Circular PVT1: an oncogenic non-coding RNA with emerging clinical importance

circPVT1 promotes silica-induced epithelial-mesenchymal transition by modulating the miR-497-5p/TCF3 axis

Epithelial-mesenchymal transition (EMT) is a vital pathological feature of silica-induced pulmonary fibrosis. However, whether circRNA is involved in the process remains unclear. The present study aimed to investigate the role of circPVT1 in the silica-induced EMT and the underlying mechanisms. We found that an elevated expression of circPVT1 promoted EMT and enhanced the migratory capacity of silica-treated epithelial cells. The isolation of cytoplasmic and nuclear separation assay showed that circPVT1 was predominantly expressed in the cytoplasm. RNA immunoprecipitation assay and RNA pull-down experiment indicated that cytoplasmic-localized circPVT1 was capable of binding to miR-497-5p. Furthermore, we found that miR-497-5p attenuated the silica-induced EMT process by targeting transcription factor 3 (TCF3), an E-cadherin transcriptional repressor, in the silica-treated epithelial cells. Collectively, these results reveal a novel role of the circPVT1/miR-497-5p/TCF3 axis in the silica-induced EMT process in lung epithelial cells. Once validated, this finding may provide a potential theoretical basis for the development of interventions and treatments for pulmonary fibrosis.

Biological role of long non-coding RNA KCNQ1OT1 in cancer progression

Long non-coding RNAs (lncRNAs) are a type of RNAs that are more than 200 nucleotides without protein-coding potential. In recent years, more and more attention has been paid to the role of lncRNAs in cancer pathogenesis. LncRNA KCNQ1 overlapping transcript 1 (KCNQ1OT1) is located on chromosome 11p15.5 with a total length of 91 kb and is highly expressed in various malignancies, which is closely related to tumor growth, lymph node metastasis, survival cycle and recurrence rate. In addition, KCNQ1OT1 is involved in the regulation of PI3K/AKT and Wnt/β-catenin signaling pathways. In this review, the mechanism and related progress of KCNQ1OT1 in different cancers were reviewed. It was found that KCNQ1OT1 can stabilize mRNA expression through sponging miRNA, which not only induced tumor cell proliferation, migration, invasion, drug resistance, epithelial-mesenchymal transition (EMT) and inhibited cell apoptosis in vitro, but also promoted tumor growth and metastasis in vivo. Therefore, as a new biomarker and therapeutic target, KCNQ1OT1 has broad prospects for the diagnosis and treatment of different cancers.

Proliferation-promoting roles of linear and circular PVT1 are independent of their ability to bind miRNAs in B-cell lymphoma

Plasmacytoma Variant Translocation 1 (PVT1) is a long non-coding RNA located at 8q24.21 immediately downstream of MYC. Both the linear and circular PVT1 transcripts contribute to cancer pathogenesis by binding microRNAs. However, little is known about their roles in B-cell lymphoma. Here we studied their expression patterns, role in growth, and ability to bind miRNAs in B-cell lymphoma. Linear PVT1 transcripts were downregulated in B-cell cell lymphoma lines compared to germinal center B cells, while circPVT1 levels were increased. Two Hodgkin lymphoma cell lines had a homozygous deletion including the 5' region of the PVT1 locus, resulting in a complete lack of circPVT1 and 5' linear PVT1 transcripts. Inhibition of both linear and circular PVT1 decreased growth of Burkitt lymphoma, while the effects on Hodgkin lymphoma and diffuse large B cell lymphoma were less pronounced. Overexpression of circPVT1 promoted growth of B-cell lymphoma lacking or having low endogenous circPVT1 levels. Contrary to other types of cancer, linear and circular PVT1 transcripts did not interact with miRNAs in B-cell lymphoma. Overall, we showed an opposite expression pattern of linear and circular PVT1 in B-cell lymphoma. Their effect on growth was independent of their ability to bind miRNAs.

Salivaomics to decode non-coding RNAs in oral cancer. A narrative review

Oral cancer is the most debilitating disease which affects the orderly life of a human. With so much advancement in research and technology, the average life expectancy of an individual with oral cancer appears to be about 5 years. The changing trend in incidence of oral cancer among young individuals and women without tobacco habits are ascending. Non habit related oral cancer are taking centre stage and multiple factors which induce complex biology are associated in such scenarios. To decipher the aetiology and to understand the process, these cancerous conditions are to be studied at molecular level. Saliva, the most non-invasively obtained body fluid are assessed for biomarkers exclusively in liquid biopsy. This fluid gives a huge platform to study number of molecules associated with oral cancer. Non coding RNAs are transcripts with no protein coding function. They are gaining more importance in recent times. Long noncoding RNA, microRNA are major types of noncoding transcriptome that influences in progression of oral cancer. They seem to play an important role in health and disease. Apart from these, circulating tumour cells, exosomes, extracellular vesicles, antigens and other proteins can be studied from saliva. This review is aimed to update the knowledge on current biomarkers in saliva associated with oral cancer and their epigenetic role in disease progression as well recent advances in detecting these markers to identify the stage of the disease, which will help in deciding the treatment protocol.

Identification of LncPVT1 and CircPVT1 as prognostic biomarkers in human colorectal polyps

LncPVT1 and CircPVT1 are isoforms for the PVT1 gene and are associated with cancer progression and carcinogenesis. Our study investigated the expression of LncPVT1 and CircPVT1 in colon adenoma polyps. 40 tissues of colorectal polyps and 40 normal-adjacent tissues (NATs) were taken. The expression of LncPVT1 and CircPVT1 was evaluated through qRael-Time PCR. The relation between expression and features of clinicopathological was explored. The ceRNA network was constructed by LncPVT1 and CircPVT1 and predicted miRNAs and miRNAs targets. Further, hub nodes in this network were determined using the cytoHubba package. Over-expressed LncPVT1 and CircPVT1 were differentiated in polyp and NATs. The expression level of LncPVT1 and CircPVT1 were significantly higher in adenoma polyps than in hyperplastic polyps. The area under the curve of the ROC estimate for the LncPVT1 and CircPVT1 was 0.74 and 0.77, respectively. A positive correlation was observed between the LncPVT1 expression and CircPVT1. Three miRNAs, including hsa-miR-484, hsa-miR-24-3p, hsa-miR-423-5p, and CircPVT1, were detected as ceRNA hub nodes. In this study, expression profiles of LncPVT1 and CircPVT1 were significantly higher in precancerous polyps. In addition, based on our in silico analysis, LncPVT1, CircPVT1/miR-484, miR-24-3p, miR-423-5p/PLAGL2 axis might be involved in colon cancer development. LncPVT1 and CircPVT1 can be prescribed as warning problems as potential prognostic biomarkers in patients with pre-CRC colon polyps.

Targeting signaling pathways in osteosarcoma: Mechanisms and clinical studies

Osteosarcoma (OS) is a highly prevalent bone malignancy among adolescents, accounting for 40% of all primary malignant bone tumors. Neoadjuvant chemotherapy combined with limb-preserving surgery has effectively reduced patient disability and mortality, but pulmonary metastases and OS cells' resistance to chemotherapeutic agents are pressing challenges in the clinical management of OS. There has been an urgent need to identify new biomarkers for OS to develop specific targeted therapies. Recently, the continued advancements in genomic analysis have contributed to the identification of clinically significant molecular biomarkers for diagnosing OS, acting as therapeutic targets, and predicting prognosis. Additionally, the contemporary molecular classifications have revealed that the signaling pathways, including Wnt/β-catenin, PI3K/AKT/mTOR, JAK/STAT3, Hippo, Notch, PD-1/PD-L1, MAPK, and NF-κB, have an integral role in OS onset, progression, metastasis, and treatment response. These molecular classifications and biological markers have created new avenues for more accurate OS diagnosis and relevant treatment. We herein present a review of the recent findings for the modulatory role of signaling pathways as possible biological markers and treatment targets for OS. This review also discusses current OS therapeutic approaches, including signaling pathway-based therapies developed over the past decade. Additionally, the review covers the signaling targets involved in the curative effects of traditional Chinese medicines in the context of expression regulation of relevant genes and proteins through the signaling pathways to inhibit OS cell growth. These findings are expected to provide directions for integrating genomic, molecular, and clinical profiles to enhance OS diagnosis and treatment.

CircRNA PVT1 modulated cell migration and invasion through Epithelial-Mesenchymal Transition (EMT) mediation in gastric cancer through miR-423-5p/Smad3 pathway

Background

Gastric cancer (GC) progression is related with gene regulations.

Objectives

This study explored underlying regulatory axis of circRNA PVT1 (circPVT1) in GC.

Methods

GC cell lines were detected for circPVT1 expression with the normal mucous epithelial cell GES-1 as control. After regulation of circPVT1, miR-423-5p and SMAD3 expression through transfection, CCK8 evaluated the cell viability, Transwell measured the migratory and invasive capability of cells. Luciferase verified the paired bindings between miR-423-5p and CircPVT1 or SMAD3. The functions of CircPVT1/miR-423-5p/SMAD3 were evaluated using RT-PCR, CCK8, Transwell assays. Western blot analyzed EMT-related proteins and phosphorylation of Smad3 in GC cells. Immunofluorescence method was used to evaluate the EMT-related proteins as well.

Results

CircPVT1 displayed higher expression in GC cells and knockdown led to decrease in cell growth, invasion and migration. CircPVT1 was targeted by miR-423-5p as a ceRNA of SMAD3. miR-423-5p upregulation suppressed both cicRNA PVT1 and SMAD3 in GC cells. Decrease in SMAD3 expression suppressed CircPVT1 by releasing miR-423-5p in cells, inhibiting cell growth, invasion and migration and suppressing the EMT process.

Conclusion

CircPVT1 modulated cell growth, invasion and migration through EMT mediation in gastric cancer through miR-423-5p/Smad3 pathway.

Myc-mediated circular RNA circMcph1/miR-370-3p/Irak2 axis is a progressive regulator in hepatic fibrosis

AIMS

Treating hepatic fibrosis (HF) is a major challenge worldwide. However, the biological functions and regulatory mechanisms of circular RNAs (circRNAs) remain unclear in HF. The present study aimed to elucidate the novel role of circMcph1 in HF.

MAIN METHODS

HF mouse model was established by injecting CCl₄ intraperitoneally and validated using hematoxylin and eosin staining, immunohistochemistry, and serological tests in vivo. RAW264.7 cells were treated with lipopolysaccharide (LPS) and interferon-γ (IFN-γ) in vitro inflammatory damage model. Gel electrophoresis, DNA sequencing, RNase R and actinomycin D treatment, random 6 primers and oligo dT primers assay, nuclear and cytoplasmic fractionation assay, and fluorescence in situ hybridization were performed to identify the characteristics of circMcph1. Functional assays such as ELISA, flow cytometry, and adeno-associated virus administration in vivo and liposome delivery gene therapy in vitro were used to determine the functional effects of circMcph1/miR-370-3p/interleukin-1 receptor-associated kinase 2 (Irak2) axis. Mechanistic assays such as luciferase reporter analysis, and chromatin immunoprecipitation revealed the molecular mechanism of the Myc/circMcph1/miR-370-3p/Irak2 axis in HF.

KEY FINDINGS

CircMcph1 expression was upregulated in liver tissues and primary Kupffer cells of CCl₄-induced HF mice, as well as in LPS and IFN-γ-treated RAW264.7 cells. Knockdown of circMcph1 ameliorated liver fibrogenesis and inflammatory damage in HF mice and reduced the inflammatory response in LPS and IFN-γ-treated RAW264.7 cells. Mechanically, circMcph1 mediated by Myc regulated the expression of Irak2 by sponging miR-370-3p in HF.

SIGNIFICANCE

The study findings suggested that the Myc/circMcph1/miR-370-3p/Irak2 axis might be a novel identifier and therapeutic target for HF.

Noncoding RNA PVT1 in osteosarcoma: The roles of lncRNA PVT1 and circPVT1

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and teenagers and is characterized by high malignant potential, rapid disease progression and high disability and mortality rates. Recently, noncoding RNAs (ncRNAs) have attracted the attention of many scholars due to their major regulatory roles in gene expression. Among them, lncRNA PVT1 and circPVT1 encoded by the PVT1 gene have been the focus of many studies; they are upregulated in OS, and abundant evidence indicates that lncRNA PVT1 and circPVT1 play key roles in the occurrence and development of OS. This review summarizes the mechanisms of action of lncRNA PVT1 and circPVT1 in regulating apoptosis, proliferation, glycolysis, invasion, migration and epithelial–mesenchymal transition (EMT) in OS and discusses their clinical applications in diagnosis, prognosis determination and drug resistance treatment, with the aim of helping researchers better understand the regulatory roles of lncRNA PVT1 and circPVT1 in OS progression and providing a theoretical basis for the development of early screening and accurate targeted treatment strategies and prognostic biomarkers for OS based on lncRNA PVT1 and circPVT1.

CircPVT1 facilitates the progression of oral squamous cell carcinoma by regulating miR-143-3p/SLC7A11 axis through MAPK signaling pathway

Oral squamous cell carcinoma (OSCC) is a common malignant tumor occurring in the oral cavity. Circular RNAs (circRNAs) play a crucial regulatory role in many cancers. This study aimed to investigate the function of circRNA plasmacytoma variant translocation 1 (PVT1) (circPVT1) in OSCC and its potential mechanism. The levels of circPVT1, solute carrier family 7 member 11 (SLC7A11), and microRNA-143-3p (miR-143-3p) were examined by quantitative real-time PCR (qRT-PCR) or western blot assay. Cell proliferation, apoptosis, migration, and invasion were evaluated by Cell Counting Kit-8 (CCK-8), colony formation assay, flow cytometry, and transwell assay. The levels of apoptosis and proliferation-related proteins were examined by western blot. The targeting relationship between miR-143-3p and circPVT1 or SLC7A11 was verified by dual-luciferase reporter, RNA immunoprecipitation (RIP), and RNA pull-down assays. The levels of mitogen-activated protein kinase (MAPK) pathway-related proteins were measured by western blot. Xenograft assay was used to assess tumor growth in vivo. CircPVT1 and SLC7A11 were upregulated, while miR-143-3p was downregulated in OSCC tissues and cells. Silencing of circPVT1 or SLC7A11 suppressed proliferation, migration, and invasion and promoted apoptosis in OSCC cells. CircPVT1 upregulated SLC7A11 expression via sponging miR-143-3p. SLC7A11 upregulation alleviated the effect of circPVT1 knockdown on OSCC cell progression. Besides, circPVT1 modulated MAPK signaling pathway by regulating miR-143-3p. Moreover, circPVT1 knockdown inhibited tumor growth in vivo. Knockdown of circPVT1 impeded OSCC progression via the miR-143-3p/SLC7A11 axis through MAPK signaling pathway.

CircPVT1: a pivotal circular node intersecting Long Non-Coding-PVT1 and c-MYC oncogenic signals

The role of circular RNAs in oncogenesis has begun to be widely studied in recent years, due to the significant impact that these molecules have in disease pathogenesis, as well as their potential for the future of innovative therapies. Moreover, due to their characteristically circular shape, circular RNAs are very resistant molecules to RNA degradation whose levels are easily assessed in body fluids. Accordingly, they represent an opportunity for the discovery of new diagnostic and prognostic markers in a wide range of diseases. Among circular RNAs, circPVT1 is a rather peculiar one that originates from the circularization of the exon 2 of the PVT1 gene that encodes a pro-tumorigenic long non-coding RNA named lncPVT1. There are a few examples of circular RNAs that derive from a locus producing another non-coding RNA. Despite their apparent transcriptional independence, which occurs using two different promoters, a possible synergistic effect in tumorigenesis cannot be excluded considering that both have been reported to correlate with the oncogenic phenotype. This complex mechanism of regulation appears to also be controlled by c-MYC. Indeed, the PVT1 locus is located only 53 Kb downstream c-MYC gene, a well-known oncogene that regulates the expression levels of about 15% of all genes. Here, we review circPVT1 origin and biogenesis highlighting the most important mechanisms through which it plays a fundamental role in oncogenesis, such as the well-known sponge activity on microRNAs, as well as its paradigmatic interactome link with lncPVT1 and c-MYC expression.

Circular RNA Plasmacytoma Variant Translocation 1 (CircPVT1) knockdown ameliorates hypoxia-induced bladder fibrosis by regulating the miR-203/Suppressor of Cytokine Signaling 3 (SOCS3) signaling axis

The effects of circular RNAs (circRNAs) on bladder outlet obstruction (BOO)-induced hypertrophy and fibrogenesis in rats and hypoxia-induced bladder smooth muscle cell (BSMC) fibrosis remain unclear. This study aimed to determine the regulatory role of circRNAs in the phenotypic changes in BSMCs in BOO-induced rats.circRNAmicroarray and real-time PCR were used to explore differentiated expressed circRNAs. Bioinformatics analyses and dual-luciferase reporter were performed to identify the targets for circRNA PVT1 (circPVT1). BOO was performed to establish a bladder fibrosis animal model. The circPVT1 and suppressor of cytokine signaling 3 (SOCS3) expression levels were upregulated (p = 0.0061 and 0.0328, respectively), whereas the microRNA-203a (miR-203) level was downregulated in rats with bladder remodeling (p=0.0085). Bioinformatics analyses and dual-luciferase reporter assay results confirmed that circPVT1 sponges miR-203 and that the latter targets the 3'-untranslated region of SOCS3. Additionally, circPVT1 knockdown alleviated BOO-induced bladder hypertrophy and fibrogenesis. Furthermore, hypoxia was induced in BSMCs to establish a cell model of bladder fibrosis. Hypoxia induction in BSMCs resulted in upregulated circPVT1 and SOCS3 levels (p = 0.0052) and downregulated miR-203 levels. Transfection with circPVT1 and SOCS3 shRNA ameliorated hypoxia-induced transforming growth factor-β (TGF-β1), TGFβR1, α-smooth muscle actin, fibrotic growth factor, extracellular matrix subtypes, BSMC proliferation, and apoptosis-associated cell injury, whereas co-transfection with miR-203 inhibitor counteracted the effect of circPVT1 shRNA on these phenotypes.These findings revealed a novel circRNA regulator of BOO-associated bladder wall remodeling and hypoxia-induced phenotypic changes in BMSCs by targeting the miR-203-SOCS3 signaling axis.

A Concise Review on the Role of CircPVT1 in Tumorigenesis, Drug Sensitivity, and Cancer Prognosis

CircPVT1 (hsa_circ_0001821) is a cancer-related circular RNA (circRNA) that originated from a genomic locus on chromosome 8q24. This locus has been previously found to encode the oncogenic long non-coding RNA PVT1. Expression of this circRNA has been found to be upregulated in diverse neoplastic conditions. CircPVT1 acts as a sponge for miR-125a, miR-125b, miR-124-3p, miR-30a-5p, miR-205-5p, miR-423-5p, miR-526b, miR-137, miR-145-5p, miR-497, miR-30d/e, miR-455-5p, miR-29a-3p, miR-204-5p, miR-149, miR-106a-5p, miR-377, miR-3666, miR-203, and miR-199a-5p. Moreover, it can regulate the activities of PI3K/AKT, Wnt5a/Ror2, E2F2, and HIF-1α. Upregulation of circPVT1 has been correlated with decreased survival of patients with different cancer types. In the current review, we explain the oncogenic impact of circPVT1 in different tissues based on evidence from in vitro, in vivo, and clinical investigations.

PRNCR1: a long non-coding RNA with a pivotal oncogenic role in cancer

Long non-coding RNAs (lncRNAs) have been gaining importance in the field of cancer research in recent years. PRNCR1 (prostate cancer-associated non-coding RNA1) is a 12.7 kb, intron-less lncRNA found to play an oncogenic role in malignancy of diverse organs including prostate, breast, lung, oral cavity, colon and rectum. Single-nucleotide polymorphisms (SNPs) of PRNCR1 locus have been found to be associated with cancer susceptibility in different populations. In this review, an attempt has been made for the first time to summarize all sorts of available data on PRNCR1 to date from relevant databases (GeneCard, LncExpDB, Ensembl genome browser, and PubMed). As functional roles of PRNCR1, miRNA (microRNA) sponging was mostly highlighted in the pathogenesis of different cancer; in addition, an association of the lncRNA with chromatin-modifying complex to enhance androgen receptor-mediated gene transcription was reported in prostate cancer. Diagnostic and prognostic importance of PRNCR1 was found in some malignancies suggesting potency of the lncRNA to serve as a clinical biomarker. For PRNCR1 SNPs, although cancer susceptibility of the risk alleles/genotypes was reported in different populations, majorities of the findings were not replicated and underlying molecular mechanisms remained unexplored. Therapeutic implication of PRNCR1 was not studied well and future research may come up in this direction for intervening novel strategies to fight against cancer.

Prognostic and clinicopathological value of circPVT1 in human cancers: A meta-analysis

BACKGROUND

Circular RNA PVT1 (circPVT1) is significantly upregulated in various human cancers and is related to poor clinical outcome of cancer patients. However, the prognostic and clinicopathological value of circPVT1 in diverse human cancers remains controversial and inconclusive.

AIM

The objective of our study is to evaluate the prognostic and clinicopathological role of circPVT1 for cancer patients.

METHODS AND RESULTS

PubMed, Embase, Web of Science, and Cochrane Library were searched for eligible studies by October 1, 2020. The correlation between circPVT1 expression, and overall survival (OS) and clinical parameters was assessed by pooled hazard ratios (HRs) and odds ratios (ORs) with 95% confidence intervals (CIs). Subgroup analyses, heterogeneity, and publication bias were conducted to further enhance reliability. Twelve studies (1282 patients) were selected for this meta-analysis, including 11 on prognosis and 10 on clinicopathological parameters. Elevated expression of circPVT1 was associated with a worse OS in cancer patients (HR, 2.009; 95% CI, 1.667-2.408, 1.892; P < .001). For clinicopathological value, upregulation of circPVT1 was closely related to poor clinical parameters lymph node metastasis (OR = 2.019; 95% CI, 1.026-3.976; P = .042; I2  = 77.5%; PH  = 0.000), late clinical stage (OR = 3.594; 95% CI, 1.828-7.065; P < .001; I2  = 71.7%; PH  = 0.001), distant metastasis (OR = 4.598; 95% CI, 1.411-14.988; P = .011; I2  = 78.1%; PH  = 0.001), and chemoresistant (OR = 6.400; 95% CI, 2.107-19.441; P = .001; I2  = 49.6%; PH  = 0.159).

CONCLUSION

High expression of circPVT1 is correlated with unfavorable prognosis of cancer patients, indicating that circPVT1 can function as a potential prognostic biomarker in human cancer.

Clinicopathologic and prognostic roles of circular RNA plasmacytoma variant translocation 1 in various cancers

OBJECTIVE

To explore the clinicopathologic and prognostic significance of circular RNA plasmacytoma variant translocation 1 (circPVT1) in various cancers.

METHODS

Several databases were searched for eligible studies published before March 01, 2021. The pooled odds ratios (ORs) with 95% confidence interval (95% CI) were calculated to assess the association between circPVT1 expression and prognostic outcomes of tumor including age, gender, clinical stage, tumor size, metastasis and overall survival. Begg's funnel plots and Egger's test were used to evaluate the publication bias. The robustness of our results was assessed using sensitivity analysis.

RESULTS

Ten studies comprising a total of 878 patients with cancer were included in this meta-analysis. The results showed that the high expression of circPVT1 was significantly related to clinical stage (OR=3.44, 95% CI: 2.40-4.94, P<0.05), tumor size (OR=2.29, 95% CI: 1.38-3.79, P<0.05), metastasis (OR=2.97, 95% CI: 2.06-4.28, p<0.05) and overall survival of cancer (OR=3.30, 95% CI: 2.26-4.84, p<0.05), but not associated with age and gender of patients with tumor. No publication bias was found.

CONCLUSIONS

High expression of circPVT1 may predict an advanced clinical stage and poor prognosis of tumor, suggesting that circPVT1 may serve as a potential prognostic marker in cancers.

CircPVT1 promotes gallbladder cancer growth by sponging miR-339-3p and regulates MCL-1 expression

Circular RNAs (circRNAs) have been implicated in modulating biological processes in some tumors. However, the contributions and molecular mechanisms of circRNAs to gallbladder cancer (GBC) remain largely unknown. In the present study, our results showed circPVT1 expression was significantly upregulated in GBC tissues and cells. Higher circPVT1 expression was correlated with lymph node metastasis, advanced TNM stage, and poor overall survival (OS) in patients with GBC. Subsequently, knockdown of circPVT1 significantly impeded GBC cell proliferation, migration, invasion, while induced cell apoptosis in vitro. However, upregulated circPVT1 had the opposite effects. In vivo, we also demonstrated that knockdown of circPVT1 inhibited tumor growth. Furthermore, we confirmed that circPVT1 could regulate Myeloid cell leukemia-1 (MCL-1) expression by sponging to miR-339-3p, which affected tumor progression in GBC cells. In summary, our findings indicated that circPVT1 may serve as a promising prognostic marker and therapeutic target for GBC.

Increased levels of circulating circular RNA (hsa_circ_0013587) may serve as a novel biomarker for pancreatic cancer

Aim: Circular RNA can serve as a biomarker for early diagnosis of pancreatic cancer. Materials & methods: Analyzed the expression of various differentially expressed circular RNAs in the pancreatic cancer tissues by gene chip and identified the expression of hsa_circ_0013587 in pancreatic cancer cells, tissues and plasma by quantitative reverse transcription PCR (qRT-PCR). Results: Hsa_circ_0013587 was highly expressed in the pancreatic cancer tissues, cell lines and plasma samples from patients with pancreatic cancer. Notably, hsa_circ_0013587 was upregulated in pancreatic cancer patients with later clinical stages III-IV as compared with those detected in early clinical stages I-II. Conclusion: A high expression of hsa_circ_0013587 may serve as a novel diagnostic and therapeutic biomarker for pancreatic cancer.

Circ-EGFR Functions as an Inhibitory Factor in the Malignant Progression of Glioma by Regulating the miR-183-5p/TUSC2 Axis

Circular RNAs (circRNAs) have pivotal functions in regulating diverse biological processes of human tumors, including glioma. Herein, a novel circRNA epidermal growth factor receptor (circ-EGFR, hsa_circ_0080223) was researched in glioma. The molecular expression levels were analyzed via quantitative real-time polymerase chain reaction (qRT-PCR). Cell Counting Kit-8 (CCK-8) and colony formation assays were conducted to assess cell proliferation. Apoptosis was analyzed using flow cytometry. Cell migration and invasion were examined via transwell assay. Interaction relations between targets were verified using dual-luciferase reporter assay. Tumor Suppressor Candidate 2 (TUSC2) protein expression was examined by Western blot. In vivo experiment was performed by establishing xenograft model in mice. The qRT-PCR showed the downregulation of circ-EGFR and TUSC2 but the upregulation of microRNA-183-5p (miR-183-5p) in glioma samples. In vitro assays revealed that circ-EGFR overexpression induced the repression of cell proliferation, migration, and invasion but the promotion of apoptosis. Circ-EGFR was identified as a sponge of miR-183-5p and circ-EGFR-mediated glioma progression inhibition was abolished by miR-183-5p downregulation. Additionally, miR-183-5p targeted TUSC2 and miR-183-5p inhibitor impeded the development of glioma by upregulating the expression of TUSC2. Furthermore, circ-EGFR could regulate the TUSC2 level by sponging miR-183-5p. Glioma growth in vivo was also reduced by circ-EGFR via targeting the miR-183-5p/TUSC2 axis. Altogether, our results suggested that circ-EGFR inhibited the malignant progression of glioma by regulating the levels of miR-183-5p and TUSC2. Circ-EGFR may be a useful therapeutic target to antagonize the glioma progression.

Elevated Circular RNA PVT1 Promotes Eutopic Endometrial Cell Proliferation and Invasion of Adenomyosis via miR-145/Talin1 Axis

Several theories on the origin of adenomyosis (ADS) have been proposed, of which the most widely accepted is the fundamental pathogenic role of uterine eutopic endometrium. Emerging evidence suggests that circular RNAs participate in the multiple tumorgenesis. The vital importance of circular RNA PVT1 (circPVT1) in the pathological progress like malignancies has been well documented. Nevertheless, its underlying correlation with ADS remains elusive yet. The purpose of this study was to investigate the expression pattern, regulatory effect, and internal mechanism of circPVT1 in ADS. qRT-PCR was performed to detect the relative mRNA expression of circPVT1, miR-145, and Talin1 in ADS endometrial tissue and cells. The protein level of Talin1 was measured by Western blot and immunochemistry. Immunofluorescence was used to identify the primary endometrial epithelial and stromal cells. circPVT1 knockdown in vitro was achieved by transfecting with specific lentivirus vector CCK-8, and colony formation assays were utilized to assess cell proliferation; meanwhile, the transwell assay was employed for evaluating cell invasion ability. By conducting bioinformatics, dual-luciferase reporter assay, or RNA immunoprecipitation (RIP) experiment, the interaction between miR-145 and circPVT1 or Talin1 was verified. Rescue experiments further determined the regulatory effect of circPVT1/miR-145/Talin1 axis. We found both circPVT1 and Talin1 were markedly upregulated in ADS endometrial tissue and cells, whereas miR-145 was decreased. Elevated expression of circPVT1 was closely related to the severity of dysmenorrhea, menorrhagia, and uterine enlargement of patients with ADS. Knockdown of circPVT1 inhibited adenomyotic epithelial and stromal cell proliferation and invasion. Further mechanistic experiments revealed that circPVT1 negatively regulated miR-145 through serving as a molecular sponge. And the facilitating effect of circPVT1 was partially reversed by miR-145. Talin1 was demonstrated to be a down target of miR-145 and indirectly affected by circPVT1. Our findings unveiled that enhanced circPVT1 may be involved in the pathogenesis of ADS via stimulating endometrial cell proliferation and invasion. The establishment of circPVT1/miR-145/Talin1 pathway might present a novel therapeutic insight for ADS.

Circular PVT1 regulates cell proliferation and invasion via miR-149-5p/FOXM1 axis in ovarian cancer

Long non-coding RNA plasmacytoma variant translocation 1 (PVT1) is a dysregulated gene in malignancy and is associated with oncogenesis. In this study, we found PVT1 RNA was an ovarian specific expressing gene, and overexpressed in multiple cancer types, including ovarian cancer (OV). Higher expression levels of PVT1 are related to shorter survival time in OV patients, especially in patients with advanced stage and grade. Recent studies indicated circular PVT1 also had an important role in cancer progression, whose roles in OV remain unclear. Knockdown of circular PVT1 significantly suppressed OV cell proliferation, migration and invasion. Bioinformatics analysis demonstrated that circular PVT1 was involved in regulating angiogenesis, osteoblast differentiation, regulation of cell growth, type B pancreatic cell proliferation, negative regulation of apoptotic process, phospholipid homeostasis, regulation of neurogenesis, definitive hemopoiesis, cell migration, regulation of glucose metabolic process, central nervous system development and type 2 immune response. Our data showed miR-149-5p targeted FOXM1, which was regulated by circular PVT1. Forkhead Box M1 (FOXM1) expression in ovarian cancer exhibited high level when compared with normal tissues, and had relation with relatively poor survival. FOXM1 promoted cell viability and reduced FOXM1 could rescue circular influence of circular PVT1-caused carcinoma induction. In conclusion, circular PVT1 increased FOXM1 level via binding to miR-149-5p and thus affected ovarian cancer cell viability and migration.

CircPVT1 Regulates Cell Proliferation, Apoptosis and Glycolysis in Hepatocellular Carcinoma via miR-377/TRIM23 Axis

Background

Recent studies reported that circular RNAs (circRNAs) exert essential functions in hepatocellular carcinoma (HCC) progression. However, the expression profile and function of circular RNA PVT1 (circPVT1) in HCC are not fully addressed. Thus, we aimed to probe into the function of circPVT1 in HCC development.

Methods

The levels of circPVT1, microRNA-377 (miR-377) and transcripts encoding tripartite motif containing 23 (TRIM23) were determined by qRT-PCR. The stability and localization of circPVT1 were examined by RNase R digestion assay and subcellular fraction assay, respectively. Cell proliferation and apoptosis were evaluated by MTT assay and flow cytometry analysis, respectively. The relationship between miR-377 and circPVT1 or TRIM23 was determined by dual-luciferase reporter assay and RNA immunoprecipitation (RIP). The protein expression of TRIM23 was measured by Western blot. The glycolysis level was assessed by specific kits and Seahorse Extracellular Flux Analyzer XF96. The function of circPVT1 in vivo was investigated in a murine xenograft model.

Results

CircPVT1 and TRIM23 levels were elevated, while miR-377 was decreased in HCC. CircPVT1 knockdown restrained proliferation and glycolysis, but enhanced apoptosis in HCC cells. CircPVT1 could bind to miR-377 and inhibition of miR-377 restored circPVT1 knockdown-mediated effect on HCC cells. TRIM23 was certified as a target of miR-377, and TRIM23 upregulation overturned the influence of miR-377 upregulation or circPVT1 silence on HCC progression. Moreover, circPVT1 knockdown restrained tumor growth in HCC in vivo.

Conclusion

CircPVT1 aggravated the progression of HCC by upregulating TRIM23 via sponging miR-377.

Regulation of microRNA-497 expression in human cancer

MicroRNAs (miRNAs/miRs) are a type of non-coding single-stranded RNA, with a length of ~22 nt, which are encoded by endogenous genes and are involved in the post-transcriptional regulation of gene expression in animals and plants. Studies have demonstrated that miRNAs play an important role in the occurrence, development, metastasis, diagnosis and treatment of cancer. In recent years, miR-497 has been identified as one of the key miRNAs in a variety of cancer types and has been shown to be downregulated in a variety of solid tumors. However, the regulation of miR-497 expression involves a complex network, which is affected by several factors. The aim of the present review was to summarize the mechanism of regulation of miR-497 expression at the pre-transcriptional and transcriptional levels in cancer, as well as the role of miR-497 expression imbalance in cancer diagnosis, treatment and prognosis. The regulatory mechanisms of miR-497 expression may aid in our understanding of the causes of miR-497 expression imbalance and provide a reference value for further research on the diagnosis and treatment of cancer.

Emerging Roles and Potential Biological Value of CircRNA in Osteosarcoma

Circular RNAs (circRNAs) are endogenous noncoding RNAs that are widely found in eukaryotic cells. They have been found to play a vital biological role in the development of human diseases. At present, circRNAs have been involved in the pathogenesis, diagnosis, and targeted treatment of multiple tumors. This article reviews the research progress of circRNAs in osteosarcoma (OSA) in recent years. The potential connection between circRNAs and OSA cell proliferation, apoptosis, metastasis, and chemotherapy sensitivity or resistance, as well as clinical values, is described in this review. Their categories and functions are generally summarized to facilitate a better understanding of OSA pathogenesis, and findings suggest novel circRNA-based methods may be used to investigate OSA and provide an outlook for viable biomarkers and therapeutic targets.

Knockdown of PVT1 Suppresses Colorectal Cancer Progression by Regulating MiR-106b-5p/FJX1 Axis

Purpose

Long non-coding RNA plasmacytoma variant translocation 1 (PVT1) has been revealed to involve in the progression of CRC. However, the precise mechanisms of PVT1 in action remain unclear.

Methods

The expression of PVT1, microRNA-106b-5p (miR-106b-5p) and four jointed box 1 (FJX1) was measured using quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot, respectively. Cell proliferation was investigated by 3-(4,5)-dimethylthiahiazo (−z-y1)-3,5-di-phenytetrazoliumromide assay. Transwell assay was used to determine cell migration and invasion. The correlation between miR-106b-5p and PVT1 or FJX1 was confirmed using luciferase reporter assay. The effects of PVT1 in vivo were assessed using mice xenograft model.

Results

PVT1 was up-regulated in CRC tissues and cell lines, especially in CRC tissues with high-grade, and highly expressed PVT1 predicted worse prognosis. Functional experiments demonstrated that PVT1 deletion inhibited CRC cell proliferation, migration and invasion in vitro and suppressed tumor growth in vivo. MiR-106b-5p was confirmed to be a target of PVT1, and inhibition of miR-106b-5p reversed the inhibitory effects of PVT1 knockdown on CRC cell malignant phenotypes. In addition, we found miR-106b-5p directly targeted FJX1, and miR-106b-5p-mediated inhibition on CRC cell proliferation, migration and invasion was attenuated by FJX1 up-regulation. Importantly, it was also proved that PVT1 could indirectly regulate FJX1 expression via targeting miR-106b-5p.

Conclusion

Knockdown of PVT1 impaired cell proliferation, migration and invasion in CRCs via regulating miR-106b-5p/FJX1 axis, which provided a novel insight into the development of therapeutic strategies for CRC patients.

Non-coding RNAs, guardians of the p53 galaxy

The TP53 gene is arguably the most important tumor suppressor gene known, contributing multifaceted roles to the process of tumor development. Its protein product p53, is a crucial sequence-specific transcription factor which regulates the expression of a large network of protein-coding genes, as well as thousands of noncoding RNAs (ncRNAs), notably microRNAs and long ncRNAs (lncRNAs). Through a variety of direct and indirect mechanisms, ncRNAs in turn modulate p53 levels and activity. Here the numbers of studies are steadily building which link the contributions of dysregulated ncRNAs to tumorigenesis via their participation throughout the p53 regulatory network. In this review, we will examine how the principal forms of ncRNAs, namely microRNAs, lncRNAs and circular RNAs (circRNAs) function as either effectors or regulators amongst the diversity of p53's cellular responses. We first discuss the more recently discovered connections between miRNAs and p53 signaling before focusing on the remarkable diversity of crosstalk evident between lncRNAs and p53, and subsequently, developing reports linking circRNAs to p53. Highlighted throughout the review are the mechanistic impacts of dysregulated ncRNAs on p53 functions as well as the possible prognostic implications of these interactions. We also describe the emerging connections between ncRNAs and the often-perplexing functions of mutant p53. Finally, in the context of p53 therapeutic approaches, we describe some of the challenges in ncRNA research and their potential for translation.

The Circular RNA-miRNA Axis: A Special RNA Signature Regulatory Transcriptome as a Potential Biomarker for OSCC

Oral squamous cell carcinoma (OSCC) is a highly recurrent form of cancer arising from the oral epithelium, which is the result of mutational change due to etiological factors such as tobacco, smoking, chewing of areca nuts, and alcohol consumption. OSCC occurrence has been observed to be prevalent in different regions of Pacific countries and in most Asian countries. Despite the accessibility of the oral cavity, OSCC is diagnosed at an extremely late stage of pathogenic tumor node metastasis pTNM (III–IV), resulting in a poor prognosis for the individual. Therefore, it is important to make definitive, early, and efficient diagnoses. Owing to the development of omic-natured studies, the presence of proteins, transcribed elements, metabolic products, and even microflora detected in saliva helps us to select biomarkers, which is an especially exciting potential because of the availability and the non-invasive nature of sample collection. Since the discovery of circular RNA (circRNA) by Sanger sequencing, it has been reported to play a pivotal role in several human diseases, including cancer. circRNA functions as a microRNA (miRNA) sponge in the regulation of mRNA expression, forming the circRNA-miRNA regulatory axis. In the case of OSCC, overexpression of different circRNAs exhibits both tumor-progressive and tumor-suppressive effects.

Functional and Clinical Impact of CircRNAs in Oral Cancer

The increasing number of recently published works regarding the role of circular RNAs (circRNAs) in oral cancer highlights the key contribution of this novel class of endogenous noncoding RNAs as regulators of critical signaling pathways and their clinical value as novel biomarkers. This review summarizes and puts into context the existing literature in order to clarify the relevance of circRNAs as novel mediators of oral cancer pathogenesis as well as their potential usefulness as predictors of clinical outcome and response to therapy in this disease.

Linear and circular PVT1 in hematological malignancies and immune response: two faces of the same coin

Non coding RNAs (ncRNAs) have emerged as regulators of human carcinogenesis by affecting the expression of key tumor suppressor genes and oncogenes. They are divided into short and long ncRNAs, according to their length. Circular RNAs (circRNAs) are included in the second group and were recently discovered as being originated by back-splicing, joining either single or multiple exons, or exons with retained introns. The human Plasmacytoma Variant Translocation 1 (PVT1) gene maps on the long arm of chromosome 8 (8q24) and encodes for 52 ncRNAs variants, including 26 linear and 26 circular isoforms, and 6 microRNAs. PVT1 genomic locus is 54 Kb downstream to MYC and several interactions have been described among these two genes, including a feedback regulatory mechanism. MYC-independent functions of PVT1/circPVT1 have been also reported, especially in the regulation of immune responses. We here review and discuss the role of both PVT1 and circPVT1 in the hematopoietic system. No information is currently available concerning their transforming ability in hematopoietic cells. However, present literature supports their cooperation with a more aggressive and/or undifferentiated cell phenotype, thus contributing to cancer progression. PVT1/circPVT1 upregulation through genomic amplification or rearrangements and/or increased transcription, provides a proliferative advantage to malignant cells in acute myeloid leukemia, acute promyelocytic leukemia, Burkitt lymphoma, multiple myeloma (linear PVT1) and acute lymphoblastic leukemia (circPVT1). In addition, PVT1 and circPVT1 regulate immune responses: the overexpression of the linear form in myeloid derived suppressor cells induced immune tolerance in preclinical tumor models and circPVT1 showed immunosuppressive properties in myeloid and lymphoid cell subsets. Overall, these recent data on PVT1 and circPVT1 functions in hematological malignancies and immune responses reflect two faces of the same coin: involvement in cancer progression by promoting a more aggressive phenotype of malignant cells and negative regulation of the immune system as a novel potential therapy-resistance mechanism.

circPVT1 Facilitates Invasion and Metastasis by Regulating miR-205-5p/c-FLIP Axis in Osteosarcoma

Background

As a key subtype of non-coding RNAs, circular RNA (circRNA) has been well documented to play a key role in the tumorigenesis of osteosarcoma (OS). circPVT1 was revealed to participate in the progression of multiple human tumors; however, the roles of circPVT1 in OS invasion and metastasis and its potential mechanisms remain elusive.

Methods

RNA expression in OS tissues and cells was examined by qRT-PCR, protein expression was measured by Western blot. circPVT1 knockdown in vitro was achieved by transfecting OS cells with specific siRNAs. OS cell proliferation was assessed via CCK-8 and colony formation assays. OS cell migration and invasion were evaluated by transwell assay. Interaction between miR-205-5p and circPVT1 or c-FLIP was validated through dual-luciferase reporter assay. Rescue experiments were performed to explore the regulatory net among circPVT1, miR-205-5p and c-FLIP in OS progression in vitro.

Results

circPVT1 and c-FLIP were highly expressed, while miR-205-5p was lowly expressed in OS tissues and cell lines. Knockdown of circPVT1 repressed cell proliferation, migration and invasion via inhibiting epithelial–mesenchymal transition (EMT) in OS. circPVT1 functioned as a sponge of miR-205-5p, and c-FLIP was targeted by miR-205-5p in OS cells. Furthermore, circPVT1 indirectly regulated c-FLIP expression through competitively binding to miR-205-5p. Inhibition of miR-205-5p or overexpression of c-FLIP abolished the effects of si-circPVT1 on cell proliferation, migration and invasion.

Conclusion

Our study demonstrated circPVT1 functions as a sponge for miR-205-5p to promote c-FLIP expression, thereby enhancing EMT and inducing OS invasion and metastasis in vitro, implying that circPVT1 might be a potential therapeutic target for further clinical therapy of OS.

Long noncoding RNA PVT1 acts as an oncogenic driver in human pan-cancer

Increasing evidence indicates that long noncoding RNAs (lncRNAs) play pivotal roles during tumorigenesis in multiple types of cancers. However, little is known about the exact role of plasmacytoma variant translocation 1 (PVT1) in human pan-cancer. Here, we report the oncogenic role and function of PVT1 in human pan-cancer, including breast cancer. The expression of PVT1 in human tumor tissues and nontumor tissues, the upstream regulation of PVT1 and the relationship between its expression and prognosis and chemoresistance were examined by using The Cancer Genome Atlas data. PVT1 expression is higher in human cancer tissues compared with adjacent noncancerous tissues, and patients with high levels of PVT1 expression usually have tumors with a higher TNM stage. High PVT1 expression is also associated with worse disease outcomes in patients with cancer. Hypomethylation and transcription factor binding in the PVT1 promoter locus activates its transcriptional expression. Guilt by association analysis revealed that PVT1 may be involved in processes associated with tumorigenesis. Moreover, PVT1 may trigger chemoresistance in human cancer. These results indicated that PVT1 may act as an oncogenic driver and maybe a potential therapeutic target in human cancer.

Circular RNA differential expression in blood cell populations and exploration of circRNA deregulation in pediatric acute lymphoblastic leukemia

Circular RNAs (circRNAs) are abundantly expressed in the haematopoietic compartment, but knowledge on their diversity among blood cell types is still limited. Nevertheless, emerging data indicate an array of circRNA functions exerted through interactions with other RNAs and proteins, by translation into peptides, and circRNA involvement as regulatory molecules in many biological processes and cancer mechanisms. Interestingly, the role of specific circRNAs in leukemogenesis has been disclosed by a few studies, mostly in acute myeloid leukemia. In this study, circRNA expression in B-cells, T-cells and monocytes of healthy subjects is described, including putative new circRNA genes. Expression comparison considered 6,228 circRNAs and highlighted cell population-specific expression and exon usage patterns. Differential expression has been confirmed by qRT-PCR for circRNAs specific of B-cells (circPAX5, circAFF3, circIL4R, and circSETBP1) or T-cells (circIKZF1, circTNIK, circTXK, and circFBXW7), and for circRNAs from intronic (circBCL2) and intergenic regions that were overexpressed in lymphocytes. Starting from this resource of circRNA expression in mature blood cell populations, targeted examination identified striking and generalized upregulated expression of circPAX5, circPVT1 and circHIPK3 in pediatric B-precursor acute lymphoblastic leukemia, and disclosed circRNAs with variable expression across cytogenetic subtypes.