Upregulated circular RNA circ_0007534 indicates an unfavorable prognosis in pancreatic ductal adenocarcinoma and regulates cell proliferation, apoptosis, and invasion by sponging miR-625 and miR-892b

The Effect of Intratumor Heterogeneity in Pancreatic Ductal Adenocarcinoma Progression and Treatment

BACKGROUND AND OBJECTIVES

Pancreatic cancer is one of the most lethal malignancies. Even though many substantial improvements in the survival rates for other major cancer forms were made, pancreatic cancer survival rates have remained relatively unchanged since the 1960s. Even more, no standard classification system for pancreatic cancer is based on cellular biomarkers. This review will discuss and provide updates about the role of stem cells in the progression of PC, the genetic changes associated with it, and the promising biomarkers for diagnosis.

MATERIALS AND METHODS

The search process used PubMed, Cochrane Library, and Scopus databases to identify the relevant and related articles. Articles had to be published in English to be considered.

RESULTS

The increasing number of studies in recent years has revealed that the diversity of cancer-associated fibroblasts is far greater than previously acknowledged, which highlights the need for further research to better understand the various cancer-associated fibroblast subpopulations. Despite the huge diversity in pancreatic cancer, some common features can be noted to be shared among patients. Mutations involving CDKN2, P53, and K-RAS can be seen in a big number of patients, for example. Similarly, some patterns of genes and biomarkers expression and the level of their expression can help in predicting cancer behavior such as metastasis and drug resistance. The current trend in cancer research, especially with the advancement in technology, is to sequence everything in hopes of finding disease-related mutations.

CONCLUSION

Optimizing pancreatic cancer treatment requires clear classification, understanding CAF roles, and exploring stroma reshaping approaches.

Study of MicroRNA Cluster Located on Chromosome X in Serum and Breast Cancer Tissue

Breast cancer is a prevalent cancer type among women worldwide, with the second highest incidence rate. The objective of this study was to identify a non-invasive biomarker for detecting breast cancer, and to this end, miRNA clusters were investigated as potential candidates. A micro-RNA cluster located on the X chromosome q27.3 region was selected for the study. The research was conducted as a case-control study with a sample size of 100 patients with breast cancer and 100 healthy individuals. Tissue samples from breast cancer tumors and tumor margins were collected from the breast cancer patients. Following RNA extraction and RT-PCR, the expression of miRNA clusters, including miR-506, miR-507, miR-508, miR-509, miR-513, miR-888, miR-891, miR-892-a, and miR-892-b, was analyzed in the serum and breast tissue of the breast cancer patients. The expression of various micro-RNAs in the case and control serums was compared, and it was found that all mentioned micro-RNAs, except mir888-5p and mir-509-3p, exhibited significant and meaningful differences between the patients and control serum groups. These micro-RNAs can be considered as potential tumor markers with a confidence level of P-value = 0.0001. In contrast, mir888-5p and mir-509-3p were considered non-significant. The expression of all micro-RNAs in the tumor margin and BC tumor was significant with a P-value < 0.0001. Based on the ROC curves, all the mentioned microRNAs, except mir-888-5p, mir-513-a-5p, and mir-509-3p, exhibited high sensitivity and specificity and can be considered remarkable non-invasive tumor markers for breast cancer detection.

Circular RNAs in pancreatic cancer progression

Pancreatic cancer (PC), typically diagnosed at relatively advanced stages with poor prognosis, is a dominant cause of cancer-related deaths worldwide. Accumulating evidence demonstrates that circular RNAs (circRNAs) are abnormally expressed in diverse tumors and affect tumorigenesis and progression. In this article, we examine the roles of circRNAs in regulation of PC progression. Additionally, circRNAs enriched in exosomes could be transferred among PC cells to modulate malignancy. Characterization of regulatory mechanisms involving circRNAs in general and PC specifically will enable earlier detection and potential development of therapeutic strategies.

CircRNA PGAM1 Promotes the Migration and Invasion of Pancreatic Adenocarcinoma Cells by Activating the AKT/mTOR Signaling Pathway

Pancreatic adenocarcinoma (PAAD) is a lethal malignancy of the gastrointestinal tract. Circular RNA, an endogenous noncoding RNA, is considered a new regulatory molecule in tumorigenesis and development. Here, we aimed to investigate the role of circPGAM1 in PAAD. The PAAD cell line HPAC was transfected with OE-circPGAM1 to overexpress circPGAM1 and treated with AZD5363 to inhibit the AKT/mTOR pathway. Simultaneously, another PAAD cell line BxPC-3 was transfected with sh-circPGAM1 to silence circPGAM1. The GEPIA database was used to determine the expression of circPGAM1 in PAAD and its association with overall and disease-free survival. CircPGAM1 expression levels were determined in cell lines using reverse transcription-quantitative PCR. The cell counting kit-8, wound healing, and transwell assays were performed to determine cell migration and invasion. The protein expression levels of phosphorylated AKT and mTOR were determined using western blotting. CircPGAM1 was overexpressed in PAAD and related to poor prognosis. Silencing circPGAM1 inhibited migration and invasion of BxPC-3 cells, and overexpression of circPGAM1 showed the opposite effects. Overall, circPGAM1 promoted the migration and invasion of PAAD cells through the AKT/mTOR axis.

Noncoding RNAs: an emerging modulator of drug resistance in pancreatic cancer

Pancreatic cancer is the eighth leading cause of cancer-related deaths worldwide. Chemotherapy including gemcitabine, 5-fluorouracil, adriamycin and cisplatin, immunotherapy with immune checkpoint inhibitors and targeted therapy have been demonstrated to significantly improve prognosis of pancreatic cancer patients with advanced diseases. However, most patients developed drug resistance to these therapeutic agents, which leading to shortened patient survival. The detailed molecular mechanisms contributing to pancreatic cancer drug resistance remain largely unclear. The growing evidences have shown that noncoding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), are involved in pancreatic cancer pathogenesis and development of drug resistance. In the present review, we systematically summarized the new insight on of various miRNAs, lncRNAs and circRNAs on drug resistance of pancreatic cancer. These results demonstrated that targeting the tumor-specific ncRNA may provide novel options for pancreatic cancer treatments.

Diagnostic and prognostic role of circRNAs in pancreatic cancer: a meta-analysis

Background

Circular RNAs (circRNAs) are types of endogenous noncoding RNAs produced by selective splicing that are expressed highly specifically in various organisms and tissues and have numerous clinical implications in the regulation of cancer development and progression. Since circRNA is resistant to digestion by ribonucleases and has a long half-life, there is increasing evidence that circRNA can be used as an ideal candidate biomarker for the early diagnosis and prognosis of tumors. In this study, we aimed to reveal the diagnostic and prognostic value of circRNA in human pancreatic cancer (PC).

Methods

A systematic search for publications from inception to 22 July 2022 was conducted on Embase, PubMed, Web of Science (WOS), and the Cochrane Library databases. Available studies that correlated circRNA expression in tissue or serum with the clinicopathological, diagnostic, and prognostic values of PC patients were enrolled. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to evaluate clinical pathological characteristics. Area under the curve (AUC), sensitivity, and specificity were adopted to assess diagnostic value. Hazard ratios (HRs) were utilized to assess disease-free survival (DFS) and overall survival (OS).

Results

This meta-analysis enrolled 32 eligible studies, including six on diagnosis and 21 on prognosis, which accounted for 2,396 cases from 245 references. For clinical parameters, high expression of carcinogenic circRNA was significantly associated with degree of differentiation (OR = 1.85, 95% CI = 1.47-2.34), TNM stage (OR = 0.46, 95% CI = 0.35-0.62), lymph node metastasis (OR = 0.39, 95% CI = 0.32-0.48), and distant metastasis (OR = 0.26, 95% CI = 0.13-0.51). As for clinical diagnostic utility, circRNA could discriminate patients with pancreatic cancer from controls, with an AUC of 0.86 (95% CI: 0.82-0.88), a relatively high sensitivity of 84%, and a specificity of 80% in tissue. In terms of prognostic significance, carcinogenic circRNA was correlated with poor OS (HR = 2.00, 95% CI: 1.76-2.26) and DFS (HR = 1.96, 95% CI: 1.47-2.62).

Conclusion

In summary, this study demonstrated that circRNA may act as a significant diagnostic and prognostic biomarker for pancreatic cancer.

Hsa_circ_0084003 modulates glycolysis and epithelial-mesenchymal transition in pancreatic ductal adenocarcinoma through targeting hsa-miR-143-3p/DNMT3A axis

Pancreatic ductal adenocarcinoma, one of the deadliest tumors of the digestive tract, is a difficult and invasive malignancy. Current treatment for pancreatic ductal adenocarcinoma mainly depends on surgery combined with radiotherapy and chemotherapy, which, however, often resulting in questionable curative effect. Therefore, new targeted therapies are needed in future treatment. We first interfered with hsa_circ_0084003 expression in pancreatic ductal adenocarcinoma cells, and further studied how hsa_circ_0084003 functioned in regulating pancreatic ductal adenocarcinoma cell aerobic glycolysis and epithelial-mesenchymal transition, and also evaluated the regulatingeffect of hsa_circ_0084003 on hsa-miR-143-3p and its target DNA methyltransferase 3A. Hsa_circ_0084003 knockdown could notably inhibit the aerobic glycolysis and epithelial-mesenchymal transition of pancreatic ductal adenocarcinoma cells. Mechanistically, hsa_circ_0084003 could regulate its downstream target DNA methyltransferase 3A by binding to hsa-miR-143-3p, and overexpression of hsa_circ_0084003 could reverse the anticarcinogenic effect of hsa-miR-143-3p on aerobic glycolysis and epithelial-mesenchymal transition in pancreatic ductal adenocarcinoma cells. Hsa_circ_0084003, as a carcinogenic circular RNA, regulated its downstream target DNA methyltransferase 3A to promote pancreatic ductal adenocarcinoma cell aerobic glycolysis and epithelial-mesenchymal transition through sponging hsa-miR-143-3p. Therefore, hsa_circ_0084003 could be studied as a possible therapeutic target regarding pancreatic ductal adenocarcinoma.

Prognostic, Diagnostic, and Clinicopathological Significance of Circular RNAs in Pancreatic Cancer: A Systematic Review and Meta-Analysis

Pancreatic cancer (PC) is a highly aggressive malignant tumor with a high mortality rate. It is urgent to find optimal molecular targets for the early diagnosis and treatment of PC. Here, we aimed to systematically analyze the prognostic, diagnostic, and clinicopathological significance of circular RNAs (circRNAs) in PC. Relevant studies were screened through PubMed, Web of Science, and other databases. The prognostic value of PC-associated circRNAs was assessed using the composite hazard ratio (HR), the diagnostic performance was assessed using the area under the summary receiver operator characteristic (SROC) curve (AUC), and the correlation with clinicopathological characteristics using the composite odds ratio (OR) was explored. In our study, 48 studies were included: 34 for prognosis, 11 for diagnosis, and 30 for correlation with clinicopathological characteristics. For prognosis, upregulated circRNAs were associated with poorer overall survival (OS) (HR = 2.02) and disease-free survival/progression-free survival (HR = 1.84) while downregulated circRNAs were associated with longer OS (HR = 0.55). Notably, the combination of circRNAs, including hsa_circ_0064288, hsa_circ_0000234, hsa_circ_0004680, hsa_circ_0071036, hsa_circ_0000677, and hsa_circ_0001460, was associated with worse OS (HR = 2.35). For diagnosis, the AUC was 0.83, and the pooled sensitivity and specificity were 0.79 and 0.73, respectively. For clinicopathologic characteristics, upregulated circRNAs were associated with poorer tumor differentiation, more nerve and vascular invasion, higher T stage, lymphatic metastasis, distant metastasis, advanced TNM stage, and higher preoperative CA19-9 level. In contrast, downregulated circRNAs were negatively associated with PC differentiation and lymphatic metastasis. Overall, our results showed that circRNAs are closely related to the prognosis and clinicopathological characteristics of PC patients and could be utilized for early diagnosis; thus, they are promising biomarkers for clinical application in PC.

Osthole exhibits an antitumor effect in retinoblastoma through inhibiting the PI3K/AKT/mTOR pathway via regulating the hsa_circ_0007534/miR-214-3p axis

CONTEXT

Osthole shows antitumor effects in various tumours. Studies describing the effect of osthole on retinoblastoma (RB) are rare.

OBJECTIVE

This study investigates the antitumor activity of osthole on RB.

MATERIALS AND METHODS

RB cells were treated with different concentrations of osthole and then subjected to cell viability, colony formation, apoptosis, and western blot assays. The expression of hsa_circ_0007534 in RB tissues was determined by qRT-PCR. Hsa_circ_0007534 overexpression plasmid (oe-circ_0007534), miR-214-3p mimics and negative controls were transfected into RB cells to investigate cell viability. Athymic nude mice were injected with Y-79 cells to establish subcutaneous RB models. These mice were treated with osthole (0.5 mmol/kg) or corn oil for 36 days. Tumour tissues were collected for further analysis.

RESULTS

Osthole inhibited cell viability of RB cells with an IC₅₀ of 200 μM for 24 h treatment and 120 μM for 48 h treatment, respectively. Hsa_circ_0007534 was increased significantly in RB tissues as compared to the matched nontumor tissues (p < 0.001). Oe-circ_0007534 counteracted the inhibitory effect of osthole on cell viability and colony numbers of Y-79 cells (p < 0.01). In vivo experiments indicated osthole significantly decreased the expression of hsa_circ_0007534 (p < 0.01) and increased the level of miR-214-3p in vivo. Furthermore, as compared to the control, osthole decreased the ratios of p-PI3K/PI3K, p-AKT/AKT and p-mTOR/mTOR (p < 0.01). However, hsa_circ_0007534 overexpression reversed the effect of osthole on the PI3K/AKT/mTOR pathway.

DISCUSSION AND CONCLUSIONS

Osthole exhibited an antitumour effect in RB, providing a scientific basis for further research and clinical applications of osthole in RB treatment.

Circ_0007534 as new emerging target in cancer: Biological functions and molecular interactions

Circular RNA (circRNAs), an important member of the non-coding RNA (ncRNA) family, are widely expressed in a variety of biological cells. Owing to their stable structures, sequence conservations, and cell- or tissue-specific expressions, these RNA have become a popular subject of scientific research. With the development of sequencing methods, it has been revealed that circRNAs exert their biological function by sponging microRNAs (miRNAs), regulating transcription, or binding to proteins. Humans have historically been significantly impacted by various types of cancer. Studies have shown that circRNAs are abnormally expressed in various cancers and are involved in the occurrence and development of malignant tumors, such as tumor cell proliferation, migration, and invasion. As one of its star molecules, circ_0007534 is upregulated in colorectal, cervical, and pancreatic cancers; is closely related to the occurrence, development, and prognosis of tumors; and is expected to become a novel tumor marker and therapeutic target. This article briefly reviews the expression and mechanism of circ_0007534 in malignant tumors based on the domestic and foreign literature.

Roles of circular RNAs in the pathogenesis and treatment of pancreatic cancer

Circular RNAs are single-stranded RNAs with a covalently closed structure formed by the process of back-splicing. Aberrant expression of circular RNAs contributes to the pathogenesis of a wide range of cancers. Pancreatic cancer is one of the most lethal cancers due to diagnostic difficulties and limited therapeutic options. Circular RNAs are emerging as novel diagnostic biomarkers and therapeutic targets for pancreatic cancer. Moreover, recent advances in the therapeutic application of engineered circular RNAs have provided a promising approach to overcoming pancreatic cancer. This review discusses the roles of circular RNAs in the pathogenesis of pancreatic cancer and in potential treatment applications and their usefulness as diagnostic biomarkers.

Oncogenic circular RNA circ_0007534 contributes to paclitaxel resistance in endometrial cancer by sponging miR-625 and promoting ZEB2 expression

Circular RNAs (circRNAs) and epithelial to mesenchymal transition (EMT) have been implicated in the development of human cancer and paclitaxel resistance. CircRNA circ_0007534 has been described as a key oncogenic circular RNA that is upregulated in a variety of cancer tissues. However, whether circ_0007534 causes EMT and paclitaxel resistance in endometrial cancer is still unknown. In this work, we revealed that circ_0007534 levels were significantly higher in endometrial cancer tissues, and that high circ_0007534 expression was associated with poor differentiation, advanced tumor stage, cancer invasion, cancer metastasis, and poor prognosis in endometrial cancer patients. Overexpression of circ_0007534 boosted endometrial cancer cell proliferation, invasion, EMT, and paclitaxel resistance. Knockdown of circ_0007534 restored paclitaxel sensitivity and reversed EMT in endometrial cancer cells. We also showed that circ_0007534 enhanced endometrial cancer aggressiveness, progression, and paclitaxel resistance by sponging microRNA-625 (miR-625) and subsequently increasing the expression of the miR-625 target gene ZEB2. Our cell functional studies demonstrated that inhibiting miR-625 or increasing ZEB2 mimicked the effects of circ_0007534 overexpression. Consequently, our data show that circ_0007534 plays a crucial role in EMT and paclitaxel resistance through miR-625/ZEB2 signaling. Targeting the circ_0007534/miR-625/ZEB2 pathway might be an effective strategy for overcoming paclitaxel resistance in endometrial cancer.

Emerging roles of long noncoding RNAs in chemoresistance of pancreatic cancer

Pancreatic cancer is one of the most common causes of cancer death in the world due to the lack of early symptoms, metastasis occurrence and chemoresistance. Therefore, early diagnosis by detection of biomarkers, blockade of metastasis, and overcoming chemoresistance are the effective strategies to improve the survival of pancreatic cancer patients. Accumulating evidence has revealed that long noncoding RNA (lncRNA) and circular RNAs (circRNAs) play essential roles in modulating chemosensitivity in pancreatic cancer. In this review article, we will summarize the role of lncRNAs in drug resistance of pancreatic cancer cells, including HOTTIP, HOTAIR, PVT1, linc-ROR, GAS5, UCA1, DYNC2H1-4, MEG3, TUG1, HOST2, HCP5, SLC7A11-AS1 and CASC2. We also highlight the function of circRNAs, such as circHIPK3 and circ_0000284, in regulation of drug sensitivity of pancreatic cancer cells. Moreover, we describe a number of compounds, including curcumin, genistein, resveratrol, quercetin, and salinomycin, which may modulate the expression of lncRNAs and enhance chemosensitivity in pancreatic cancers. Therefore, targeting specific lncRNAs and cicrRNAs could contribute to reverse chemoresistance of pancreatic cancer cells. We hope this review might stimulate the studies of lncRNAs and cicrRNAs, and develop the new therapeutic strategy via modulating these noncoding RNAs to promote chemosensitivity of pancreatic cancer cells.

Biological functions, mechanisms, and clinical significance of circular RNA in pancreatic cancer: a promising rising star

Pancreatic cancer (PC) is a highly malignant solid tumor with insidious onset and easy early metastasis. Despite tremendous efforts devoted to research in this field, the mechanisms underlying PC tumorigenesis and progression remain unclear. Additionally, robust biomarkers and satisfactory therapeutic strategies for clinical use in PC patients are still lacking. Circular RNAs (circRNAs) are a new type of non-coding RNA originating from precursor messenger RNAs, with a covalent continuous closed-loop structure, strong stability and high specificity. Accumulating evidence suggests that circRNAs may participate in PC development and progression. Abnormal expression of circRNAs in PC is considered a vital factor that affects tumor cell proliferation, migration, invasion, apoptosis, angiogenesis and drug resistance. In this review of relevant articles published in recent years, we describe the basic knowledge concerning circRNAs, including their classification, biogenesis, functions and research approaches. Moreover, the biological roles and clinical significance of circRNAs related to PC are discussed. Finally, we note the questions remaining from recent studies and anticipate that further investigations will address these gaps in knowledge in this field. In conclusion, we expect to provide insights into circRNAs as potential targets for specific PC diagnosis and treatment in the future.

Zic family member 5 promotes survival in human pancreatic cancer and cholangiocarcinoma cells

Pancreatic ductal adenocarcinoma (PDAC) and cholangiocarcinoma (CCA) are malignant tumors with poor prognosis because of the limited effectiveness of traditional chemotherapy and few effective molecular therapeutic agents. Here, we determined the essential roles of Zic family member 5 (ZIC5) in the survival of PDAC and CCA cells. The results showed that ZIC5 is strongly expressed in PDAC and CCA tissues, while ZIC5 expression is barely observed in most normal human adult tissues. Furthermore, ZIC5 expression is related to poor prognosis of patients with PDAC. ZIC5 knockdown via small interfering RNA decreased the phosphorylation of signal transducer and activator of transcription 3 (STAT3), a protein that is associated with PDAC and CCA aggressiveness. However, ZIC5 knockdown induced cell death regardless of STAT3 activation, which is promoted by interleukin (IL) −6, a factor associated with inflammation. Furthermore, knockdown of ZIC5 in PDAC and CCA cells additively or synergistically induced apoptosis with the anti-cancer drug gemcitabine. Thus, ZIC5 constitutes a potential therapeutic target for the treatment of PDAC and CCA.

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ZIC5 is expressed in PDAC and CCA, while barely observed in normal adult tissues.

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ZIC5 expression is related to poor prognosis of patients with PDAC.

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ZIC5 knockdown induces apoptosis in several PDAC and CCA cell lines.

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Knockdown of ZIC5 additively or synergistically induces apoptosis with gemcitabine.

Crucial Roles of miR-625 in Human Cancer

Genetic and epigenetic characteristics are core factors of cancer. MicroRNAs (miRNAs) are small non-coding RNAs which regulate gene expression at the post-transcriptional level via binding to corresponding mRNAs. Recently, increasing evidence has proven that miRNAs regulate the occurrence and development of human cancer. Here, we mainly review the abnormal expression of miR-625 in a variety of cancers. In summarizing the role and potential molecular mechanisms of miR-625 in various tumors in detail, we reveal that miR-625 is involved in a variety of biological processes, such as cell proliferation, invasion, migration, apoptosis, cell cycle regulation, and drug resistance. In addition, we discuss the lncRNA-miRNA-mRNA and circRNA-miRNA-mRNA networks and briefly explain the specific mechanisms of competing endogenous RNAs. In conclusion, we reveal the potential value of miR-625 in cancer diagnosis, treatment, and prognosis and hope to provide new ideas for the clinical application of miR-625.

Sevoflurane represses the progression of glioma by the regulation of circ_0037655/miR-130a-5p/RPN2 axis

Sevoflurane (SEV) is a common anesthetic to inhibit glioma progression. The previous studies have indicated the molecular mechanisms of SEV function in glioma. The objective of this study was to explore the association of circ_00037655 with SEV in glioma. Cell viability was evaluated by Cell Counting Kit-8 (CCK-8) assay. Cell proliferation was analyzed using Edu assay and colony formation assay. Flow cytometry was applied to determine cell apoptosis. Protein analysis was performed via western blot. Cell migration and invasion were assessed by transwell assay. Circ_0037655, microRNA-130a-5p (miR-130a-5p) and ribophorin II (RPN2) levels were detected using the quantitative real-time polymerase chain reaction (qRT-PCR). Dual-luciferase reporter, RNA immunoprecipitation (RIP) and pull-down assays were used to analyze target interaction. The effect of circ_0037655 on SEV in vivo was researched by xenograft models. SEV reduced cell viability, proliferation, migration and invasion but induced apoptosis of glioma cells. Circ_0037655 expression was inhibited after SEV treatment in glioma cells. The effects of SEV on glioma cell behaviors were attenuated by upregulation of circ_0037655. Circ_0037655 interacted with miR-130a-5p and miR-130a-5p targeted RPN2. Circ_0037655 or miR-130a-5p regulated the anti-tumor function of SEV in glioma by targeting miR-130a-5p or RPN2. Circ_0037655 affected the expression of RPN2 via targeting miR-130a-5p. Circ_0037655 relieved SEV-induced glioma growth inhibition in vivo by mediating miR-130a-5p and RPN2 levels. SEV inhibited the malignant progression of glioma cells partly by regulating the circ_0037655/miR-130a-5p/RPN2 axis.

Identifying a novel IRF3/circUHRF1/miR-1306-5p/ARL4C axis in pancreatic ductal adenocarcinoma progression

Pancreatic ductal adenocarcinoma (PDAC) is considered one most aggressive and lethal cancer types worldwide. While its underlying mechanisms are still poorly understood. CircRNAs play essential roles in various biological progression, including PDAC. Here, our results found that circUHRF1 was highly expressed in PDAC tumor tissues compared with normal tissues. Next, Cell or animal models were constructed, CCK-8, cell colony, EdU, flow cytometry assay, transwell migration, and Western blot assays were applied. CircUHRF1 knockdown influenced PDAC cell proliferation, apoptosis, migration and EMT level in vitro, and tumor growth in vivo. Subsequently, bioinformatics analysis, AGO2-RIP, RNA pull-down, and dual-luciferase reporter assays were used to explore the downstream targets in PDAC progression. Our findings suggest that circUHRF1 regulated ARL4C expression to promote PDAC progression through sponging miR-1306-5p. The role of miR-1306-5p in PDAC cellular progression has been elucidated, and the expression association between miR-1306-5p and circUHRF1 or ARL4C in PDAC tissues was analyzed. Furthermore, circUHRF1 expression in PDAC cells could be transcriptionally regulated by IRF3. Collectively, our study demonstrated the role of IRF3/circUHRF1/miR-1306-5p/ARL4C axis in PDAC progression. Our results suggest that circUHRF1 is one promising diagnosis or therapeutic target for PDAC management.Abbreviations : CircRNA; Circular RNAPDAC; pancreatic ductal adenocarcinomaUHRF1; Ubiquitin-like with PHD and RING finger domain 1ARL4C; ADP Ribosylation Factor Like GTPase 4CRIP; RNA immunoprecipitationEDU; 5-Ethynyl-2'-deoxyuridineEMT; epithelial to mesenchymal transitionAGO2; Argonaute RISC Catalytic Component 2CCK8; Cell counting Kit-8IRF3; Interferon Regulatory Factor 3.

circular RNAs 0000515 and 0011385 as potential biomarkers for disease monitoring and determining prognosis in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is extremely fatal and potential biomarkers for precision medicine of patients with PDAC are yet to be elucidated. Moreover, the clinical values of circular RNAs (circRNAs) in PDAC management are yet to be investigated. The aim of the present study was to perform a secondary analysis of two PDAC public datasets (GSE69362 and GSE79634), to identify the candidate circRNAs, to validate the expression of these circRNAs, and to determine their association with the clinicopathological characteristics and survival of patients with PDAC. A total of 60 patients with PDAC were retrospectively reviewed in the present study. The expression levels of these candidate circRNAs were detected in PDAC tissues and paired adjacent normal tissues via reverse transcription-quantitative PCR analysis. In addition, the clinicopathological characteristics and overall survival (OS) of patients with PDAC were recorded. Bioinformatics analysis identified 22 overlapping differentially expressed (DE) circRNAs between the GSE69362 and GSE79634 datasets, among which nine DEcircRNAs with accordant expression trends (the DEcircRNAs that were upregulated or downregulated in tumor tissues compared with paired adjacent normal tissues in both datasets) were selected as candidate circRNAs, including circ_0000515, circ_0000517, circ_0000520, circ_0000514, circ_0011385, circ_0055033, circ_0072088, circ_0003528 and circ_0008514. In the 60 patients with PDAC, the expression levels of circ_0000515, circ_0000517, circ_0000520, circ_0000514, circ_0011385, circ_0055033, circ_0072088 and circ_0003528 were notably upregulated in PDAC tissues compared with paired adjacent normal tissues. Furthermore, circ_0000515, circ_0000520, circ_0000514, circ_0011385 and circ_0072088 were positively associated with T stage, N stage and/or TNM stage in patients with PDAC. Notably, circ_0000515 and circ_0011385 were negatively associated with OS in patients with PDAC. Taken together, the results of the present study suggest that circ_0000515 and circ_0011385 may serve as prognostic biomarkers for patients with PDAC.

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.

Circ_0007534 Silencing Inhibits the Proliferation, Migration and Invasion and Induces the Apoptosis of Glioma Cells Partly Through Down-Regulating PROX1 Via Elevating miR-22-3p Level

Glioma is a common malignant brain neoplasm. The role and mechanism of circular RNA 0,007,534 (circ_0007534) in glioma progression were investigated in this study. The expression of circ_0007534, microRNA-22-3p (miR-22-3p) and prospero homeobox protein 1 (PROX1) messenger RNA (mRNA) was determined by quantitative real-time polymerase chain reaction (qRT-PCR). The proliferation, migration and invasion abilities were analyzed by colony formation assay, transwell migration assay and transwell invasion assay. Cell apoptosis was assessed through measuring the activity of Caspase-3 using the Caspase-3 kit and the apoptosis rate using flow cytometry. Dual-luciferase reporter assay was used to confirm the target interaction between miR-22-3p and circ_0007534 or PROX1. The protein level of PROX1 was examined by Western blot assay. Animal studies were conducted to analyze the influence of circ_0007534 interference on xenograft tumor growth in vivo. Circ_0007534 was highly expressed in glioma tissues and cell lines relative to that in normal tissues and NHA cell line. Circ_0007534 knockdown suppressed the proliferation and motility while induced the apoptosis of glioma cells. Circ_0007534 negatively regulated miR-22-3p level through targeting it in glioma cells. Circ_0007534 interference-induced influences in glioma cells were partly overturned by the silencing of miR-22-3p. PROX1 was a target of miR-22-3p, and circ_0007534 interference-mediated effects in glioma cells were largely diminished by the overexpression of PROX1. Circ_0007534 interference restrained glioma development in vivo. Circ_0007534 aggravated glioma progression through elevating PROX1 expression via targeting miR-22-3p, which provided new targets for the diagnosis and treatment of glioma.

The Use of circRNAs as Biomarkers of Cancer

CircRNAs are a subclass of lncRNAs that have been found to be abundantly present in a wide range of species, including humans. CircRNAs are generally produced by a noncanonical splicing event called backsplicing that is dependent on the canonical splicing machinery, giving rise to circRNAs classified into three main categories: exonic circRNA, circular intronic RNA, and exon-intron circular RNA. Notably, circRNAs possess functional importance and display their functions through different mechanisms of action including sponging miRNAs, or even being translated into functional proteins. In addition, circRNAs also have great potential as biomarkers, particularly in cancer, thanks to their high stability, tissue type and developmental stage specificity, and their presence in biological fluids, which make them promising candidates as noninvasive biomarkers. In this chapter, we describe the most commonly used techniques for the study of circRNAs as cancer biomarkers, including high-throughput techniques such as RNA-Seq and microarrays, and other methods to analyze the presence of specific circRNAs in patient samples.

Non-Coding RNAs in Pancreatic Cancer Diagnostics and Therapy: Focus on lncRNAs, circRNAs, and piRNAs

Simple Summary

Pancreatic cancer is the seventh leading cause of cancer related death worldwide. In the United States, pancreatic cancer remains the fourth leading cause of cancer related death. The lack of early diagnosis and effective therapy contributes to the high mortality of pancreatic cancer. Therefore, there is an urgent need to find novel and effective biomarkers for the diagnosis and treatment of pancreatic cancer. Long noncoding RNA, circular RNAs and piwi-interacting RNA are non-coding RNAs and could become new biomarkers for the diagnosis, prognosis, and treatment of pancreatic cancer. We summarize the new findings on the roles of these non-coding RNAs in pancreatic cancer diagnosis, prognosis and targeted therapy.

Abstract

Pancreatic cancer is an aggressive malignance with high mortality. The lack of early diagnosis and effective therapy contributes to the high mortality of this deadly disease. For a long time being, the alterations in coding RNAs have been considered as major targets for diagnosis and treatment of pancreatic cancer. However, with the advances in high-throughput next generation of sequencing more alterations in non-coding RNAs (ncRNAs) have been discovered in different cancers. Further mechanistic studies have demonstrated that ncRNAs such as long noncoding RNAs (lncRNA), circular RNAs (circRNA) and piwi-interacting RNA (piRNA) play vital roles in the regulation of tumorigenesis, tumor progression and prognosis. In recent years, increasing studies have focused on the roles of ncRNAs in the development and progression of pancreatic cancer. Novel findings have demonstrated that lncRNA, circRNA, and piRNA are critically involved in the regulation of gene expression and cellular signal transduction in pancreatic cancer. In this review, we summarize the current knowledge of roles of lncRNA, circRNA, and piRNA in the diagnosis and prognosis of pancreatic cancer, and molecular mechanisms underlying the regulation of these ncRNAs and related signaling in pancreatic cancer therapy. The information provided here will help to find new strategies for better treatment of pancreatic cancer.

Increased levels of circulating circular RNA (hsa_circ_0013587) may serve as a novel biomarker for pancreatic cancer

Aim: Circular RNA can serve as a biomarker for early diagnosis of pancreatic cancer. Materials & methods: Analyzed the expression of various differentially expressed circular RNAs in the pancreatic cancer tissues by gene chip and identified the expression of hsa_circ_0013587 in pancreatic cancer cells, tissues and plasma by quantitative reverse transcription PCR (qRT-PCR). Results: Hsa_circ_0013587 was highly expressed in the pancreatic cancer tissues, cell lines and plasma samples from patients with pancreatic cancer. Notably, hsa_circ_0013587 was upregulated in pancreatic cancer patients with later clinical stages III-IV as compared with those detected in early clinical stages I-II. Conclusion: A high expression of hsa_circ_0013587 may serve as a novel diagnostic and therapeutic biomarker for pancreatic cancer.

Non-coding RNAs in pancreatic ductal adenocarcinoma: New approaches for better diagnosis and therapy

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies with a 5-year survival rate less than 8%, which has remained unchanged over the last 50 years. Early detection is particularly difficult due to the lack of disease-specific symptoms and a reliable biomarker. Multimodality treatment including chemotherapy, radiotherapy (used sparingly) and surgery has become the standard of care for patients with PDAC. Carbohydrate antigen 19-9 (CA 19-9) is the most common diagnostic biomarker; however, it is not specific enough especially for asymptomatic patients. Non-coding RNAs are often deregulated in human malignancies and shown to be involved in cancer-related mechanisms such as cell growth, differentiation, and cell death. Several micro, long non-coding and circular RNAs have been reported to date which are involved in PDAC. Aim of this review is to discuss the roles and functions of non-coding RNAs in diagnosis and treatments of PDAC.

The promoting effects of hsa_circ_0050102 in pancreatic cancer and the molecular mechanism by targeting miR-1182/NPSR1

Pancreatic cancer is one of the most lethal tumors across the world with an overall 5-year survival rate of 9%, and great efforts have been devoted in early diagnosis and treatment in the past decades. Competing endogenous RNAs are novel and specific regulatory mechanisms of gene expression, and researches have indicated its important roles in tumor regulation. In this study, we explored the circ-0050102 expression in pancreatic cancer and its impacts on tumor malignant phenotypes and further investigated the correlations among circ-0050102, miR-1182 and NPSR1. Results of real-time quantitative PCR showed that circ-0050102 expressed higher in pancreatic cancers compared with that in adjacent normal tissues. In cell functional experiment, downregulation of circ-0050102 could suppress cell proliferation, migration and invasion ability, boost cell apoptosis and arrest cell cycle in both PANC-1 and CFPAC-1 cells. Furthermore, allogeneic transplantation in nude mice was performed and results showed that the inhibition of circ-0050102 could slow down tumor formation in vivo. Mechanism research suggested that circ-0050102 could downregulate miR-1182, while miR-1182 could not influence the expression of circ-0050102, and miR-1182 could directly target at NPSR1 and suppress it. Moreover, circ-0050102 could reverse the effects of si-NPSR1 on pancreatic cancer cells. In conclusion, we identified that circ-0050102 played an important role in promoting pancreatic cancer by regulating the miR-1182/NPSR1 pathway.

Circular RNAs as novel potential biomarkers for pancreatic cancer

Pancreatic cancer (PaCa) is the fourth leading cause of cancer-related deaths in the United States, and the vast majority of these malignancies are pancreatic ductal adenocarcinomas (PDAC), but there is still a lack of early detection biomarkers for PaCa. Unlike linear RNAs, circRNAs form covalently closed continuous loops and can act as mammalian gene regulators. They may be diagnostic or predictive biomarkers for some tumors, also be novel potential therapeutic targets in different diseases. This review focuses on (1) the biogenesis of circRNAs, RNA binding proteins (RBPs) and complementary sequences of circRNAs; (2) the characteristics of circRNAs which allow them to interact with miRNAs; (3) the roles of circRNAs playing in the regulation of gene expression, cell behavior and cancer, and their potential role as novel biomarkers and therapeutic targets in pancreatic cancer.

Recent Advances in the Potential Use of Circular RNA for the Diagnosis and Treatment of Pancreatic Cancer

There are few biomarkers available for the early diagnosis and prognostic evaluation of pancreatic cancer. In addition, the development of targeted therapy for pancreatic cancer is an unmet need due to the lack of molecular targets. With the continuous progress in circular RNA (circRNA)-related research, its role in the occurrence and development of pancreatic cancer has been discovered and gradually recognized. Therefore, circRNA may represent a novel marker for early diagnosis of this disease and a focus of targeted clinical therapy. CircRNA is a type of non-coding RNA with a closed circular structure formed by covalent bonds. Some circRNAs can act as “sponges” to adsorb microRNAs (miRNAs) and play the role of competitive endogenous RNA (ceRNA) to remove their inhibitory effects on the target genes of miRNA. Thus, they can indirectly restore the expression of target genes. The circRNA–miRNA–mRNA network plays a regulatory role in the proliferation, invasion, metastasis, and other biological behaviors of pancreatic cancer. Given the recent advances in circRNA, this review seeks to provide an overview of the biological function of circRNA and highlights the recent research progress regarding the molecular mechanism of circRNA for the clinical diagnosis and treatment of pancreatic cancer.

Mechanisms of circular RNA circ_0066147 on pancreatic cancer progression

Background

The purpose of the study was to explore the precise parts of circ_0066147 (circular RNA [circRNA] scm-like with four mbt domains 1, circSFMBT1) in pancreatic cancer (PC) progression.

Methods

Ribonuclease R assay was used to confirm the stability of circ_0066147. circ_0066147, miR-326 and E2F transcription factor 2 (E2F2) expression levels was detected by quantitative reverse-transcription polymerase chain reaction or Western blot. Cell proliferation, apoptosis, migration and invasion abilities were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide, flow cytometry, wound-healing and transwell assays, respectively. Targeted relationships among circ_0066147, miR-326 and E2F2 were verified by the dual-luciferase reporter or RNA pull-down assay.

Results

circ_0066147 expression was upregulated in PC tissues and cells. circ_0066147 knockdown inhibited PC cell proliferation, migration, invasion and enhanced apoptosis in vitro, as well as weakened tumor growth in vivo. Mechanistically, circ_0066147 directly targeted miR-326 and circ_0066147 modulated E2F2 expression by miR-326. miR-326 mediated the regulation of circ_0066147 in PC cell behaviors in vitro. Furthermore, E2F2 was a functional target of miR-326 in modulating PC cell behaviors in vitro.

Conclusion

circ_0066147 regulated PC malignant progression in part depending on the miR-326/E2F2 axis, illuminating circ_0066147 was a potential prognostic marker and therapeutic target for PC management.

The diverse roles of circular RNAs in pancreatic cancer

Pancreatic cancer is one of the malignant tumors with poor prognosis. The molecular mechanisms of pancreatic oncogenesis and malignant progression are not fully elucidated. Several key signaling pathways, such as Notch, Wnt and hedgehog pathways, are important to drive pancreatic carcinogenesis. Recently, noncoding RNAs, especially circular RNAs (circRNAs), have been characterized to participate into pancreatic cancer development. Therefore, in this review article, we describe the association between circRNAs and pancreatic cancer prognosis. Moreover, we discuss how circRNAs are involved in regulation of cellular processes in pancreatic cancer, including proliferation, apoptosis, cell cycle, migration, invasion, EMT, metastasis, angiogenesis, drug resistance and immune escape. Furthermore, we mention that several compounds could regulate the expression of circRNAs, indicating that targeting circRNAs by compounds might be helpful for treating pancreatic cancer patients.

ChrXq27.3 miRNA cluster functions in cancer development

MicroRNAs (miRNAs) regulate the expression of their target genes post-transcriptionally; thus, they are deeply involved in fundamental biological processes. miRNA clusters contain two or more miRNA-encoding genes, and these miRNAs are usually coexpressed due to common expression mechanisms. Therefore, miRNA clusters are effective modulators of biological pathways by the members coordinately regulating their multiple target genes, and an miRNA cluster located on the X chromosome q27.3 region has received much attention in cancer research recently. In this review, we discuss the novel findings of the chrXq27.3 miRNA cluster in various types of cancer.

The chrXq27.3 miRNA cluster contains 30 mature miRNAs synthesized from 22 miRNA-encoding genes in an ~ 1.3-Mb region. The expressions of these miRNAs are usually negligible in many normal tissues, with the male reproductive system being an exception. In cancer tissues, each miRNA is dysregulated, compared with in adjacent normal tissues. The miRNA-encoding genes are not uniformly distributed in the region, and they are further divided into two groups (the miR-506-514 and miR-888-892 groups) according to their location on the genome. Most of the miRNAs in the former group are tumor-suppressive miRNAs that are further downregulated in various cancers compared with normal tissues. miR-506-3p in particular is the most well-known miRNA in this cluster, and it has various tumor-suppressive functions associated with the epithelial–mesenchymal transition, proliferation, and drug resistance. Moreover, other miRNAs, such as miR-508-3p and miR-509-3p, have similar tumor-suppressive effects. Hence, the expression of these miRNAs is clinically favorable as prognostic factors in various cancers. However, the functions of the latter group are less understood. In the latter group, miR-888-5p displays oncogenic functions, whereas miR-892b is tumor suppressive. Therefore, the functions of the miR-888–892 group are considered to be cell type- or tissue-specific.

In conclusion, the chrXq27.3 miRNA cluster is a critical regulator of cancer progression, and the miRNAs themselves, their regulatory mechanisms, and their target genes might be promising therapeutic targets.

CircRNA circ_0092314 Induces Epithelial-Mesenchymal Transition of Pancreatic Cancer Cells via Elevating the Expression of S100P by Sponging miR-671

Background

Circular RNAs (circRNAs) is a novel class of non-coding RNAs that regulate gene expression during cancer progression. Circ_0092314 is a newly discovered circRNA that was upregulated in pancreatic cancer (PAAD) tissues. However, the detailed functions and underlying mechanisms of circ_0092314 in PAAD cells remain unclear.

Methods

We first determined the expression of circ_0092314 in PAAD and normal tissues and further investigated the functional roles of circ_0092314 in regulating epithelial-mesenchymal transition (EMT) of PAAD cells. We also assessed the regulatory action of circ_0092314 on the microRNA-671 (miR-671) and its target S100P.

Results

Circ_0092314 was markedly upregulated in PAAD tissues and cells, and its overexpression was closely correlated with worse prognosis of PAAD patients. Functionally, circ_0092314 promotes proliferation, invasion and EMT in vitro and tumor growth in vivo. Mechanistically, we demonstrated that circ_0092314 directly binds to miR-671 and relieve its suppression of the downstream target S100P, which induces EMT and activates the AKT signaling pathway. The tumor-promoting effects caused by overexpression of circ_0092314 could be revered by re-expression of miR-671 in PAAD cells.

Conclusions

Overall, our study demonstrates that circ_0092314 exerts critical roles in promoting the EMT features of PAAD cells, and provides insight into how elevated expression of circ_0092314 might influence PAAD progression.

Repression of circRNA_000684 inhibits malignant phenotypes of pancreatic ductal adenocarcinoma cells via miR-145-mediated KLF5

BACKGROUND

Circular RNAs (circRNAs) are aberrantly expressed in pancreatic ductal adenocarcinoma (PDAC). In the current study, we investigated how circRNA_000684 affected the progression of PDAC, and how it regulated kruppel-like factor 5 (KLF5) and microRNA (miR)-145.

METHODS

Differentially expressed circRNAs, miRs and genes related to PDAC as well as their targeting relationship were predicted using bioinformatics analyses. Binding relationships among circRNA_000684, miR-145 and KLF5 were verified using dual-luciferase reporter gene assay, RIP and RNA pull-down assay, respectively. The effects of circRNA_000684, miR-145, KLF5 on the malignant phenotypes of PDAC cells and human umbilical vein endothelial cell (HUVEC) angiogenesis were assessed using loss- and gain-of function experiments by CCK-8 assay, scratch test, Transwell and tube formation assays. RT-qPCR and Western blot analysis were used to determine MCM2, MMP2 and MMP9 and VEGFA expression. In addition, the roles of circRNA_000684, miR-145, and KLF5 in tumor growth were validated through in vivo experiments.

RESULTS

Expression of CircRNA_000684 and KLF5 was upregulated, whereas miR-145 expression was downregulated in PDAC tissues and cells. CircRNA_000684 repression or miR-145 elevation inhibited the proliferation, invasion and migration of PDAC cells and HUVEC angiogenesis, as evidenced by lower levels of MCM2, MMP2 and MMP9 and VEGFA. CircRNA_000684 negatively regulated miR-145 expression, while miR-145 negatively regulated KLF5. In-vivo, circRNA_000684 elevation or miR-145 repression promoted tumor growth.

CONCLUSION

Taken together, the present study provided evidence clarifying that circRNA_000684 could downregulate miR-145 expression and elevate KLF5 to promote the progression of PDAC.

CircRNAs: a new target for the diagnosis and treatment of digestive system neoplasms

A circRNA is a type of endogenous noncoding RNA that consists of a closed circular RNA molecule formed by reverse splicing; these RNAs are widely distributed in a variety of biological cells. In contrast to linear RNAs, circRNAs have no 5′ cap or 3′ poly(A) tail. They have a stable structure, a high degree of conservation, and high stability, and they are richly and specifically expressed in certain tissues and developmental stages. CircRNAs play a very important role in the occurrence and progression of malignant tumors. According to their origins, circRNAs can be divided into four types: exon-derived circRNAs (ecRNAs), intron-derived circRNAs (ciRNAs), circRNAs containing both exons and introns (EIciRNAs) and intergenic circRNAs. A large number of studies have shown that circRNAs have a variety of biological functions, participate in the regulation of gene expression and play an important role in the occurrence and progression of tumors. In this paper, the structure and function of circRNAs are reviewed, along with their biological role in malignant tumors of the digestive tract, in order to provide a reference for the diagnosis and treatment of digestive system neoplasms.

Current State of "Omics" Biomarkers in Pancreatic Cancer

Pancreatic cancer is one of the most fatal malignancies and the seventh leading cause of cancer-related deaths related to late diagnosis, poor survival rates, and high incidence of metastasis. Unfortunately, pancreatic cancer is predicted to become the third leading cause of cancer deaths in the future. Therefore, diagnosis at the early stages of pancreatic cancer for initial diagnosis or postoperative recurrence is a great challenge, as well as predicting prognosis precisely in the context of biomarker discovery. From the personalized medicine perspective, the lack of molecular biomarkers for patient selection confines tailored therapy options, including selecting drugs and their doses or even diet. Currently, there is no standardized pancreatic cancer screening strategy using molecular biomarkers, but CA19-9 is the most well known marker for the detection of pancreatic cancer. In contrast, recent innovations in high-throughput techniques have enabled the discovery of specific biomarkers of cancers using genomics, transcriptomics, proteomics, metabolomics, glycomics, and metagenomics. Panels combining CA19-9 with other novel biomarkers from different "omics" levels might represent an ideal strategy for the early detection of pancreatic cancer. The systems biology approach may shed a light on biomarker identification of pancreatic cancer by integrating multi-omics approaches. In this review, we provide background information on the current state of pancreatic cancer biomarkers from multi-omics stages. Furthermore, we conclude this review on how multi-omics data may reveal new biomarkers to be used for personalized medicine in the future.

Down-regulation of circular RNA hsa_circ_0007534 suppresses cell growth by regulating miR-219a-5p/SOX5 axis in osteosarcoma

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The interaction between circ_0007534 and miR-219a-5p is confirmed for the first time.

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The interaction between miR-219a-5p and SOX5 is confirmed for the first time.

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Circ_0007534 knockdown inhibits the progression of osteosarcoma cells.

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Circ_0007534 regulates the growth of osteosarcoma cells through modulating miR-219a-5p/SOX5 axis.

Introduction

Circular RNA circ_0007534 and microRNA-219a (miR-219a-5p) were reported to be involved in osteosarcoma (OS) development. Osteosarcoma (OS) is one of the most common malignant bone tumors, which was more prone to occur in the metaphysis of long bones, including distal femur and proximal tibia. However, the detailed mechanisms were not fully clear. The purpose of this research was to reveal the functional mechanisms of circ_0007534 and miR-219a-5p in OS.

Methods

The levels of genes were determined by quantitative real-time polymerase chain reaction (qRT-PCR) or western blot assay. Cell proliferation ability was detected by cell counting kit-8 (CCK-8) and colony formation assay. Cell migration and invasion abilities were measured using the transwell assay. Furthermore, the interaction between miR-219a-5p and circ_0007534 or SRY (sex-determining region Y)-box 5 (SOX5) was predicted by starbaseV3.0, and confirmed by the dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Besides, tumor xenograft experiment was performed to analyze the effect of circ_0007534 depletion on tumor growth in vivo.

Results

The levels of circ_0007534 and SOX5 were increased, while the miR-219a-5p level was decreased in OS tissues and cells. Circ_0007534 knockdown repressed the proliferation, colony formation, migration, and invasion in OS cells. Circ_0007534 targeted miR-219a-5p, and miR-219a-5p interacted with SOX5. Furthermore, circ_0007534 regulated the growth of OS cells through modulating the levels of miR-219a-5p and SOX5.

Conclusion

Our finding demonstrated that circ_0007534 knockdown suppressed the growth of OS cells via regulating miR-219a-5p/SOX5 axis, providing a potential target for OS treatment and diagnosis.

Knockdown of circRNA_0007534 suppresses the tumorigenesis of cervical cancer via miR-206/GREM1 axis

BACKGROUND

Increasing evidence manifested that circular RNAs (circRNAs) acted as crucial regulators in human cancers by targeting the miRNA/mRNA axis, including cervical cancer (CC). Circ_0007534 was reported to promote CC cell proliferation and invasion by the miR-498/BMI-1 axis. The aim of this study was to explore a novel miRNA/mRNA network underlying circ_0007534 in CC regulation.

METHODS

The quantitative real-time polymerase chain reaction (qRT-PCR) was implemented to examine the levels of circ_0007534, miR-206 and Gremlin1 (GREM1). Cell viability was determined using MTT assay. BrdU and colony formation assays were performed for analyzing cell proliferation. Cell apoptosis was assessed by flow cytometry. The protein levels of GREM1 and apoptotic markers (Bcl-2, Bax, C-Caspase3) were measured via western blot. Cell invasion was detected by transwell assay. The target relationship was analyzed by dual-luciferase reporter assay. The impact of circ_0007534 on CC growth in vivo was ascertained by xenograft assay.

RESULTS

Circ_0007534 expression was aberrantly increased in CC tissues and cells. Functionally, knockdown of circ_0007534 reduced CC cell growth and invasion but motivated apoptosis. In the mechanism, circ_0007534 targeted miR-206 and its regulatory function was associated with sponging miR-206. Moreover, circ_0007534 was found to regulate GREM1 level by targeting miR-206. The inhibitory effect of si-circ_0007534 on the malignant progression of CC was reversed after GREM1 was overexpressed. Furthermore, circ_0007534 inhibition also reduced tumor growth of CC in vivo partially by regulating miR-206/GREM1 axis.

CONCLUSION

These results suggested that knockdown of circ_0007534 promoted the level of miR-206 to induce the expression downregulation of GREM1, consequently inhibiting the progression of CC.

Inhibition of chemotherapy-related breast tumor EMT by application of redox-sensitive siRNA delivery system CSO-ss-SA/siRNA along with doxorubicin treatment

Metastasis is one of the main reasons causing death in cancer patients. It was reported that chemotherapy might induce metastasis. In order to uncover the mechanism of chemotherapy-induced metastasis and find solutions to inhibit treatment-induced metastasis, the relationship between epithelial-mesenchymal transition (EMT) and doxorubicin (DOX) treatment was investigated and a redox-sensitive small interfering RNA (siRNA) delivery system was designed. DOX-related reactive oxygen species (ROS) were found to be responsible for the invasiveness of tumor cells in vitro, causing enhanced EMT and cytoskeleton reconstruction regulated by Ras-related C3 botulinum toxin substrate 1 (RAC1). In order to decrease RAC1, a redox-sensitive glycolipid drug delivery system (chitosan-ss-stearylamine conjugate (CSO-ss-SA)) was designed to carry siRNA, forming a gene delivery system (CSO-ss-SA/siRNA) downregulating RAC1. CSO-ss-SA/siRNA exhibited an enhanced redox sensitivity compared to nonresponsive complexes in 10 mmol/L glutathione (GSH) and showed a significant safety. CSO-ss-SA/siRNA could effectively transmit siRNA into tumor cells, reducing the expression of RAC1 protein by 38.2% and decreasing the number of tumor-induced invasion cells by 42.5%. When combined with DOX, CSO-ss-SA/siRNA remarkably inhibited the chemotherapy-induced EMT in vivo and enhanced therapeutic efficiency. The present study indicates that RAC1 protein is a key regulator of chemotherapy-induced EMT and CSO-ss-SA/siRNA silencing RAC1 could efficiently decrease the tumor metastasis risk after chemotherapy.

Circular RNA in pancreatic cancer: a novel avenue for the roles of diagnosis and treatment

Pancreatic cancer (PC), an important cause of cancer-related deaths worldwide, is one of the most malignant cancers characterized by a dismal prognosis. Circular RNAs (circRNAs), a class of endogenous ncRNAs with unique covalently closed loops, have attracted great attention in regard to various diseases, especially cancers. Compelling studies have suggested that circRNAs are aberrantly expressed in different cancer tissues and cell types, including PC. More specifically, circRNAs can modify the proliferation, progression, tumorigenesis and chemosensitivity of PC, and some circRNAs could serve as biomarkers for diagnosis and prognosis. Herein, we summarize what is currently known to be related to the biogenesis, functions and potential roles of human circRNAs in PC and their application prospects for PC clinical treatments.

Circ-ZDHHC5 Accelerates Esophageal Squamous Cell Carcinoma Progression in vitro via miR-217/ZEB1 Axis

Circular RNA (circRNA) exhibits a covalently closed circular conformation and is structurally stable. Nevertheless, the precise effects exerted by circRNA in esophageal squamous cell carcinoma (ESCC) remains uncertain. circRNA was ascertained by a human circRNA array study and was confirmed by the quantification of reverse transcriptase polymerase reactions. A luciferase reporter, fluorescence in situ hybridization experiment was exploited to explore the interaction between circ-ZDHHC5 and miR-217. The function of circ-ZDHHC5 was determined by siRNA-mediated knockout of circ-ZDHHC5 in in vitro proliferation, migration, and invasion. circ-ZDHHC5, rather than linear ZDHHC5 mRNA, rose in the tissues of patients with ESCC, plasma, and ESCC cell lines in comparison with normal controls. Knockdown of circ-ZDHHC5 inhibited tumorigenesis in ESCC cells, and the co-transfection of si-circ-ZDHHC5 and miR-217 mimics further enhanced the above effect. Noticeably, the present study showed that circ-ZDHHC5 was an miR-217 sponge that modulated the expression of zinc finger E-box binding homeobox 1 (ZEB1), further facilitating ESCC tumorigenesis. As revealed by this study, circ-ZDHHC5 can act as a new potential circular biomarker for detecting ESCC. It provides a novel perceptivity for the treatment of ESCC suggesting that circ-ZDHHC5 could impact on ESCC progression by sponging miR-217 with ZEB1.

Downregulation of long noncoding RNA SNHG14 suppresses cell proliferation and invasion by regulating EZH2 in pancreatic ductal adenocarcinoma (PDAC)

BACKGROUNDS

Previous studies have showed that long non-coding RNAs (lncRNAs) are critical regulators in many cancers. The aim of this study is to investigate the clinical role and functional effects of long non-coding RNA SNHG14 in pancreatic ductal adenocarcinoma (PDAC).

METHODS

The expression of SNHG14 in 58 pairs of pancreatic cancer tissues and adjacent normal tissues was detected by quantitative real-time PCR (qRT-PCR) analysis. The correlations between SNHG14 expression and PDAC patients' clinicopathological characteristics and prognosis were statistically assessed. Cell counting kit-8 (CCK8) and transwell cell invasion assays were employed to detect the capacities of cell proliferation and cell invasion. The western blot analysis was used to detected the expression of E-cadherin and Vimentin.

RESULTS

In the study, we found that SNHG14 expression was higher in PDAC tissue compared to adjacent normal tissues by qRT-PCR analysis. Higher SNHG14 expression was significantly associated with advanced TNM stage and positive lymph node metastasis in PDAC patients. Furthermore, we demonstrated that higher SNHG14 expression acted as a poor predictor in PDAC patients compared with lower SNHG14 expression. Moreover, we showed that higher SNHG14 expression promoted cell proliferation, cell colony formation and cell invasion ability in PDAC. Upregulation of SNHG14 expression promoted cell invasion by affecting E-cadherin expression via interacting with EZH2.

CONCLUSIONS

Thus, these results indicated that SNHG14 expression acts as a prognostic maker for PDAC and potential target of PDAC treatment.

CircDDX42 Accelerates the Development of Pancreatic Cancer via miR-613/ID4/PI3K/AKT Axis

Background

Pancreatic cancer (PC) is one of the fatal cancers globally. CircDEAD-box helicase 42 (circDDX42) has been reported to play an oncogenic role in many cancers. The purpose of our study was to explore the relationship between circDDX42 and PC development and the potential mechanism by which circDDX42 modulating the progression of PC.

Methods

The enrichment of circDDX42, miR-613 and inhibitor of DNA binding 4 (ID4) was determined by quantitative real-time polymerase chain reaction (qRT-PCR) in PC tissues and cells. The proliferation, apoptosis and metastasis of PC cells were examined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), Western blot, flow cytometry and transwell migration and invasion assays, respectively. The binding sites between miR-613 and circDDX42 or ID4 were predicted by Starbase bioinformatic software, and dual-luciferase reporter assay was conducted to verify the combination between miR-613 and circDDX42 or ID4. Western blot was carried out to detect the abundance of ID4, p-phosphatidylinositol 3-kinase (p-PI3K), PI3K, p-AKT serine/threonine kinase (p-AKT) and AKT in PC cells. The in vivo role of circDDX42 was verified through using murine xenograft model.

Results

The level of circDDX42 was enhanced in PC tissues and cells compared with that in matching normal tissues and HPDE cells. CircDDX42 promoted the proliferation and metastasis and suppressed the apoptosis of PC cells. CircDDX42 could sponge miR-613, and miR-613 was negatively regulated by circDDX42 in PC cells. MiR-613 suppressed the progression of PC. ID4 was a direct target of miR-613. ID4 was inversely modulated by miR-613 and positively regulated by circDDX42 in PC cells. ID4 played an oncogenic role in the tumorigenesis of PC. CircDDX42/miR-613/ID4 axis regulated the activation of PI3K/AKT pathway in PC cells. ID4 facilitated the progression of PC via activating PI3K/AKT signal pathway. CircDDX42 promoted the tumor growth of PC in vivo.

Conclusion

CircDDX42 accelerated the proliferation and metastasis while impeded the apoptosis of PC cells via circDDX42/miR-613/ID4/PI3K/AKT axis. This axis might be a promising target for PC therapy.

The Role of Circular RNAs in Pancreatic Ductal Adenocarcinoma and Biliary-Tract Cancers

Simple Summary

Pancreatic and biliary tract cancers often present with non-specific symptoms, resulting in diagnosis at a late stage. This may be too late for curative surgery. Earlier detection and characterisation may guide treatment options and increase survival. Natural “circles” of RNA (circRNAs) are shown to regulate cancer-related genes, and act as cancer “biomarkers”. Recent research has shown that circRNAs are both abundant and stable, both of which are desirable characteristics for clinically useful biomarkers. In this systematic review, we describe the roles of circRNAs in pancreatic and biliary tract cancers, summarise the current published research and explore their utility as a biomarker. A total of 32 articles were included: 22 considering Pancreatic Cancer, 7 for Bile Duct Cancer and 3 for Gallbladder Cancer. CircRNA proved an exciting prospect as a biomarker for these cancers and future work should continue to develop and expand this field of research.

Abstract

Pancreatic Ductal Adenocarcinoma (PDAC) and biliary-tract cancers (BTC) often present at a late stage, and consequently patients have poor survival-outcomes. Circular RNAs (circRNAs) are non-coding RNA molecules whose role in tumourigenesis has recently been realised. They are stable, conserved and abundant, with tissue-specific expression profiles. Therefore, significant interest has arisen in their use as potential biomarkers for PDAC and BTC. High-throughput methods and more advanced bioinformatic techniques have enabled better profiling and progressed our understanding of how circRNAs may function in the competing endogenous RNA (ceRNA) network to influence the transcriptome in these cancers. Therefore, the aim of this systematic review was to describe the roles of circRNAs in PDAC and BTC, their potential as biomarkers, and their function in the wider ceRNA network in regulating microRNAs and the transcriptome. Medline, Embase, Scopus and PubMed were systematically reviewed to identify all the studies addressing circRNAs in PDAC and BTC. A total of 32 articles were included: 22 considering PDAC, 7 for Cholangiocarcinoma (CCA) and 3 for Gallbladder Cancer (GBC). There were no studies investigating Ampullary Cancer. Dysregulated circRNA expression was associated with features of malignancy in vitro, in vivo, and ex vivo. Overall, there have been very few PDAC and BTC tissues profiled for circRNA signatures. Therefore, whilst the current studies have demonstrated some of their functions in these cancers, further work is required to elucidate their potential role as cancer biomarkers in tissue, biofluids and biopsies.

circEPSTI1 Acts as a ceRNA to Regulate the Progression of Osteosarcoma

BACKGROUND

Recent studies have reported the vital roles of circular RNAs (circRNAs) in tumor progression. However, the function and expression profile of most circRNAs in osteosarcoma remain unclear.

METHODS

We examined the expression of circEPSTI1, a circRNA, in 50 paired adjacent normal tissues and osteosarcoma tissues by qRT-PCR. Then, we further explored the function of circEPSTI1 in osteosarcoma progression in vitro and in vivo. For example, cell proliferation and migration were examined. Some experiments were performed to explore the regulatory function of circEPSTI1 in miRNA and to investigate the potential role of circEPSTI1 in osteosarcoma.

RESULTS

We found that circEPSTI1 was significantly upregulated in osteosarcoma. Inhibition of circEPSTI1 suppressed the osteosarcoma cancer cell proliferation and migration in vitro. Dual luciferase reporter assay showed that circEPSTI1 and MCL1 (myeloid cell leukaemia 1) could bind to miR-892b and that MCL1 and circEPSTI1 were targets of miR-892b.

CONCLUSION

Thus, the circEPSTI1-miR-892b-MCL1 axis affected osteosarcoma progression through the miRNA sponging mechanism. circEPSTI1 may serve as a target and biomarker for osteosarcoma treatment.

Non-coding RNA biomarkers in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies, which is usually diagnosed at an advanced stage. The late disease diagnosis, the limited availability of effective therapeutic interventions and lack of robust diagnostic biomarkers, are some of the primary reasons for the dismal 5-year survival rates (∼8%) in patients with PDAC. The pancreatic cancer develops through accumulation of a series of genomic and epigenomic alterations which lead to the transformation of normal pancreatic epithelium into an invasive carcinoma - a process that can take up to 15-20 years to develop, from the occurrence of first initiating mutational event. These facts highlight a unique window of opportunity for the earlier detection of PDAC, which could allow timely disease interception and improvement in the overall survival outcomes in patients suffering from this fatal malignancy. Non-coding RNAs (ncRNAs) have been recognized to play a central role in PDAC pathogenesis and are emerging as attractive candidates for biomarker development in various cancers, including PDAC. More specifically, the ncRNAs play a pivotal role in PDAC biology as they affect tumor growth, migration, and invasion by regulating cellular processes including cell cycle, apoptosis, and epithelial-mesenchymal transition. In this review, we focus on three types of well-established ncRNAs - microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) - and discuss their potential as diagnostic, prognostic and predictive biomarkers in PDAC.

Circular RNAs and cancer: Opportunities and challenges

Circular RNAs (circRNAs) are covalently circularized RNA moieties that despite being relatively abundant were only recently identified and have only begun to be investigated within the last couple of years. Even though there are many thousands of genes that appear capable of producing circRNAs, and the fact that many circRNAs appear to be highly evolutionarily conserved, the function of all but a few remain to be fully explored. What has been determined, however, is that circRNAs play key regulatory roles in many aspects of biology with focus being given to their function in cancer. Most of the studies to date have found that circRNAs act as master regulator of gene expression most often than not acting to regulate levels though sequestration or "sponging" of other gene expression regulators, particularly miRNAs. They can also function directly modulating transcription, or by interfering with splicing mechanisms. Some circRNAs can also be translated into functional proteins or peptides. A combination of tissue and developmental stage specific expression along with an innate resistance to RNAse activity means that circRNAs show perhaps their greatest potential as novel biomarkers of cancer. In this chapter we consider the current state of knowledge regarding these molecules, their synthesis, function, and association with cancer. We also consider some of the challenges that remain to be overcome to allow this emerging class of RNAs to fulfill their potential in clinical practice.