The Circular RNA hsa_circ_0001445 Regulates the Proliferation and Migration of Hepatocellular Carcinoma and May Serve as a Diagnostic Biomarker. Dis Markers. 2018;2018:3073467. [PMID: 29785229 PMCID: PMC5896272 DOI: 10.1155/2018/3073467]

Abnormally expressed circular RNAs as novel non-invasive biomarkers for hepatocellular carcinoma: A meta-analysis

BACKGROUND

Circular RNAs (circRNAs) are a newly discovered class of endogenous non-coding RNAs that may have roles in cancer genesis and development. In the recent literature, dysregulated circRNAs have been extensively investigated in hepatocellular carcinoma (HCC). Whether or not circRNAs are of clinical value for the management of HCC has not been characterized.

AIM

To meta-analyze the diagnostic and prognostic value of abnormally expressed circRNAs in HCC.

METHODS

Eligible studies were sourced from PubMed, EMBASE, and CNKI online databases. Data on patients’ clinical characteristics, including diagnostic efficacy and overall survival, were extracted. The diagnostic and prognostic parameters were respectively synthesized using the bivariate meta-analysis model and multivariate Cox hazard regression analysis based on Stata 12.0. The trim and fill method was adopted to assess the possible effects from publication bias.

RESULTS

A total of 21 eligible studies were included. The pooled sensitivity, specificity, and area under the curve of abnormally expressed circRNAs in distinguishing HCC from non-cancer controls were 0.78 (95%CI: 0.69–0.85), 0.80 (95%CI: 0.74–0.86), and 0.86, respectively. Survival analyses showed that the down-regulated circRNA expression signature correlated perfectly with HCC survival [hazard ratio (HR) = 0.42, 95%CI: 0.19–0.91, P = 0.028; I² = 92.7%, P = 0.000], whereas the HCC cases with high circRNA levels had significantly poorer prognoses than those of patients with low circRNA levels (HR = 2.22, 95%CI: 1.50–3.30, P = 0.000; I² = 91%, P = 0.000). Moreover, abnormally expressed circRNAs were intimately associated with tumor size, differentiation grade, microvascular invasion, metastasis, TNM stage, and serum alpha fetal protein level in patients with HCC. Stratified analysis based on sample type, control source, and expression status also yielded robust results.

CONCLUSION

Abnormally expressed circRNA signatures show immense potential as novel non-invasive biomarker(s) for HCC diagnosis and prognosis.

Hsa_circ_0028502 and hsa_circ_0076251 are potential novel biomarkers for hepatocellular carcinoma

Circular RNAs (circRNAs) have been increasingly revealed to be desirable biomarkers for some tumors, including hepatocellular carcinoma (HCC). Combined with our previous microarray screening results, we aimed to determine the hsa_circ_0028502 and hsa_circ_0076251 expression features in HCC, analyze the relationship between their expression level and clinical and pathological characteristics, and investigate their diagnostic and prognostic values. Our data demonstrated that the hsa_circ_0028502 and hsa_circ_0076251 levels were considerably lower in HCC tissues than in adjacent paracancerous tissues (P < .001). Further study revealed that hsa_circ_0028502 expression levels were related to tumor node metastasis (TNM) stage (P = .015) and that hsa_circ_0076251 expression levels were related to Barcelona Clinic Liver Cancer (BCLC) stage (P = .038), comorbidity with type 2 diabetes mellitus (P = .023) and the presence of serum HbsAg (P = .044). Furthermore, the degree of expression of both hsa_circ_0028502 and hsa_circ_0076251 increased from HCC to liver cirrhosis (LC) to chronic hepatitis (CH). The receiver operating characteristic (ROC) curve demonstrated that hsa_circ_0028502 and hsa_circ_0076251 could serve as fairly accurate markers to distinguish HCC tissues from CH tissues and LC tissues, as well as distinguishing LC tissues from CH tissues. Cox regression analysis showed that low expression of has_circ_0076251 was associated with unfavorable survival rates in HCC (HR = 0.46; 95% CI = 0.22‐0.98; P < .05). These findings implied that hsa_circ_0028502 and hsa_circ_0076251 were potentially valuable biomarkers for HCC diagnosis, whereas hsa_circ_0076251 could be used as a prognostic indicator for HCC.

Molecular mechanisms of circular RNAs, transforming growth factor-β, and long noncoding RNAs in hepatocellular carcinoma

At the heart of hepatocellular carcinoma (HCC) lies disruption of signaling pathways at the level of molecules, genes, and cells. Non‐coding RNAs (ncRNAs) have been implicated in the disease progression of HCC. For instance, dysregulated expression of circular RNAs (circRNAs) has been observed in patients with HCC. As such, these RNAs are potential therapeutic targets and diagnostic markers for HCC. Long non‐coding RNAs (lncRNAs), a type of ncRNA, have also been recognized to participate in the initiation and progression of HCC. Transforming growth factor‐beta (TGF‐β) is another element which is now recognized to play crucial roles in HCC. It has been implicated in many biological processes such as survival, immune surveillance, and cell proliferation. In HCC, TGF‐β promotes disease progression by two mechanisms: an intrinsic signaling pathway and the extrinsic pathway. Through these pathways, it modulates various microenvironment factors such as inflammatory mediators and fibroblasts. An interesting yet‐to‐be resolved concept is whether the HCC‐promoting role of TGF‐β pathways is limited to a subset of HCC patients or it is involved in the whole process of HCC development. This review summarizes recent advancements to highlight the roles of circRNAs, lncRNAs, and TGF‐β in HCC.

Noncoding RNAs in Extracellular Fluids as Cancer Biomarkers: The New Frontier of Liquid Biopsies

The last two decades of cancer research have been devoted in two directions: (1) understanding the mechanism of carcinogenesis for an effective treatment, and (2) improving cancer prevention and screening for early detection of the disease. This last aspect has been developed, especially for certain types of cancers, thanks also to the introduction of new concepts such as liquid biopsies and precision medicine. In this context, there is a growing interest in the application of alternative and noninvasive methodologies to search for cancer biomarkers. The new frontiers of the research lead to a search for RNA molecules circulating in body fluids. Searching for biomarkers in extracellular body fluids represents a better option for patients because they are easier to access, less painful, and potentially more economical. Moreover, the possibility for these types of samples to be taken repeatedly, allows a better monitoring of the disease progression or treatment efficacy for a better intervention and dynamic treatment of the patient, which is the fundamental basis of personalized medicine. RNA molecules, freely circulating in body fluids or packed in microvesicles, have all the characteristics of the ideal biomarkers owing to their high stability under storage and handling conditions and being able to be sampled several times for monitoring. Moreover, as demonstrated for many cancers, their plasma/serum levels mirror those in the primary tumor. There are a large variety of RNA species noncoding for proteins that could be used as cancer biomarkers in liquid biopsies. Among them, the most studied are microRNAs, but recently the attention of the researcher has been also directed towards Piwi-interacting RNAs, circular RNAs, and other small noncoding RNAs. Another class of RNA species, the long noncoding RNAs, is larger than microRNAs and represents a very versatile and promising group of molecules which, apart from their use as biomarkers, have also a possible therapeutic role. In this review, we will give an overview of the most common noncoding RNA species detectable in extracellular fluids and will provide an update concerning the situation of the research on these molecules as cancer biomarkers.

The role of circular RNA hsa_circ_0085616 in proliferation and migration of hepatocellular carcinoma cells

Background

CircRNAs involved in the development of many diseases have been recently identified. However, the possible role of circRNAs in human hepatocellular carcinoma (HCC) remains to be investigated.

Objective

This study aimed to identify the expression of hsa_circ_0085616 in different HCC cell lines and its function in HCC tumorigenesis.

Methods

The expression of hsa_circ_0085616 was first measured in 68 pairs of HCC tissues and matched normal adjacent tissues. Further analysis was performed in different HCC cell lines and human normal hepatic cell lines. Moreover, we down- or upregulated its expression by cell transfection in vitro. Cell proliferation, migration, invasion and apoptosis were measured, and proliferation-related signaling pathway proteins were also analyzed.

Results

We found that hsa_circ_0085616 was highly expressed in all HCC cell lines compared to the normal liver cell line. Upregulation or downregulation of hsa_circ_0085616 expression could strengthen or weaken the proliferative ability of HCC cells in vitro. Moreover, the protein levels of β-catenin, p-ERK, and p-AKT, which play important roles in the typical proliferation pathway, were also affected by the expression of hsa_circ_0085616.

Conclusion

Our study indicated that hsa_circ_0085616 might be a potential biomarker and a new therapeutic target for HCC.

Detection of serum long non-coding RNA UCA1 and circular RNAs for the diagnosis of bladder cancer and prediction of recurrence

Accumulating evidence indicates that long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) may be biomarkers for the diagnosis and prediction of recurrence in tumor patients because they play an important role in tumorigenesis and progression. In this study, the expression of lncRNA urothelial carcinoma-associated 1 (UCA1) and associated circFARSA, circSHKBP1, and circBANP was investigated in serum specimens from bladder cancer (BC) patients and healthy controls using real-time PCR. When comparing patients with BC to healthy controls, the expression of lncRNA UCA1, circFARSA, and circSHKBP1 was significantly increased. The area under the curve (AUC) of the lncRNA UCA1 and circSHKBP1 signature to distinguish BC patients from controls was 0.804. The diagnostic performance of this signature was more optimal for low volume tumors (AUC = 0.870). Moreover, we determined that the expression of circFARSA, circSHKBP1, and circBANP was higher for recurrent BC than for patients without recurrence. Receiver operating characteristic (ROC) analysis revealed that a combination of circFARSA and circBANP levels was able to discriminate the patients with tumor recurrence from those without, with an area under the ROC curve of 0.737. In conclusion, our results identified an lncRNA UCA1: circSHKBP1 panel and a circFARSA: circBANP panel for BC diagnosis and prognosis, respectively.

Hsa_circ_0003998 may be used as a new biomarker for the diagnosis and prognosis of hepatocellular carcinoma

Background

Circular RNAs (circRNAs) play important roles in the progression of cancers, but the precise role of circRNAs in the diagnosis and prognosis of hepatocellular carcinoma (HCC) remains to be clarified. The aim of the current study was to explore the diagnostic and prognostic values of hsa_circ_0003998 in HCC.

Methods

CircRNAs expression was measured using RNA-seq analysis from HCC tissues (n=6) (three cases with or without portal vein invasion). Hsa_circ_0003998 in 200 pairs of HCC and adjacent noncancerous tissues and HCC cell lines was examined using qRT-PCR and the clinicopathologic significance was determined. We also detected the plasma levels of hsa_circ_0003998 in HCC, hepatitis B patients and healthy controls. The clinical diagnosis and prognostic values were further determined using receiver operating characteristic (ROC) curve, Kaplan–Meier curve and Cox regression.

Results

Hsa_circ_0003998 was upregulated in HCC tissues (P<0.001) and HCC cell lines (HepG2, HuH7, MHCC97H) (P<0.001). In addition, upregulation of hsa_circ_0003998 level was associated with higher serum alpha-fetoprotien (AFP) level (P=0.003), larger tumor diameter (P=0.009), lower differentiation level (P=0.023) and microvascular invasion (P=0.028). The plasma level of hsa_circ_0003998 in HCC patients was significantly higher than those in hepatitis B patients (P<0.001) and healthy controls (P<0.001). Its level was significantly reduced after the operation (P<0.001). The area under the ROC curve (AUC) for distinguishing HCC from adjacent noncancerous tissues was 0.894 (95% CI=0.86–0.922, P<0.001), the sensitivity and specificity were 0.84 and 0.8, respectively. Comparing with hepatitis B patients and healthy controls, hsa_circ_0003998, respectively, had an AUC value of 0.833 (95% CI=0.763–0.889, P<0.001) and 0.892 (95% CI=0.831–0.937, P<0.001). Their sensitivity and specificity were 0.83, 0.7 and 0.8, 0.84, respectively. Moreover, the combination of hsa_circ_0003998 and AFP showed the highest AUC value of 0.947, the sensitivity and specificity were 0.88 and 0.92, respectively. The hsa_circ_0003998 (P=0.003) and AFP (P=0.008) levels were independent prognostic factors for HCC. The overall survival of HCC patients with high level of hsa_circ_0003998 was significantly poorer than those with low level (P=0.005).

Conclusion

Our findings suggest that hsa_circ_0003998 may be used as a novel potential biomarker for the diagnosis and prognosis of HCC patients.

Circular RNAs in hepatocellular carcinoma: Biomarkers, functions and mechanisms

Hepatocellular carcinoma (HCC), a leading cause of cancer-related death with high invasive and metastatic potential, has a low survival rate. To improve the survival and quality of life in HCC patients, it is urgently needed to explore novel biomarkers for early diagnosis and prognosis of HCC, as well as therapeutic strategies. Circular RNAs (circRNAs) are a class of highly conserved, stable and abundant non-coding RNAs (ncRNAs) that can regulate gene expression at transcriptional or post-transcriptional levels. Recently, some circRNAs are identified to be potential biomarkers for HCC diagnosis and prognosis. Furthermore, some circRNAs are found to play oncogenic or suppressive roles in HCC progression by regulating various biological processes, including cell proliferation, migration, invasion and metastasis, epithelial-mesenchymal transition (EMT), as well as apoptosis. In this review, we summarize recent findings of deregulated circRNAs, their functions and molecular mechanisms in HCC, and discuss their potential roles as diagnostic biomarkers, prognostic biomarkers, as well as therapeutic targets for HCC.

Diagnostic performance of circular RNAs in human cancers: A systematic review and meta-analysis

BACKGROUND

Recently, accumulating evidence have revealed that circular RNA (circRNA) was deregulated in multiple types of cancer, suggesting that circRNA might serve as a novel candidate biomarker of cancer diagnosis. However, inconsistent results have become an obstacle in applying circRNAs to clinical practice. The aim of this study is to evaluate diagnostic value of circRNAs among cancers.

METHODS

A literature search was systematically performed among PubMed, Sciencedirect, Cochrane Library, Web of Science, Wanfang, and Chinese National Knowledge Infrastructure databases up to February 15, 2019. The pooled sensitivity (SEN), specificity (SPE), positive likelihood ratios, negative likelihood ratios, diagnostic odds ratio, and area under the SROC curve (AUC) were applied to evaluate diagnostic performance of circRNAs.

RESULTS

In total, the study included 64 studies with single circRNA and 13 studies with combined circRNAs. Overall, the study presented that a single circRNA had moderate diagnostic value, with a SEN of 0.75, a SPE of 0.76, and an AUC of 0.82. The plasma circRNAs had higher diagnostic accuracy than tissue (AUC: 0.87, 95% confidence interval [CI]: 0.83-0.89 for plasma/serum subgroup; AUC: 0.79, 95% CI: 0.75-0.82 for tissue subgroup). Furthermore, the combined circRNAs had good diagnostic efficacy for GC, with a SEN of 0.89, a SPE of 0.94, and an AUC of 0.97, respectively.

CONCLUSION

This study confirmed that circRNAs may be candidate biomarkers for cancer diagnosis. In particular, diagnosis of combined circRNAs will be a new alternative applied to clinical research and practice for cancer.

Circular RNAs as novel regulators, biomarkers and potential therapies in fibrosis

Fibrosis is the excess deposition of extracellular matrix components which ultimately leads to the disruption of organ architecture and loss of function. Circular RNAs (circRNAs) are a newly discovered type of long noncoding RNAs with single-stranded covalently closed loops. It is known that circRNAs are novel regulators of gene expression via various ways, including miRNA sponge, protein sponge, regulation of transcription and post transcription. Recently, a growing body of evidence suggests that circular RNAs are also involved in tissue fibrosis in several organs. In this review, we summarized current studies of circular RNAs in fibrosis and hopefully aid in better understanding the molecular mechanism of fibrosis and provide a basis to explore new therapeutic targets of fibrosis.

CircRNA hsa_circ_0004585 as a potential biomarker for colorectal cancer

Objective: Circular RNAs (circRNAs) are involved in regulating of carcinogenesis of various cancer cells. However, the function of circRNAs in colorectal cancer (CRC) has remained largely unknown. This study investigated the characteristic expression of circRNAs in CRC and adjacent normal tissues, analyzed the miRNAs related to candidate circRNAs, and studied the correlation between circRNAs with clinical data of CRC. Methods: Human CircRNA microarray has been applied to screen the expressions of circRNAs of the CRC tissues and adjacent normal tissues. Quantitative real-time polymerase chain reaction (qRT-PCR) verified the candidate circRNAs in CRC tissue and patients' peripheral blood. The circRNA array data were analyzed by GeneSpring 13.0 (Agilent) software. The diseases, pathways and functional enrichment analysis of these genes were performed using the KEGG system. In addition, the circRNA-miRNA network was constructed based on the miRanda-3.3 software. Statistical analysis was performed with SPSS23.0, GraphPad Prism, and Sigmaplot software. Results: In total, 13,198 circRNAs were identified as distinct between CRC and adjacent normal tissues, including 6,697 upregulated and 6,501 downregulated genes. Based on scores, six of them were selected for further verification in CRC tissues and peripheral blood. The hsa_circ_0004585 expression was significantly upregulated both in CRC patients tissue and peripheral blood. Hsa_circ_0004585 was positively correlated with patient's tumor size, indicating the function of hsa_circ_0004585 in CRC carcinogenesis and metastasis. Conclusion: Hsa_circ_0004585 could be a potential biomarker for diagnosis of CRC.

Circular RNAs as potential biomarkers and therapeutics for cardiovascular disease

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

Systematic Review and Meta-Analysis of the Utility of Circular RNAs as Biomarkers of Hepatocellular Carcinoma

Emerging studies have reported circRNAs were dysregulated in HCC. However, the clinical value of these circRNAs remains to be clarified. Herein, we aimed to comprehensively explore their association with the diagnosis, prognosis, and clinicopathological characteristics of HCC. PubMed, EMBASE, Web of Science, and Cochrane Library databases were comprehensively searched for eligible studies up to October 30, 2018. The diagnostic effect was evaluated by the pooled sensitivity, specificity, and other indexes. The pooled hazard ratio (HR) for overall survival (OS) and recurrence free survival (RFS) was calculated to assess the prognostic value. Ten studies on diagnosis, 12 on prognosis, and 23 on clinicopathology were identified from the databases. A total of 11 upregulated and 11 downregulated circRNAs showed an association with clinicopathological features of HCC. For the diagnosis analyses, the pooled sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR) of circRNAs for HCC were 0.74 (95%CI: 0.65-0.82) and 0.76 (95%CI: 0.70-0.81), 3.1 (95%CI: 2.5-3.8), 0.34 (95%CI: 0.25-0.47), and 9 (95%CI: 6-14), respectively. The area under SROC curve (AUC) was 0.81 (95% CI: 0.78-0.84), indicating moderate diagnostic accuracy. In stratified analyses, the diagnostic performance of circRNAs varied based on the source of control and specimen type. For the prognosis analyses, increased expression of upregulated circRNAs was associated with worse OS (HR: 3.67, 95%: 2.07-6.48), while high expression of downregulated circRNAs was associated with better OS (HR: 0.38, 95%: 0.30-0.48). In conclusion, this study reveals that circRNAs may serve as promising diagnostic and prognostic biomarkers for HCC. However, further investigations are still required to explore the clinical value of circRNAs.

Circular RNAs in Cancer: emerging functions in hallmarks, stemness, resistance and roles as potential biomarkers

Circular RNAs (circRNAs) are a class of RNA molecules with closed loops and high stability. CircRNAs are abundantly expressed in eukaryotic organisms and exhibit both location- and step-specificity. In recent years, circRNAs are attracting considerable research attention attributed to their possible contributions to gene regulation through a variety of actions, including sponging microRNAs, interacting with RNA-binding proteins, regulating transcription and splicing, and protein translation. Growing evidence has revealed that circRNAs play critical roles in the development and progression of diseases, especially in cancers. Without doubt, expanding our understanding of circRNAs will enrich knowledge of cancer and provide new opportunities for cancer therapy. In this review, we provide an overview of the characteristics, functions and functional mechanisms of circRNAs. In particular, we summarize current knowledge regarding the functions of circRNAs in the hallmarks, stemness, resistance of cancer, as well as the possibility of circRNAs as biomarkers in cancer.

circSMARCA5 Functions as a Diagnostic and Prognostic Biomarker for Gastric Cancer

Background

Circular RNAs have been implicated in various malignancies and can function as potential biomarkers for cancers. Reportedly, circSMARCA5 was downregulated in hepatocellular carcinoma and glioblastoma multiforme, but upregulated in prostate cancer. The functional roles and clinical significance of circSMARCA5 still remain unknown in the context of gastric cancer (GC).

Methods

Expression levels of circSMARCA5 were detected by qRT-PCR. Clinical data including patient basic information, clinicopathological features, and survival data were obtained. The Kaplan-Meier methods, multivariate Cox regression models, and the receiver operating characteristic curve were used to assess the clinical significance of circSMARCA5 in GC. Cell proliferation assays and transwell assays were performed to elucidate the functional roles of circSMARCA5 in GC.

Results

The circSMARCA5 level was decreased in GC tissues and cell lines. The low expression level of circSMARCA5 was correlated to poorer overall survival and disease-free survival. Low circSMARCA5 expression was revealed as an independent unfavorable predictive factor for GC. The results indicated that circSMARCA5 had a moderate ability for discrimination between GC patients and controls with an area under the curve of 0.806. Upregulation of circSMARCA5 dampened the proliferation, migration, and invasion of GC cells, whereas circSMARCA5 knockdown promoted GC progression.

Discussion

Our results demonstrated that circSMARCA5 was decreased and exerted tumor-suppressive effects in GC. circSMARCA5 can function as a potential biomarker for GC prognosis and diagnosis.

Prognostic and diagnostic significance of circRNAs expression in hepatocellular carcinoma patients: A meta-analysis

Circular RNAs (circRNAs) as novel biomarkers are widely investigated in various cancers. The aim of our study was to reveal the clinicopathological, prognostic, and diagnostic features of circRNAs in human hepatocellular carcinoma (HCC). A systematical search was conducted on PubMed, Scopus, Web of Science (WOS), EMBASE, and the Cochrane Library databases. Eligible studies reporting on the association among circRNAs and clinicopathological, prognostic, diagnostic values of HCC patients were included. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were utilized to assess clinicopathological parameters, sensitivity, and specificity, and hazard ratios (HRs) were to evaluate overall survival (OS). 17 eligible studies which included 7 for clinicopathological features, 10 for prognosis, and 8 for diagnosis were in our study. As for clinicopathological parameters, high expression of oncogenic circRNAs had a significant association with poor clinicopathological features and tumor-suppressor circRNAs proved the contrary. In terms of the prognostic values, oncogenic circRNAs had a negative influence on overall survival (OS: HR = 3.39, 95%Cl: 2.59-4.19), and high expression of tumor-suppressor circRNAs was relevant to improved survival outcomes (OS: HR = 0.46, 95%Cl: 0.37-0.56). The pooled diagnostic outcomes indicated an area under the curve (AUC) of 0.84, with sensitivity of 82% and specificity of 72% in discriminating HCC from controls. Our study indicates that circRNAs may be important biomarkers for prognostic and diagnostic values of HCC.

The circulating transcriptome as a source of cancer liquid biopsy biomarkers

Non-invasive biomarkers or liquid biopsies have the potential to revolutionise cancer patient management as repeated sampling allows real-time monitoring of disease progression and response to treatment. This allows for earlier intervention and dynamic treatment management; both cornerstones of personalised medicine. The circulating transcriptome represents a rich source of potential cancer biomarkers that includes many classes of RNA, both coding and non-coding, that are only now beginning to be explored. In particular the increasing power and availability of RNAseq techniques have pushed studies beyond circulating miRNAs, to other classes of RNA including mRNA, snRNA, snoRNA, piRNA, YRNA, lncRNA and circRNA. In this review we focus on the emerging potential for these different classes of RNA as cancer biomarkers, and in particular the barriers and limitations that remain to be overcome if these molecules are to become part of routine clinical practice.

Differential circRNA expression profiles in latent human cytomegalovirus infection and validation using clinical samples

Human cytomegalovirus (HCMV) is an opportunistic prototypic beta-herpesvirus that can cause severe and even fatal diseases in immune-naive newborns and immunocompromised adults. Host-virus interactions occurring at the transcriptional and posttranscriptional levels are critical for establishing an HCMV latent or lytic infection, but the mechanisms remain poorly understood. Herein, we investigated the expression of circRNAs in human leukemia monocytes (THP-1 cells) latently infected with HCMV and explored the diagnostic value of circRNAs in children with HCMV infection. A total of 2,110 and 1,912 circRNAs were identified in mock-infected and HCMV latent-infected THP-1 cells, respectively. Of these, we identified 1,421 differently expressed circRNAs, of which 650 were upregulated and 771 were downregulated. The host genes corresponding to the differentially expressed circRNAs were mainly involved in the regulation of host cell secretion pathways, cell cycle, and cell apoptosis. The differentially expressed circRNAs had binding sites for microRNAs, suggesting an important role in the mechanism of HCMV latent infection. Furthermore, a clinical analysis showed that the expression levels of hsa_circ_0001445 and hsa_circ_0001206 were statistically significantly different in HCMV-infected patients vs. normal controls, suggesting that these circRNAs could potentially serve as biomarkers of HCMV-infection.

Novel biomarkers in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related deaths and the fifth most common cancer worldwide. Most of these patients are seen with advanced disease at the time of presentation. In spite of its high prevalence, there are not many therapeutic options available for patients with advanced-stage HCC. There is an urgent need for improving early detection and prognostication of patients with HCC. In addition, the development of new therapies targeting specific pathways involved in the pathogenesis of HCC should be a major goal for future research, with the objective of improving outcomes of patients with HCC. Biomarkers represent a relatively easy and noninvasive way to detect and estimate disease prognosis. In spite of the numerous efforts to find molecules as possible biomarkers, there is not a single ideal marker in HCC. Many new findings have shown promising results both in diagnosing and treating HCC. In this review, we summarized the most recent and relevant biomarkers in HCC.

Contribution of dysregulated circRNA_100876 to proliferation and metastasis of esophageal squamous cell carcinoma

Purpose

Accumulating evidence demonstrates that circRNAs regulate diverse cellular processes and cancer progression. However, it remains unclear whether circRNAs play any functional role in esophageal squamous cell carcinoma (ESCC).

Materials and methods

The significance of circRNA_100876 in ESCC was analyzed by studying circRNA_100876 expression in ESCC tissues and the association between circRNA_100876 expression and clinicopathologic parameters. The biological effects of circRNA_100876 knockdown by lentivirus-mediated siRNAs on cell proliferation, cell cycle, apoptosis, and migration were investigated in vitro and in vivo.

Results

CircRNA_100876 expression was upregulated (P<0.05) and was negatively correlated with survival outcome (P<0.05) in ESCC. Inhibition of proliferation, migration, invasion, and epithelial–mesenchymal transition progression was confirmed after circRNA_100876 depletion.

Conclusion

Dysregulation of circRNA_100876 expression leads to poor prognosis in ESCC by accelerating cell proliferation and metastasis.

Emerging Roles of Circular RNAs in Osteosarcoma

Osteosarcoma (OS) is a primary malignant bone tumor in early adolescence with high metastasis and death rates. Although the combination of polychemotherapy and surgical excision increased the survival rates up to 60%, the prognosis remains poor for most patients with metastatic or recurrent osteosarcoma. However, the exact pathogenic mechanism and pivotal elements regulating tumor invasion and metastasis are largely unknown. Circular RNAs (circRNAs) are novel endogenous non-coding RNA (ncRNA) molecules that generate the cyclic structure from back splicing. An increasing number of studies show that circRNAs can regulate transcriptional or posttranscriptional gene expression by acting as microRNA (miRNA) sponges and are involved in regulation of many important biological processes. The deregulation of some circRNAs was demonstrated in osteosarcoma. Furthermore, some circRNAs were identified to play essential roles in osteosarcoma occurrence, invasion, and metastasis. This review summarizes the regulatory effect of circRNAs in the occurrence and development of osteosarcoma, concentrating on deregulation, regulatory mechanisms, and functions of circRNAs and their potential value as biomarkers and therapy.

Circular RNAs: Characteristics, Function and Clinical Significance in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. HCC patients are commonly diagnosed at an advanced stage, for which highly effective therapies are limited. Moreover, the five-year survival rate of HCC patients remains poor due to high frequency of tumor metastasis and recurrence. These challenges give rise to the emergent need to discover promising biomarkers for HCC diagnosis and identify novel targets for HCC therapy. Circular RNAs (circRNAs), a class of long-overlook non-coding RNA, have been revealed as multi-functional RNAs in recent years. Growing evidence indicates that circRNA expression alterations have a broad impact in biological characteristics of HCC. Most of these circRNAs regulate HCC progression by acting as miRNA sponges, suggesting that circRNAs may function as promising diagnostic biomarkers and ideal therapeutic targets for HCC. In this review, we summarize the current progress in studying the functional role of circRNAs in HCC pathogenesis and present their potential values as diagnostic biomarkers and therapeutic targets. In-depth investigations on the function and mechanism of circRNAs in HCC will enrich our knowledge of HCC pathogenesis and contribute to the development of effective diagnostic biomarkers and therapeutic targets for HCC.