Identification of Key circRNAs in Non-Small Cell Lung Cancer

CircSEC24A induces KLF8 expression to promote the malignant progression of non-small cell lung cancer by regulating miR-1253

OBJECTIVES

This study aimed to analyze the role of circSEC24A in non-small cell lung cancer (NSCLC) and its underlying mechanism.

METHODS

RNA levels of circSEC24A, microRNA-1253 (miR-1253), and KLF transcription factor 8 (KLF8) were detected by quantitative real-time polymerase chain reaction. Protein expression was analyzed by western blot or immunohistochemistry assay. Cell proliferation and apoptosis were investigated by colony formation assay, 5-ethynyl-2'-deoxyuridine assay, and flow cytometry analysis. Glycolysis was evaluated by commercial kits. Dual-luciferase reporter assay and RNA immunoprecipitation assay were conducted to identify the associations among circSEC24A, miR-1253, and KLF8. Xenograft mouse model assay was used to evaluate the effect of circSEC24A on tumor tumorigenesis.

RESULTS

CircSEC24A and KLF8 were upregulated, while miR-1253 was downregulated in NSCLC. CircSEC24A knockdown inhibited proliferation and glycolysis but induced the apoptosis of NSCLC cells. CircSEC24A acted as a miR-1253 sponge and regulated NSCLC cell malignancy by targeting miR-1253. KLF8 was identified as a target of miR-1253, and its overexpression attenuated miR-1253-induced effects in NSCLC cells. Besides, circSEC24A upregulated KLF8 by sponging miR-1253. Further, circSEC24A knockdown suppressed NSCLC cell tumorigenesis in vivo.

CONCLUSIONS

CircSEC24A silencing inhibited NSCLC cell malignancy through the miR-1253/KLF8 pathway, providing a potential therapeutic target for NSCLC.

The role of m6A modified circ0049271 induced by MNNG in precancerous lesions of gastric cancer

Gastric cancer (GC) is a malignant cancer with the highest global rates of morbidity and death. Dietary factors have a close relationship with the occurrence of GC. Circular RNAs (circRNAs) and N6-methyladenine (m6A) are important factors in the onset and progression of GC and other malignancies. However, little is known about the role of circRNA m6A modifications in the occurrence and development of GC. Initially, a transformed malignant cell model generated by the chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was established in this investigation. Furthermore, following exposure to MNNG, circ0049271 is substantially expressed in gastric epithelial cells (GES-1). Subsequent research revealed that the knockdown of circ0049271 prevented the epithelial-mesenchymal transition (EMT) as well as the migration, invasion, and proliferation of gastric epithelial cells induced by long-term exposure to MNNG. The opposite effects were observed when circ0049271 was overexpressed. Mechanistically, circ0049271 activates the TGFβ/SMAD signaling pathway and has m6A modifications mediated by WTAP. Our findings indicate that circ0049271 promotes the occurrence of GC by regulating the TGFβ/SMAD pathway, and WTAP may mediate the methylation of circ0049271 m6A. This study provides new insights into the regulation of circRNA-mediated m6A modifications and the discovery of early GC induced by dietary factors such as nitrite.

Downregulation of hsa_circTLK1 represses non-small cell lung cancer progression by regulating miR-876-3p/SRSF7 axis

Background

This study clarified the expression of cicrTLK1 in non-small cell lung cancer (NSCLC) and explored its role in cancer growth, metastasis and immune escape, providing a potential molecular target and theoretical basis for NSCLC treatment.

Methods

The expression levels of circTLK1, miR-876-3p and SRSF7 were determined by RT-qPCR assay. The localization of circTLK1 in NSCLC cells was determined by FISH assay. EdU and cell plate clone formation assay were applied to explore cell proliferation. Wound healing test and Transwell assay were applied to measure the migration and invasion ability. Cell apoptosis rate was detected by FCM assay. Western blotting assay was adopted to measure the protein expression of SRSF7. Dual-luciferase reporter gene assay was applied to assess the interaction between miR-876-3p and circTLK1, and between miR-876-3p and SRSF7. The ability of cirTLK1 to regulate tumor formation in vivo was examined by tumor transplantation experiments in nude mice.

Results

The relative expression of circTLK1 was increased in NSCLC cell lines. Knockdown of circTLK1 prohibited the proliferation, migration, and invasion, and promoted apoptosis rate, but miR-876-3p inhibitor reversed the effects of circTLK1 knockdown. In addition, silencing of circTLK1 overtly restrained the growth of transplanted tumors in vivo, and inhibited immune escape. In addition, circTLK1 interacted with miR-876-3p, and SRSF7 was concluded to be the target gene of miR-876-3p.

Conclusion

In this study, we researched the inhibitory effect of circTLK1knockdown on NSCLC progression and immune escape, and further elucidated the potential regulatory mechanism of circTLK1/miR876-3p/SRSF7 axis.

Circ_0049271 targets the miR-1197/PTRF axis to attenuate the malignancy of osteosarcoma

BACKGROUND

Circular RNAs (circRNAs) perform key regulatory functions in osteosarcoma (OS) tumorigenesis. In this study, we aimed to explore the detailed action mechanisms of circ_0049271 in OS progression.

METHODS

Cell colony formation, cell counting kit-8, and transwell assays were performed to assess the proliferation and invasion of OS cells. Quantitative reverse transcription-polymerase chain reaction and western blotting were used to determine the expression levels of polymerase 1 and transcript release factor (PTRF), microRNA (miR)-1197, and circ_0049271 in OS cells. Furthermore, RNA immunoprecipitation and dual luciferase assays were conducted to explore the targeted relationships among PTRF, miR-1197, and circ_0049271. Finally, a tumor formation assay was conducted to determine the effects of circ_0049271 on in vivo tumor growth in mice.

RESULTS

High expression levels of miR-1197 and low levels of circ_0049271 and PTRF were observed in OS cells. circ _0049271 targeted miR-1197 to mediate PTRF expression. Moreover, the proliferation and invasion of OS cells were repressed by circ_0049271 or PTRF overexpression and increased by miR-1197 upregulation. Enforced circ_0049271 also impeded tumor growth in vivo. Upregulation of miR-1197 reversed the antitumor effects of circ_0049271 on OS progression in vitro; however, PTRF overexpression attenuated the cancer-promoting effects of miR-1197 on OS in vitro.

CONCLUSIONS

Our findings revealed that circ_0049271 targeted the miR-1197/PTRF axis to attenuate the malignancy of OS, suggesting a potential target for its clinical treatment.

CircRNA circ-PDCD11 is highly expressed in lung large-cell carcinoma and predicts poor survival

BACKGROUND

Circ-PDCD11 (hsa_circ_0019853, 461 bp) has been characterized as an oncogenic circRNA in breast cancer, while its function in other cancers is unclear. In this study, we explored the role of circ-PDCD11 in lung cancer.

METHODS

Plasma samples were obtained from patients with lung large-cell carcinoma (LLCC, n = 40), lung squamous cell carcinoma (LSCC, n = 40), lung adenocarcinoma (LA, n = 40) and small-cell lung cancer (SCLC, n = 40) as well as healthy controls (Control, n = 40). Paired tumor and nontumor tissue samples were obtained from all patients. Expression of circ-PDCD11 in these samples was determined by RT-qPCR. The role of plasma circ-PDCD11 in the diagnosis of LLCC was analyzed with ROC curve. A five-year follow-up was performed to analyze the role of plasma circ-PDCD11 in the prognosis of LLCC.

RESULTS

Plasma circ-PDCD11 was specifically upregulated in LLCC but not in other lung cancer types, compared to the controls. Increased circ-PDCD11 expression in tumor tissues compared to nontumor tissues was only observed in LLCC patients but not in other lung cancer types. Increased plasma circ-PDCD11 levels effectively separated LLCC patients from patients with other types of cancers. High plasma circ-PDCD11 levels were closely correlated with poor survival of LLCC patients. Plasma circ-PDCD11 levels were closely correlated with tumor metastasis, but not tumor size of LLCC.

CONCLUSION

CircRNA circ-PDCD11 is highly expressed specifically in LLCC and predicts poor survival.

Expression analysis of hsa_circ_0020397, hsa_circ_0005986, hsa_circ_0003028, and hsa_circ_0006990 in renal cell carcinoma

Renal cell carcinoma (RCC) is a prevalent heterogeneous kidney cancer. So far, different genes have been reported for RCC development. However, its particular molecular mechanism remains unclear. Circular RNAs (circRNAs), a class of non-coding RNAs, are involved in numerous biological processes in different malignancies such as RCC. This study aims to assess the expression and underlying mechanism of four circRNAs (hsa_circ_0020397, hsa_circ_0005986, hsa_circ_0003028, hsa_circ_0006990) with possible new roles in RCC. In the experimental step, we investigated the expression of these four circRNAs in our RCC samples using quantitative real-time polymerase chain reaction. In the bioinformatics step, the differential expressed mRNAs (DEmRNAs), and miRNAs (DEmiRNAs) were obtained from the GEO datasets using the GEO2R tool. A protein-protein interaction network was constructed using the STRING database, and hub genes were identified by Cytoscape. Molecular pathways associated with hub genes were detected using KEGG pathway enrichment analysis. Then, we utilized the ToppGene database to detect the relationships between DEmiRNAs and hub genes. Furthermore, interactions between circRNAs and DEmiRNAs were predicted by the StarBase and circinteractome databases. Finally, a circRNA-DEmiRNA-hub gene triple network was constructed. Our results revealed that the expression of hsa_circ_0020397, hsa_circ_0005986, and hsa_circ_0006990 was downregulated in RCC tissues. Moreover, these circRNAs had a significantly lower expression in patients with a history of kidney disease. Furthermore, hsa_circ_0003028 and hsa_circ_0006990 showed higher expression in the tumor of participants with Lymphovascular/perineural invasion and oncocytoma type, respectively. Based on bioinformatic results, 15 circRNA-DEmiRNA-hub gene ceRNA regulatory axes were predicted, which included three hub genes, five miRNAs, and four selected circRNAs. In conclusion, the current work is the first to emphasize the expression of the hsa_circ_0020397, hsa_circ_0005986, hsa_circ_0003028, and hsa_circ_0006990 in RCC patients presents a novel perspective on the molecular processes underlying the pathogenic mechanisms of RCC.

Efficacy of autoantibodies combined with tumor markers in the detection of lung cancer

BACKGROUND

The purpose of this study was to explore the detection value of seven autoantibodies (TAAbs): p53, PGP9.5, SOX2, GBU4-5, MAGE A1, CAGE, and GAGE7 and three tumor markers: CYFRA21-1, NSE, and SCCA in the diagnosis of lung cancer.

METHODS

ELISA was used to detect the levels of the TAAbs, and chemiluminescence immunoassay was used to test the levels of the tumor markers. The diagnostic efficacy of the TAAbs combined with the tumor markers for lung cancer was evaluated by receiver operating characteristic (ROC) curves.

RESULTS

The positive rate of the combined detection of seven TAAbs and three tumor markers in lung cancer (37.8%) was higher than that in other three groups. The positive rates of SOX2, GAGE7, MAGE A1, CAGE, CYFRA21-1, and SCCA had differences among the four groups. Compared with the benign lung disease group, only GAGE7, CYFRA21-1, and SCCA differed among the groups. The combined sensitivity of the TAAbs was 29.07% (AUC, 0.594), the combined sensitivity of all the markers was 37.76% (AUC, 0.660 [p < 0.05]), and Youden's index was 0.196. In the lung cancer group, CYFRA21-1 had a significant difference in age and sex, and SOX2, MAGE A1, CYFRA21-1, NSE, and SCCA were significantly different in pathological type and TNM. In contrast, p53 and GBU4-5 showed no significant differences in age, sex, pathological type, and TNM.

CONCLUSIONS

The combined detection of seven TAAbs and three tumor markers could be useful in early diagnosis of lung cancer.

Circ_0030998 Restrains Cisplatin Resistance Through Mediating miR-1323/PDCD4 Axis in Non-small Cell Lung Cancer

We aimed to explore the underlying mechanism behind the cisplatin (DDP) resistance of non-small cell lung cancer (NSCLC) cells to identify novel potential therapeutic targets to overcome chemoresistance. Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot assay were applied to analyze RNA and protein expression, respectively. Cell Counting Kit-8 (CCK8) assay was conducted to analyze the DDP resistance of NSCLC cells. Colony formation assay and 5-Ethynyl-2'-deoxyuridine (EdU) assay were performed to analyze cell proliferation ability. Flow cytometry was applied to assess cell apoptosis. Cell migration and invasion were assessed by transwell assays. Cell glycolytic metabolism was analyzed using commercial kits. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to test the intermolecular target relations. Circular RNA_0030998 (circ_0030998) was down-regulated in DDP-resistant NSCLC tissues and cell lines. Circ_0030998 overexpression restrained the DDP resistance, proliferation, migration, invasion and glycolytic metabolism and triggered the apoptosis of NSCLC cells. Circ_0030998 overexpression contributed to the anti-tumor effect of DDP in the growth of xenograft tumor in vivo. MicroRNA-1323 (miR-1323) was a molecular target of circ_0030998 in NSCLC cells. Circ_0030998 overexpression-mediated effects on the DDP resistance and malignant properties of NSCLC cells were largely based on its negative regulation of miR-1323. MiR-1323 interacted with programmed cell death 4 (PDCD4). Circ_0030998 positively regulated PDCD4 expression partly through sponging miR-1323. MiR-1323 silencing restrained DDP resistance and progression of NSCLC partly through up-regulating PDCD4. Circ_0030998 suppressed DDP resistance and NSCLC progression depending on the regulation of miR-1323/PDCD4 axis.

Biogenesis, functions, and clinical implications of circular RNAs in non-small cell lung cancer

Lung cancer (LC) is the leading cause of cancer-related deaths worldwide, with high morbidity and mortality. Non-small cell lung cancer (NSCLC) is a major pathological type of LC and accounts for more than 80% of all cases. Circular RNAs (circRNAs) are a large class of non-coding RNAs (ncRNAs) with covalently closed-loop structures, a high abundance, and tissue-specific expression patterns. They participate in various pathophysiological processes by regulating complex gene networks involved in proliferation, apoptosis, migration, and epithelial-to-mesenchymal transition (EMT), as well as metastasis. A growing number of studies have revealed that the dysregulation of circRNAs contributes to many aspects of cancer progression, such as its occurrence, metastasis, and recurrence, suggesting their great potential as efficient and specific biomarkers in the diagnosis, prognosis, and therapeutic targeting of NSCLC. In this review, we systematically elucidate the characteristics, biogenesis, and functions of circRNAs and focus on their molecular mechanisms in NSCLC progression. Moreover, we highlight their clinical implications in NSCLC treatment.

Circ_0016760 Serves as a Cancer Promoter in Non-small Cell Lung Cancer Through miR-876-3p/NOVA2 Axis

Non-small cell lung cancer (NSCLC) is a serious threaten to human health globally. Circular RNAs (circRNAs) were testified to alter the progression of NSCLC. This work intended to investigate the functional role of circ_0016760 in NSCLC development and the potential mechanism. Expression of circ_0016760, microRNA (miR)-876-3p and NOVA alternative splicing regulator 2 (NOVA2) was determined via quantitative reverse transcription-PCT (qRT-PCR) or western blotting. Cell viability, clonogenicity and apoptosis were assessed by Cell Counting Kit-8 (CCK-8) assay, colony formation assay and flow cytometry, respectively. Transwell assay was performed to examine cell migration and invasion. Western blotting was also conducted to detect the levels of epithelial-to-mesenchymal transition (EMT)-related proteins. Role of circ_0016760 in vivo was evaluated via xenograft model assay. Moreover, the interaction between miR-876-3p and circ_0016760 or NOVA2 was verified by dual-luciferase reporter assay or RNA Immunoprecipitation (RIP) assay. Circ_0016760 and NOVA2 were upregulated, while miR-876-3p expression was decreased in NSCLC tissues and cells. Circ_0016760 depletion suppressed NSCLC cell proliferation and metastasis in vitro, as well as hampered tumor growth in vivo. Circ_0016760 acted as a sponge of miR-876-3p, and miR-876-3p could target NOVA2. Circ_0016760 might play vital roles in NSCLC by regulating miR-876-3p/NOVA2 axis. Circ_0016760 could promote the malignant development of NSCLC through miR-876-3p/NOVA2 axis, at least in part.

CircFOXP1: A novel serum diagnostic biomarker for non-small cell lung cancer

Background

Emerging evidence suggests that circular RNAs (circRNAs) were aberrantly expressed in the patients of non-small cell lung cancer (NSCLC). This study aims to evaluate the diagnostic value of potential serum biomarker in circRNAs.

Methods

Serum circRNAs were extracted and purified by RNA isolated kit and identified by quantitative real time-polymerase chain reaction (qRT-PCR) assay. We then performed a receiver operating characteristic (ROC) curve to estimate the diagnostic efficacy. The relationship between circRNA and clinic characteristics of patients was analyzed by SPSS 25.0. Univariate and multivariate analyses were also used to evaluate its diagnostic capability. The mechanism of circFOXP1 was further excavated by bioinformatics analysis.

Results

By performing qRT-PCR assay, we identified that circFOXP1 (hsa_circ_0008234) and conventional tumor markers (carcinoembryonic antigen (CEA) and cytokeratin fragment 21–1 (CYFRA21-1)) were all significantly overexpressed in the serum of patients with NSCLC when compared with healthy controls ( P < 0.05). While the ROC curves analysis demonstrated that area under the curve of circFOXP1 was obviously superior to CEA and CYFRA21-1, which exerted more diagnostic advantage. Univariate and multivariate analyses revealed that serum circFOXP1 was an independent diagnostic molecule, and was significantly correlated with T stage and lymphatic metastasis in NSCLC ( P < 0.05). Mechanistically, circFOXP1 might target hsa-miR-370-3p and hsa-miR-18a-5p, and be involved in vascular endothelial growth factor signaling pathways to regulate proliferative and metastasis processes.

Conclusion

Our results highlight the preferable diagnostic potential of serum circFOXP1 in NSCLC.

A novel circ_MACF1/miR-942-5p/TGFBR2 axis regulates the functional behaviors and drug sensitivity in gefitinib-resistant non-small cell lung cancer cells

BACKGROUND

Resistance to gefitinib remains a major obstacle for the successful treatment of non-small cell lung cancer (NSCLC) with epidermal growth factor receptor (EGFR) mutations. In this paper, we studied the precise actions of circular RNA (circRNA) microtubule actin crosslinking factor 1 (circ_MACF1) in gefitinib resistance.

METHODS

We established gefitinib-resistant NSCLC cells (PC9/GR and A549/GR). The levels of circ_MACF1, microRNA (miR)-942-5p, and transforming growth factor beta receptor 2 (TGFBR2) were gauged by quantitative real-time PCR (qRT-PCR) or western blot. Subcellular fractionation and Ribonuclease R (RNase R) assays were done to characterize circ_MACF1. Cell survival, proliferation, colony formation, apoptosis, migration, and invasion were detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 5-Ethynyl-2'-Deoxyuridine (EdU), colony formation, flow cytometry, and transwell assays, respectively. Dual-luciferase reporter assays were used to verify the direct relationship between miR-942-5p and circ_MACF1 or TGFBR2. The xenograft assays were used to assess the role of circ_MACF1 in vivo.

RESULTS

Circ_MACF1 was down-regulated in A549/GR and PC9/GR cells. Overexpression of circ_MACF1 repressed proliferation, migration, invasion, and promoted apoptosis and gefitinib sensitivity of A549/GR and PC9/GR cells in vitro, as well as inhibited tumor growth under gefitinib in vivo. Circ_MACF1 directly targeted miR-942-5p, and miR-942-5p mediated the regulatory effects of circ_MACF1. TGFBR2 was identified as a direct and functional target of miR-942-5p. Circ_MACF1 modulated TGFBR2 expression through miR-942-5p.

CONCLUSION

Our findings demonstrated that circ_MACF1 regulated cell functional behaviors and gefitinib sensitivity of A549/GR and PC9/GR cells at least partially by targeting miR-942-5p to induce TGFBR2 expression.

Circ_0017639 facilitates proliferative, migratory, and invasive potential of non-small cell lung cancer (NSCLC) cells via PI3K/AKT signaling pathway

Non-small cell lung cancer (NSCLC) has increased morbidity and mortality rate worldwide. The current NSCLS therapies are associated with poor outcomes and need further improvement. CircRNAs were shown to regulate NSCLC progression. However, little is known re garding the functions and mechanisms of circ_0017639 in NSCLC, which requires further extensive studies. The circ_0017639 expression in NSCLC tissues and cell lines was evaluated via qRT-RCR. Moreover, using ectopic plasmid incorporation and shRNA assays, we analyzed the circ_0017639-mediated cellular proliferative, migratory and invasive processes in NSCLC cell lines, using CCK-8, EdU, and transwell assays. Furthermore, the core proteins (p-PI3K, PI3K, p-AKT, and AKT) levels of the PI3K/AKT signaling cascade were investigated via immunoblotting. Finally, we tested the functional role of circ_0017639 by examining its regulation of xenograft tumor growths in nude mice in vivo. Circ_0017639 expression was remarkably high in the NSCLC tissues and cell lines. The transfection experiments showed that circ_0017639 overexpression was able to promote proliferative, migratory, and invasive properties of NSCLC cells, while sh-circ_0017639 showed opposing effects. We further showed that circ_0017639 knockdown suppressed the cellular development via PI3K/AKT cascade inactivation. Additionally, in-vivo experiment in nude mice demonstrated that sh-circ_0017639 could reduce the tumor growth of NSCLC. Circ_0017639 may promote the development of NSCLC by accelerating NSCLC metastasis through stimulating the PI3K/AKT cascade.

Identification of Differentially Expressed Circular RNAs as miRNA Sponges in Lung Adenocarcinoma

Background

Circular RNAs (circRNAs) may function as the decoys for microRNAs (miRNAs) or proteins, the templates for translation, and the sources of pseudogene generation. The purpose of this study is to determine the diagnostic circRNAs, which are related to lung adenocarcinoma (LUAD), that adsorb miRNAs on the basis of the competing endogenous RNA (ceRNA) hypothesis.

Methods

The differentially expressed circRNAs (DEcircRNAs) in LUAD were revealed by the microarray data (GSE101586 and GSE101684) that were obtained from the Gene Expression Omnibus (GEO) database. The miRNAs that were targeted by the DEcircRNAs were predicted with the CircInteractome, and the target mRNAs of the miRNAs were found by the miRDB and the TargetScan. The ceRNA network was built by the Cytoscape. The potential biological roles and the regulatory mechanisms of the circRNAs were investigated by the Gene Ontology (GO) enrichment analysis and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The expression of the host genes of circRNAs was examined by the Ualcan. The survival analysis was performed by the Kaplan-Meier plotter.

Results

In comparison with normal lung tissues, LUAD tissues contained 7 overlapping cancer-specific DEcircRNAs with 294 miRNA response elements (MREs). Among the 7 DEcircRNAs, 3 circRNAs (hsa_circ_0072088, hsa_circ_0003528, and hsa_circ_0008274) were upregulated and 4 circRNAs (hsa_circ_0003162, hsa_circ_0029426, hsa_circ_0049271, and hsa_circ_0043256) were downregulated. A circRNA-miRNA-mRNA regulatory network, which included 33 differentially expressed miRNAs (DEmiRNAs) and 2007 differentially expressed mRNAs (DEmRNAs), was constructed. These mRNAs were enriched in the biological function of cell-cell adhesion, response to hypoxia, and stem cell differentiation and were involved in the PI3K-Akt signaling, HIF-1 signaling, and cAMP signaling pathways.

Conclusion

Our results indicated that 7 DEcircRNAs could have diagnostic value for LUAD. Additionally, the circRNAs-mediated ceRNA network might provide a novel perspective into unraveling the pathogenesis and progression of LUAD.

Circular RNA _0015278 inhibits the progression of non-small cell lung cancer through regulating the microRNA 1278/SOCS6 gene axis

Background

Non-small cell lung cancer (NSCLC) is one of the most lethal malignancies worldwide. Deepening understanding of the pathogenesis of NSCLC is quite important for its treatment. Circular (circ) RNA_0015278 has been found to be downregulated in NSCLC, but its role in NSCLC and the underlying regulatory mechanism is unknown.

Methods

Circ_0015278, microRNA (miR)-1278 and SOCS6 were analyzed with real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) or western blot. Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) staining were used to evaluate cell proliferation. The colony forming capacity and invasion of NSCLC cells were assessed with colony formation and transwell assays, respectively. The interaction among circ_0015278, miR-1278, and SOCS6 was evaluated using luciferase, receptor interacting protein (RIP), and RNA-pull down assays. Cell apoptosis was analyzed using flow cytometry. A subcutaneous NSCLC xenograft mouse model was established for evaluating circ_0015278-mediated effects on the growth of NSCLC in vivo.

Results

Circ_0015278 was downregulated in NSCLC tissues and cells, and its reduced expression indicated poor prognosis. Overexpression of circ_0015278 restrained the proliferation, colony formation, invasion, and epithelial-mesenchymal transition (EMT) of NSCLC cells and induced NSCLC cell apoptosis. Moreover, overexpression of circ_0015278 inhibited the growth of NSCLC in vivo. Mechanically, circ_0015278 acted as an miR-1278 sponge to reduce its quantity, and miR-1278 targeted SOCS6 to inhibit its expression in NSCLC cells. Circ_0015278 promoted SOCS6 expression by sponging miR-1,278 in NSCLC cells. Overexpression of circ_0015278 attenuated the malignant phenotypes of NSCLC through sponging miR-1278 and consequently promoting SOCS6 expression.

Conclusions

We demonstrated for the first time that circ_0015278 attenuated the progression of NSCLC via targeting the miR-1278/SOCS6 axis, which provides potential diagnostic biomarkers and therapeutic targets.

Bioinformatics Analysis Predicts hsa_circ_0026337/miR-197-3p as a Potential Oncogenic ceRNA Network for Non-small Cell Lung Cancers

BACKGROUND

Circular RNAs (circRNAs) play an essential role in developing tumors, but their role in non-small cell lung cancer (NSCLC) is unclear. Thus, the present study explored the possible molecular mechanism of circRNAs in NSCLC.

METHODS

Three circular RNA (circRNA) microarray datasets were downloaded from the Gene Expression Omnibus (GEO) database. Differential expressions of circRNAs (DECs) were identified in NSCLC tissue and compared to adjacent healthy tissue. The online cancer-specific circRNA database (CSCD) was used for the analysis of the DECs function. Protein-protein interaction (PPI) network, Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), Cytoscape, and UALCAN were used to predict the critical nodes and perform patient survival analysis, respectively. The interaction between the DECs, the predicted miRNAs, and hub genes was also determined. Finally, the circRNA-miRNA-mRNA network was established.

RESULTS

The expression of hsa_circ_0049271, hsa_circ_0026337, hsa_circ_0043256, and hsa_circ_0008234 was decreased in NSCLC tissues. The Encyclopedia of RNA Interactomes (ENCORI) and CSCD database results showed that hsa_circ_0026337 was found to sponge with miR-1193, miR-197-3p, miR-3605-5p, miR-433-3p, and miR-652-3p, and hsa_circ_0043256 to sponge with miR-1252-5p, miR-494-3p, and miR-558, respectively. Subsequently, 100 mRNAs were predicted to bind with these seven miRNA response elements (MREs). The GO analysis and KEGG pathway revealed that these 100 MREs might be involved in "histone deacetylase binding" and "cellular senescence". PPI network and Cytoscape identified the top ten hub genes. Survival analysis data showed that the low expression of hsa_circ_0026337 was significantly associated with shortened survival time in NSCLC (P=0.037), which increased the expression level of hsa-miR-197-3p, thereby inhibiting the translation of specific proteins.

CONCLUSION

This study examined the circRNA-miRNA-mRNA regulatory network associated with NSCLC and explored the potential functions of DECs in the network to elucidate the mechanisms underlying disease progression in NSCLC.

Circular RNA: A novel type of biomarker for glioma (Review)

With the rapid development of sequencing technologies, the characteristics and functions of circular RNAs (circRNAs) in different tissues, and their underlying pathophysiological mechanisms, have been identified. circRNAs are significantly enriched in the brain and are continually expressed from the embryonic stage to the adult stage in rats. Previous studies have reported that certain circRNAs are differentially expressed in glioma and regulate a number of biological processes, such as cell proliferation, metastasis and oncogenesis of glioma. Furthermore, certain circRNAs have been associated with tumor size, World Health Organization tumor grade and poor prognosis in patients with glioma. It has been hypothesized that circRNAs may be involved in the onset and progression of glioma through transcriptional regulation, protein translation and binding to microRNAs. These properties and functions suggest the potential of circRNAs as prognostic biomarkers and therapeutic targets for glioma. For the present review, published studies were examined from PubMed, Embase, Cochrane Central and the reference lists of the retrieved articles. The aim of the present review was to summarize the progress of circRNA research in glioma, discuss the potential diagnostic and prognostic values, and the roles of circRNAs in glioma, and provide a novel theoretical basis and research concepts for the prediction, diagnosis and treatment of glioma.

Circular RNA circ_0003028 contributes to tumorigenesis by regulating GOT2 via miR-1298-5p in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) is a common malignant tumor, with high morbidity and mortality. Circular RNA (circRNA) circ_0003028 was reported to be upregulated in NSCLC. This study is designed to explore the role and mechanism of circ_0003028 on NSCLC progression. In this work, circ_0003028, microRNA-1298-5p (miR-1298-5p), and glutamic oxaloacetic transaminase 2 (GOT2) level were detected by real-time quantitative polymerase chain reaction (RT-qPCR). The localization of circ_0003028 was analyzed by subcellular fractionation assay. Cell proliferation, colony number, cell cycle progression, apoptosis, migration, invasion, and angiogenesis were measured by Cell Counting Kit-8 (CCK-8), colony formation, flow cytometry, transwell, and tube formation assays. Protein levels of Beclin1, light chain 3 (LC3)-II/LC3-I, GOT2, proliferating cell nuclear antigen (PCNA) were examined by western blot assay. The binding relationship between miR-1298-5p and circ_0003028 or GOT2 was predicted by circular RNA Interactome or starbase and then verified by dual-luciferase reporter, RNA Immunoprecipitation (RIP), and RNA pull-down assays. The biological role of circ_0003028 on NSCLC tumor growth was examined by the xenograft tumor model in vivo. We reported that circ_0003028 and GOT2 were upregulated, and miR-1298-5p was decreased in NSCLC tissues and cells. Moreover, circ_0003028 knockdown curbed cell proliferative ability, migration, invasion, angiogenesis, and facilitate apoptosis and autophagy in NSCLC cells in vitro. Mechanical analysis discovered that circ_0003028 regulated GOT2 expression by sponging miR-1298-5p. Circ_0003028 silencing hindered the cell growth of NSCLC in vivo. Taken together, circ_0003028 knockdown could suppress NSCLC progression partly by regulating the miR-1298-5p/GOT2 axis, providing an underlying therapeutic target for NSCLC.

Construction of a circRNA-miRNA-mRNA Regulatory Network Reveals Potential Mechanism and Treatment Options for Osteosarcoma

Background

Osteosarcoma is a common malignant primary bone tumor in adolescents and children. Numerous studies have shown that circRNAs were involved in the proliferation and invasion of various tumors. However, the role of circRNAs in osteosarcoma remains unclear. Here, we aimed to explore the regulatory network among circRNA-miRNA-mRNA in osteosarcoma.

Methods

The circRNA (GSE140256), microRNA (GSE28423), and mRNA (GSE99671) expression profiles of osteosarcoma were collected from the Gene Expression Omnibus (GEO) database. Differentially expressed circRNAs, miRNAs and mRNAs were identified. CircRNA-miRNA interactions and miRNA-mRNA interactions were determined by Circular RNA Interactome (CircInteractome) database and microRNA Data Integration Portal (mirDIP) database, respectively. Then, we constructed a regulatory network. Function enrichment analysis of miRNA and mRNA was performed by DIANA-miRPath v3.0 and Metascape database, respectively. mRNAs with significant prognostic value were identified based on expression profiles from The Cancer Genome Atlas (TCGA) database, and we constructed a subnetwork for them. To make the most of the network, we used the CLUE database to predict potential drugs for the treatment of osteosarcoma based on mRNA expression in the network. And we used the STITCH database to analyze and validate the interactions among these drugs and mRNAs, and to further screen for potential drugs.

Results

A total of 9 circRNAs, 19 miRNAs, 67 mRNAs, 54 pairs of circRNA-miRNA interactions and 110 pairs of miRNA-mRNA interactions were identified. A circRNA-miRNA-mRNA network was constructed. Function enrichment analysis indicated that these miRNAs and mRNAs in the network were involved in the process of tumorigenesis and immune response. Among these mRNAs, STC2 and RASGRP2 with significantly prognostic value were identified, and we constructed a subnetwork for them. Based on mRNA expression in the network, three potential drugs, quinacridine, thalidomide and zonisamide, were screened for the treatment of osteosarcoma. Among them, quinacridine and thalidomide have been proved to have anti-tumor effects in previous studies, while zonisamide has not been reported. And a corresponding drug-protein interaction network was constructed.

Conclusion

Overall, we constructed a circRNA-miRNA-mRNA regulatory network to investigate the possible mechanism in osteosarcoma, and predicted that quinacridine, thalidomide and zonisamide could be potential drugs for the treatment of osteosarcoma.

Emerging landscape of circHIPK3 and its role in cancer and other diseases (Review)

Circular RNAs (circRNAs) are a special class of recently re‑discovered RNAs, which are covalently closed ring RNA molecules. circRNAs have been reported to possess multiple functions and are considered crucial regulators of several processes, and are therefore gaining increasing attention. In recent years, increasing evidence has shown that circRNAs are implicated in several crucial biological processes via regulation of gene expression, and their dysregulation is also associated with the development of numerous diseases, particularly acting as oncogenic or tumor‑suppressor molecules in cancer. Furthermore, circRNAs are involved in cell proliferation, differentiation, apoptosis, invasion and metastasis. In the present review, the biogenesis and functions of circRNAs are described, with a focus on the most recent research advances and the emerging roles of circular homeodomain‑interacting protein kinase 3 (circHIPK3) in human diseases. The present review may provide novel avenues for research on the roles of circHIPK3 as a clinical diagnostic and prognostic biomarker, as well as highlighting promising therapeutic targets for certain diseases and cancer.

Differential Expression and Bioinformatics Analysis of circRNA in Non-small Cell Lung Cancer

Circular RNA (CircRNA) plays an important role in tumorigenesis and progression of non-small cell lung cancer (NSCLC), but the pathogenesis of NSCLC caused by circRNA has not been fully elucidated. This study aimed to investigate differentially expressed circRNAs and identify the underlying pathogenesis hub genes of NSCLC by comprehensive bioinformatics analysis. Data of gene expression microarrays (GSE101586, GSE101684, and GSE112214) were downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed circRNAs (DECs) were obtained by the “limma” package of R programs and the overlapping operation was implemented of DECs. CircBase database and Cancer-Specific CircRNA database (CSCD) were used to find miRNAs binding to DECs. Target genes of the found miRNAs were identified utilizing Perl programs based on miRDB, miRTarBase, and TargetScan databases. Functional and enrichment analyses of selected target genes were performing using the “cluster profiler” package. Protein-protein interaction (PPI) network was constructed by the Search Tool for the STRING database and module analysis of selected hub genes was performed by Cytoscape 3.7.1. Survival analysis of hub genes were performed by Gene Expression Profiling Interactive Analysis (GEPIA). Respectively, 1 DEC, 249 DECs, and 101 DECs were identified in GSE101586, GSE101684, and GSE112214. A total of eight overlapped circRNAs, 43 miRNAs and 427 target genes were identified. Gene Ontology (GO) enrichment analysis showed these target genes were enriched in biological processes of regulation of histone methylation, Ras protein signal transduction and covalent chromatin modification etc. Pathway enrichment analysis showed these target genes are mainly involved in AMPK signaling pathway, signaling pathways regulating pluripotency of stem cells and insulin signaling pathway etc. A PPI network was constructed based on 427 target genes of the 43 miRNAs. Ten hub genes were found, of which the expression of MYLIP, GAN, and CDC27 were significantly related to NSCLC patient prognosis. Our study provide a deeper understanding the circRNAs-miRNAs-target genes by bioinformatics analysis, which may provide novel insights for unraveling pathogenesis of NSCLC. MYLIP, GAN, and CDC27 genes might serve as novel biomarker for precise treatment and prognosis of NSCLC in the future.