Circ_SMAD4 promotes gastric carcinogenesis by activating wnt/β-catenin pathway

Resveratrol Inhibits circ_0074371-related Pathway to Alleviate Sepsis-induced Acute Kidney Injury

Resveratrol has a protective effect on sepsis-induced acute kidney injury (AKI). Circ_0074371 has been confirmed to inhibit sepsis-induced AKI process, but whether resveratrol inhibits sepsis-induced AKI by regulating circ_0074371-related pathway remains unclear. In this study, lipopolysaccharide (LPS)-induced renal tubular epithelial cells (HK2) were used to mimic AKI cell models. Quantitative real-time PCR was used to detect relative expression of circ_0074371, microRNA (miR)-145-5p and inositol polyphosphate multikinase (IPMK). Cell proliferation and apoptosis were detected by cell counting kit 8 assay, EdU assay and flow cytometry. The levels of inflammation factors were measured by ELISA assay, and MDA level and SOD activity were examined to assess oxidative stress. Protein expression of IPMK was evaluated by western bolt analysis. The relationship between miR-145-5p and circ_0074371 or IPMK was confirmed by dual-luciferase reporter assay. It was showed that circ_0074371 was upregulated in AKI patients and LPS-induced HK2 cells, and silencing of circ_0074371 promoted proliferation and inhibited apoptosis, inflammation and oxidative stress in LPS-induced HK2 cells. In terms of mechanism, circ_0074371 sponged miR-145-5p to positively regulate IPMK. IPMK overexpression could reverse the relieving effect of circ_0074371 knockdown on LPS-induced HK2 cell injury. Moreover, resveratrol suppressed LPS-induced apoptosis, inflammation and oxidative stress in HK2 cells, and circ_0074371 overexpression also reversed the protective effect of resveratrol against LPS-induced cell injury. Our data suggested that resveratrol alleviated LPS-induced HK2 cell injury by inactivating the circ_0074371/miR-145-5p/IPMK axis.

The dual roles of circRNAs in Wnt/β-Catenin signaling and cancer progression

Cancer, a complex pathophysiological condition, arises from the abnormal proliferation and survival of cells due to genetic mutations. Dysregulation of cell cycle control, apoptosis, and genomic stability contribute to uncontrolled growth and metastasis. Tumor heterogeneity, microenvironmental influences, and immune evasion further complicate cancer dynamics. The intricate interplay between circular RNAs (circRNAs) and the Wnt/β-Catenin signalling pathway has emerged as a pivotal axis in the landscape of cancer biology. The Wnt/β-Catenin pathway, a critical regulator of cell fate and proliferation, is frequently dysregulated in various cancers. CircRNAs, a class of non-coding RNAs with closed-loop structures, have garnered increasing attention for their diverse regulatory functions. This review systematically explores the intricate crosstalk between circRNAs and the Wnt/β-Catenin pathway, shedding light on their collective impact on cancer initiation and progression. The review explores the diverse mechanisms through which circRNAs modulate the Wnt/β-Catenin pathway, including sponging microRNAs, interacting with RNA-binding proteins, and influencing the expression of key components in the pathway. Furthermore, the review highlights specific circRNAs implicated in various cancer types, elucidating their roles as either oncogenic or tumour-suppressive players in the context of Wnt/β-Catenin signaling. The intricate regulatory networks formed by circRNAs in conjunction with the Wnt/β-Catenin pathway are discussed, providing insights into potential therapeutic targets and diagnostic biomarkers. This comprehensive review delves into the multifaceted roles of circRNAs in orchestrating tumorigenesis through their regulatory influence on the Wnt/β-Catenin pathway.

Mechanisms of immune checkpoint inhibitors: insights into the regulation of circular RNAS involved in cancer hallmarks

Current treatment strategies for cancer, especially advanced cancer, are limited and unsatisfactory. One of the most substantial advances in cancer therapy, in the last decades, was the discovery of a new layer of immunotherapy approach, immune checkpoint inhibitors (ICIs), which can specifically activate immune cells by targeting immune checkpoints. Immune checkpoints are a type of immunosuppressive molecules expressed on immune cells, which can regulate the degree of immune activation and avoid autoimmune responses. ICIs, such as anti-PD-1/PD-L1 drugs, has shown inspiring efficacy and broad applicability across various cancers. Unfortunately, not all cancer patients benefit remarkably from ICIs, and the overall response rates to ICIs remain relatively low for most cancer types. Moreover, the primary and acquired resistance to ICIs pose serious challenges to the clinical application of cancer immunotherapy. Thus, a deeper understanding of the molecular biological properties and regulatory mechanisms of immune checkpoints is urgently needed to improve clinical options for current therapies. Recently, circular RNAs (circRNAs) have attracted increasing attention, not only due to their involvement in various aspects of cancer hallmarks, but also for their impact on immune checkpoints in shaping the tumor immune microenvironment. In this review, we systematically summarize the current status of immune checkpoints in cancer and the existing regulatory roles of circRNAs on immune checkpoints. Meanwhile, we also aim to settle the issue in an evidence-oriented manner that circRNAs involved in cancer hallmarks regulate the effects and resistance of ICIs by targeting immune checkpoints.

CircTMEM87A promotes the tumorigenesis of gastric cancer by regulating the miR-1276/SLC7A11 axis

BACKGROUND

Gastric cancer (GC) is a common malignancy with high incidence and mortality, and its pathogenesis involves the regulation of circular RNAs (circRNAs). However, the molecular mechanism of circTMEM87A in GC malignant progression is uncertain.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the expressions of circTMEM87A, miR-1276, and solute carrier family 7 membrane 11 (SLC7A11). Western blot was applied to detect protein expression levels of EMT-related proteins (vimentin and E-cadherin) and SLC7A11. Cell counting kit-8 assay (CCK8) and thymidine analog 5-ethynyl-2'-deoxyuridine (EdU) were performed to assess cell proliferation. Apoptosis was investigated using flow cytometry. Transwell assay and wound healing assay were carried out to examine the migration of MKN-7 and AGS cells. The Cellular ROS Assay Kit, Iron Assay Kit, and GSH/GSSG Ratio Detection Assay Kit were utilized to monitor lipid ROS level, iron level, and GSH/GSSG ratio, respectively. The interaction between miR-1276 and circTMEM87A or SLC7A11 was investigated using dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. A xenograft mouse model was constructed to explore the function of circTMEM87A in tumor formation in vivo.

RESULTS

CircTMEM87A and SLC7A11 were upregulated, while miR-1276 was downregulated in GC tissues and cells. Knockdown of circTMEM87A suppressed the proliferation and migration and promoted apoptosis and ferroptosis of GC cells. CircTMEM87A served as a sponge for miR-1276, and miR-1276 inhibitor relieved the circTMEM87A knockdown-induced effects on GC cell phenotypes. Similarly, SLC7A11, a downstream gene of miR-1276, rescued miR-1276 overexpression-induced effects on GC cell function. Furthermore, circTMEM87A knockdown inhibited GC cell tumor phenotypes in vivo.

CONCLUSION

CircTMEM87A promoted the proliferation and migration and inhibited apoptosis and ferroptosis of GC cells by increasing SLC7A11 expression through binding to miR-1276.

METTL3-mediated m6A modification of circRNF220 modulates miR-330-5p/survivin axis to promote osteosarcoma progression

BACKGROUND

Circular RNAs (circRNAs) play a crucial role in regulating various physiological processes. However, the precise regulatory mechanisms of circRNF220s in osteosarcoma (OS) are not well understood.

METHODS

The abundances of circRNF220, miR-330-5p, and survivin were determined using qRT-PCR. To assess the m6A accumulation in circRNF220, a methylated RNA immunoprecipitation (Me-RIP) assay was conducted. Cellular multiplication, motility, and invasion were examined using the cell Counting Kit-8 (CCK-8), EdU, colony formation, Transwell, and wound-healing assays. The binding relationships were measured through RNA immunoprecipitation (RIP) and luciferase reporter assays. In vivo functionality was assessed using xenograft models.

RESULTS

CircRNF220 was identified as being overexpressed in both OS cells and tissues. In vitro experiments demonstrated that silencing circRNF220 impeded the proliferation, invasion, and motility of OS cells. Similarly, in vivo studies confirmed that downregulating circRNF220 inhibited the growth of OS. Further mechanistic investigations unveiled that METTL3-modulated circRNF220 regulated the progression of OS by upregulating survivin expression through acting as a sponge for miR-330-5p.

CONCLUSION

The modulation of METTL3-regulated circRNF220 has been found to promote the progression of OS by modulating the miR-330-5p/survivin axis. This novel finding suggests a potentially unique approach to managing OS.

Circ-SUZ12 Protects Cardiomyocytes from Hypoxia-Induced Dysfunction Through Upregulating SUZ12 Expression to Activate Wnt/β-catenin Signaling Pathway

Acute myocardial infarction (AMI) is a common coronary artery disease. This study attempted to reveal the impact of circ-SUZ12 (hsa_circ_0042961) on cardiomyocyte injury after exposure to hypoxia.Circ-SUZ12 was screened out from the GEO dataset GSE169594. RNA expression and protein level were detected by quantitative real-time PCR (qRT-PCR) and Western blot, respectively. The characteristics of circ-SUZ12 were identified by measuring its resistance to Rnase R or actinomycin D (Act D) treatment. CCK-8 and EdU assays were performed to explore the viability of AC16 cells. Cell apoptosis was assessed through TUNEL assay and flow cytometry analysis. Mechanism experiments were performed to investigate the downstream molecular mechanism of circ-SUZ12.Circ-SUZ12 was highly expressed in blood samples of AMI patients in the GEO dataset and lowly expressed in hypoxia-treated cardiomyocytes. Overexpression of circ-SUZ12 reversed hypoxia-induced cardiomyocyte injury. Circ-SUZ12 regulated SUZ12 polycomb repressive complex 2 subunit (SUZ12) expression by recruiting FUS protein. SUZ12 activated the Wnt/β-catenin signaling pathway by increasing the H3K27me3 level in microRNA (miR)-526b-5p promoter to release catenin beta 1 (CTNNB1). CTNNB1 depletion reversed the effect of circ-SUZ12 on the viability and apoptosis of hypoxia-induced cardiomyocytes.Circ-SUZ12 protects cardiomyocytes from hypoxia-induced dysfunction through upregulating SUZ12 expression to activate the Wnt/β-catenin signaling pathway.

Deciphering the Enigmatic Influence: Non-Coding RNAs Orchestrating Wnt/β-Catenin Signaling Pathway in Tumor Progression

Dysregulated expression of specific non-coding RNAs (ncRNAs) has been strongly linked to tumorigenesis, cancer progression, and therapeutic resistance. These ncRNAs can act as either oncogenes or tumor suppressors, thereby serving as valuable diagnostic and prognostic markers. Numerous studies have implicated the participation of ncRNAs in the regulation of diverse signaling pathways, including the pivotal Wnt/β-catenin signaling pathway that is widely acknowledged for its pivotal role in embryogenesis, cellular proliferation, and tumor biology control. Recent emerging evidence has shed light on the capacity of ncRNAs to interact with key components of the Wnt/β-catenin signaling pathway, thereby modulating the expression of Wnt target genes in cancer cells. Notably, the activity of this pathway can reciprocally influence the expression levels of ncRNAs. However, comprehensive analysis investigating the specific ncRNAs associated with the Wnt/β-catenin signaling pathway and their intricate interactions in cancer remains elusive. Based on these noteworthy findings, this review aims to unravel the intricate associations between ncRNAs and the Wnt/β-catenin signaling pathway during cancer initiation, progression, and their potential implications for therapeutic interventions. Additionally, we provide a comprehensive overview of the characteristics of ncRNAs and the Wnt/β-catenin signaling pathway, accompanied by a thorough discussion of their functional roles in tumor biology. Targeting ncRNAs and molecules associated with the Wnt/β-catenin signaling pathway may emerge as a promising and effective therapeutic strategy in future cancer treatments.

CircUSP48 promotes malignant behavior by regulating CYR61 via miR-365 in osteosarcoma

Even though circular RNAs (circRNAs), a class of non-coding endogenous RNA, play a crucial role in the progression of osteosarcoma (OS), the specific function of hsa_circ_0000028 (circUSP48) remains unclear. This study aims to elucidate the mechanism by which circUSP48 regulates OS. We employed qRT-PCR and western blot techniques to quantify circDOCK1, miR-186, and DNMT3A levels. Cell proliferation was assessed using the cell counting kit-8 (CCK-8), 5-Ethynyl-20-deoxyuridine (EdU) assay, and colony formation assay. Cell migration and invasion were evaluated through Transwell and cell scratch assays. Furthermore, we performed dual-luciferase reporter, RIP, and RNA pull-down assays to investigate the association between circUSP48, miR-365, and CYR61. In addition, an in vivo xenograft model was utilized to assess the functional role of circUSP48. High levels of circUSP48 and CYR61 were observed in OS tissues and cells, while miR-365 levels were low. Knockdown of circUSP48 suppressed the multiplication, motility, and invasion of OS cells, thereby reducing carcinoma growth. Moreover, inhibition of miR-365 reversed the OS cell-suppressive effect caused by circUSP48 knockdown through direct interaction with circUSP48. Additionally, circUSP48 upregulated the expression of CYR61 by sponging miR-365. The findings suggest that circUSP48 promotes malignant behavior in OS by regulating the expression of CYR61 through miR-365, making it a potential therapeutic target for OS.

A spotlight on the interplay between Wnt/β-catenin signaling and circular RNAs in hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is one of the deadliest cancers due to multifocal development and distant metastasis resulting from late diagnosis. Consequently, new approaches to HCC diagnosis and treatment are required to reduce mortality rates. A large body of evidence suggests that non-coding RNAs (ncRNAs) are important in cancer initiation and progression. Cancer cells release many of these ncRNAs into the blood or urine, enabling their use as a diagnostic tool. Circular RNAs (CircRNAs) are as a members of the ncRNAs that regulate cancer cell expansion, migration, metastasis, and chemoresistance through different mechanisms such as the Wnt/β-catenin Signaling pathway. The Wnt/β-catenin pathway plays prominent roles in several biological processes including organogenesis, stem cell regeneration, and cell survival. Aberrant signaling of both pathways mentioned above could affect the progression and metastasis of many cancers, including HCC. Based on several studies investigated in the current review, circRNAs have an effect on HCC formation and progression by sponging miRNAs and RNA-binding proteins (RBPs) and regulating the Wnt/β-catenin signaling pathway. Therefore, circRNAs/miRNAs or RBPs/Wnt/β-catenin signaling pathway could be considered promising prognostic and therapeutic targets in HCC.

Non-coding RNA-based therapeutics in cancer therapy: An emphasis on Wnt/β-catenin control

Non-coding RNA transcripts are RNA molecules that have mainly regulatory functions and they do not encode proteins. microRNAs (miRNAs), lncRNAs and circRNAs are major types of this family and these epigenetic factors participate in disease pathogenesis, especially cancer that their abnormal expression may lead to cancer progression. miRNAs and lncRNAs possess a linear structure, whereas circRNAs possess ring structures and high stability. Wnt/β-catenin is an important factor in cancer with oncogenic function and it can increase growth, invasion and therapy resistance in tumors. Wnt upregulation occurs upon transfer of β-catenin to nucleus. Interaction of ncRNAs with Wnt/β-catenin signaling can determine tumorigenesis. Wnt upregulation is observed in cancers and miRNAs are able to bind to 3'-UTR of Wnt to reduce its level. LncRNAs can directly/indirectly regulate Wnt and in indirect manner, lncRNAs sponge miRNAs. CircRNAs are new emerging regulators of Wnt and by its stimulation, they increase tumor progression. CircRNA/miRNA axis can affect Wnt and carcinogenesis. Overall, interaction of ncRNAs with Wnt can determine proliferation rate, migration ability and therapy response of cancers. Furthermore, ncRNA/Wnt/β-catenin axis can be utilized as biomarker in cancer and for prognostic applications in patients.

Human umbilical cord mesenchymal stem cells conditioned medium exerts anti-tumor effects on KGN cells in a cell density-dependent manner through activation of the Hippo pathway

BACKGROUND

The conditioned medium from human umbilical cord mesenchymal stem cells (UCMSCs-CM) provides a new cell-free therapy for tumors due to its unique secretome. However, there are many contradictory reports about the effect of UCMSCs-CM on tumor cells. The loss of contact inhibition is a common characteristic of tumor cells. A relationship between the effect of UCMSCs-CM on tumor cells and contact inhibition in tumor cells is rarely concerned. Whether the effect of UCMSCs-CM on tumor cells is affected by cell density? Here, we explored the effect of UCMSCs-CM on granulosa tumor cell line (KGN) cells at low or high density.

METHODS

Growth curve and CCK8 assay were used to assess cell proliferation and viability. Scratch wound and matrigel invasion assay were implicated to detect cell motility of KGN cells. UCMSCs-CM effects on cell cycle, apoptosis and pathway-related proteins were investigated by flow cytometry, TUNEL assay, western blot and immunofluorescence analysis respectively.

RESULTS

In growth curve analysis, before KGN cells proliferated into confluence, UCMSCs-CM had no effect on cell proliferation. However, once the cells proliferate to contact each other, UCMSCs-CM significantly inhibited proliferation. Meanwhile, when KGN cells were implanted at high density, UCMSCs-CM could induce cell cycle arrest at G1 phase, inhibit cell migration, invasion and promote apoptosis. While it had no similar effect on KGN cells implanted at low density. In mechanism, the UCMSCs-CM treatment activated the Hippo pathway when KGN cells were implanted at high density. Consistently, the MST1/2 inhibitor, XMU-MP-1, inhibited the activation of the Hippo pathway induced by UCMSCs-CM treatment and accordingly declined the anti-tumor effect of UCMSCs-CM on KGN cells.

CONCLUSIONS

The effect of UCMSCs-CM on tumor cells is affected by cell density. UCMSCs-CM exerted anti-tumor effect on KGN cells by activating Hippo pathway to restore contact inhibition. Our results suggest that UCMSCs-CM is a promising therapeutic candidate for GCT treatment.

Role of circRNAs in gastric cancer

Circular RNAs (circRNAs) are a large class of non-coding RNAs with single-strand covalently closed loops, formed by reverse splicing, which widely exist in many cell lines and diverse species. Some circRNAs have highly evolutionarily conserved sequences, or tissue-specific or cell-specific expression patterns, and many circRNAs are extremely stable. In the past decades, accumulating evidence has indicated that circRNAs participate in the mechanisms associated with the development of many kinds of tumors, exert important biological functions by acting as microRNA or protein ‘sponges’, transcriptional regulatory factors, and protein translation templates, and play key roles in the occurrence and development of gastric cancer. This review comprehensively summarizes the biogenesis, characteristics, and biological functions of circRNAs, and the molecular mechanisms underlying the role of circRNAs in the carcinogenesis and progression of gastric cancer.

Silencing circUSP48 suppresses osteosarcoma progression by regulating the miR-335/ smad nuclear interacting protein 1 pathway

BACKGROUND

Circular RNAs (circRNAs) can have a critical function in the multi-processes of osteosarcoma (OS). Nevertheless, whether circUSP48 is involved in OS progression remains unclear.

METHODS

In the current work, the expression of circUSP48, miR-335 and SNIP1 in OS cell lines and tissues were evaluated using qRT-PCR. Then, Sanger sequencing, RNase R treatment and FISH assay were performed for circUSP48 validation. Furthermore, the function and potential mechanisms of circUSP48 in OS were investigated by performing loss-of-function experiments.

RESULTS

Silencing circUSP48 could suppress proliferation, invasion as well as migration of OS cells in vitro, also inhibiting the growth of tumor in vivo. Importantly, circUSP48 promoted OS malignancy by sponging miR-335 to upregulate SNIP1.

CONCLUSION

Overall, these findings suggested that circUSP48 acted as an oncogene in OS, which might become a new target for OS therapy.

circBGN accelerates gastric cancer cell proliferation and invasion via activating IL6/STAT3 signaling pathway

Circular RNAs participate in the pathogenesis of various tumors, including gastric cancer (GC). In this study, we investigated the role of circBGN in regulating proliferation and invasion of GC cells and elucidated the mechanism. The expression of circBGN was assessed by quantitative reverse-transcription PCR and in situ hybridization. In addition, loss- and gain-of-function investigations in vitro and in vivo were performed to determine the biological functions of circBGN. Luciferase reporter assays and rescue experiments were applied to investigate the interaction between circBGN and miR-149-5p as well as the relationship between miR-149-5p and IL6. Our results showed that circBGN expression was significantly elevated in GC tissues and cells. Knockdown of circBGN dramatically suppressed GC cell proliferation and invasion in vitro. Xenograft experiments revealed that knockdown of circBGN delayed tumor growth in vivo. Furthermore, circBGN can directly bind to miR-149-5p, thereby preventing miR-149-5p from binding to its target mRNA [IL6 mRNA], thus activating IL6/STAT3 signaling pathway. Rescue assays indicated that circBGN regulates GC cell proliferation and invasion by upregulating miR-149-5p/IL6 axis output. Taken together, our investigation indicates that circBGN supports GC progression by activating IL6/STAT3 signaling pathway, thus pointing to a new possible therapeutic target in GC.

Circular RNAs as diagnostic biomarkers for gastric cancer: A comprehensive update from emerging functions to clinical significances

The incidence and mortality of gastric cancer ranks as a fouth leading cause of cancer death worldwide, especially in East Asia. Due to the lack of specific early-stage symptoms, the majority of patients in most developing nations are diagnosed at an advanced stage. Therefore, it is urgent to find more sensitive and reliable biomarkers for gastric cancer screening and diagnosis. Circular RNAs (circRNAs), a novel type of RNAs with covalently closed loops, are becoming a latest hot spot in the field of. In recent years, a great deal of research has demonstrated that abnormal expression of circRNAs was associated with the development of gastric cancer, and suggested that circRNA might serve as a potential biomarker for gastric cancer diagnosis. In this review, we summarize the structural characteristics, formation mechanism and biological function of circRNAs, and elucidate research progress and existing problems in early screening of gastric cancer.

Circ_0006404 enhances hepatocellular carcinoma progression by regulating miR-624

Growing studies have demonstrated that circRNAs (circular RNAs) act potential roles in tumor metastasis and progression. However, the expression and function of circ_0006404 in hepatocellular carcinoma (HCC) remain to be investigated. The expression of circ_0006404 and miR-624 was detected by qRT-PCR. CCK-8 assay, flow cytometry, and wound healing were performed to determine cell proliferation, cycle, and migration. The target of circ_0006404 was studied by bioinformatics and luciferase activity analysis. Our data indicated that circ_0006404 was overexpressed in HCC specimens and cells and ectopic expression of circ_0006404 increased HCC cell growth, cycle, and migration. Moreover, we showed that miR-624 was downregulated in HCC specimens and cells and miR-624 expression was negatively correlated with circ_0006404 expression in HCC specimens. Circ_0006404 sponged miR-624 in HCC cell, and the overexpression of circ_0006404 suppressed miR-624 expression in HCC cell. Furthermore, circ_0006404 induced HCC cell growth, cycle, and migration via regulating miR-624. These results elucidated that circ_0006404 facilitated HCC progression and might act as one new biomarker for this carcinoma.

The functional roles of the circRNA/Wnt axis in cancer

CircRNAs, covalently closed noncoding RNAs, are widely expressed in a wide range of species ranging from viruses to plants to mammals. CircRNAs were enriched in the Wnt pathway. Aberrant Wnt pathway activation is involved in the development of various types of cancers. Accumulating evidence indicates that the circRNA/Wnt axis modulates the expression of cancer-associated genes and then regulates cancer progression. Wnt pathway-related circRNA expression is obviously associated with many clinical characteristics. CircRNAs could regulate cell biological functions by interacting with the Wnt pathway. Moreover, Wnt pathway-related circRNAs are promising potential biomarkers for cancer diagnosis, prognosis evaluation, and treatment. In our review, we summarized the recent research progress on the role and clinical application of Wnt pathway-related circRNAs in tumorigenesis and progression.

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.

Hsa_circ_0134111 promotes intervertebral disc degeneration via sponging miR-578

Intervertebral disc degeneration (IDD) is a chronic degenerative and age-dependent process characterized by aberrant apoptosis, proliferation, synthesis, and catabolism of the extracellular matrix of the nucleus pulposus (NP) cells. Recently, studies showed that circular RNAs play important roles in the development of many diseases. However, the role of circRNAs in IDD development remains unknown. We showed that circ_0134111 level was overexpressed in IDD tissue samples as compar-ed to control tissues. The upregulation of circ_0134111 was more drastic in the moderate and severe IDD cases than in those with mild IDD. In addition, we showed that interleukin-1β and tumor necrosis factor-α exposure significantly enhanced circ_0134111 expression in NP cells. Furthermore, ectopic expression of circ_0134111 induced proliferation, pro-inflammatory cytokine secretion, and ECM degradation in the NP cells. We also showed that circ_0134111 directly interacted with microRNA (miR)-578 in NP cells where elevated expression of circ_0134111 enhanced the ADAMTS-5 and MMP-9 expression. Moreover, miR-578 expression was significantly decreased in IDD patients and the miR-578 expression was negatively correlated with circ_0134111 expression in the IDD samples. Interleukin-1β and tumor necrosis factor-α exposure significantly decreased miR-578 levels in NP cells, in which ectopic miR-578 expression inhibited cell growth, pro-inflammatory cytokine expression, and ECM degradation. Finally, we showed that circ_0134111 overexpression induced the IDD-related phenotypic changes through inhibiting miR-578. These data suggested that circ_0134111 could promote the progression of IDD through enhancing aberrant NP cell growth, inflammation, and ECM degradation partly via regulating miR-578.

Emerging Roles of Circular RNAs in Vascular Smooth Muscle Cell Dysfunction

Atherosclerosis is the major pathophysiological basis of cerebrovascular and cardiovascular diseases. Vascular smooth muscle cells (VSMCs) constitute the main structure of vasculature and play important roles in maintaining vascular tone and blood pressure. Many biological processes and cellular signaling events involved in atherosclerogenesis have been shown to converge on deregulating VSMC functions. However, the molecular mechanisms underlying dysfunctional VSMC in atherosclerosis are still poorly defined. Recent evidence revealed that circular RNAs (circRNAs) are closely related to diseases such as degenerative diseases, tumor, congenital diseases, endocrine diseases and cardiovascular diseases. Several studies demonstrated that circRNAs (e.g., circACTA2, Circ-SATB2, circDiaph3, circ_0020397, circTET3, circCCDC66) played critical roles in the regulation of VSMC proliferation, migration, invasion, and contractile-to-synthetic phenotype transformation by sponging microRNAs (e.g., miR-548f-5p, miR-939, miR-148a-5p, miR-138, miR-351-5p, miR-342-3p). This review describes recent progress in the profiling of circRNAs by transcriptome analysis in VSMCs and their molecular functions in regulating VSMC proliferation and migration.

Gastric cancer: An epigenetic view

Gastric cancer (GC) poses a serious threat worldwide with unfavorable prognosis mainly due to late diagnosis and limited therapies. Therefore, precise molecular classification and search for potential targets are required for diagnosis and treatment, as GC is complicated and heterogeneous in nature. Accumulating evidence indicates that epigenetics plays a vital role in gastric carcinogenesis and progression, including histone modifications, DNA methylation and non-coding RNAs. Epigenetic biomarkers and drugs are currently under intensive evaluations to ensure efficient clinical utility in GC. In this review, key epigenetic alterations and related functions and mechanisms are summarized in GC. We focus on integration of existing epigenetic findings in GC for the bench-to-bedside translation of some pivotal epigenetic alterations into clinical practice and also describe the vacant field waiting for investigation.

CircRNAs in gastric cancer: current research and potential clinical implications

Gastric cancer (GC) has a dismal prognosis and is also one of the most commonly diagnosed malignancies worldwide. circRNAs are covalently closed circular RNA molecules without 5'-cap and a 3'-tail, currently listed among the broad noncoding RNA family. circRNAs participate in a variety of pathophysiological processes relevant to human diseases, especially malignancies, including GC. Compelling evidence has shown that circRNAs can function by sponging miRNAs, interacting with RNA binding proteins, and encoding proteins or peptides. Yet, our current understanding of these RNA circles remains very limited. Here, we overview the biogenesis, characteristics, functions, and degradation of circRNAs. Moreover, we give an account of the circRNAs that have been linked with GC, describing their functions and mechanisms of action in the context of GC. Next, we discuss the potential value of circRNAs as diagnostic or prognostic GC biomarkers and summarize future prospects, important questions, and challenges of circRNA-based therapeutics.

Contribution of circRNAs in gastric cancer

Gastric cancer (GC) is one of the most commonly diagnosed neoplasms in the world. A number of environmental and lifestyle factors, particularly chronic infection with Helicobacter pylori, have been found to partake in the pathogenesis of GC. The advent of high-throughput genome and transcriptome analysis has enhanced the knowledge about molecular mechanisms of the pathogenesis of GC. However, data regarding the expression of several circRNAs, such as circLMTK2, are not consistent. We explain the role of circRNAs in the development of GC. We searched databases for the newest publications using the terms gastric cancer and circRNA. Each circRNA alteration, downstream targets, its impacts on cancer cells, and the prognostic and diagnostic roles of these circRNAs have been discussed. Taken together, circRNAs can be putative biomarkers in GC and potential targets for the treatment of this cancer. Yet, this field is still in its infancy and needs further experiments for reaching the clinical application. As these transcripts are stable in circulation, they can be used in non-invasive methods of cancer detection and patients' follow-up.

Emerging roles of circular RNAs in neuropathic pain

Neuropathic pain is a major type of chronic pain caused by the disease or injury of the somatosensory nervous system. It afflicts about 10% of the general population with a significant proportion of patients’ refractory to conventional medical treatment. This highlights the importance of a better understanding of the molecular pathogenesis of neuropathic pain so as to drive the development of novel mechanism‐driven therapy. Circular RNAs (circRNAs) are a type of non‐coding, regulatory RNAs that exhibit tissue‐ and disease‐specific expression. An increasing number of studies reported that circRNAs may play pivotal roles in the development of neuropathic pain. In this review, we first summarize circRNA expression profiling studies on neuropathic pain. We also highlight the molecular mechanisms of specific circRNAs (circHIPK3, circAnks1a, ciRS‐7, cZRANB1, circZNF609 and circ_0005075) that play key functional roles in the pathogenesis of neuropathic pain and discuss their potential diagnostic, prognostic, and therapeutic utilization in the clinical management of neuropathic pain.

Circular RNA hsa_circ_0000073 Enhances Osteosarcoma Cells Malignant Behavior by Sponging miR-1252-5p and Modulating CCNE2 and MDM2

Objective: An increasing number of studies have demonstrated that circular RNAs (circRNAs) are involved in tumor progression. However, the role of hsa_circ_0000073 in osteosarcoma (OS) is still not fully elucidated.

Methods: Quantitative reverse transcription-polymerase chain reaction or Western blot was used to detect the gene expression. GeneChip analysis, bioinformatics, luciferase reporter, and RNA immunoprecipitation assays were adopted to predict and verify the relationships between genes. Counting Kit-8 Assay, clone formation assay, wound-healing assay, transwell assays, cell cycle assays, and in vivo tumorigenesis were used to evaluate cell function.

Results: hsa_circ_0000073 was highly expressed in OS cell lines and could promote OS progression, including proliferation, migration, invasion, and cell cycle in vitro as well as tumorigenesis in vivo. Mechanically, hsa_circ_0000073 could readily downregulate the expression of CCNE2 and MDM2 through miR-1252-5p. Rescue experiments validated miR-1252-5p mimics, or CCNE2/MDM2 short hairpin RNA could reverse the hsa_circ_0000073 overexpressing-induced impairment of malignant tumor behavior.

Conclusion: hsa_circ_0000073 functions as a tumor promoter in OS to increase malignant tumor behavior through sponging miR-1252-5p and regulating CCNE2 and MDM2 expression, which could be a novel target for OS therapy.

Emerging roles of circular RNAs in osteoporosis

Osteoporosis is one bone disease characterized with skeletal impairment, bone strength reduced and fracture risk enhanced. The regulation processes of bone metabolism are associated with several factors such as mechanical stimulation, epigenetic regulation and hormones. However, the mechanism of osteoporosis remains unsatisfactory. Increasing high‐throughput RNA sequencing and circular RNAs (circRNAs) microarray studies indicated that circRNAs are differentially expressed in osteoporosis. Growing functional studies further pinpointed specific deregulated expressed circRNAs (e.g., circ_28313, circ_0016624, circ_0006393, circ_0076906 and circ_0048211) for their functions involved in bone metabolism, including bone marrow stromal cells (BMSCs) differentiation, proliferation and apoptosis. Moreover, CircRNAs (circ_0002060, Circ_0001275 and Circ_0001445) may be acted as diagnostic biomarkers for osteoporosis. This review discussed recent progresses in the circRNAs expression profiling analyses and their potential functions in regulating BMSCs differentiation, proliferation and apoptosis.

Potential molecular mechanism of cardiac hypertrophy in mice induced by exposure to ambient PM2.5

Cardiac hypertrophy could be induced by ambient fine particulate matter (PM2.5) exposure. Since cardiac hypertrophy represents an early event leading to heart dysfunction, it is necessary to explore the molecular mechanisms, which are largely unknown. In the present study, an ambient particulate matter exposure mice model was established to explore its adverse effects related to the heart and the potential mechanisms. Forty-eight male C57BL/6 mice were randomly subjected to three groups: filtered air group, unfiltered air group and concentrated air group, and were exposed for 8 and 16 weeks, 6 h/day, respectively. In vitro experiments, the cardiac muscle cell line (HL-1) was treated with PM2.5 (0, 25, 50 and 100 μg/mL) for 24 h. In the present study, cardiac hypertrophy was occurred in vivo and vitro after exposure to PM2.5. Mechanistically, circ_0001859 could sponge miR-29b-3p, which could interact with 3'UTRs of Ctnnb1 (gene name of β-catenin). And Ctnnb1 expression was transcriptionally inhibited by si-circ_0001859 or miR-29b-3p mimic in HL-1 cells. Additionally, miR-29b-3p inhibitor could also make a reversion about the inhibition effect of circ_0001859 silencing on Ctnnb1 mRNA level in HL-1 cells. Functionally, knockout of circ_0001859 or overexpression of miR-29b-3p could inhibit LEF1/IGF-2R pathway and alleviate the progress of hypertrophy induced by PM2.5 in HL-1 cells. And miR-29b-3p inhibitor could reverse the inhibition effect of circ_0001859 silencing on hypertrophic response induced by PM2.5 in HL-1 cells. Consequently, the data demonstrated that circRNA_0001859 promoted the process of cardiac hypertrophy through suppressing miR-29b-3p leading to enhance Ctnnb1 level, and activated downstream pathway molecules LEF1/IGF-2R.

ALCAP2 inhibits lung adenocarcinoma cell proliferation, migration and invasion via the ubiquitination of β-catenin by upregulating the E3 ligase NEDD4L

Lung cancer is recognized as the leading cause of cancer-related death worldwide, with non-small cell lung cancer (NSCLC) being the predominant subtype, accounting for approximately 85% of lung cancer cases. Although great efforts have been made to treat lung cancer, no proven method has been found thus far. Considering β, β-dimethyl-acryl-alkannin (ALCAP2), a natural small-molecule compound isolated from the root of Lithospermum erythrorhizon. We found that lung adenocarcinoma (LUAD) cell proliferation and metastasis can be significantly inhibited after treatment with ALCAP2 in vitro, as it can induce cell apoptosis and arrest the cell cycle. ALCAP2 also significantly suppressed the volume of tumours in mice without inducing obvious toxicity in vivo. Mechanistically, we revealed that ALCAP2-treated cells can suppress the nuclear translocation of β-catenin by upregulating the E3 ligase NEDD4L, facilitating the binding of ubiquitin to β-catenin and eventually affecting the wnt-triggered transcription of genes such as survivin, cyclin D1, and MMP9. As a result, our findings suggest that targeting the oncogene β-catenin with ALCAP2 can inhibit the proliferation and metastasis of LUAD cells, and therefore, ALCAP2 may be a new drug candidate for use in LUAD therapeutics.

Circ_SMAD4 promotes gastric carcinogenesis by activating wnt/β-catenin pathway

Objectives

Circular RNAs (circRNAs) are essential participants in tumour progression. This study focused on investigating the mechanism of a novel functional circRNA in gastric cancer (GC).

Methods

Gene expression was detected by qRT‐PCR or Western blot. Survival curves were generated via Kaplan‐Meier method. In vitro and in vivo assays were used to investigate the impact of circ_SMAD4 on GC cell growth and tumorigenesis. Agarose gel electrophoresis assay, RNase R treatment and Sanger sequencing were utilized for confirming the circular structure of circ_SMAD4. Relationship between molecules was monitored by a series of mechanical experiments, as needed.

Results

Circ_SMAD4 expression was potentiated in GC. Circ_SMAD4 depletion impeded GC cell growth in vitro and restrained tumorigenesis in vivo. Mechanically, nuclear circ_SMAD4 recruited TCF4 to facilitate CTNNB1 transcription, while cytoplasmic circ_SMAD4 sequestered miR‐1276 to prevent the silence of CTNNB1 mRNA, leading to activation of Wnt/β‐catenin pathway. Rescue experiments validated that circ_SMAD4 depended on miR‐1276/TCF4‐regulated CTNNB1 to elicit accelerating effects on GC cell growth.

Conclusion

Circ_SMAD4 facilitated GC tumorigenesis by activating CTNNB1‐dependent Wnt/β‐catenin pathway. Hopefully, the findings could provide new clues for improving GC prognosis and treatment.