Knockdown of circular RNA UBAP2 inhibits the malignant behaviours of esophageal squamous cell carcinoma by microRNA-422a/Rab10 axis

Circ_FNDC3B Promotes Cell Proliferation and Metastasis in Esophageal Squamous Cell Carcinoma via Regulating MAPK1 by Binding to miR-136-5p

A handful of circular RNAs (circRNAs) associated with cancer progression have been indicated in esophageal squamous cell carcinoma (ESCC). The current study aimed to investigate the functional mechanism of circular RNA Fibronectin type III domain containing 3B (circ_FNDC3B) in ESCC. Circ_FNDC3B, FNDC3B, microRNA-136-5p (miR-136-5p) and mitogen-activated protein kinase 1 (MAPK1) were examined via the quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was evaluated by Cell Counting Kit-8 (CCK-8) and colony formation assays. Transwell assay was performed to measure cell migration and invasion. Protein analysis was implemented by western blot. Cell apoptosis was assessed via flow cytometry. Target interaction was affirmed using dual-luciferase reporter assay. The function analysis of circ_FNDC3B in vivo was explored by xenograft models. The upregulation of circ_FNDC3B was detected in ESCC tissues and cells. Functionally, ESCC cell proliferation and metastasis were repressed but apoptosis was promoted by circ_FNDC3B knockdown. Besides, circ_FNDC3B silence inhibited ESCC progression through MAPK1 downregulation. Further target analysis identified miR-136-5p as a target of circ_FNDC3B and an upstream control of MAPK1. Additionally, the regulation of si-circ_FNDC3B in ESCC was also dependent on targeting miR-136-5p. Moreover, circ_FNDC3B targeted miR-136-5p to affect MAPK1 level. Tumorigenesis in vivo was also suppressed by downregulating circ_FNDC3B to regulate miR-136-5p/MAPK1 axis. Circ_FNDC3B downregulation impeded the development of ESCC via the mediation of miR-136-5p/MAPK1 axis. This report afforded a novel insight into the functional mechanism of circ_FNDC3B in ESCC.

Circ_0003945: an emerging biomarker and therapeutic target for human diseases

Due to the rapid development of RNA sequencing techniques, a circular non-coding RNA (ncRNA) known as circular RNAs (circRNAs) has gradually come into focus. As a distinguished member of the circRNA family, circ_0003945 has garnered attention for its aberrant expression and biochemical functions in human diseases. Subsequent studies have revealed that circ_0003945 could regulate tumor cells proliferation, migration, invasion, apoptosis, autophagy, angiogenesis, drug resistance, and radio resistance through the molecular mechanism of competitive endogenous RNA (ceRNA) during tumorigenesis. The expression of circ_0003945 is frequently associated with some clinical parameters and implies a poorer prognosis in the majority of cancers. In non-malignant conditions, circ_0003945 also holds considerable importance in diseases pathogenesis. This review aims to recapitulate molecular mechanism of circ_0003945 and elucidates its potential as a diagnostic and therapeutic target in neoplasms and other diseases.

MicroRNAs: A novel signature in the metastasis of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a malignant epithelial tumor, characterized by squamous cell differentiation, it is the sixth leading cause of cancer-related deaths globally. The increased mortality rate of ESCC patients is predominantly due to the advanced stage of the disease when discovered, coupled with higher risk of metastasis, which is an exceedingly malignant characteristic of cancer, frequently leading to a high mortality rate. Unfortunately, there is currently no specific and effective marker to predict and treat metastasis in ESCC. MicroRNAs (miRNAs) are a class of small non-coding RNA molecules, approximately 22 nucleotides in length. miRNAs are vital in modulating gene expression and serve pivotal regulatory roles in the occurrence, progression, and prognosis of cancer. Here, we have examined the literature to highlight the intimate correlations between miRNAs and ESCC metastasis, and show that ESCC metastasis is predominantly regulated or regulated by genetic and epigenetic factors. This review proposes a potential role for miRNAs as diagnostic and therapeutic biomarkers for metastasis in ESCC metastasis, with the ultimate aim of reducing the mortality rate among patients with ESCC.

Unveiling the prominent roles of circular RNAs ubiquitin binding associated protein 2 in cancers

Circular RNAs (circRNAs), a novel type of covalently closed non-coding RNAs, are widely expressed in eukaryotes and viruses. Accumulating evidence has shown that circRNAs play key roles in the pathophysiological changes process of human diseases and can affect cancer development and progression through regulating target genes expression, linear RNA transcription and protein generation. Recent studies had found that circRNA-UBAP2 (ubiquitin binding associated protein 2) was aberrantly expressed in various human tumors and could affect tumor cells proliferation, migration, invasion, cell cycle, anti-apoptosis, radioresistance, chemoresistance and other malignant biological behavioral progress. Mechanistic studies further revealed that circUBAP2 could affect the occurrence and development of human tumors through multiple different molecular regulatory pathways in vivo and in vitro. In addition, the abnormal expression of circUBAP2 was significantly correlated with the clinicopathological characteristics of malignant tumors and had potential value as biomarkers for the diagnosis and prognosis evaluation of cancer patients, which deserved further study. This review had summarized and discussed the oncogenic roles and clinical performances of circUBAP2 in various human malignancies with a focus on biological functions and molecular mechanisms, which could help to elevate the understanding to the roles of circRNAs and continue subsequent studies on circUBAP2.

Circular RNAs: pivotal role in the leukemogenesis and novel indicators for the diagnosis and prognosis of acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive hematological malignancy and affected patients have poor overall survival (OS) rates. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) with a unique loop structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been identified exhibiting either up-regulation or down-regulation in AML patients compared with healthy controls. Recent studies have reported that circRNAs regulate leukemia cell proliferation, stemness, and apoptosis, both positively and negatively. Additionally, circRNAs could be promising biomarkers and therapeutic targets in AML. In this study, we present a comprehensive review of the regulatory roles and potentials of a number of dysregulated circRNAs in AML.

The circRNA circADAMTS6 promotes progression of ESCC and correlates with prognosis

Circular RNAs (circRNAs) are a type of noncoding RNA, which play a vital role in the occurrence and development of esophageal squamous cell carcinoma (ESCC). While the role of novel circADAMTS6 in ESCC remains unknown. We assessed circADAMTS6 expression in ESCC tissues and cells, and the relationship between circADAMTS6 expression and overall survival of ESCC patients. Functional experiments in vitro and xenograft in vivo assay were applied to explore the functions and mechanisms of circADAMTS6 in ESCC. Results found that up-regulation of circADAMTS6 was associated with poor overall survival and may acted as an independent risk factor for ESCC prognosis. Knockdown of circADAMTS6 significantly inhibited the proliferation, migration and invasion of ESCC cells and growth of xenograft tumors in vivo. Induced AGR2 expression was able to rescue the loss of function induced by si-circADAMTS6 in KYSE150 cell. CircADAMTS6 may acts as oncogene by activating AGR2 and the Hippo signaling pathway coactivator YAP in ESCC.

Current advances and future perspectives on the functional roles and clinical implications of circular RNAs in esophageal squamous cell carcinoma: more influential than expected

Esophageal squamous cell carcinoma (ESCC) is one of the most aggressive gastrointestinal cancers with high incidence and mortality. Therefore, it is necessary to identify novel sensitive and specific biomarkers for ESCC detection and treatment. Circular RNAs (circRNAs) are a type of noncoding RNAs featured by their covalently closed circular structure. This special structure makes circRNAs more stable in mammalian cells, coupled with their great abundance and tissue specificity, suggesting circRNAs may present enormous potential to be explored as valuable prognostic and diagnostic biomarkers for tumor. Mounting studies verified the critical roles of circRNAs in regulating ESCC cells malignant behaviors. Here, we summarized the current progresses in a handful of aberrantly expressed circRNAs, and elucidated their biological function and clinical significance in ESCC, and introduced a series of databases for circRNA research. With the improved advancement in high-throughput sequencing and bioinformatics technique, new frontiers of circRNAs will pave the path for the development of precision treatment in ESCC.

Circular RNAs With Efficacy in Preclinical In Vitro and In Vivo Models of Esophageal Squamous Cell Carcinoma

Esophageal cancer is associated with a dismal prognosis. The armamentarium of approved drugs is focused on chemotherapy with modest therapeutic benefit. Recently, checkpoint inhibitory monoclonal antibody Pembrolizumab was approved. In order to identify new targets and modalities for the treatment of esophagus squamous cell carcinoma (ESCC) we searched the literature for circRNAs involved in the pathogenesis of ESCC. We identified two down-regulated and 17 up-regulated circRNAs as well as a synthetic circRNA with efficacy in preclinical in vivo systems. Down-regulated circRNAs sponge microRNAs directed against tumor suppressor genes. Up-regulated circRNAs sponge microRNAs directed against mRNAs, which encode proteins with pro-tumoral functions. We discuss issues such as reconstitution of down-regulated circRNAs and inhibition of up-regulated circRNAs with short interfering RNA (siRNA)- related entities. Also, we address druggability issues of the identified targets.

Role of circular RNAs in gastrointestinal tumors and drug resistance

The incidence of gastrointestinal cancers has increased significantly over the past decade and gastrointestinal malignancies now rank among the leading causes of mortality globally. Although newer therapeutic strategies such as targeted therapies have greatly improved patient outcomes, their clinical success is limited by drug resistance, treatment failure and recurrence of metastatic disease. Therefore, there is an urgent need for further research identifying accurate and reliable biomarkers for precise treatment strategies. Circular RNAs (circRNAs) exhibit a covalently closed structure, high stability and biological conservation, and their expression is associated with the occurrence and development of gastrointestinal tumors. Moreover, circRNAs may significantly influence drug resistance of gastrointestinal cancers. In this article, we review the role of circRNAs in the occurrence and development of gastrointestinal cancer, their association with drug resistance, and potential application for early diagnosis, treatment and prognosis in gastrointestinal malignancies. Furthermore, we summarize characteristics of circRNA, including mechanism of formation and biological effects via mRNA sponging, chromatin replication, gene regulation, translational modification, signal transduction, and damage repair. Finally, we discuss whether circRNA-related noninvasive testing may be clinically provided in the future. This review provides new insights for the future development of diagnostics and therapeutics based on circRNAs in gastrointestinal tumors.

Dissecting the Role of Circular RNAs in Sarcomas with Emphasis on Osteosarcomas

Circular RNAs (circRNAs) are single-stranded RNAs generated from exons back-splicing from a single pre-mRNA, forming covalently closed loop structures which lack 5'-3'-polarity or polyadenylated tail. Ongoing research depicts that circRNAs play a pivotal role in tumorigenesis, tumor progression, metastatic potential and chemoresistance by regulating transcription, microRNA (miRNA) sponging, RNA-binding protein interactions, alternative splicing and to a lesser degree, protein coding. Sarcomas are rare malignant tumors stemming from mesenchymal cells. Due to their clinically insidious onset, they often present at advanced stage and their treatment may require aggressive chemotherapeutic or surgical options. This review is mainly focused on the regulatory functions of circRNAs on osteosarcoma progression and their potential role as biomarkers, an area which has prompted lately extensive research. The attributed oncogenic role of circRNAs on other mesenchymal tumors such as Kaposi Sarcoma (KS), Rhabdomyosarcoma (RMS) or Gastrointestinal Stromal Tumors (GISTs) is also described. The involvement of circRNAs on sarcoma oncogenesis and relevant emerging diagnostic, prognostic and therapeutic applications are expected to gain more research interest in the future.

Biological and clinical implications of metastasis-associated circular RNAs in oesophageal squamous cell carcinoma

Oesophageal squamous cell carcinoma (OSCC) is a prevalent malignancy with high morbidity and mortality as a result of early metastasis and poor prognosis. Metastasis is a multistep process, involving various signalling pathways. Circular RNAs (circRNAs) are a class of covalently closed noncoding RNAs, the aberrant expression of which is reported to be involved in several biological events, including cell transformation, proliferation, migration, invasion, apoptosis and metastasis. Several studies have reported interactions between circRNAs and metastasis-associated signalling pathways. The abundance, stability and highly specific expression of candidate circRNAs make them potential biomarkers and therapeutic targets in OSCC. In this review article, we comprehensively describe metastasis-related circRNAs and their interactions with epithelial-mesenchymal transition-associated molecules. We also describe the molecular mechanisms and clinical relevance of circRNAs in OSCC progression and metastasis.

Emerging roles of circUBAP2 targeting miR-370-3p in proliferation, apoptosis, and invasion of papillary thyroid cancer cells

Circular RNAs (circRNAs) have been documented to be aberrantly expressed in many types of malignancies and involved in cancer progression. However, their role in thyroid cancer (TC) remains largely unknown. Our study aimed to explore the role and mechanism of circUBAP2 in TC. The differentially expressed circRNAs in TC tissues were identified using GSE18105 from gene expression omnibus (GEO) database. CircUBAP2 and miR-370-3p expression was analyzed using qRT-PCR. The stability of circUBAP2 was confirmed by actinomycin D and RNase R. The subcellular localization of circUBAP2 was detected using cell fractionation assay. Cell proliferation, apoptosis, and invasion were evaluated using MTT, flow cytometry analysis, and Transwell invasion assay, respectively. The interaction between circUBAP2 and miR-370-3p was predicted using bioinformatics analysis and validated by luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation. CircUBAP2 was upregulated and miR-370-3p was downregulated in TC tissues and cells. CircUBAP2 was highly stable, resistant to RNase R digestion, and predominantly localized in the cytoplasm. CircUBAP2 knockdown inhibited cell proliferation and invasion and triggered apoptosis in TC cells. Bioinformatics analysis showed that circUBAP2 contained putative binding sites of miR-370-3p. CircUBAP2 acted as a sponge to inhibit miR-370-3p expression. Mechanistically, miR-370-3p inhibition abolished the effects of circUBAP2 on proliferation, apoptosis, and invasion in TC cells. Taken together, CircUBAP2 knockdown impeded the proliferation and invasion and induced apoptosis in TC cells via sponging miR-370-3p.

CircRNA UBAP2 serves as a sponge of miR-1294 to increase tumorigenesis in hepatocellular carcinoma through regulating c-Myc expression

Circular RNAs (circRNAs) are a class of regulatory RNAs with complex roles in healthy and diseased tissues. However, the oncogenic role of circRNAs in hepatocellular carcinoma (HCC) remains poorly understood, including the mechanisms by which the circular ubiquitin binding associated protein 2 (circUBAP2) contributes to tumorigenesis. We analyzed the expression of circUBAP2 in 20 paired samples of HCC and healthy tissue as well as in seven HCC cell lines via quantitative real-time polymerase chain reaction (qRT-PCR). Functional experiments, such as CCK8 viability assays, colony formation assays, wound healing, transwell assays, and flow cytometry, were conducted to assess the effects of circUBAP2 in vitro. To further elucidate the mechanisms by which circUBAP2 acts, we conducted dual-luciferase assays, western blots, RNA pull-down assays, and rescue experiments. CircUBAP2 was highly upregulated in most HCC tissues and was associated with poor prognosis. HCC patients with high circUBAP2 expression had greater vascular invasion and worse differentiation. Functionally, circUBAP2 overexpression enhanced HCC cell proliferation, migration, and invasion and inhibited apoptosis. Furthermore, we found that circUBAP2 upregulated c-Myc expression by sponging miR-1294, thus contributing to hepatocarcinogenesis. Inhibiting circUBAP2 expression in HCC attenuated the oncogenic effects of c-Myc. These findings suggest that circUBAP2 promotes HCC growth and metastasis. CircUBAP2 may have value as an independent prognostic biomarker or as a new target for the treatment of HCC.

Oncogenic circDHTKD1 promotes tumor growth and metastasis of oral squamous cell carcinoma in vitro and in vivo via upregulating miR-326-mediated GAB1

Circular RNAs (circRNAs) have been extensively elucidated with regard to their significant implications in oral squamous cell carcinoma (OSCC). This study performed the functional investigation of circRNA dehydrogenase E1 and transketolase domain containing 1 (circDHTKD1) in OSCC. RNA expression levels of different molecules were measured via quantitative real-time polymerase chain reaction (qRT-PCR). Cellular behaviors were detected by 3-(4, 5-dimethylthiazol-2-y1)-2,5-diphenyl tetrazolium bromide (MTT) for cell viability, colony formation assay for clonal capacity, flow cytometry for cell apoptosis, wound healing assay for migration, and transwell assay for migration/invasion. Western blot was used for analyzing protein expression. RNA pull-down and dual-luciferase reporter assays were applied to assess the binding between targets. A xenograft tumor model was established in nude mice for in vivo experiments. Our expression analysis revealed that circDHTKD1 was upregulated in OSCC tissues and cells. circDHTKD1 knockdown was shown to impede OSCC cell growth and metastasis but motivate apoptosis. Additionally, circDHTKD1 served as a microRNA-326 (miR-326) sponge and the function of circDHTKD1 was achieved by sponging miR-326 in OSCC cells. Also, miR-326 inhibited OSCC development via targeting GRB2-associated-binding protein 1 (GAB1). circDHTKD1 could sponge miR-326 to alter GAB1 expression. Furthermore, circDHTKD1 contributed to OSCC progression in vivo via the miR-326/GAB1 axis. These data disclosed a specific circDHTKD1/miR-326/GAB1 signal axis in governing the malignant progression of OSCC, showing the considerable possibility of circDHTKD1 as a predictive and therapeutic target for clinical diagnosis and treatment of OSCC.

Circular RNA UBAP2 promotes the proliferation of prostate cancer cells via the miR-1244/MAP3K2 axis

Prostate cancer (PCa) is a common male malignant disease with a high incidence, which can seriously affect the quality of life of patients. The survival rate of patients with PCa has improved to 98.6%; however, new insights for the molecular mechanism are still urgently required. Circular RNA (circ)UBAP2 is a tumor-associated circRNA that has been demonstrated to promote the progression of various types of cancer. CircUBAP2 has been demonstrated to be significantly upregulated in PCa, but its role in the progression of PCa remains unclear. The present study aimed to provide an improved understanding of the regulatory mechanism of circUBAP2 in PCa. circUBAP2 expression was identified to be upregulated in four PCa cell lines and clinical tissues by using reverse transcription-quantitative PCR analysis. Binding sites analysis and luciferase reporter gene assay indicated that the microRNA(miR)-1244/MAP3K2 axis was the target of circUBAP2. Gain-of-function assays revealed that circUBAP2 promoted the proliferation of PCa cells by sponging miR-1244 and promoting the MAP3K2 axis. The present findings may be essential for providing new strategies in the diagnosis and targeted therapy of PCa.

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.

circUBAP2 regulates osteosarcoma progression via the miR‑204‑3p/HMGA2 axis

Circular RNA (circRNA/circ)-ubiquitin associated protein 2 (UBAP2), a newly recognized circRNA, serves a functional role in several types of tumor, including ovarian cancer, colorectal cancer and osteosarcoma. However, the precise roles and molecular mechanism under-lying circUBAP2 in osteosarcoma (OS) are not completely understood. In the present study, the expression levels of circUBAP2, microRNA (miR)-204-3p and (HMGA2) were evaluated via reverse transcription-quantitative PCR in OS tissues and cells. OS cell proliferation, migration, invasion and apoptosis were assessed by performing Cell Counting Kit-8, Transwell and flow cytometry assays, respectively. HMGA2 protein expression levels were determined via western blot-ting. Dual-luciferase reporter assays were performed to verify the interaction between circUBAP2 and miR-204-3p, and between miR-204-3p and HMGA2. An RNA immunoprecipitation (RIP) assay was conducted to confirm the interaction between circUBAP2 and miR-204-3p. The results demonstrated that circUBAP2 expression was significantly upregulated in OS tissues and cell lines compared with para-cancerous tissues and hFOB1.19 cells, respectively. In addition, high circUBAP2 expression levels in patients with OS were associated with a lower survival rate compared with lower expression levels in patients with OS. The functional assays revealed that circUBAP2 knockdown significantly inhibited OS cell proliferation, migration and invasion, but increased OS cell apoptosis compared with the small interfering RNA-negative control (si-NC) group. The dual-luciferase reporter and RIP assay results confirmed that circUBAP2 bound to miR-204-3p. Moreover, miR-204-3p expression was significantly downregulated in OS tissues compared with paracancerous tissues, and miR-204-3p expression was negatively correlated with circUBAP2 expression in OS tissues. Collectively, the results demonstrated that miR-204-3p was associated with circUBAP2 knockdown-mediated inhibition of OS cell malignant behavior. Moreover, miR-204-3p was also identified as one of the direct targets of HMGA2. Collectively, the results indicated that compared with the si-NC group, circUBAP2 knockdown significantly inhibited OS cell malignant behavior by binding to miR-204-3p, which subsequently regulated HMGA2 expression. Therefore, the present study demonstrated that circUBAP2 expression was upregulated in OS, and circUBAP2 regulated OS cell malignant behavior via the miR-204-3p/HMGA2 axis.

Decreased circUBAP2 Expression Is Associated with Preeclampsia by Limiting Trophoblast Cell Proliferation and Migration

Preeclampsia (PE) is a common obstetric disease and a major cause of maternal, newborn, and fetal death. This condition is a multisystem disorder characterized by hypertension, proteinuria, and involvement of the kidney, liver, and nervous system. It is generally believed that the placenta is the main cause of PE. circRNAs are a special class of noncoding RNAs that can form covalently closed continuous ring structures with tissue-specific conservation, and they have been reported to play a wide range of regulatory functions in various diseases, including PE. In this study, we reported a novel circUBAP2 (hsa_circ_0003496) and found that it was downregulated in placental tissues from patients with PE compared to healthy controls. After knocking down circUBAP2 in trophoblast cells, we found that cell proliferation and migration were significantly suppressed. In addition, preliminary mechanistic studies showed that circUBAP2 can sponge miR-1244, and FOXM1 was identified as a target gene for miR-1244. Cotransfection of si-circUBAP2 and a miR-1244 inhibitor partially reversed the suppressive effect induced by circUBAP2 depletion on proliferation and migration. In conclusion, the circUBAP2/miR-1244/FOXM1 axis might be a promising molecular marker for the diagnosis and treatment of PE.

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.

Circular RNAs and esophageal cancer

As a new kind of RNA, circular RNA (circRNA) is a endogenous non-coding RNA with circular structure, which has the characteristics of universality, stability, conservatism and specificity. CircRNA can specifically bind to microRNAs (miRNAs) in the form of competitive endogenous RNA, thus directly or indirectly regulating the expression of related genes. In addition to the role of sponge, circRNA also regulates parental gene expression, transcriptional translation and protein modification; and it can be used as a biomarker to develop potential diagnosis and treatment methods and evaluate prognosis. Due to changes in dietary habits and genetic factors, the morbidity and mortality of esophageal cancer (EC) in the world are still high, and are prone to early metastasis. Although the diagnosis and treatment techniques have been improved in recent years, the early diagnosis of EC is not common, and the 5-year survival rate of patients is still very low. This article reviews the function and significance of circRNA and discusses the research progress of circRNA as biomarkers in EC.

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.

Role of non-coding RNAs in esophageal carcinoma

In recent years, the research on the role of non-coding RNAs (ncRNAs) in tumors has received more and more attention. Although research on the role of ncRNAs in the early diagnosis, disease monitoring, treatment guidance, and prognosis prediction of esophageal carcinoma has been gradually carried out, there are still many problems that need to be addressed. In the current paper, I review the progress in the research of ncRNAs in esophageal carcinoma, with an aim to help provide new strategies for the prevention and treatment of esophageal carcinoma.