Circular RNA circ_0074026 indicates unfavorable prognosis for patients with glioma and facilitates oncogenesis of tumor cells by targeting miR‐1304 to modulate ERBB4 expression

Exploring the impact of circRNAs on cancer glycolysis: Insights into tumor progression and therapeutic strategies

Cancer cells exhibit altered metabolic pathways, prominently featuring enhanced glycolytic activity to sustain their rapid growth and proliferation. Dysregulation of glycolysis is a well-established hallmark of cancer and contributes to tumor progression and resistance to therapy. Increased glycolysis supplies the energy necessary for increased proliferation and creates an acidic milieu, which in turn encourages tumor cells' infiltration, metastasis, and chemoresistance. Circular RNAs (circRNAs) have emerged as pivotal players in diverse biological processes, including cancer development and metabolic reprogramming. The interplay between circRNAs and glycolysis is explored, illuminating how circRNAs regulate key glycolysis-associated genes and enzymes, thereby influencing tumor metabolic profiles. In this overview, we highlight the mechanisms by which circRNAs regulate glycolytic enzymes and modulate glycolysis. In addition, we discuss the clinical implications of dysregulated circRNAs in cancer glycolysis, including their potential use as diagnostic and prognostic biomarkers. All in all, in this overview, we provide the most recent findings on how circRNAs operate at the molecular level to control glycolysis in various types of cancer, including hepatocellular carcinoma (HCC), prostate cancer (PCa), colorectal cancer (CRC), cervical cancer (CC), glioma, non-small cell lung cancer (NSCLC), breast cancer, and gastric cancer (GC). In conclusion, this review provides a comprehensive overview of the significance of circRNAs in cancer glycolysis, shedding light on their intricate roles in tumor development and presenting innovative therapeutic avenues.

Circ-PITX1 promotes non-small-cell lung cancer progression through regulating ETS1 expression via miR-615-5p

BACKGROUND

Circular RNAs (circRNAs), produced by reverse splicing, act as important players in human cancers. We aimed to assess the biological functions of circRNA pituitary homeobox 1 (circ-PITX1) in non-small-cell lung cancer (NSCLC).

METHODS

qRT-PCR was employed to determine RNA expression. Biological behaviors of NSCLC cells were assessed by CCK-8, colony formation, EdU assay, flow cytometry, wound healing, and transwell assays. Glutamine catabolism was examined via the measurement of glutamine consumption, α-ketoglutarate levels, as well as ATP levels. Protein levels were detected by western blot assays. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to reveal the mechanism responsible for circ-PITX1 regulating NSCLC cell malignancy. The murine xenograft model was established to investigate circ-PITX1's effect on tumor formation.

RESULTS

Circ-PITX1 was overexpressed in NSCLC tissue samples and cells. Its low expression repressed NSCLC cell proliferation and motility. Moreover, our data revealed its downregulation inhibited glutamine catabolism and tumor formation and promoted cell apoptosis. In addition, circ-PITX1 bound to miR-615-5p, and its inhibitory effect on tumor cellular behaviors could be reversed after decreasing miR-615-5p expression. The miRNA targeted E26 transformation specific-1 (ETS1), whose upregulation abolished miR-615-5p overexpression-induced effects in NSCLC cells. Furthermore, circ-PITX1 positively modulated ETS1 production through interaction with miR-615-5p.

CONCLUSION

Circ-PITX1 facilitated NSCLC progression via modulating miR-615-5p/ETS1 pathway.

Roles of circular RNAs in regulating the development of glioma

BACKGROUND

Glioma is the most common malignant tumor in the central nervous system. In patients with glioma, the prognosis is poor and median survival is only 12-15 months. With the recent development of sequencing technology, important roles of noncoding RNAs are being discovered in cells, especially those of circular RNAs (circRNAs). Because circRNAs are stable, abundant, and highly conserved, they are regarded as novel biomarkers in the early diagnosis and prognosis of diseases.

PURPOSE

In this review, roles and mechanisms of circRNAs in the development of glioma are summarized.

METHODS

This paper collects and reviews relevant PubMed literature.

CONCLUSION

Several classes of circRNAs are highly expressed in glioma and are associated with malignant biological behaviors of gliomas, including proliferation, migration, invasion, apoptosis, angiogenesis, and drug resistance. Further studies are needed to clarify the roles of circRNAs in glioma and to determine whether it is possible to increase therapeutic effects on tumors through circRNA intervention.

Isoliquiritigenin regulates the circ_0002860/miR-431-5p/RAB9A axis to function as a tumor inhibitor in melanoma

Background:

Isoliquiritigenin (ISL) presents antitumor effects against melanoma cells. It is known that various circular RNAs (circRNAs) are involved in the development of melanoma. Therefore, the present study aims to investigate the molecular mechanisms of ISL and circ_0002860.

Methods:

Circ_0002860, microRNA-431-5p (miR-431-5p) and member RAS oncogene family (RAB9A) were detected through reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assay. Cell viability was examined via cell counting kit-8 assay. The proliferation ability was assessed using colony formation assay. Cell apoptosis and cell cycle were determined by flow cytometry. Transwell assay was used for detection of migration and invasion. Western blot was conducted for protein analysis. Target binding was confirmed via dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. In vivo research was performed through xenograft tumor assay.

Results:

Circ_0002860 was downregulated by ISL in melanoma cells. ISL-induced inhibitory effects on cell proliferation, cell cycle progression, migration and invasion were alleviated by circ_0002860 overexpression. MiR-431-5p was a target of circ_0002860. Circ_0002860 eliminated the ISL-induced tumor inhibition via sponging miR-431-5p in melanoma cells. Circ_0002860 elevated the RAB9A level by targeting miR-431-5p. The function of ISL was related to miR-431-5p/RAB9A axis in melanoma progression. Tumor growth was reduced by ISL in vivo through downregulating circ_0002860 to regulate miR-431-5p and RAB9A levels.

Conclusion:

The current data indicates that ISL suppressed cell malignant progression of melanoma via targeting the circ_0002860/miR-431-5p/RAB9A pathway.

Exosomal miR-1304-3p promotes breast cancer progression in African Americans by activating cancer-associated adipocytes

Breast cancer displays disparities in mortality between African Americans and Caucasian Americans. However, the exact molecular mechanisms remain elusive. Here, we identify miR-1304-3p as the most upregulated microRNA in African American patients. Importantly, its expression significantly correlates with poor progression-free survival in African American patients. Ectopic expression of miR-1304 promotes tumor progression in vivo. Exosomal miR-1304-3p activates cancer-associated adipocytes that release lipids and enhance cancer cell growth. Moreover, we identify the anti-adipogenic gene GATA2 as the target of miR-1304-3p. Notably, a single nucleotide polymorphism (SNP) located in the miR-1304 stem-loop region shows a significant difference in frequencies of the G allele between African and Caucasian American groups, which promotes the maturation of miR-1304-3p. Therefore, our results reveal a mechanism of the disparity in breast cancer progression and suggest a potential utility of miR-1304-3p and the associated SNP as biomarkers for predicting the outcome of African American patients.

Exploring the Correlation of Abnormal CXCL9 Expression with Immune Infiltration in Glioma and Patient Prognosis Based on TCGA and GTEx Databases

In this study, we intend to identify key immune-related genes (IRGs) in gliomas using the TCGA and GTEx databases. Following collection of the RNA-seq data of lower-grade glioma (LGG) and glioblastoma (GBM) patients from the TCGA and GTEx databases, the differentially expressed IRGs (DE-IRGs) were screened. The ESTIMATE algorithm was utilized to evaluate StromalScore and ImmuneScore of LGG and GBM samples and a multifactorial Cox risk model was constructed to identify the related risk genes. The core IRGs of LGG and GBM were screened through a PPI network, followed by exploration of their correlation with glioma prognosis. The relationship between IRGs and immune cells in LGG and GBM was detected. In vitro assays were performed to detect the effect of CXCL9 on glioma cell development. We screened 403 and 492 DE-IRGs in LGG and GBM. StromalScore and ImmuneScore were related to overall survival in LGG, but not in GBM. CXCL9 was identified as a core gene in LGG and GBM and shared association with the prognosis of gliomas. Furthermore, a correlation was found between CXCL9 and immune infiltration of LGG and GBM. Glioma cell proliferation and invasion could be inhibited by silencing of CXCL9. Overall, CXCL9 is correlated to the prognosis of glioma patients and may accelerate glioma development via immune regulation.

CircRNAs in Tumor Radioresistance

Circular RNAs (circRNAs) are endogenous, non-coding RNAs, which are derived from host genes that are present in several species and can be involved in the progression of various diseases. circRNAs’ leading role is to act as RNA sponges. In recent years, the other roles of circRNAs have been discovered, such as regulating transcription and translation, regulating host genes, and even being translated into proteins. As some tumor cells are no longer radiosensitive, tumor radioresistance has since become a challenge in treating tumors. In recent years, circRNAs are differentially expressed in tumor cells and can be used as biological markers of tumors. In addition, circRNAs can regulate the radiosensitivity of tumors. Here, we list the mechanisms of circRNAs in glioma, nasopharyngeal carcinoma, and non-small cell lung cancer; further, these studies also provide new ideas for the purposes of eliminating radioresistance in tumors.

ErbB4 in the brain: Focus on high grade glioma

The epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases (RTKs) consists of EGFR, ErbB2, ErbB3, and ErbB4. These receptors play key roles in cell proliferation, angiogenesis, cell migration, and in some cases, tumor promotion. ErbB4 is a unique member of the EGFR family, implicated not only in pro-tumorigenic mechanisms, such as cell proliferation and migration, but also in anti-tumorigenic activities, including cell differentiation and apoptosis. ErbB4 is differentially expressed in a wide variety of tissues, and interestingly, as different isoforms that result in vastly different signalling outcomes. Most studies have either ignored the presence of these isoforms or used overexpression models that may mask the true function of ErbB4. ErbB4 is widely expressed throughout the body with significant expression in skeletal tissue, mammary glands, heart, and brain. Knockout models have demonstrated embryonic lethality due to disrupted heart and brain development. Despite high expression in the brain and a critical role in brain development, remarkably little is known about the potential signalling activity of ErbB4 in brain cancer.This review focuses on the unique biology of ErbB4 in the brain, and in particular, highlights brain cancer research findings. We end the review with a focus on high grade gliomas, primarily glioblastoma, a disease that has been shown to involve EGFR and its mutant forms. The role of the different ErbB4 isotypes in high grade gliomas is still unclear and future research will hopefully shed some light on this question.

CircRNA: An emerging star in the progression of glioma

Circular RNAs (circRNAs), a class of single-stranded noncoding RNAs with a covalently closed loop structure, are recognized as promising biomarkers and targets for diagnosing and treating dozens of diseases, especially cancers. CircRNAs are extremely stable, abundant and conserved and have tissue- or developmental stage-specific expression. Currently, the biogenesis and biological functions of circRNAs have been increasingly revealed with deep sequencing and bioinformatics. Studies have indicated that circRNAs are frequently expressed in brain tissues and that their expression levels change in different stages of neural development, suggesting that circRNAs may play an important role in diseases of the nervous system, such as glioma. However, because the biogenesis and functions of circRNAs do not depend on a single mechanism but are coregulated by multiple factors, it is necessary to further explore the underlying mechanisms. In this review, we summarized the classification, mechanisms of biogenesis and biological functions of circRNAs. Meanwhile, we emphatically expounded on the process of abnormal expression of circRNAs, methods used in circRNA research, and their effects on the malignant biological capabilities of glioma.

Circ_0001588 Upregulates ERBB4 to Promote Glioma Malignant Progression Through Sponging miR-1281

Circular RNA (circRNA) plays a crucial part in glioma progression. However, the function of circ_0001588 in glioma development is still unknown. The study aims to reveal the role of circ_0001588 in glioma malignant progression and the inner molecular mechanism. The RNA expressions of circ_0001588, microRNA-1281 (miR-1281), and erb-b2 receptor tyrosine kinase 4 (ERBB4) were detected by qRT-PCR. Protein expression was checked by western blot analysis or immunohistochemistry assay. Cell proliferation was investigated by cell counting kit-8 and colony formation assays. Flow cytometry, transwell, and tube formation assays were used to detect cell apoptosis, cell migration, and invasion as well as angiogenesis, respectively. The binding relationship between miR-1281 and circ_0001588 or ERBB4 was identified by dual-luciferase reporter and RNA immunoprecipitation assays. Mouse model assay was performed to confirm the effect of circ_0001588 knockdown on tumor formation in vivo. Circ_0001588 and ERBB4 expressions were significantly upregulated, while miR-1281 was downregulated in glioma tissues and cells compared with control groups. Circ_0001588 expression was closely related to tumor size and WHO grade of glioma. Decreased expression of circ_0001588 in glioma cells led to significant decreases of cell proliferation, migration, invasion, and tube formation and an increase of cell apoptosis. Additionally, downregulation of miR-1281, a target miRNA of circ_0001588, rescued circ_0001588 knockdown-mediated effects. MiR-1281 also inhibited glioma malignant progression by targeting ERBB4. Importantly, circ_0001588 regulated ERBB4 expression by interacting with miR-1281. Furthermore, circ_0001588 depletion suppressed tumor formation in vivo. Circ_0001588 acted as an oncogene in glioma malignant progression by miR-1281/ERBB4 pathway, suggesting the potential of circ_0001588 as a therapeutic target for glioma.

[Research Progress in CircRNA and Radiotherapy Resistance of Non-small Cell Lung Cancer]

As the main type of lung cancer, non-small cell lung cancer (NSCLC) is a common cancer which is characterized by low 5-year survival rate and worse prognosis. Nowadays, some studies show that the low survival rate and worse prognosis are due to the resistance to radiotherapy caused by circRNA. Therefore, to find out the relationship between circRNA and radiotherapy resistance of NSCLC was imoprtant. According to research the relevant literatures, the relationship between circRNA and radiotherapy resistance of NSCLC was explored. CircRNA plays an important role in the invasion, metastasis, proliferation and treatment resistance of NSCLC. The radiation resistance of tumor cells induced by circRNA has become a crucial problem in radiotherapy. CircRNA plays an important role in the radiotherapy resistance of NSCLC.
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CircSOS2 promotes cervical squamous cell carcinoma by regulation of proliferation, cell cycle, apoptosis, migration, invasion, and glycolysis by targeting miR-543/FNDC3B axis

BACKGROUND

Cervical squamous cell carcinoma (SCC) is a common subtype of cervical cancer. Circular RNAs (circRNAs) have been demonstrated as vital regulators in gene regulation and malignant tumor progression. Therefore, the precise role of circular RNA salt overly-sensitive 2 (circSOS2) was investigated in SCC.

METHODS

The relative expression levels of circSOS2, microRNA-543 (miR-543), and Fibronectin type III domain containing 3B (FNDC3B) were determined by real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot assays. The correlation between percent survival times of SCC patients and circSOS2 level was presented by Kaplan-Meier Plotter analysis. The cell proliferation was measured by MTT and colony-forming assays. Flow cytometry assay was used to assess apoptosis and cell cycle distribution. The migration and invasion were measured by transwell assay. The glycolysis was analyzed by extracellular acidification rate (ECAR) assay, Glucose Assay Kit, and Lactate Assay Kit. The interaction relationship between miR-543 and circSOS2 or FNDC3B was analyzed by dual-luciferase reporter, RNA immunoprecipitation (RIP), and RNA pull-down assays. A xenograft experiment was established to clarify the functional role of circSOS2 inhibition in viv.

RESULTS

CircSOS2 was highly expressed in SCC tissues and cells; besides, its expression level was closely associated with poor prognosis. Loss-of-functional experiments revealed that suppression of circSOS2 repressed proliferation, cell cycle process, migration, invasion, and glycolysis while induced apoptosis in SCC cells, which was overturned by inhibition of miR-543. In addition, miR-543 was downregulated and negatively correlated with circSOS2 expression in SCC tissues. We also found that overexpression of miR-543 impeded proliferation, cell cycle process, migration, invasion, and glycolysis while induced apoptosis in SCC cells by targeting FNDC3B. The silencing of circSOS2 impeded tumorigenesis in vivo.

CONCLUSION

CircSOS2 conferred an oncogenic function in SCC by regulation of proliferation, cell cycle, apoptosis, migration, invasion, and glycolysis of SCC cells, which was contributed to its interactions with miR-543 and FNDC3B.

Circular RNA circ_0001162 promotes cell proliferation and invasion of glioma via the miR-936/ERBB4 axis

The biological modulatory roles of many circular RNAs (circRNAs) have been validated in glioma. The current study was designed to research the functional mechanism of circ_0001162 in glioma progression. The quantitative real-time polymerase chain reaction (qRT-PCR) was used for assaying the levels of circ_0001162 and microRNA-936 (miR-936). Cell proliferation and colony formation abilities were evaluated via 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide (MTT) and colony formation assay, respectively. Transwell assay was applied to assess cell migration and invasion. The impact of circ_0001162 on glioma growth in vivo was performed using xenograft tumor assay. The target binding was affirmed via the dual-luciferase reporter and RNA pull-down assays. All protein expression levels were examined via Western blot. Circ_0001162 was an overexpressed circRNA in glioma. Circ_0001162 promoted glioma cell proliferation, colony formation, migration and invasion in vitro. Tumorigenesis of glioma in vivo was also enhanced by circ_0001162. Circ_0001162 could directly target miR-936 and the biological function of circ_0001162 in glioma was related to the inhibition of miR-936. ErbB2 receptor tyrosine kinase 4 (ERBB4) was a direct target of miR-936. Additionally, miR-936 inhibited the glioma development via targeting ERBB4. The miR-936/ERBB4 axis was responsible for the oncogenic role of circ_0001162 in glioma. The effects of circ_0001162 on glioma cells were also associated with the positive regulation of ERBB4. These results indicated that circ_0001162 contributed to the glioma progression via regulating the miR-936/ERBB4 axis, which laid a foundation for the pathomechanism and molecular treatment of glioma.

circMELK promotes glioblastoma multiforme cell tumorigenesis through the miR-593/EphB2 axis

A number of studies indicate that circular RNAs (circRNAs) play paramount roles in regulating the biological behavior of glioblastoma multiforme (GBM). In this study, we investigated the underlying mechanism of circMELK in GBM. Real-time PCRs were used to examine the expression of circMELK in glioma tissues and normal brain tissues (NBTs). Localization of circMELK in GBM cells was estimated by fluorescence in situ hybridization (FISH). Transwell migration and three-dimensional invasion assays were performed to examine glioma cell migration and invasion in vitro. Spheroid formation, clonogenicity, and cell viability assays were implemented to test the stemness of glioma stem cells (GSCs). The functions of circMELK in vivo were investigated in a xenograft nude-mouse model. We have proved that circMELK functions as a sponge for tumor suppressor microRNA-593 (miR-593) by RNA immunoprecipitation and circRNA precipitation assays, which targets the oncogenic gene Eph receptor B2 (EphB2). Dual-luciferase reporter assays were adopted to estimate the interactions between miR-593 and circMELK or EphB2. We demonstrated that circMELK was upregulated in GBM, acting as an oncogene and regulating GBM mesenchymal transition and GSC maintenance via sponging of miR-593. Furthermore, we found that EphB2 was involved in circMELK/miR-593 axis-induced GBM tumorigenesis. This function opens the opportunity for the development of a novel therapeutic target for the treatment of gliomas.

Competing Endogenous RNA Networks in Glioma

Gliomas are the most common and malignant primary brain tumors. Various hallmarks of glioma, including sustained proliferation, migration, invasion, heterogeneity, radio- and chemo-resistance, contribute to the dismal prognosis of patients with high-grade glioma. Dysregulation of cancer driver genes is a leading cause for these glioma hallmarks. In recent years, a new mechanism of post-transcriptional gene regulation was proposed, i.e., "competing endogenous RNA (ceRNA)." Long non-coding RNAs, circular RNAs, and transcribed pseudogenes act as ceRNAs to regulate the expression of related genes by sponging the shared microRNAs. Moreover, coding RNA can also exert a regulatory role, independent of its protein coding function, through the ceRNA mechanism. In the latest glioma research, various studies have reported that dysregulation of certain ceRNA regulatory networks (ceRNETs) accounts for the abnormal expression of cancer driver genes and the establishment of glioma hallmarks. These achievements open up new avenues to better understand the hidden aspects of gliomas and provide new biomarkers and potential efficient targets for glioma treatment. In this review, we summarize the existing knowledge about the concept and logic of ceRNET and highlight the emerging roles of some recently found ceRNETs in glioma progression.

Regulation of cell signaling pathways by circular RNAs and microRNAs in different cancers: Spotlight on Wnt/β-catenin, JAK/STAT, TGF/SMAD, SHH/GLI, NOTCH and Hippo pathways

Groundbreaking discoveries in molecular oncology have leveraged our understanding altogether to a new level. Mapping of plethora of cell signaling pathways has enabled researchers to drill down deep into the intermeshed regulatory networks which crosstalk to promote carcinogenesis and metastasis. More importantly, discovery of non-coding RNAs has added new layers of complexity to already complicated nature of cell signaling pathways. The discovery of circular RNAs (circRNAs) has opened the door to an ever-widening understanding of cellular processes that are controlled or influenced by circRNAs. In this review, we have summarized most recent advancements in our understanding related to interplay between circular RNAs and microRNAs for the regulation of NOTCH, Wnt/β-catenin, Hippo, SHH/GLI, JAK/STAT and TGF/SMAD pathways in different cancers.

CircRNAs as potential biomarkers for the clinicopathology and prognosis of glioma patients: a meta-analysis

BACKGROUND

An increasing number of studies have reported circular RNAs (circRNAs) as new potential biomarkers for the prognosis of gliomas. However, the overall prognostic value of circRNAs for glioma remains unclear. Therefore, this study is the first comprehensive evaluation of the clinicopathological and prognostic value of dysregulated circRNAs in the treatment of glioma patients.

METHODS

We systematically reviewed the online databases of PubMed, Web of Science, EMBASE, and Cochrane Library to identify studies that explored the relationship between circRNA expression and clinicopathological and prognostic factors in glioma through April 11, 2020. The quality of the included studies was evaluated by the Newcastle-Ottawa Scale (NOS) checklists. Clinicopathological features were assessed by pooled odds ratios (ORs) and 95% confidence intervals (CIs), and overall survival (OS) was assessed by hazard ratios (HRs) and 95% CIs.

RESULTS

Twenty-four eligible studies, including 22 studies of clinicopathological features, 1 diagnostic study, and 18 studies of prognosis, that included a total of 1390 patients were ultimately included in this study. Meta-analysis showed that highly expressed oncogenic circRNAs were significantly related to poor clinicopathological features (age: P = 0.026; tumor size: P ≤ 0.001; tumor grade: P ≤ 0.001; KPS: P = 0.012) and worse overall survival (OS) (HR = 2.01, 95% CI: 1.61-2.50, P ≤ 0.001). Moreover, we found that highly expressed tumor-suppressor circRNAs were related to better clinicopathological features (gender: P = 0.042; age: P = 0.014; tumor size: P = 0.022; tumor grade: P ≤ 0.001) and longer OS (HR = 2.70, 95% CI: 1.82-3.99, P ≤ 0.001).

CONCLUSIONS

In conclusion, there is a significant correlation between the dysregulated expression of circRNAs and the clinicopathology and prognosis of glioma patients.

CircPSMC3 alleviates the symptoms of PCOS by sponging miR-296-3p and regulating PTEN expression

Polycystic ovary syndrome (PCOS), the most common female endocrine disease that causes anovulatory infertility, still lacks promising strategy for the accurate diagnosis and effective therapeutics of PCOS attributed to its unclear aetiology. In this study, we determined the abnormal reduction in circPSMC3 expression by comparing the ovarian tissue samples of PCOS patients and normal individuals. The symptom relief caused by up-regulation of circPSMC3 in PCOS model mice suggested the potential for further study. In vitro functional experiments confirmed that circPSMC3 can inhibit cell proliferation and promote apoptosis by blocking the cell cycle in human-like granular tumour cell lines. Mechanism study revealed that circPSMC3 may play its role through sponging miR-296-3p to regulate PTEN expression. Collectively, we preliminarily characterized the role and possible insights of circPSMC3/miR-296-3p/PTEN axis in the proliferation and apoptosis of KGN cells. We hope that this work provides some original and valuable information for the research of circRNAs in PCOS, not only to better understand the pathogenesis but also to help provide new clues for seeking for the future therapeutic target of PCOS.

Circular RNA circPITX1 knockdown inhibits glycolysis to enhance radiosensitivity of glioma cells by miR-329-3p/NEK2 axis

Background

Numerous circular RNAs (circRNAs) have been recognized as vital modulators of human malignancies, including glioma. Whereas, the functional role of circRNA Pituitary Homeo Box 1 (circPITX1) in the radioresistance of glioma cells remains largely uncertain.

Methods

Quantitative real-time PCR (qRT-PCR) or western blot analysis was employed to examine the expression of circPITX1, microRNA (miR)-329-3p and NIMA-related kinase 2 (NEK2). 3-(4, 5-dimethylthiazol-2-y1)-2, 5-diphenyl tetrazolium bromide (MTT) assay was used to determine cell viability. Glycolysis was assessed by commercial kits and western blot analysis. Colony formation assay was conducted to analyze cell survival and clonogenicity capacity. The relationship among circPITX1, miR-329-3p and NEK2 was confirmed via dual-luciferase reporter assay. The in vivo function of circPITX1 was evaluated by tumor xenograft assay.

Results

Expression of circPITX1 and NEK2 was up-regulated in glioma tissues and cells, while miR-329-3p exhibited reverse trend. CircPITX1 knockdown repressed viability, glycolysis and colony formation, but promoted radiosensitivity of glioma cells, as well as inhibited tumor growth in vivo. MiR-329-3p was a target miRNA of circPITX1 and miR-329-3p deficiency reversed knockdown of circPITX1-mediated glycolysis inhibition and radioresistance reduction. MiR-329-3p exerted inhibitory effects on glycolysis and radioresistance of glioma cells by targeting NEK2. CircPITX1 facilitated NEK2 expression by sponging miR-329-3p. Glycolytic inhibitor 2-deoxy-d-glucose (2-DG) disposition weakened the promoted impact on glycolysis caused by circPITX1.

Conclusion

CircPITX1 knockdown reduced glycolysis to contribute to radiosensitivity in glioma through miR-329-3p/NEK2 axis, providing a possible mechanism of circPITX1 in the development of glioma.