Circ_0006404 Accelerates Prostate Cancer Progression Through Regulating miR-1299/CFL2 Signaling

Plasma Circular RNAs as Biomarkers for Breast Cancer

Breast cancer (BC) is currently the most common neoplasm, the second leading cause of cancer death in women worldwide, and is a major health problem. The discovery of new biomarkers is crucial to improve our knowledge of breast cancer and strengthen our clinical approaches to diagnosis, prognosis, and follow-up. In recent decades, there has been increasing interest in circulating RNA (circRNA) as modulators of gene expression involved in tumor development and progression. The study of circulating circRNAs (ccircRNAs) in plasma may provide new non-invasive diagnostic, prognostic, and predictive biomarkers for BC. This review describes the latest findings on BC-associated ccircRNAs in plasma and their clinical utility. Several ccircRNAs in plasma have shown great potential as BC biomarkers, especially from a diagnostic point of view. Mechanistically, most of the reported BC-associated ccircRNAs are involved in the regulation of cell survival, proliferation, and invasion, mainly via MAPK/AKT signaling pathways. However, the study of circRNAs is a relatively new area of research, and a larger number of studies will be crucial to confirm their potential as plasma biomarkers and to understand their involvement in BC.

Integrated Network Analysis of microRNAs, mRNAs, and Proteins Reveals the Regulatory Interaction between hsa-mir-200b and CFL2 Associated with Advanced Stage and Poor Prognosis in Patients with Intestinal Gastric Cancer

Intestinal gastric cancer (IGC) carcinogenesis results from a complex interplay between environmental and molecular factors, ultimately contributing to disease development. We used integrative bioinformatic analysis to investigate IGC high-throughput molecular data to uncover interactions among differentially expressed genes, microRNAs, and proteins and their roles in IGC. An integrated network was generated based on experimentally validated microRNA-gene/protein interaction data, with three regulatory circuits involved in a complex network contributing to IGC progression. Key regulators were determined, including 23 microRNA and 15 gene/protein hubs. The regulatory circuit networks were associated with hallmarks of cancer, e.g., cell death, apoptosis and the cell cycle, the immune response, and epithelial-to-mesenchymal transition, indicating that different mechanisms of gene regulation impact similar biological functions. Altered expression of hubs was related to the clinicopathological characteristics of IGC patients and showed good performance in discriminating tumors from adjacent nontumor tissues and in relation to T stage and overall survival (OS). Interestingly, expression of upregulated hub hsa-mir-200b and its downregulated target hub gene/protein CFL2 were related not only to pathological T staging and OS but also to changes during IGC carcinogenesis. Our study suggests that regulation of CFL2 by hsa-miR-200b is a dynamic process during tumor progression and that this control plays essential roles in IGC development. Overall, the results indicate that this regulatory interaction is an important component in IGC pathogenesis. Also, we identified a novel molecular interplay between microRNAs, proteins, and genes associated with IGC in a complex biological network and the hubs closely related to IGC carcinogenesis as potential biomarkers.

Depletion of circ_0088046 suppressed cell growth and motility of hepatocellular carcinoma via circ_0088046-miR-1299-RTKN2 ceRNA pathway

Circular RNAs (circRNAs) have been verified to be important modulators and therapeutic targets of human hepatocellular carcinoma (HCC). This study aims to explore the role and mechanism of circ_0088046 in HCC progression. Quantitative real-time polymerase chain reaction (qRT-PCR), western blot and immunohistochemistry assays were used to detect the mRNA and protein expression of circ_0088046, miR-1299, Rhotekin 2 (RTKN2), Bax, Bcl-2, E-cadherin and Ki-67. Cell proliferation was investigated by 5-Ethynyl-2'-deoxyuridine (EdU) assay and cell colony formation assay. Cell apoptosis rate was measured by flow cytometry. Transwell migration and invasion assays were adopted to assess cell migration and invasion. The molecular target relationship between miR-1299 and circ_0088046 or RTKN2 were analysed by dual-luciferase reporter assay and RNA immunoprecipitation assay. An animal experiment was conducted to demonstrate the effect of circ_0088046 on tumour formation in vivo. High levels of circ_0088046 and RTKN2, and low levels of miR-1299 were displayed in HCC tissues and cells. Circ_0088046 absence repressed cell proliferation, migration and invasion, but boosted apoptosis of HCC cells. MiR-1299 was a target of circ_0088046 and miR-1299 inhibitor restored circ_0088046 silencing-mediated inhibitory impacts on HCC cell malignancy. MiR-1299 could directly target RTKN2, and overexpressed RTKN2 rescued the suppressive effects caused by miR-1299 mimic. In addition, circ_0088046 silencing constrained tumour formation in vivo. Circ_0088046 contributed to HCC cell malignancy via modulating the miR-1299/RTKN2 axis.

CircEGFR reduces the sensitivity of pirarubicin and regulates the malignant progression of triple-negative breast cancer via the miR-1299/EGFR axis

Circular RNAs (circRNAs) have been found to be involved in cancer progression and chemotherapy sensitivity. However, the biological function of circRNAs in triple-negative breast cancer (TNBC) and its effect on the sensitivity to pirarubicin (THP) chemotherapy are still unclear. CircEGFR (hsa_circ_0080220) was screened and verified by bioinformatics analysis, proving it was highly expressed in TNBC cell lines, patient tissues, and plasma exosomes, and was associated with poor prognosis of patients. The expression level of circEGFR in patient tissue has potential diagnostic value to distinguish TNBC tissue from normal breast tissue. In vitro studies confirmed that overexpression of circEGFR promoted the proliferation, migration, invasion, and EMT of TNBC cells and decreased the sensitivity of THP treatment while silencing circEGFR showed the opposite effect. The circEGFR/miR-1299/EGFR pathway was cascaded and verified. CircEGFR regulated malignant progression of TNBC by regulating EGFR via sponging miR-1299. THP can inhibit the malignant phenotype of MDA-MB-231 cells by downregulating the expression of circEGFR. In vivo studies confirmed that overexpression of circEGFR can promote tumor growth and EMT and reduce tumor sensitivity to THP treatment. Silencing circEGFR inhibited the malignant progression of the tumor. These results revealed circEGFR is a promising biomarker for TNBC diagnosis, therapeutic and prognosis.

The function and mechanisms of action of circular RNAs in Urologic Cancer

Kidney, bladder, and prostate cancer are the three major tumor types of the urologic system that seriously threaten human health. Circular RNAs (CircRNAs), special non-coding RNAs with a stabile structure and a unique back-splicing loop-forming ability, have received recent scientific attention. CircRNAs are widely distributed within the body, with important biologic functions such as sponges for microRNAs, as RNA binding proteins, and as templates for regulation of transcription and protein translation. The abnormal expression of circRNAs in vivo is significantly associated with the development of urologic tumors. CircRNAs have now emerged as potential biomarkers for the diagnosis and prognosis of urologic tumors, as well as targets for the development of new therapies. Although we have gained a better understanding of circRNA, there are still many questions to be answered. In this review, we summarize the properties of circRNAs and detail their function, focusing on the effects of circRNA on proliferation, metastasis, apoptosis, metabolism, and drug resistance in kidney, bladder, and prostate cancers.

Hsa_circ_0001925 promotes malignant progression in triple-negative breast cancer via miR-1299/YY1 axis

BACKGROUND

Circular RNAs (circRNAs) are related to the pathogenesis and progression of triple-negative breast cancer (TNBC). The aim of this study was to investigate the role and mechanism of hsa_circ_0001925 in TNBC progression.

METHODS

Hsa_circ_0001925, microRNA (miR)-1299 and Yin Yang 1 (YY1) levels were examined in TNBC via reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot. Cell counting kit-8 (CCK-8), colony formation, 5-ethynyl-2'-deoxyuridine (EdU) staining, flow cytometry, wound healing assay and tube formation assay were conducted to estimate the effects of hsa_circ_0001925 on malignant phenotypes of TNBC tumors. Several protein levels were measured with western blot. The regulatory relationship between miR-1299 and hsa_circ_0001925 or YY1 was validated using a dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Xenograft assay was used to estimate the effect of hsa_circ_0001925 in TNBC in vivo.

RESULTS

Hsa_circ_0001925 and YY1 levels were upregulated, while miR-1299 abundance was downregulated in TNBC tissues and cells. Hsa_circ_0001925 silencing constrained cell proliferation, migration and angiogenesis whereas it promoted apoptosis in vitro, and hsa_circ_0001925 silencing significantly curbed xenograft tumor growth in vivo. Hsa_circ_0001925 acted as a miRNA sponge for miR-1299. Hsa_circ_0001925 decreased YY1 expression by sponging miR-1299. MiR-1299 downregulation alleviated the effects of hsa_circ_0001925 knockdown on BC progression. MiR-1299 interacted with the 3' untranslated region (3' UTR) of YY1, and YY1 overexpression partly reversed the effects of miR-1299 overexpression on BC progression.

CONCLUSION

Our findings showed that hsa_circ_0001925 mediated TNBC progression via regulating miR-1299/YY1 axis, providing a potential target for BC treatment.

Circular RNA circ_0005667 promotes cisplatin resistance of endometrial carcinoma cells by regulating IGF2BP1 through miR-145-5p

BACKGROUND

Circular RNA (circRNA) plays a significant role in cisplatin (DDP) resistance. The purpose of this study was to explore the role of circ_0005667 in DDP resistance of endometrial carcinoma (EC) cells.

METHODS

The expression of circular RNA circ_0005667, microRNA-145-5p (miR-145-5p) and insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1) in DDP-sensitive and DDP-resistant EC tissues and EC cells was determined by quantitative real-time PCR (qRT-PCR). The expression of apoptosis-related proteins, drug resistance-related proteins and IGF2BP1 proteins were detected by western blot. The half-maximal inhibitory concentration (IC50) of DDP was determined using a cell counting kit-8 (CCK-8) assay. For functional assays, cell proliferation, migration, invasion and cell apoptosis were determined using 5-ethynyl-2'-deoxyuridine (EdU) assay, wound healing assay, transwell assay and flow cytometry assay, respectively. The binding relationship between miR-145-5p and circ_0005667 or IGF2BP1 was verified by dual-luciferase reporter assay. A xenograft experiment was applied to clarify the functional role of circ_0005667 in vivo.

RESULTS

Levels of circ_0005667 and IGF2BP1 were markedly increased, whereas miR-145-5p was downregulated in DDP-resistant EC tissues and cells. The circ_0005667 deficiency could enhance DDP sensitivity, inhibit cell proliferation, migration and invasion and promote cell apoptosis in DDP-resistant EC cells in vitro. Mechanistically, circ_0005667 modulated IGF2BP1 expression through sponging miR-145-5p. In addition, miR-145-5p depletion attenuated circ_0005667 silencing-induced effects in EC cells. The regulation of miR-145-5p in DDP resistance involved low IGF2BP1 expression. In vivo experiments revealed that circ_0005667 silencing could improve the sensitivity of the tumor to DDP.

CONCLUSION

Circ_0005667 enhanced DDP resistance in EC by elevating IGF2BP1 through sponging miR-145-5p.

Circular RNA circ_0079593 facilitates glioma development via modulating miR-324-5p/XBP1 axis

Glioma is a common brain tumor with high mortality. Circular RNAs (circRNAs) play crucial roles in tumor occurrence and development. However, the function and molecular basis of circ_0079593 in glioma remain unknown. Quantitative real-time PCR (qPCR) and Western blot were used for expression determination of circ_0079593, microRNA-324-5p (miR-324-5p) and X-box binding protein 1 (XBP1). Cell Counting Kit-8 (CCK-8), colony formation, flow cytometry, transwell assays, and tube formation assay were employed to evaluate cell functions. Glycolysis was determined via detecting glucose consumption, lactate production and ATP level. The binding relationship between miR-324-5p and circ_0079593 or XBP1 was validated by dual-luciferase reporter assay and RNA Immunoprecipitation (RIP) assay. Besides, xenograft assay was applied to test tumor growth in vivo. Circ_0079593 and XBP1 levels were elevated, while miR-324-5p level was declined in glioma. Silencing of circ_0079593 restrained proliferation, mobility, angiogenesis and glycolysis and induced apoptosis in glioma cells. Circ_0079593 accelerated glioma progression via sequestering miR-324-5p, one of the targets of circ_0079593. XBP1 was a target gene of miR-324-5p, and miR-324-5p alleviated the malignant growth of glioma by repressing XBP1. Furthermore, silence of circ_0079593 hindered tumor growth in vivo. Circ_0079593 contributed to the malignant evolution of glioma via modulating miR-324-5p and downstream XBP1 gene, suggesting that circ_0079593 might be a promising therapeutic target for glioma. Circ_0079593 was boosted in glioma. Circ_0079593 depletion restrained glioma progression. Circ_0079593 triggered glioma development via miR-324-5p/XBP1 axis. Circ_0079593 silence suppressed glioma tumorigenesis in vivo.

Circ_0006404 enhances hepatocellular carcinoma progression by regulating miR-624

Growing studies have demonstrated that circRNAs (circular RNAs) act potential roles in tumor metastasis and progression. However, the expression and function of circ_0006404 in hepatocellular carcinoma (HCC) remain to be investigated. The expression of circ_0006404 and miR-624 was detected by qRT-PCR. CCK-8 assay, flow cytometry, and wound healing were performed to determine cell proliferation, cycle, and migration. The target of circ_0006404 was studied by bioinformatics and luciferase activity analysis. Our data indicated that circ_0006404 was overexpressed in HCC specimens and cells and ectopic expression of circ_0006404 increased HCC cell growth, cycle, and migration. Moreover, we showed that miR-624 was downregulated in HCC specimens and cells and miR-624 expression was negatively correlated with circ_0006404 expression in HCC specimens. Circ_0006404 sponged miR-624 in HCC cell, and the overexpression of circ_0006404 suppressed miR-624 expression in HCC cell. Furthermore, circ_0006404 induced HCC cell growth, cycle, and migration via regulating miR-624. These results elucidated that circ_0006404 facilitated HCC progression and might act as one new biomarker for this carcinoma.

Serum hsa_circ_0079480 is a novel prognostic marker for acute myeloid leukemia

Background

The dysregulated expression of serum circular RNAs (circRNAs) has previously been linked to the prognosis of acute myeloid leukemia (AML) patients, but the clinical and prognostic relevance of serum hsa_circ_0079480 levels in this oncogenic setting have yet to be established. Herein, we assessed the putative prognostic relevance of circulating hsa_circ_0079480 levels in AML patient serum.

Methods

Serum was prepared from blood samples collected from 236 AML patients and 160 healthy controls, with hsa_circ_0079480 levels therein being quantified by quantitative real‐time reverse transcription‐polymerase chain reaction (qRT‐PCR) after which the clinical value of these levels was assessed.

Results

Acute myeloid leukemia patients were found to exhibit significant hsa_circ_0079480 upregulation in their serum as compared to serum from healthy controls, with such upregulation being most profound in individuals with M4/M5 type disease and to be more common in patients with poor cytogenic risk or high white blood cell counts. Receiver operating characteristic (ROC) curves demonstrated that serum hsa_circ_0079480 levels were able to effectively differentiate between patients with AML and healthy controls. Moreover, the upregulation of serum hsa_circ_0079480 was found to be closely related to clinicopathological findings and to be an independent predictor of reduced overall and relapse‐free survival among individuals diagnosed with AML. Furthermore, serum hsa_circ_0079480 levels were markedly decreased after treatment in this patient population, with these levels being lower in patients that achieved complete remission as compared to those patients that did not.

Conclusion

Levels of hsa_circ_0079480 in patient serum may offer value as a prognostic biomarker in AML.

Circ_0076305 facilitates prostate cancer development via sponging miR-411-5p and regulating PGK1

Abnormal expression of circular RNA (circRNA) is tightly linked to cancer progression. In this study, we aimed to investigate the biological role of circ_0076305 in prostate cancer (PCa). RT-qPCR was utilized to examine circ_0076305, microRNA-411-5p (miR-411-5p) and phosphoglycerate kinase 1 (PGK1) expression in PCa tissues and cells. CCK-8 assay, EdU assay, wound-healing assay and flow cytometry were executed to investigate the regulatory function of circ_0076305 on the proliferation, migration and apoptosis of PCa cells. Western blot (WB) assay was applied for measuring the protein levels. The effect of circ_0076305 on cellular glycolysis was examined using commercial kits. RNA immunoprecipitation (RIP) and dual-luciferase reporter assays were conducted for confirming the association between miR-411-5p and circ_0076305 or PGK1. The role of circ_0076305 in vivo was detected via establishing mice xenograft model. Circ_0076305 was highly expressed in PCa. Circ_0076305 silencing could repress cell growth, migration and glycolysis while triggered apoptosis in PCa cells. MiR-411-5p was targeted by circ_0076305, and miR-411-5p suppression counteracted the influence of circ_0076305 silencing in PCa cells. Additionally, miR-411-5p directly targeted PGK1, and miR-411-5p upregulation restrained PCa cell malignant behaviours via reducing PGK1. Mechanically, circ_0076305 sponged miR-411-5p to affect PGK1 expression. Importantly, circ_0076305 interference inhibited tumour growth in vivo. Circ_0076305 served as a novel oncogene PCa progression through regulation of miR-411-5p/PGK1 axis.

Circular RNA circ_0062019 exerts oncogenic properties in prostate cancer via mediating miR-1253/NRBP1 axis

Circular RNAs (circRNAs) participate in the progression of various cancers. However, the function of circ_0062019 in prostate cancer (PCa) remains unclear. In this study, CCK-8, colony formation, transwell, tube formation and flow cytometry assays were applied to assess cell proliferation, motility, angiogenesis, cell cycle distribution and apoptosis. The binding association between miR-1253 and circ_0062019 or NRBP1 was verified through dual-luciferase reporter assay and RIP assay. Xenograft assay was conducted to evaluate tumour formation in vivo. As a result, circ_0062019 and NRBP1 were increased, but miR-1253 was decreased in PCa. Depletion of circ_0062019 curbed cell proliferation, migration, invasion, angiogenesis and EMT and induced apoptosis in PCa cells. Circ_0062019 facilitated the malignancy of PCa cells via sequestering miR-1253. Simultaneously, miR-1253 hindered PCa cell progression via regulating NRBP1. Ccirc_0062019 silencing suppressed tumour growth in vivo. Taken together, circ_0062019 expedited PCa progression through mediating miR-1253/NRBP1 pathway.

The Role and Clinical Potentials of Circular RNAs in Prostate Cancer

Globally, prostate cancer (PCa) is the second most commonly diagnosed cancer in men globally. Early diagnosis may help in promoting survival in the affected patients. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) which have been found to show extensive dysregulation in a handful of human diseases including cancers. Progressions in RNA identification techniques have provided a vast number of circRNAs exhibiting either up-regulation or down-regulation in PCa tissues compared to normal adjacent tissues. The mechanism of action is not clear for most of dysregulated circRNAs. Among them, function of a number of newly identified dysregulated circRNAs have been assessed in PCa cells. Increase in cell proliferation, migration, invasion, and metastasis have been reported for up-regulated circRNAs which suggest their role as oncogenes. On the other hand, down-regulated circRNAs have shown tumor suppressing actions in experimental studies. Furthermore, in a majority of studies, circRNAs have been found to sponge microRNAs (miRNAs), negatively regulating expression or activity of the downstream miRNAs. Additionally, they have been identified in interaction with regulatory proteins. This axis consequently regulates a signaling pathway, a tumor suppressor, or an oncogene. Easy, quick, and reliable detection of circRNAs in human body fluids also suggests their potentials as biomarker candidates for diagnosis and prediction of prognosis in PCa patients. In this review, we have discussed the role and potentials of a number of dysregulated circRNAs in PCa.

Circ-METTL15 contributes to the proliferation, metastasis, immune escape and restrains apoptosis in lung cancer by regulating miR-1299/PDL1 axis

BACKGROUND

Circular RNAs (circRNAs) are important regulators in the pathogenesis of lung cancer. The study aims to explore the function and mechanism of circRNA methyltransferase-like 15 (circ-METTL15) in lung cancer development.

METHODS

The expression of circ-METTL15, miR-1299 and programmed death-ligand 1 (PDL1) were investigated by qRT-PCR assay. Cell viability, colony formation, cell proliferation and invasion were determined by MTT, colony formation, EDU incorporation and transwell assays, respectively. Cell apoptosis was attested by flow cytometry and TUNEL assays. Interferon-γ (IFN-γ) and Tumour Necrosis Factor-α (TNF-α) production were tested by enzyme-linked immunosorbent assay (ELISA), and the survival rate of cancer cells was assessed by cytotoxicity analysis. The protein expression was examined by western blot or immunohistochemistry (IHC) assay. The interaction between miR-1299 and circ-METTL15 or PDL1 was confirmed via dual-luciferase reporter assay. Xenograft models were established in mice to explore the role of circ-METTL15 in tumour growth in vivo.

RESULTS

Circ-METTL15 was upregulated in lung cancer tissues and cells. Circ-METTL15 silencing suppressed cell proliferation, colony formation, invasion, immune escape and promoted cell apoptosis in lung cancer cells. Circ-METTL15 was a sponge of miR-1299, and it could exert regulatory function in lung cancer via miR-1299. Furthermore, PDL1 was a functional target of miR-1299, and miR-1299 inhibited lung cancer cell development via decreasing PDL1 expression. Moreover, circ-METTL15 controlled PDL1 expression by acting as a sponge of miR-1299. Besides, circ-METTL15 downregulation blocked lung cancer tumour growth in vivo by regulating the miR-1299/PDL1 axis.

CONCLUSION

Circ-METTL15 promoted lung cancer malignant progression at least partly through modulating PDL1 by sponging miR-1299.

Lysine 2-hydroxyisobutyrylation proteomics reveals protein modification alteration in the actin cytoskeleton pathway of oral squamous cell carcinoma

As the most commonplace malignant carcinoma in the oral cavity, oral squamous cell carcinoma (OSCC) is highly invasive and prone to recurrence. The nosogenesis of OSCC are affected by epigenetics. Recently, a newly-found post-translational modification of lysine, 2-hydroxyisobutylation (Khib), has been proved to play a critical role in biological regulation. However, no research has evaluated the mechanism of Khib in oral cancer. Here, we performed liquid chromatography-mass spectrometry-based quantitative proteomics combined with bioinformatics analysis to reveal and evaluate Khib protein alterations in OSCC. Numerous proteins in OSCC undergo up-regulated modification of Khib. We quantified and identified 967 proteins with differential expression levels, and 617 2-hydroxyisobutylated proteins with 938 Khib sites. Among them, 125 proteins both differentially expressed and accompanied by obvious Khib modification were further identified and analyzed through KEGG-based and ingenuity pathway analysis (IPA). These proteins are enriched in the actin cytoskeleton regulatory pathway, and IPA predicted that they alter the state of actin aggregation and stability, hence impacting and regulating the actin cytoskeleton in OSCC. This is the first 2-hydroxyisobutylated modification proteomics performed for OSCC. Khib protein is significantly concentrated in the actin cytoskeleton regulatory pathway, indicating that this pathway may mediate the tumorigenesis or exacerbation of OSCC. SIGNIFICANCE: This is the first study that revealed the alterations of Khib protein in oral squamous cell carcinoma through LC-MS/MS-based modified proteomic. Our data showed that the protein in the actin cytoskeleton regulatory pathway was underwent significant Khib modification and abundance changes. We applied predictive function in IPA software to analyze and clarify that the aggregation of actin and the regulation of actin stability that mediated by the actin cytoskeleton regulatory pathway may be the potential mechanism of the occurrence and development of oral squamous cell carcinoma. Our research broadens the understanding of the pathogenesis of oral squamous cell carcinoma and provides new insights for future research.

The Emerging Role of Circular RNAs in Prostate Cancer: A Systematic Review

Prostate cancer is one of the most common malignant tumors that threaten the health of men. It is urgent to explore new molecular targets and develop new drugs for the treatment of prostate cancer. Circular RNAs (circRNAs) are aberrantly expressed in various malignant tumors. The dysregulated circRNAs are involved in the metastasis, tumor growth, drug resistance, and immunosuppression of malignant tumors. The present review systematically summarized publications concerning the biological implications of circRNAs in prostate cancer. The PubMed and Web of Science databases were used to retrieve publications concerning circRNAs and prostate cancer until June 16, 2021. The following keywords were used in the literature search: (circRNA OR circular RNA) AND prostate cancer. 73 publications were enrolled in the present systematic review to summarize the role of circRNAs in prostate cancer. The dysregulated and functional circRNAs were involved in the cell cycle, proliferation, migration, invasion, metastasis, drug resistance and radiosensitivity of prostate cancer. In addition, circRNAs could function through EVs and serve as prognostic and diagnostic biomarkers. Certain circRNAs were correlated with clinicopathological features of prostate cancer. A comprehensive review of the molecular mechanism of the tumorigenesis and progression of prostate cancer may contribute to the development of new therapies of prostate cancer in the future.

Hsa_circRNA_100146 Promotes Prostate Cancer Progression by Upregulating TRIP13 via Sponging miR-615-5p

Objective: This study was conducted for investigating the functions of circular RNA circRNA_100146 (circRNA_100146) in the development of prostate cancer (PCa) and identifying the underlying mechanisms of the circRNA_100146/miR-615-5p/TRIP13 axis. Materials and Methods: Under the support of RT-PCR, the expression of circRNA_100146 in PCa cells was examined. Cell Counting Kit-8 (CCK-8) assays and clone formation assays were applied to the assessment of cell proliferation. We then determined cell invasion and migration through transwell assays and wound healing assays. RNA pull-down assays and luciferase reporter assays were performed for the exploration of the regulatory effects of potential molecules on the expressions of the targeting genes. In addition, a nude mouse xenograft model was applied to demonstrate the oncogenic roles of circRNA_100146 in PCa. Results: CircRNA_100146 expression was distinctly upregulated in PCa cells. Silencing of circRNA_100146 suppressed PCa cells' invasion, migration, and proliferation. CircRNA_100146 sponged miR-615-5p to suppress its expressions, while miR-615-5p targeted the 3'-UTR of TRIP13 to repress the expression of TRIP13. In addition, we observed that knockdown of miR-615-5p reversed the suppression of circRNA_100146 silence on the proliferation and invasion of PCa cells. In addition, the tumor growth was also suppressed by silencing circRNA_100146 in vivo. Conclusion: CircRNA_100146 is a tumor promoter in PCa, which promoted progression by mediating the miR-615-5p/TRIP13. CircRNA_100146 can be a potential candidate for targeted therapy of PCa.

The Emerging Roles of circFOXO3 in Cancer

Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs which are mainly formed by reverse splicing of precursor mRNAs. They are relatively stable and resistant to RNase R because of their covalently closed structure without 5' caps or 3' poly-adenylated tails. CircRNAs are widely expressed in eukaryotic cells and show tissue, timing, and disease specificity. Recent studies have found that circRNAs play an important role in many diseases. In particular, they affect the proliferation, invasion and prognosis of cancer by regulating gene expression. CircRNA Forkhead box O3 (circFOXO3) is a circRNA confirmed to be abnormally expressed in a variety of cancers, including prostate cancer, hepatocellular carcinoma, glioblastoma, bladder cancer, and breast cancer, etc. At present, the feature of circFOXO3 as a molecular sponge is widely studied to promote or inhibit the development of cancers. However, the diverse functions of circFOXO3 have not been fully understood. Hence, it is important to review the roles of circFOXO3 in cancers. This review has summarized and discussed the roles and molecular mechanism of circFOXO3 and its target genes in these cancers, which can help to enrich our understanding to the functions of circRNAs and carry out subsequent researches on circFOXO3.