Circular RNA circ_0079593 indicates a poor prognosis and facilitates cell growth and invasion by sponging miR-182 and miR-433 in glioma

Glioma is one of the major global health problems, including in China. Circular RNAs (circRNAs) have been increasingly identified and characterized in almost every aspect of biology, especially in cancer biology. This research desires to explore the functions and mechanism of a novel circRNA, circ_0079593, on regulating glioma progression. Quantitative real-time polymerase chain reaction (qRT-PCR) was carried out to measure the relative expression of circ_0079593, which was upregulated in matched cancerous tissues from 60 patients and four cell lines of glioma. A higher level of circ_0079593 in glioma specimens was linked to larger tumor size, higher WHO grade, and worse survival rate for patients with glioma. Moreover, circ_0079593 can be deemed as an independent prognostic predictor for glioma patients analyzed by multivariate method. Cell counting kit-8, flow cytometric, wound healing, and transwell experiments were used to evaluate cell growth, apoptosis, migration, and invasion influenced by circ_0079593 knockdown/overexpression. Exogenous downregulation of circ_0079593 expression significantly suppressed glioma cell proliferation by increasing cell apoptosis in vitro, and retarded the migratory and invasive potential. Ectopic expressed circ_0079593 could induce the opposite effects. Mechanistically, bioinformatics analysis, qRT-PCR, and dual-luciferase reporter assays showed that microRNA 182 (miR-182) and miR-433 could be sponged and negatively regulated by circ_0079593. Further, rescue assays demonstrated that the biological functions of circ_0079593 are dependent on its inhibition of miR-182 and miR-433. Collectively, the present work indicates that circ_0079593 may be used as an effective prognostic marker and therapeutic target for glioma.     

Upregulation of circular RNA circ_0000502 predicts unfavorable prognosis in osteosarcoma and facilitates cell progression via sponging miR-1238

Growing evidence suggests that circular RNAs (circRNAs) play a significant role in regulating cancer initiation and metastasis. Osteosarcoma (OS) is a sophisticated disease with various genes activated or silenced. In this study, we defined a novel cancer-related circRNA, circ_0000502 in OS progression. qRT-PCR was conducted to detect its expression level in OS tissue samples and cell lines. In addition, the clinical significance of circ_0000502 was investigated. Afterwards, gain-of-function and loss-of-function in vitro assays were performed to detect the cell growth, apoptosis, migration, and invasion altered by circ_0000502 by CCK-8, clone-forming, flow cytometry, and transwell experiments. Xenograft study was performed to validate the in vitro data. The luciferase reporter assay was used to explore the mechanism of circ_0000502. Circ_0000502 was identified upregulated in both OS tissue specimens and cells. In addition, its expression predicts clinical severity and unfavorable prognosis in the 63 recruited patients with OS. Circ_0000502 facilitated cell proliferation, migration, and invasion in OS cells and inhibited cell apoptosis. The animal study further confirmed the in vitro results. For mechanism exploration, circ_0000502 could directly sponge microRNA (miR)-1238, and the oncogenic functions of circ_0000502 is partially dependent on its regulation of miR-1238 proved by rescue assays. In summary, this study might help to develop rational predictive and therapeutic target for patients with OS.     

Circular RNA circ_001350 regulates glioma cell proliferation,apoptosis, and metastatic properties by acting as a miRNA sponge

Glioma is an aggressive malignancy with increasing incidence and threatens people's health worldwide. Accumulating evidence revealed that circular RNAs (circRNAs) play important functions in cancers. A previous study demonstrated that circ_001350 was elevated in glioma tissue samples than nontumorous tissue specimens screened by high-throughput microarray. The level of circ_001350 in glioma tissue specimens and cell lines was detected by quantitative real-time polymerase chain reaction. The Fisher exact test was carried out to estimate the correlation of circ_001350 level with clinical characteristics. Cell proliferation, apoptosis, and motility abilities were detected using cell counting kit-8, clonogenic, flow cytometry, and transwell experiments, respectively. The potential target of circ_001350 was identified by the luciferase assay. circ_001350 level was significantly enhanced in glioma tissue specimens and cells. Further, elevated expression of circ_001350 was closely linked to patients' clinical severity. Knockdown of circ_001350 could inhibit cell proliferation and metastatic properties and increase apoptotic cells. circ_001350 could directly bind to miR-1236 and regulate its expression to exert oncogenic functions. Collectively, circ_001350 directly sponges miR-1236, thus contributing to malignant progression of glioma.     

Upregulated circular RNA circ_0007534 indicates an unfavorable prognosis in pancreatic ductal adenocarcinoma and regulates cell proliferation,apoptosis, and invasion by sponging miR-625 and miR-892b

Circular RNAs (circRNAs) have been regarded as critical regulators of human diseases and biological markers in some types of malignancies, including pancreatic ductal adenocarcinoma (PDAC). Recently, circ_0007534 has been identified as a novel cancer-related circRNA. Nevertheless, its clinical relevance, functional roles, and mechanism have not been studied in PDAC. In the current study, real-time quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of circ_0007534 in 60-paired PDAC tissue samples and different cell lines. Loss-of-function and gain-of-function assays were performed to detect cell proliferation, apoptosis, and metastatic properties affected by circ_0007534. An animal study was also carried out. The luciferase reporter assay was performed to uncover the underlying mechanism of circ_0007534. As a result, circ_0007534 was overexpressed not only in PDAC tissues but also in a panel of PDAC cell lines, and this overexpression is closely associated with advanced tumor stage and positive lymph node invasion. In addition, circ_0007534 may be regarded as an independent prognostic factor for patients with PDAC. For the part of functional assays, circ_0007534 significantly increased cell proliferation, migratory, and invasive potential of PDAC cells. Circ_0007534 could inhibit cell apoptosis partly via a Bcl-2/caspase-3 pathway. The xenograft study further confirmed the cell growth promoting the role of circ_0007534. Mechanistically, miR-625 and miR-892b were sponged by circ_0007534. The oncogenic functions of circ_0007534 is partly dependent on its regulation of miR-625 and miR-892b. In conclusion, our study illuminates a novel circRNA that confers an oncogenic function in PDAC.     

Overexpression of circ_0005198 sponges miR-1294 to regulate cell proliferation,apoptosis, migration,and invasion in glioma

Glioma (GM) is an aggressive malignancy with high mortality rate across the world. Mounting studies demonstrates that abnormally expressed circular RNAs (circRNAs) act as important roles in tumor progression. In the current work, a novel circRNA, circ_0005198, was explored. Circ_0005198 level in GM tissue samples and cells was detected. The clinical implication of circ_0005198 was analyzed by Fisher's test and Kaplan-Meier analysis. In vitro experiments were carried out to elucidate the influence of circ_0005198 on GM cell proliferation, apoptosis, and metastatic properties. Luciferase reporter and rescue experiments were conducted to clear the mechanism of circ_0005198. The expression of circ_0005198 was enhanced in GM tumors and cells. Its expression in tumor specimens was related to clinical severity and poor prognosis. Functionally, circ_0005198 could remarkably boost cell growth, clone-forming ability, and metastatic properties and attenuate cell apoptosis in GM cells. What's more, circ_0005198 could directly sponge miR-1294 to exert oncogenic functions. In summary, this study might provide an effective therapeutic target for GM.     

Circular RNA circ_0103552 forecasts dismal prognosis and promotes breast cancer cell proliferation and invasion by sponging miR-1236

Breast cancer (BC) is a fatal malignancy, which has a high incidence and mortality across the world. Circular RNAs (circRNAs) have crucial roles in tumor initiation and progression. In this project, a newly found circRNA, circ_0103552 was explored. Quantitative real-time polymerase chain reaction was applied to measure its expression in the patients' tissue specimens and cells. In addition, Fisher's exact test, Kaplan-Meier curves and Cox regression model were conducted to discover the clinical significance of circ_0103552. Cell viability, clone-forming ability, apoptosis, and metastatic properties of BC cells were evaluated by gain/loss-of-function assays. Dual luciferase reporter assay was applied to illuminate its mechanisms. As data indicated, circ_0103552 was significantly elevated in BC tissue samples and cells. In addition, its expression correlates with clinical severity and dismal prognosis. Furthermore, circ_0103552 could facilitate cell growth, clone-forming ability, migration and invasion, and decrease apoptotic cells. For the mechanism exploration, circ_0103552 could directly sponge miR-1236 to execute oncogenic activities in BC cells. In summary, this study provides a novel circRNA in tumorigeneis and progression of BC and may help to develop effective therapeutic target for this devastating disease.     

Circular RNA circ_0034642 elevates BATF3 expression and promotes cell proliferation and invasion through miR-1205 in glioma

Growing evidence indicates that circular RNA (circRNA) plays an important role in the regulation of tumor biological behaviors. In this study, we aimed to explore the role of a novel circRNA, circ_0034642, in glioma. qRT-PCR was conducted to evaluate the levels of circ_0034642 in glioma tissues and cells. In addition, the clinical severity and prognostic role of circ_0034642 were illustrated. Functionally, loss and gain-of function assays were performed by CCK-8, colony-forming, flow cytometric and transwell experiments in glioma cells. Moreover, luciferase reporter assay was used to detect the mechanism of circ_0034642. Circ_0034642 was upregulated in glioma tissues and cell lines. Overexpressed circ_0034642 was correlated with adverse phenotypes in the patients with glioma. In addition, circ_0034642 could be regarded as a prognostic predictor for glioma patients. Moreover, circ_0034642 could promote cell proliferation, migratory and invasive capacities and inhibit cell apoptosis. For the mechanism investigation, circ_0034642 was proved to be a sponge of miR-1205, and miR-1205 could regulate BATF3 expression via targeting 3′UTR of BATF3. Rescue assays also illustrated that the oncogenic function of circ_0034642 is partly attributed to its modulation on miR-1205/BATF3 axis. Collectively, circ_0034642/miR-1205/BATF3 pathway may play an important role in glioma.     

Retracted: Elevation of circular RNA circ-POSTN facilitates cell growth and invasion by sponging miR-1205 in glioma

Glioma is the most common type of primary intracranial tumor. Dysregulation of circular RNAs (circRNAs) plays a critical role in multiple solid tumors. However, the expression profiles of circRNAs and their functions in glioma have been rarely studied. The current work aims to investigate the clinical significance of a novel circRNA, circ-POSTN, in glioma and explore its biological functions and mechanisms in the progression of glioma. We found that circ-POSTN was highly expressed in glioma tissue samples and cells. High circ-POSTN expression was significantly linked to larger tumor size, higher World Health Organization grades, and shorter overall survival. Furthermore, silencing of circ-POSTN in glioma cells could decrease cell growth, migratory and invasive potential, and induce cell apoptosis in LN229 cells. On the contrary, ectopically expressed circ-POSTN induced the opposite effects in the U251 cell line. By bioinformatic prediction and luciferase reporter assay, we identified that miR-1205 could be sponged by circ-POSTN. Further rescue assays demonstrated that the oncogenic functions of circ-POSTN are partly attributed to its regulation of miR-1205 in glioma cells. Taken together, our data suggest that circ-POSTN plays an oncogenic role in glioma progression and may serve as a novel therapeutic target in this deadly disease.     

Circular RNA circ_0011269 sponges miR-122 to regulate RUNX2 expression and promotes osteoporosis progression

Circular RNAs (circRNAs) are a novel class of noncoding RNAs that are widely expressed in human disease. However, circRNAs expression profile and potential mechanism in osteoporosis pathogenesis remain to be further studied. In the present study, a total of 69 circRNAs were identified to be abnormally expressed in osteoporosis patient samples by microarray and bioinformatics analyses. We found that circ_0011269 was notably downregulated in osteoporosis (fold change, 3.94). By means of miRanda algorithm, we constructed the interaction network of circ_0011269-miRNAs in osteoporosis based on target binding and miR-122 was enrolled in the network. Dual-luciferase reporter assay verified the target relationship of miR-122 and circ_0011269/RUNX2. The expression of circ_0011269 and RUNX2 were gradually increased during osteogenic differentiation while miR-122 exhibited a decreased expression. Moreover, overexpression of circ_0011269 could promote RUNX2 expression and inhibit osteoporosis. In summary, this study found that circ_0011269 sponges miR-122 to regulate RUNX2 expression and promotes osteoporosis progression.     

Elevated expression of circular RNA circ_0008450 predicts dismal prognosis in hepatocellular carcinoma and regulates cell proliferation,apoptosis, and invasion via sponging miR-548p

Hepatocellular carcinoma (HCC) is one of the most frequent malignancies and a main cause of global cancer mortality. In the past decade, circular RNAs (circRNAs) have been proved to play key roles in various cancers. Previously, circ_0008450 was identified upregulated in HCC tissues by high-throughput circRNA sequencing. In this study, quantitative real-time polymerase chain reaction was used to evaluate the expression level of circ_0008450 in human HCC tumor and corresponding nontumor tissue samples, and the association between circ_0008450 expression and clinicopathologic features of patients with HCC was also analyzed. After that, the functions of circ_0008450 in biological behaviors of HCC cells were determined by cell counting kit-8, colony formation, flow cytometry, and the transwell assays. The mechanism of circ_0008450 was explored by the bioinformatic analysis and dual-luciferase reporter assay. The expression of circ_0008450 is upregulated in HCC tissue specimens and cell lines. Patients with a high circ_0008450 expression usually bear a lower 5-year survival rate. Silencing of circ_0008450 in Huh-7 cells inhibited cell viability, migration, and invasion, whereas cell apoptosis was increased. Conversely, its overexpression in HepG2 cells leads to absolutely inverse results. In addition, circ_0008450 was proved to be a sponge of miR-548p. The oncogenic role of circ_0008450 was partially attributed to its suppression on miR-548p. This study implies a new target for the treatment of HCC.     

Circular RNA hsa_circ_0076248 promotes oncogenesis of glioma by sponging miR-181a to modulate SIRT1 expression

Glioma is one of the most common primary malignancies of the central nervous system, which has aggressive clinical behavior and a poorer prognosis. MicroRNAs (miRs) are a class of small noncoding RNAs that function as mediators of gene expression, which can be sponged by circRNA provided with a closed circular structure. Dysregulations of circular RNAs (circRNAs) and miRs have been implicated in the development and progression of glioma. In the current study, we investigated the role of circular RNA hsa_circ_0076248 in mediating the oncogenesis of glioma by sponging miR-181a to modulate silent information regulator 1 (SIRT1) expression in vitro and in vivo. The quantitative real-time polymerase chain reaction results showed that the expression of miR-181a was significantly decreased in glioma tissues and cell lines compared with normal brain tissues and normal gliocyte, respectively, and the expression of hsa_circ_0076248 and SIRT1 demonstrated the opposite. Bioinformatics analysis identified hsa_circ_0076248 could sponge miR-181a, and miR-181a could target the mRNA of SIRT1. Our results verified that downregulating hsa_circ_0076248 or upregulating miR-181a could depress the proliferation and invasion of glioma in vitro and in vivo. The experiment also showed that downregulating hsa_circ_0076248 or upregulating miR-181a could remarkably promote the temozolomide chemotherapy sensitivity. Furthermore, Western blot analysis testified that downregulating hsa_circ_0076248 or upregulating miR-181a could promote the expression of p53 and SIRT1. In summary, our study sheds light on the regulatory mechanism of hsa_circ_0076248 in glioma growth and invasion via sponging miR-181a, which downregulates the SIRT1 expression and also suggests that hsa_circ_0076248, miR-181a, and SIRT1 may serve as potential therapeutic targets for glioma.     

Circular RNA ciRS-7 inhibits autophagy of ESCC cells by functioning as miR-1299 sponge to target EGFR signaling

Autophagy is a kind of intracellular degradation pathway which could be regulated by many noncoding RNAs. ciRS-7, also called CDR1as, is a circular RNA that is relatively well studied at present. In our recent study, we have found that the expression of ciRS-7 is abnormally increased in the esophageal squamous cell carcinoma (ESCC), and may function as an oncogene to accelerate ESCC progression through sponging miR-876-5p. Meanwhile, another study showed that ciRS-7 is highly expressed in the triple-negative breast cancer (TNBC) and may function as a competing endogenous RNA of miR-1299 to maintain the high migration and invasive capacity of TNBC cells. Of interest, in the present work, we observed that ciRS-7 could inhibit starvation or rapamycin-induced autophagy of ESCC cells and miR-1299 promotes starvation or rapamycin-induced autophagy of ESCC cells. Mechanically, miR-1299 could directly bind to the 3′-untranslated region of epidermal growth factor receptor (EGFR) and then affects its downstream Akt-mTOR pathway in ESCC cells. Consistent with our past findings, ciRS-7 could also sponge miR-1299 in ESCC cells. Taken together, this study has shed light on that circular RNA ciRS-7 inhibits autophagy of ESCC cells by functioning as miR-1299 sponge to target EGFR signaling.