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

The expression of circRNAs as a promising biomarker in the diagnosis and prognosis of human cancers: a systematic review and meta-analysis

Background

CircRNAs, a type of non-coding RNAs with special loop structure, of which the aberrant expression is closely related to tumor growth, proliferation, metastasis and recurrence. It remains unclear whether they have the potential to be biomarkers for diagnosis and prognosis of cancers. The study aims to clarify the relationship of circRNAs expression with cancers diagnosis and prognosis.

Materials and Methods

Sensitivity, specificity, area under curve (AUC) and receiver operating characteristic curve (ROC) were calculated to evaluate the diagnostic efficacy; Hazard ratio (HR) of overall survival (OS), disease free survival (DFS) and recurrence free survival (RFS) were calculated to evaluate the association between circRNAs expression and survival of cancer patients.

Results

A total of 27 studies were involved in the meta-analysis, including 16 diagnostic and 11 prognostic articles. Among the diagnostic studies, 18 kinds of circRNAs had been investigated, in which 3 were up regulated and 15 were down regulated. Their pooled sensitivity, specificity and AUC were 0.71(0.65–0.77), 0.77(0.72–0.81) and 0.81(0.77–0.84), respectively. In stratified analysis, a higher specificity was shown in circRNAs for diagnosing gastric cancer and hepatocellular cancer. 12 circRNAs were involved in the prognostic studies, including 6 up-regulated and 6 down-regulated circRNAs. Their overall HR of OS and DFS/RFS were 1.37(0.98–1.75) and 2.28 (0.77–3.79), respectively.

Conclusions

CircRNAs have the potential to be biomarkers for diagnosis and prognosis of cancers. Further investigations are still needed to explore the clinical value of circRNAs as tumor markers.

Downregulated expression of hsa_circ_0074362 in gastric cancer and its potential diagnostic values

AIM

To explore the diagnostic value of hsa_circ_0074362 in the screening of gastric cancer.

METHODS

The expression levels of hsa_circ_0074362 in 127 gastric cancer tissues and paired adjacent normal tissues, 83 gastritis tissues and six gastric cancer cell lines were first detected by quantitative reverse transcription-polymerase chain reaction. Then, the relationship between its levels and clinicopathological factors of patients with gastric cancer was analyzed. Finally, a receiver operating characteristic curve was established.

RESULTS

Hsa_circ_0074362 levels were significantly downregulated in gastric cancer tissues, gastritis tissues and gastric cancer cell lines. Its levels were associated with lymphatic metastasis.

CONCLUSION

Hsa_circ_0074362 probably plays a role in the initiation of gastric cancer and may be a potential biomarker of gastric cancer.

Circular RNAs: clinical relevance in cancer

Circular RNAs, as recently discovered new endogenous non-coding RNAs, are important gene modulators with critical roles in tumor initiation and malignant progression. With the development of RNA sequencing and microarray technologies, numerous of functional circRNAs have been identified in cancerous tissues and cell lines. Mechanistically, circRNAs function as miRNA sponges, miRNA reservoirs or parental gene expression regulators. In this review, we discuss the properties and functions of circRNAs and their clinical implication as promising biomarkers for cancer research. Moreover, some emerging fields, such as exosome-loaded and immune response-associated circRNAs, are also discussed, suggesting novel insights into the carcinogenesis and therapy associated with these molecules.

The comprehensive expression analysis of circular RNAs in gastric cancer and its association with field cancerization

Circular RNAs comprise a new class of long noncoding RNAs characterized by their 5' and 3' ends covalently joined. Previous studies have demonstrated that some circular RNAs act as microRNA sponges, and are associated with cellular proliferation in cancer. We were the first to analyze the global expression of circular RNAs in samples of patients without gastric cancer, gastric cancer, and matched tumor-adjacent gastric tissue. Among the samples, we identified 736 previously annotated circular RNAs by RNA-Seq. The tumor-adjacent tissue presented the higher abundance of circular RNAs and could not be considered as a normal tissue, reinforcing the notion of field effect in gastric cancer. We identified five differentially expressed circular RNAs that may be potential biomarkers of this type of cancer. We also predicted candidate microRNAs targets of the highest expressed circular RNAs in gastric tissues and found five miRNAs. Overall, our results support the hypothesis of circular RNAs representing a novel factor in the dynamic epigenetic network of gene regulation, which involves the microRNAs, its mRNAs targets, and the circular RNAs-derived genes. Further studies are needed to elucidate the roles and the functional relevance of the circular RNAs in human diseases.

Circular RNAs: emerging cancer biomarkers and targets

CircRNAs are a class of RNA molecules that structurally form closed loops. CircRNAs are abundant in eukaryotic transcripts and show certain levels of tissue and cell specificity. CircRNAs have been suggested to regulate gene expression at transcriptional, post-transcriptional, and translational levels. An increasing number of studies have shown that circRNAs play important roles in the development and progression of diseases including cancer. In particular, circRNAs have shown great potential in cancer diagnosis, prognosis, and therapy. In this review, we provide an overview of the biogenesis and characteristics of circRNAs, succinctly describe their functions, and comprehensively discuss about the recent advances in the roles of circRNAs in cancer with an emphasis on their clinical values.

Clinical values of circular RNA 0000181 in the screening of gastric cancer

BACKGROUND

Circular RNAs (circRNAs) are recently found involved in cancer occurrence and development. However, their values in the diagnosis of gastric cancers are largely unknown. In this study, we analyzed the values of hsa_circ_0000181 in the diagnosis of gastric cancer.

METHODS

Using divergent primers, hsa_circ_0000181 expression levels in fresh gastric cancer tissues and paired adjacent non-tumorous tissues, and plasmas from patient with gastric cancer and health people were detected by real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The association between hsa_circ_0000181 levels and the clinicopathologic features of patients with gastric cancer was further analyzed. Finally, to evaluate the diagnostic value, receiver operating characteristic (ROC) curve was established.

RESULTS

Hsa_circ_0000181 levels in gastric cancer tissues and plasma from gastric cancer patients were significantly decreased than those in paired adjacent non-tumorous tissues (P < .001) and healthy people (P < .001), respectively. Furthermore, hsa_circ_0000181 expression in gastric cancer tissues was significantly correlated with tumor diameter (P = .027), lymphatic metastasis (P = .044), distal metastasis (P = .023), and carbohydrate antigen 19-9 (P = .031). Its decreased levels in patients' plasma were significantly associated with differentiation (P = .038) and carcinoembryonic antigen (P = .037). The areas under ROC curve were 0.756. The specificity of tissue hsa_circ_0000181 and sensitivity of plasma hsa_circ_0000181 were 85.2% and 99.0%, respectively.

CONCLUSIONS

Thanks to the high stability, tissue and plasma hsa_circ_0000181 may be a novel biomarker for the diagnosis of gastric cancer.

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

Circular RNAs (circRNAs) are a new class of noncoding RNAs. However, the expression profile and clinical significance of circRNAs in human gastric cancer is unclear. The global circRNA expression profile in human gastric cancer was measured by circRNA microarray. Hsa_circ_0014717, one of the most downregulated circRNAs in microarray, was selected as a targeted circRNA to explore its levels in gastric tissues and gastric juice. Freeze-thaw experiment and incubation experiment confirmed the stability of gastric juice circRNAs. A total of 308 circRNAs, including 107 (34.74%) upregulated and 201 (65.26%) downregulated circRNAs, were found significantly aberrantly expressed in gastric cancer tissues. The top ten upregulated in gastric cancer tissues were hsa_circ_0035445, hsa_circ_0003789, hsa_circ_0063809, hsa_circ_0074362, hsa_circ_0006282, hsa_circ_0011107, hsa_circ_0084606, hsa_circ_0005556, hsa_circ_0050547, and hsa_circ_0006470, while the top ten downregulated ones were hsa_circ_0007099, hsa_circ_0001897, hsa_circ_0007707, hsa_circ_0008832, hsa_circ_0001546, hsa_circ_0002089, hsa_circ_0004680, hsa_circ_0000154, hsa_circ_0004458, and hsa_circ_0008394. The hot-point chromosomes were chr1, chr2, chr3, chr9, and chr17. Hsa_circ_0014717 was significantly downregulated in 77.2% (74/96) gastric cancer tissues. Its levels in gastric cancer tissues were related to tumor stage (P = 0.037), distal metastasis (P = 0.048), tissue carcinoembryonic antigen (P = 0.001), and carbohydrate antigen 19-9 expression (P = 0.021). More importantly, hsa_circ_0014717 can stably exist in human gastric juice; and its nature meets the requirements of clinical detection. Our study uncovered the circRNA expression profile in human gastric cancer. Moreover, some circRNAs can stably exist in human body fluid, and has the potential to be used as novel biomarkers for the screening of high-risk gastric cancer patients.

Decreased expression of hsa_circ_0003570 in hepatocellular carcinoma and its clinical significance

BACKGROUND

Circular RNAs (circRNAs) constitute a class of non-coding RNAs recently discovered to be widespread and abundant in mammalian cells. However, the expression features of most of circRNAs in hepatocellular carcinoma (HCC) are unraveled. In this study, we focused on hsa_circ_0003570, which was found to be down-regulated in HCC tissues in our previous microarray screening.

METHODS

The hsa_circ_0003570 levels in HCC cell lines, HepG2, SMMC-7721, MHCC97L, MHCC97H, and HCCLM3, and human normal hepatic cell line L02 were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Then, its levels in 107 paired HCC tissues and adjacent non-tumor tissues, 60 liver biopsy samples from patients with chronic liver diseases were detected by qRT-PCR. The receiver operating characteristic curve (ROC) was used to evaluate the diagnostic value of hsa_circ_0003570 for HCC.

RESULTS

Hsa_circ_0003570 was not only first found down-regulated in HCC cell lines (P<.001) but also in HCC tissues (P<.001). Moreover, hsa_circ_0003570 was gradually decreased from chronic hepatitis (CH), to liver cirrhosis (LC) and to HCC tissues (P<.01). Its expression levels were significantly correlated with tumor diameter (P=.035), differentiation (P=.013), microvascular invasion (P=.045), Barcelona Clinic Liver Cancer stages (P=.011), tumor-node-metastasis stages (P=.016), and serum alpha-fetoprotein levels (P=.031). The ROC curve demonstrated that hsa_circ_0003570 had poor performance for differentiating HCC from LC and CH, but had relatively good performance for differentiating LC from CH.

CONCLUSIONS

These results indicated that hsa_circ_0003570 expression levels were associated with HCC clinicopathological characteristics.