The tumor suppressor function of hsa_circ_0006282 in gastric cancer through PTEN/AKT pathway.

BACKGROUND: Circular RNAs (circRNAs) play key roles in carcinogenesis. However, the roles of circRNAs in gastric cancer are largely unknown. The aim of this study is to study the possible roles of hsa_circ_0006282 in gastric cancer. METHODS: The hsa_circ_0006282 levels in gastric cancer cell lines, 85 gastritis tissues, and 103 paired gastric cancer tissues and non-tumor tissues were first detected by quantitative real-time reverse transcription-polymerase chain reaction. RNA interference and hsa_circ_0006282 expression plasmid were further used to manipulate hsa_circ_0006282 expression in gastric cancer. Finally, biological effects of hsa_circ_0006282 were analyzed by real-time cell analysis, flow cytometry, Transwell, cell cloning assay and Western blot analysis. RESULTS: Hsa_circ_0006282 was down expressed in gastric cancer cells, gastritis tissues, and gastric cancer tissues. The abilities of cell proliferation, cell migration and resistance to apoptosis were enhanced after hsa_circ_0006282 was downregulated, while overexpression of hsa_circ_0006282 got opposite results. Besides, Western blot showed that the levels of protein kinase B (AKT) and cyclin-dependent kinase 2 (CDK2) were significantly increased and decreased after knockdown and up-regulation of hsa_circ_0006282, respectively, while phosphatase and tensin homolog deleted on chromosome ten (PTEN) was significantly opposite regulated. Finally, hsa_circ_0006282 promoted the expression of PTEN by sponging hsa-miR-136-5p. CONCLUSION: By regulating the PTEN/AKT signaling pathway through competitively binding with hsa-miR-136-5p, hsa_circ_0006282 suppresses the growth of gastric cancer.

tRNA-derived fragments: Mechanisms underlying their regulation of gene expression and potential applications as therapeutic targets in cancers and virus infections.

tRNA-derived fragments (tRFs) are a new category of regulatory noncoding RNAs with distinct biological functions in cancers and stress-induced diseases. Herein, we first summarize the classification and biogenesis of tRFs. tRFs are produced from pre-tRNAs or mature tRNAs. Based on the incision loci, tRFs are classified into several types: tRF-1, tRF-2, tRF-3, tRF-5, and i-tRF. Some tRFs participate in posttranscriptional regulation through microRNA-like actions or by displacing RNA binding proteins and regulating protein translation by promoting ribosome biogenesis or interfering with translation initiation. Other tRFs prevent cell apoptosis by binding to cytochrome c or promoting virus replication. More importantly, the dysregulation of tRFs has important clinical implications. They are potential diagnostic and prognostic biomarkers of gastric cancer, liver cancer, breast cancer, prostate cancer, and chronic lymphocytic leukemia. tRFs may become new therapeutic targets for the treatment of diseases such as hepatocellular carcinoma and respiratory syncytial virus infection. Finally, we point out the existing problems and future research directions associated with tRFs. In conclusion, the current progress in the research of tRFs reveals that they have important clinical implications and may constitute novel molecular therapeutic targets for modulating pathological processes.

Downregulated Expression of linc-ROR in Gastric Cancer and Its Potential Diagnostic and Prognosis Value.

BACKGROUND: Gastric cancer (GC) is one of the global mortality diseases and has a poor prognosis due to the lack of ideal tumor biomarkers. Numerous studies have shown that long noncoding RNAs (lncRNAs) can affect the occurrence and development of cancer through a variety of signaling pathways. The abnormal expression and specificity of lncRNAs in tumors make them potential biomarkers of cancers. Nevertheless, the diagnostic roles of lncRNAs in GC have been poorly understood. So this study focuses on the clinical diagnostic value of lncRNAs in GC. MATERIALS AND METHODS: Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to investigate the expression of the linc-ROR (long intergenic noncoding RNA, regulator of reprogramming) in 105 paired GC tissues and adjacent normal tissues. Receiver operating characteristic (ROC) curve and area under the curve (AUC) were established to assess the diagnostic value of linc-ROR. The relationship between expression of linc-ROR and clinicopathological factors of patients with GC was further explored. Kaplan-Meier analysis was performed to evaluate the prognostic value of linc-ROR expression. RESULTS: The linc-ROR expression level was significantly decreased in GC tissues compared with its adjacent nontumor tissues (n = 105, P < 0.001). We also discovered that linc-ROR was evidently downregulated in 68.6% (72/105) of GC tissues. The AUC's value of linc-ROR was up to 0.6495, with sensitivity and specificity of 0.7524 and 0.5143, respectively. Intriguingly, the linc-ROR expression levels were obviously associated with tumor differentiation (P = 0.004). Notably, the overall survival rate of GC patients with high expression of linc-ROR was significantly higher than those with low expression. CONCLUSION: Our data revealed that linc-ROR has clinical potential as a biomarker for the diagnosis of GC and assessment of its prognosis.

The clinical significance of serum chitinase 3-like 1 in hepatitis B-related chronic liver diseases.

AIM: In the present study, we purposed to determine serum chitinase 3-like 1 (CHI3L1) expression characteristics in chronic liver diseases monoinfected with hepatitis B virus and analyze its diagnostic value in liver fibrosis. METHODS: A total of 467 chronic hepatitis B (CHB) patients, 312 liver cirrhosis (LC) patients, and 104 hepatocellular carcinoma (HCC) patients at our institution were enrolled, and clinical indicators were analyzed. RESULTS: Our data have shown that the expression level of serum CHI3L1 was steadily increased from CHB to LC to HCC (P < .001). Serum CHI3L1 expression levels were positively associated with liver stiffness measurement (LSM), fibrosis-4 (FIB-4) index, aspartate aminotransferase-to-platelet ratio index (APRI), and HCC stage. The receiver operating characteristic (ROC) curve proved that serum CHI3L1 was superior to other noninvasive methods (LSM, FIB-4, and APRI) with an area under the ROC curve (AUC) of 0.97 in diagnosing significant fibrosis. CONCLUSIONS: Serum CHI3L1 harbors significant clinical value in chronic liver diseases infected with hepatitis B virus, especially in the diagnosis of fibrosis.

The biogenesis and biological functions of circular RNAs and their molecular diagnostic values in cancers.

BACKGROUND: In addition to non-coding RNAs (lncRNAs) and microRNAs (miRNAs), circular RNAs (circRNAs) are endogenous RNAs with various functions, which have recently become a research hotspot. CircRNAs are a kind of closed circular RNA molecule widely existing in transcriptomes. Due to lack of free ends, they are not easily cleaved by RNase R, thus avoiding degradation. They are more stable than linear RNAs. METHODS: Data were collected through PubMed. The following search terms were used: "circular RNA," "circRNA," "cancer," "mechanism," "biogenesis," "biomarker," "diagnosis." Only articles published in English were included. RESULTS: Most circRNAs express tissue/developmental stage specificity. Moreover, circRNAs are involved in the regulation of a variety of biological activities. In this review, we discuss the formation, classification, and biological functions of circRNAs, especially their molecular diagnostic values in common cancers, including gastric cancer (hsa_circ_002059, circ_LARP4, hsa_circ_0000190, hsa_circ_0000096, circ-SFMBT2, and circ_PVT1), hepatocellular carcinoma (circ_104075, circRNA_100338, circ_MTO1, and circZKSCAN1), colorectal cancer (hsa_circ_0136666 and hsa_circ_0000523), lung cancer (hsa_circ_0006427, circ_100876, and circ_ABCB10), breast cancer (hsa_circ_0089105, circAGFG1, and circEPSTI1), bladder cancer (circFNDC3B and circTFRC), and esophageal squamous cell carcinoma (circ_100876 and circ-DLG1). CONCLUSION: CircRNAs not only play important roles in tumorigenesis, but also may become new diagnostic biomarkers.

Hsa_circ_0065149 is an Indicator for Early Gastric Cancer Screening and Prognosis Prediction.

Circular RNAs (circRNAs) are an endogenous RNAs with a covalently closed cyclic structure. They have emerged recently as key regulators in the development and progression of human cancers. However, the clinical values of most circRNAs in gastric cancer (GC) are unknown. Hsa_circ_0065149, one of the dysregulated circRNAs in gastric carcinogenesis detected by circRNA microarray, was chose as a targeted circRNA in this study. We firstly enlarged sample size and identified the level changes of hsa_circ_0065149 among four stages of gastric tumorigenesis from healthy gastric mucosa, gastritis, intestinal metaplasia to GC. Then, the potential relationship between hsa_circ_0065149 expression levels and GC patients' clinicopathological factors was investigated. Moreover, the clinical significance of hsa_circ_0065149 in plasma exosomes and gastric juice were explored. Receiver operating characteristic (ROC) curve and Kaplan-Meier survival curve were constructed to evaluate diagnostic and prognostic values. Finally, bioinformatics analysis was performed to excavate the potential functions of hsa_circ_0065149. Hsa_circ_0065149 expression was only significantly down-regulated in gastric cancer, not changed among healthy gastric mucosa and gastritis intestinal metaplasia. Low hsa_circ_0065149 expression levels in GC tissues were significantly associated with tumor diameter (P = 0.034) and perineural invasion (P = 0.037). GC patients with low hsa_circ_0065149 levels had a much longer overall survival than those in high group (P = 0.020). More important, hsa_circ_0065149 levels were significantly decreased in plasma exosomes of early GC patients. As a screening biomarker for early GC, hsa_circ_0065149 in plasma exosomes has higher sensitivity and specificity than traditional clinical biomarkers. Bioinformatics analysis suggest that the abnormal expression of hsa_circ_0065149 may play an important role during gastric carcinogenesis. Those results indicate that hsa_circ_0065149 in exosmoes is an indicator for early GC screening and prognosis prediction.

Clinical significance of hsa_circ_0000419 in gastric cancer screening and prognosis estimation.

Gastric cancer (GC) is an aggressive malignancy that seriously threatens human health. Accumulating studies have shown that circular RNAs (circRNAs) can be used as diagnostic biomarkers and promising therapeutic targets with significant clinical implications. However, the roles of circRNAs in GC remain largely elusive. In this study, hsa_circ_0000419 levels in GC cell lines, tissues and plasma were detected, and their clinicopathological correlation was analyzed. Receiver operating characteristic (ROC) curve and Kaplan-Meier survival curve were established for its clinical values evaluation. Potential biological functions were further predicted and annotated by bioinformatics analysis. Hsa_circ_0000419 levels were significantly decreased in GC cell lines, cancer tissues and plasma from GC patients. GC tissues hsa_circ_0000419 levels were associated with cell differentiation, Borrmann type, overall survival and disease-free survival, whereas plasma hsa_circ_0000419 were significantly correlated with tumor stage, lymphatic and distal metastasis, venous and perineural invasion. Plasma hsa_circ_0000419 exists in exosomes and maintain good stability. Bioinformatics analysis showed that hsa_circ_0000419 involved in gastric tumorigenesis and progression via its interaction with microRNAs. Collectively, our study suggests that hsa_circ_0000419 is a novel biomarker for GC screening as well as an important indicator for prognostic estimation of patients with advanced GC.

Tumor-suppressive circular RNAs: Mechanisms underlying their suppression of tumor occurrence and use as therapeutic targets.

Circular RNAs (circRNAs) have a covalently closed circular conformation and are structurally stable. Those circRNAs with tumor-suppressive properties play an important role in tumorigenesis and metastasis and thus may be used as therapeutic targets of cancers. Herein, we review the current understanding of the classification of circRNAs and summarize the functions and mechanisms of circRNAs that have tumor-suppressive roles in various cancers, including liver cancer (circARSP91, circADAMTS13, circADAMTS14, circMTO1, hsa_circ_0079299, and circC3P1), bladder cancer (circFNDC3B, circITCH, circHIPK3, circRNA-3, cdrlas, and circLPAR1), gastric cancer (circLARP4, circYAP1, hsa_cric_0000096, hsa_circ_0000993, and circPSMC3), breast cancer (circ_000911, hsa_circ_0072309, and circASS1), lung cancer (hsa_circ_0000977, circPTK2, circ_0001649, hsa_circ_100395, and circ_0006916), glioma (circ_0001946, circSHPRH, and circFBXW7), and colorectal cancer (circITGA7 and hsa_circ_0014717). Thanks to their structural stability, these tumor-suppressive circRNAs may be used as potential and potent therapeutic targets. Moreover, we propose a new method for the classification of circRNAs. Based on whether they can be translated, circRNAs can be divided into noncoding circRNAs and coding circRNAs.

Clinical significances of hsa_circ_0067582 and hsa_circ_0005758 in gastric cancer tissues.

BACKGROUND: Circular RNAs (circRNAs) are a special class of endogenous noncoding RNAs that have numerous biological functions in normal situation and diseases including cancers. However, the clinical significance of circRNAs in gastric cancer (GC) remains largely unknown. Here, we chose two representative circRNAs, hsa_circ_0067582 and hsa_circ_0005758, to investigate their clinical significance in GC patients. METHODS: Using real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR), we explored the expression levels of hsa_circ_0067582 and hsa_circ_0005758 in tissues with different stages of gastric tumorigenesis. Then, the relationships between their expression levels and GC patients' clinicopathological factors were further investigated. Receiver operating characteristic (ROC) curves were established for evaluating diagnostic values of hsa_circ_0067582 and hsa_circ_0005758. RESULTS: Compared with healthy control tissues, both hsa_circ_0067582 and hsa_circ_0005758 were significantly decreased in GC tissues. Besides, hsa_circ_0067582 expression was associated with GC patients' tissue CEA level (P <.001) and stages (P = .037); and hsa_circ_0005758 expression was relevant to tissue CEA level (P < .001) and perineural invasion (P = .048). The area under the ROC curve (AUC) of hsa_circ_0067582 was up to 0.671. The cutoff value was set at 10.61, with which the sensitivity and specificity were 55.2% and 75.0%, respectively. Similar to hsa_circ_0005758, the AUC of hsa_circ_0005758 was 0.721. The cutoff value was set at 10.20, with which the sensitivity and specificity were 75.0% and 67.7%, respectively. CONCLUSION: These results showed that both hsa_circ_0067582 and hsa_circ_0005758 may play an important role in gastric carcinogenesis; and they may be potential indicators for GC diagnosis.

Using tRNA halves as novel biomarkers for the diagnosis of gastric cancer.

BACKGROUND: tRNA halves (tiRNAs) are produced from mature tRNAs. They have important roles both with in normal cells and cancer cells. However, the diagnostic value of tiRNAs in cancers have not yet been elucidated. OBJECTIVE: To explore the diagnostic value of tiRNA-5034-GluTTC-2 in gastric cancer. PATIENTS AND METHODS: Quantitative reverse transcription-polymerase chain reaction was used to detect the expression levels of tiRNA-5034-GluTTC-2 in paired gastric cancer tissues and adjacent normal tissues, plasmas from patients with gastric cancer and healthy people, and gastric cancer cell lines. Then, the relationship between its levels and clinicopathological factors of patients with gastric cancer was analyzed. A receiver operating characteristic (ROC) curve was established to predict the diagnostic value. RESULTS: tiRNA-5034-GluTTC-2 was first found to be down-regulated in gastric cancer tissues and plasmas. Its levels were significantly associated with tumor size. The area under the ROC curve (AUC) was 0.779 and 0.835 in tissue and plasma, respectively. The sensitivity, specificity and AUC were 84.7%, 92.8%, and 0.915 when tissues and plasmas were used in combination, respectively. The overall survival rate of patients with a lower expression of tiRNA-5034-GluTTC-2 was significantly lower than those with a higher expression. CONCLUSIONS: These results indicated that tiRNA-5034-GluTTC-2 may be a novel biomarker for the diagnosis of gastric cancer.

CRISPR-Cpf1-mediated genome editing and gene regulation in human cells.

Clustered regularly interspaced short palindromic repeat (CRISPR) system is being championed as a robust and flexible tool for genome editing. Compared with CRISPR associated protein 9 (Cas9), the CRISPR from Prevotella and Francisella 1 (Cpf1) protein has some distinct characteristics, including RNase activity, T-rich protospacer adjacent motif (PAM) preference and generation of sticky cutting ends. The extremely low propensity of off-target effects and relatively high editing efficiency represent prominent advantages of Cpf1 over Cas9. CRISPR-Cpf1, alone or fused with function domains, has broadly expanded the applications such as multiplex gene knockout, transcriptional repression or activation and epigenome editing in a drug controlled way. Meanwhile, the modification of CRISPR RNAs (crRNAs) with aptamer RNA achieves great promotion on genome editing. Moreover, disease-associated gene manipulation in mice, tumor mutation detection in patients with cancers, and more yet to come, represent growing demands of CRISPR-Cpf1 in clinical genome therapy. In this review, we summarized the unique properties of Cpf1 and the molecular mechanisms underlying CRISPR-Cpf1 on gene editing and regulation in human cells.

Identification and functional annotation of metabolism-associated lncRNAs and their related protein-coding genes in gastric cancer.

BACKGROUND: Long noncoding RNAs (lncRNAs) play important roles in carcinogenesis. However, the roles of metabolism-associated lncRNAs in cancers are still unclear. METHODS: A microarray of metabolism-associated lncRNAs was used to detect their expression patterns between gastric cancer and paired nontumorous tissues. Its results and gastric cancer differential gene expression data from public databases were used to screen the metabolic pathway-associated lncRNAs. A metabolic network with microRNAs (miRNAs), lncRNAs, and protein-coding genes was further constructed. Finally, the expression of TOPORS antisense RNA 1 (TOPORS-AS1), a screened highly expressed lncRNA and its associated protein-coding gene, NADH: ubiquinone oxidoreductase subunit B6 (NDUFB6), were verified by reverse transcription polymerase chain reaction. RESULTS: A total of eight upregulated and one downregulated lncRNAs and 25 upregulated and 20 downregulated protein-coding genes were found to be involved in metabolism in gastric cancer. Within the lncRNAs-miRNAs-mRNAs metabolic network, 78 miRNA-target links, 546 positive coexpression relationships, and 191 protein-protein interactions were found. The expression of TOPORS-AS1 and its associated gene, NDUFB6 in gastric cancer tissues was significantly lower than that in adjacent nontumor tissues. Moreover, NDUFB6 expression was associated with the invasion and distal metastasis of gastric cancer. CONCLUSIONS: The metabolism-associated lncRNAs play important roles in the occurrence of gastric cancer.

Circular RNA 0068669 as a new biomarker for hepatocellular carcinoma metastasis.

BACKGROUND: Circular RNAs (circRNAs) play important roles in disease occurrence. However, the roles of circRNAs in the diagnosis of hepatocellular carcinoma (HCC) are largely unknown. The aim of this study is to investigate the clinical diagnostic values of hsa_circ_0068669 (Alias: hsa_circ_103561), one of the representative HCC-associated circRNAs. METHODS: Hsa_circ_0068669 expression levels in HCC tissues, HCC cell lines, and chronic hepatitis tissues were detected by real-time quantitative reverse transcription-polymerase chain reaction. Its expression levels between HCC tissues and adjacent non-tumorous tissues were analyzed using paired t test. Independent t test and one-way analysis of variance (ANOVA) were performed to analyze the relationships between hsa_circ_0068669 expression levels and clinicopathological factors of patients with HCC. A receiver operating characteristic (ROC) curve was established to estimate the value of hsa_circ_0068669 as a biomarker in HCC. RESULTS: Hsa_circ_0068669 expression was significantly downregulated in HCC tissues and HCC cell lines compared with paired non-tumorous tissues and normal hepatic cell line, respectively. Moreover, hsa_circ_0068669 expression in HCC tissues was decreased comparing with chronic hepatitis tissues. Furthermore, hsa_circ_0068669 expression was correlated with microvascular invasion and TNM stages. CONCLUSIONS: Our findings indicate that hsa_circ_0068669 might be served as a novel potential biomarker for HCC metastasis.

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.

Reduced expression of circRNA hsa_circ_0003159 in gastric cancer and its clinical significance.

BACKGROUND: Circular RNAs (circRNAs) play a crucial role in the occurrence of several diseases including cancers. However, little is known about circRNAs' diagnostic values for gastric cancer, one of the worldwide most common diseases of mortality. METHODS: The hsa_circ_0003159 levels in 108 paired gastric cancer tissues and adjacent non-tumorous tissues from surgical patients with gastric cancer were first detected by real-time quantitative reverse transcription-polymerase chain reaction. Then, the relationships between hsa_circ_0003159 expression levels in gastric cancer tissues and the clinicopathological factors of patients with gastric cancer were analyzed. Finally, its diagnostic value was evaluated through the receiver operating characteristic curve. RESULTS: Compared with paired adjacent non-tumorous tissues, hsa_circ_0003159 expression was significantly down-regulated in gastric cancer tissues. What is more, we found that hsa_circ_0003159 expression levels were significantly negatively associated with gender, distal metastasis, and tumor-node-metastasis stage. CONCLUSIONS: All of the results suggest that hsa_circ_0003159 may be a potential cancer marker of patients with gastric cancer.

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.

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.

Plasma circular RNA profiling of patients with gastric cancer and their droplet digital RT-PCR detection.

To observe the diagnostic values of circular RNAs (circRNAs), their expression profiles between gastric cancer patients' plasma and healthy controls were first assessed by circRNA microarray. Then, circRNA levels were measured by reverse transcription quantitative polymerase chain reaction (RT-qPCR) and RT-droplet digital PCR (RT-ddPCR), respectively. A total of 343 differentially expressed circRNAs were found. The top 10 elevated circRNAs in patients were hsa_circ_0088300, hsa_circ_0075825, hsa_circ_0019172, hsa_circ_0000220, hsa_circ_0035277, hsa_circ_0000301, hsa_circ_0000189, hsa_circ_0090080, hsa_circ_0001888, and hsa_circ_0001874. The top 10 reduced circRNAs were hsa_circ_0004771, hsa_circ_0001190, hsa_circ_0061276, hsa_circ_0092337, hsa_circ_0058495, hsa_circ_0061274, hsa_circ_0075829, hsa_circ_0080845, hsa_circ_0001006, and hsa_circ_0003764. In cancer and dysplasia tissues, hsa_circ_0001017 and hsa_circ_0061276 were downregulated. Their levels were significantly associated with distal metastasis. The area under receiver operating characteristic curve in combinative use was 0.966 with 95.5% sensitivity and 95.7% specificity. Patients with low plasma hsa_circ_0001017 or hsa_circ_0061276 had a much shorter overall survival than those with high levels. Patients whose plasma hsa_circ_0001017 or hsa_circ_0061276 levels recovered to normal after operation had a longer disease-free survival. Finally, the in vitro model indicated gastric cancer cells secreting circRNAs into plasma. In conclusion, RT-ddPCR is a potent non-invasive and absolute quantification method for simultaneous detection of multiple circRNAs. Hsa_circ_0001017 and hsa_circ_0061276 are new potential biomarkers for gastric cancer. KEY MESSAGE: A total of 343 circRNAs are differentially expressed between gastric cancer patients' plasma and healthy controls. Hsa_circ_0001017 and hsa_circ_0061276 are downregulated in gastric cancer tissues. The RT-ddPCR is a potent method for simultaneous detection of multiple circRNAs in plasma. Hsa_circ_0001017 and hsa_circ_0061276 are potential biomarkers for gastric cancer.

Low expression of hsa_circ_0006633 in human gastric cancer and its clinical significances.

Circular RNAs are new type of endogenous RNAs, which play an important role in the regulation of gene expression and indicate a great capacity in clinical diagnosis and treatments of diseases. However, the role of circular RNAs in gastric cancer remains unknown. In this study, we chose hsa_circ_0006633 as the target circular RNA and measured its levels in human gastric cancer tissues, plasma, and gastric cell lines by real-time quantitative reverse transcription polymerase chain reaction. Hsa_circ_0006633 levels at multiple stages of gastric tumorigenesis were then explored, and its relationships with clinicopathological features were analyzed as well. We found that the expression levels of hsa_circ_0006633 in four gastric cancer cell lines, HGC-27, SGC-7901, MGC-803, and AGS, were downregulated than those in normal gastric mucosal epithelial cell line GES-1. Then, we further detected that it was downregulated in 79.2% (76/96) gastric cancer tissues compared with the adjacent non-tumorous tissues. The lower expression of hsa_circ_0006633 was associated with cancer distal metastasis ( p = 0.037) and tissue carcinoembryonic antigen level ( p = 0.041). In addition, hsa_circ_0006633 expression was significantly decreased in gastritis and dysplasia tissues comparing with the healthy control. Moreover, plasma hsa_circ_0006633 levels were significantly increased in gastric cancer compared with healthy control. Our data imply that hsa_circ_0006633 may play an important role in gastric carcinogenesis and is also a potential biomarker for screening 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.