Circular RNA MTO1 suppresses tumorigenesis of gastric carcinoma by sponging miR-3200-5p and targeting PEBP1

miR-3200 accelerates the growth of liver cancer cells by enhancing Rab7A

Researches indicate miR-3200 is closely related to tumorigenesis, However, the role of miR-3200 in human hepatocarcinogenesis is still unclear. In this study, we clearly demonstrate that miR-3200 accelerates the growth of liver cancer cells in vivo and in vitro. Obviously, these findings are noteworthy that miR-3200 affects the transcriptional regulation for several genes, including DSP，BABAM2, Rab7A,SQSTM1,PRKAG2,CDK1,ABCE1,BECN1,PTEN,UPRT. And miR-3200 affects the transcriptional ability of several genes, such as, upregulating CADPS, DSP,FBXO32, PPCA,SGK1, PATXN7L1, PLK2,ITGB5,FZD3,HOXC8,HSPA1A,C-Myc,CyclnD1,CyclinE,PCNA and down -regulating SUV39H1, MYO1G, OLFML3, CBX5, PPDE2A, HOXA7, RAD54L, CDC45,SHMT7,MAD2L1,P27,IQGAP3,PTEN,P57,SCAMP3,etc...On the other hand, it is obvious that miR-3200 affects the translational ability of several genes, such as, upregulating GNS,UPRT,EIFAD,YOS1,SGK1,K-Ras,PKM2,C-myc,Pim1,CyclinD1,mTOR,erbB-2,CyclinE,PCNA,RRAS,ARAF,RAPH1,etc.. and down-regulating KDM2A, AATF, TMM17B, RAB8B, MYO1G,P21WAF1/Cip1,GADD45,PTEN,P27,P18,P57,SERBP1,RPL34,UFD1,Bax,ANXA6,GSK3β. Strikingly, miR-3200 affects some signaling pathway in liver cancer, including carbon metabolism signaling pathway, DNA replication pathway, FoxO signaling pathway, Hippo signaling pathway, serine and threonine metabolism signaling pathway, mTOR signaling pathway, Fatty acid biosynthesis signaling pathway, carcinogenesis-receptor activation signaling pathway, autophagy signaling pathway. Furthermore, our results suggest that miR-3200 enhances expression of RAB7A, and then Rab7A regulates the carcinogenic function of miR-3200 by increasing telomere remodeling in human liver cancer. These results are of great significance for the prevention and treatment of human liver cancer.

Triple Amplification Strategy of CHA-PER-DNAzyme for Ultrasensitive Detection of circRNA Associated with Hepatocellular Carcinoma

Biological and clinical studies have indicated that aberrant expression of circMTO1 served as a crucial biomarker for the diagnosis and prognosis of hepatocellular carcinoma (HCC) patients as well as a potential therapeutic target. However, the detection of circRNAs currently faces challenges such as homologous linear RNA interference and low-expression abundance of certain circRNAs. Therefore, we developed a triple amplification method based on catalytic hairpin assembly (CHA) activation by back-splice junction (BSJ), resulting in CHA products that triggered primer exchange reaction to generate DNAzyme. Subsequently, DNAzyme cleaved the fluorescent reporter chain, enabling ultrasensitive detection of hepatocellular carcinoma-associated circMTO1 through the output fluorescence signal. The catalytic hairpin opening sequence within CHA specifically targeted the BSJ sequence in circRNA, thereby avoiding false positive signals observed in circRNA assays due to the recognition of homologous linear RNA molecules. Moreover, this triple amplification method facilitated sensitive detection of circRNA and addressed the issue of low-abundance expression levels associated with circMTO1 in HCC samples. Notably, our newly designed assay for detecting circRNA exhibited a linear range from 1 fM to 100 nM with a detection limit of 0.265 fM. Furthermore, it demonstrated excellent and consistent performance even within complex systems. Our proposed method enabled the specific and sensitive detection of circMTO1 in various cancer cells and blood samples from HCC patients, providing an innovative approach for investigating the role of circRNA in tumorigenesis and development while promoting its clinical application.

Circular RNAs as the pivotal regulators of epithelial-mesenchymal transition in gastrointestinal tumor cells

Gastrointestinal (GI) cancers, as the most common human malignancies are always considered one of the most important health challenges in the world. Late diagnosis in advanced tumor stages is one of the main reasons for the high mortality rate and treatment failure in these patients. Therefore, investigating the molecular pathways involved in GI tumor progression is required to introduce the efficient markers for the early tumor diagnosis. Epithelial-mesenchymal transition (EMT) is one of the main cellular mechanisms involved in the GI tumor metastasis. Non-coding RNAs (ncRNAs) are one of the main regulatory factors in EMT process. Circular RNAs (circRNAs) are a group of covalently closed loop ncRNAs that have higher stability in body fluids compared with other ncRNAs. Considering the importance of circRNAs in regulation of EMT process, in the present review we discussed the role of circRNAs in EMT process during GI tumor invasion. It has been reported that circRNAs mainly affect the EMT process through the regulation of EMT-specific transcription factors and signaling pathways such as WNT, PI3K/AKT, TGF-β, and MAPK. This review can be an effective step in introducing a circRNA/EMT based diagnostic panel marker for the early tumor detection among GI cancer patients.

Investigation of the clinicopathological and prognostic role of circMTO1 in multiple cancers

OBJECTIVE

To observe the prognostic value of circular RNA mitochondrial tRNA translation optimization 1 (circMTO1) in human tumors.

METHODS

We searched multiple databases for related reports published before November 01, 2021. The OR/HR and 95% CI were extracted to explore the correlation between circMTO1 expression and clinicopathological features in various cancers. The stability of the results from meta-analysis was estimated via sensitivity analysis. We adopted Begg's funnel plots and Egger's test to appraise the potential bias of publication. Subgroup analysis for overall survival (OS) were also performed.

RESULTS

11 studies containing 1383 patients and 4 articles including 536 patients were enrolled. We found that low expression status of circMTO1 was significantly related to big tumor size (OR=2.11, 95% CI: 1.26-3.56, P<0.05), poor differentiation tumors (OR=2.09, 95% CI: 1.46-2.98, P<0.05), OS (HR=2.02, 95% CI: 1.63-2.50, P<0.05), disease-free survival (DFS) (HR=1.83, 95% CI: 1.27-2.56, P<0.05) of cancers. Subgroup analysis indicated that low expression status of circMTO1 was correlated with OS, regardless of analysis method, cut-off value, case number and NOS score.

CONCLUSIONS

The low expression of circMTO1 may predict big tumor size, poor differentiation and worse outcome of cancer, presenting that circMTO1 may be a useful biomarker for prognosis of tumors.

Circular RNA circ_0065378 upregulates tumor suppressor candidate 1 by competitively binding with miR-4701-5p to alleviate colorectal cancer progression

BACKGROUND AND AIM

Colorectal cancer (CRC), the third most lethal human cancer worldwide, seriously threatens human health and life. Numerous circular RNAs (circRNAs) including circ_PLXNB1 (hsa_circ_0065378) have been confirmed to be dysregulated in CRC by RNA-seq analysis. We aimed to explore the functional role of circ_PLXNB1 in CRC malignant behaviors and clarify its potential molecular mechanism.

METHODS

Gene expression levels of circ_PLXNB1 and miR-4701-5p were determined by quantitative real-time polymerase chain reaction analysis. MTT and Transwell assays were conducted to measure cell proliferation, invasion, and migration. Protein expression of tumor suppressor candidate 1 (TUSC1), E-cadherin and N-cadherin was determined by western blot analysis. Mouse xenograft models were used to investigate the role of circ_PLXNB1 in tumor growth.

RESULTS

The results showed that gene expression of circ_PLXNB1 in CRC tissues was significantly downregulated. Overexpression of circ_PLXNB1 inhibited the malignant behaviors of CRC cells, as manifested by the decrease in cell proliferation, cell invasion, migration, and EMT. Mechanistically, circ_PLXNB1 exerted its functional effects by binding with miR-4701-5p. Moreover, TUSC1 siRNA partially abolished the suppressive effect of the miR-4701-5p inhibitor or circ_PLXNB1 on CRC cell malignant behaviors.

CONCLUSIONS

Circ_PLXNB1 attenuated CRC progression by binding with miR-4701-5p to overexpress TUSC1, indicating that the circ_PLXNB1/miR-4701-5p/TUSC1 axis might be a potential novel molecular target in CRC diagnosis and therapy.

Circular RNA mitochondrial translation optimization 1 correlates with less lymph node metastasis, longer disease-free survival, and higher chemotherapy sensitivity in gastric cancer

Objective

Circular‐mitochondrial translation optimization 1 (circ‐MTO1) inhibits the progression of gastric cancer by regulating the growth, apoptosis, and invasion of tumor cells. However, its clinical potential as a biomarker for gastric cancer remains to be further evaluated. This study aimed to assess circ‐MTO1 expression and its correlation with clinical features and prognosis in gastric cancer patients, as well as the effect of circ‐MTO1 on the sensitivity to chemotherapy in gastric cancer cells.

Methods

Circ‐MTO1 in tumor and adjacent tissues of 97 gastric cancer patients undergoing resection was examined by reverse transcription‐quantitative polymerase chain reaction. HGC‐27 and NCI‐N87 cells transfected by circ‐MOT1 overexpression plasmid (OE‐circ‐MOT1) and negative control (OE‐NC) were treated with 0‒6.4 μM oxaliplatin. Relative cell viability was detected using Cell Counting Kit‐8.

Results

Circ‐MTO1 was insufficiently expressed in gastric tumor tissue (median (interquartile range): 0.403 (0.288‒0.518)) compared with adjacent tissue (median (interquartile range): 1.000 (0.715‒1.524)) (p < 0.001). Besides, tumor circ‐MTO1 was correlated with less lymph node metastasis (p = 0.014) and low TNM stage (p = 0.039), while was not correlated with demographic features or other clinical characteristics (all p > 0.05). Furthermore, tumor circ‐MTO1 high expression was independently correlated with prolonged disease‐free survival (DFS) (p = 0.013, adjusted hazard ratio (95% confidential interval): 0.314 (0.126‒0.782)), but was not correlated with overall survival (p > 0.05). Lastly, in gastric cancer cells, OE‐circ‐MTO1 apparently decreased relative cell viabilities at oxaliplatin concentrations of 0.4, 0.8, 1.6, and 3.2 μM (all p < 0.05).

Conclusion

Circ‐MTO1 correlates with less lymph node metastasis, prolonged DFS, and improved chemotherapy sensitivity in gastric cancer.

CircMTO1 suppresses hepatocellular carcinoma progression via the miR-541-5p/ZIC1 axis by regulating Wnt/β-catenin signaling pathway and epithelial-to-mesenchymal transition

CircRNA mitochondrial tRNA translation optimization 1 (circMTO1) functions as a tumor suppressor usually and is related to the progression of many tumors, including hepatocellular carcinoma (HCC). CircMTO1 is downregulated in HCC as compared to adjacent nontumor tissue, which may suppress the HCC progression by certain signal pathways. However, the underlying signal pathway remains largely unknown. The interactions between circMTO1 and miR-541-5p were predicted through bioinformatics analysis and verified using pull-down and dual-luciferase reporter assays. CCK-8, transwell, and apoptosis assays were performed to determine the effect of miR-541-5p on HCC progression. Using bioinformatic analysis, dual-luciferase reporter assay, RT-qPCR, and western blot, ZIC1 was found to be the downstream target gene of miR-541-5p. The regulatory mechanisms of circMTO1, miR-541-5p, and ZIC1 were investigated using in vitro and in vivo rescue experiments. The results depicted that silencing circMTO1 or upregulating miR-541-5p expression facilitated HCC cell proliferation, migration, and invasion and inhibited apoptosis. CircMTO1 silencing upregulated the expression of downstream ZIC1 regulators of the Wnt/β-catenin pathway markers, β-catenin, cyclin D1, c-myc, and the mesenchymal markers N-cadherin, Vimentin, and MMP2, while the epithelial marker E-cadherin was downregulated. MiR-541-5p knockdown had the opposite effect and reversed the effect of circMTO1 silencing on the regulation of downstream ZIC1 regulators. Intratumoral injection of miR-541-5p inhibitor suppressed tumor growth and reversed the effect of circMTO1 silencing on the promotion of tumor growth in HCC. These findings indicated that circMTO1 suppressed HCC progression via the circMTO1/ miR-541-5p/ZIC1 axis by regulating Wnt/β-catenin signaling and epithelial-to-mesenchymal transition, making it a novel therapeutic target.

Circ_0004104 Accelerates the Progression of Gastric Cancer by Regulating the miR-539-3p/RNF2 Axis

BACKGROUND

Circular RNA (circRNA) has been shown to be closely associated with cancer progression, including gastric cancer (GC). However, the function of circ_0004104 in GC progression has not been clarified.

AIMS

The purpose of this study was to explore the role of circ_0004104 in GC progression.

METHODS

The expression levels of circ_0004104, miR-539-3p, and ring finger protein 2 (RNF2) were assessed using quantitative real-time polymerase chain reaction. Cell proliferation was measured by 3-(4,5-dimethyl-2 thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, and cell migration and invasion were detected using transwell assay. The levels of glutamine, glutamate, and α-ketoglutarate were determined to evaluate the glutaminolysis of cells, and the protein levels of glutaminolysis-related markers and RNF2 were detected using western blot analysis. Furthermore, Dual-Luciferase Reporter Assay was employed to assess the interaction between miR-539-3p and circ_0004104 or RNF2. Animal experiments were carried out to evaluate the effect of circ_0004104 silencing on GC tumor growth in vivo.

RESULTS

Circ_0004104 was upregulated in GC, and its knockdown repressed the proliferation, metastasis, and glutaminolysis of GC cells in vitro and reduced GC tumor growth in vivo. Furthermore, we discovered that circ_0004104 could sponge miR-539-3p and miR-539-3p could target RNF2. The rescue experiments suggested that miR-539-3p inhibitor could reverse the suppressive effect of circ_0004104 silencing on GC progression, and RNF2 overexpression also reversed the inhibition effect of miR-539-3p mimic on GC progression.

CONCLUSION

Circ_0004104 accelerated GC progression via regulating the miR-539-3p/RNF2 axis, indicating that circ_0004104 might be a potential therapeutic target for GC.

CircSLC7A6 promotes the progression of Wilms' tumor via microRNA-107/ ABL proto-oncogene 2 axis

The dysregulation of circular RNAs (circRNAs) has been proved to be involved in the carcinogenesis of various cancers. Nevertheless, the biological function of circSLC7A6 remains unclear in Wilms’ tumor (WT). In our study, we found that circSLC7A6 was upregulated in cancerous WT tissues and cells. Cell apoptosis was increased while cell viability, migration, and invasion were repressed by circSLC7A6 silencing. Besides, circSLC7A6 knockdown suppressed WT tumor growth in vivo. miR-107 was identified as a direct target of circSLC7A6, and circSLC7A6 could negatively regulate miR-107 expression. In addition, circSLC7A6 knockdown inhibited WT progression, while the effect was partially abolished by the downregulation of miR-107. Additionally, ABL proto-oncogene 2 axis (ABL2) was verified as a downstream gene of miR-107, and circSLC7A6 could upregulate ABL2 expression by serving as a ceRNA of miR-107. Moreover, functional assays revealed that ABL2 overexpression reversed the impact of circSLC7A6 depletion on cell proliferation, migration, invasion, and apoptosis of WT. In conclusion, the present study demonstrated that circSLC7A6 facilitated WT progression by upregulating ABL2 through inhibiting miR-107 expression. These results suggested that circSLC7A6 might serve as a potential therapeutic target for WT.

Circular RNA MTO1 intercorrelates with microRNA-630, both associate with Enneking stage and/or pathological fracture as well as prognosis in osteosarcoma patients

Objective

Circular RNA‐mitochondrial tRNA translation optimization 1 (circ‐MTO1) not only involves in bioprocess of various cancers, but also regulates osteosarcoma progression by regulating microRNA‐630 (miR‐630). However, the clinical role of circ‐MTO1 and miR‐630 in osteosarcoma is still obscure. This study aimed to assess the correlation of circ‐MTO1 and miR‐630 with disease features and prognosis and to explore their association with each other in osteosarcoma patients.

Methods

Forty‐four osteosarcoma patients who received neoadjuvant chemotherapy to surgical resection were analyzed in this retrospective study. Then, circ‐MTO1 and miR‐630 expressions were evaluated in tumor and adjacent non‐tumor specimens by reverse transcription quantitative polymerase chain reaction.

Results

Circ‐MTO1 was lower in tumor than in non‐tumor tissues (p<0.001); meanwhile, its elevated tumor expression was correlated with less advanced Enneking stage (p=0.049), good neoadjuvant chemotherapy response (p=0.029), and longer disease‐free survival (DFS) (p=0.047). However, no association was found between circ‐MTO1 and overall survival (OS) (p=0.122). Additionally, miR‐630 in tumor was higher than in non‐tumor tissues (p<0.001), while its raised tumor expression was associated with pathological fracture occurrence (p=0.003), advanced Enneking stage (p=0.036), poor neoadjuvant chemotherapy response (p=0.035), and shorter DFS (p=0.011). However, no association was found between miR‐630 and OS (p=0.066). In addition, tumor circ‐MTO1 was negatively associated with miR‐630 (r=−0.323, p=0.032).

Conclusion

Circ‐MTO1 and miR‐630 expressions are inter‐correlated and dysregulated in osteosarcoma patients. Besides, they associate with Enneking stage and/or pathological fracture, as well as neoadjuvant treatment response and accumulating DFS in these patients.

Candidate oncogene circularNOP10 mediates gastric cancer progression by regulating miR-204/SIRT1 pathway

Background

The role of circular RNA (circRNA) in gastric cancer (GC) is attracting increasing attention. CircNOP10 (hsa_circ-0034351) has been reported to be upregulated in human GC tissue. However, the biological role and mechanism of circNOP10 in GC remain unknown.

Methods

Circular RNA expression profile of GC was detected based on microarray, and circNOP10 was identified for the subsequent investigation. Clinical samples of GC tissue and patient blood were obtained from the Zhongda Hospital, Southeast University. The different degraded GC cell lines were presented in our laboratory. The function and mechanism of circNOP10 in GC were investigated using Western blot, qRT-PCR, flow cytometry, in situ hybridization and pull down experiment.

Results

The results indicated that increased circNOP10 in GC tissue was involved in tumor stage and prognosis. In addition, circNOP10 sponged microRNA-24 (miR-204)-mediated biological processes through sirtuin 1 (SIRT1), which further confirmed that the circNOP10/miR-204/SIRT1 pathway promoted proliferation and migration as well as epithelial-mesenchymal transition (EMT) through the NF-κβ pathway in GC cell lines.

Conclusions

Candidate oncogene circNOP10 mediated GC cell proliferation, arrest cell cycle in G₂/M phase, induced cell apoptosis, enhanced tumor metastasis, as well as EMT by activating the miR-204/SIRT1 pathway, suggesting that it may serve as a potential biomarker in GC therapy.

CircMTO1: A circular RNA with roles in the carcinogenesis

Circular RNAs (circRNAs) have a closed loop structure which endows them high stability. These transcripts are made through back splicing instead of classical splicing and are abundant in the human transcriptome. Recent advances in the development and implementation of high-throughput sequencing methods in cooperation with novel bioinformatics tools have shown contribution of circRNAs in the developmental processes, physiological settings and pathoetiology of cancers. CircMTO1 is a circRNA which was firstly identified as a down-regulated circRNA in hepatocellular carcinoma through circRNA profiling using microarray technique. Subsequent independent studies in lung adenocarcinoma, colorectal cancer, bladder cancer, glioblastoma, prostate cancer, osteosarcoma, gastric cancer and ovarian cancer have verified down-regulation of circMTO1 in neoplastic tissues compared with non-neoplastic ones. However, expression of circMTO1 has been found to be up-regulated in cervical and gallbladder cancers. miR-17, miR-9, miR-221, miR-6893, miR-92, miR-219a-5p, miR-337, miR-630, miR-3200-5p and miR-199a-3p have been shown to be sequestered by circMTO1. This circRNA can regulate activity of Notch, Wnt/β-Catenin, TGF-β/Smad, JAK1/STAT3 and AMPK signaling pathways. In the current study, we review the literature on the role of circMTO1 in the tumorigenesis.

The Roles of circMTO1 in Cancer

Circular RNAs (circRNAs) are a recently discovered type of covalently-closed circular non-coding RNAs, mainly formed by non-sequential back-splicing of precursor mRNAs (pre-mRNAs). Recent studies have demonstrated that circRNAs can have either oncogenic or tumor-suppressor roles depending on the cellular context. CircRNA mitochondrial tRNA translation optimization 1 (circMTO1), a recently reported circular RNA originating from exons of MTO1 located on chromosome 6q13, was proved to be abnormally expressed in many malignant tumors, such as hepatocellular carcinoma, gastric carcinoma and colorectal cancer, resulting in tumor initiation and progression. However, there are no reviews focusing on the roles of circMTO1 in cancer. Here, we first summarize the main biological characteristics of circMTO1, and then focus on its biological functions and the possible underlying molecular mechanisms. Finally, we summarize the roles of circMTO1 in cancer and discuss future prospects in this area of research.

Biological roles and potential clinical values of circular RNAs in gastrointestinal malignancies

Circular RNAs (circRNAs), a class of endogenous RNA molecules, are produced by alternative splicing of precursor RNA and are covalently linked at the 5' and 3' ends. Recent studies have revealed that dysregulated circRNAs are closely related to the occurrence and progression of gastrointestinal malignancies. Accumulating evidence indicates that circRNAs, including circPVT1, circLARP4, circ-SFMBT2, cir-ITCH, circRNA_100782, circ_100395, circ-DONSON, hsa_circ_0001368, circNRIP1, circFAT1(e2), circCCDC66, circSMARCA5, circ-ZNF652, and circ_0030235 play important roles in the proliferation, differentiation, invasion, and metastasis of cancer cells through a variety of mechanisms, such as acting as microRNA sponges, interacting with RNA-binding proteins, regulating gene transcription and alternative splicing, and being translated into proteins. With the characteristics of high abundance, high stability, extensive functions, and certain tissue-, time- and disease-specific expressions, circRNAs are expected to provide novel perspectives for the diagnoses and treatments of gastrointestinal malignancies.

Comprehensive Analysis of Correlations in the Expression of miRNA Genes and Immune Checkpoint Genes in Bladder Cancer Cells

Personalised medicine is the future and hope for many patients, including those with cancers. Early detection, as well as rapid, well-selected treatment, are key factors leading to a good prognosis. MicroRNA mediated gene regulation is a promising area of development for new diagnostic and therapeutic methods, crucial for better prospects for patients. Bladder cancer is a frequent neoplasm, with high lethality and lacking modern, advanced therapeutic modalities, such as immunotherapy. MicroRNAs are involved in bladder cancer pathogenesis, proliferation, control and response to treatment, which we summarise in this perspective in response to lack of recent review publications in this field. We further performed a correlation-based analysis of microRNA and gene expression data in bladder cancer (BLCA) TCGA dataset. We identified 27 microRNAs hits with opposite expression profiles to genes involved in immune response in bladder cancer, and 24 microRNAs hits with similar expression profiles. We discuss previous studies linking the functions of these microRNAs to bladder cancer and assess if they are good candidates for personalised medicine therapeutics and diagnostics. The discussed functions include regulation of gene expression, interplay with transcription factors, response to treatment, apoptosis, cell proliferation and angiogenesis, initiation and development of cancer, genome instability and tumour-associated inflammatory reaction.

Circular RNAs in Human Cancer

Circular RNAs (circRNAs) are a class of endogenous single-stranded covalently closed RNAs, primarily produced from pre-mRNAs via non-canonical back-splicing. circRNAs are highly conserved, stable, and expressed in tissue- and development-specific pattern. circRNAs play essential roles in physiological process as well as cancer biology. By the advances of deep sequencing and bioinformatics, the number of circRNAs have increased explosively. circRNAs function as miRNA/protein sponge, protein scaffold, protein recruitment, enhancer of protein function, as well as templates for translation involved in the regulation of transcription/splicing, translation, protein degradation, and pri-miRNA processing in human cancers and contributed to the pathogenesis of cancer. Numerous circRNAs may function in diverse manners. In this review, we survey the current understanding of circRNA functions in human cancer including miRNA sponge, circRNA-protein interaction, and circRNA-encoded protein, and summarize available databases for circRNA annotation and functional prediction.

Hypoxia‑induced circCCDC66 promotes the tumorigenesis of colorectal cancer via the miR‑3140/autophagy pathway

Circular RNAs (circRNAs) have been reported to be involved in the progression of colorectal cancer (CRC). However, the biological role of circCCDC66 in CRC remains unclear. Therefore, the present study aimed to elucidate the mechanisms through which circCCDC66 affects the hypoxia‑induced progression of CRC. It was found that hypoxia promoted the progression of CRC and upregulated the expression of circCCDC66. Furthermore, circCCDC66‑knockdown reduced viability, migration and invasion, and enhanced the apoptosis of hypoxia‑exposed CRC cells. Using the starBase database, it was identified that circCCDC66 may bind to miR‑3140. Subsequently, it was confirmed that circCCDC66 serves as a sponge of miR‑3140 and the depletion of miR‑3140 partly abolished the effects of circCCDC66 on the phenotype of hypoxia‑exposed CRC cells. In addition, miR‑3140 was validated to inhibit the autophagy pathway. The use of an autophagy inducer partially reversed the miR‑3140 overexpression‑induced inhibition of the viability and invasion, and the promotion of the apoptosis of hypoxia‑exposed CRC cells. In summary, the findings of the present study demonstrated that circCCDC66 facilitates the development of CRC cells under hypoxic conditions via regulation of miR‑3140/autophagy. These findings may provide a novel therapeutic option for patients with CRC.

CircPDZD8 promotes gastric cancer progression by regulating CHD9 via sponging miR-197-5p

CircRNAs have been shown to be associated with gastric cancer tumorigenesis. But little was known about the role of circPDZD8 in gastric cancer. CircPDZD8 was up-regulated in gastric cancer tissues and cells, Kaplan-Meier survival analysis indicated that gastric patients had a poor overall survival when circPDZD8 levels were high. CircPDZD8 knockdown could hinder proliferation and migration of gastric cancer cells. MiR-197-5p, which was down-regulated in gastric cancer, was shown to be a target of circPDZD8 and was inversely correlated with circPDZD8 expression. CHD9, as a target gene of miR-197-5p, was negatively regulated by miR-197-5p and positively correlated with circPDZD8 expression. Importantly, circPDZD8 could up-regulate CHD9 expression by sponging miR-197-5p, and modulate cell progression by regulation of the miR-197-5p/CHD9 axis in gastric cancer. CircPDZD8 knockdown repressed the progression of gastric cancer cells by sponging miR-197-5p and down-regulating CHD9.

Circular RNAs in gastrointestinal cancer: Current knowledge, biomarkers and targeted therapy (Review)

Circular RNAs (circRNAs) are a type of endogenous non‑coding RNAs that are connected at the 3' and 5' ends by exon or intron cyclization, which forms a covalently closed loop. They are stable, well conserved, exhibit specific expression in mammalian cells and can function as microRNA (miRNA or miR) sponges to regulate the target genes of miRNAs, which influences biological processes. Such as tumor proliferation, invasion, metastasis, apoptosis and tumor stage. circRNAs represent promising candidates for clinical diagnosis and treatment. In the present review, the biogenesis, classification and functions of circRNAs in tumors are briefly summarized and discussed. In addition, the participation of circRNAs in signal transduction pathways regulating gastrointestinal cancer cellular functions is highlighted.

CircFLNA Acts as a Sponge of miR-646 to Facilitate the Proliferation, Metastasis, Glycolysis, and Apoptosis Inhibition of Gastric Cancer by Targeting PFKFB2

Background

Many studies have confirmed that circular (circRNA) is involved in the development of gastric cancer (GC). However, the role of circFLNA in the progression of GC remains unclear.

Methods

Quantitative real-time PCR (qRT-PCR) was used to measure the relative expression of circFLNA, microRNA (miR)-646 and 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 2 (PFKFB2). Cell counting kit 8 (CCK8) assay, transwell assay and flow cytometry were performed to determine the proliferation, migration, invasion and apoptosis of cells, respectively. GC tumor xenograft models were built to confirm the function of circFLNA silencing on GC tumor growth in vivo. Furthermore, the lactate production, glucose consumption, ATP level and glucose uptake were detected to assess the glycolysis of cells. Then, the interaction between miR-646 and circFLNA or PFKFB2 was confirmed using dual-luciferase reporter assay. RNA immunoprecipitation (RIP) assay was used to verify the interaction between miR-646 and circFLNA further. In addition, Western blot (WB) analysis was employed to detect the relative protein expression of PFKFB2.

Results

Our results found that circFLNA was upregulated in GC tissues and cells. Silencing of circFLNA could suppress the proliferation, migration, invasion, glycolysis, and enhance the apoptosis of GC cells. Also, circFLNA knockdown reduced GC tumor volume and weight in vivo. Further experiments revealed that circFLNA could sponge miR-646, and miR-646 could target PFKFB2. The rescue experiments indicated that miR-646 inhibitor could reverse the suppressive effect of circFLNA silencing on GC progression, and PFKFB2 overexpression also could invert the inhibition effect of miR-646 on GC progression.

Conclusion

Our data concluded that circFLNA played a pro-cancer role in GC, which suggested that circFLNA might be a potential biomarker for GC treatment.

hsa_circ_0000520 influences herceptin resistance in gastric cancer cells through PI3K-Akt signaling pathway

Background

To investigate whether hsa_circ_0000520 affects Herceptin resistance in gastric cancer by regulating the PI3K‐AKT signaling.

Methods

The expression of hsa_circ_0000520 was detected by qRT‐PCR in gastric cancer tissues and cell lines. A Herceptin‐resistant gastric cancer cell was established. PcDNA and pcDNA‐hsa_circ_0000520 were transfected into NCI‐N87R cells and treated with Herceptin at a concentration of 10 μg/mL for 24 hours. MTT tested cell proliferation, and apoptosis was measured by flow cytometry. IGF‐1 treatment was used to activate PI3K‐Akt signaling. The expression levels of related proteins were detected.

Results

The expression of hsa_circ_0000520 was reduced in gastric cancer tissues and cell lines, and hsa_circ_0000520 in NCI‐N87R cells was significantly lower than that of NCI‐N87 cells. Compared with the CON group, the cell viability of the Herceptin group was significantly reduced, the apoptosis rate was significantly increased, the level of Bax protein was significantly increased, and the levels of Bcl‐2, p‐PI3K, and p‐Akt protein were significantly reduced. Compared with the Herceptin + pcDNA group, the cell viability of the Herceptin + hsa_circ_0000520 group was significantly reduced, the apoptosis rate was significantly increased, the level of Bax protein was significantly increased, and the levels of p‐PI3K and p‐Akt proteins were significantly reduced. After IGF‐1 treatment, the cell viability was significantly increased, the apoptosis rate was significantly reduced, the level of Bax protein was significantly reduced, and the level of Bcl‐2 protein was significantly increased.

Conclusion

Hsa_circ_0000520 overexpression may reverse the Herceptin resistance of gastric cancer cells by inhibiting the PI3K‐Akt signaling pathway.

Circular RNAs in gastric cancer: Biomarkers for early diagnosis

Circular RNAs (circRNAs) are highly conserved and stable closed-loop non-coding RNAs. They are involved in numerous biological functions, including regulating gene transcription or protein translation by interacting with proteins and regulating expression of microRNAs. The aberrant expression of circRNAs has been reported in many cancers, including gastric cancer. By regulating gene expression, circRNAs are able to affect the proliferation, invasion and metastasis of gastric cancer. The current review focused on the characteristics and biological functions of circRNAs, the carcinogenic potential and the possible implications of circRNAs on the diagnosis and treatment of gastric cancer. In conclusion, circRNAs may serve as potential biomarkers for diagnosis, as well as therapeutic targets.