Global circular RNA expression profile of human gastric cancer and its clinical significance

Advanced approaches of the use of circRNAs as a replacement for cancer therapy

Cancer is a broad name for a group of diseases in which abnormal cells grow out of control and are characterized by their complexity and recurrence. Although there has been progress in cancer therapy with the entry of precision medicine and immunotherapy, cancer incidence rates have increased globally. Non-coding RNAs in the form of circular RNAs (circRNAs) play crucial roles in the pathogenesis, clinical diagnosis, and therapy of different diseases, including cancer. According to recent studies, circRNAs appear to serve as accurate indicators and therapeutic targets for cancer treatment. However, circRNAs are promising candidates for cutting-edge cancer therapy because of their distinctive circular structure, stability, and wide range of capabilities; many challenges persist that decrease the applications of circRNA-based cancer therapeutics. Here, we explore the roles of circRNAs as a replacement for cancer therapy, highlight the main challenges facing circRNA-based cancer therapies, and discuss the key strategies to overcome these challenges to improve advanced innovative therapies based on circRNAs with long-term health effects.

DETHACDA: A Dual-View Edge and Topology Hybrid Attention Model for CircRNA-Disease Associations Prediction

There exists growing evidence that circRNAs are concerned with many complex diseases physiological processes and pathogenesis and may serve as critical therapeutic targets. Identifying disease-associated circRNAs through biological experiments is time-consuming, and designing an intelligent, precise calculation model is essential. Recently, many models based on graph technology have been proposed to predict circRNA-disease association. However, most existing methods only capture the neighborhood topology of the association network and ignore the complex semantic information. Therefore, we propose a Dual-view Edge and Topology Hybrid Attention model for predicting CircRNA-Disease Associations (DETHACDA), effectively capturing the neighborhood topology and various semantics of circRNA and disease nodes in a heterogeneous network. The 5-fold cross-validation experiments on circRNADisease indicate that the proposed DETHACDA achieves the area under receiver operating characteristic curve of 0.9882, better than four state-of-the-art calculation methods.

Circ_0003789 Knockdown Inhibits Tumor Progression by miR-429/ZFP36L2 Axis in Gastric Cancer

An increasing number of circRNAs have been found to be involved in the development of gastric cancer. However, the function of circ_0003789 in regulating gastric cancer progression is unclear. Here, we aimed to investigate the expression, function and molecular mechanism of circ_0003789 in gastric cancer pathogenesis. Circ_0003789, miR-429 and ZFP36 ring finger protein like 2 (ZFP36L2) mRNA were quantified by quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was illustrated by 5-Ethynyl-2'-deoxyuridine (Edu), cell counting kit-8 (CCK-8) and colony formation assays. Apoptosis was determined by flow cytometry. Protein level was detected by Western blotting assay. Xenograft assays were used for functional analysis of circ_0003789 in vivo. The relationship between miR-429 and circ_0003789 or ZFP36L2 was predicted by starbase3.0 online database and identified by dual luciferase reporter assay. The expression levels of circ_0003789 and ZFP36L2 were significantly upregulated in gastric cancer tissues and cells, while the expression of miR-429 was downregulated. Downregulation of circ_0003789 inhibited gastric cancer cell growth and invasion and promoted apoptosis in vitro. Circ_0003789 acted as a sponge of miR-429. Moreover, miR-429 silencing by miR-429 inhibitors attenuated the effects of circ_0003789 interference on cell growth, apoptosis and invasion. ZFP36L2 was targeted by miR-429, and the effects of miR-429 on cell growth, invasion and apoptosis were attenuated by ZFP36L2 overexpression. Circ_0003789 could enhance ZFP36L2 expression by interacting with miR-429. Silencing of circ_0003789 inhibited tumor growth in vivo. Circ_0003789 regulates tumor progression in gastric cancer through miR-429/ZFP36L2 axis. This finding implies that circ_0003789 may be a therapeutic target for gastric cancer.

Potential therapeutic targets of gastric cancer explored under endogenous network modeling of clinical data

Improvement in the survival rate of gastric cancer, a prevalent global malignancy and the leading cause of cancer-related mortality calls for more avenues in molecular therapy. This work aims to comprehend drug resistance and explore multiple-drug combinations for enhanced therapeutic treatment. An endogenous network modeling clinic data with core gastric cancer molecules, functional modules, and pathways is constructed, which is then transformed into dynamics equations for in-silicon studies. Principal component analysis, hierarchical clustering, and K-means clustering are utilized to map the attractor domains of the stochastic model to the normal and pathological phenotypes identified from the clinical data. The analyses demonstrate gastric cancer as a cluster of stable states emerging within the stochastic dynamics and elucidate the cause of resistance to anti-VEGF monotherapy in cancer treatment as the limitation of the single pathway in preventing cancer progression. The feasibility of multiple objectives of therapy targeting specified molecules and/or pathways is explored. This study verifies the rationality of the platform of endogenous network modeling, which contributes to the development of cross-functional multi-target combinations in clinical trials.

Exploring non-coding RNA mechanisms in hepatocellular carcinoma: implications for therapy and prognosis

Hepatocellular carcinoma (HCC) is a significant contributor to cancer-related deaths in the world. The development and progression of HCC are closely correlated with the abnormal regulation of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Important biological pathways in cancer biology, such as cell proliferation, death, and metastasis, are impacted by these ncRNAs, which modulate gene expression. The abnormal expression of non-coding RNAs in HCC raises the possibility that they could be applied as new biomarkers for diagnosis, prognosis, and treatment targets. Furthermore, by controlling the expression of cancer-related genes, miRNAs can function as either tumor suppressors or oncogenes. On the other hand, lncRNAs play a role in the advancement of cancer by interacting with other molecules within the cell, which, in turn, affects processes such as chromatin remodeling, transcription, and post-transcriptional processes. The importance of ncRNA-driven regulatory systems in HCC is being highlighted by current research, which sheds light on tumor behavior and therapy response. This research highlights the great potential of ncRNAs to improve patient outcomes in this difficult disease landscape by augmenting the present methods of HCC care through the use of precision medicine approaches.

Non-Coding RNA as Biomarkers and Their Role in the Pathogenesis of Gastric Cancer-A Narrative Review

Non-coding RNAs (ncRNAs) represent a broad family of molecules that regulate gene expression, including microRNAs, long non-coding RNAs and circular RNAs, amongst others. Dysregulated expression of ncRNAs alters gene expression, which is implicated in the pathogenesis of several malignancies and inflammatory diseases. Gastric cancer is the fifth most frequently diagnosed cancer and the fourth most common cause of cancer-related death. Studies have found that altered expression of ncRNAs may contribute to tumourigenesis through regulating proliferation, apoptosis, drug resistance and metastasis. This review describes the potential use of ncRNAs as diagnostic and prognostic biomarkers. Moreover, we discuss the involvement of ncRNAs in the pathogenesis of gastric cancer, including their interactions with the members of major signalling pathways.

Circular RNA CircSLC22A23 Promotes Gastric Cancer Progression by Activating HNRNPU Expression

BACKGROUND

Circular RNAs (CircRNAs) play essential roles in cancer occurrence as regulatory RNAs. However, circRNA-mediated regulation of gastric cancer (GC) remains poorly understood.

AIM

The purpose of this study was to investigate the molecular mechanism of circSLC22A23 (hsa_circ_0075504) underlying GC occurrence.

METHODS

CircSLC22A23 levels were first quantified by quantitative real-time reverse transcription-polymerase chain reaction in GC cell lines, 80 paired GC tissues and adjacent normal tissues, and 27 pairs of plasma samples from preoperative and postoperative patients with GC. Then circSLC22A23 was knocked-down with short hairpin RNA to analyze its oncogenic effects on the proliferation, migration, and invasion of GC cells. Finally, circRNA-binding proteins and their downstream target genes were identified by RNA pulldown, mass spectrometry, RNA immunoprecipitation, quantitative real-time reverse transcription-polymerase chain reaction, and Western blot assays.

RESULTS

CircSLC22A23 was found to be highly expressed in GC cells, GC tissues, and plasma from GC patients. Knockdown of circSLC22A23 inhibited GC cell proliferation, migration and invasion. RNA pulldown and RNA immunoprecipitation assays verified the interaction between circSLC22A23 and heterogeneous nuclear ribonucleoprotein U (HNRNPU). Knockdown of circSLC22A23 decreased HNRNPU protein levels. Moreover, rescue assays showed that the tumor suppressive effect of circSLC22A23 knockdown was reversed by HNRNPU overexpression. Finally, epidermal growth factor receptor (EGFR) was found to be one of the downstream target genes of HNRNPU that was up regulated by circSLC22A23.

CONCLUSION

CircSLC22A23 regulated the transcription of EGFR through activation of HNRNPU in GC cells, suggesting that circSLC22A23 may serve as a potential therapeutic target for the treatment of GC.

Deregulation of circRNA hsa_circ_0009109 promotes tumor growth and initiates autophagy by sponging miR-544a-3p in gastric cancer

Background

Autophagy death of cancer cells is detrimental to apoptosis induced by therapeutic drugs, which promotes tumor progression to a certain extent. Increasing reports have demonstrated the regulatory role of circular RNAs (circRNAs) in autophagy. Here, we aimed to determine the role of hsa_circ_0009109 in autophagy in gastric cancer (GC).

Methods

The effects of hsa_circ_0009109 on autophagy were examined using quantitative real-time polymerase chain reaction (qPCR), transmission electron microscopy, Western blot, and immunofluorescence. The mechanism of hsa_circ_0009109 regulating the miR-544a-3p/bcl-2 axis was analysed using fluorescence in situ hybridization, dual-luciferase reporter, and rescue experiments.

Results

Functional testing indicated that hsa_circ_0009109 was significantly down-expressed in GC tissues and cell lines. A reduction in cytoplasmic-derived hsa_circ_0009109 could promote GC progression by accelerating cell proliferation, enhancing migration and invasion, inhibiting apoptosis, and accelerating the cell cycle progression. Besides, hsa_circ_0009109 was found to exert the effect of an autophagy inhibitor such as 3-Methyladenine (3-MA), which was manifested by the weakening of the immunofluorescence of LC3B and the reduction in autophagy-related proteins after overexpression of hsa_circ_0009109, while increased autophagosomes were observed after interference with hsa_circ_0009109. Subsequently, the crosstalk between hsa_circ_0009109 and miR-544a-3p/bcl-2 was verified using dual-luciferase reporter assay. The autophagy status was altered under the regulation of the hsa_circ_0009109-targeted miR-544a-3p/bcl-2 axis.

Conclusions

The hsa_circ_0009109 mediated a novel autophagy regulatory network through targeting the miR-544a-3p/bcl-2 axis, which may shed new light on the exploration of therapeutic targets for the clinical treatment of GC.

CircHLA-C: A significantly upregulated circRNA co-existing in oral leukoplakia and oral lichen planus

BACKGROUND

Oral leukoplakia (OLK) and oral lichen planus (OLP) are common precancerous lesions of the oral mucosa. The role of circular RNAs (circRNAs) in OLK and OLP is unclear. The aim of this study was to evaluate the circRNA expression profiles of OLK and OLP, and further explore the potential role of circRNAs in the pathogenesis of these two diseases.

METHODS

High throughput sequencing technology was performed to detect the differentially expressed circRNA in OLK (n = 6), OLP (n = 6), oral squamous cell carcinoma (n = 6), and normal oral mucosa tissues (n = 6). Expression of selected circRNAs was validated by qRT-PCR, enzyme tolerance assay, and Sanger sequencing. Expanded sample size validation was done in 20 tissue pairs. The biological processes and signal pathways involved in differential circRNA were analyzed by GO and KEGG enrichment. TargetScan and MiRanda were used to predict miRNAs downstream of circRNA and draw competitive endogenous RNA network diagram.

RESULTS

Forty-nine circRNAs were significantly altered in OLK and OLP, including 30 upregulated and 19 downregulated circRNAs. The five selected circRNAs were validated by qRT-PCR, Sanger sequencing, and RNase R assay. GO and KEGG analyses indicated that the upregulated circHLA-C may be involved in the biological process of immune function of OLK and OLP. Bioinformatics analysis indicated that circHLA-C may be involved in the progression of OLK and OLP as a ceRNA. In validation with expanded sample size, PCR results showed that circHLA-C expression was significantly upregulated in OLK and OLP. ROC analysis indicated that circHLA-C has potential diagnostic value with good accuracy and specificity.

CONCLUSION

Our study revealed that circHLA-C is the most significantly upregulated circRNA co-existing in OLK and OLP, and we preliminarily discuss the role of circHLA-C in the etiopathogenesis and progression of OLK and OLP.

Identification of a valuable gene network for the diagnosis and treatment of non-obstructive azoospermia: in-silico analyses - experimental research

Introduction

Non-obstructive azoospermia (NOA) is an etiology of infertility in men. NOA may have various classifications; however, hypogonadotropic hypogonadism can be regarded as a class of NOA associated with genetic factors. Former studies have shown that noncoding RNA (ncRNA) plays an essential role in NOA incidence, but few studies have been performed on the NOA-related ncRNA interaction network. In the current study, genes, NOA-related microRNA (miRNA), and circular RNA (circRNA) were found by bioinformatics methods to offer a new perspective on NOA treatment.

Methods

The gonadotropin-releasing hormone receptor (GnRHR)-related protein-protein interaction (PPI) network was extracted by searching in 'string-database'. GO, KEGG, and Enrichr databases were used to identify pathways, molecular function, and biological processing. Four databases, including TargetScan, mirDIP, miRmap, and miRWalk, were used to extract miRNAs. At last, the circ2GO, circBase, and literature were used to identify circRNAs and their genes.

Results

The current study identified the four proteins associated with the GnRHR signaling; eight shared miRNAs that affect the expression of found proteins and 25 circRNAs and their origin genes that regulate the miRNAs' function.

Conclusion

The two miRNAs, hsa-miR-134-3p and hsa-miR-513C-3p, the three genes, VCAN, NFATC3, and PRDM5, and their associated circRNAs can perform as a valuable gene network in the diagnosis and treatment of NOA pathogenesis.

Identification of circRNA-associated ceRNA networks in peripheral blood mononuclear cells as potential biomarkers for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), which is a common respiratory disorder with high morbidity and mortality globally, has a complex pathogenesis that is not fully understood. Some circular RNAs (circRNAs) have been recognized to serve as miRNA sponges for regulating target RNA transcripts during the processes of human diseases. In the present study, we aimed to investigate novel circRNA-associated biomarkers for COPD, 245 differentially expressed circRNAs were identified, including 111 up-regulated and 134 down-regulated circRNAs. These candidate circRNAs were enriched in inflammation-associated pathways (such as mTOR, B-cell receptor, and NF-κB signaling pathways) via Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses. A combination of two circRNAs (up-regulated hsa_circ_0067209 and down-regulated hsa_circ_0000673) demonstrated good diagnostic value (area under the receiver operating characteristic curve [AUC] = 0.866) for COPD by receiver operating characteristic curve (ROC) analysis and qRT-PCR validation. Subsequently, hsa-miR-8082 and hsa-miR-1248 were identified as targets for hsa_circ_0067209 and hsa_circ_0000673, respectively, via bioinformatics analysis and a dual-luciferase reporter assay, and the combination of these two miRNAs displayed better diagnosis potential for COPD (AUC = 0.967) than each other. Evaluation of COPD-related mRNA profiles revealed that the up-regulated genes ABR and TRPM6 were predicted downstream targets for hsa_circ_0067209/hsa-miR-8082, whereas the down-regulated gene RORC was a predicted downstream target for hsa_circ_0000673/hsa-miR-1248. In summary, hsa_circ_0067209 and hsa_circ_0000673 have potential as novel diagnostic biomarkers of COPD. In addition, competing endogenous RNA networks of hsa_circ_0067209/hsa-miR-8082/ABR/TRPM6 and hsa_circ_0000673/hsa-miR-1248/RORC may play critical regulation roles for COPD pathogenesis.

Expression of plasma exosomal circLPAR1 in patients with gastric cancer and its clinical application value

OBJECTIVE

To determine plasma exosomal circular RNA LPAR1 (circLPAR1) expression in gastric cancer (GC) and analyze its clinical value in GC diagnosis and prognosis evaluation.

METHODS

The research subjects were 64 GC patients, 30 chronic gastritis (CG) patients (disease control group) and 30 healthy controls (HCs; healthy control group). RT-PCR quantified circLPAR1 expression in GC tissues and adjacent counterparts of GC patients as well as plasma exosomal circLPAR1 in each group. The correlation of differentially expressed circLPAR1 with clinicopathological indexes was analyzed, and receiver operating characteristics (ROC) and Kaplan-Meier curves were drawn to evaluate the value of plasma exosomal circLPAR1 in GC diagnosis and prognosis assessment.

RESULTS

GC patients exhibited lower plasma exosomal circLPAR1 levels than CG patients and HCs (P<0.05). Lower circLPAR1 expression was determined in GC tissues than in adjacent counterparts (P<0.05), and a positive connection between GC tissue circLPAR1 and plasma exosomal circLPAR1 was identified in GC patients (P<0.05). Evidently elevated plasma exosomal circLPAR1 was observed in post-surgical GC patients (P<0.05). ROC curves showed that the areas under the curve (AUCs) of plasma exosomal circLPAR1, serum carcinoembryonic antigen (CEA), and serum carbohydrate antigen 19-9 (CA19-9) for the diagnosis of GC were 0.836, 0.767 and 0.746, respectively, and the AUC of their combined diagnosis was 0.914. Low plasma exosomal circLPAR1 was strongly linked to tumor size, differentiation degree, tumor-node-metastasis (TNM) staging, vascular invasion, lymphatic metastasis, and HER2 expression of GC patients (P<0.05). GC patients with high plasma exosomal circLPAR1 expression had significantly longer prognostic survival time than those with low expression (P<0.05). According to univariate and multivariate Cox regression analyses, tissue differentiation degree (HR=1.415), TNM stage (HR=1.637), HER2 expression (HR=1.831), and low plasma exosomal circLPAR1 expression (HR=2.042) were risk factors for adverse prognosis in GC patients.

CONCLUSIONS

circLPAR1 expression is related to GC progression, and the detection of plasma exosomal circLPAR1 has promising clinical application value in assisting the diagnosis and prognosis evaluation of GC.

Upregulation of hsa_circ_0002003 promotes hepatocellular carcinoma progression

BACKGROUND

Circular RNAs (circRNAs), which are involved in various human malignancies, have emerged as promising biomarkers. The present study aimed to investigate unique expression profiles of circRNAs in hepatocellular carcinoma (HCC) and identify novel biomarkers associated with HCC development and progression.

METHODS

CircRNA expression profiles of HCC tissues were jointly analyzed to identify differentially expressed circRNAs. Overexpression plasmid and siRNA targeting candidate circRNAs were used in functional assays in vitro. CircRNA-miRNA interactions were predicted using miRNAs expressed in the miRNA-seq dataset GSE76903. To further screen downstream genes targeted by the miRNAs, survival analysis and qRT-PCR were conducted to evaluate their prognostic role in HCC and construct a ceRNA regulatory network.

RESULTS

Three significantly upregulated circRNAs, hsa_circ_0002003, hsa_circ_0002454, and hsa_circ_0001394, and one significantly downregulated circRNA, hsa_circ_0003239, were identified and validated by qRT-PCR. Our in vitro data indicated that upregulation of hsa_circ_0002003 accelerated cell growth and metastasis. Mechanistically, DTYMK, DAP3, and STMN1, which were targeted by hsa-miR-1343-3p, were significantly downregulated in HCC cells when hsa_circ_0002003 was silenced and were significantly correlated with poor prognosis in patients with HCC.

CONCLUSION

Hsa_circ_0002003 may play critical roles in HCC pathogenesis and serve as a potential prognostic biomarker for HCC. Targeting the hsa_circ_0002003/hsa-miR-1343-3p/STMN1 regulatory axis could be an effective therapeutic strategy in patients with HCC.

Gastric juice non-coding RNAs as potential biomarkers for gastric cancer

Gastric cancer (GC), being one of the most common malignant human tumors, occupies the second position in the structure of mortality in men and women. High rates of morbidity and mortality in this pathology determine its extremely high clinical and social significance. Diagnosis and timely treatment of precancerous pathology is the main way to reduce morbidity and mortality, and early detection of GC and its adequate treatment improve prognosis. The ability to accurately predict the development of GC and start treatment on time, as well as the ability to determine the stage of the disease if the diagnosis is confirmed - non-invasive biomarkers can become the key to solving these and many other problems of modern medicine. One of the promising biomarkers being studied are non-coding RNAs, namely, miсroRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). They are involved in a wide range of processes, including apoptosis, proliferation, differentiation, angiogenesis, which play a critical role in the development of GC oncogenesis. In addition, they are quite specific and stable due to their carriers (extracellular vesicles or Argonaute 2 protein) and can be detected in various human biological fluids, in particular gastric juice. Thus, miRNAs, lncRNAs, and circRNAs isolated from the gastric juice of GC patients are promising preventive, diagnostic and prognostic non-invasive biomarkers. This review article presents the characteristics of circulating or extracellular miRNAs, lncRNAs, and circRNAs in gastric juice, allowing their use in the GC preventive, diagnosis, prognosis and monitoring therapy.

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.

Circ_0003789 Facilitates Gastric Cancer Progression by Inducing the Epithelial-Mesenchymal Transition Through the Wnt/β-Catenin Signaling Pathway

Background: The role of circular RNAs in the pathogenesis of gastric cancer (GC) has been well documented by numerous studies. However, whether circ_0003789 plays a role during GC progression remains to be determined. Thus, this study investigated the biological functions of circ_0003789 during GC progression. Materials and Methods: Circ_0003789 expression was determined using quantitative real-time polymerase chain reaction in GC and matched para-carcinoma normal tissues. Functional experiments were performed to estimate changes in the proliferation, apoptosis, migration, and invasion of GC cells treated to silence circ_0003789. E-cadherin, vimentin, Wnt3a, and β-catenin expression was determined using immunofluorescence staining and Western blot assays. Xenograft tumor growth and Ki67 expression were also evaluated in vivo. Results: Circ_0003789 was upregulated in GC tissues and cells, and its upregulation positively correlated with poor tumor differentiation, distal metastasis, and advanced clinical stage. Silencing circ_0003789 inhibited GC cell proliferation, migration, invasion, and the epithelial-mesenchymal transition (EMT), both in vitro and in vivo. Mechanistically, the Wnt/β-catenin signaling pathway was repressed by circ_0003789 silencing. Conclusions: Circ_0003789 facilitates GC progression by inducing the EMT through the Wnt/β-catenin signaling pathway.

Long non-coding RNAs reveal new regulatory mechanisms controlling gene expression

A plethora of non-coding RNAs have been found in eukaryotes, notably with the advent of modern sequencing technologies to analyze the transcriptome. Apart from the well-known housekeeping RNA genes (such as the ribosomal RNA or the transfer RNA), many thousands of transcripts detected are not evidently linked to a protein-coding gene. These, so called non-coding RNAs, may code for crucial regulators of gene expression, the small si/miRNAs, for small peptides (translated under specific conditions) or may act as long RNA molecules (antisense, intronic or intergenic long non-coding RNAs or lncRNAs). The lncRNAs interact with members of multiple machineries involved in gene regulation. In this review, we discussed about how plant lncRNAs permitted to discover new regulatory mechanisms acting in epigenetic control, chromatin 3D structure and alternative splicing. These novel regulations diversified the expression patterns and protein variants of target protein-coding genes and are an important element of the response of plants to environmental stresses and their adaptation to changing conditions.

Circular RNA circFBXO7 attenuates non-small cell lung cancer tumorigenesis by sponging miR-296-3p to facilitate KLF15-mediated transcriptional activation of CDKN1A

BACKGROUND

Accumulating evidence indicates that circular RNAs (circRNAs) play important roles in various cancers. Hsa_circ_0008832 (circFBXO7) is a circRNA generated from the second exon of the human F-box only protein 7 (FBXO7). Mouse circFbxo7 is a circRNA generated from the second exon of mouse F-box only protein 7 (Fbxo7). The role of human circFBXO7 and mouse circFbxo7 in non-small cell lung cancer (NSCLC) has not been reported.

METHODS

The expression of circFBXO7 was measured by quantitative real-time PCR. Survival analysis was performed to explore the association between the expression of circFBXO7 and the prognosis of patients with NSCLC. Lung cancer cell lines were transfected with plasmids. Cell proliferation, cell cycle, and tumorigenesis were evaluated to assess the effects of circFBXO7. Fluorescence in situ hybridization assay was used to identify the location of circFBXO7 and circFbxo7 in human and mouse lung cancer cells. Luciferase reporter assay was conducted to confirm the relationship between circFBXO7 and microRNA.

RESULTS

In this study, we found that circFBXO7 was downregulated in NSCLC tissues and cell lines. NSCLC patients with high circFBXO7 expression had prolonged overall survival. Overexpression of circFBXO7 inhibited cell proliferation both in vitro and in vivo. Mechanistically, we demonstrated that circFBXO7 upregulated the expression of miR-296-3p target gene Krüppel-like factor 15 (KLF15) and KLF15 transactivated the expression of CDKN1A.

CONCLUSIONS

CircFBXO7 acts as a tumor suppressor by a novel circFBXO7/miR-296-3p/KLF15/CDKN1A axis, which may serve as a potential biomarker and therapeutic target for NSCLC.

Circular RNA 0001789 sponges miR-140-3p and regulates PAK2 to promote the progression of gastric cancer

BACKGROUND

Gastric cancer (GC) is the third-leading cause of cancer-associated mortalities globally. The deregulation of circular RNAs (circRNAs) and microRNAs (miRNAs or miRs) is widely implicated in the pathogenesis and progression of different cancer types.

METHODS

The expression profiling of circRNAs in GC is required to identify crucial circRNAs as biomarkers or therapeutic targets. In the present study, a published circRNA microarray dataset was used to identify differentially expressed circRNAs between GC tissues and normal gastric mucosa tissues. Reverse transcription-quantitative PCR was performed to validate the expression of circ_0001789. Fisher's exact test, receiver operating characteristic curve and Kaplan-Meier plots were employed to analyze the clinical significance of circ_0001789. The miRNA targets of circ_0001789 were predicted using an online database, and their functional interaction was further confirmed by RNA pull-down, RNA immunoprecipitation and dual luciferase reporter assays. Transwell assays were conducted to investigate the biological functions of circ_0001789, miR-140-3p and p21 activated kinase 2 (PAK2) in the migration and invasion of GC cells. A xenograft mouse model was established to validate the role of circ_0001789 in the tumorigenesis of GC cells.

RESULTS

circ_0001789 was identified as a highly expressed circRNA in GC tissues versus normal gastric mucosa tissues. Silencing circ_0001789 attenuated the malignancy of GC cells, and exosomal circ_0001789 was sufficient to regulate the malignant phenotype of GC cells. miR-140-3p was further identified as a downstream target of circ_0001789, which showed a negative correlation with circ_0001789 expression in GC tissues. Overexpression of miR-140-3p suppressed cell migration, invasion and epithelial-mesenchymal transition in GC cells. PAK2 was identified as the target of miR-140-3 to mediate the malignant phenotype of GC cells.

CONCLUSION

The present data suggested that the upregulation of circ_0001789 was associated with the progression of GC and with poor prognosis in patients with GC, and that miR-140-3p/PAK2 served as the downstream axis to mediate the oncogenic effect of circ_0001789.

MicroRNAs induced by Listeria monocytogenes and their role in cells

Listeria monocytogenes (Lm) causes abortions at high rates and threatens newborns' lives. Also, the elderly and immunocompromised individuals are particularly vulnerable neurologically. The bacterium exerts its pathogenesis intracellularly by manipulating cell organs. It manipulates nucleus elements, microRNAs (miRNAs), in order to increase survival and evade immunity. miRNAs are small non-coding RNAs that degrade gene expression post-transcriptionally. Any alteration to the expression of miRNAs affects various cascades in cells, especially immunity-related responses. Thus, utilizing miRNAs as a novel therapeutic agent not only restricts infection but enhances immunity reactions. This review provides an overview of miRNAs in listeriosis, their role in cells, and their prospects as therapy.

Gastric cancer detection by non-blood-based liquid biopsies: A systematic review looking into the last decade of research

Gastric cancer (GC) screening is arguable in most Western countries. Liquid biopsies are a great promise to answer the unmet need for less invasive diagnostic biomarkers in GC. Thus, we aimed at systematically reviewing the current knowledge on liquid biopsy-based biomarkers in GC screening. A systematic search on PubMed/MEDLINE and Scopus databases was performed on published articles reporting the use of non-blood specimen (saliva, gastric juice [GJ], urine and stool) on GC diagnosis. 3208 records were retrieved by June 2022. After removal of duplicate records, 2379 abstracts were screened, and 84 full texts included in this systematic review. More than 90% of studies were reported on Asian populations. Overall, 9 studies explored stool-, 12 saliva-, and 29 urine-derived biomarkers for GC detection. Additionally, 37 studies, representing the majority, analyzed GJ, focusing on nucleic acid molecules. Several miRNAs and lncRNA molecules have been associated with GC risk, particularly miR-21 (area under the curve [AUC] = 0.97, 95% CI: 0.94-1.00). Considering salivary biomarkers, the best described model in validation sets included the soybean agglutinin and Vicia villosa agglutinin lectins (AUC = 0.89, 95% CI: 0.80-0.99). Most studies in urine carried out metabolomic approaches, with two discriminatory models presenting AUC values superior to 0.97. This systematic review emphasizes the potential role of non-blood-based biomarkers, although further validation, particularly in Western countries, is mandatory, namely for non-invasive screening and/or monitoring, as well as the use of GJ as a tool to enhance upper gastrointestinal endoscopy accuracy.

Functional properties of circular RNAs and research progress in gastric cancer

Circular RNAs (circRNAs) are a class of closed circular non-coding RNAs widely exist in eukaryotes, with high stability and species conservation. A large number of studies have shown that circRNAs are abnormally expressed in various tumor tissues, and are abundant in plasma with long half-life and high specificity, which may be served as potential tumor biomarkers for early diagnosis, treatment and prognosis of malignant tumors. However, the role of circRNAs is still poorly understood in gastric cancer. This article reviews the research progress of circRNAs in gastric cancer in recent years so as to explore the relationship between circRNAs and the occurrence and the development of gastric cancer, and provide new ideas for the diagnosis and treatment of gastric cancer.

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.

Circular RNAs: Biomarkers of cancer

Circular RNAs (circRNAs) are a class of single-stranded closed RNAs that are produced by the back splicing of precursor mRNAs. The formation of circRNAs mainly involves intron-pairing-driven circularization, RNA-binding protein (RBP)-driven circularization, and lariat-driven circularization. The vast majority of circRNAs are found in the cytoplasm, and some intron-containing circRNAs are localized in the nucleus. CircRNAs have been found to function as microRNA (miRNA) sponges, interact with RBPs and translate proteins, and play an important regulatory role in the development and progression of cancer. CircRNAs exhibit tissue- and developmental stage-specific expression and are stable, with longer half-lives than linear RNAs. CircRNAs have great potential as biomarkers for cancer diagnosis and prognosis, which is highlighted by their detectability in tissues, especially in fluid biopsy samples such as plasma, saliva, and urine. Here, we review the current studies on the properties and functions of circRNAs and their clinical application value.

Identification of a functional circRNA-miRNA-mRNA regulatory network in infantile hemangioma by bioinformatics analysis

Several circRNA have been reported to serve critical roles in various biological processes of human body. The present study aimed to build a circRNA-based competing endogenous RNA (ceRNA) network and explore the regulatory mechanisms of circRNA in infantile hemangiomas (IH). Differentially expressed circRNA, miRNA, and mRNA were downloaded from the gene expression synthesis (GEO) microarray database (GSE98795, GSE69136, and GSE127487). Cancer-specific circRNA database (CSCD), miRDB and Targetscan were employed to predict the targets of RNA. A total of 855 DEcircRNAs, 69 differentially expressed miRNAs (DEmiRNAs), and 3233 differentially expressed mRNAs (DEmRNAs) appeared as genes that were aberrantly expressed in IH. The circRNA-miRNA-mRNA network was constructed based on 108 circRNAs, 7 miRNAs, 274 mRNAs in IH. Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis indicated hypoxia-inducible factors (HIF)-1 signaling pathway and Notch signaling pathway were significantly enriched in IH with being constructed a ceRNA regulatory network. Furthermore, protein-protein interaction (PPI) network and Cytoscape showed the top 10 hub genes that regulate angiogenesis, namely FBXW7, CBLB, HECW2, FBXO32, FBXL7, KLHL5, EP300, MAPK1, MEF2C, and PLCG1. Our findings provide a deeper understanding the circRNA-related ceRNA regulatory mechanism in IH. This study further perfected the circRNA-miRNA-mRNA regulatory network related to IH and explored the potential function of mRNA in this network. It provides more understanding for the circRNA-related ceRNA regulation mechanism in the pathogenesis of IH.

Transcriptome sequencing of hepatocellular carcinoma uncovers multiple types of dysregulated ncRNAs

Transcriptome profiling of hepatocellular carcinoma (HCC) by next-generation sequencing (NGS) technology has been broadly performed by previous studies, which facilitate our understanding of the molecular mechanisms of HCC formation, progression, and metastasis. However, few studies jointly analyze multiple types of noncoding RNAs (ncRNAs), including long noncoding RNAs (lncRNAs), circular RNAs (circRNAs), and micro-RNAs (miRNAs), and further uncover their implications in HCC. In this study, we observed that the circRNA cZRANB1 and lncRNA DUXAP10 were not only significantly upregulated in tumor tissues, but also higher expressed in blood exosomes of HCC as compared with healthy donors. From the analysis of subclass-associated dysregulated ncRNAs, we observed that DLX6-AS1, an antisense RNA of DLX6, and the sense gene DLX6 were highly expressed in S1, a subclass with a more invasive/disseminative phenotype. High correlation between DLX6-AS1 and DLX6 suggested that DLX6-AS1 may function via promoting the transcription of DLX6. Integrative analysis uncovers circRNA–miRNA, lncRNA–miRNA, and competing endogenous RNA networks (ceRNAs). Specifically, cZRANB1, LINC00501, CTD-2008L17.2, and SLC7A11-AS1 may function as ceRNAs that regulate mRNAs by competing the shared miRNAs. Further prognostic analysis demonstrated that the dysregulated ncRNAs had the potential to predict HCC patients’ overall survival. In summary, we identified some novel circRNAs and miRNAs, and dysregulated ncRNAs that could participate in HCC tumorigenesis and progression by inducing transcription of their neighboring genes, increasing their derived miRNAs, or acting as miRNA sponges. Moreover, our systematic analysis provides not only rich data resources for related researchers, but also new insights into the molecular basis of how different ncRNAs coordinately or antagonistically participate in the pathogenesis process of diseases.

Melatonin may suppress lung adenocarcinoma progression via regulation of the circular noncoding RNA hsa_circ_0017109/miR-135b-3p/TOX3 axis

Melatonin is a hormone synthesized in the pineal gland and has widespread physiological and pharmacological functions. Moreover, it can activate protective receptor-dependent processes. These processes can prevent tissue carcinogenesis and inhibit malignant tumor progression and metastasis. Therefore, we investigated the regulatory effects of melatonin on dysregulated circular RNAs in human lung adenocarcinoma (LUAD) cells. In this study, we treated LUAD cells with melatonin and measured the expression of hsa_circ_0017109, miR-135b-3p, and TOX3 by quantitative reverse transcription polymerase chain reaction. Colony formation and cell counting kit-8 assays were used to determine cell proliferation. The wound-healing assay and Transwell experiment were carried out to evaluate the migration potential and invasive capacity of LUAD cells. Also, cell apoptosis was detected using a cell apoptosis kit, and protein production was identified by Western blot. It was suggested that melatonin could inhibit LUAD progression in vivo and in vitro, and the role of TOX3 in this process was explored. Additionally, hsa_circ_0017109 was found to sponge miR-135b-3p, a downstream factor of circ_0017109, which was demonstrated to target TOX3 in LUAD cells and could promote the Hippo pathway and epithelial-mesenchymal transition pathway. To summarize, we demonstrated that melatonin decreases the expression of circ_0017109 and suppresses the non-small-cell lung cancer cell migration, invasion, and proliferation through decreasing TOX3 expression via direct activation of miR-135b-3p.

Role of circular RNAs in disease progression and diagnosis of cancers: An overview of recent advanced insights

Tumor microenvironment (TME) is a crucial regulator of tumor progression and cells in the TME release a number of molecules that are responsible for anaplasticity, invasion, metastasis of tumor, establishing stem cell niches, up-regulation and down-regulation of various pathways in cancer cells, interfering with immune surveillance and immune escape. Moreover, they can serve as diagnostic markers, and determine effective therapies. Among them, CircRNAs have gained special attention due to their involvement in mutated pathways in cancers. By functioning as a molecular sponge for miRNAs, binding with proteins, and directing selective splicing. CircRNAs modify the immunological environment of cancers to promote their growth. Besides of critical role in tumor growth, circRNAs are emerging as potential candidates as biomarkers for diagnosis cancer therapy. Also, circRNAs vaccination even offers a novel approach to tumor immunotherapy. Over the recent years, studies are advocating that circRNAs have tissue specific tumor specific expression patterns, which indicates their potential clinical utility. Especially, circRNAs have emerged as potential predictive and prognostic biomarkers. Although, there has been significant progress in deciphering the role of circRNA in cancers, literature lacks comprehensive overview on this topic. Keeping in view of these significant discoveries, this review systematically discusses circRNA and their role in the tumor in different dimensions.

A new biomarker for the early diagnosis of gastric cancer: gastric juice- and serum-derived SNCG

Aim: To explore the possibility of gastric juice (GJ)- and serum-derived SNCG as a potential biomarker for the early diagnosis of gastric cancer (GC). Materials & methods: GJ and serum samples were collected from 87 patients with GC, 38 patients with gastric precancerous lesions and 44 healthy volunteers. The levels of SNCG in GJ and serum samples were detected by ELISA. Results: The levels of SNCG in GJ and serum were significantly higher in the GC group when compared with the GPL group or the control group. The expression of SNCG in GJ and serum was associated with tumor node metastasis stage, lymph node metastasis, tumor size and drinking, and it is important for the diagnosis and prognosis of GC (p < 0.05). Conclusion: The findings highlight the significance of SNCG in GC diagnosis and prognosis and implicate SNCG as a promising candidate for GC treatment.

Hsa_circ_0001020 Serves as a Potential Biomarker for Gastric Cancer Screening and Prognosis

Circular RNAs (circRNAs) are an intriguing class of RNAs with covalently closed-loop structures. With characteristics of high stability and disease-specific expression, circRNAs are emerging as ideal targets for cancer therapy. However, the screening utility and clinical value of circRNAs in gastric cancer (GC) remain largely elusive. We detected levels of hsa_circ_0001020 in cell lines and tissue and plasma samples and investigated its clinicopathological correlations. Kaplan-Meier survival curves and regression analyses were used to analyze its prognostic value. Receiver operating characteristic curves and biomarker combinations were examined to verify its screening value. Bioinformatics analysis was also performed to predict potential biological functions. Our tests found that hsa_circ_0001020 was significantly upregulated in GC cell lines, GC tissue samples, and even in plasma. High hsa_circ_0001020 expression levels in GC tissues were significantly associated with distal metastasis and blood carbohydrate antigen 19-9 (CA19-9). GC patients with high hsa_circ_0001020 had a lower overall survival and disease-free survival time than the low levels. Regression analysis suggested that the level of hsa_circ_0001020 expression was an independent prognostic factor for survival time. As a biomarker for GC, hsa_circ_0001020 showed a superior AUC, sensitivity, and specificity than carcinoembryonic antigen and CA19-9, and was suitable for combination with clinical tumor biomarkers. Bioinformatics analysis provided valuable clues for the possible oncogenic pathways of GC, such as the FoxO and p53 signaling pathways. In conclusion, our study found that hsa_circ_0001020 in GC could be a reliable biomarker to screen for GC and predict prognosis.

The tumor suppressor function of hsa_circ_0006282 in gastric cancer through PTEN/AKT pathway

BACKGROUND

Circular RNAs (circRNAs) play key roles in carcinogenesis. However, the roles of circRNAs in gastric cancer are largely unknown. The aim of this study is to study the possible roles of hsa_circ_0006282 in gastric cancer.

METHODS

The hsa_circ_0006282 levels in gastric cancer cell lines, 85 gastritis tissues, and 103 paired gastric cancer tissues and non-tumor tissues were first detected by quantitative real-time reverse transcription-polymerase chain reaction. RNA interference and hsa_circ_0006282 expression plasmid were further used to manipulate hsa_circ_0006282 expression in gastric cancer. Finally, biological effects of hsa_circ_0006282 were analyzed by real-time cell analysis, flow cytometry, Transwell, cell cloning assay and Western blot analysis.

RESULTS

Hsa_circ_0006282 was down expressed in gastric cancer cells, gastritis tissues, and gastric cancer tissues. The abilities of cell proliferation, cell migration and resistance to apoptosis were enhanced after hsa_circ_0006282 was downregulated, while overexpression of hsa_circ_0006282 got opposite results. Besides, Western blot showed that the levels of protein kinase B (AKT) and cyclin-dependent kinase 2 (CDK2) were significantly increased and decreased after knockdown and up-regulation of hsa_circ_0006282, respectively, while phosphatase and tensin homolog deleted on chromosome ten (PTEN) was significantly opposite regulated. Finally, hsa_circ_0006282 promoted the expression of PTEN by sponging hsa-miR-136-5p.

CONCLUSION

By regulating the PTEN/AKT signaling pathway through competitively binding with hsa-miR-136-5p, hsa_circ_0006282 suppresses the growth of gastric cancer.

Review: RNA-based diagnostic markers discovery and therapeutic targets development in cancer

The present review aimed to outline different types of RNAs in cancer diagnostics and treatment, and to provide novel insights into their clinical applications. RNAs, including mRNA, long non-coding (lnc)RNA, circular (circ)RNA and micro (mi)RNA, are now increasingly utilized in the diagnosis and treatment of various cancers. Each aforementioned type of RNA possess their own unique characteristics and could be aberrantly expressed as diagnostic markers or therapeutic targets in different cancers. In addition to mRNAs, which have become a promising alternative in cancer diagnostics and therapy, the uses of lncRNA, circRNA and miRNA in predictive tumor diagnostics and therapy has rapidly increased in recent years. In the present review, the mechanisms of mRNA, lncRNA, circRNA and miRNA in regulating and participating in the development of different cancers were determined, and their potential capacity in cancer diagnostics and therapy were investigated. In addition, the present review analyzed the assoaciations between different RNAs and their subsequent potential in cancer prediction and treatment.

The regulation of hsacirc_004413 promotes proliferation and drug resistance of gastric cancer cells by acting as a competing endogenous RNA for miR-145-5p

Background

Whether circRAN, which acts as a microRNA sponge, plays a role in 5-fluorouracil (5-Fu) resistant gastric cancer has not been reported. In this study, a 5-Fu resistant cell line with an IC50 of 16.59 µM was constructed.

Methods

Using comparative analysis of circRNA in the transcriptomics of resistant and sensitive strains, 31 differentially expressed circRNAs were detected, and the microRNA interacting with them was predicted.

Results

Hsacirc_004413 was selected for verification in drug resistant and sensitive cells. By interfering with hsacirc_004413 using antisense RNA, the sensitivity of drug resistant cells to 5-Fu was significantly promoted, and the apoptosis and necrosis of the cells were significantly increased. In sensitive cells, inhibition by inhibitors enhanced the resistance of cells to 5-Fu. We hypothesize that hsacirc_004413 makes gastric cancer cells resistant to 5-Fu mainly through adsorption of miR-145-5p.

Biological and clinical implications of hsa_circ_0086720 in gastric cancer and its clinical application

Background

Circular RNAs (circRNAs) are thought to be vital participants in carcinogenesis and have the characteristics of being stable, specific, and well conserved. However, their clinical significance and application value in gastric cancer (GC) are still poorly understood. Hsa_circ_0086720 was found to be a dysregulated circRNA in GC by microarray screening and was further explored for its clinical significance and application.

Methods

Hsa_circ_0086720 was detected in GC cell lines, tissues, and plasma, and the clinicopathological correlations were investigated. The existence, stability, origin, and change in the plasma hsa_circ_0086720 level were verified in early GC patients. Moreover, receiver operating characteristic and Kaplan–Meier survival curves were constructed to analyze the diagnostic and prognostic values, and bioinformatics analysis was used to identify the potential functions. Finally, risk factors and nomogram predicting were established.

Results

Hsa_circ_0086720 was found to be downregulated in gastric carcinogenesis, and tissue hsa_circ_0086720 was negatively associated with perineural invasion, Borrmann type, disease‐free survival, and overall survival. Hsa_circ_0086720 was stable in circulating plasma and was actively secreted by cells in gastric carcinogenesis. As a biomarker for early GC screening, plasma hsa_circ_0086720 had good sensitivity and specificity, and its stability met the clinical application requirements. Bioinformatics analysis suggested that dysregulated hsa_circ_0086720 has important functions in gastric carcinogenesis. Univariate Cox regression analysis identified factors associated with overall survival time and disease‐free survival time. The nomograms showed good accuracy of predicting survival time.

Conclusion

Hsa_circ_0086720 is a novel biomarker for screening early GC and predicting the prognosis of advanced‐stage patients.

Extracellular Circular RNAs Act as Novel First Messengers Mediating Cell Cross-Talk in Ischemic Cardiac Injury and Myocardial Remodeling

Myocardial infarction (MI) causes most of the mortality worldwide. Coronary obstruction-caused myocardial ischemic injury leads to permanent loss of the myocardium. Subsequent compensatory myocardial remodeling and heart failure would result in arrhythmia and even sudden death. The molecular mechanisms of these pathological processes remain to be thoroughly revealed. Circular RNAs (circRNAs) are special types of non-coding RNAs which can durably regulate gene expression and modulate cell fate. They had been reported to mediate ischemic myocardial injury and myocardial remodeling. circRNAs can be loaded into extracellular vesicles and released into extracellular space. More recently, it was uncovered that the extracellular circRNAs can regulate intercellular communications, similar to "first messengers." The cross-talk mediated by extracellular circRNAs had been demonstrated to play important roles in pathological processes. Here, we would like to review the modulation of extracellular circRNAs in ischemic myocardial injury and myocardial remodeling. We believe the extracellular circRNAs can bring new strategies of MI treatment.

Icaritin-elevated circ_0000190 suppresses the malignant progression of multiple myeloma by targeting miR-301a

Icaritin has potential anticancer effects on various cancers, including multiple myeloma (MM). Recent studies claim that Icaritin can regulate the expression of noncoding RNAs (ncRNAs) in cancer development. This study aimed to investigate the role of circular RNA_0000190 (circ_0000190) and functional mechanism in Icaritin-treated MM. The expression of circ_0000190 and miR-301a was detected by quantitative real-time polymerase chain reaction. Cell cycle, apoptosis, migration, and invasion were investigated using flow cytometry assay, and transwell assay, respectively. The expression of BAX, BCL2, MMP2, and CCND1 was detected by western blot. The predicted target relationship between circ_0000190 and miR-301a was validated by dual-luciferase reporter assay and RNA immunoprecipitation assay. The activation of JAK1/STAT3 pathway was examined using western blot. Circ_0000190 was strikingly downregulated in MM specimens and cell lines, and Icaritin promoted the expression of circ_0000190. In function, circ_0000190 overexpression promoted MM cell cycle arrest and apoptosis but restrained the ability of migration and invasion. Icaritin blocked the development of MM by increasing circ_0000190 expression. MiR-301a was identified as a target of circ_0000190, and miR-301a reintroduction largely abolished the effects of circ_0000190 overexpression. The activation of JAK1/STAT3 pathway was promoted by miR-301a restoration. Icaritin played anticancer effects in MM partly by enhancing the expression of circ_0000190 and regulating the circ_0000190/miR-301a pathway. This study enhanced the understanding of the mechanism of Icaritin associated with circRNAs in MM.

Circ_0003159 upregulates LIFR expression through competitively binding to miR-221-3p/miR-222-3p to block gastric cancer development

Gastric cancer (GC) remains a major cause of cancer-related deaths. Increasing studies suggest that cancer development is accompanied by the deregulation of circular RNAs. We investigated the function of circ_0003159 in GC. The expression levels of circ_0003159, miR-221-3p/miR-222-3p and leukemia inhibitory factor receptor (LIFR) mRNA were measured by real-time quantitative polymerase chain reaction. Cell colony formation ability was assessed by colony formation assay, and cell viability was assessed by cell counting kit-8 assay. Cell apoptosis was assessed by flow cytometry assay and caspase3 activity. Cell migration and invasion were assessed by transwell assay. Glycolysis energy metabolism was assessed by 5'-triphosphate production, glucose uptake and lactate production. The protein levels of related marker proteins and LIFR were detected by western blot. The relationship between circ_0003159 and miR-221-3p/miR-222-3p, or LIFR and miR-221-3p/miR-222-3p was obtained from bioinformatics tools and verified by dual-luciferase reporter assay. A cancer tumorogenicity xenograft experiment in nude mice was conducted to determine the role of circ_0003159 in tumor growth by AGS cells. Our results showed that circ_0003159 expression was decreased in GC tissues and cells. Circ_0003159 overexpression sequestered GC cell viability, migration, invasion and glycolysis and induced cell apoptosis. MiR-221-3p and miR-222-3p were targets of circ_0003159, and the inhibition of miR-221-3p and miR-222-3p also blocked GC cell viability, migration, invasion and glycolysis and promoted cell apoptosis. LIFR was a common target of miR-221-3p and miR-222-3p. Interestingly, LIFR knockdown reversed the effects of circ_0003159 overexpression on GC cell behaviors. Circ_0003159 increased the expression level of LIFR by targeting miR-221-3p and miR-222-3p. The tumorigenicity assay showed that circ_0003159 overexpression inhibited tumor growth in vivo. In conclusion, circ_0003159 inhibited GC development in vitro and in vivo by enriching the level of LIFR via direct binding to miR-221-3p/miR-222-3p.

lncRNA GAS8-AS1 regulates cancer cell proliferation and predicts poor survival of patients with gastric cancer

Long non-coding (lnc)RNAs have been recognized as important regulators in gastric cancer. lncRNA GAS8-AS1 is considered a tumor suppressor in multiple types of cancer, such as papillary thyroid carcinoma, ovarian cancer and colorectal cancer. However, the specific role of GAS8-AS1 in gastric cancer remains to be fully elucidated. The aim of the present study was to investigate the role of GAS8-AS1 in gastric cancer and its potential underlying mechanisms of action. The expression levels of GAS8-AS1, microRNA (miR)-21-3p, PTEN and pyruvate dehydrogenase (E1) alpha subunit gene (PDHA1) in gastric cancer and non-cancerous tissues, as well as in gastric cancer cell lines, were detected using reverse transcription-quantitative PCR. Cell proliferation was detected by using a Cell Counting Kit-8 assay. Cell migration and invasion were detected using a Transwell assay. Results of the present study demonstrated that the expression levels of GAS8-AS1 in gastric cancer tissues were significantly decreased, whereas its expression did not differ among cancer tissues at different clinical stages. Low expression levels of GAS8-AS1 predicted poor 5-year survival rates for 70 patients with gastric adenocarcinoma from the Affiliated Hospital of Xuzhou Medical University (Xuzhou, China) during patient follow-up. In addition, the expression levels of miR-21-3p were markedly increased in cancer tissues, and miR-21-3p expression was negatively associated with the expression of GAS8-AS1. The direct interaction between GAS8-AS1 and miR-21-3p was predicted using the starBase database and was confirmed by using an RNA pull-down assay. In gastric cell lines, the overexpression of GAS8-AS1 reduced the expression levels of mature miR-21-3p but did not affect the expression of miR-21-3p precursor, while the overexpression of miR-21-3p did not, in turn, affect the expression of GAS8-AS1. In addition, the overexpression of GAS8-AS1 inhibited cancer cell proliferation, while the overexpression of miR-21-3p promoted cancer cell proliferation and attenuated the effects of GAS8-AS1. Overexpression of miR-21-3p promoted cancer cell migration and invasion, whereas overexpression of GAS8-AS1 did not affect cell migration or invasion. In summary, results of the present study have demonstrated that GAS8-AS1 acts as a tumor suppressor in gastric cancer, and it may inhibit cancer cell proliferation by downregulating miR-21-3p.

CircRNAs as Potential Blood Biomarkers and Key Elements in Regulatory Networks in Gastric Cancer

Gastric cancer (GC) is the fifth most common type of cancer and the third leading cause of cancer death in the world. It is a disease that encompasses a variety of molecular alterations, including in non-coding RNAs such as circular RNAs (circRNAs). In the present study, we investigated hsa_circ_0000211, hsa_circ_0000284, hsa_circ_0000524, hsa_circ_0001136 and hsa_circ_0004771 expression profiles using RT-qPCR in 71 gastric tissue samples from GC patients (tumor and tumor-adjacent samples) and volunteers without cancer. In order to investigate the suitability of circRNAs as minimally invasive biomarkers, we also evaluated their expression profile through RT-qPCR in peripheral blood samples from patients with and without GC (n = 41). We also investigated the predicted interactions between circRNA-miRNA-mRNA and circRNA-RBP using the KEGG and Reactome databases. Overall, our results showed that hsa_circ_0000211, hsa_circ_0000284 and hsa_circ_0004771 presented equivalent expression profiles when analyzed by different methods (RNA-Seq and RT-qPCR) and different types of samples (tissue and blood). Further, functional enrichment results identified important signaling pathways related to GC. Thus, our data support the consideration of circRNAs as new, minimally invasive biomarkers capable of aiding in the diagnosis of GC and with great potential to be applied in clinical practice.

Impact of circ-0000221 in the Pathogenesis of Hepatocellular via Modulation of miR-661-PTPN11 mRNA Axis

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death in Egypt. A deep understanding of the molecular events occurring in HCC can facilitate the development of novel diagnostic and/or therapeutic approaches. In the present study, we describe a novel axis of hsa-circ-0000221–miR-661–PTPN11 mRNA proposed by in silico and in vitro analysis and its role in HCC pathogenesis. We observe a reduction in the expression levels of hsa-circ-0000221 and PTPN11 mRNA in HCC patients’ sera tested compared with control subjects. The reduction occurs with a concomitant increase in the expression of miR-661. Furthermore, the introduction of exogenous hsa-circ-0000221 into Hep-G2 or SNU449 cell lines results in detectable decrease in cellular viability and an increase in apoptotic manifestations that is associated with G1 accumulation and CCDN1 overexpression. Altogether, these findings indicate the tumor-suppressive role of hsa-circ-0000221 in HCC, which acts through miR-661 inhibition, along with a subsequent PTPN11 mRNA increase, where PTPN11 is known to inhibit cell proliferation in many forms of cancer. Our study encourages further investigation of the role of circRNAs in cancer and their potential use as molecular biomarkers.

hsa_circ_0001275 Is One of a Number of circRNAs Dysregulated in Enzalutamide Resistant Prostate Cancer and Confers Enzalutamide Resistance In Vitro

Simple Summary

Although newer generations of androgen deprivation therapy such as enzalutamide are providing hope, it is clinically challenging to deliver effective therapy to individuals with metastatic castrate-resistant prostate cancer. Between 20–40% of patients have intrinsic resistance to therapy and all patients will ultimately experience disease progression due to acquired resistance, which is a significant clinical dilemma. The aim of our study was to evaluate the role of circular RNAs (circRNAs) in enzalutamide-resistant prostate cancer as part of the effort to identify useful biomarkers for patient selection and potential new therapeutic targets. We confirmed that hsa_circ_0001275 was highly upregulated in an enzalutamide resistant cell line and demonstrated that its overexpression resulted in increased enzalutamide resistance. Our data showed that hsa_circ_0001275 was not expressed abundantly in patient plasma samples, however, a trend of expression was evident which paralleled disease activity indicating a possible association with enzalutamide resistance. Overall, we have provided evidence that hsa_circ_0001275 promotes enzalutamide resistance and thus may serve as a potential therapeutic target.

Abstract

Background: Enzalutamide is part of the treatment regimen for metastatic castration-resistant prostate cancer (MCRPC). However, both intrinsic and acquired resistance to the drug remain substantial clinical quandaries. circRNAs, a novel type of non-coding RNA, have been identified in a number of cancers including prostate cancer and have been associated with cancer development and progression. circRNAs have shown great potential as clinically useful blood-based ‘liquid biopsies’ and as therapeutic targets in prostate cancer. The aim of this study was to examine the role of circRNA transcripts in enzalutamide-resistant prostate cancer cells and assess their utility as biomarkers. Methods: An isogenic cell line model of enzalutamide resistance was subjected to circRNA microarray profiling. Several differentially expressed circRNAs, along with their putative parental genes were validated using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). circRNAs of interest were stably overexpressed in the control cell line and drug sensitivity was assessed using an ELISA-based proliferation assay. The candidate circRNA, hsa_circ_0001275, was measured in patient plasma samples using RT-droplet digital PCR (RT-ddPCR). Results: hsa_circ_0001275 and its parental gene, PLCL2, were significantly up-regulated in strongly resistant clones vs. control (p < 0.05). Overexpression of hsa_circ_0001275 in the control cell line resulted in increased resistance to enzalutamide (p < 0.05). While RT-ddPCR analysis of hsa_circ_0001275 expression in plasma samples of 44 clinical trial participants showed a trend that mirrored the stages of disease activity (as defined by PSA level), the association did not reach statistical significance. Conclusions: Our data suggest that increased levels of hsa_circ_0001275 contribute to enzalutamide resistance. hsa_circ_0001275 plasma expression showed a trend that mirrors the PSA level at specific disease time points, indicating that circRNAs mirror disease recurrence and burden and may be associated with enzalutamide resistance.

Evaluation of plasma circ_0006282 as a novel diagnostic biomarker in colorectal cancer

Background

Nowadays, non‐invasive and rapid detection of cancers through molecular biomarkers has received much attention. Therefore, this study investigated the non‐invasive and rapid diagnosis of colorectal cancer through one of the newest biomarkers (circular RNA).

Methods

For this purpose, we collected tumoral, adjacent normal tissue, and plasma samples from 100 colorectal cancer (CRC) patients, 25 postoperative CRC patients, 28 colitis patients, and 108 healthy donors. First Illumina high‐throughput (Hi Seq 2000) sequencing was performed to identify known and novel differentially expressed circRNAs in the cancerous and adjacent normal tissues (n = 3). We used quantitative real‐time fluorescent polymerase chain reaction (qRT‐PCR) to detect the expression level of hsa_circ_0006282 among the different samples. Moreover, inter‐ and intra‐assays were performed to evaluate the potential of hsa_circ_0006282 as being a biomarker. The receiver operating characteristic curve (ROC) was drawn to appraise its diagnostic efficacy, and the sensitivity of this circ RNA was evaluated.

Results

Based on RNA‐sequencing results circ_0006282, cirs7, circ‐0001313, circ_0055625, circ_000984, circ_0055625, circ_0001178, circ_0071589, circ‐001569 were upregulated, and circ‐ITGA7, circ‐CDYL, circITCH, circ_0026344, circ_0000038, circ_0002220, circ_0067480, circIGHV3‐20‐1, circ_104916, circ_0009361 were downregulated circRNA. The hsa_circ_0006282 was the highest upregulated differentially expressed circRNA. Expression evaluation of this circRNA on different samples showed upregulation in CRC tissues (p < 0.0001) and plasma samples of CRC patients in comparison to healthy controls (p < 0.0001), while the area under the curve (AUC) was 0.831 (95% CI: 0.779–0.883). Expression of hsa_circ_0006282 in CRC patients decreased to normal after surgery (p < 0.0001). Our results showed high specificity and sensitivity of CRC detection when hsa_circ_0006282, carcinoembryonic antigen (CEA), and carbohydrate antigen199 (CA199) are combined.

Conclusion

Plasma hsa_circ_0006282 can be used as a novel diagnostic and dynamic monitoring biomarker in CRC patients.

The role of non-coding RNAs in chemotherapy for gastrointestinal cancers

Gastrointestinal (GI) cancers, including colorectal, gastric, hepatic, esophageal, and pancreatic tumors, are responsible for large numbers of deaths around the world. Chemotherapy is the most common approach used to treat advanced GI cancer. However, chemoresistance has emerged as a critical challenge that prevents successful tumor elimination, leading to metastasis and recurrence. Chemoresistance mechanisms are complex, and many factors and pathways are involved. Among these factors, non-coding RNAs (ncRNAs) are critical regulators of GI tumor development and subsequently can induce resistance to chemotherapy. This occurs because ncRNAs can target multiple signaling pathways, affect downstream genes, and modulate proliferation, apoptosis, tumor cell migration, and autophagy. ncRNAs can also induce cancer stem cell features and affect the epithelial-mesenchymal transition. Thus, ncRNAs could possibly act as new targets in chemotherapy combinations to treat GI cancer and to predict treatment response.

The circular RNA hsa_circ_000780 as a potential molecular diagnostic target for gastric cancer

Background

The present study aimed to identify a specific circular RNA (circRNA) for early diagnosis of gastric cancer (GC).

Methods

Totally 82 patients with GC, 30 with chronic nonatrophic gastritis and 30 with chronic atrophic gastritis were included in this study. Four of the 82 GC patients were selected for screening. Total RNA from malignant and adjacent tissue samples was extracted, and circRNAs in four patients were screened. According to the screening results, the eight most upregulated and downregulated circRNAs with a statistically significant association with GC were identified by real-time fluorescent quantitative polymerase chain reaction (PCR). Then, the most regulated circRNA was selected for further sensitivity and specificity assessments. CircRNA expression was examined by quantitative reverse transcriptase PCR in 78 GC (21 and 57 early and advanced GC, respectively) and adjacent tissue samples, as well as in gastric fluid samples from 30 patients with chronic nonatrophic gastritis, 30 with chronic atrophic gastritis, and 78 GC.

Results

A total of 445 circRNAs, including 69 upregulated and 376 downregulated circRNAs, showed significantly altered expression in GC tissue samples. Hsa_circ_000780 was significantly downregulated in 80.77% of GC tissue samples, with levels in GC tissue samples correlating with tumor size, tumor stage, T stage, venous invasion, carcinoembryonic antigen amounts, and carbohydrate antigen 19–9 levels. Strikingly, this circRNA was found in the gastric fluid of patients with early and advanced GC.

Conclusions

The present study uncovered a new circRNA expression profile in human GC, with hsa_circ_000780 significantly downregulated in GC tissue and gastric fluid specimens. These findings indicate that hsa_circ_000780 should be considered a novel biomarker for early GC screening.

Circ-PTPDC1 promotes the Progression of Gastric Cancer through Sponging Mir-139-3p by Regulating ELK1 and Functions as a Prognostic Biomarker

Circular RNAs (circRNAs) is a novel class of non-coding RNAs resulting from the non-canonical splicing of linear pre-mRNAs. However, the role of circRNAs in gastric cancer (GC) remains indistinct. This study aims to explore their potential modulation in GC and its prognostic value. We first screen for circRNA expression patterns in GC through GC and adjacent noncancerous tissues by microarray. Based on the bioinformatics analysis of the microarray data, we screened out a novel circRNA, circ-PTPDC1. Then we demonstrated that circ-PTPDC1 was up-regulated in GC cells, tissues, and serum. Its overexpression was positively correlated with age, invasion depth, advanced clinical stages, and worse survival in patients with GC. We further revealed that circ-PTPDC1 promotes the proliferation, migration, and invasion of GC cell lines via sponging miR-139-3p by regulating ELK1. Importantly, we identified that circ-PTPDC1 promotes tumor upgrowth and metabasis in vivo. Additionally, we established its prognostic prediction model based on the follow-up data of the patients. Our study revealed a novel regulatory mechanism and a comprehensive landscape of circ-PTPDC1 in GC, suggesting that circ-PTPDC1 has the potential to be a biomarker for early detection and prognostic prediction of GC.

Hsa_circ_0003195 as a biomarker for diagnosis and prognosis of gastric cancer

PURPOSE

Recent studies have shown that circular RNAs (circRNAs) are closely related to the occurrence and development of gastric cancer. In this paper, we analyzed the value of hsa_circ_0003195 in diagnosis and prognosis of gastric cancer.

METHODS

Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to determine the level of hsa_circ_0003195 in 100 paired gastric cancer tissues and paracancerous tissues, 74 paired fasting plasma from gastric cancer patients before and 10 days after operation, and 74 fasting plasmas from healthy controls. A receiver operating characteristic (ROC) curve was generated to evaluate the diagnostic value. The survival analysis and Cox proportional-hazards model were used to evaluate the efficiency of hsa_circ_0003195 in predicting overall survival (OS) in patients with gastric cancer.

RESULTS

The expression of hsa_circ_0003195 was down-regulated in gastric cancer tissues and plasma from patients with gastric cancer. The expression level of hsa_circ_0003195 was correlated with differentiation, TNM stages, lymphatic metastasis, and distal metastasis. The area under the ROC curve (AUC) of tissue and plasma hsa_circ_0003195 was 0.684 and 0.695, respectively. The plasma hsa_circ_0003195 can be used as predictors of survival of patients with gastric cancer.

CONCLUSION

Hsa_circ_0003195 may be a new diagnostic and prognostic marker of gastric cancer.

The Value of Circulating Circular RNA in Cancer Diagnosis, Monitoring, Prognosis, and Guiding Treatment

Liquid biopsy includes non-invasive analysis of circulating tumor-derived substances. It is a novel, innovative cancer screening tool that overcomes the limitations of current invasive tissue examinations in precision oncology. Circular RNA (circRNA) is a recent, novel, and attractive liquid biomarker showing stability, abundance, and high specificity in various diseases, especially in human cancers. This review focused on the emerging potential of human circRNA in body fluids as the liquid biopsy biomarkers for cancers and the methods used to detect the circRNA expression and summarized the construction of circRNA biomarkers in body fluids for treating human cancers and their limitations before they become part of routine clinical medicine. Furthermore, the future opportunities and challenges of translating circRNAs in liquid biopsy into clinical practices were explored.

CircRNAs: Insights into Gastric Cancer

Background

Gastric cancer (GC) is recorded as the fifth most common cancer globally. The classic resemblance of early symptoms of chronic gastritis including nausea, dysphagia, and dyspepsia with GC is the current challenge limiting the early diagnosis of GC. The current diagnostic procedures of GC are limited due to their invasive nature. This directs the research question toward alternative approaches, specifically at the molecular level. Recent advances in molecular regulation of cancer suggest the prominence of circular RNAs (circRNAs) in the multistep process of tumourigenesis.

Summary

CircRNAs are a class of non-coding RNAs, abundant in eukaryotes, with key roles in regulating genes and miRNAs as well as the alteration of processes involved in pathological conditions. Research studies have demonstrated the participation of circRNAs in the initiation and progression of tumours. This review provides a comprehensive insight into the potential of circRNAs as disease biomarkers for the early detection and treatment of GC.

Key Messages

This study is an amalgamation of the implications and future prospects of circRNAs for the detection and potential treatment of GC.

Circ_0027599 elevates RUNX1 expression via sponging miR-21-5p on gastric cancer progression

BACKGROUND

Increasing evidence has shown that circular RNAs (circRNAs) serve as vital regulators in tumour progression. In this study, we focused on the functions of circ_0027599 in gastric cancer (GC) progression.

METHODS

The levels of circ_0027599, runt-related transcription factor 1 (RUNX1) mRNA and microRNA-21-5p (miR-21-5p) were detected by quantitative real-time polymerase chain reaction (qRT-PCR) assay. The protein levels of RUNX1, E-Cadherin, vimentin and N-Cadherin were measured by Western blot assay. Cell viability, colony formation, metastasis and cell cycle process were evaluated by Cell Counting Kit-8 (CCK-8) assay, colony formation assay, transwell assay and flow cytometry analysis, respectively. The interaction between circ_0027599 and miR-21-5p and the interaction between miR-21-5p and RUNX1 were verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. The role of circ_0027599 in tumour growth in vivo was investigated by murine xenograft model assay.

RESULTS

Circ_0027599 and RUNX1 were downregulated in GC tissues and cells. Circ_0027599 level was associated with the overall survival of GC patients. Circ_0027599 or RUNX1 overexpression inhibited GC cell viability, colony formation, migration, invasion and cell cycle process in vitro. For mechanism analysis, circ_0027599 positively regulated RUNX1 expression via functioning as the sponge for miR-21-5p. RUNX1 inhibition reversed circ_0027599 overexpression mediated malignant behaviours of GC cells. Moreover, circ_0027599 overexpression repressed tumour growth in vivo.

CONCLUSION

Circ_0027599 overexpression repressed GC progression via modulation of miR-21-5p/RUNX1 axis, which might illumine a novel therapeutic target for GC.

The role of GTPase-activating protein ARHGAP26 in human cancers

Rho GTPases are molecular switches that play an important role in regulating the behavior of a variety of tumor cells. RhoA GTPase-activating protein 26 (ARHGAP26) is a GTPase-activating protein and inhibits the activity of Rho GTPases by promoting the hydrolytic ability of Rho GTPases. It also affects tumorigenesis and progression of various tumors through several methods, including formation of abnormal fusion genes and circular RNA. This review summarizes the biological functions and molecular mechanisms of ARHGAP26 in different tumors, proposes the potential clinical value of ARHGAP26 in cancer treatment, and discusses current issues that need to be addressed.