Circular RNAs as Biomarkers for Cancer

Circ-USP9X accelerates deep vein thrombosis after fracture by acting as a miR-148b-3p sponge and upregulates SRC kinase signaling inhibitor 1

OBJECTIVES

This study aims to elucidate the role of circUSP9X (Circular RNA Ubiquitin Specific Peptidase 9 X-Linked) in the development of venous thrombosis in the lower extremities.

METHODS

An animal model of Deep Vein Thrombosis (DVT) and a hypoxic model of Human Umbilical Vein Endothelial Cells (HUVECs) treated with Cobalt (II) Chloride (CoCl2) were developed. The expression levels of circUSP9X, microRNA-148b-3p (miR-148b-3p), and SRC Kinase Signaling Inhibitor 1 (SRCIN1) were quantified using quantitative reverse transcription Polymerase Chain Reaction and Western blot analysis. Cell cytotoxicity, viability, apoptosis, and inflammation in HUVECs were assessed via Lactate Dehydrogenase (LDH) assay, MTT assay, flow cytometry, Enzyme-Linked Immunosorbent Assay, and Western blot, respectively. Hematoxylin and Eosin staining were employed for histopathological examination of the venous tissues in the animal model. The interaction between circUSP9X, miR-148b-3p, and SRCIN1 was further explored through dual-luciferase reporter assays and RNA Immunoprecipitation experiments.

RESULTS

The present findings reveal a significant upregulation of circUSP9X and SRCIN1 and a concurrent downregulation of miR-148b-3p in DVT cases. Knockdown of circUSP9X or overexpression of miR-148b-3p ameliorated CoCl2-induced apoptosis in HUVECs, reduced LDH release, enhanced cellular viability, and mitigated inflammation. Conversely, overexpression of circUSP9X intensified CoCl2's cytotoxic effects. The effects of manipulating circUSP9X expression were counteracted by the corresponding modulation of miR-148b-3p and SRCIN1 levels. Additionally, circUSP9X knockdown effectively inhibited the formation of DVT in the mouse model. A competitive binding mechanism of circUSP9X for miR-148b-3p, modulating SRCIN1 expression, was identified.

CONCLUSION

circUSP9X promotes the formation of DVT through the regulation of the miR-148b-3p/SRCIN1 axis.

Circular RNA COL1A1 promotes Warburg effect and tumor growth in nasopharyngeal carcinoma

OBJECTIVE

Circular RNAs (circRNAs), pivotal in the pathogenesis and progression of nasopharyngeal carcinoma (NPC), remain a significant point of investigation for potential therapeutic interventions. Our research was driven by the objective to decipher the roles and underlying mechanisms of hsa_circ_0044569 (circCOL1A1) in governing the malignant phenotypes and the Warburg effect in NPC.

METHODS

We systematically collected samples from NPC tissues and normal nasopharyngeal epithelial counterparts. The expression levels of circCOL1A1, microRNA-370-5p (miR-370-5p), and prothymosin alpha (PTMA) were quantitatively determined using quantitative polymerase chain reaction (qPCR) and Western blotting. Transfections in NPC cell lines were conducted using small interfering RNAs (siRNAs) or vectors carrying the pcDNA 3.1 construct for overexpression studies. We interrogated the circCOL1A1/miR-370-5p/PTMA axis's role in cellular functions through a series of assays: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide for cell viability, colony formation for growth, Transwell assays for migration and invasion, and Western blotting for protein expression profiling. To elucidate the molecular interactions, we employed luciferase reporter assays and RNA immunoprecipitation techniques.

RESULTS

Our investigations revealed that circCOL1A1 was a stable circRNA, highly expressed in both NPC tissues and derived cell lines. A correlation analysis with clinical pathological features demonstrated a significant association between circCOL1A1 expression, lymph node metastasis, and the tumor node metastasis staging system of NPC. Functionally, silencing circCOL1A1 led to substantial suppression of cell proliferation, migration, invasion, and metabolic alterations characteristic of the Warburg effect in NPC cells. At the molecular level, circCOL1A1 appeared to modulate PTMA expression by acting as a competitive endogenous RNA or 'sponge' for miR-370-5p, which in turn promoted the malignant characteristics of NPC cells.

CONCLUSION

To conclude, our findings delineate that circCOL1A1 exerts its oncogenic influence in NPC through the modulation of the miR-370-5p/PTMA signaling axis.

Circular RNAs: An emerging precise weapon for diabetic nephropathy diagnosis and therapy

Diabetic nephropathy (DN) is a prevalent chronic microvascular complication associated with diabetes mellitus and represents a major cause of chronic kidney disease and renal failure. Current treatment strategies for DN primarily focus on symptom alleviation, lacking effective approaches to halt or reverse DN progression. Circular RNA (circRNA), characterized by a closed-loop structure, has emerged as a novel non-coding RNA regulator of gene expression, attributed to its conservation, stability, specificity, and multifunctionality. Dysregulation of circRNA expression is closely associated with DN progression, whereby circRNA impacts kidney cell injury by modulating cell cycle, differentiation, cell death, as well as influencing the release of inflammatory factors and stromal fibronectin expression. Consequently, circRNA is considered a predictive biomarker and a potential therapeutic target for DN. This review provides an overview of the latest research progress in the classification, functions, monitoring methods, and databases related to circRNA. The paper focuses on elucidating the impact and underlying mechanisms of circRNA on kidney cells under diabetic conditions, aiming to offer novel insights into the prevention, diagnosis, and treatment of DN.

Circ_103809 Aggravates the Malignant Phenotype of Pancreatic Cancer Through Modulating miR-197-3p/TSPAN3 Axis

Pancreatic cancer (PC) is a malignant tumor with insidious clinical manifestations and dismal prognosis. Emerging reports have demonstrated that circRNAs exert pivotal biological function in PC. Here, we investigated the crucial biological role and underlying regulatory mechanisms of differentially expressed circ_103809 in PC. In this study, hsa_circ_103809 (hsa_circ_0072088) was identified as the research object via analyzing and screening the aberrantly expressed circRNAs in PC by GSE69362 dataset. The levels of circ_103809 in PC tissues and cells were assessed via qRT-PCR. Functional assays were conducted to monitor the impacts of circ_103809 on PC cells. Additionally, the downstream molecular targets and regulatory networks of circ_103809 were predicted by bioinformatics and validated using luciferase assays and rescue experiments. We found that circ_103809 was substantially upregulated in PC tissues and cells. Silencing circ_103809 restrained the growth viability, clonogenic rate, migration, and invasion capabilities of PC cells. Further mechanistic exploration disclosed that miR-197-3p was the downstream gene of circ_103809, while Tetraspanin-3 (TSPAN3) was a direct target of miR-197-3p. The suppressive effect of circ_103809 knockdown on malignant processes of PC cells was eliminated by miR-197-3p downregulation or TSPAN3 upregulation. Our study demonstrated that circ_103809 served as an innovative positive regulator in the growth and metastasis of PC cells. Furthermore, circ_103809 mediated the miR-197-3p/TSPAN3 axis to modulate the malignant progression of PC cells, which was prospected to be a probable biomarker and an efficient therapeutic target for PC.

Circular RNA circSLC7A11 contributes to progression and stemness of laryngeal squamous cell carcinoma via sponging miR-877-5p from LASP1

Background

Laryngeal squamous cell carcinoma (LSCC) belongs to tumors of head and neck. Circular RNA circSLC7A11 functions as oncogenes in various tumors. However, the role of circSLC7A11 in LSCC remains largely unknown. Here, we aimed to clarify the circSLC7A11 function in LSCC.

Methods

Relevance between circSLC7A11 expressions and LSCC clinicopathological was checked using chi-square. Relevance between circSLC7A11 expressions and LSCC patients' survival time was validated using Kaplan-Meier analysis. CircSLC7A11 expressions in LSCC tissues and cells were determined using quantitative real-time PCR. CircSLC7A11 functions in LSCC were examined by Cell Counting Kit-8, EdU analysis, Western blot, flow cytometry, sphere formation assay, and Transwell analysis. Meanwhile, circSLC7A11 mechanism in LSCC was determined using dual-luciferase reporter analysis, RNA pull-down, RNA Immunoprecipitation.

Results

CircSLC7A11 was highly expressed in LSCC, and high circSLC7A11 expressions were interrelated to the TNM stage. Also, LSCC patients with high circSLC7A11 owned shorter overall survival. Functional studies revealed that circSLC7A11 knockdown reduced LSCC cell proliferation, migration, invasion, stemness characteristics, and enhanced cell apoptosis. Mechanistic study data corroborated that circSLC7A11 targeted miR-877-5p, miR-877-5p targeted LASP1. LASP1 was negatively interrelated to miR-877-5p and was positively interrelated to circSLC7A11 in LSCC tissues. Also, circSLC7A11 knockdown reduced the LASP1 levels, and miR-877-5p inhibitor co-transfection reversed this reduction. Rescue assays further demonstrated that circSLC7A11 accelerated LSCC through miR-877-5p/LASP1.

Conclusion

CircSLC7A11 exerted oncogenic functions in LSCC by miR-877-5p/LASP1, hinting that circSLC7A11 was a novel biomarker for LSCC.

Circular RNAs in hepatocellular carcinoma: Recent advances

Circular RNAs (circRNAs) have covalently closed loop structures at both ends, exhibiting characteristics dissimilar to those of linear RNAs. Emerging evidence suggests that aberrantly expressed circRNAs play crucial roles in hepatocellular carcinoma (HCC) by affecting the proliferation, apoptosis and invasive capacity of HCC cells. Certain circRNAs may be used as biomarkers to diagnose and predict the prognosis of HCC. Therefore, circRNAs are expected to become novel biomarkers and therapeutic targets for HCC. Herein, we briefly review the characteristics and biological functions of circRNAs, focusing on their roles in HCC to provide new insights for the early diagnosis and targeted therapy of HCC.

Circ_0085315 promotes cell proliferation, invasion, and migration in colon cancer through miR-1200/MAP3K1 signaling pathway

Colon cancer (CC) is a common malignant tumor of the digestive tract. Circular RNAs (circRNAs) play important roles in the progression of CC. This study aimed to explore the role and mechanism of circRNA_0085315 in CC. In this study, we used qRT-PCR and Western blot assays to analyze the expressions of circRNA, miRNA, and mRNA as well as the expression of the related proteins. Luciferase reporter, RNA pull-down, and qRT-PCR assays were used to prove the relationship among circRNA, miRNA, and mRNA. CCK-8, colony formation, and transwell assays were used to perform the analysis of cell proliferation, migration, and invasion. Our results showed that the higher circRNA_0085315 expression led to the poorer prognosis of CC patients. The function of circRNA_0085315 as a ceRNA in competing with MAP3K1 mRNA to sponge miR-1200. CircRNA_0085315 sponged miR-1200 to promote cell proliferation, migration, and invasion and affected the expression of Ki67, MMP2, E-cadherin, and N-cadherin, but not circRNA_0085315-mut without the binding site of miR-1200. MAP3K1-overexpression or miR-1200 mimics prevented the suppression on the enhanced cell proliferation, migration, and invasion caused by circRNA_0085315-overexpression. circRNA_0085315 increased the phosphorylation levels of JNK, p38, and ERK1/2 by stimulating MAP3K1 up-regulation caused by miR-1200 inhibition. In conclusion, circRNA_0085315 serves as a ceRNA and promotes CC progression through the activation of the MAPK signaling pathway mediated via the miR-1200/MAP3K1 axis, suggesting that circRNA_0085315 may be a promising diagnostic and therapeutic target for CC.

GEO Database Screening Combined with In Vitro Experiments to Study the Mechanism of hsa_circ_0003570 in Infantile Hemangiomas

Objective

In this study, we screened out a type of differentially expressed circular RNA in infantile hemangioma (IH) cells and analyzed the mechanism in the malignant biological behavior of IH.

Methods

Based on the GSE98795, GSE100682, and GSE43742 datasets, differential expression analysis of circRNAs, microRNAs, and mRNAs was performed. The relative expression level of RNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). MTT assay, Transwell, flow cytometry analysis, and western blot were used to study the effects of hsa_circ_0003570, hsa-miR-138-5p, and RGS5 on the proliferation and apoptosis of hemangioma endothelial cells (HEMECs).

Results

The hsa_circ_0003570 and RGS5 mRNA were upregulated in HEMECs, but hsa-miR-138-5p was downregulated. Silencing of hsa_circ_0003570 inhibited the proliferation of HEMECs and promoted the apoptosis of HEMECs. The malignant biological behaviors of hsa_circ_0003570 on the proliferation and apoptosis of HEMECs were reversed by hsa-miR-138-5p. Hsa_circ_0003570 acted as the ceRNA of hsa-miR-138-5p and upregulated the expression of RGS5. Silencing of RGS5 inhibited the proliferation, migration, and invasion of HEMECs and promoted apoptosis.

Conclusion

Hsa_circ_0003570 promotes IH cell proliferation and inhibits IH cell apoptosis through hsa-miR-138-5p/RGS5 axis.

Non-coding RNAs and macrophage interaction in tumor progression

The macrophages are abundantly found in TME and their M2 polarization is in favor of tumor malignancy. On the other hand, non-coding RNAs (ncRNAs) can modulate macrophage polarization in TME to affect cancer progression. The miRNAs can dually induce/suppress M2 polarization of macrophages and by affecting various molecular pathways, they modulate tumor progression and therapy response. The lncRNAs can affect miRNAs via sponging and other molecular pathways to modulate macrophage polarization. A few experiments have also examined role of circRNAs in targeting signaling networks and affecting macrophages. The therapeutic targeting of these ncRNAs can mediate TME remodeling and affect macrophage polarization. Furthermore, exosomal ncRNAs derived from tumor cells or macrophages can modulate polarization and TME remodeling. Suppressing biogenesis and secretion of exosomes can inhibit ncRNA-mediated M2 polarization of macrophages and prevent tumor progression. The ncRNAs, especially exosomal ncRNAs can be considered as non-invasive biomarkers for tumor diagnosis.

hsa_circ_0013401 Accelerates the Growth and Metastasis and Prevents Apoptosis and Autophagy of Neuroblastoma Cells by Sponging miR-195 to Release PAK2

Background

Increased levels of circRNAs have been identified in a variety of cancers. However, the specific functions and mechanisms of circRNAs in neuroblastoma (NB) have not been fully explored.

Methods

The levels of hsa_circ_0045997, hsa_circ_0080307, hsa_circ_0013401, hsa_circ_0077578, and microRNA-195 were confirmed by RT-qPCR in NB. Gain- and loss-of-function assays and rescue experiments were conducted to determine the influence of hsa_circ_0013401, miR-195, and P21-activated kinase 2 (PAK2) on the proliferation, apoptosis, autophagy, migration, and invasion of NB cells. Regulatory gene targets were validated by the luciferase assay. A xenograft mouse model was used to determine the in vivo effects of hsa_circ_0013401.

Results

hsa_circ_0013401 was highly expressed, miR-195 was lowly expressed, and there was a negative correlation between hsa_circ_0013401 and miR-195 in NB. The inhibitory effects of hsa_circ_0013401 knockdown suppressed the proliferation, migration, and invasion and induced the apoptosis and autophagy of NB cells by targeting miR-195 to downregulate PAK2 expression. Luciferase reporter assays showed that miR-195 was a direct target of hsa_circ_0013401, and PAK2 was the downstream target gene of miR-195. In vivo studies showed that hsa_circ_0013401 promotes tumor formation.

Conclusions

hsa_circ_0013401 induced NB progression through miR-195 to enhance PAK2. Therefore, we might highlight a novel regulatory axis (hsa_circ_0013401/miR-195/PAK2) in NB.

Circular RNA circFAT1(e2) Promotes Colorectal Cancer Tumorigenesis via the miR-30e-5p/ITGA6 Axis

circRNAs (circular RNAs) are a family of noncoding RNAs and have diverse physiological and pathological functions. However, the functions and mechanisms of circRNAs in the development and progression of colorectal cancer (CRC) remain largely unknown. Here, we aimed to explore the functions and roles of circFAT1(e2) in CRC. qRT-PCR revealed that circFAT1(e2) in CRC tumor tissues was upregulated compared with that in adjacent normal tissues and was also upregulated in CRC cell lines. Small interfering RNAs (siRNAs) against circFAT1(e2) were used to decrease the expression of circFAT1(e2) in HCT116 and RKO cells in vitro. The roles of circFAT1(e2) in CRC cell metastasis and proliferation were then determined by transwell and CCK-8 assays. The results showed that circFAT1(e2) silencing markedly suppressed CRC growth. Moreover, we identified circFAT1(e2) as a promoter of CRC metastasis. Knockdown of circFAT1(e2) evidently reduced HCT116 and RKO cell migration and invasion. Furthermore, the regulatory relationship between circFAT1(e2) and its target miRNAs was verified by a luciferase reporter assay. We demonstrated that circFAT1(e2) could sponge miR-30e-5p, which regulated the expression level of integrin α6 (ITGA6), the downstream target gene of miR-30e-5p. Rescue assays demonstrated that knockdown of miR-30e-5p enhanced CRC proliferation and migration via ITGA6. Taken together, our results reveal the novel oncogenic roles of circFAT1(e2) in CRC through the miR-30e-5p/ITGA6 axis.

CircUBAP2 Inhibits Proliferation and Metastasis of Clear Cell Renal Cell Carcinoma via Targeting miR-148a-3p/FOXK2 Pathway

Clear cell renal cell carcinoma (ccRCC) is the prominent histological subtype of renal cell carcinoma (RCC) with high incidence of local recurrence and distant metastasis. It has been documented that circular ribonucleic acids (circRNAs) play crucial roles in the development of cancers; however, study on exploring the role of circRNAs in ccRCC still remains limited. In the present study, we aimed to evaluate the biological function of a novel circRNA UBAP2 (circUBAP2) in ccRCC and the underlying mechanism. Our results showed that circUBAP2 expression was significantly down-regulated in ccRCC tissues and cell lines. Overexpression of circUBAP2 significantly inhibited the proliferation, migration, and invasion of ccRCC cells. MiR-148a-3p was a target miRNA of circUBAP2 in ccRCC cells, and its expression levels in ccRCC tissues and cell lines were negatively correlated with circUBAP2 levels. Moreover, miR-148a-3p reversed the inhibitory effects of circUBAP2 on cell proliferation, migration, and invasion in ccRCC cells. Additionally, forkhead box K2 (FOXK2) was found to be a target gene of miR-148a-3p and regulated by miR-148a-3p in ccRCC cells. Furthermore, knockdown of FOXK2 reversed the inhibitory effects of miR-148a-3p inhibitor on ccRCC cells. In conclusion, these findings indicated that circUBAP2 functioned as a novel tumor suppressor in ccRCC through regulating the miR-148a-3p/FOXK2 axis. Therefore, circUBAP2 might serve as a potential therapeutic target for the treatment of ccRCC.

Circular RNA circHIPK3 modulates prostate cancer progression via targeting miR-448/MTDH signaling

PURPOSE

Prostate cancer (PCa) is one of the most diagnosed cancers in men worldwide. Several studies have identified that circular RNAs (circRNAs) have a crucial impact on the biological processes in PCa. Therefore, it is necessary to study the molecular mechanism of circRNAs in tumor progression and metastasis.

METHODS

RNA interference was used to decrease circHIPK3 and MTDH expression. Overexpression vector was used to increase circHIPK3 and MTDH expression. Luciferase reporter assay were used to detect the relationship between circHIPK3 and miR-448 or between miR-448 and MTDH. MTT assay, colony formation assay and transwell assay were used to measure proliferation and migration of PCa cells.

RESULTS

Circular RNA circHIPK3 was significantly increased in PCa tissues and cell lines. And overexpression of circHIPK3 promoted the migration, proliferation, and invasion of PC-3 and 22Rv1 cells, while knockdown of circHIPK3 markedly repressed the above-mentioned series of biological processes. Furthermore, circHIPK3 promoted metadherin (MTDH) expression by sponging miR-448. In vivo experiments, it was also found that overexpression of circHIPK3 significantly promoted tumor growth.

CONCLUSIONS

Our research shows that circHIPK3 plays a carcinogenic effect in PCa by regulating the miR-448/MTDH axis, indicating that circHIPK3 may be a potential therapeutic target for PCa.

circTLK1 facilitates the proliferation and metastasis of renal cell carcinoma by regulating miR-495-3p/CBL axis

Renal cell carcinoma (RCC) is a common urological malignancy. Circular RNAs (circRNAs) have been confirmed to play an important regulatory role in various cancers. This study aimed to investigate the role and potential mechanism of circTLK1 (hsa_circ_0004442) in RCC. The levels of circTLK1, Cbl proto-oncogene (CBL), and microRNA-495-3p (miR-495-3p) were detected by quantitative reverse transcription polymerase chain reaction or western blot. Cell proliferation, cycle arrest and apoptosis, migration, and invasion were assessed by colony formation, flow cytometry, scratch, and transwell assays. The levels of E-cadherin and Vimentin were measured by western blot. The targeting relationship between miR-495-3p and miR-495-3p or CBL was verified by dual-luciferase reporter assay. Tumor growth in vivo was evaluated by xenograft assay. The results found that circTLK1 and CBL were up-regulated in RCC tissues and cells. Silencing of circTLK1 or CBL inhibited proliferation and metastasis and accelerated apoptosis in RCC cells. In addition, circTLK1 directly bound to miR-495-3p, and CBL was the target of miR-495-3p. circTLK1 sponged miR-495-3p to increase CBL expression. Moreover, knockdown of circTLK1 suppressed tumor growth in vivo. In conclusion, down-regulation of circTLK1 restrained proliferation and metastasis and promoted apoptosis in RCC cells by modulating miR-495-3p/CBL axis.

Circular RNA circSPATA6 Inhibits the Progression of Oral Squamous Cell Carcinoma Cells by Regulating TRAF6 via miR-182

Background

Oral squamous cell carcinoma (OSCC) has become a widely concerned social problem. Circular RNA spermatogenesis-associated protein 6 (circSPATA6) exhibited low expression in OSCC tissues, yet the regulatory mechanism of circSPATA6 remains vague.

Methods

Levels of circSPATA6, linear SPATA6, microRNA-182 (miR-182), and tumor necrosis factor receptor-associated factor 6 (TRAF6) were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Migration, invasion, cell cycle arrest, and apoptosis were assessed by Wound-healing, Matrigel invasion, and Flow cytometry assays. The binding relationship between miR-182 and circSPATA6 or TRAF6 was predicted by circRNA interactome or DIANA TOOL and then proved by the dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays. TRAF6 protein level was measured by Western blot assay. The biological role of circSPATA6 on OSCC tumor growth was analyzed by xenograft tumor model in vivo. Exosomes were isolated and detected by differential centrifugation and a transmission electron microscope.

Results

CircSPATA6 and TRAF6 were declined, and miR-182 was elevated in OSCC cells. Functionally, circSPATA6 impeded migration and invasion, and facilitated cell cycle arrest and apoptosis of OSCC cells. Mechanistically, circSPATA6 could modulate TRAF6 expression through sponging miR-182. Moreover, circSPATA6 blocked tumor growth in the OSCC mice model. Exosomal circSPATA6 retarded the growth of OSCC cells.

Conclusion

CircSPATA6 curbed migration and invasion, and expedited cell cycle arrest and apoptosis in OSCC cells partly through regulating the miR-182/TRAF6 axis. These findings hinted at an underlying circRNA-targeted therapy for OSCC.

MiR-302b Suppresses Tumor Metastasis by Targeting Frizzled 6 in OSCC

Oral squamous cell carcinoma (OSCC) accounts for approximately 90% of malignant epithelial tumors of the oral and maxillofacial region. OSCC has high rate of metastasis and poor prognosis. Tobacco and/or alcohol consumption and human papillomavirus infection are relatively exact susceptibility factors for OSCC, but the specific process of oral mucosal carcinogenesis and progression is very complicated. microRNA-302b (miR-302b) could regulate various characteristics of many tumor cells, such as proliferation and apoptosis, but its role and mechanism in OSCC have not been reported. This research aims to study the effect of miR-302b on the invasion and migration ability of OSCC and the mechanism by which it functions as well as to identify new prognostic indicators and therapeutic targets for OSCC patients. Functional studies showed that the miR-302b level was negatively correlated with the invasion and migration ability of OSCC. The studies also showed that the overexpression of miR-302b could attenuate the invasion and migration ability of OSCC cells and reduce lymphangiogenesis and the lung metastasis rate of OSCC cells in a mouse model. Mechanistic studies were performed by quantitative polymerase chain reactions, luciferase assays, and RNA pull-down experiments. The results verified that frizzled class receptor 6 (FZD6) is a target gene of miR-302b in OSCC that could promote cell invasion and migration. Clinical studies demonstrate that the protein expression level of FZD6 was higher in OSCC and metastatic lymph nodes than in normal oral mucosa epithelium. Taken together, these data showed that miR-302b could inhibit the invasion and migration ability of OSCC cells by targeting and downregulating FZD6, thereby inhibiting OSCC metastasis. As a new target gene of miR-302b, FZD6 has the potential to become a prognostic and therapeutic target for OSCC patients.

Circular RNA AKT3 governs malignant behaviors of esophageal cancer cells by sponging miR-17-5p

BACKGROUND

Recent studies have demonstrated that circular RNA AKT3 (circAKT3) plays a crucial role in regulating the malignant phenotypes of tumor cells. However, the potential effects of circAKT3 on esophageal cancer have not been investigated.

AIM

To illuminate the role of circAKT3 in malignant behaviors of esophageal cancer cells and its underlying mechanism.

METHODS

Clinical samples were collected to detect the expression of circAKT3. The role of circAKT3 in proliferation, migration, invasion, and apoptosis of esophageal cancer cells was evaluated using Cell Counting Kit-8, wound healing assays, Transwell assays, and fluorescence analysis, respectively. The target of circAKT3 was screened and identified using an online database and luciferase reporter assay. A xenograft nude mouse model was established to investigate the role of circAKT3 in vivo.

RESULTS

In vitro assays showed that proliferative, migratory, and invasive capacities of esophageal cancer cells were significantly enhanced by circAKT3 overexpression. Furthermore, miR-17-5p was screened as the target of circAKT3, and miR-17-5p antagonized the effects of circAKT3 on esophageal cancer cells. Moreover, we identified RHOC and STAT3 as the direct target molecules of miR-17-5p, and circAKT3 facilitated expression of RHOC and STAT3 by inhibiting miR-17-5p. In vivo assays showed circAKT3 knockdown inhibited growth of esophageal cancer.

CONCLUSION

CircAKT3 contributed to the malignant behaviors of esophageal cancer in vitro and in vivo by sponging miR-17-5p thus providing a potential target for treatment of esophageal cancer.

circCRKL suppresses the progression of prostate cancer cells by regulating the miR-141/KLF5 axis

BACKGROUND

Prostate cancer (PCa) is a prevalent human malignancy in males. Circular RNA circCRKL (Hsa_circ_0001206) was reported to be lowly expressed in PCa tissues. However, the regulatory role of circCRKL in PCa is poorly defined.

METHODS

Levels of circCRKL, microRNA-141 (miR-141), and Kruppel-like factor (KLF5) were measured by real-time quantitative polymerase chain reaction (RT-qPCR). Cell cycle progression, apoptosis, migration, and invasion were examined by Flow cytometry, Wound healing, and transwell assays. The underlying relationship between miR-141 and circCRKL or KLF5 was predicted by starBase, and then verified by a dual-luciferase reporter, RNA Immunoprecipitation (RIP), and RNA pull-down assays. The protein level of KLF5 was assessed by western blot assay. The biological role of circCRKL was detected by a xenograft tumor model in vivo.

RESULTS

CircCRKL and KLF5 were decreased, and miR-141 was increased in PCa tissues and cells. The functional analysis discovered that the overexpression of circCRKL repressed cell cycle progression, migration, invasion, and boosted apoptosis of PCa cells. Mechanically, circCRKL could positively regulate KLF5 expression by sponging miR-141. In addition, circCRKL upregulation could hinder PCa tumor growth in vivo.

CONCLUSION

These findings revealed that circCRKL inhibited the progression of PCa through upregulating KLF5 expression by sponging miR-141, elucidating a novel regulatory pathway in PCa cells. Our research suggested an underlying circRNA-targeted therapy for PCa.

Circular RNA profiling in plasma exosomes from patients with gastric cancer

Gastric cancer (GC) is among the most common cancer types worldwide with high mortality. Recent studies have shown that exosomes play a crucial role in the tumorigenesis of GC. The present study aimed to investigate the circular RNA (circRNA) profile in plasma exosomes from patients with gastric cancer (GC). Peripheral blood samples were collected from 5 patients with GC and 5 healthy donors, and exosomes were isolated from plasma. The high-throughput RNA sequencing (RNA-seq) method was applied to detect the differently expressed circRNAs (DE circRNAs). Subsequently, sequencing results were confirmed by reverse transcription quantitative (RT-q) PCR. The potential roles of DE circRNAs in GC were identified using Gene ontology (GO) and Kyoto Encyclopedia of Gene and Genome (KEGG) analysis. Furthermore, MiRanda software was used to predict circRNA-micro-RNA (miRNA) interactions. A total of 67,880 circRNAs were identified in all samples and 1,060 significantly DE circRNAs were screened, including 620 upregulated and 440 downregulated ones. These results were further confirmed by RT-qPCR. GO and KEGG analyses revealed that these circRNAs were significantly associated with ‘cell cycle’, ‘cytoskeleton organization’, ‘cellular response to DNA damage’, ‘regulation of GTPase activity’, ‘phosphatidylinositol signaling pathway’, ‘MAPK signaling pathway’, ‘thyroid hormone signaling pathway’, ‘chemokine signaling pathway’ and ‘Wnt signaling pathway’. In addition, a circRNA-miRNA-mRNA interaction network was established. Taken together, these findings may help better understanding the underlying mechanisms of GC and identifying new molecular alterations in GC, and allow the enrichment of the circRNA profiling in human GC.

Circular RNA PVT1 promotes metastasis via regulating of miR-526b/FOXC2 signals in OS cells

As a class of covalently closed non-coding RNAs, circular RNAs (circRNAs) are key regulators in various malignancies including osteosarcoma (OS). In the present study, we found that circular RNA PVT1 (circPVT1) was up-regulated in OS and correlated with poor prognosis of patients with OS. Functionally, we showed that knockdown of circPVT1 suppressed OS cells metastasis. In addition, we found that (forkhead box C2) FOXC2 was a downstream gene in circPVT1-mediated metastasis in OS cells. We demonstrated that circPVT1 promoted OS cells metastasis via post-transcriptionally regulating of FOXC2. Furthermore, we revealed that microRNA 526b (miR-526b) was a key bridge which connected circPVT1 and FOXC2. We showed that miR-526b was down-regulated in OS tissue and cell lines. Through a transwell assay, we found that miR-526b suppressed OS cells metastasis by targeting of FOXC2. We also showed that miR-526b targeted circPVT1 via similar mircoRNA response elements (MREs) as it did for FOXC2. Finally, we proved that circPVT1 decoyed miR-526b to promote FOXC2-mediated metastasis in OS cells. In brief, our current study demonstrated that circPVT1, functioning as an oncogene, promotes OS cells metastasis via regulation of FOXC2 by acting as a ceRNA of miR-526b. CircPVT1/miR-526b/FOXC2 axis might be a novel target in molecular treatment of OS.

Circular RNAs as potential biomarkers and therapeutics for cardiovascular disease

Circular RNAs (circRNAs) are genetic regulators that were earlier considered as "junk". In contrast to linear RNAs, they have covalently linked ends with no polyadenylated tails. CircRNAs can act as RNA-binding proteins, sequestering agents, transcriptional regulators, as well as microRNA sponges. In addition, it is reported that some selected circRNAs are transformed into functional proteins. These RNA molecules always circularize through covalent bonds, and their presence has been demonstrated across species. They are usually abundant and stable as well as evolutionarily conserved in tissues (liver, lung, stomach), saliva, exosomes, and blood. Therefore, they have been proposed as the "next big thing" in molecular biomarkers for several diseases, particularly in cancer. Recently, circRNAs have been investigated in cardiovascular diseases (CVD) and reported to play important roles in heart failure, coronary artery disease, and myocardial infarction. Here, we review the recent literature and discuss the impact and the diagnostic and prognostic values of circRNAs in CVD.

Circular RNA PVT1 promotes metastasis via miR-145 sponging in CRC

Circular RNAs (circRNAs) are a class of covalently closed non-coding RNAs and are widely involved in various cancers including colorectal cancer (CRC). Circular RNA PVT1 (circPVT1) was reported in several malignancies but the role it plays in CRC remains unclear. In our current research, we focused on the expression and function of circPVT1) works in CRC. We found that circPVT1 was upregulated in CRC. Also, we illustrated that the upregulated circPVT1 was closely correlated with poor prognosis and bad clinicopathological features of patients with CRC. Through a loss of function experiment, we showed that a downregulation of circPVT1 suppressed CRC cells metastasis. Through online prediction, we found that circPVT1 had a microRNA response element (MRE) for miR-145. Additionally, we demonstrated that miR-145 was downregulated in CRC. Even further, we showed that miR-145 was involved in circPVT1 mediated facilitation of CRC metastasis. In a further mechanical study, we demonstrated that circPVT1 could target miR-145. Lastly, we revealed that the metastasis-promoting role of circPVT1 in CRC was partially achieved via miR-145 sponging. In brief, the findings of the present study illustrated that circPVT1, working as an oncogene, promotes metastasis via miR-145 sponging in CRC. CircPVT1/miR-145 axial might be a novel point in targeting treatment of CRC.

circEPSTI1 regulates ovarian cancer progression via decoying miR-942

Increasing studies show that circular RNAs (circRNAs) play vital roles in tumour progression. But, how circRNAs function in ovarian cancer is mostly unclear. Here, we detected the expression of circEPSTI1 in ovarian cancer and explored the function of circEPSTI1 in ovarian cancer via a series of experiments. Then, we performed luciferase assay and RNA immunoprecipitation (RIP) assay to explore the competing endogenous RNA (ceRNA) function of circEPSTI1 in ovarian cancer. qRT-PCR verified that circEPSTI1 was overexpressed in ovarian cancer. Inhibition of circEPSTI1 suppressed ovarian cancer cell proliferation, invasion but promoted cell apoptosis. Luciferase assays and RIP assay showed that circEPSTI1 and EPSTI1 (epithelial stromal interaction 1) could directly bind to miR-942. And circEPSTI1 could regulate EPSTI1 expression via sponging miR-942. In summary, circEPSTI1 regulated EPSTI1 expression and ovarian cancer progression by sponging miR-942. circEPSTI1 could be used as a biomarker and therapeutic target in ovarian cancer.