Circular RNA ZNF609 Promoted Hepatocellular Carcinoma Progression by Upregulating PAP2C Expression via Sponging miR-342-3p

Serum hsa_circ_0000615 is a prognostic biomarker of sorafenib resistance in hepatocellular carcinoma

BACKGROUND

Circular RNAs (circRNAs) can shape tumor progression and chemoresistance. How specific circRNAs shape hepatocellular carcinoma (HCC) chemoresistance, however, remains to be fully elucidated.

METHODS

In total, serum samples were collected from 202 HCC patients that had completed four sorafenib chemotherapy cycles. Serum hsa_circ_0000615 levels in these patients were quantified via quantitative real-time polymerase chain reaction (qRT-PCR), with demographic details and survival outcomes being recorded for subsequent analyses.

RESULTS

We found hsa_circ_0000615 to be significantly upregulated in chemoresistant HCC patients relative to chemosensitive patients, with such upregulation being positively correlated with disease stage. Moreover, the area under the curve (AUC) value for hsa_circ_0000615 was moderately good, and high levels of hsa_circ_0000615 expression were associated with shorter overall survival among chemoresistant HCC patients.

CONCLUSION

Our results highlight hsa_circ_0000615 as a promising driver of sorafenib resistance in HCC patients, highlighting it as a promising target for the treatment of this deadly cancer type.

Emerging Roles of Circ-ZNF609 in Multiple Human Diseases

Circular RNAs (circRNAs) are a special type of endogenous RNAs with extensive roles in multiple human diseases. They are formed by back-splicing of partial sequences of the parental precursor mRNAs. Unlike linear RNAs, their covalently closed loop structure without a 5′ cap and a 3′ polyadenylated tail confers on them high stability and they are difficult to be digested by RNase R. Increasing evidence has proved that aberrant expressions of many circRNAs are detected and that circRNAs exert essential biological functions in disease development and progression via acting as a molecular sponge of microRNA, interacting with proteins as decoys or scaffolds, or self-encoding small peptides. Circular RNA zinc finger protein 609 (circ-ZNF609) originates from exon2 of ZNF609, which is located at chromosome 15q22.31, and it has recently been proved that it can translate into a protein. Being aberrantly upregulated in various diseases, it could promote malignant progression of human tumors, as well as tumor cell proliferation, migration, and invasion. Here in this review, we concluded the biological functions and potential mechanisms of circ-ZNF609 in multiple diseases, which could be further explored as a targetable molecule in future accurate diagnosis and prognosis.

Circular RNAs Acting as miRNAs’ Sponges and Their Roles in Stem Cells

Circular RNAs (circRNAs), a novel type of endogenous RNAs, have become a subject of intensive research. It has been found that circRNAs are important players in cell differentiation and tissue homeostasis, as well as disease development. Moreover, the expression of circRNAs is usually not correlated with their parental gene expression, indicating that they are not only a steady-state by-product of mRNA splicing but a product of variable splicing under novel regulation. Sequence conservation analysis has also demonstrated that circRNAs have important non-coding functions. CircRNAs exist as a covalently closed loop form in mammalian cells, where they regulate cellular transcription and translation processes. CircRNAs are built from pre-messenger RNAs, and their biogenesis involves back-splicing, which is catalyzed by spliceosomes. The splicing reaction gives rise to three different types of intronic, exotic and exon–intron circular RNAs. Due to higher nuclease stability and longer half lives in cells, circRNAs are more stable than linear RNAs and have enormous clinical advantage for use as diagnostic and therapeutic biomarkers for disease. In recent years, it has been reported that circRNAs in stem cells play a crucial role in stem cell function. In this article, we reviewed the general feature of circRNAs and the distinct roles of circRNAs in stem cell biology, including regulation of stem cell self-renewal and differentiation. CircRNAs have shown unique expression profiles during differentiation of stem cells and could serve as promising biomarkers of these cells. As circRNAs play pivotal roles in stem cell regulation as well as the development and progression of various diseases, we also discuss opportunities and challenges of circRNA-based treatment strategies in future effective therapies for promising clinical applications.

The emerging roles of circRNAs in cancer and oncology

Over the past decade, circular RNAs (circRNAs) have emerged as a large class of primarily non-coding RNA molecules, many of which have key roles in cancer development and progression through diverse mechanisms of action. CircRNAs often have tissue-restricted and cancer-specific expression patterns, and accumulating data suggest that these molecules are of potential clinical relevance and utility. In particular, circRNAs have strong potential as diagnostic, prognostic and predictive biomarkers, which is underscored by their detectability in liquid biopsy samples such as in plasma, saliva and urine. However, technical issues in the detection and assessment of circRNAs as well as biological knowledge gaps need to be addressed to move this relatively young field of research forward and bring circRNAs to the forefront of clinical practice. Herein, we review the current knowledge regarding circRNA biogenesis, regulation and functions in cancer as well as their clinical potential as biomarkers, therapeutic agents and drug targets.

CircRNA ZNF609 promotes the growth and metastasis of thyroid cancer in vivo and in vitro by downregulating miR-514a-5p

Thyroid cancer (TC) often manifests in the form of a painless cervical mass or nodule and continues to increase in incidence. Currently, much less is known about its pathogenesis in TC cells. This study sought to figure out what role the circular RNA (circRNA) ZNF609/miR-514a-5p might play in TC development and metastasis. In this study, the detection of circ-ZNF609 and miR-514a-5p expressions was carried out by qRT-PCR in TC cell lines. Cell proliferation assessment is employed by cell counting kit-8 (CCK-8) assay, colony formation, Western blot and immunofluorescence. Cell invasion and migration measurement were conducted applying wound healing and transwell. The relationship between circ-ZNF609 and miR-514a-5p was subjected to prediction with bioinformatics analysis and validated with the aid of luciferase reporter assay. Furthermore, xenograft animal experiment was adopted to confirm the role of circ-ZNF609/miR-514a-5p in TC in vivo. The data indicated that circ-ZNF609 was highly expressed, while miR-514a-5p was downregulated in TC cells. Circ-ZNF609 knockdown prevented the malignant biological behaviors of TPC-1 and IHH-4 cells. Besides, circ-ZNF609 sponged miR-514a-5p and miR-514a-5p knockdown reversed the suppressed impacts of circ-ZNF609 knockdown on TC cell malignant biological behaviors. In addition, the silence of circ-ZNF6091 significantly repressed, whereas miR-514a-5p silencing promoted TC tumorigenesis in vivo. The findings highlighted the importance of circ-ZNF609 function in facilitating TC cell development and metastasis in vitro and in vivo via binding to miR-514a-5p.

Circular RNA ZNF609 functions as a competing endogenous RNA in regulating E2F transcription factor 6 through competitively binding to microRNA-197-3p to promote the progression of cervical cancer progression

Countless studies have demonstrated that Circular RNAs (circRNAs) exert vital effects in regulating tumorigenesis of various cancers. CircRNA ZNF609 (circ-ZNF609) has been reported as an oncogene in various human cancers. Nevertheless, its regulating effect in cervical cancer (CC) remains to be further explored. RT-qPCR was adopted to measure circ-ZNF609, miR-197-3p and E2F6 levels. CC cell proliferation, migration and invasion were analyzed via CCK-8 and transwell assays. Dual-luciferase reporter assay was adopted to confirm the interaction between miR-197-3p and circ-ZNF609 or E2F6. In the present study, it was found that circ-ZNF609 was elevated in CC tissues and cell lines, and circ-ZNF609 deletion repressed cell viability, migration and invasion in CC. Moreover, circ-ZNF609 was identified to negatively regulate miR-197-3p expression in CC cells. The inhibition of miR-197-3p abrogated the inhibitory effect on CC cell proliferation, migration and invasion induced by circ-ZNF609 knockdown. Additionally, we further demonstrated that circ-ZNF609 upregulated E2F6 by interacting with miR-197-3p. Finally, rescue assays indicated that E2F6 overexpression upended the suppression of CC progression induced by circ-ZNF609 deletion. In conclusion, circ-ZNF609 promoted CC progression through modulating the miR-197-3p/E2F6 axis as an oncogene. This finding offers a unique insight into CC molecular mechanism and suggests a potential target for CC therapy.

The Crosstalk Between Regulatory Non-Coding RNAs and Nuclear Factor Kappa B in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a highly lethal type of malignancies that possesses great loss of life safety to human beings worldwide. However, few effective means of curing HCC exist and its specific molecular basis is still far from being fully elucidated. Activation of nuclear factor kappa B (NF-κB), which is often observed in HCC, is considered to play a significant part in hepatocarcinogenesis and development. The emergence of regulatory non-coding RNAs (ncRNAs), particularly microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), is a defining advance in cancer biology, and related research in this branch has yielded many diagnostic and therapeutic opportunities. Recent studies have suggested that regulatory ncRNAs act as inhibitors or activators in the initiation and progression of HCC by targeting components of NF-κB signaling or regulating NF-κB activity. In this review, we attach importance to the role and function of regulatory ncRNAs in NF-κB signaling of HCC and NF-κB-associated chemoresistance in HCC, then propose future research directions and challenges of regulatory ncRNAs mediated-regulation of NF-κB pathway in HCC.

circ-ZNF609: A potent circRNA in human cancers

Circular RNAs (circRNAs) are a novel group of endogenous RNAs with a circular structure. Growing evidence indicates that circRNAs are involved in a variety of human diseases including malignancies. CircRNA ZNF609 (circ‐ZNF609), derived from the ZNF609 gene sequence, has been demonstrated to be involved in the development and progression of many diseases. circ‐ZNF609 is thought to be a viable diagnostic and prognostic biomarker for several diseases and might be a new therapeutic target, but further research is needed to accelerate clinical application. Here, we review the biogenesis and function of circRNAs and the functional roles and molecular mechanism related to circ‐ZNF609 in neoplasms and other diseases.

MicroRNA‑200c‑3p suppresses intervertebral disc degeneration by targeting RAP2C/ERK signaling

Intervertebral disc degeneration (IDD) is a major cause of lower back pain. The high morbidity associated with this disease diminishes the quality of life of those who are affected. MicroRNAs (miRs) play crucial roles in various diseases, including IDD. However, the mechanism via which miR‑200c‑3p plays a role in the development of IDD remains unknown. The present study aimed to investigate the effect of miR‑200c‑3p on the progression of IDD and the underlying mechanism. The expression level of miR‑200c‑3p was evaluated in intervertebral disc tissues from patients with IDD. To construct the IDD cell model, the nucleus pulposus (NP) cells were treated with lipopolysaccharide (LPS) 24 h following transfection with miR‑200c‑3p mimic or inhibitor. A luciferase activity assay was performed, while reverse transcription‑quantitative PCR and western blotting were conducted to determine the RNA and protein expression levels, respectively. The expression level of miR‑200c‑3p in the intervertebral disc tissues of patients with IDD was lower than that of normal subjects. LPS treatment reduced the expression level of miR‑200c‑3p in NP cells. Moreover, miR‑200c‑3p mimic inhibited LPS‑induced NP cell apoptosis. It was found that miR‑200c‑3p attenuated inflammatory cytokine levels and extracellular matrix (ECM) degradation in NP cells. Furthermore, miR‑200c‑3p targeted Ras‑related protein 2C (RAP2C) in NP cells. RAP2C promoted apoptosis, inflammatory cytokine levels and ECM degradation by activating ERK signaling. Knockdown of RAP2C and inhibition of ERK signaling by SCH772984 partially reversed the proinflammatory effect of the miR‑200c‑3p inhibitor on LPS‑treated NP cells. Thus, miR‑200c‑3p inhibits NP cell apoptosis, inflammatory cytokine levels and ECM degradation in IDD by targeting RAP2C/ERK signaling.

Circular RNA ZNF609 drives tumor progression by regulating the miR-138-5p/SIRT7 axis in melanoma

Melanoma serves as a prevailing and lethal skin malignancy with high mortality and a growing number of patients globally. Circular RNAs (circRNAs), as a type of emerging cellular regulator, are involved in the modulation of melanoma. Nevertheless, the function of circZNF609 in melanoma development remains obscure. In this study, we were interested in the effect and the underlying mechanism of circZNF609 on DNA damage during melanoma progression. The circZNF609 depletion significantly suppressed melanoma cell invasion, migration, and proliferation, and stimulated apoptosis. Meanwhile, comet assays showed that the tail length and γH2AX levels were elevated by circZNF609 depletion. Mechanically, circZNF609 sponged miR-138-5p and miR-138-5p targeted SIRT7 in the melanoma cells. The SIRT7 overexpression and miR-138-5p inhibitor could reverse circZNF609 depletion-mediated DNA damage and malignant progression in melanoma cells. Functionally, CircZNF609 promoted cell growth of melanoma in the nude mice. Consequently, we conclude that circZNF609 suppresses DNA damage and potentially enhances melanoma progression at the experimental condition by modulating the miR-138-5p/SIRT7 axis. Our finding provides new insights into the mechanism by which circZNF609 modulates the development of melanoma. CircZNF609 and miR-138-5p may be utilized as therapeutic targets for melanoma.

Expression patterns and prognostic potential of circular RNAs in mantle cell lymphoma: a study of younger patients from the MCL2 and MCL3 clinical trials

Mantle cell lymphoma (MCL) is characterized by marked differences in outcome, emphasizing the need for strong prognostic biomarkers. Here, we explore expression patterns and prognostic relevance of circular RNAs (circRNAs), a group of endogenous non-coding RNA molecules, in MCL. We profiled the circRNA expression landscape using RNA-sequencing and explored the prognostic potential of 40 abundant circRNAs in samples from the Nordic MCL2 and MCL3 clinical trials, using NanoString nCounter Technology. We report a circRNA-based signature (circSCORE) developed in the training cohort MCL2 that is highly predictive of time to progression (TTP) and lymphoma-specific survival (LSS). The dismal outcome observed in the large proportion of patients assigned to the circSCORE high-risk group was confirmed in the independent validation cohort MCL3, both in terms of TTP (HR 3.0; P = 0.0004) and LSS (HR 3.6; P = 0.001). In Cox multiple regression analysis incorporating MIPI, Ki67 index, blastoid morphology and presence of TP53 mutations, circSCORE retained prognostic significance for TTP (HR 3.2; P = 0.01) and LSS (HR 4.6; P = 0.01). In conclusion, circRNAs are promising prognostic biomarkers in MCL and circSCORE improves identification of high-risk disease among younger patients treated with cytarabine-containing chemoimmunotherapy and autologous stem cell transplant.

Circular RNA ZNF609 promotes the malignant progression of glioma by regulating miR-1224-3p/PLK1 signaling

Objective: Previous studies have demonstrated that circular RNAs (circRNAs) play vital roles in pathological process of various diseases, including tumors. This study aimed at exploring the role and mechanism of circRNA RNA ZNF609 (circ-ZNF609) in the occurrence and development of glioma. Materials and methods: Real-time quantitative PCR (qRT-PCR) was applied to measure the expression of circ-ZNF609, miRNA-1224-3p (miR-1224-3p) and Polo-like kinase 1 (PLK1) in glioma tissues and cell lines. Furthermore, the association between circ-ZNF609 and clinical features of glioma was analyzed. CCK8 assay, EdU assay and Transwell assay were conducted to detect the effect of circ-ZNF609, miR-1224-3p and PLK1 on proliferation, migration and invasion in glioma cells. Then, we investigated the underlying mechanism of circ-ZNF609 by bioinformatics analysis, luciferase reporter assay, RNA immunoprecipitation (RIP), qRT-PCR and western blotting assay. Results: Circ-ZNF609 was confirmed prominently upregulated in glioma. Inhibition of circ-ZNF609 could obviously suppress glioma cell proliferation, migration and invasion, while overexpression of circ-ZNF609 promoted glioma growth and metastasis. In vivo, xenotransplanted tumor model also showed that overexpression of circ-ZNF609 could promote in vivo glioma growth. Mechanistically, circ-ZNF609 could promote PLK1 expression via binding to miR-1224-3p, circ-ZNF609/miR-1224-3p/PLK1 was shown responsible for circ-ZNF609 promoting glioma growth and metastasis. Conclusion: Together, our results revealed that circ-ZNF609 elevates glioma growth and metastasis via enforcing PLK1 expression by competitively binding miR-1224-3p, suggesting that circ-ZNF609 might be an underlying therapeutic target for glioma.

Recent Update on the Role of Circular RNAs in Hepatocellular Carcinoma

After being overlooked for decades, circular RNAs (circRNAs) have recently generated considerable interest. circRNAs play a role in a variety of normal and pathological biological processes, including hepatocarcinogenesis. Many circRNAs contribute to hepatocarcinogenesis through sponging of microRNAs (miRs) and disruption of cellular signaling pathways that play a part in control of cell proliferation, metastasis and apoptosis. In most cases, overexpressed circRNAs sequester miRs to cause de-repressed translation of mRNAs that encode oncogenic proteins. Conversely, low expression of circRNAs has also been described in hepatocellular carcinoma (HCC) and is associated with inhibited production of tumor suppressor proteins. Other functions of circRNAs that contribute to hepatocarcinogenesis include translation of truncated proteins and acting as adapters to regulate influence of transcription factors on target gene expression. circRNAs also affect hepatocyte transformation indirectly. For example, the molecules regulate immune surveillance of cancerous cells and influence the liver fibrosis that commonly precedes HCC. Marked over- or under-expression of circRNA expression in HCC, with correlating plasma concentrations, has diagnostic utility and assays of these RNAs are being developed as biomarkers of HCC. Although knowledge in the field has recently surged, the myriad of described effects suggests that not all may be vital to hepatocarcinogenesis. Nevertheless, investigation of the role of circRNAs is providing valuable insights that are likely to contribute to improved management of a serious and highly aggressive cancer.