Circular RNA Profiling Reveals That circRNA_104433 Regulates Cell Growth by Targeting miR-497-5p in Gastric Cancer

Circular RNA circRNA_100349 functions as a miR-218-5p sponge for suppressing the cell proliferation of gastric cancer via regulation of IGF2 expression

BACKGROUND

Circular RNAs (circRNAs) hold critical importance due to their notable function in developing Gastric Cancer (GC), which is a malignancy with the third most frequent occurrence worldwide. The aim of this study was to see if circRNA_0044516 would control GC cell proliferation and establish more effective therapeutic strategies.

METHODS

In GC tissues or cells, quantitative Real‑Time Polymerase Chain Reaction (qRT-PCR) was employed for the detection of the expression of circRNA_100349, Insulin-like Growth Factor II (IGF2), and miR-218-5p. CCK-8 assays were employed to gauge the proliferation of cells. A luciferase reporter was employed to establish the relationship of circRNA_100349 or IGF2 with miR-218-5p.

RESULTS

CircRNA_100349 was observed to undergo upregulation in GC cell lines along with tissues. GC cell proliferation was prevented by downregulating circRNA_100349. MiR-149 was targeted by CircRNA_100349, and its downregulation increased the amount of miR-218-5p in GC cells. Simultaneously silencing circRNA_100349 decreased IGF2 expression via miR-218-5p, and thus suppressed GC cell proliferation. Furthermore, in nude mice, circRNA_100349 knockdown prevented the tumor development of GC cells.

CONCLUSIONS

The findings furnished evidence of the critical involvement of circRNA_100349 in GC and that its downregulation impedes GC cell proliferation via the miR-218-5p/IGF2 axis.

Circular RNAs in Cell Cycle Regulation of Cancers

Cancer has been one of the most problematic health issues globally. Typically, all cancers share a common characteristic or cancer hallmark, such as sustaining cell proliferation, evading growth suppressors, and enabling replicative immortality. Indeed, cell cycle regulation in cancer is often found to be dysregulated, leading to an increase in aggressiveness. These dysregulations are partly due to the aberrant cellular signaling pathway. In recent years, circular RNAs (circRNAs) have been widely studied and classified as one of the regulators in various cancers. Numerous studies have reported that circRNAs antagonize or promote cancer progression through the modulation of cell cycle regulators or their associated signaling pathways, directly or indirectly. Mostly, circRNAs are known to act as microRNA (miRNA) sponges. However, they also hold additional mechanisms for regulating cellular activity, including protein binding, RNA-binding protein (RBP) recruitment, and protein translation. This review will discuss the current knowledge of how circRNAs regulate cell cycle-related proteins through the abovementioned mechanisms in different cancers.

miR-497-5p Expression and Biological Activity in Gastric Cancer

Background: This research aims to investigate the expression and biological roles of miR-497-5p in gastric cancer (GC), and its possible mechanisms. Methods: Real Time Quantitative PCR (RT-qPCR) was performed to detect miR-497-5p in GC and normal tissues, as well as GC cell lines versus normal gastric mucosal cells (GES-1). The effects of miR-497-5p overexpression on proliferation were measured by the cell counting kit-8 (CCK8) assay and ethidium bromide (EdU) assay. Flow cytometry was used to assess the cell cycle. The migration and invasion were evaluated by scratch assay and Transwell assay, respectively. Gene targets of miR-497-5p were predicted using "multiMiR" R package combined with mirTarPathway database. And then luciferase reporter experiment was used to evaluate the activity of ERBB2 by miR-497-5p mimics in GC cell line. Besides, functional experiments were performed to verify the impact of miR-497-5p /ERBB2 on phenotypes of GC cells. Results: Compared with the normal tissues and mucosal cells, miR-497-5p was reduced in GC tissues and GC cell lines. miR-497-5p significantly decreased proliferation, migration, and invasion capacity, with an elevated apoptosis ratio of gastric cancer cells. Bioinformatics indicated that ERBB2 might be the potential target of miR-497-5p Dual-luciferase reporter experiments showed it adversely regulated ERBB2 3'UTR luciferase activity. The expression of ERBB2 in GC tissues and cells is significantly higher compared to normal tissues and cells. Over-expression of ERBB2 in gastric cancer cells significantly reduced miR-497-5p's inhibitory effect on the malignant behavior of GC cells. Conclusion: miR-497-5p was significantly down-regulated in GC tissues and cells, which inhibited the malignant features of GC cells by targeting ERBB2.

Circular RNA circHMCU promotes breast tumorigenesis through miR-4458/PGK1 regulatory cascade

BACKGROUND

Circular RNAs (circRNAs) are abnormally expressed in breast cancer (BC). However, the biological function and mechanism of circHMCU still need to be further explored.

METHODS

The expression levels of circHMCU, miR-4458 and phosphoglycerate kinase 1 (PGK1) were measured by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. The glucose uptake, lactate production and ATP level were assayed by related commercial kits. Cell Counting Kit-8 (CCK8), 5'-ethynyl-2'-deoxyuridine (EdU) and flow cytometry assays were used to test cell proliferation and apoptosis, respectively. The migratory and invasive abilities were detected by transwell and wound-healing assays. The relationships among circHMCU, miR-4458 and PGK1 were verified by dual-luciferase reporter assay. The function of circHMCU in tumor growth was evaluated by animal studies.

RESULTS

CircHMCU was upregulated in BC tissues and cell lines, whereas miR-4458 was downregulated. For biological experiments, circHMCU knockdown inhibited cell proliferation, migration, glycolysis, while promoted cell apoptosis. CircHMCU bound miR-4458, and miR-4458 targeted PGK1. MiR-4458 inhibition reversed circHMCM knockdown-mediated effects on BC cell malignant behaviors. MiR-4458 overexpression suppressed cell glycolysis, proliferation, and metastasis and promoted apoptosis in BC cells through PGK1 upregulation. Additionally, circHMCU suppressed tumor growth in vivo.

CONCLUSION

CircHMCU acted as an oncogenic factor by regulating the miR-4458/PGK1 axis in BC.

Circ_0000520 interacts with miR-512-5p to upregulate KIAA0100 to promote malignant behaviors in lung cancer

BACKGROUND

CircRNAs function as pivotal molecules to regulate the malignant development of lung cancer. This study was designed to research the functional role and how it acted in lung cancer progression.

METHODS

Circ_0000520, microRNA-512-5p (miR-512-5p) and Breast cancer-overexpressed gene 1 (KIAA0100) levels were measured through reverse transcription-quantitative polymerase chain reaction assay. Cell Counting Kit-8 assay and EdU assay were used to examine cell proliferation. Cell cycle and apoptosis were evaluated via flow cytometry. The protein levels were determined using western blot. Cell migration and invasion were assessed by wound healing assay and transwell assay. The circ_0000520 function in vivo was explored by tumor xenograft assay. The molecular interaction was analyzed via Dual-luciferase reporter assay.

RESULTS

Circ_0000520 was obviously upregulated in lung cancer tissues and cells. Silence of circ_0000520 inhibited proliferation, cell cycle progression, migration, invasion and angiogenesis but promoted cell apoptosis. Circ_0000520 downregulation reduced tumor growth of lung cancer in vivo. Circ_0000520 served as a miR-512-5p sponge. The oncogenic function of circ_0000520 was partly achieved by sponging miR-512-5p in lung cancer. KIAA0100 was a target of miR-512-5p and miR-512-5p inhibited the malignant behaviors of lung cancer cells via downregulating KIAA0100. Circ_0000520 targeted miR-512-5p to regulate the level of KIAA0100.

CONCLUSION

All these data demonstrated that circ_0000520 was able to drive the progression of lung cancer via the mediation of miR-512-5p/KIAA0100 axis. Circ_0000520 might be a potential biomarker for lung cancer.

Circ_0000189 Promotes the Malignancy of Glioma Cells via Regulating miR-192-5p-ZEB2 Axis

Background

Some recent studies have reported the role of circular RNAs (circRNAs) in modulating the tumorigenesis of human malignancies. Nevertheless, the expression characteristics, biological functions, and regulatory mechanism of circ_0000189 in glioma are unclear.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was utilized to detect the expression levels of circ_0000189, miR-192-5p, and ZEB2 mRNA in glioma tissues and cells. The association between the expression of circ_0000189 and the clinicopathological indicators and the features of magnetic resonance imaging (MRI) images of glioma patients were analyzed. Western blot was utilized to evaluate ZEB2 expression and epithelial-mesenchymal transition (EMT-)-related proteins (E-cadherin, N-cadherin, as well as Vimentin) in glioma cells. Cell proliferation was assessed employing cell counting kit-8 (CCK-8) and EdU experiments. Flow cytometry was used to detect the apoptotic rate of the cells. Cell migration and invasion were accessed employing Transwell assay. Moreover, dual luciferase reporter gene assay and RNA immunoprecipitation assay were employed to investigate the targeting relationship between miR-192-5p and circ_0000189, miR-192-5p, and ZEB2. Subcutaneous tumorigenesis experiment and lung metastasis experiment in nude mice were conducted to verify the regulatory function of circ_0000189 on the proliferation and metastasis of glioma cells in vivo.

Results

circ_0000189 was markedly overexpressed in glioma tissues and cell lines. Its high expression was associated with poor clinical pathological indicators and adverse MRI signs. Gain-of-function experiments and loss-of-function experiments confirmed that circ_0000189 overexpression facilitated the proliferation and migration, as well as invasion of glioma cells, and suppressed apoptosis, and facilitated epithelial-mesenchymal transition (EMT) process. Compared to the control group, knocking down circ_0000189 suppressed the malignant phenotypes of glioma cells both in vivo and in vitro. Working as a competitive endogenous RNA, circ_0000189 directly targeted miR-192-5p, and repressed its expression, and circ_0000189 positively modulated ZEB2 expression indirectly via repressing miR-192-5p.

Conclusion

circ_0000189 facilitates the progression of glioma by modulating miR-192-5p/ZEB2 axis.

Circular RNA FLNA acts as a sponge of miR-486-3p in promoting lung cancer progression via regulating XRCC1 and CYP1A1

Significantly high-expressed circFLNA has been found in various cancer cell lines, but not in lung cancer. Therefore, this study aimed to explore the role of circFLNA in the progression of lung cancer. The target gene of circFLNA was determined by bioinformatics and luciferase reporter assay. Viability, proliferation, migration, and invasion of the transfected cells were detected by CCK-8, colony formation, wound-healing, and transwell assays, respectively. A mouse subcutaneous xenotransplanted tumor model was established, and the expressions of circFLNA, miR-486-3p, XRCC1, CYP1A1, and related genes in the cancer cells and tissues were detected by RT-qPCR, Western blot, or immunohistochemistry. The current study found that miR-486-3p was low-expressed in lung cancer. MiR-486-3p, which has been found to target XRCC1 and CYP1A1, was regulated by circFLNA. CircFLNA was located in the cytoplasm and had a high expression in lung cancer cells. Cancer cell viability, proliferation, migration, and invasion were promoted by overexpressed circFLNA, XRCC1, and CYP1A1 but inhibited by miR-486-3p mimic and circFLNA knockdown. The weight of the xenotransplanted tumor was increased by circFLNA overexpression yet reduced by miR-486-3p mimic. Furthermore, miR-486-3p mimic reversed the effect of circFLNA overexpression on promoting lung cancer cells and tumors and regulating the expressions of miR-486-3p, XRCC1, CYP1A1, and metastasis/apoptosis/proliferation-related factors. However, overexpressed XRCC1 and CYP1A1 reversed the inhibitory effect of miR-486-3p mimic on cancer cells and tumors. In conclusion, circFLNA acted as a sponge of miR-486-3p to promote the proliferation, migration, and invasion of lung cancer cells in vitro and in vivo by regulating XRCC1 and CYP1A1.

[Research Progress in CircRNA and Radiotherapy Resistance of Non-small Cell Lung Cancer]

As the main type of lung cancer, non-small cell lung cancer (NSCLC) is a common cancer which is characterized by low 5-year survival rate and worse prognosis. Nowadays, some studies show that the low survival rate and worse prognosis are due to the resistance to radiotherapy caused by circRNA. Therefore, to find out the relationship between circRNA and radiotherapy resistance of NSCLC was imoprtant. According to research the relevant literatures, the relationship between circRNA and radiotherapy resistance of NSCLC was explored. CircRNA plays an important role in the invasion, metastasis, proliferation and treatment resistance of NSCLC. The radiation resistance of tumor cells induced by circRNA has become a crucial problem in radiotherapy. CircRNA plays an important role in the radiotherapy resistance of NSCLC.
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Circ-DONSON Facilitates the Malignant Progression of Gastric Cancer Depending on the Regulation of miR-149-5p/LDHA Axis

Earlier studies have shown that circular RNA (circRNA) expression is closely related to the malignant progression of cancer, but the role of circ-DONSON in gastric cancer (GC) has not been fully elucidated. The expression of circ-DONSON, miR-149-5p and lactate dehydrogenase A (LDHA) was measured via qRT-PCR. CCK8 assay was used to assess cell viability, and colony formation assay was performed to detect the number of colonies and the radiosensitivity of cells. Besides, flow cytometry, transwell assay and tube formation assay were employed to determine cell apoptosis, migration, invasion and angiogenesis. Western blot analysis was used to assess the protein expression. The interaction between miR-149-5p and circ-DONSON or LDHA was confirmed by dual-luciferase reporter assay. The influence of circ-DONSON on GC tumor growth in vivo was explored through constructing mice xenograft models. Our results suggested that circ-DONSON was highly expressed in GC tissues and cells. Loss-functional assay results confirmed that silenced circ-DONSON could inhibit the proliferation, metastasis and angiogenesis, while enhance the apoptosis and radiosensitivity of GC cells. In terms of mechanism, circ-DONSON could sponge miR-149-5p, which could target LDHA in GC. MiR-149-5p inhibitor or LDHA overexpression could reverse the suppression effect of circ-DONSON knockdown on GC progression. Additionally, our results also suggested that circ-DONSON silencing could restrain the tumor growth of GC in vivo. These results demonstrated that circ-DONSON could facilitate GC progression by increasing LDHA expression via sponging miR-149-5p, indicating that circ-DONSON might be a novel biomarker for GC treatment.

Circ_0007142 downregulates miR-874-3p-mediated GDPD5 on colorectal cancer cells

BACKGROUND

Ferroptosis is an iron-dependent and oxidative cell death form. Recent studies suggested that circular RNAs (circRNAs) regulated ferroptosis in tumour cells. Circ_0007142 was identified as a carcinogenic molecule in colorectal cancer (CRC), but its function on ferroptosis in CRC remains unknown.

METHODS

Circ_0007142, microRNA-874-3p (miR-874-3p) and glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5) levels were assayed using the quantitative real-time polymerase chain reaction (qRT-PCR). Cell survival and proliferation were measured by Cell Counting Kit-8 (CCK-8) assay. Protein detection was performed by Western blot. Cell apoptosis was analysed by flow cytometry. Ferroptosis was assessed by iron accumulation and oxidative stress. Target binding was evaluated by dual-luciferase reporter assay. In vivo research was conducted by tumour xenograft in mice.

RESULTS

Circ_0007142 was overexpressed in CRC. After expression inhibition of circ_0007142, proliferation was reduced, while apoptosis and ferroptosis were facilitated in CRC cells. Mechanically, circ_0007142 was found as a miR-874-3p sponge and miR-874-3p inhibitor eliminated the regulation of si-circ_0007142 in CRC cells. MiR-874-3p targeted GDPD5 and upregulation of GDPD5 reversed the miR-874-3p-triggered tumour inhibition and ferroptosis promotion in CRC cells. Moreover, GDPD5 was regulated by the circ_0007142/miR-874-3p axis. Circ_0007142 also affected CRC tumorigenesis in vivo through the regulation of miR-874-3p and GDPD5.

CONCLUSION

All these findings proved that circ_0007142/miR-874-3p/GDPD5 axis regulated tumorigenesis and ferroptosis of CRC cells. Circ_0007142 might be an available marker for ferroptosis in CRC therapy.

Carvedilol protects against the H2O2-induced cell damages in rat myoblasts by regulating the circ_NFIX/miR-125b-5p/TLR4 signal axis

ABSTRACT

Circular RNAs (circRNAs) have been involved in the regulation of various kinds of cardiovascular diseases, including acute myocardial infarction (AMI). This study was performed to investigate the molecular mechanism associated with circRNA nuclear factor IX (circ_NFIX) in carvedilol-mediated cardioprotection in H2O2-treated H9c2 cells. Flow cytometry was performed for the analysis of cell cycle and apoptosis. Cell proliferation was evaluated using colony formation assay and 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide (MTT) assay. Lactate dehydrogenase (LDH) activity was measured via LDH assay. The relative levels of circ_NFIX, microRNA-125b-5p (miR-125b-5p) and toll-like receptor 4 (TLR4) were determined via quantitative real-time polymerase chain reaction (qRT-PCR). Protein levels were examined by western blot. The target interaction was proved via dual-luciferase reporter assay. H2O2-induced cell cycle arrest, proliferation repression, apoptosis and LDH promotion in H9c2 cells were inhibited by carvedilol. Circ_NFIX level was reduced after carvedilol treatment in H2O2-treated H9c2 cells, and circ_NFIX overexpression inhibited the protective effects of carvedilol on H2O2-induced cell damages. Furthermore, circ_NFIX was validated to serve as a sponge of miR-125b-5p and the inhibitory function of circ_NFIX in carvedilol-induced cardioprotection was achieved by sponging miR-125b-5p. Moreover, TLR4 acted as a target gene of miR-125b-5p and miR-125b-5p inhibitor upregulated the TLR4 expression to suppress the protective effects of carvedilol on H2O2-treated H9c2 cells. In addition, circ_NFIX regulated the TLR4 level by exerting the sponge influence on miR-125b-5p. Rat model also indicated that Carv might suppressed the progression of AMI via regulating the levels of circ_NFIX, miR-125b-5p and TLR4. These findings suggested that carvedilol protected H9c2 cells against the H2O2-induced cell dysfunction through depending on the circ_NFIX/miR-125b-5p/TLR4 axis.

Down-regulation of hsa_circ_0006470 predicts tumor invasion: A new biomarker of gastric cancer

Background

Gastric cancer (GC) is a common cancer. Circular RNAs (circRNAs) regulate the pathogenesis of GC. This study aims to explore its potential as a GC biomarker.

Methods

The expression of hsa_circ_0006470 in GC tissues and GC cell lines was measured by quantitative reverse transcription‐polymerase chain reaction. The diagnostic value of hsa_circ_0006470 was estimated by the receiver operating characteristic (ROC) curve.

Results

Compared with adjacent normal tissues, the expression of hsa_circ_0006470 in GC tissues was significantly lower. The expression levels of hsa_circ_0006470 in different TNM stages and different invasion degrees were significantly different. The area under the ROC curve was 0.783, with sensitivity and specificity 0.725 and 0.750, respectively.

Conclusions

Hsa_circ_0006470 has a high value as a diagnostic biomarker for GC.

A comprehensive review on the role of protein tyrosine phosphatases in gastric cancer development and progression

The main post-translational reversible modulation of proteins is phosphorylation and dephosphorylation, catalyzed by protein kinases (PKs) and protein phosphatases (PPs) which is crucial for homeostasis. Imbalance in this crosstalk can be related to diseases, including cancer. Plenty of evidence indicates that protein tyrosine phosphatases (PTPs) can act as tumor suppressors and tumor promoters. In gastric cancer (GC), there is a lack of understanding of the molecular aspects behind the tumoral onset and progression. Here we describe several members of the PTP family related to gastric carcinogenesis. We discuss the associated molecular mechanisms which support the down or up modulation of different PTPs. We emphasize the Helicobacter pylori (H. pylori) virulence which is in part associated with the activation of PTP receptors. We also explore the involvement of intracellular redox state in response to H. pylori infection. In addition, some PTP members are under influence by genetic mutations, epigenetics mechanisms, and miRNA modulation. The understanding of multiple aspects of PTPs in GC may provide new targets and perspectives on drug development.

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.

RETRACTED ARTICLE: Circ_002117 binds to microRNA-370 and promotes endoplasmic reticulum stress-induced apoptosis in gastric cancer

BACKGROUND

Mounting evidence implicates circular RNAs (circRNAs) in various biological processes during cancer progression. Gastric cancer is a main cause of cancer-related deaths worldwide. Herein, we aimed at investigating whether circ_002117 mediates gastric cancer progression through endoplasmic reticulum (ER) stress.

METHODS

Bioinformatics analysis detected differentially expressed circRNAs and their target miRNA candidates, and RT-qPCR was performed to detect expression of circ_002117, microRNA (miRNA)-370 and HERPUD1 in gastric cancer tissues and cells. Gastric cancer cells were transfected with plasmids and their proliferative ability and apoptosis were detected with gain- and loss-of-function assay. The ER of treated cells was observed under a transmission electron microscope. Dual-luciferase reporter gene assay and RIP were performed to detect the interaction between HEPRUD1, miR-370 and circ_002117-treated cells were injected into mice to establish xenograft tumor model.

RESULTS

Circ_002117 and HEPRUD1 were poorly expressed whereas miR-370 was highly expressed in clinical cancer tissues and cells. Circ_002117 was indicated to target and suppress miR-370 expression, while HERPUD1 was directly targeted by miR-370. Circ_002117 overexpression or miR-370 deficiency promoted ER stress-induced apoptosis and decreased proliferation of gastric cancer cells, which was reversed by silencing of HEPRUD1. Circ_002117 overexpression or miR-370 depletion significantly suppressed gastric cancer tumorigenesis in vivo.

CONCLUSIONS

Taken altogether, circ_002117 facilitated ER stress-induced apoptosis in gastric cancer by upregulating HERPUD1 through miR-370 inhibition.

Circular RNA circRNA_103809 Accelerates Bladder Cancer Progression and Enhances Chemo-Resistance by Activation of miR-516a-5p/FBXL18 Axis

Background

Numerous researches have suggested that circular RNAs (circRNAs) play critical functions in bladder cancer (BC) progression. This study aims to investigate the potential roles of circRNA_103809 in regulating BC development.

Methods

qRT-PCR was used to analyze gene expression. CCK8 and colony formation were used to analyze cell proliferation. Transwell was utilized to examine cell migration and invasion. Gemcitabine was used to analyze the effect of circRNA_103809 on the chemo-resistance of BC cells. Luciferase reporter assay was performed to detect the RNA interactions.

Results

circRNA_103809 was highly expressed in BC tissues and cell lines. CircRNA_103809 high expression was associated with a poor progression in BC patients. CircRNA_103809 knockdown impaired the growth and metastasis of BC cells. Furthermore, circRNA_103809 silencing increased the sensitivity of BC cells to Gemcitabine treatment. CircRNA_103809 was the sponge for miR-516a-5p and promoted FBXL18 expression via restraining miR-516a-5p activity.

Conclusion

circRNA_103809 promotes proliferation, migration, invasion and chemo-resistance of BC cells through regulating miR-516a-5p/FBXL18 axis.

Circular RNAs in Gastric Cancer: Potential Biomarkers and Therapeutic Targets

Circular RNAs (circRNAs), as a recently established group of endogenous noncoding RNAs, have been involved in the occurrence and development of different malignancies. Gastric cancer (GC) remains a globally significant contributor to death in cancer patients due to insufficient early diagnosis, limited treatment measures, and poor prognosis. An increasing number of studies have found that many circRNAs are dysregulated in GC and are closely associated with its tumorigenesis and metastasis. Thus, circRNAs have the potential to serve as diagnostic and prognostic biomarkers and even therapeutic targets. This review comprehensively summarizes the most recent findings on how circRNAs influence GC progression and their clinical value. In addition, we present several methological deficiencies in the studies and provide some promising ideas for future research.

Circular RNA is a popular molecule in tumors of the digestive system (Review)

Most tumors of the digestive system, including esophageal, gastric, liver and colorectal cancer, are malignant tumors that are associated with rates of high morbidity and mortality. The lack of effective methods for early diagnosis is an important cause of poor prognosis for these malignancies. Circular RNAs (circRNAs) belong to a family of endogenous, covalently closed non‑coding RNAs that are characterized as having no 5' cap structures or 3' poly‑A tails. Shortly following discovery, circRNAs were considered to be a product of mis‑splicing and have no significant biological function. However, in recent years, accumulating evidence is demonstrating that they serve key roles in tumorigenesis and have the potential to serve as diagnostic markers. The present article summarizes the biogenesis and function of circRNAs and reviews their role in seven common types of tumor of the digestive system whilst exploring their potential as tumor markers and the significant roles they can serve in the digestive system, in addition to providing a referencing point for future studies of digestive system malignancies.

Circular RNA CircPRMT5 Accelerates Proliferation and Invasion of Papillary Thyroid Cancer Through Regulation of miR-30c/E2F3 Axis

Background

The role of circular RNA (circRNA) in papillary thyroid cancer (PTC) is largely unknown. This study aims to determine the function and mechanism of circPRMT5 in the regulation of PTC development.

Methods

PTC tissues and cell lines were used to determine circPRMT5 expression via quantitative real-time polymerase chain reaction. Small interfering RNA (siRNA) was utilized to knock down circPRMT5. Proliferation was analyzed through CCK8 and colony formation assays. Transwell assay was performed to determine cell migration and invasion. Luciferase assay and RIP assay were carried out to analyze the interaction between circPRMT5 and miR-30c.

Results

CircPRMT5 expression was upregulated in PTC tissues and cell lines. And circPRMT5 level was positively linked with advanced stage and lymph node metastasis. CircPRMT5 knockdown inhibited proliferation, migration and invasion while inducing apoptosis. CircPRMT5 worked as a competing endogenous RNA for miR-30c. By inhibiting miR-30c, circPRMT5 promoted the expression of E2F3.

Conclusion

Our findings demonstrate that circPRMT5 acts as an oncogenic circRNA to promote PTC progression via regulating miR-30c/E2F3 axis.