathmin1 and TACC3 enhance the stability of spindle fiber.

E2F1 transcription factor mediates a link between fat and islets to promote β cell proliferation in response to acute insulin resistance

Prevention or amelioration of declining β cell mass is a potential strategy to cure diabetes. Here, we report the pathways utilized by β cells to robustly replicate in response to acute insulin resistance induced by S961, a pharmacological insulin receptor antagonist. Interestingly, pathways that include CENP-A and the transcription factor E2F1 that are independent of insulin signaling and its substrates appeared to mediate S961-induced β cell multiplication. Consistently, pharmacological inhibition of E2F1 blocks β-cell proliferation in S961-injected mice. Serum from S961-treated mice recapitulates replication of β cells in mouse and human islets in an E2F1-dependent manner. Co-culture of islets with adipocytes isolated from S961-treated mice enables β cells to duplicate, while E2F1 inhibition limits their growth even in the presence of adipocytes. These data suggest insulin resistance-induced proliferative signals from adipocytes activate E2F1, a potential therapeutic target, to promote β cell compensation.

Resveratrol alleviates Ang II-induced vascular smooth muscle cell senescence by upregulating E2F1/SOD2 axis

Background

Vascular smooth muscle cells (VSMCs) senescence is a crucial factor relevant to accelerate cardiovascular diseases. Resveratrol (RES) has been reported that could obstruct vascular senescence. However, the detailed molecular mechanisms of RES in VSMCs senescence are still indistinct and deserve further investigations.

Methods and Results

In this study, VSMCs were treated with 100 nM angiotensin II (Ang II) for 3 days and then followed with a range of different concentrations of RES (0.5, 5, 15, 25, 35, 50 μM), and 25 μM of RES was chose for following experiments. We found that the E2F1 and SOD2 expressions were reduced in Ang II-induced VSMCs. RES treatment impeded Ang II-induced oxidative stress and mitochondrial dysfunction through elevating E2F1 and SOD2 expression, thereby alleviating VSMCs senescence. Additionally, E2F1 knockdown reversed the protective effects of RES on VSMCs senescence caused by Ang II administration. Ch-IP assay and dual luciferase reporter gene assay validated that E2F1 could bind to the promoter region of SOD2. Furthermore, E2F1 or SOD2 overexpression blocked Ang II-induced on VSMCs senescence.

Conclusion

In conclusion, RES mitigated Ang II-induced VSMCs senescence by suppressing oxidative stress and mitochondrial dysfunction through activating E2F1/SOD2 axis. Our study disclosed that RES might be a potential drug and the axis of its regulatory mechanism might be therapeutic targets for postponing vascular senescence.

Pathway-based approach reveals differential sensitivity to E2F1 inhibition in glioblastoma

Analysis of tumor gene expression is an important approach for the classification and identification of therapeutic vulnerabilities. However, targeting glioblastoma (GBM) based on molecular subtyping has not yet translated into successful therapies. Here, we present an integrative approach based on molecular pathways to expose new potentially actionable targets. We used gene set enrichment analysis (GSEA) to conduct an unsupervised clustering analysis to condense the gene expression data from bulk patient samples and patient-derived gliomasphere lines into new gene signatures. We identified key targets that are predicted to be differentially activated between tumors and were functionally validated in a library of gliomasphere cultures. Resultant cluster-specific gene signatures associated not only with hallmarks of cell cycle and stemness gene expression, but also with cell-type specific markers and different cellular states of GBM. Several upstream regulators, such as PIK3R1 and EBF1 were differentially enriched in cells bearing stem cell like signatures and bear further investigation. We identified the transcription factor E2F1 as a key regulator of tumor cell proliferation and self-renewal in only a subset of gliomasphere cultures predicted to be E2F1 signaling dependent. Our in vivo work also validated the functional significance of E2F1 in tumor formation capacity in the predicted samples. E2F1 inhibition also differentially sensitized E2F1-dependent gliomasphere cultures to radiation treatment. Our findings indicate that this novel approach exploring cancer pathways highlights key therapeutic vulnerabilities for targeting GBM.

Troponin C-1 Activated by E2F1 Accelerates Gastric Cancer Progression via Regulating TGF-β/Smad Signaling

BACKGROUND

Troponin C-1 (TNNC1) has been previously characterized as an oncogenic gene.

AIMS

This study aimed to reveal the roles of TNNC1 in gastric cancer and the potential underlying mechanisms.

METHODS

TNNC1 siRNAs and TNNC1 overexpression plasmid were used to alter its expression in AGS, MKN45, and HGC-27 cells. CCK-8 assay, colony formation, EdU assay, flow cytometry, transwell assay, and scratch test were conducted to measure the phenotype changes. In vivo effects of TNNC1 silence were confirmed by using a xenograft mouse model. Bioinformatics analysis was conducted to screen out the transcription factor and downstream signaling of TNNC1.

RESULTS

TNNC1 was highly expressed in gastric cancer tissues and cell lines, and its expression was associated with poor prognosis. TNNC1 silence suppressed the proliferation, migration, and invasion of AGS and MKN45 cells. However, TNNC1 silence induced apoptosis by mediating the cleavage of caspase-3 and caspase-9. Overexpression of TNNC1 in HGC-27 cells led to the contrary effects. The anti-tumor effects of TNNC1 silence were also confirmed in a xenograft animal model. E2F1 was validated as an upstream transcription factor of TNNC1. Effects of TNNC1 silence on AGS cell migration and invasion were attenuated by E2F1 overexpression. Besides, TGF-β/Smad was a downstream signaling pathway of TNNC1. The anti-tumor impacts of TNNC1 silence were weaken by SB431542 (a specific inhibitor of TGF-β signaling) while accelerated by TGF-β.

CONCLUSION

TNNC1 activated by E2F1 functioned as an oncogenic gene through regulating TGF-β/Smad signaling. TNNC1 was suggested as a potential molecular drug target of gastric cancer.

The transcription factor E2F1 controls the GLP-1 receptor pathway in pancreatic β cells

The glucagon-like peptide 1 (Glp-1) has emerged as a hormone with broad pharmacological potential in type 2 diabetes (T2D) treatment, notably by improving β cell functions. The cell-cycle regulator and transcription factor E2f1 is involved in glucose homeostasis by modulating β cell mass and function. Here, we report that β cell-specific genetic ablation of E2f1 (E2f1β-/-) impairs glucose homeostasis associated with decreased expression of the Glp-1 receptor (Glp1r) in E2f1β-/- pancreatic islets. Pharmacological inhibition of E2F1 transcriptional activity in nondiabetic human islets decreases GLP1R levels and blunts the incretin effect of GLP1R agonist exendin-4 (ex-4) on insulin secretion. Overexpressing E2f1 in pancreatic β cells increases Glp1r expression associated with enhanced insulin secretion mediated by ex-4. Interestingly, ex-4 induces retinoblastoma protein (pRb) phosphorylation and E2f1 transcriptional activity. Our findings reveal critical roles for E2f1 in β cell function and suggest molecular crosstalk between the E2F1/pRb and GLP1R signaling pathways.

Aberrant Nuclear Translocation of E2F1 and Its Association in Cushing's Disease

Nonsurgical medical treatments are often performed for Cushing's disease due to high recurrence rates. However, current medical treatment that targets corticotroph adenomas are limited. To develop a treatment that specifically targets corticotrophs in Cushing's disease, it is necessary to identify corticotroph lineage-specific proteins, which are involved in the Cushing's tumor phenotype. We have previously reported that the expression of E2F transcription factor 1 (E2F1), one of the cell cycle regulatory proteins, was increased in corticotrophs in Cushing's disease model mice and was involved in the regulation of POMC gene expression. Phosphorylation of Ser337 of E2F1 (pS337-E2F1) facilitates its binding to the POMC promoter, which was suggested to contribute to elevated POMC expression in corticotrophs. Here, we report that E2F1 expression is specific to the corticotroph lineage in normal human pituitaries and that the E2F1 protein is localized in the cytosol in normal corticotrophs. We show that pS337-E2F1 is localized in the nucleus specifically in Cushing's tumors, while it is localized in the perinuclear cytoplasm in the normal pituitary. This observation demonstrates that pS337 is a marker for Cushing's tumors and suggests that phosphorylation of E2F1 may be a target for developing a novel pharmacological treatment for tumorigenesis and hormone dysregulation of Cushing's disease.

A positive feedback loop of CENPU/E2F6/E2F1 facilitates proliferation and metastasis via ubiquitination of E2F6 in hepatocellular carcinoma

Centromere protein U (CENPU), a centromere-binding protein required for cellular mitosis, has been reported to be closely associated with carcinogenesis in multiple malignancies; however, the role of CENPU in hepatocellular carcinoma (HCC) is still unclear. Herein, we investigated its biological role and molecular mechanism in the development of HCC. High CENPU expression in HCC tissue was observed and correlated positively with a poor prognosis in HCC patients. CENPU knockdown inhibited the proliferation, metastasis, and G1/S transition of HCC cells in vivo and in vitro, while ectopic expression of CENPU exerted the opposite effects. Mechanistically, CENPU physically interacted with E2F6 and promoted its ubiquitin-mediated degradation, thus affecting the transcription level of E2F1 and further accelerating the G1/S transition to promote HCC cell proliferation. E2F1 directly binds to the CENPU promoter and increases the transcription of CENPU, thereby forming a positive regulatory loop. Collectively, our findings indicate a crucial role for CENPU in E2F1-mediated signalling for cell cycle progression and reveal a role for CENPU as a predictive biomarker and therapeutic target for HCC patients.

LncRNA SNHG1 activates glycolysis to promote hepatocellular cancer progression through miR-326/PKM2 axis

AIMS

Hepatocellular cancer (HCC) is a lethal malignancy with extremely poor prognosis. Here, we attempted to investigate the role and underlying mechanism of SNHG1 in HCC progression.

METHODS

Combined with bioinformatics and experimental validation, we explored the clinical significance of SNHG1 in HCC. CCK8, cell colony formation assay, and subcutaneous tumorigenesis experiments of nude mice were conducted to evaluate the pro-proliferative capacity of SNHG1. Glucose consumption and lactate production were measured to explore the regulatory role of SNHG1 in glycolysis. Nuclear-cytoplasmic separation, qRT-PCR and Western blot assays, chromatin immunoprecipitation, luciferase reporter and RNA immunoprecipitation assays were performed to investigate the molecular mechanisms of SNHG1 in HCC.

RESULTS

SNHG1 expression was dramatically increased in HCC and positively correlated with poor prognosis. It was E2F1 that bound to SNHG1 promoter region to activate SNHG1 transcription. Furthermore, SNHG1 served as a molecular sponge for miR-326 to sequester the interaction of miR-326 and PKM2, facilitating the expression of PKM2. Activating PKM2 expression was evidenced to be one of mechanisms of SNHG1 to promote glycolysis and proliferation of HCC cells.

CONCLUSION

E2F1-activated SNHG1 modulates miR-326/PKM2 axis to facilitate glycolysis and proliferation of HCC cells. Targeting SNHG1 could be a promising therapeutic option for HCC.

Regulation of the cell cycle under anoxia stress in tail muscle and hepatopancreas of the freshwater crayfish, Orconectes virilis

Regulation of the cell cycle is an understudied response to oxygen deprivation among crustaceans. The virile crayfish, Orconectes virilis, is a freshwater crustacean that when challenged by environmental oxygen limitation undergoes metabolic rate depression (to ~30% of normal levels) and switches to anaerobic metabolism to generate energy. To understand how crayfish regulate the cell cycle in response to anoxia, key proteins involved in cell cycle control were analyzed in muscle and hepatopancreas. At the G1/S barrier, an overall upregulation of positive regulators of cell cycle progression was indicated by the responses of G1 cyclins (cyclin D and cyclin E) and Cyclin dependent kinases (CDK4, CDK6 and CDK2) under anoxia. Although the levels of Cyclin kinase inhibitors (CKIs) at this juncture were also upregulated (P15/16 and P21 (T145) in muscle and P16 (S152) in hepatopancreas), levels of a major regulator of this phase and driver to S-phase, E2F1, were significantly higher in both tissues in conjunction with deactivation of its inhibitor, Retinoblastoma (Rb) protein. At the G2/M barrier, expression profiles of the G2 cyclin B suggested cell cycle progression despite overall trend of higher activities of checkpoint kinases, (Chk1 (S317) and Chk2 (S19)), that also negatively regulate the cyclin B-CDK1 complex via CdC25C (cell division cycle 25) whose levels remained unchanged. Overall, the present study suggests continued cell cycle progression, albeit with potential deceleration, as indicated by checkpoint kinases and kinase inhibitor profiles that might play a role in protecting tissues from apoptotic damage under chronic anoxic stress.