Circ-EZH2 knockdown reverses DDAH1 and CBX3-mediated cell growth and invasion in glioma through miR-1265 sponge activity

RNA sequencing reveals CircRNA expression profiles in chicken embryo fibroblasts infected with velogenic Newcastle disease virus

Introduction

Newcastle disease virus (NDV) is an important avian pathogen prevalent worldwide; it has an extensive host range and seriously harms the poultry industry. Velogenic NDV strains exhibit high pathogenicity and mortality in chickens. Circular RNAs (circRNAs) are among the most abundant and conserved eukaryotic transcripts. They are part of the innate immunity and antiviral response. However, the relationship between circRNAs and NDV infection is unclear.

Methods

In this study, we used circRNA transcriptome sequencing to analyze the differences in circRNA expression profiles post velogenic NDV infection in chicken embryo fibroblasts (CEFs). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to reveal significant enrichment of differentially expressed (DE) circRNAs. The circRNA- miRNA-mRNA interaction networks were further predicted. Moreover, circ-EZH2 was selected to determine its effect on NDV infection in CEFs.

Results

NDV infection altered circRNA expression profiles in CEFs, and 86 significantly DE circRNAs were identified. GO and KEGG enrichment analyses revealed significant enrichment of DE circRNAs for metabolism-related pathways, such as lysine degradation, glutaminergic synapse, and alanine, aspartic-acid, and glutamic-acid metabolism. The circRNA- miRNA-mRNA interaction networks further demonstrated that CEFs might combat NDV infection by regulating metabolism through circRNA-targeted mRNAs and miRNAs. Furthermore, we verified that circ-EZH2 overexpression and knockdown inhibited and promoted NDV replication, respectively, indicating that circRNAs are involved in NDV replication.

Conclusions

These results demonstrate that CEFs exert antiviral responses by forming circRNAs, offering new insights into the mechanisms underlying NDV-host interactions.

Roles of circular RNAs in regulating the development of glioma

BACKGROUND

Glioma is the most common malignant tumor in the central nervous system. In patients with glioma, the prognosis is poor and median survival is only 12-15 months. With the recent development of sequencing technology, important roles of noncoding RNAs are being discovered in cells, especially those of circular RNAs (circRNAs). Because circRNAs are stable, abundant, and highly conserved, they are regarded as novel biomarkers in the early diagnosis and prognosis of diseases.

PURPOSE

In this review, roles and mechanisms of circRNAs in the development of glioma are summarized.

METHODS

This paper collects and reviews relevant PubMed literature.

CONCLUSION

Several classes of circRNAs are highly expressed in glioma and are associated with malignant biological behaviors of gliomas, including proliferation, migration, invasion, apoptosis, angiogenesis, and drug resistance. Further studies are needed to clarify the roles of circRNAs in glioma and to determine whether it is possible to increase therapeutic effects on tumors through circRNA intervention.

circEZH2E2 /E3 is a dual suppressor of miR363/miR708 to promote EZH2 expression and prostate cancer progression

The histone methyltransferase enhancer of zeste homolog 2 (EZH2) is overexpressed in a variety of malignancies including prostate cancer (PCa) and may play important roles in tumor progression. Gene copy number gains, enhanced transcription, and a few circRNAs have been reported to upregulate EZH2. It was not known whether EZH2 itself generates circRNAs that promote its own expression. We here report the identification of circEZH2^E2/E3 that is derived from exons 2 and 3 of the EZH2 gene and overexpressed in PCa. We show that circEZH2^E2/E3 functions as a dual inhibitor for both miR363 and miR708 that target the EZH2 3'UTR and CDS, respectively, resulting in the upregulation of EZH2 expression and hence the downregulation of EZH2-repressed genes (e.g., CDH1 and DAB2IP), and enhancement of PCa cell proliferation, migration, invasion, and xenograft PCa growth. Overexpression of circEZH2^E2/E3 is significantly correlated with higher tumor grade, tumor progression, and unfavorable progression-free and disease-specific survival in PCa patients. These findings show a novel autoenhancing EZH2-circEZH2^E2/E3 -miR363/miR708-EZH2 regulatory loop, by which circEZH2^E2/E3 plays important roles in PCa tumorigenesis and progression by upregulating EZH2, and may have potential diagnostic, prognostic, and therapeutic uses in PCa management.

CBX3 accelerates the malignant progression of glioblastoma multiforme by stabilizing EGFR expression

CBX3, also known as HP1γ, is a major isoform of heterochromatin protein 1, whose deregulation has been reported to promote the development of human cancers. However, the molecular mechanism of CBX3 in glioblastoma multiforme (GBM) are unclear. Our study reported the identification of CBX3 as a potential therapeutic target for GBM. Briefly, we found that, CBX3 is significantly upregulated in GBM and reduces patient survival. In addition, functional assays demonstrated that CBX3 significantly promote the proliferation, invasion and tumorigenesis of GBM cells in vitro and in vivo. Mechanistically, Erlotinib, a small molecule targeting epidermal growth factor receptor (EGFR) tyrosine kinase, was used to demonstrate that CBX3 direct the malignant progression of GBM are EGFR dependent. Previous studies have shown that PARK2(Parkin) and STUB1(Carboxy Terminus of Hsp70-Interacting Protein) are EGFR-specific E3 ligases. Notably, we verified that CBX3 directly suppressed PARK2 and STUB1 at the transcriptional level through its CD domain to reduce the ubiquitination of EGFR. Moreover, the CSD domain of CBX3 interacted with PARK2 and regulated its ubiquitination to further reduce its protein level. Collectively, these results revealed an unknown mechanism underlying the pathogenesis of GBM and confirmed that CBX3 is a promising therapeutic target.

The novel circSLC6A6/miR-1265/C2CD4A axis promotes colorectal cancer growth by suppressing p53 signaling pathway

Background

Colorectal cancer (CRC) is one of the most frequent malignancy and a leading cause of cancer-related deaths. Therefore, further researches are required to identify novel and more effective diagnoses and to identify molecular targets in treatment of CRC.

Methods

C2CD4A expression in CRC tissues and cell lines was detected by qRT-PCR and western blot. The biological functions of C2CD4A were performed both in vitro and in vivo. Western blot, cDNA array, IP-MS, Co-immunoprecipitation assay, and Ubiquitination assay were used to analyze the interaction between C2CD4A and p53. Bioinformatics analysis, FISH, RNA sequencing, luciferase reporter assay, RNA immunoprecipitation, RNA pull-down and rescue experiments, were deployed to detect upstream regulation mechanism of C2CD4A.

Results

C2CD4A was elevated in CRC tissues compared with adjacent normal colorectal tissues. C2CD4A knockdown significantly promoted cell apoptosis and with inhibited proliferation in vitro, and tumorigenicity in vivo, whereas C2CD4A overexpression led to opposite effects. Moreover, circSLC6A6 was upregulated and shown to positively regulate C2CD4A expression via sponging miR-1265. Fundamentally, C2CD4A inhibited p53 signaling pathway through interacting with p53 and increasing its ubiquitination and degradation.

Conclusion

Our results identified that circSLC6A6/miR-1265/C2CD4A axis, which was involved in CRC via the p53 signaling pathway, may serve as a therapeutic target for CRC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02126-y.

Rediscovering potential molecular targets for glioma therapy through the analysis of the cell of origin, microenvironment, and metabolism

Gliomas are the most common type of malignant brain tumors. Despite significant medical advances, gliomas remain incurable and are associated with high mortality. Although numerous biomarkers of diagnostic value have been identified and significant progress in the prognosis of the outcome has been made, the treatment has not been parallelly improved during the last three decades. This review summarizes and discusses three aspects of recent discoveries related to glioma, with the objective to highlight the advantages of glioma-specific drugs targeting the cell of origin, microenvironment, and metabolism. Given the heterogeneous nature of gliomas, various cell populations have been implicated as likely sources of the tumor. Depending on the mutation(s) acquired by the cells, it is believed that neuronal stem/progenitor cells, oligodendrocyte progenitor cells, mature neurons, and glial cells can initiate cell transformation into a malignant phenotype. The level of tumorigenicity appears to be inversely correlated with the maturation of a given cell population. The microenvironment of gliomas includes non-cancer cells such as immune cells, fibroblasts, and cells of blood vessels, as well as secreted molecules and the extracellular matrix, and all these components play a vital role during tumor initiation and progression. We will discuss in detail how the tumor microenvironment can stimulate and drive the transformation of non-tumor cell populations into tumor-supporting cells or glioma cells. Metabolic reprogramming is a key feature of gliomas and is thought to reflect the adaptation to the increased nutritional requirements of tumor cell proliferation, growth, and survival. Mutations in the IDH gene can shape metabolic reprogramming and may generate some vulnerabilities in glioma cells, such as abnormal lipid metabolism and sensitivity to endoplasmic reticulum stress (ERS). We will analyze the prominent metabolic features of malignant gliomas and the key pathways regulating glioma metabolism. This review is intended to provide a conceptual background for the development of glioma therapies based on the properties of tumor cell populations, microenvironment, and metabolism.

Competing Endogenous RNA Networks in Glioma

Gliomas are the most common and malignant primary brain tumors. Various hallmarks of glioma, including sustained proliferation, migration, invasion, heterogeneity, radio- and chemo-resistance, contribute to the dismal prognosis of patients with high-grade glioma. Dysregulation of cancer driver genes is a leading cause for these glioma hallmarks. In recent years, a new mechanism of post-transcriptional gene regulation was proposed, i.e., "competing endogenous RNA (ceRNA)." Long non-coding RNAs, circular RNAs, and transcribed pseudogenes act as ceRNAs to regulate the expression of related genes by sponging the shared microRNAs. Moreover, coding RNA can also exert a regulatory role, independent of its protein coding function, through the ceRNA mechanism. In the latest glioma research, various studies have reported that dysregulation of certain ceRNA regulatory networks (ceRNETs) accounts for the abnormal expression of cancer driver genes and the establishment of glioma hallmarks. These achievements open up new avenues to better understand the hidden aspects of gliomas and provide new biomarkers and potential efficient targets for glioma treatment. In this review, we summarize the existing knowledge about the concept and logic of ceRNET and highlight the emerging roles of some recently found ceRNETs in glioma progression.

Long noncoding RNA DLGAP1-AS1 promotes the progression of glioma by regulating the miR-1297/EZH2 axis

Dysregulated lncRNAs have been implicated in a plethora of tumors, including glioma. One such oncogenic lncRNAs that has been reported in several cancers is the lncRNA DLGAP1 antisense RNA 1 (DLGAP1-AS1). This study seeks to characterize the expression of DLGAP1-AS1 in glioma tissues, which we found to be raised in both glioma samples and cell lines. Functional experiments revealed that DLGAP1-AS1 promoted in vitro glioma cell invasion, migration and proliferation. DLGAP1-AS1 was found to function as a miR-1297 sponge, based on information from luciferase reporter assays, RNA pull-down assays and publicly available online databases. miR-1297 was in turn found to functionally target EZH2. DLGAP1-AS1 modulated EZH2 expressions through miR-1297 sponging. Glioma progression appears to be supported DLGAP1-AS1 -promoted activation of the miR-1297/EZH2 axis. The components of this axis may function as therapeutic targets for glioma.

Circ_0004771 Accelerates Cell Carcinogenic Phenotypes via Suppressing miR-1253-Mediated DDAH1 Inhibition in Breast Cancer

Background

Circ_0004771 was demonstrated to mediate cell growth promotion and apoptosis suppression in breast cancer (BC). Herein, the precise functions and mechanism of circ_0004771 in the biological property of BC cells were investigated.

Methods

The expression of circ_0004771, microRNA (miR)-1253 and dimethylarginine dimethylaminohydrolase 1 (DDAH1) mRNA was analyzed using quantitative real-time polymerase chain reaction. The proliferation, apoptosis, migration, invasion, adhesion, Western blot and in vivo tumorigenesis assays were employed to evaluate the roles of circ_0004771 and DDAH1 in BC tumorigenesis. The interaction between miR-1253 and circ_0004771 or DDAH1 was validated by dual-luciferase reporter, pull-down and RNA immunoprecipitation (RIP) assay. Exosomes were isolated by Exoquick-TC^® methods, and qualified using Nanosight™ technology and Western blot.

Results

Circ_0004771 or DDAH1 expression was elevated in BC, and silencing either of them suppressed cell malignant phenotypes, thus impeding BC progression. Importantly, circ_0004771 up-regulation attenuated the anticancer action of DDAH1-knockdown in BC. Additionally, we confirmed that circ_0004771 functioned as a sponge of miR-1253 to up-regulate DDAH1 expression. Moreover, xenograft assay exhibited that circ_0004771 knockdown also hindered tumor growth in vivo via regulating DDAH1 and miR-1253. Besides that, it was found that circ_0004771 was packaged into exosomes isolated from the serum of BC.

Conclusion

Circ_0004771 accelerated cell carcinogenic phenotypes via up-regulating DDAH1 expression through absorbing miR-1253 in BC. Besides, circ_0004771 was packaged into exosomes isolated from the serum of BC. All these findings suggested a promising molecular target for BC treatment.

circ_0082375 promotes the progression of glioma by regulating Wnt7B

Circular RNAs contribute to the progression of glioma. However, the biological role and underlying mechanism of circ_0082375 in glioma remain unclear. Quantitative real-time PCR and Western blot assay were used to evaluate the expression levels of circ_0082375, microRNA-485-5p, and Wnt family member 7B (Wnt7B). The overall survival of glioma patients was estimated by the Kaplan–Meier curve. Cell proliferation, apoptosis, invasion, and migration were detected by cell counting kit-8, 5-ethynyl-2 -deoxyuridine (EdU) staining, flow cytometry, and transwell assays, respectively. Glucose level and lactate production were determined using glucose and lactate assay kits. In vitro angiogenesis assay was used to evaluate the angiogenesis of glioma cells. The interaction between microRNA (miR)-485-5p and circ_0082375 or Wnt family member 7B (Wnt7B) was verified by dual-luciferase reporter and RNA immunoprecipitation assays. A xenograft model was used to verify the function of circ_0082375 in vivo. circ_0082375 was upregulated in glioma tissues, and it was closely related to the prognosis of glioma patients. circ_0082375 knockdown suppressed cell proliferation, migration, invasion, angiogenesis, glycolysis, and epithelial-mesenchymal transition (EMT), and promoted cell apoptosis in glioma cells. irc_0082375 was a sponge of miR-485-5p, which directly targeted Wnt7B. Knockdown of circ_0082375 inhibited the malignancy, angiogenesis, and glycolysis of glioma cells in vitro by sponging miR-485-5p. Besides, circ_0082375 knockdown hampered the growth of glioma growth by regulating the miR-485-5p/Wnt7B axis in vivo. Altogether, circ_0082375 regulated miR-485-5p/Wnt7B axis to promote the malignancy, angiogenesis, and glycolysis of glioma cells, thereby contributing to the progression of glioma.

Lidocaine inhibits glioma cell proliferation, migration and invasion by modulating the circEZH2/miR-181b-5p pathway

BACKGROUND

Lidocaine is well known as a local anesthetic that has been reported to play an antitumor role in numerous cancers, including glioma. Circular RNAs (circRNAs) play multiple biological roles in cancers. The aim of this study was to determine the effects of lidocaine in glioma in vitro and in vivo and explore functional mechanisms.

METHODS

The effects of lidocaine on glioma progression were investigated by cell proliferation, migration and invasion using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, colony formation assay and transwell assay. The expression of CD133 and glial fibrillary acidic protein (GFAP) was quantified by western blot to assess cell differentiation. The expression of circEZH2 and miR-181b-5p was detected by a quantitative real-time PCR (qRT-PCR). The target relationship between circEZH2 and miR-181b-5p was verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. The effect of lidocaine on tumor growth in vivo was investigated by establishing Xenograft models.

RESULTS

Lidocaine inhibited proliferation, migration, invasion and induced differentiation of glioma cells in vitro. Lidocaine suppressed the expression of circEZH2, and circEZH2 was highly expressed in glioma tissues and cells. CircEZH2 overexpression partly inhibited the function of lidocaine. CircEZH2 was a sponge of miR-181b-5p, and miR-181b-5p was downregulated in glioma tissues and cells. Besides, miR-181b-5p restoration reversed the effects of circEZH2 overexpression to repress the malignant behaviors of glioma cells. In addition, lidocaine mediated the circEZH2/miR-181b-5p axis to inhibit tumor growth in vivo.

CONCLUSION

Lidocaine suppressed glioma progression by modulating the circEZH2/miR-181b-5p pathway.

Circ_0008532 promotes bladder cancer progression by regulation of the miR-155-5p/miR-330-5p/MTGR1 axis

BACKGROUND

Circular RNAs (circRNAs) have been associated with bladder cancer (BC), but the specific underlying molecular mechanism of their association with BC development has not been fully explored.

METHODS

Levels of Circ_0008532, MTGR1 and miR-155-5p/miR-330-5p in bladder cancer cell lines and tissues were determined with quantitative real-time PCR and western blotting assays. In vitro and in vivo assays were performed to investigate the function of circ_0008532 in tumorigenesis in bladder cancer cells. The relationships of Circ_0008532, MTGR1 and miR-155-5p/miR-330-5p were predicted using bioinformatic tools and verified by RNA-FISH, RIP and luciferase assays. The effects of circ_0008532 on the Notch signaling pathway were determined by GSEA analysis and western blotting assay.

RESULTS

We found that circ_0008532 is upregulated in BC cell lines and tissues. Moreover, overexpression of circ_0008532 promotes, and silencing of circ_0008532 inhibits the capacity for invasive in BC cells. In addition, circ_0008532 can directly interact with miR-155-5p and miR-330-5p as an miRNA sponge which mediates the expression of the miR-155-5p/miR-330-5p target gene MTGR1 and downstream Notch signaling.

CONCLUSIONS

Circ_0008532 may act as an oncogene in BC through a novel circ_0008532/miR-155-5p, miR-330-5p /MTGR1/Notch pathway axis, which in turn may provide potential biomarkers and a therapeutic target for the management of bladder cancer.