circFBXW7 Inhibits Malignant Progression by Sponging miR-197-3p and Encoding a 185-aa Protein in Triple-Negative Breast Cancer

Accumulating evidence indicates that circular RNAs (circRNAs) are vital regulators of various biological functions involved in the progression of multiple cancers. Circular F-box and WD repeat domain containing 7 (circFBXW7) (hsa_circ_0001451) has been reported to act as a tumor suppressor by encoding a novel protein in glioma; however, its functions and mechanisms in triple-negative breast cancer (TNBC) remain elusive. In the current study, we validated by qRT-PCR that circFBXW7 was downregulated in TNBC cell lines and found that low expression of circFBXW7 was associated with poorer clinical outcomes. circFBXW7 expression was negatively correlated with tumor size and lymph node metastasis, and it was an independent prognostic factor for TNBC patients. We performed cell proliferation, colony formation, transwell, wound-healing, and mouse xenograft assays to confirm the functions of circFBXW7. Overexpression of circFBXW7 obviously inhibited cell proliferation, migration, and tumor growth in both in vitro and in vivo assays. Luciferase reporter assays and RNA immunoprecipitation assays revealed that circFBXW7 serves as a sponge of miR-197-3p and suppresses TNBC growth and metastasis by upregulating FBXW7 expression. In addition, the FBXW7-185aa protein encoded by circFBXW7 inhibited the proliferation and migration abilities of TNBC cells by increasing the abundance of FBXW7 and inducing c-Myc degradation. In summary, our research demonstrated that circFBXW7 sponges miR-197-3p and encodes the FBXW7-185aa protein to suppress TNBC progression through upregulating FBXW7 expression. Thus, circFBXW7 may act as a therapeutic target and prognostic biomarker for TNBC.

LncRNAs in Ovarian Cancer Progression, Metastasis, and Main Pathways: ceRNA and Alternative Mechanisms

Ovarian cancer (OvCa) develops asymptomatically until it reaches the advanced stages with metastasis, chemoresistance, and poor prognosis. Our review focuses on the analysis of regulatory long non-coding RNAs (lncRNAs) competing with protein-coding mRNAs for binding to miRNAs according to the model of competitive endogenous RNA (ceRNA) in OvCa. Analysis of publications showed that most lncRNAs acting as ceRNAs participate in OvCa progression: migration, invasion, epithelial-mesenchymal transition (EMT), and metastasis. More than 30 lncRNAs turned out to be predictors of survival and/or response to therapy in patients with OvCa. For a number of oncogenic (CCAT1, HOTAIR, NEAT1, and TUG1 among others) and some suppressive lncRNAs, several lncRNA/miRNA/mRNA axes were identified, which revealed various functions for each of them. Our review also considers examples of alternative mechanisms of actions for lncRNAs besides being ceRNAs, including binding directly to mRNA or protein, and some of them (DANCR, GAS5, MALAT1, and UCA1 among others) act by both mechanisms depending on the target protein. A systematic analysis based on the data from literature and Panther or KEGG (Kyoto Encyclopedia of Genes and Genomes) databases showed that a significant part of lncRNAs affects the key pathways involved in OvCa metastasis, EMT, and chemoresistance.

Ferroptosis is involved in the progression of hepatocellular carcinoma through the circ0097009/miR-1261/SLC7A11 axis

Background

Circular RNAs (circRNAs) are a class of non-coding RNAs that have been demonstrated to play important roles in tumorigenesis. However, how circRNAs regulate the progression of hepatocellular cancer (HCC) remains unclear.

Methods

In the present study, circRNA microarray analyses were performed with HCC tissues to identify circRNAs that are differentially expressed. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis was conducted on HCC cell lines and tissues, and circ0097009 was found to be significantly upregulated. The functions of circ0097009 in HCC were investigated by a series of experiments, including cell proliferation, invasion, and mouse xenograft assays. Additionally, luciferase assays and RNA immunoprecipitation (RIP) assays were used to explore the interactions of circ0097009, microRNA-1261 (miR-1261), and solute carrier family 7 member 11 (SLC7A11) in HCC.

Results

Microarray analysis and qRT-PCR verified that circRNA, circ0097009, was significantly upregulated in HCC tissues and cell lines. Knockdown of circ0097009 inhibited the proliferation and invasion of HCC cells. Luciferase reporter assays showed that circ0097009 and SLC7A11 directly bound to miR-1261. Subsequent experiments showed that circ0097009 and SLC7A11 reciprocally regulated their expression via miR-1261 sponging by circ0097009.

Conclusions

Circ0097009 acts as a competing endogenous RNA to regulate the expression of SLC7A11, a key regulator of cancer cell ferroptosis, by sponging miR-1261 in HCC. Circ0097009 may be used as a diagnostic biomarker for HCC and as a potential target for HCC therapy.

circEPSTI1 regulates ovarian cancer progression via decoying miR-942

Increasing studies show that circular RNAs (circRNAs) play vital roles in tumour progression. But, how circRNAs function in ovarian cancer is mostly unclear. Here, we detected the expression of circEPSTI1 in ovarian cancer and explored the function of circEPSTI1 in ovarian cancer via a series of experiments. Then, we performed luciferase assay and RNA immunoprecipitation (RIP) assay to explore the competing endogenous RNA (ceRNA) function of circEPSTI1 in ovarian cancer. qRT-PCR verified that circEPSTI1 was overexpressed in ovarian cancer. Inhibition of circEPSTI1 suppressed ovarian cancer cell proliferation, invasion but promoted cell apoptosis. Luciferase assays and RIP assay showed that circEPSTI1 and EPSTI1 (epithelial stromal interaction 1) could directly bind to miR-942. And circEPSTI1 could regulate EPSTI1 expression via sponging miR-942. In summary, circEPSTI1 regulated EPSTI1 expression and ovarian cancer progression by sponging miR-942. circEPSTI1 could be used as a biomarker and therapeutic target in ovarian cancer.

Circular RNA circKIF4A facilitates the malignant progression and suppresses ferroptosis by sponging miR-1231 and upregulating GPX4 in papillary thyroid cancer

Circular RNAs (circRNAs) are one type of non-coding RNA. They act as important role in regulating various biological processes in the malignant progression. But we don't clearly know the specific mechanism of the majority circRNAs in papillary thyroid tumor progression. In the current study, we explored circKIF4A and the result showed that it had high expression in papillary thyroid cancer. The functions of circKIF4A were explored by CCK-8, transwell, and mouse xenograft experiments. Knockdown of circKIF4A could suppress papillary thyroid cell growth and migration. In addition, RIP assays and dual luciferase vector reporter assays were further conducted. Our consequence showed circKIF4A facilitated the malignant progress of papillary thyroid tumor by sponging miR-1231 and upregulating GPX4 expression. In conclusion, our study proved that circKIF4A-miR-1231-GPX4 axis played a vital role in cancer proliferation and ferroptosis by competing endogenous RNAs. Therefore, targeting circKIF4A is very likely to be a potential method for treatment of papillary thyroid cancer in the future.

circGNB1 Facilitates Triple-Negative Breast Cancer Progression by Regulating miR-141-5p-IGF1R Axis

As an intriguing class of RNA, circular RNAs (circRNAs) are vital mediators of various diseases including cancers. However, the biological role and underlying mechanism of the majority of circRNAs are still ambiguous in the progression of triple-negative breast cancer (TNBC). In this study, we characterized and further investigated hsa_circ_0009362 (circGNB1) by reanalyzing the circRNA microarray profiling in our previous study. Validating by qRT-PCR, circGNB1 was overexpressed in TNBC cell lines and high expression of circGNB1 was associated with worse clinical features and survival outcomes. The expression of circGNB1 was positively correlated with tumor size and clinical stage, and high expression of circGNB1 was an independent risk factor for TNBC patients. Cell proliferation, colony formation, wound-healing and mouse xenograft assays were carried out to investigate the functions of circGNB1. Both in vitro and in vivo assays revealed that knockdown of circGNB1 significantly suppressed cell proliferation, migration and tumor growth. Subsequently, we performed luciferase reporter assays and RNA immunoprecipitation assays to elucidate the underlying molecular mechanism of circGNB1. The results showed that circGNB1 sponges miR-141-5p and facilitates TNBC progression by upregulating IGF1R. Altogether, our study demonstrated the pivotal role of circGNB1-miR-141-5p-IGF1R axis in TNBC growth and metastasis though the mechanism of competing endogenous RNAs. Therefore, circGNB1 may have the potential to be a therapeutic target and novel prognostic biomarker for TNBC.

circGFRA1 Promotes Ovarian Cancer Progression By Sponging miR-449a

Backgroud: Increasing studies show that circular RNAs (circRNAs) play important roles in tumor progression. However, the function of circRNAs in ovarian cancer is mostly unclear. Methods: We detected the expression of circGFRA1 by quantitative real-time PCR (qRT-PCR) in 50 pairs of ovarian cancer tissues and adjacent normal tissues. Then, we explored the function of circGFRA1 in ovarian cancer progression, such as cell proliferation, apoptosis and invasion. Moreover, we performed luciferase reporter and RNA immunoprecipitation (RIP) assay to study the competing endogenous RNA (ceRNA) function of circGFRA1 in ovarian cancer progression. Results: qRT-PCR showed that circGFRA1 was overexpressed in ovarian cancer tissues. Inhibition of circGFRA1 suppressed cell proliferation and invasion, but induced cell apoptosis in ovarian cancer. Luciferase reporter and RIP assay revealed that circGFRA1 could regulate the expression of GFRA1 by sponging miR-449a. Conclusions: In summary, circGFRA1 regulated GFRA1 expression and ovarian cancer progression by sponging miR-449a. circGFRA1 could be a potential diagnostic biomarker and therapeutic target for ovarian cancer.

circFBXL5 promotes breast cancer progression by sponging miR-660

Increasing studies have revealed that circular RNAs (circRNAs) play important roles in cancer progression. However, the potential involvement of circRNAs in breast cancer metastasis to lung is not clear so far. In this study, we conducted circular RNA microarrays of primary breast cancer tissues and lung metastatic tissues. The results revealed that circFBXL5 (hsa_circ_0125597) up‐regulated the most in lung metastatic tissues. Survival analysis revealed that high levels of circFBXL5 correlated with worse outcome of breast cancer. Further experiments showed that knockdown of circFBXL5 inhibited breast cancer cell proliferation and migration to lung. Mechanism study showed that circFBXL5 acted as a sponge for miR‐660 and compete binding to miR‐660 with SRSF6, leading to increased expression of SRSF6. Collectively, our study highlighted the regulatory function of the circFBXL5/miR‐660/SRSF6 pathway in breast cancer progression, which could be potential therapeutic targets for breast cancer.

CircABCC2 Regulates Hepatocellular Cancer Progression by Decoying MiR-665

Background: Numerous studies have shown that circular RNAs (circRNAs) play vital roles in tumor progression. However, how circRNAs function in hepatocellular cancer (HCC) remains mostly unclear.

Methods: We analyzed HCC circRNA expression via a microarray, and the expression of an upregulated circRNA, circABCC2, was detected. We next explored the function of circABCC2 in HCC via a series of experiments. We performed RNA immunoprecipitation (RIP) and luciferase assays to explore the competing endogenous RNA (ceRNA) function of circABCC2 in HCC.

Results: qRT-PCR verified that circABCC2 was overexpressed in HCC. Inhibition of circABCC2 suppressed HCC cell proliferation and invasion, but promoted apoptosis. Luciferase assays and RIP showed that circABCC2 and ABCC2 could directly bind to miR-665 and that circABCC2 could regulate ABCC2 expression by sponging miR-665.

Conclusions: In summary, circABCC2 regulates ABCC2 expression and HCC progression by sponging miR-665. circABCC2 could be used as a biomarker and therapeutic target in HCC.

New Insights into the Role of miR-29a in Hepatocellular Carcinoma: Implications in Mechanisms and Theragnostics

Hepatocellular carcinoma (HCC) remains one of the most lethal human cancer globally. For advanced HCC, curable plan for advanced HCC is yet to be established, and the prognosis remains poor. The detail mechanisms underlying the progression of HCC tumorigenicity and the corruption of tumor microenvironment (TME) is complex and inconclusive. A growing body of studies demonstrate microRNAs (miRs) are important regulators in the tumorigenicity and TME development. Notably, mounting evidences indicate miR-29a play a crucial role in exerting hepatoprotective effect on various types of stress and involved in the progression of HCC, which elucidates their potential theragnostic implications. In this review, we reviewed the advanced insights into the detail mechanisms by which miR-29a dictates carcinogenesis, epigenetic program, and metabolic adaptation, and implicated in the sponging activity of competitive endogenous RNAs (ceRNA) and the TME components in the scenario of HCC. Furthermore, we highlighted its clinical significance in diagnosis and prognosis, as well as the emerging therapeutics centered on the activation of miR-29a.

circIQCH sponges miR-145 to promote breast cancer progression by upregulating DNMT3A expression

As a unique type of RNA, circular RNAs (circRNAs) are important regulators of multiple biological processes in the progression of cancer. However, the potential role of most circRNAs in breast cancer lung metastasis is still unknown. In this study, we characterized and further investigated circIQCH (hsa_circ_0104345) by analyzing the circRNA microarray profiling in our previous study. circIQCH was upregulated in breast cancer tissues, especially in the metastatic sites. CCK-8, transwell, wound-healing and mouse xenograft assays were carried out to investigate the functions of circIQCH. Knockdown of circIQCH inhibited breast cancer cell proliferation and migration to lung. Moreover, luciferase reporter assays and RNA immunoprecipitation assays were performed to elucidate the underlying molecular mechanism of circIQCH. The results showed that circIQCH sponges miR-145 and promotes breast cancer progression by upregulating DNMT3A. In summary, our study demonstrated the pivotal role of circIQCH-miR-145-DNMT3A axis in breast cancer growth and metastasis via the mechanism of competing endogenous RNAs. Thus, circIQCH could be a potential therapeutic target for breast cancer.

Identifying a Comprehensive ceRNA Network to Reveal Novel Targets for the Pathogenesis of Parkinson's Disease

Parkinson's disease (PD) is the second commonest progressive neurodegenerative disease worldwide. Increasing evidence reveals that non-coding RNAs play roles in the pathophysiological process of PD. The notion called competing endogenous RNAs (ceRNAs) network is used to describe the roles of non-coding RNAs. According to this theory, long non-coding RNAs (lncRNAs) act as microRNAs (miRNAs) sponges by miRNA response elements or miRNA binding sites to control the availability of endogenous miRNA for binding to their target mRNAs. This study aimed to construct a ceRNA network in PD, which might have the potential to clarify the pathogenesis of PD. We investigated differential expression (DE) lncRNAs and mRNAs in substantia nigra array data GSE7621 between PD patients and healthy controls from the Gene Expression Omnibus database. And we used starBase 2.0 and miRWalk 2.0 databases to predict miRNAs that have interactions with DElncRNAs and DEmRNAs. Based on DElncRNAs, DEmRNAs and predicted miRNAs, two ceRNA networks were constructed. The first one was based on lncRNA-miRNA interactions and miRNA-mRNA interactions that shared the same miRNAs that we predicted, on which function annotation and PPI analysis were performed to identify hub genes. Hereby the second ceRNA network was generated to explore the core section in the first ceRNA network and was validated in external datasets. As a result, we identified 31 DE lncRNAs and 1,828 DEmRNAs, and finally constructed the first ceRNA network associated with PD, including 9 lncRNAs, 18 miRNAs, and 185 mRNAs. mRNAs in the first ceRNA network focused on autophagy, DNA repair and vesicle transport, which were critical pathological processes in PD. Nineteen hub genes in the first ceRNA network identified through PPI analysis, the second ceRNA network was constructed to annotate the core part of the first one. Moreover, the core subnetwork was validated in external datasets, of which several nodes including FBXL7, PTBP2, and lncRNA NEAT1 were verified. In conclusion, a ceRNA network was constructed based on the differential expression profiles of whole substantia nigra tissues of normal and PD patients, and the network was subsequently identified which revealed its association with autophagy, DNA repair and vesicle transport. The core subnetwork of the ceRNA network was identified and validated in external data. Our findings offered novel insights into the roles of ceRNAs in the pathogenesis of PD and provided promising diagnostic biomarkers.

Brain-expressed 3'UTR extensions strengthen miRNA cross-talk between ion channel/transporter encoding mRNAs

Why protein-coding genes express transcripts with longer 3′untranslated regions (3′UTRs) in the brain rather than in other tissues remains poorly understood. Given the established role of 3′UTRs in post-transcriptional regulation of transcript abundance and their recently highlighted contributions to miRNA-mediated cross-talk between mRNAs, we hypothesized that 3′UTR lengthening enhances coordinated expression between functionally-related genes in the brain. To test this hypothesis, we annotated 3′UTRs of human brain-expressed genes and found that transcripts encoding ion channels or transporters are specifically enriched among those genes expressing their longest 3′UTR extension in this tissue. These 3′UTR extensions have high density of response elements predicted for those miRNAs that are specifically expressed in the human frontal cortex (FC). Importantly, these miRNA response elements are more frequently shared among ion channel/transporter-encoding mRNAs than expected by chance. This indicates that miRNA-mediated cross-talk accounts, at least in part, for the observed coordinated expression of ion channel/transporter genes in the adult human brain. We conclude that extension of these genes' 3′UTRs enhances the miRNA-mediated cross-talk among their transcripts which post-transcriptionally regulates their mRNAs' relative levels.

circ0101675 promotes malignant process via sponging miR-1278 and upregulating WNT3A/5A in non-small cell lung cancer

Circular RNAs (circRNAs) is one type of non-coding RNAs (ncRNAs) which have many roles in biological processes, as well as modulation intracellular gene expression modulation. Nonethless, the roles along with expression status of the most circRNAs in NSCLC (non-small cell lung cancer) remain unknown. Herein, we conducted a high-throughput microarray sequencing to identify abnormal expressed circRNAs. Circ0101675 was found upregulated in NSCLC cell lines and tissues. We carried out colony formation, transwell, CCK-8, and animal assays to investigate the functions of circ0101675. Silence of circ0101675 inhibited the migration and proliferation of NSCLC. To elucidate the mechanism, RNA immunoprecipitation assays along with luciferase enzyme reporter assays were further employed to explore the cross-talk between circ0101675 and other molecules. We discovered that circ0101675 facilitates the malignant process of growth and migration via sponging miR-1278 and upregulating WNT3A/5A expression. In conclusion, we revelaed the vital role of circ0101675-miR-1278-WNT3A/5A signaling in NSCLC progression via the competing endogenous RNAs mechanism. Therefore, circ0101675 can be used as a new and useful biomarker for monitoring and treating NSCLC.

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.

circ0093740 Promotes Tumor Growth and Metastasis by Sponging miR-136/145 and Upregulating DNMT3A in Wilms Tumor

As a research hotspot, circular RNAs (circRNAs) is one type of non-coding RNAs which have many different functions in biological processes. However, there is lack of study investigating the underlying molecular mechanism and the potential roles of circRNAs in Wilms tumor. We conducted a high-throughput microarray sequencing to screen differentially expressed circRNAs in Wilms tumor. A novel circRNA (circ0093740) was identified as a frequently upregulated circRNA in Wilms tumor cells and tissues. Suppression of circ0093740 remarkably inhibited the proliferation and migration ability in Wilms tumor, validated by several experiments. The molecular mechanism of circ0093740 was investigated by luciferase assays and RNA immunoprecipitation assays. The results revealed that circ0093740 promotes the growth and migration ability by sponging miR-136/145 and upregulating DNMT3A. In conclusion, our study discovered the biological role of the circ0093740-miR-136/145-DNMT3A axis in Wilms tumor growth and metastasis which is important for developing new treatment strategy.

Identification of modules and novel prognostic biomarkers in liver cancer through integrated bioinformatics analysis

Liver cancer is a common malignant tumor with poor prognosis. Due to the lack of specific clinical manifestations at early stages, most patients are already at advanced stages of the disease by the time of diagnosis. Identification of novel biomarkers for liver cancer may thus enable earlier detection, improving outcome. MicroRNAs (miRNAs) are small endogenous noncoding RNAs of 18–22 nucleotides in length, which have a regulatory role in the expression of target proteins. Increased evidence suggests that miRNAs are abnormally expressed in a variety of cancer malignancies. Here, we combined RNA sequencing data and clinical information from The Cancer Genome Atlas Liver Hepatocellular Carcinoma database for weighted gene coexpression network analysis to identify potential miRNA prognostic biomarkers. We constructed nine coexpression modules, allowing us to identify that miR‐105‐5p, miR‐767‐5p, miR‐1266‐5p, miR‐4746‐5p, miR‐500a‐3p, miR‐1180‐3p and miR‐139‐5p are significantly associated with liver cancer prognosis. We found that these miRNAs exhibit significant association with prognosis of patients with liver cancer and confirmed the expression of these miRNAs in liver cancer tissues. Multivariate Cox regression analysis showed that miR‐105‐5p and miR‐139‐5p may be considered as independent factors. In summary, here we report that seven miRNAs have potential value as prognostic biomarkers of liver cancer.

WGCNA Analysis Identifies Polycystic Ovary Syndrome-Associated Circular RNAs That Interact with RNA-Binding Proteins and Sponge miRNAs

Objective

Dysfunction of cumulus granulosa cells has been suggested as a contributor to abnormal folliculogenesis and the development of polycystic ovary syndrome (PCOS), but the underlying molecular mechanisms remain unclear. Recent studies indicate that circular RNAs (circRNAs) exert important roles for diseases. We aimed to screen crucial circRNAs of PCOS patients and predict their functions.

Methods

The high-throughput datasets of circRNAs (GSE145296), microRNAs (miRNAs; GSE72274) and messenger RNAs (mRNAs; GSE155489) in cumulus cells of PCOS patients and controls were collected from the Gene Expression Omnibus database. Differentially expressed circRNAs (DECs), miRNAs (DEMs) and protein-coding genes (DEGs) were identified by the limma method. The weighted correlation network analysis (WGCNA) was conducted using the DECs to mine PCOS-associated modules. Hub DECs in modules were defined as both of |gene significance| and |module membership| >0.8. The downstream effectors of hub DECs were predicted by constructing DEC-DEM-DEG ceRNA and DEC-RNA binding protein (RBP) networks. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed to explore the functions of circRNAs.

Results

A total of 3614 DECs, 3544 DEGs and 1469 DEMs were identified between PCOS and controls. WGCNA analysis yielded five PCOS-related modules, of which 190 DECs were hub circRNAs. Seventeen hub DECs, nine DEMs, and 315 DEGs were identified to construct the ceRNA network, while 56 hub DECs and two DEGs (MBNL2, RBPMS) constituted the circRNA-RBP network. Five hub DECs (hsa_circ_0063309, hsa_circ_0054275, hsa_circ_0056196, hsa_circ_0018108 and hsa_circ_0070987) were overlapped between ceRNA and DEC-MBNL2 regulatory networks and thus they may be pivotal for PCOS. Furthermore, hsa_circ_0099109 could interact with the RBP gene RBPMS. Function analyses showed these circRNAs were inflammation-, apoptosis- or steroidogenesis-related.

Conclusion

Aberrant expression of six circRNAs that function as RBP regulators or miRNA sponges may be possible mechanisms underlying the pathogenesis of PCOS by affecting apoptosis and steroidogenesis in cumulus cells.

[Long Non-Coding RNAs as Competitive Endogenous RNAs in Osteosarcoma]

It was more than twenty years ago that miRNAs were recognized as a new class of RNA, but the understanding of their regulatory role is just beginning to emerge. Furthermore, it was found that the function of miRNAs as "master regulators" can be controlled by other non-coding RNAs (ncRNAs), in particular, long ncRNAs (lncRNAs). The regulatory functions of lncRNAs have been indicated in tumors in various locations and, in particular, in osteosarcoma, the most common and most aggressive malignant bone disease in children during puberty. This review discusses studies about the role of lncRNAs in the regulation of gene expression by the competitive endogenous RNAs (ceRNAs) mechanism. Data from these publications confirm the involvement of lncRNAs in the major signaling pathways, such as Notch, PI3K/AKT, Wnt/β-catenin, JNK, and HIV/VEGF. For example, seven members of the SNHG family (small nucleolar RNA host gene) were shown to participate in the Notch and PI3K/AKT signaling pathways; moreover, several lncRNA/miRNA/mRNA regulatory axes were identified for nearly all members of this family. The functions of other multifunctional oncogenic lncRNAs are also discussed; in particular, six to ten such axes have been determined for TUG1, MALAT1, and XIST. Using the Gene Cards, KEGG, and Panther databases, the key signaling pathways were identified for the targets of these three multifunctional lncRNAs. Investigation of lncRNA function contributes to the development of new diagnostic and prognostic markers for the treatment of patients with osteosarcoma. According to the available data, interactions between ceRNAs, that is, miRNAs, mRNAs, and lncRNAs, represent a new form of gene expression regulation that is involved in various pathophysiological processes, including bone oncogenesis.

Identification and analysis of survival-associated ceRNA triplets in prostate adenocarcinoma

Prostate adenocarcinoma (PRAD) is one of the most common causes of cancer-associated mortality worldwide. Recent evidence has emphasized the role of competitive endogenous RNAs (ceRNA) in prostate cancer. However, the current understanding of the roles that ceRNAs play in survival-associated PRAD remains in its infancy. In the present study, a PRAD-specific ceRNA network was constructed by integrating long non-coding RNA (lncRNA)-microRNA (miRNA)-gene interactions using experimental and computational methods, as well as expression correlations from The Cancer Genome Atlas database. The topological features of the ceRNA network were then analyzed and the PRAD-risk lncRNAs were compared with non-risk lncRNAs within this network. It was revealed that PRAD-risk lncRNAs had a higher degree, closeness and betweenness centrality, but also had the shortest path length. Finally, 42 significant PRAD-survival-associated triplets were identified. Notably, these triplets may form a compacted subnetwork composed of only 25 nodes (5 miRNAs, 4 lncRNAs and 16 genes) and 32 edges, indicating that some nodes were involved in many triplets. Among this subnetwork, mir-21 indicated the highest degree centrality and was demonstrated to exert its oncogenic effects in prostate tumors by downregulating transforming growth factor β receptor 2 (TGFBR2). Two triplets (MIR22HG_hsa-mir-21_TGFBR2 and MIR22HG_hsa-mir-21_BCL2) were finally identified; not only were they significantly associated with PRAD survival but they also had the highest average degree in the identified subnetwork. The results from the present study provide further insights into the understanding of the potential roles and interactions of ceRNA triplets and potential prognosis markers for PRAD.

A Competing Endogenous RNA Network and an 8-lncRNA Prognostic Signature Identify MYO16-AS1 as an Oncogenic lncRNA in Bladder Cancer

Recently, growing evidence has shed light on the competitive endogenous RNAs (ceRNAs) activity of long noncoding RNAs (lncRNAs) in carcinogenesis and tumor progression. To better elucidate the regulatory mechanisms of lncRNA in muscle-invasive bladder cancer (MIBC), we identified aberrantly expressed mRNAs, lncRNAs, and miRNAs in tumor tissues by using RNA sequence profiles from The Cancer Genome Atlas. The MIBC-specific ceRNA network, including 58 lncRNAs, 22 miRNAs, and 52 mRNAs, was constructed and visualized in Cytoscape. Further, using the univariate and multivariate Cox regression model, we screened 8 lncRNAs (AC078778.1, LINC00525, AC008676.1, AP000553.1, SACS-AS1, AC009065.1, AC127496.3, and MYO16-AS1) to construct an lncRNA signature for predicting the overall survival of MIBC patients. Kaplan-Meier analysis and a receiver operating characteristic curve were applied to evaluate the performance of the signature. Real-time quantitative PCR analysis was carried out to test expression levels of the 8 lncRNAs in MIBC patient tissues. Transwell assays demonstrated that overexpressing MYO16-AS1 can enhance UMUC2 migration and invasion. Our study offers a novel lncRNA-correlated ceRNA model to better understand the molecular mechanisms involved in MIBC. In addition, we developed an independent 8-lncRNAs biomarker for prognostic prediction and identified MYO16-AS1 as an oncogenic lncRNA in bladder cancer.

circALPL Sponges miR-127 to Promote Gastric Cancer Progression by Enhancing MTDH Expression

Background: CircRNA plays an important role in cancer progression. However, the potential mechanism of circRNA in gastric cancer remains unknown. In this study, we aimed to investigate the specific mechanism of circALPL in gastric cancer. Methods: Using a high-throughput microarray, we found that circALPL was upregulated in gastric cancer cell lines. RT-qPCR was used to measure the circALPL expression level in gastric cell lines and tissue. Transwell, CCK-8, and metastasis assays were performed to learn the function after circALPL was inhibited. Results: circALPL downregulation suppresses the invasion and proliferation ability of gastric cancer cells. Additionally, the underlying pathway of circALPL was studied using luciferase reporter assays and RNA immunoprecipitation assays. The results showed that circALPL promotes gastric cancer progression by sponging miR-127, thus upregulating MTDH. Conclusion: The circALPL-miR-127-MTDH pathway plays a vital role in gastric cancer proliferation and metastasis. circALPL might be a new therapeutic target in gastric cancer.