Circular RNA CircEYA3 induces energy production to promote pancreatic ductal adenocarcinoma progression through the miR-1294/c-Myc axis

Integration of single-nucleus and exosome RNA sequencing dissected inter-cellular communication and biomarkers in pancreatic ductal adenocarcinoma

Background

Mounting evidence underscores the importance of cell communication within the tumor microenvironment, which is pivotal in tumor proliferation, invasion, and metastasis. Exosomes play a crucial role in cell-to-cell communication. Although single-cell RNA sequencing (scRNA-seq) provides insights into individual cell transcriptional characteristics, it falls short of comprehensively capturing exosome-mediated intercellular communication.

Method

We analyzed Pancreatic Ductal Adenocarcinoma (PDAC) tissues, separating supernatant and precipitate for exosome purification and single-cell nucleus suspension. We then constructed Single-nucleus RNA sequencing (snRNA-seq) and small RNA-seq libraries from these components. Our bioinformatic analysis integrated these sequences with ligand-receptor analysis and public miRNA data to map the cell communication network.

Results

We established intercellular communication networks using bioinformatic analysis to track exosome miRNA effects and ligand-receptor pairs. Significantly, hsa-miR-1293 emerged as a prognostic biomarker for pancreatic cancer, linked to immune evasion, increased myeloid-derived suppressor cells, and poorer prognosis. Targeting this miRNA may enhance anti-tumor immunity and improve outcomes.

Conclusion

Our study offers a novel approach to constructing intercellular communication networks using snRNA-seq and exosome-small RNA sequencing. By integrating miRNA tracing with ligand-receptor analysis, we illuminate the complex interactions in the pancreatic cancer microenvironment, highlighting the pivotal role of miRNAs and identifying potential biomarkers and therapeutic targets.

Biological functions of circRNA in regulating the hallmarks of gastrointestinal cancer (Review)

Circular RNA (circRNA) was first observed in the cytoplasm of eukaryotic cells in 1979, but it was not characterized in detail until 2012, when high‑throughput sequencing technology was more advanced and available. Consequently, the mechanism of circRNA formation and its biological function have been progressively elucidated by researchers. circRNA is abundant in eukaryotic cells and exhibits a certain degree of organization, timing and disease‑specificity. Additionally, it is poorly degradable, meeting the characteristics of an ideal clinical biomarker. In the present review, the recent research progress of circRNAs in digestive tract malignant tumors was primarily discussed. This included the roles, biological functions and clinical significance of circRNA, providing references for its research value and clinical potential in gastrointestinal cancer.

CircEYA3 aggravates intervertebral disc degeneration through the miR-196a-5p/EBF1 axis and NF-κB signaling

Intervertebral disc degeneration (IDD) is a well-established cause of disability, and extensive evidence has identified the important role played by regulatory noncoding RNAs, specifically circular RNAs (circRNAs) and microRNAs (miRNAs), in the progression of IDD. To elucidate the molecular mechanism underlying IDD, we established a circRNA/miRNA/mRNA network in IDD through standardized analyses of all expression matrices. Our studies confirmed the differential expression of the transcription factors early B-cell factor 1 (EBF1), circEYA3, and miR-196a-5p in the nucleus pulposus (NP) tissues of controls and IDD patients. Cell proliferation, apoptosis, and extracellular mechanisms of degradation in NP cells (NPC) are mediated by circEYA3. MiR-196a-5p is a direct target of circEYA3 and EBF1. Functional analysis showed that miR-196a-5p reversed the effects of circEYA3 and EBF1 on ECM degradation, apoptosis, and proliferation in NPCs. EBF1 regulates the nuclear factor kappa beta (NF-кB) signalling pathway by activating the IKKβ promoter region. This study demonstrates that circEYA3 plays an important role in exacerbating the progression of IDD by modulating the NF-κB signalling pathway through regulation of the miR196a-5p/EBF1 axis. Consequently, a novel molecular mechanism underlying IDD development was elucidated, thereby identifying a potential therapeutic target for future exploration.

Hypoxia-Challenged Pancreatic Adenocarcinoma Cell-Derived Exosomal circR3HCC1L Drives Tumor Growth Via Upregulating PKM2 Through Sequestering miR-873-5p

Pancreatic adenocarcinoma (PAAD) is a fatal disease with poor survival. Increasing evidence show that hypoxia-induced exosomes are associated with cancer progression. Here, we aimed to investigate the function of hsa_circ_0007678 (circR3HCC1L) and hypoxic PAAD cell-derived exosomal circR3HCC1L in PAAD progression. Through the exoRBase 2.0 database, we screened for a circular RNA circR3HCC1L related to PAAD. Changes of circR3HCC1L in PAAD samples and cells were analyzed with real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation, migration, invasion were analyzed by colony formation, cell counting, and transwell assays. Measurements of glucose uptake and lactate production were done using corresponding kits. Several protein levels were detected by western blotting. The regulation mechanism of circR3HCC1L was verified by dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assays. Exosomes were separated by differential ultracentrifugation. Animal experiments were used to verify the function of hypoxia-derived exosomal circR3HCC1L. CircR3HCC1L was upregulated in PAAD samples and hypoxic PAAD cells. Knockdown of circR3HCC1L decreased hypoxia-driven PAAD cell proliferation, migration, invasion, and glycolysis. Hypoxic PAAD cell-derived exosomes had higher levels of circR3HCC1L, hypoxic PAAD cell-derived exosomal circR3HCC1L promoted normoxic cancer cell malignant transformation and glycolysis in vitro and xenograft tumor growth in mouse models in vivo. Mechanistically, circR3HCC1L regulated pyruvate kinase M2 (PKM2) expression via sponging miR-873-5p. Also, PKM2 overexpression or miR-873-5p silencing offset circR3HCC1L knockdown-mediated effects on hypoxia-challenged PAAD cell malignant transformation and glycolysis. Hypoxic PAAD cell-derived exosomal circR3HCC1L facilitated PAAD progression through the miR-873-5p/PKM2 axis, highlighting the contribution of hypoxic PAAD cell-derived exosomal circR3HCC1L in PAAD.

LncRNA CCAT1 participates in pancreatic ductal adenocarcinoma progression by forming a positive feedback loop with c-Myc

Long noncoding RNAs (lncRNAs) play fundamental roles in cancer development; however, the underlying mechanisms for a large proportion of lncRNAs in pancreatic ductal adenocarcinoma (PDAC) have not been elucidated. The expression of colon cancer-associated transcript-1 (CCAT1) in PDAC specimens and cell lines was measured by quantitative real-time polymerase chain reaction (qRT-PCR). The function of CCAT1 was examined in vitro and in vivo. The interactions among CCAT1, miR-24-3p and c-Myc were determined by bioinformatics analysis, RNA immunoprecipitation (RIP), dual-luciferase reporter assay, and rescue experiments. CCAT1 was significantly increased in PDAC, positively correlated with PDAC progression and predicted a worse prognosis. Furthermore, CCAT1 enhanced Adenosine triphosphate (ATP) production to facilitate PDAC cell proliferation, colony formation and motility in vitro and tumor growth in vivo. CCAT1 may serve as an miR-24-3p sponge, thereby counteracting its repression by c-Myc expression. Reciprocally, c-Myc may act as a transcription factor to alter CCAT1 expression by directly targeting its promoter region, thus forming a positive feedback loop with CCAT1. Collectively, these results demonstrate that a positive feedback loop of CCAT1/miR-24-3p/c-Myc is involved in PDAC development, which may serve as a biomarker and therapeutic target for PDAC.

Circular RNA circTMEM59 inhibits progression of pancreatic ductal adenocarcinoma by targeting miR-147b/SOCS1: An in vitro study

Purpose

This study aimed to detect the role and mechanism of circTMEM59 in pancreatic ductal adenocarcinoma (PDAC).

Methods

66 paired PDAC tissues and normal samples were harvested from patients diagnosed and undergoing pancreatic cancer surgery in our hospital. The expression of circTMEM59 in PDAC tissues and cell lines was detected. Based on bioinformatics information, the circTMEM59 mimics, miR-147b mimics, miR-147b inhibitor and si-suppressor of cytokine signaling 1 (SOCS1) were transfected into PDAC cells. The expression levels of circTMEM59, miR-147b and SOCS1 were detected by quantitative real-time polymerase chain reaction (qRT-PCR). RNA interaction was confirmed by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Cell invasion and proliferation were evaluated by Transwell and Cell Counting Kit-8 (CCK-8) assays. The protein expression was detected by Western blot.

Results

CircTMEM59 was confirmed to be downregulated in PDAC tumor tissues and cells. Low expression of circTMEM59 was closely correlated with the short survival time and poor clinicopathological characteristics. By up-regulating the expression of circTMEM59 in PDAC cells, cell proliferation, invasion and epithelial-mesenchymal transition (EMT) were inhibited. More importantly, miR-147b could be sponged by circTMEM59, and knockdown of miR-147b inhibited progression of PDAC cells. Further study revealed that SOCS1 was targeted by miR-147b. SOCS1 expression was negatively related to miR-147b expression and positively related to circTMEM59 expression in PDAC tissues. Upregulated miR-147b and downregulated SOCS1 could rescue the effects of circTMEM59 on cell proliferation, EMT and invasion.

Conclusion

Our data indicated that circTMEM59 inhibited cell proliferation, invasion and EMT of PDAC by regulating miR-147b/SOCS1 axis.

A Circulating Panel of circRNA Biomarkers for the Noninvasive and Early Detection of Pancreatic Ductal Adenocarcinoma

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is one of the most fatal malignancies. Delayed manifestation of symptoms and lack of specific diagnostic markers lead patients being diagnosed with PDAC at advanced stages. This study aimed to develop a circular RNA (circRNA)-based biomarker panel to facilitate noninvasive and early detection of PDAC.

METHODS

A systematic genome-wide discovery of circRNAs overexpressed in patients with PDAC was conducted. Subsequently, validation of the candidate markers in the primary tumors from patients with PDAC was performed, followed by their translation into a plasma-based liquid biopsy assay by analyzing 2 independent clinical cohorts of patients with PDAC and nondisease controls. The performance of the circRNA panel was assessed in conjunction with the plasma levels of cancer antigen 19-9 for the early detection of PDAC.

RESULTS

Initially, a panel of 10 circRNA candidates was identified during the discovery phase. Subsequently, the panel was reduced to 5 circRNAs in the liquid biopsy-based assay, which robustly identified patients with PDAC and distinguished between early-stage (stage I/II) and late-stage (stage III/IV) disease. The areas under the curve of this diagnostic panel for the detection of early-stage PDAC were 0.83 and 0.81 in the training and validation cohorts, respectively. Moreover, when this panel was combined with cancer antigen 19-9 levels, the diagnostic performance for identifying patients with PDAC improved remarkably (area under the curve, 0.94) for patients in the validation cohort. Furthermore, the circRNA panel could also efficiently identify patients with PDAC (area under the curve, 0.85) who were otherwise deemed clinically cancer antigen 19-9-negative (<37 U/mL).

CONCLUSIONS

A circRNA-based biomarker panel with a robust noninvasive diagnostic potential for identifying patients with early-stage PDAC was developed.

Circular RNAs in pancreatic cancer progression

Pancreatic cancer (PC), typically diagnosed at relatively advanced stages with poor prognosis, is a dominant cause of cancer-related deaths worldwide. Accumulating evidence demonstrates that circular RNAs (circRNAs) are abnormally expressed in diverse tumors and affect tumorigenesis and progression. In this article, we examine the roles of circRNAs in regulation of PC progression. Additionally, circRNAs enriched in exosomes could be transferred among PC cells to modulate malignancy. Characterization of regulatory mechanisms involving circRNAs in general and PC specifically will enable earlier detection and potential development of therapeutic strategies.

CircNEK6 promotes the progression of pancreatic ductal adenocarcinoma through targeting miR-503/CCND1 axis

PURPOSE

The present study aimed to reveal the function and underlying molecular mechanism of circRNA NIMA related kinase 6 (circNEK6) in promoting the progression of pancreatic ductal adenocarcinoma (PDAC).

METHODS

The differentially expressed circRNAs in three paired PDAC tissues and adjacent tissues were identified by RNA sequencing. CircNEK6 was screened out to further explore its relationship with the prognosis of PDAC patients. The target microRNAs and mRNAs of circNEK6 were analyzed through online databases and detected by quantitative real-time polymerase chain reaction. Cell counting kit-8 assay, clone formation assay, transwell assay, flow cytometry and western blot were used to explore the function of circNEK6 on the biological behaviors of PDAC cells. The in vivo antitumor effect of circNEK6 silencing on PDAC was investigated by nude mouse xenograft models.

RESULTS

203 differentially expressed circRNAs including circNEK6 were identified between paired PDAC tissues and adjacent tissues, and the expression level of circNEK6 was negatively correlated with the prognosis of PDAC patients. The results of in vitro experiments showed that knockdown of circNEK6 repressed the proliferation, migration and invasion, but induced the apoptosis of PDAC cells. Moreover, circNEK6 silencing inhibited tumor growth and prolonged the survival time of PDAC-bearing mice. Mechanistically, miR-503/cyclin D1 (CCND1) axis was predicted and confirmed as the target of circNEK6.

CONCLUSIONS

CircNEK6 serves as a competing endogenous RNA of CCND1 by absorbing miR-503, which might be treated as a novel and potential target for PDAC treatment.

Exosome-transmitted hsa_circ_0012634 suppresses pancreatic ductal adenocarcinoma progression through regulating miR-147b/HIPK2 axis

Circular RNA (circRNA) has been confirmed to play a vital role in pancreatic ductal adenocarcinoma (PDAC) progression. However, the function and regulatory mechanism of hsa_circ_0012634 in PDAC progression remain unclear. Quantitative real-time PCR was used to measure the expression of hsa_circ_0012634, microRNA (miR)-147b and homeodomain interacting protein kinase 2 (HIPK2). Cell function was assessed by cell counting kit 8 assay, EdU assay, colony formation assay and flow cytometry. Glucose uptake and lactate production were evaluated to determine cell glycolysis ability. Protein expression was examined by western blot analysis. RNA interaction was confirmed by RNA pull-down assay and dual-luciferase reporter assay. Exosomes were isolated from serums and cell culture supernatant using ultracentrifugation and identified by transmission electron microscopy. Animal experiments were conducted using nude mice. Hsa_circ_0012634 was downregulated in PDAC tissues and cells, and its overexpression suppressed PDAC cell proliferation, glycolysis and enhanced apoptosis. MiR-147b was targeted by hsa_circ_0012634, and its inhibitors repressed PDAC cell growth and glycolysis. HIPK2 could be targeted by miR-147b, and hsa_circ_0012634 regulated miR-147b/HIPK2 to suppress PDAC cell progression. Hsa_circ_0012634 was lowly expressed in serum exosomes of PDAC patients. Exosomal hsa_circ_0012634 inhibited PDAC cell growth and glycolysis in vitro, as well as tumorigenesis in vivo. Exosomal hsa_circ_0012634 restrained PDAC progression via the miR-147b/HIPK2 pathway, confirming that hsa_circ_0012634 might serve as a diagnosis and treatment biomarker for PDAC.

Circ_0114581 promotes osteogenic differentiation of BMSCs via the MiR-155-5p/HNRNPA3 axis

Osteoporosis (OP) is a common metabolic bone disease characterized by deterioration of bone tissue structure, reduction of bone mass, and susceptibility to fracture. More and new suitable therapeutic targets need to be discovered. The purpose of this study was to explore the ceRNA mechanisms of circRNAs involved in osteoporosis. In this study, a competing endogenous RNA (ceRNA) regulatory network was obtained through the application of OP-related high throughput data sets. Our results provided evidence that HNRNPA3 was involved in the regulation of osteogenic differentiation in BMSCs. Testing of human bone tissues and ovariectomized mice bones proved that its expression level was negatively correlated with OP. The utilization of miRNA mimic or inhibitor proved that miR-155-5p could negatively regulate the expression of HNRNPA3, while overexpression of hsa_circ_0114581 with a circRNA overexpression vector proved that hsa_circ_0114581 could indirectly promoted HNRNPA3 expression and osteogenic differentiation by sponging hsa-miR-155-5p. A serious of luciferase reporter assay experiments further verified the binding site between miR-155-5p and HNRNPA3 and the binding site between miR-155-5p and hsa_circ_0114581. This study proved that the hsa_circ_0114581/hsa-miR-155-5p/HNRNPA3 axis was related with OP. The results reveal valuable insights into the pathogenesis of OP and noncoding RNA markers that may have a treatment role and will help to provide hypotheses for future studies.

Diagnostic and prognostic role of circRNAs in pancreatic cancer: a meta-analysis

Background

Circular RNAs (circRNAs) are types of endogenous noncoding RNAs produced by selective splicing that are expressed highly specifically in various organisms and tissues and have numerous clinical implications in the regulation of cancer development and progression. Since circRNA is resistant to digestion by ribonucleases and has a long half-life, there is increasing evidence that circRNA can be used as an ideal candidate biomarker for the early diagnosis and prognosis of tumors. In this study, we aimed to reveal the diagnostic and prognostic value of circRNA in human pancreatic cancer (PC).

Methods

A systematic search for publications from inception to 22 July 2022 was conducted on Embase, PubMed, Web of Science (WOS), and the Cochrane Library databases. Available studies that correlated circRNA expression in tissue or serum with the clinicopathological, diagnostic, and prognostic values of PC patients were enrolled. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to evaluate clinical pathological characteristics. Area under the curve (AUC), sensitivity, and specificity were adopted to assess diagnostic value. Hazard ratios (HRs) were utilized to assess disease-free survival (DFS) and overall survival (OS).

Results

This meta-analysis enrolled 32 eligible studies, including six on diagnosis and 21 on prognosis, which accounted for 2,396 cases from 245 references. For clinical parameters, high expression of carcinogenic circRNA was significantly associated with degree of differentiation (OR = 1.85, 95% CI = 1.47-2.34), TNM stage (OR = 0.46, 95% CI = 0.35-0.62), lymph node metastasis (OR = 0.39, 95% CI = 0.32-0.48), and distant metastasis (OR = 0.26, 95% CI = 0.13-0.51). As for clinical diagnostic utility, circRNA could discriminate patients with pancreatic cancer from controls, with an AUC of 0.86 (95% CI: 0.82-0.88), a relatively high sensitivity of 84%, and a specificity of 80% in tissue. In terms of prognostic significance, carcinogenic circRNA was correlated with poor OS (HR = 2.00, 95% CI: 1.76-2.26) and DFS (HR = 1.96, 95% CI: 1.47-2.62).

Conclusion

In summary, this study demonstrated that circRNA may act as a significant diagnostic and prognostic biomarker for pancreatic cancer.

Exosomal ERBB2IP contributes to tumor growth via elevating PSAT1 expression in non-small cell lung carcinoma

BACKGROUND

Both exosomes and circular RNAs (circRNAs) are involved in tumor growth. Hsa_circ_0001492 (circERBB2IP) has been reported to be overexpressed in plasma exosomes from patients with lung adenocarcinoma, but the biological role of exosomal circERBB2IP in non-small cell lung carcinoma (NSCLC) is indistinct.

METHODS

Exosomes isolated from serums and medium samples were validated by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and western blotting. Relative expression of circERBB2IP was detected by RT-qPCR. Loss-of-function was done to determine the effect of circERBB2IP on NSCLC cell proliferation and migration. Molecular mechanisms associated with circERBB2IP were predicted by bioinformatic analysis and validated by dual-luciferase reporter, RIP, and RNA pulldown assays. In vivo experiments were performed to identify the function of circERBB2IP in NSCLC.

RESULTS

We discovered that circERBB2IP expression was correlated with TNM grade, lymph node metastasis and tumor size of NSCLC patients. Upregulation of circERBB2IP was observed in exosomes derived from NSCLC patient's serum and circERBB2IP might be a potential diagnostic biomarker for NSCLC. CircERBB2IP was transmitted between carcinoma cells through exosomes. Knockdown of circERBB2IP lowered cell growth in mouse models and restrained NSCLC cell proliferation and migration. CircERBB2IP could mediate PSAT1 expression via sponging miR-5195-3p.

CONCLUSION

In conclusion, circERBB2IP may drive NSCLC growth by the miR-5195-3p/PSAT1 axis in NSCLC, shedding light on a diagnostic biomarker and therapeutic target for NSCLC.

Circ_0081054 facilitates melanoma development via sponging miR-637 and regulating RAB9A

BACKGROUND

Accumulating evidence announces that aberrantly expressed circRNAs were closely related to the development of human cancers. However, the role and mechanism of multiple circRNAs remain unclear. Our work aimed to disclose the functional role and mechanism of circ_0081054 in melanoma.

METHODS

Quantitative real-time polymerase chain reaction assay was utilized to detect circ_0081054, microRNA-637 (miR-637) and RAB9A (member RAS oncogene family) mRNA expression. Cell proliferative ability was evaluated via Cell Counting Kit-8 and colony formation assay. Cell invasion was assessed by using wound healing assay.

RESULTS

The significant upregulation of circ_0081054 was detected in melanoma tissues and cells. The proliferation, migration, glycolytic metabolism, and angiogenesis in melanoma cells were suppressed, while apoptosis was promoted following the silence of circ_0081054. In addition, circ_0081054 could target miR-637, and miR-637 inhibitor could reverse the effects of circ_0081054 deficiency. Furthermore, RAB9A was a target gene for miR-637 and RAB9A overexpression could reverse the effects of miR-637 overexpression. In addition, the deficiency of circ_0081054 hampered tumor growth in vivo. Moreover, circ_0081054 could regulate RAB9A expression by sponging miR-637.

CONCLUSION

All results indicated that circ_0081054 promoted the malignant behaviors of melanoma cells partly by regulating the miR-637/RAB9A molecular axis.

Downregulation of circ-STK39 suppresses pancreatic cancer progression by sponging mir-140-3p and regulating TRAM2-mediated epithelial-mesenchymal transition

BACKGROUND

Pancreatic cancer (PC) is amongst the most lethal gastrointestinal tumors, which is the seventh leading reason of cancer-related mortality worldwide. Previous studies have indicated that circular RNAs (circRNAs), which is a new type of endogenous noncoding RNA (ncRNA), can mediate tumor progression in diverse tumor types including PC. Whereas precise roles regarding circRNAs and their underlying regulatory mechanisms in PC remain unknown.

METHODS

In the current study, we employed next generation sequencing (NGS) to characterize abnormally expressed circRNAs among PC tissues. Next, we assessed expression levels of one identified circRNA, circ-STK39, in PC cell lines and tissues. Then, using bioinformatics analysis, luciferase reporter, Transwell migration, EdU and CCK-8 assays, we examined the regulatory mechanisms and targets of circ-STK39. Finally, our group explored the circ-STK39 role in PC tumor growth and metastasis in vivo.

RESULTS

Our team discovered that circ-STK39 expression increased in PC tissues and cells, suggesting that circ-STK39 may have a role in PC progression. Downregulation of circ-STK39 inhibited PC proliferation and migration. Bioinformatics and luciferase reporter outcomes demonstrated that TRAM2 and miR-140-3p were circ-STK39 downstream targets. TRAM2 overexpression reversed the miR-140-3p overexpression effects upon migration, proliferation and the epithelial-mesenchymal transition (EMT).

CONCLUSION

In this regard, we showed that circ-STK39 downregulation led to decreased migration, proliferation and the EMT of PC via the miR-140-3p/TRAM2 axis.

The function and mechanisms of action of circular RNAs in Urologic Cancer

Kidney, bladder, and prostate cancer are the three major tumor types of the urologic system that seriously threaten human health. Circular RNAs (CircRNAs), special non-coding RNAs with a stabile structure and a unique back-splicing loop-forming ability, have received recent scientific attention. CircRNAs are widely distributed within the body, with important biologic functions such as sponges for microRNAs, as RNA binding proteins, and as templates for regulation of transcription and protein translation. The abnormal expression of circRNAs in vivo is significantly associated with the development of urologic tumors. CircRNAs have now emerged as potential biomarkers for the diagnosis and prognosis of urologic tumors, as well as targets for the development of new therapies. Although we have gained a better understanding of circRNA, there are still many questions to be answered. In this review, we summarize the properties of circRNAs and detail their function, focusing on the effects of circRNA on proliferation, metastasis, apoptosis, metabolism, and drug resistance in kidney, bladder, and prostate cancers.

Crosstalk between circRNAs and the PI3K/AKT and/or MEK/ERK signaling pathways in digestive tract malignancy progression

Evidence indicates that circular RNAs (circRNAs) may play an important role in regulating gene expression by binding to miRNAs through miRNA response elements. circRNAs are formed by back-splicing and have a covalently closed structure. The biogenesis of circRNAs also appears to be regulated by certain cell-specific and/or gene-specific mechanisms, and thus some circRNAs are tissue specific and tumor-expression specific. Furthermore, the high stability and tissue specificity of circRNAs may be of value for early diagnosis, survival prediction and precision medicine. This review summarizes current knowledge regarding the classification and functions of circRNAs and the role of circRNAs in regulating the PI3K/AKT and/or MEK/ERK signaling pathways in digestive tract malignancy tumors.

CircRNA-104718 promotes glioma malignancy through regulation of miR-218-5p/HMGB1 signalling pathway

Increasing number of studies have proven that circular RNAs (circRNAs) play a major role in the biological processes of many different cancers, including glioma, especially as competitive molecular sponges of microRNAs (miRNAs). However, the clear molecular mechanism of the circRNA network in glioma is still not well understood. The expression level of circRNA-104718 and microRNA (miR)-218-5p in glioma tissues and cells were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The target protein's expression level was assessed by western blotting. Bioinformatics systems were used to predict the possible microRNAs and target genes of circRNA-104718, after which dual-luciferase reporter assays were used to confirm the predicted interactions. The proliferation, invasion, migration and apoptosis of glioma cells were detected by CCK, EdU, transwell, wound-healing and flow cytometry assays. CircRNA-104718 was upregulated in human glioma tissues, and a higher level of circRNA-104718 indicated poorer outcomes in glioma patients. In contrast, in glioma tissues, miR-218-5p was downregulated. Knockdown of circRNA-104718 suppressed migration and invasion while boosting the apoptosis rate of glioma cells. In addition, the upregulation of miR-218-5p in glioma cells caused the same suppression. Mechanistically, circRNA-104718 inhibited the protein expression level of high mobility group box-1 (HMGB1) by acting as a molecular sponge for miR-218-5p. CircRNA-104718 is a suppressive factor in glioma cells and might represent a new target for the treatment of glioma patients. CircRNA-104718 modulates glioma cell proliferation through the miR-218-5p/HMGB1 signalling axis. CircRNA-104718 provides a possible mechanism for understanding the pathogenesis of glioma.

The malignancy of chordomas is enhanced via a circTLK1/miR-16-5p/Smad3 positive feedback axis

CircRNAs play crucial roles in various malignancies via an increasing number of reported regulatory mechanisms, including the classic sponging mechanism between circRNAs and micro RNAs (miRNAs). We performed bioinformatic analyses and identified circTLK1 as a regulator of malignant chordoma progression. Moreover, we observed that circTLK1 showed high expression in chordoma cells and tissues, while circTLK1 interference suppressed chordoma cell proliferation and invasion. In addition, circTLK1 directly interacted with miR-16-5p, which has previously been shown to repress chordoma, and circTLK1 knockdown suppressed Smad3 expression. Chromatin immunoprecipitation sequencing further demonstrated that Smad3 acts as a positive regulator by interacting with TLK1, thereby mediating the circTLK1/miR-16-5p/Smad3 positive feedback axis. Taken together, our findings suggested that the disruption of the circTLK1/miR-16-5p/Smad3 positive feedback pathway, particularly via the Smad3 inhibitor SIS3, could be a promising therapeutic strategy.

circINSR Inhibits Adipogenic Differentiation of Adipose-Derived Stromal Vascular Fractions through the miR-152/MEOX2 Axis in Sheep

Adipose tissue plays a crucial role in energy metabolism. Several studies have shown that circular RNA (circRNA) is involved in the regulation of fat development and lipid metabolism. However, little is known about their involvement in the adipogenic differentiation of ovine stromal vascular fractions (SVFs). Here, based on previous sequencing data and bioinformatics analysis, a novel circINSR was identified in sheep, which acts as a sponge to promote miR-152 in inhibiting the adipogenic differentiation of ovine SVFs. The interactions between circINSR and miR-152 were examined using bioinformatics, luciferase assays, and RNA immunoprecipitation. Of note, we found that circINSR was involved in adipogenic differentiation via the miR-152/mesenchyme homeobox 2 (MEOX2) pathway. MEOX2 inhibited adipogenic differentiation of ovine SVFs and miR-152 inhibited the expression of MEOX2. In other words, circINSR directly isolates miR-152 in the cytoplasm and inhibits its ability to promote adipogenic differentiation of ovine SVFs. In summary, this study revealed the role of circINSR in the adipogenic differentiation of ovine SVFs and its regulatory mechanisms, providing a reference for further interpretation of the development of ovine fat and its regulatory mechanisms.

Identification of prognostic genes signature and construction of ceRNA network in pirarubicin treatment of triple-negative breast cancer

BACKGROUND

The altered long non-coding RNA (lncRNA), circular RNA (circRNA) and mRNA expression in triple-negative breast cancer (TNBC) after pirarubicin (THP) treatment can be a critical factor in the development of tumor. Here, we identify a set of lncRNA, circRNA, and mRNA that can reveal the molecular target and molecular mechanism of THP, and can be used to predict the prognostic characteristics of TNBC.

METHODS

Affymetrix GeneChip sequencing was performed to determine whether lncRNA, circRNA, and mRNA were changed in MDA-MB-231 cells after THP treatment, and qRT-PCR was used to verify the accuracy of GeneChip results. Bioinformatics methods were used to analyze the differentially expressed (DE) lncRNA, circRNA and mRNA, and the co-expression network and ceRNA network were constructed. The STRING database, Kaplan-meier Mapper database, GEPIA database, and Tumor Immunity Estimation Resource were used to screen hub genes with clinical value and important significance.

RESULTS

THP 5 μM could significantly inhibit proliferation, migration and invasion of MDA-MB-231 cells for 24 h. 1547 DE lncRNAs, 4992 DE circRNAs, and 5777 DE mRNAs were identified. The reliability of the GeneChip was verified by qRT-PCR. An mRNA-lncRNA/circRNA co-expression network was constructed based on the Pearson correlation coefficient. Finally, we established a new ceRNA network, including three circRNAs, five miRNAs, and three mRNAs. The mRNAs are associated with immune infiltration. The mRNAs and miRNAs are significantly associated with survival outcomes in TNBC.

CONCLUSION

The results reveal the molecular target and mechanism of THP treatment of TNBC. These ceRNA network can be used as molecular targets for the treatment of TNBC patients and as molecular biomarkers to predict patient prognosis.

CircSEC11A knockdown alleviates oxidative stress and apoptosis and promotes cell proliferation and angiogenesis by regulating miR-29a-3p/SEMA3A axis in OGD-induced human brain microvascular endothelial cells (HBMECs)

BACKGROUND

Circular RNA (circRNA) has been found to play an important role in the progression of many diseases, including ischemic stroke. However, the regulatory mechanism of circSEC11A in ischemic stroke progression need to further investigation.

METHODS

Human brain microvascular endothelial cells (HBMECs) were stimulated by oxygen glucose deprivation (OGD). CircSEC11A, SEC11A mRNA and miR (microRNA)-29a-3p were quantified by quantitative real-time PCR (qRT-PCR). SEMA3A, BAX and BCL2 protein level was quantified by western blot. Oxidative stress, cell proliferation, angiogenesis and apoptosis abilities were gauged by oxidative stress assay kit, 5-Ethynyl-2'-Deoxyuridine (EdU) staining, tube formation assay and flow cytometry assays, respectively. Direct relationship between miR-29a-3p and circSEC11A or SEMA3A was validated by dual-luciferase reporter assay, RIP assay and RNA pull-down assay.

RESULTS

CircSEC11A was upregulated in OGD-induced HBMECs. OGD promoted the oxidative stress and apoptosis and inhibited cell proliferation and angiogenesis, while circSEC11A knockdown relieved the effects. CircSEC11A functioned as the sponge for miR-29a-3p, and miR-29a-3p inhibitor reversed the effects of si-circSEC11A on OGD-induced HBMECs oxidative injuries. Moreover, SEMA3A served as the target gene of miR-29a-3p. MiR-29a-3p inhibition ameliorated OGD-induced HBMECs oxidative injuries, while SEMA3A overexpression rescued the impacts of miR-29a-3p mimic.

CONCLUSION

CircSEC11A promoted the malignant progression in OGD-induced HBMECs through the mediation of miR-29a-3p/SEMA3A axis. This study has provided the new insight into the underlying application of circSEC11A in cell model of ischemic stroke.

Epigenetic reprogramming in pancreatic premalignancy and clinical implications

Pancreatic cancer (PC) is the most lethal human cancer, with less than 10% 5-year survival. Pancreatic premalignancy is a genetic and epigenomic disease and is linked to PC initiation. Pancreatic premalignant lesions include pancreatic intraepithelial neoplasia (PanIN), intraductal papillary mucinous neoplasm (IPMN), and mucinous cystic neoplasm (MCN), with pancreatic acinar-to-ductal metaplasia (ADM) as the major source of pancreatic premalignant lesions. Emerging evidence reveals that an epigenetic dysregulation is an early event in pancreatic tumorigenesis. The molecular mechanisms of epigenetic inheritance include chromatin remodeling; modifications in histone, DNA, and RNA; non-coding RNA expression; and alternative splicing of RNA. Changes in those epigenetic modifications contribute to the most notable alterations in chromatin structure and promoter accessibility, thus leading to the silence of tumor suppressor genes and/or activation of oncogenes. The expression profiles of various epigenetic molecules provide a promising opportunity for biomarker development for early diagnosis of PC and novel targeted treatment strategies. However, how the alterations in epigenetic regulatory machinery regulate epigenetic reprogramming in pancreatic premalignant lesions and the different stages of their initiation needs further investigation. This review will summarize the current knowledge of epigenetic reprogramming in pancreatic premalignant initiation and progression, and its clinical applications as detection and diagnostic biomarkers and therapeutic targets in PC.

Novel hypoxia-induced HIF1α-circTDRD3-positive feedback loop promotes the growth and metastasis of colorectal cancer

Tumor hypoxia and circular RNAs (circRNAs) are considered to play key roles in tumor progression and malignancy, respectively. Nevertheless, the biological functions and underlying mechanisms of specific circRNAs exposed to hypoxic microenvironments in colorectal cancer (CRC) remain largely elusive. Herein, a novel circRNA, circTDRD3, which is upregulated under hypoxic conditions, was identified. The expression of circTDRD3 was highly expressed in CRC tissues and positively correlated with overall survival, tumor size, lymph node invasion and clinical stage. CircTDRD3 facilitated CRC cell proliferation, migration and metastasis in vitro and in vivo. Mechanistically, circTDRD3 promoted HIF1α expression by sponging miR-1231, which facilitated CRC progression. Meanwhile, HIF1α directly combined with TDRD3 promoter to increase the expression of TDRD3 pre-mRNA. Then HIF1a-induced PTBP1 accelerated the formation of circTDRD3. Our findings reveal that circTDRD3 facilitates the proliferation and metastasis of CRC through a positive feedback loop mediated by the HIF1α/PTBP1/circTDRD3/miR-1231/HIF1α axis. Therefore, circTDRD3 may serve as a prognostic biomarker and therapeutic target for patients with CRC.

Prognostic, Diagnostic, and Clinicopathological Significance of Circular RNAs in Pancreatic Cancer: A Systematic Review and Meta-Analysis

Pancreatic cancer (PC) is a highly aggressive malignant tumor with a high mortality rate. It is urgent to find optimal molecular targets for the early diagnosis and treatment of PC. Here, we aimed to systematically analyze the prognostic, diagnostic, and clinicopathological significance of circular RNAs (circRNAs) in PC. Relevant studies were screened through PubMed, Web of Science, and other databases. The prognostic value of PC-associated circRNAs was assessed using the composite hazard ratio (HR), the diagnostic performance was assessed using the area under the summary receiver operator characteristic (SROC) curve (AUC), and the correlation with clinicopathological characteristics using the composite odds ratio (OR) was explored. In our study, 48 studies were included: 34 for prognosis, 11 for diagnosis, and 30 for correlation with clinicopathological characteristics. For prognosis, upregulated circRNAs were associated with poorer overall survival (OS) (HR = 2.02) and disease-free survival/progression-free survival (HR = 1.84) while downregulated circRNAs were associated with longer OS (HR = 0.55). Notably, the combination of circRNAs, including hsa_circ_0064288, hsa_circ_0000234, hsa_circ_0004680, hsa_circ_0071036, hsa_circ_0000677, and hsa_circ_0001460, was associated with worse OS (HR = 2.35). For diagnosis, the AUC was 0.83, and the pooled sensitivity and specificity were 0.79 and 0.73, respectively. For clinicopathologic characteristics, upregulated circRNAs were associated with poorer tumor differentiation, more nerve and vascular invasion, higher T stage, lymphatic metastasis, distant metastasis, advanced TNM stage, and higher preoperative CA19-9 level. In contrast, downregulated circRNAs were negatively associated with PC differentiation and lymphatic metastasis. Overall, our results showed that circRNAs are closely related to the prognosis and clinicopathological characteristics of PC patients and could be utilized for early diagnosis; thus, they are promising biomarkers for clinical application in PC.

Roles of circular RNAs in the pathogenesis and treatment of pancreatic cancer

Circular RNAs are single-stranded RNAs with a covalently closed structure formed by the process of back-splicing. Aberrant expression of circular RNAs contributes to the pathogenesis of a wide range of cancers. Pancreatic cancer is one of the most lethal cancers due to diagnostic difficulties and limited therapeutic options. Circular RNAs are emerging as novel diagnostic biomarkers and therapeutic targets for pancreatic cancer. Moreover, recent advances in the therapeutic application of engineered circular RNAs have provided a promising approach to overcoming pancreatic cancer. This review discusses the roles of circular RNAs in the pathogenesis of pancreatic cancer and in potential treatment applications and their usefulness as diagnostic biomarkers.

CircDUSP22 Overexpression Restrains Pancreatic Cancer Development via Modulating miR-1178-3p and Downstream BNIP3

Aberrant expression of circular RNAs (circRNAs) is important in carcinogenesis, however, many differentially expressed circRNAs have not been functionally characterized. This study aimed to unveil the role of circRNA-dual specificity phosphatase 22 (circDUSP22) in pancreatic cancer (PaCa). Expression analyses of circDUSP22, miR-1178-3p and BCL2 interacting protein 3 (BNIP3) were carried out using quantitative real-time PCR (qRT-PCR) or western blotting. Cell growth was assessed by MTT, EdU and colony formation assays. Cell cycle distribution and cell apoptosis were investigated using flow cytometry assay. The assumed binding relationship between miR-1178-3p and circDUSP22 or BNIP3 was testified by dual-luciferase reporter and pull-down assays. The effect of circDUSP22 in vivo was identified by animal studies. The decreased expression of circDUSP22 was observed in PaCa samples and cells. CircDUSP22 ectopic expression in vitro blocked PaCa cell proliferation, arrested cell cycle and provoked cell apoptosis. CircDUSP22 targeted miR-1178-3p, whose expression was reinforced in PaCa. The inhibitory cell growth caused by circDUSP22 ectopic expression was reversed by miR-1178-3p enrichment. In addition, miR-1178-3p targeted BNIP3, whose expression was declined in PaCa. The inhibitory cell growth caused by circDUSP22 ectopic expression was reversed by BNIP3 knockdown. CircDUSP22 overexpression in vivo decelerated tumor growth. CircDUSP22 upregulation blocked PaCa development partly by targeting miR-1178-3p and increasing BNIP3, implying the potential implication of circDUSP22 in targeted therapy of PaCa.

Circular RNA hsa_circ_0007367 promotes the progression of pancreatic ductal adenocarcinoma by sponging miR-6820-3p and upregulating YAP1 expression

Circular RNAs (circRNAs) play critical regulatory roles in cancer biological processes. Nevertheless, the contributions and underlying mechanisms of circRNAs to pancreatic ductal adenocarcinoma (PDAC) remain largely unexplored. Dysregulated circRNAs between cancerous tissues and matched adjacent normal tissues were identified by circRNA microarray in PDAC. The biological effect of hsa_circ_007367 both in vitro and in vivo was demonstrated by gain- and loss-of-function experiments. Further, dual-luciferase reporter and RNA pull-down assays were performed to confirm the interaction among hsa_circ_007367, miR-6820-3p, and Yes-associated protein 1 (YAP1). The expression of hsa_circ_007367 and YAP1 were detected by in situ hybridization (ISH) and immunohistochemistry (IHC) using tissue microarray (TMA) in 128 PDAC samples. We first identified that a novel circRNA, hsa_circ_0007367, was markedly upregulated in PDAC tissues and cells. Functionally, in vivo and in vitro data indicated that hsa_circ_0007367 promotes the proliferation and metastasis of PDAC. Mechanistically, we confirmed that hsa_circ_0007367 could facilitate the expression of YAP1, a well-known oncogene, by sponging miR-6820-3p, which function as a tumor suppresser in PDAC cells. The results of ISH and IHC demonstrated that hsa_circ_0007367 and YAP1 were upregulated in PDAC tissues. Furthermore, clinical data showed that higher hsa_circ_0007367 expression was correlated with advanced histological grade and lymph node metastasis in PDAC patients. In conclusion, our findings reveal that hsa_circ_0007367 acts as an oncogene via modulating miR-6820-3p/YAP1 axis to promote the progression of PDAC, and suggest that hsa_circ_0007367 may serve as a potential therapeutic target for treatment of PDAC.

The integrative analysis of competitive endogenous RNA regulatory networks in osteoporosis

Osteoporosis (OP) is a common bone disease of old age resulting from the imbalance between bone resorption and bone formation. CircRNAs are a class of endogenous non-coding RNAs (ncRNAs) involved in gene regulation and may play important roles in the development of OP. Here, we aimed to discover the OP‑related circRNA-miRNA-mRNA (ceRNA) network and the potential mechanisms. Six microarray datasets were obtained from the GEO database and the OP‑related differentially expressed genes (DEGs), circRNAs (DECs), and miRNAs (DEMs) were screened out from these datasets. Then, combined with the prediction of the relationships between DEGs, DEMs, and DECs, a ceRNA network containing 7 target circRNAs, 5 target miRNAs, and 38 target genes was constructed. Then the RNA-seq verification by using total RNAs isolated from the femurs of normal and ovariectomized Wistar rats indicated that MFAP5, CAMK2A, and RGS4 in the ceRNA network were closely associated with osteoporosis. Function enrichment analysis indicated that the target circRNAs, miRNAs, and genes were involved in the process of MAPK cascade, hormone stimulus, cadherin binding, rRNA methyltransferase, PI3K-Akt signaling pathway, and Vitamin digestion and absorption, etc. Then a circRNA-miRNA-hub gene subnetwork was constructed and the qRT-PCR analysis of human bone tissues from the femoral head was used to confirm that the transcription of hsa_circR_0028877, hsa_circR_0082916, DIRAS2, CAMK2A, and MAPK4 showed a significant correlation with osteogenic genes. Besides, the two axes of hsa_circR_0028877/hsa-miR-1273f/CAMK2A and hsa_circR_0028877/hsa-miR-1273f/DIRAS2 conformed to be closely associated with OP. Additionally, by constructing a drug-target gene network, RKI-1447, FRAX486, Hyaluronic, and Fostamatinib were identified as therapeutic options for OP. Our study revealed the potential links between circRNAs, miRNAs, and mRNAs in OP, suggesting that the ceRNA mechanism might contribute to the occurrence of OP.

EIF4A3-regulated circ_0087429 can reverse EMT and inhibit the progression of cervical cancer via miR-5003-3p-dependent upregulation of OGN expression

BACKGROUND

Circular RNAs (circRNAs) are noncoding RNAs with stable structures with high expression and tissue-specific expression. Studies have shown that circRNA dysregulation is closely related to the progression of tumours. However, the function and regulatory mechanism of most circRNAs in cervical cancer are still unclear.   METHODS: CircRNAs related to cervical cancer were screened through the Gene Expression Omnibus (GEO) database. qRT-PCR was used to verify the expression of circ_0087429 in cervical cancer tissues and cells. Then, in vivo and in vitro experiments were conducted to evaluate the role of circ_0087429 in the progression of cervical cancer. The role of the circ_0087429/miR-5003-3p/osteoglycin (OGN) axis in the epithelial to mesenchymal transition (EMT) was confirmed by rescue experiments, fluorescence in situ hybridization, luciferase reporter assays, immunofluorescence staining and western blotting. The inhibitory effect of Eukaryotic initiation factor 4A-III (EIF4A3) on the biogenesis of circ_0087429 was verified by RNA immunoprecipitation (RIP) assays and qRT-PCR.

RESULTS

circ_0087429 is significantly downregulated in cervical cancer tissues and cells and negatively correlated with International Federation of Gynecology and Obstetrics (FIGO) staging and lymphatic metastasis in cervical cancer patients. circ_0087429 can significantly inhibit the proliferation, migration, invasion and angiogenesis of cervical cancer in vitro and tumour growth and metastasis in vivo. OGN is significantly downregulated in cervical cancer tissues and cells. circ_0087429 can upregulate the expression of OGN by competitively binding with miR-5003-3p, thereby reversing EMT and inhibiting the progression of cervical cancer. EIF4A3 can inhibit circ_0087429 expression by binding to its flanking regions.

CONCLUSIONS

As a tumour suppressor, circ_0087429 regulated by EIF4A3 can reverse EMT and inhibit the progression of cervical cancer through the miR-5003-3p/OGN axis. It is expected to become a potential target for the treatment of cervical cancer.

Silencing circOMA1 Inhibits Osteosarcoma Progression by Sponging miR-1294 to Regulate c-Myc Expression

Background

Several studies have reported that circRNAs have a crucial function in the tumorigenesis of various cancers. However, the expression and function of circOMA1 in osteosarcoma is unknown.

Methods

circOMA1 was identified through bioinformatics analysis. qRT-PCR was used to assess the expressions of circOMA1, miR-1294, and c-Myc in osteosarcoma tissues. Further, we performed functional experiments to explore the biological function of circOMA1 in osteosarcoma. Moreover, a luciferase reporter assay, RNA immunoprecipitation (RIP), and fluorescence in situ hybridisation (FISH) assay were performed to demonstrate the association between circOMA1 and miR-1294.

Results

circOMA1 exhibited considerable upregulation in osteosarcoma tissues compared with adjacent normal tissues. Silencing circOMA1 suppressed osteosarcoma progression in vitro and in vivo. Mechanically, circOMA1 functioned as a sponge of miR-1294 to upregulate c-Myc expression.

Conclusion

circOMA1 played the role of an oncogene in osteosarcoma and promoted osteosarcoma progression by mediating the miR-1294/c-Myc pathway, which might be a new target for treating osteosarcoma.

LncRNA MNX1-AS1: A novel oncogenic propellant in cancers

To date, recent studies have shown that long non-coding RNAs (lncRNAs) are key players in gene regulation processes involved in cancer pathogenesis. In general, Motor neuron and pancreas homeobox 1-antisense RNA1 (MNX1-AS1) is highly expressed in all cancers as reported so far and exerts oncogenic effects through different mechanisms. In this review, we comprehensively summarize the detailed mechanisms of potential functions of MNX1-AS1 in different cancer types as well as the latest knowledge highlighting the potential of MNX1-AS1 as a therapeutic target for cancer. Aberrant expression of MNX1-AS1 closely correlates with clinicopathological parameters. such as lymphatic metastasis, tumor size, tumor stage, OS and DFS. Thus, MNX1-AS1 can be used as a diagnostic and prognostic biomarker or even a therapeutic prognostic target. This article reviews its function, molecular mechanism and clinical prognosis in various malignancies.

HIF1α-SP1 interaction disrupts the circ-0001875/miR-31-5p/SP1 regulatory loop under a hypoxic microenvironment and promotes non-small cell lung cancer progression

BACKGROUND

Circular RNAs (circRNAs) play an important role in the progression of non-small cell lung cancer (NSCLC), especially under tumor hypoxia. However, the precise functions and underlying mechanisms of dysregulated circRNAs in NSCLC are largely unknown.

METHODS

High-throughput RNA sequencing was performed to identify significantly expressed circRNAs in NSCLC tissues. The functions of circ-0001875 in NSCLC cells were investigated in vitro and in vivo. The regulatory relationships of circ-0001875, miR-31-5p and SP1 were examined by dual luciferase reporter assays and rescue experiments. The signal pathway of epithelial-to-mesenchymal transition and the formation of filopodia were analyzed by western blot and immunofluorescence staining. The binding of SP1 to Alu elements was evaluated by RNA immunoprecipitation, and the HIF1α and SP1 interaction was detected by co-immunoprecipitation.

RESULTS

We identified the novel Has_circ_0001875 as a significantly upregulated circRNA in NSCLC tissues and cell lines. circ-0001875 promoted the proliferation and metastasis of NSCLC both in vitro and in vivo, and induced NSCLC cells to extend filopodia. Mechanistically, circ-0001875 sponged miR-31-5p to regulate SP1, influencing epithelial-to-mesenchymal transition via the TGFβ/Smad2 signal pathway. SP1 negatively regulated circ-0001875 formation through an AluSq-dependent feedback loop, which was disrupted by competitive binding of HIF1α to SP1 under hypoxia condition. The circ-0001875/miR-31-5p/SP1 axis was associated with the clinical features and prognosis of NSCLC patients.

CONCLUSIONS

Our results revealed that the circ-0001875/miR-31-5p/SP1 axis and the complex regulatory loops influence NSCLC progression. These findings provide new insights into the regulation of circRNA formation under tumor hypoxia.

Splicing factor derived circular RNA circCAMSAP1 accelerates nasopharyngeal carcinoma tumorigenesis via a SERPINH1/c-Myc positive feedback loop

Background

Circular RNAs play an important role in tumor genesis and progression, but they have not been sufficiently studied in patients with nasopharyngeal carcinoma (NPC).

Methods

The circular RNA, circCAMSAP1, was screened in NPC cells by RNA sequencing analysis. The expression of circCAMSAP1 in NPC tissues was examined by real-time quantitative polymerase chain reaction (RT-qPCR) and in situ hybridization. Wound-healing, transwell, MTT and flow cytometry assays, and nude mouse tumor models were used to explore the effect of circCAMSAP1 on proliferation and metastasis of NPC in vitro or in vivo. The downstream proteins regulated by circCAMSAP1 were screened using mass spectrometry. The interaction between circCAMSAP1 and the SERPINH1 mRNA was identified using the circular RNA immunoprecipitation method and the luciferase reporter assay. The interaction between SERPINH1 and transcription factor c-Myc was verified through Co-immunoprecipitation (Co-IP) and immunofluorescence. The effect of c-Myc on the generation of circCAMSAP1 was examined through RT-qPCR and chromatin immunoprecipitation. Finally, the splicing factors that promote the production of circCAMSAP1 were explored by RT-qPCR and RNA immunoprecipitation (RIP).

Results

We found that circCAMSAP1 was highly expressed in NPC tissues and promoted NPC proliferation and metastasis. Additionally, circCAMSAP1 promoted SERPINH1 expression through improved SERPINH1 mRNA stability by binding to the 3′-untranslated region (3’UTR) of SERPINH1. Highly expressed SERPINH1 reduced the ubiquitination-degradation rate of c-Myc, causing increased tumorigenesis. Meanwhile, c-Myc, cooperating with splicing factor 10 (SRSF10), could also promote CAMSAP1 pre-mRNA transcription and back-splicing, forming a positive feedback of circCAMSAP1 production, resulting in the proliferation and metastasis of NPC.

Conclusions

Our findings revealed that circCAMSAP1 promotes NPC proliferation and metastasis by binding to the 3’UTR of SERPINH1, suggesting that the positive feedback of circCAMSAP1-SERPINH1-c-Myc may serve as a prognostic biomarker or therapeutic target in patients with NPC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01502-2.

Research Progress of circRNAs in Glioblastoma

Circular RNAs (circRNAs) are a class of single-stranded covalently closed non-coding RNAs without a 5' cap structure or 3' terminal poly (A) tail, which are expressed in a variety of tissues and cells with conserved, stable and specific characteristics. Glioblastoma (GBM) is the most aggressive and lethal tumor in the central nervous system, characterized by high recurrence and mortality rates. The specific expression of circRNAs in GBM has demonstrated their potential to become new biomarkers for the development of GBM. The specific expression of circRNAs in GBM has shown their potential as new biomarkers for GBM cell proliferation, apoptosis, migration and invasion, which provides new ideas for GBM treatment. In this paper, we will review the biological properties and functions of circRNAs and their biological roles and clinical applications in GBM.

Long Non-Coding RNAs in Epithelial-Mesenchymal Transition of Pancreatic Cancer

Non-coding RNAs (ncRNAs), or RNA molecules that do not code for proteins, are generally categorized as either small or long ncRNA (lncRNA) and are involved in the pathogenesis of several diseases including many cancers. Identification of a large number of ncRNAs could help to elucidate previously unknown mechanisms in phenotype regulation. Some ncRNAs are encapsulated by extracellular vesicles (EVs) and transferred to recipient cells to regulate cellular processes, including epigenetic and post-transcriptional regulations. Recent studies have uncovered novel molecular mechanisms and functions of lncRNAs in pancreatic ductal adenocarcinoma (PDAC), one of the most intractable cancers that is highly invasive and metastatic. As the epithelial-mesenchymal transition (EMT) triggers tumor cell invasion and migration, clarification of the roles of lncRNA in EMT and tumor cell stemness would be critical for improving diagnostic and therapeutic approaches in metastatic cancers. This review provides an overview of relevant studies on lncRNA and its involvement with EMT in PDAC. Emerging knowledge offers evidence for the dysregulated expression of lncRNAs and essential insights into the potential contribution of both lncRNAs and EVs in the pathogenesis of PDAC. Future directions and new clinical applications for PDAC are also discussed.

Demethyltransferase FTO alpha-ketoglutarate dependent dioxygenase (FTO) regulates the proliferation, migration, invasion and tumor growth of prostate cancer by modulating the expression of melanocortin 4 receptor (MC4R)

N6-Methyladenosine (m6A) is the most abundant modifications in human messenger RNAs (mRNAs). This study aimed at investigating the function and mechanism of demethyltransferase fat mass and obesity-associated protein (FTO) in prostate cancer(PCa). The expression level of FTO in PCa was detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot. Besides, the impacts of FTO on the proliferation, migration and invasion of PCa cells were also detected by cell counting kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU) and transwell assays. Furthermore, we also explored the potential mechanism of FTO in PCa. The results showed that FTO expression was decreased in PCa, and the low expression of FTO showed an obvious relevance to the clinical characteristics. Downregulation of FTO facilitated the proliferation, migration, invasion and tumor growth of PCa cells. Besides, MC4R displayed a remarkably high expression in PCa tissues, whose expression and m6A level were regulated by FTO. Meanwhile, the in vitro experiments revealed that highly expressed FTO partially reversed the facilitating effect of highly expressed MC4R on the malignant phenotype of PCa cells. Overall, FTO was downregulated in PCa and its expression level showed a relevance to the prognosis of PCa patients. Additionally, FTO could regulate the proliferation, migration and invasion of PCa via regulating the expression level of MC4R.