A Novel Circular RNA hsa_circRPPH1_015 Exerts an Oncogenic Role in Breast Cancer by Impairing miRNA-326-Mediated ELK1 Inhibition

Circ_RPPH1 facilitates progression of breast cancer via miR-1296-5p/TRIM14 axis

Circular RNA Ribonuclease P RNA Component H1 (circ_RPPH1) and microRNA (miRNA) miR-1296-5p play a crucial role in breast cancer (BC), but the molecular mechanism is vague. Evidence showed that miR-1296-5p can activate tripartite motif-containing 14 (TRIM14). Clinical indications of eighty BC patients were collected and the circ_RPPH1 expression was detected using real-time quantitative PCR. MCF-7 and MDA-MB-231 cells were transfected with overexpression or knockdown of circ_RPPH1, miR-1296-5p, or TRIM14. Cell counting kit-8, cell cloning formation, wound healing, Transwell, and flow cytometry assays were performed to investigate the malignant phenotype of BC. The dual-luciferase reporter gene analyses were applied to reveal the interaction between these target genes. Subcutaneous tumorigenic model mice were established with circ_RPPH1 overexpression MDA-MB-231 cells in vivo; the tumor weight and volume, levels of miR-1296-5 and TRIM14 mRNA were measured. Western blot and immunohistochemistry were used to detect TRIM14 in cells and mice. Circ_RPPH1 levels were notably higher in BC patients and have been found to promote cell proliferation, invasion, and migration of BC cells. Circ_RPPH1 altered cell cycle and hindered apoptosis. Circ_RPPH1 knockdown or miR-1296-5p overexpression inhibited the malignant phenotype of BC. Furthermore, miR-1296-5p knockdown reversed circ_RPPH1's promotion effects on BC. Interestingly, TRIM14 overexpression counteracts the inhibitory effects of miR-1296-5p overexpression and circ_RPPH1 silencing on BC. Moreover, in BC tumor-bearing mice, circ_RPPH1 overexpression led to increased TRIM14 expression and facilitated tumor growth. Circ_RPPH1 enhanced BC progression through miR-1296-5p/TRIM14 axis, indicating its potential as a biomarker and therapeutic target in BC.

RUSC1-AS1 promotes the malignant progression of breast cancer depending on the regulation of the miR-326/XRCC5 pathway

BACKGROUND

Many long noncoding RNAs (lncRNAs) are the key regulators for cancer progression, including breast cancer (BC). RUSC1 antisense 1 (RUSC1-AS1) has been found to be highly expressed in BC, but its role and potential molecular mechanism in BC remain to be further elucidated.

METHODS

Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was utilized to measure RUSC1-AS1, microRNA (miR)-326 and X-ray repair cross-complementing group 5 (XRCC5) expression. Cell proliferation, metastasis, cell cycle, apoptosis and angiogenesis were determined by cell counting kit-8, colony formation, transwell, flow cytometry and tube formation assays. Protein expression was detected by western blot analysis. The targeted relationship between miR-326 and RUSC1-AS1 or XRCC5 was validated using dual-luciferase reporter assay and RIP assay. Xenograft models were constructed to uncover the effect of RUSC1-AS1 on BC tumorigenesis.

RESULTS

RUSC1-AS1 was upregulated in BC, and its downregulation suppressed BC proliferation, metastasis, cell cycle, angiogenesis, and tumor growth. MiR-326 was confirmed to be sponged by RUSC1-AS1, and its inhibitor reversed the regulation of RUSC1-AS1 silencing on BC progression. XRCC5 could be targeted by miR-326. Overexpression of XRCC5 reversed the inhibitory impacts of miR-326 on BC progression.

CONCLUSION

RUSC1-AS1 could serve as a sponge of miR-326 to promote BC progression by targeting XRCC5, suggesting that RUSC1-AS1 might be a target for BC treatment.

CircRPPH1 promotes the stemness of gastric cancer cells by targeting miR-375/SLC7A11 axis

This study mainly focuses on revealing the role of circRPPH1 in gastric cancer cell stemness. In vitro and in vivo experiments were performed to evaluate the effects of circRPPH1 on gastric cancer cell stemness. Luciferase reporter and RIP assays were implemented to reveal the underlying mechanisms. MiR-375 directly bound to circRPPH1 in gastric cancer cells. And circRPPH1 acted as an miR-375 sponge to positively regulate SLC7A11 expression, which has been confirmed to be the direct target of miR-375 in gastric cancer, and thus regulated ferroptosis. Moreover, circRPPH1 promoted the stemness of gastric cancer cells dependent on the miR-375/SLC7A11. This study provides a potential target for gastric cancer progression based on the circRPPH1/miR-375/SLC7A11 regulatory axis.

Exosomal circular RNAs: New player in breast cancer progression and therapeutic targets

Breast cancer is the most prevalent type of malignancy among women. Exosomes are extracellular vesicles of cell membrane origin that are released via exocytosis. Their cargo contains lipids, proteins, DNA, and different forms of RNA, including circular RNAs. Circular RNAs are new class of non-coding RNAs with a closed-loop shape involved in several types of cancer, including breast cancer. Exosomes contained a lot of circRNAs which are called exosomal circRNAs. By interfering with several biological pathways, exosomal circRNAs can have either a proliferative or suppressive role in cancer. The involvement of exosomal circRNAs in breast cancer has been studied with consideration to tumor development and progression as well as its effects on therapeutic resistance. However, its exact mechanism is still unclear, and there have not been available clinical implications of exo-circRNAs in breast cancer. Here, we highlight the role of exosomal circRNAs in breast cancer progression and to highlight the most recent development and potential of circRNAas therapeutic targets and diagnostics for breast cancer.

C-Fos-activated circRPPH1 contributes to glioma stemness

OBJECTIVE

Cancer stem cells or cancer stemness has been confirmed to a major obstacle for glioma progression and it has also been reported that circRNAs play an important part in cancer progression. This study mainly focuses on revealing the role of circRPPH1 and the underlying mechanisms in glioma cell stemness.

METHODS

In vitro experiment including RT-qPCR, Western blot, sphere-formation analysis, and ALDH1 activity, and in vivo tumorigenesis experiments were performed to evaluate the effects of circRPPH1 on glioma cell stemness. Luciferase reporter, ChIP, and DNA pull-down analysis were used to reveal the underlying mechanisms.

RESULTS

It was found that circRPPH1 level was upregulated in glioma cell spheres and facilitated the stemness of glioma cells; C-FOS transcriptionally activated circRPPH1 expression via directly binding to circRPPH1 promoter in glioma cells. Moreover, circRPPH1 promoted the stemness of glioma cells dependent on c-FOS-mediated transcriptional activation.

CONCLUSIONS

This study indicates that c-Fos-activated circRPPH1 contributes to glioma stemness and provides a potential target for glioma progression based on the c-FOS/circRPPH1 regulatory axis.

Silencing circ_0074371 inhibits the progression of sepsis-induced acute kidney injury by regulating miR-330-5p/ELK1 axis

BACKGROUND

Sepsis-induced acute kidney injury (AKI) is a common in clinic. Circular RNAs (circRNAs) play significant roles in ameliorating AKI. The purpose of this study was aimed to identify the role of circ_0074371 and the potential action mechanism in sepsis-induced AKI.

METHODS

AKI patients and healthy individual serum samples were collected and the relative expression of circ_0074371 was measured by real-time polymerase chain reaction (RT-PCR). HK2 cells were treated with different dose (0, 2.5, 5 and 10 μg/ml) lipopolysaccharide (LPS) to establish the AKI cell model. The cell viability and apoptosis of HK2 cells were detected using cell counting kit-8 (CCK-8) and flow cytometry, respectively. The contents of malondialdehyde (MDA), and superoxide dismutase (SOD) were evaluated using the relative commercial kits. The IL-1β and TNF-α levels in cell culture supernatants were measured by ELISA. The interaction relationship between miR-330-5p and circ_0074371 or ELK1 was predicted by Targetscan database and further confirmed by the dual-luciferase reporter assay system.

RESULTS

The circ_0074371 expression was up-regulated in sepsis patients and LPS-induced HK2 cells. Silencing circ_0074371 promoted HK2 cells viability and inhibited the HK2 cells apoptosis. miR-330-5p inhibitor weakened circ_0074371 inhibitor-induced cell viability, apoptosis and oxidative stress. Further mechanism analysis showed that circ_0074371 acted as a sponge for miR-330-5p to increase ELK1 expression level. Importantly, miR-330-5p downregulation or ELK1 upregulation reversed the action of circ_0074371 knockdown on LPS-induced HK2 cells.

CONCLUSION

Knockdown of circ_0074371 ameliorated LPS-induced HK2 cells apoptosis, inflammation and oxidative stress via regulating miR-330-5p/ELK1, opening a new window into the pathogenesis AKI.

UPF1/circRPPH1/ATF3 feedback loop promotes the malignant phenotype and stemness of GSCs

Glioblastoma multiforme (GBM) is the most lethal type of craniocerebral gliomas. Glioma stem cells (GSCs) are fundamental reasons for the malignancy and recurrence of GBM. Revealing the critical mechanism within GSCs' self-renewal ability is essential. Our study found a novel circular RNA (circRPPH1) that was up-regulated in GSCs and correlated with poor survival. The effect of circRPPH1 on the malignant phenotype and self-renewal of GSCs was detected in vitro and in vivo. Mechanistically, UPF1 can bind to circRPPH1 and maintain its stability. Therefore, more existing circRPPH1 can interact with transcription factor ATF3 to further transcribe UPF1 and Nestin expression. It formed a feedback loop to keep a stable stream for stemness biomarker Nestin to strengthen tumorigenesis of GSCs continually. Besides, ATF3 can activate the TGF-β signaling to drive GSCs for tumorigenesis. Knocking down the expression of circRPPH1 significantly inhibited the proliferation and clonogenicity of GSCs both in vitro and in vivo. The overexpression of circRPPH1 enhanced the self-renewal of GSCs. Our findings suggest that UPF1/circRPPH1/ATF3 maintains the potential self-renewal of GSCs through interacting with RNA-binding protein and activating the TGF-β signal pathway. Breaking the feedback loop against self-renewing GSCs may represent a novel therapeutic target in GBM treatment.

Circular RNAs as Potential Biomarkers in Breast Cancer

Due to the high heterogeneity and initially asymptomatic nature of breast cancer (BC), the management of this disease depends on imaging together with immunohistochemical and molecular evaluations. These tests allow early detection of BC and patient stratification as they guide clinicians in prognostication and treatment decision-making. Circular RNAs (circRNAs) represent a class of newly identified long non-coding RNAs. These molecules have been described as key regulators of breast carcinogenesis and progression. Moreover, circRNAs play a role in drug resistance and are associated with clinicopathological features in BC. Accumulating evidence reveals a clinical interest in deregulated circRNAs as diagnostic, prognostic and predictive biomarkers. Furthermore, due to their covalently closed structure, circRNAs are highly stable and easily detectable in body fluids, making them ideal candidates for use as non-invasive biomarkers. Herein, we provide an overview of the biogenesis and pleiotropic functions of circRNAs, and report on their clinical relevance in BC.

Circular RNA circCCDC85A inhibits breast cancer progression via acting as a miR-550a-5p sponge to enhance MOB1A expression

BACKGROUND

A growing body of evidence indicates that abnormal expression of circular RNAs (circRNAs) plays a crucial role by acting as molecular sponges of microRNAs (miRNAs) in various diseases, including cancer. In this study, we explored whether circCCDC85A could function as a miR-550a-5p sponge and influence breast cancer progression.

METHODS

We detected the expression of circCCDC85A in breast cancer tissues and cells using fluorescence in situ hybridization (FISH) and quantitative reverse transcription polymerase chain reaction (qRT-PCR). CCK-8 and colony formation assay were used to detect the proliferative ability of breast cancer cells. Wound healing assay and transwell migration and invasion assays were used to detect the migrative and invasive abilities of breast cancer cells. We also examined the interactions between circCCDC85A and miR-550a-5p using FISH, RNA-binding protein immunoprecipitation (RIP), and luciferase reporter assay. Moreover, we performed luciferase reporter assay, qRT-PCR, and Western blot to confirm the direct targeting of miR-550a-5p to MOB1A.

RESULTS

The expression of circCCDC85A in breast cancer tissues was obviously lower than that in normal breast tissues. Over-expression of circCCDC85A substantially inhibited the proliferative, migrative, and invasive ability of breast cancer cells, while knocking down of circCCDC85A enhanced the aforementioned properties of breast cancer cells. Moreover, enforced expression of circCCDC85A inhibits the oncogenic activity of miR-550a-5p and increases the expression of MOB1A targeted by miR-550a-5p. Further molecular mechanism research showed that circCCDC85A may act as a molecular sponge for miR-550a-5p, thus restoring miR-550a-5p-mediated targeting repression of tumor suppressor MOB1A in breast cancer cells.

CONCLUSION

Our findings provide novel evidence that circCCDC85A inhibits the progression of breast cancer by functioning as a molecular sponge of miR-550a-5p to enhance MOB1A expression.

CircRPPH1 promotes cell proliferation, migration and invasion of non-small cell lung cancer (NSCLC) via the PI3K/AKT and JAK2/STAT3 signaling axes

Non-small cell lung cancer (NSCLC) has markedly increased morbidity and mortality rate worldwide. Circular RNAs (circRNAs) were shown to regulate NSCLC progression. But, the underlying pathways of the circRPPH1-mediated regulation of NSCLC still need further exploration. We evaluated circRPPH1 levels in NSCLC tissues and cell lines via qRT-RCR. Moreover, using ectopic plasmid incorporation and siRNA assays, we analyzed the circRPPH1-mediated regulation of cell proliferation (CP), migration (CM), and invasion (CI) in NSCLC cell lines (H1975 and A549 cells), using CCK-8, colony forming, scratch wound, and transwell assays, respectively. CircRPPH1 levels were remarkably high in the NSCLC tissues and cell lines. The transfection experiments showed that circRPPH1 overexpression was able to promote CP, CM and CI of NSCLC cells, while CP, CM and CI were significantly restrained by the knockdown of circRPPH1. We also displayed that circRPPH1 knockdown suppressed the cell progression via inactivating the PI3K/AKT and JAK2/STAT3 signaling axes. Subsequently, in vivo experiment in nude mice was demonstrated that the inhibition of circRPPH1 could reduce the tumor growth of NSCLC. circRPPH1 may accelerate the growth and metastasis of NSCLC, in culture conditions and in animal models, by stimulating the PI3K/AKT and JAK2/STAT3 signaling axes, thus promoting the development of NSCLC.

A novel circular RNA circPPFIA1 promotes laryngeal squamous cell carcinoma progression through sponging miR-340-3p and regulating ELK1 expression

Abnormal expression of circular RNA (circRNA) is closely related to the occurrence and development of many cancers. By screening the expression of circRNA, we identified a novel circRNA termed as has_circ_0023326 in laryngeal squamous cell carcinoma (LSCC). We verified the expression of circPPFIA1 and found that it was upregulated in LSCC tissues compared to the adjacent normal tissues. Functional studies were carried out to detect the effect of circPPFIA1 expression on the phenotype of LSCC cells. These results suggest that circPPFIA1 knockdown can suppress the proliferation, migration, and invasion of LSCC cells, while circPPFIA1 overexpression can promote these processes. Mechanistically, miR-340-3p was predicted to be the target miRNA sponged by circPPFIA1 as confirmed through the luciferase assay and rescue experiments. In addition, miR-340-3p was found to target ELK1 and inhibit its expression. Taken together, circPPFIA1 promotes the progression of LSCC via the miR-340-3p/ELK1 signaling axis, which may serve as a novel prognostic or therapeutic target for LSCC.

Circular RNAs Interaction with MiRNAs: Emerging Roles in Breast Cancer

Despite significant advances in cancer therapy strategies, breast cancer is one of the most common and lethal malignancies worldwide. Characterization of a new class of RNAs using next-generation sequencing opened new doors toward uncovering etiopathogenesis mechanisms of breast cancer as well as prognostic and diagnostic biomarkers. Circular RNAs (circRNAs) are a novel class of RNA with covalently closed and highly stable structures generated primarily from the back-splicing of precursor mRNAs. Although circRNAs exert their function through various mechanisms, acting as a sponge for miRNAs is their primary mechanism of function. Furthermore, growing evidence has shown that aberrant expression of circRNAs is involved in the various hallmarks of cancers. This paper reviews the biogenesis, characteristics, and mechanism of functions of circRNAs and their deregulation in various cancers. Finally, we focused on the circRNAs roles as a sponge for miRNAs in the development, metastasis, angiogenesis, drug resistance, apoptosis, and immune responses of breast cancer.

The Regulation Network and Clinical Significance of Circular RNAs in Breast Cancer

Breast cancer is one of the most common malignant tumors in women worldwide. Circular RNA (circRNA) is a class of structurally stable non-coding RNA with a covalently closed circular structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been discovered and have proven to be clinically significant in the development and progression of breast cancer. Importantly, several regulators of circRNA biogenesis have been discovered. Here, we systematically summarize recent progress regarding the network of regulation governing the biogenesis, degradation, and distribution of circRNAs, and we comprehensively analyze the functions, mechanisms, and clinical significance of circRNA in breast cancer.

The biogenesis, function and clinical significance of circular RNAs in breast cancer

Circular RNAs (circRNAs) are noncoding RNAs that form covalently closed loop structures. CircRNAs are dysregulated in cancer and play key roles in tumorigenesis, diagnosis, and tumor therapy. CircRNAs function as competing endogenous RNAs or microRNA sponges that regulate transcription and splicing, binding to proteins, and translation. CircRNAs may serve as novel biomarkers for cancer diagnosis, and they show potential as therapeutic targets in cancers including breast cancer (BC). In women, BC is the most common malignant tumor worldwide and the second leading cause of cancer death. Although evidence indicates that circRNAs play a critical role in BC, the mechanisms regulating the function of circRNAs in BC remain poorly understood. Here, we provide literature review aiming to clarify the role of circRNAs in BC and summarize the latest research. We provide a systematic overview of the biogenesis and biological functions of circRNAs, elaborate on the functional roles of circRNAs in BC, and highlight the value of circRNAs as diagnostic and therapeutic targets in BC.

CircRNA circYY1 (hsa_circ_0101187) Modulates Cell Glycolysis and Malignancy Through Regulating YY1 Expression by Sponging miR-769-3p in Breast Cancer

Background

Breast cancer (BC) is a highly heterogeneous malignant tumor that affects women’s health. Circular RNAs (circRNAs) are involved in tumor growth in many cancers. However, the role of hsa_circ_0101187 (circYY1) in BC is still unclear.

Methods

Expression of circYY1, microRNA (miR)-769-3p, and YY1 (Yin Yang 1) mRNA was tested by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability, colony formation, migration, and invasion were analyzed with MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide), colony formation, and transwell assays. Glucose uptake, lactate product, and ATP (adenosine triphosphate) content were detected with corresponding kits. Several protein levels were measured with Western blotting. The regulatory mechanisms of the circYY1, miR-769-3p, and YY1 were validated by RNA immunoprecipitation (RIP) assay, dual-luciferase reporter assay, and/or RNA pull-down assay. The role of circYY1 in BC was confirmed by xenograft assay.

Results

CircYY1 and YY1 were upregulated in BC, while miR-769-3p had an opposing result. Also, BC patients with high circYY1 expression had a poor prognosis. Downregulation of circYY1 decreased xenograft tumor growth in vivo. Both circYY1 inhibition and miR-769-3p elevation constrained BC cell viability, colony formation, migration, invasion, and glycolysis in vitro. CircYY1 acted as a sponge for miR-769-3p, which targeted YY1. CircYY1 sponged miR-769-3p to modulate YY1 expression. Both miR-769-3p inhibition and YY1 upregulation antagonized circYY1 silencing-mediated influence on malignancy and glycolysis of BC cells.

Conclusion

CircYY1 promoted glycolysis and tumor growth via increasing YY1 expression through sponging miR-769-3p in BC, offering a promising therapeutic target and prognostic biomarker for BC.

The roles of circRNAs in cancers: Perspectives from molecular functions

Circular RNAs (circRNAs), characteristic of covalently closed loops generated by back-splicing, are a subclass of single-stranded RNA molecules. Owing to the circular structures, circRNAs are protected from exonuclease-induced degradation, which makes them more stable compared with linear RNAs. With the development of high-throughput sequencing technology and bioinformatics, the roles of circRNAs in a variety of physiological and pathophysiological processes have been increasingly revealed. Although the functions of most circRNAs remain largely elusive, accumulating studies have identified them as microRNA(miRNA) sponges, protein regulators, transcriptional regulators, protein templates, and so forth. In this review, we briefly describe the biogenesis of circRNAs and provide an overview on their functions in cancers, including miRNA sponges, protein regulators, transcriptional regulators, protein templates. Furthermore, we discuss the potential application of circRNAs as biomarkers and give insight into future perspectives.