Circle RNA hsa_circRNA_100290 serves as a ceRNA for miR-378a to regulate oral squamous cell carcinoma cells growth via Glucose transporter-1 (GLUT1) and glycolysis

Circ_03955 promotes pancreatic cancer tumorigenesis and Warburg effect by targeting the miR-3662/HIF-1α axis

OBJECTIVES

Former studies found that circRNAs play an important part in the occurrence of a variety of malignant biological characteristics that are critical for cancer progression. It has been shown that circ_03955 is highly expressed and implicated with quantities of biological processes in solid tumor. However, whether circ_03955 regulates the tumorigenesis and Warburg effect of pancreatic cancer (PC) remains largely unknown.

MATERIALS AND METHODS

The level of circ_03955 in PC tissues and cell lines was determined by real-time qPCR (RT-qPCR). Loss-of-function and gain-of-function assays were employed to investigate the biological role of circ_03955 in cell proliferation, apoptosis, and glycolysis. RT-qPCR, western blotting, bioinformatics analysis, luciferase reporter assay, and in vivo tumorigenicity assay were employed to determine the underlying mechanisms.

RESULTS

In this study, it was investigated that circ_03955 was up-regulated in PC clinical samples as well as PC cell lines and associated with poor clinical outcomes of PC patients. Functional assays revealed that circ_03955 exerts a certain stimulative effect on the growth of PC cells in vitro and in vivo. Circ_03955 also inhibited apoptosis and promotes Warburg effect in PC cells. Mechanistically, bioinformatics analysis indicated that circ_03955 acts as a sponge for microRNA (miR)-3662, and hypoxia-inducible factor 1ɑ (HIF-1ɑ) was one of the transcriptional targets of miR-3662. Importantly, genetic promoting of HIF-1ɑ or downregulation of miR-3662 largely compromised circ_03955 depletion mediated tumor-inhibiting effects.

CONCLUSIONS

Taken together, circ_03955 functions as a tumor promoter through miR-3662/HIF-1α axis, which might provide a novel sight for PC treatment.

Tip of the Iceberg: Roles of CircRNAs in Cancer Glycolysis

Warburg effect reflects that tumor cells tend to generate energy by aerobic glycolysis rather than oxidative phosphorylation (OXPHOS), thus promoting the development of malignant tumors. As a kind of non-coding RNA, circular RNA (circRNA) is characterized by a closed ring structure and emerges as a regulator of cancer metabolism. Mounting studies revealed that circRNA can regulate the cancer metabolism process through affecting the expression of glycolysis relevant enzymes, transcription factors (TFs), and signaling pathways. In this review, we comprehensively analyzed and concluded the mechanism of circRNA regulating glycolysis, hoping to deepen the cognition of the cancer metabolic regulatory network and to reap huge fruits in targeted cancer treatment.

Glycolysis reprogramming in cancer-associated fibroblasts promotes the growth of oral cancer through the lncRNA H19/miR-675-5p/PFKFB3 signaling pathway

As an important component of the tumor microenvironment, cancer-associated fibroblasts (CAFs) secrete energy metabolites to supply energy for tumor progression. Abnormal regulation of long noncoding RNAs (lncRNAs) is thought to contribute to glucose metabolism, but the role of lncRNAs in glycolysis in oral CAFs has not been systematically examined. In the present study, by using RNA sequencing and bioinformatics analysis, we analyzed the lncRNA/mRNA profiles of normal fibroblasts (NFs) derived from normal tissues and CAFs derived from patients with oral squamous cell carcinoma (OSCC). LncRNA H19 was identified as a key lncRNA in oral CAFs and was synchronously upregulated in both oral cancer cell lines and CAFs. Using small interfering RNA (siRNA) strategies, we determined that lncRNA H19 knockdown affected proliferation, migration, and glycolysis in oral CAFs. We found that knockdown of lncRNA H19 by siRNA suppressed the MAPK signaling pathway, 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) and miR-675-5p. Furthermore, the lncRNA H19/miR-675-5p/PFKFB3 axis was involved in promoting the glycolysis pathway in oral CAFs, as demonstrated by a luciferase reporter system assay and treatment with a miRNA-specific inhibitor. Our study presents a new way to understand glucose metabolism in oral CAFs, theoretically providing a novel biomarker for OSCC molecular diagnosis and a new target for antitumor therapy.

Circ-KIAA0907 inhibits the progression of oral squamous cell carcinoma by regulating the miR-96-5p/UNC13C axis

Background

Circular RNA (circRNA) plays an important role in regulating cell biological function and has been shown to be involved in cancer progression, including oral squamous cell carcinoma (OSCC). Circ-KIAA0907 has been found to play an anti-cancer role in OSCC, so it is worth exploring more functions and new mechanisms of circ-KIAA0907 in OSCC progression.

Methods

Quantitative real-time PCR (qRT-PCR) was used to detect the expression of circ-KIAA0907, microRNA (miR)-96-5p, and unc-13 homolog C (UNC13C). Transwell assay, flow cytometry, and colony formation assay were employed to measure the migration, invasion, apoptosis, and radiosensitivity of cells. Besides, glucose uptake, lactate production, and extracellular acidification rate (ECAR) were determined to evaluate the glycolysis ability of cells. Dual-luciferase reporter assay and RIP assay were performed to confirm the interactions among circ-KIAA0907, miR-96-5p, and UNC13C. And RNA pull-down assay was used to verify the binding degree of miR-96-5p to its targets. Moreover, UNC13C protein level was examined using western blot (WB) analysis. OSCC xenograft models were constructed to perform in vivo experiments.

Results

Circ-KIAA0907 was a stability circRNA with lowly expression in OSCC. Overexpressed circ-KIAA0907 could inhibit migration, invasion, and glycolysis, while promoting apoptosis and radiosensitivity in OSCC cells. In the terms of mechanism, circ-KIAA0907 could sponge miR-96-5p to regulate UNC13C expression. MiR-96-5p overexpression could reverse the inhibitory effect of circ-KIAA0907 on OSCC progression, and UNC13C knockdown also could overturn the suppressive effect of miR-96-5p inhibitor on OSCC progression. Animal experiments revealed that circ-KIAA0907 could reduce the tumor growth of OSCC by regulating the miR-96-5p/UNC13C axis.

Conclusion

Our study suggests that circ-KIAA0907 restrains OSCC progression via the miR-96-5p/UNC13C axis, indicating that it may be a potential target for OSCC treatment.

Circ_0056285 Regulates Proliferation, Apoptosis and Glycolysis of Osteosarcoma Cells via miR-1244/TRIM44 Axis

Background

Osteosarcoma (OS) is a common malignant bone cancer that occurs in adolescents and children. Circular RNAs (circRNAs) are important regulators of tumorigenesis and development. This study aimed to explore the role and molecular basis of circ_0056285 in OS.

Methods

The levels of circ_0056285, miR-1244 and tripartite motif containing 44 (TRIM44) were determined by quantitative real-time polymerase chain reaction or Western blot assay. Cell proliferation was evaluated by Cell Counting Kit-8 (CCK-8) assay and colony formation assay. Cell apoptosis was assessed by flow cytometry and caspase 3and caspase 9 activity assay kits. Glucose uptake, lactate product and ATP level were examined using commercial kits. Hexokinase II (HK2) and lactate dehydrogenase A (LDHA) levels were measured by Western blot assay. The interaction among circ_0056285, miR-1244 and TRIM44 was confirmed by dual-luciferase reporter assay, RNA immunoprecipitation assay or RNA pull-down assay. Xenograft experiment was conducted to explore tumor growth in vivo. Exosomes were identified by transmission electron microscope (TEM), nanoparticle tracking analysis (NTA) and Western blot. The diagnostic value of exosomal circ_0056285 was evaluated by receiver operating characteristic (ROC) curve.

Results

Circ_0056285 and TRIM44 were up-regulated, and miR-1244 was down-regulated in OS tissues and cells. Circ_0056285 silencing inhibited proliferation and glycolysis and promoted apoptosis in OS cells. Also, circ_0056285 knockdown hindered proliferation and accelerated apoptosis in OS cells by regulating miR-1244/TRIM44 axis. Circ_0056285 depletion impeded tumor growth in vivo. Furthermore, ROC curve showed that circ_0056285 might be a diagnostic biomarker in OS.

Conclusion

Circ_0056285 facilitated OS progression by sponging miR-1244 and increasing TRIM44 expression, providing a promising therapeutic target for OS.

CircRNA_104565 Promoted Cell Proliferation in Papillary Thyroid Carcinoma by Sponging miR-134

BACKGROUND

Thyroid cancer is one of the most common cancers with rising incidence worldwide, and papillary thyroid carcinoma (PTC) accounts for 80-85% of thyroid malignancy. Although it has been reported that many genes relate to the carcinogenesis of PTC, the molecular mechanisms remain mostly unclear.

METHODS

QRT-PCR assay was performed to detect circRNA_104565, miR-134 and ELF2 expression. CCK8 assay was exercised to examine cell proliferation. Western blot was used to detect ELF2 expression.

RESULTS

We found that circRNA_104565 was highly expressed in PTC tissue and cell and promoted cell proliferation in vitro and in vivo. In addition, circRNA_104565 promoted cell proliferation in PTC by regulating the miR-134/ELF2 axis.

CONCLUSION

Hence, revealing the function of circRNA_104565 in PTC is important for understanding the molecular mechanism of carcinogenesis and providing new biomarkers or therapeutic targets for PTC.

Circular RNAs as biomarkers and therapeutic targets in cancer

Circular RNAs (circRNAs) are a class of single-stranded closed non-coding RNA molecules (ncRNAs), which are formed as a result of reverse splicing of mRNAs. Despite their relative abundance, an interest in understanding their regulatory importance is rather recent. High stability, abundance and evolutionary conservation among species underline some of their important traits. CircRNAs perform a variety of cellular functions ranging from miRNA and proteins sponges to transcriptional modulation and splicing. Additionally, most circRNAs are expressed aberrantly in pathological conditions suggesting their possible exploitation as diagnostic biomarkers. Their covalent closed cyclic structure resulting in resistance to RNases further makes them suitable as cancer biomarkers. Studies involving human tumors have verified differences in the expression profiles of circRNAs, indicating a regulatory role in cancer pathogenesis and metastasis. As endogenous competitive RNA, circRNAs can regulate tumor proliferation and invasion. Further, some circRNAs located in the nucleus can regulate transcription of genes by binding to RNA polymerase II. In this review, we elaborate the characteristics, functions and mechanisms of action of circRNAs in cancer. We also discuss the possibility of using circRNAs as potential therapeutic targets and biomarkers for cancer.

LINC00839 Regulates Proliferation, Migration, Invasion, Apoptosis and Glycolysis in Neuroblastoma Cells Through miR-338-3p/GLUT1 Axis

BACKGROUND

Long noncoding RNAs (lncRNAs) are related to the development and treatment of neuroblastoma. The lncRNA LINC00839 is dysregulated in neuroblastoma, while its function and mechanism in neuroblastoma development remain largely unclear.

METHODS

The tumor and adjacent noncancerous tissues were collected from 48 neuroblastoma patients. LINC00839, glucose transporter 1 (GLUT1) and microRNA-338-3p (miR-338-3p) abundances were examined via quantitative reverse transcription polymerase chain reaction or Western blot. Cell proliferation, apoptosis, migration, invasion and glycolysis were assessed via Cell Counting Kit-8, colony formation, flow cytometry, wound healing, transwell, glucose uptake and lactate production. The target relationship of miR-338-3p and LINC00839 or GLUT1 was tested via dual-luciferase reporter analysis and RNA immunoprecipitation. The function of LINC00839 on neuroblastoma cell growth in vivo was tested via a xenograft model.

RESULTS

LINC00839 and GLUT1 abundances were increased in neuroblastoma tissues and cell lines. The high expression of LINC00839 and GLUT1 indicated the lower overall survival. LINC00839 interference constrained neuroblastoma cell proliferation, migration, invasion and glycolysis, and facilitated apoptosis. GLUT1 overexpression or miR-338-3p knockdown could mitigate the influence of LINC00839 silence on neuroblastoma cell processes. LINC00839 could regulate GLUT1 expression via miR-338-3p. LINC00839 knockdown reduced neuroblastoma cell growth in xenograft model.

CONCLUSION

LINC00839 silence repressed neuroblastoma cell proliferation, migration, invasion and glycolysis and promoted apoptosis via regulating miR-338-3p/GLUT1 axis.

Circular RNA hsa_circ_0008003 facilitates tumorigenesis and development of non-small cell lung carcinoma via modulating miR-488/ZNF281 axis

As one of the most aggressive malignancies, non‐small cell lung carcinoma (NSCLC) has high risks of death. It has been demonstrated that circRNAs accelerate NSCLC progression, but the underlying molecular mechanisms of circRNAs in NSCLC were still obscure. In the first place, the circRNA microarray of NSCLC was investigated in this study, and hsa_circ_0008003 (circ‐0008003) was chosen as the research object. Then, it was unveiled that the expression of circ‐0008003 examined via qRT‐PCR was elevated in tumour tissues relative to the non‐tumour tissues, which was associated with TNM stage and lymphatic metastasis in NSCLC. Additionally, the prognosis of NSCLC patients with high circ‐0008003 level was poor. Besides, circ‐0008003 silencing dampened the invasion and proliferation of NSCLC cells. Next, according to the mechanistic studies, circ‐0008003 functioned as a ceRNA of ZNF281 in NSCLC by acting as the endogenous sponge for miR‐488, which was proved to be a tumour suppressor in NSCLC. Additionally, ZNF281 overexpression and miR‐488 suppression recovered the influences of repressed circ‐0008003 on NSCLC cellular processes. It was validated in this research that circ‐0008003 triggered tumour formation in NSCLC, which was adjusted via miR‐488/ZNF281 axis, casting a novel light on the resultful target for treating NSCLC and predicting the prognosis.

Comprehensive analysis of circular RNA in oral leukoplakia: upregulated circHLA-C as a potential biomarker for diagnosis and prognosis

Background

Emerging evidence indicates that circular RNAs (circRNAs) play an indispensable role in a variety of tumors, yet the function of circRNAs in premalignant lesions is still obscure. Oral leukoplakia (OLK) is one of the most common premalignant lesions of the oral mucosa. Our study aimed to comprehensively investigate whether circRNAs contribute to the occurrence and development of OLK.

Methods

We obtained six pairs of OLK and normal oral mucosal (NOM) tissue samples and subjected them to high-throughput sequencing to detect the expression of circRNA. In total, 26 pairs of NOM and OLK tissues were used for validation. Key circRNAs were selected and further validated by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR), ribonuclease (RNase) R digestion, and Sanger sequencing. Visualization analysis of circular human leukocyte antigen-C (circHLA-C) was performed in the UCSC Genome Browser (genome.ucsc.edu). Functional analysis of differentially expressed (DE) circRNAs were processed by Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Furthermore, TargetScan (www.targetscan.org) was applied to predict targeted micro RNAs (miRNAs) and messenger RNAs (mRNAs) of circRNAs and a competing endogenous RNA (ceRNA) network related with identified circRNAs was constructed in Cytoscape (v2.8.0).

Results

Profile data showed that 366 circRNAs were significantly altered in OLK tissues, including 65 upregulated and 301 downregulated circRNA transcripts. Compared with sequencing results, seven selected circRNAs expressed the same changing tendency. The amplest upregulated circRNA in our sequencing data, circHLA-C, was confirmed through back-splice junction sequences by Sanger sequencing after RNase R digestion. Correlation analysis demonstrated that circHLA-C correlated positively with the degree of dysplasia. Furthermore, receiver operating characteristic (ROC) curve analysis indicated that circHLA-C had potential diagnostic value with excellent accuracy and specificity.

Conclusions

According to the literature, we were the first to uncover the expression profiles of circRNAs in OLK. Our research performed a comprehensive bioinformatics analysis of DE circRNAs in OLK and identified circHLA-C as a promising diagnostic biomarker with potential as a therapeutic genetic target for OLK.

CircRNA_ACAP2 Suppresses EMT in Head and Neck Squamous Cell Carcinoma by Targeting the miR-21-5p/STAT3 Signaling Axis

Circular RNAs (circRNAs) contain microRNA (miRNA)-specific binding sites and can function as miRNA sponges to regulate gene expression by suppressing the inhibitory effect of miRNAs on their target genes. MiR-21-5p has been reported to be involved in the development of head and neck squamous cell carcinoma (HNSCC) and plays an important role in the activation of epithelial-mesenchymal transition (EMT). However, the upstream regulatory mechanism and downstream targets of miR-21-5p in tumor cells remain unknown. CircRNA_ACAP2 inhibits the function of miR-21-5p by binding to its specific binding sites in HNSCC cells. Overexpression of CircRNA_ACAP2 inhibits the proliferation and migration of HNSCC cells, while downregulation of CircRNA_ACAP2 has the opposite effect. STAT3 is a direct target gene of miR-21-5p and a transcription factor of ZEB1. We demonstrate that CircRNA_ACAP2 functions as a tumor suppressor gene in HNSCC and that its function is regulated via the miR-21-5p/STAT3 signaling axis.

Clinical Significance of Has_circ_0060937 in Bone Metastasis of NSCLC

Background

Bone metastasis can induce multiple types of bone diseases which reduce the non-small-cell lung cancer (NSCLC) patient's quality-of-life. Due to the difficulty of finding bone metastases and lack of effective early diagnosis, it is easy to miss the best treatment. Therefore, the study of serum tumor biomarkers is of great significance in the diagnosis of NSCLC bone metastasis.

Methods

The qRT-PCR assay was performed to assess has_circ_0060937 expression in 100 NSCLC patients. Furthermore, the small interfering RNAs si-has_circ_0060937 or si-NC were transfected into NSCLC bone metastasis cells. CCK8 assay was exercised to detect cell proliferation, and cell invasion assays were used to detect cell invasion in NSCLC bone metastasis cells.

Results

In this study, we firstly found that the expression of has_circ_0060937 in boneless metastasis NSCLC tissues and bone metastasis NSCLC tissues was significantly increased compared to normal tissues, and the expression of has_circ_0060937 was highest in bone metastasis. Expression of serum has_circ_0060937 in bone metastasis group from Grade I to Grade III NSCLC was drastically higher than boneless metastasis group or healthy group. In the Grade I to Grade III bone metastasis group, the expression of serum has_circ_0060937 gradually boosted with the increase of bone metastasis grades. Additionally, knockdown of has_circ_0060937 inhibited cell proliferation and cell invasion in NSCLC bone metastasis cell line.

Conclusion

The results suggestthat has_circ_0060937 is closely associated with bone metastasis in NSCLC, and the circRNAs we inspected may be a potential biomarker of bone metastasis in NSCLC.

Long non-coding RNA MIAT regulates blood tumor barrier permeability by functioning as a competing endogenous RNA

Blood-tumor barrier (BTB) presents a major obstacle to brain drug delivery. Therefore, it is urgent to enhance BTB permeability for the treatment of glioma. In this study, we demonstrated that MIAT, ZAK, and phosphorylated NFκB-p65 (p-NFκB-p65) were upregulated, while miR-140-3p was downregulated in glioma-exposed endothelial cells (GECs) of BTB compared with those in endothelial cells cocultured with astrocytes (ECs) of blood-brain barrier (BBB). MIAT inhibited miR-140-3p expression, increased the expression of ZAK, enhanced the ratio of p-NFκB-p65:NFκB-p65, and promoted the endothelial leakage of BTB. Our current study revealed that miR-140-3p was complementary to the ZAK 3'untranslated regions (3'-UTR), and luciferase activity of ZAK was inhibited by miR-140-3p in 293T cells. MiR-140-3p silencing resulted in an increase in BTB permeability by targeting ZAK, while overexpression of miR-140-3p had the opposite results in GECs of BTB. Overexpression of ZAK induced an increase in BTB permeability, and this effect was related to ZAK's ability to mediate phosphorylation of NFκB-p65. Conversely, ZAK silencing get opposite results in GECs of BTB. As a molecular sponge of miR-140-3p, MIAT attenuated its negative regulation of the target gene ZAK by adsorbing miR-140-3p. P-NFκB-p65 as a transcription factor negatively regulated the expression of TJ-associated proteins by means of chip assay and luciferase assay. Single or combined application of MIAT and miR-140-3p effectively promoted antitumor drug doxorubicin (Dox) across BTB to induce apoptosis of glioma cells. In summary, MIAT functioned as a miR-140-3p sponge to regulate the expression of its target gene ZAK, which contribution to phosphorylation of NFκB-p65 was associated with an increase in BTB permeability by down-regulating the expression of TJ associated proteins, thereby promoting Dox delivery across BTB. These results might provide a novel strategy and target for chemotherapy of glioma.

The functions and clinical significance of circRNAs in hematological malignancies

With covalently closed circular structures, circular RNAs (circRNAs) were once misinterpreted as by-products of mRNA splicing. Being abundant, stable, highly conserved, and tissue-specific, circRNAs are recently identified as a type of regulatory RNAs. CircRNAs bind to certain miRNAs or proteins to participate in gene transcription and translation. Emerging evidence has indicated that the dysregulation of circRNAs is closely linked to the tumorigenesis and treatment response of hematological malignancies. CircRNAs play critical roles in various biological processes, including tumorigenesis, drug resistance, tumor metabolism, autophagy, pyroptosis, and ferroptosis. The N6-methyladenosine modification of circRNAs and discovery of fusion-circRNAs provide novel insights into the functions of circRNAs. Targeting circRNAs in hematological malignancies will be an attractive treatment strategy. In this review, we systematically summarize recent advances toward the novel functions and molecular mechanisms of circRNAs in hematological malignancies, and highlight the potential clinical applications of circRNAs as novel biomarkers and therapeutic targets for future exploration.

Comprehensive Assessment of Plasma Circ_0004771 as a Novel Diagnostic and Dynamic Monitoring Biomarker in Gastric Cancer

Purpose

Due to the lack of specific and sensitive detection indicators, most patients with GC are already in the advanced stage at the time of diagnosis. Therefore, it is urgent to search for effective diagnostic biomarkers that can be applied in clinic.

Materials and Methods

We screened out circ_0004771 through circRNA sequencing. Exonuclease digestion assay, agarose gel electrophoresis (AGE) and Sanger sequencing verified the potential of circ_0004771 being a biomarker. Additionally, we established quantitative real-time fluorescent polymerase chain reaction (qRT-PCR) to detect the expression level of circ_0004771 and evaluated the methodology. What's more, we collected plasma samples from 120 GC patients, 40 superficial gastritis patients, 20 postoperative GC patients, 20 postoperative recurrence patients and 120 healthy donors. We constructed the receiver operating characteristic curve (ROC) to appraise its diagnostic efficacy.

Results

The expression level of circ_0004771 is up-regulated in GC tissues, which is consistent with circRNA sequencing result (P=0.0001). Circ_0004771 can serve as a promising biomarker because of its stable structure and longer half-life. Plasma circ_0004771 expression is markedly richer in GC patients than that in normal people (P<0.0001), and the area under the ROC (AUC) is 0.831 (95% CI: 0.779–0.883). The diagnostic efficacy of circ_0004771 is higher than that of CEA (AUC=0.747, 95% CI: 0.686–0.808) and CA199 (AUC=0.508, 95% CI: 0.433–0.583). Higher diagnostic efficacy can be achieved by combination diagnosis for distinguishing GC patients from normal people (AUC=0.864). Besides, the expression level of circ_0004771 can distinguish GC patients from gastritis patients (AUC=0.845, 95% CI: 0.772–0.917). The plasma circ_0004771 expression in GC patients decreased to normal after surgery (P<0.0001). In addition, plasma circ_0004771 expression increased again in patients with postoperative recurrence.

Conclusion

Plasma circ_0004771 is differentially expressed in GC patients, postoperative GC patients and patients with recurrence, suggesting that plasma circ_0004771 can be used as a novel diagnostic and dynamic monitoring biomarker in GC.

Coptisine Blocks Secretion of Exosomal circCCT3 from Cancer-Associated Fibroblasts to Reprogram Glucose Metabolism in Hepatocellular Carcinoma

Coptisine, extracted from rhizoma coptidis, has been shown to inhibit a variety of cancers. However, the underlying mechanism by which coptisine regulates hepatocellular carcinoma (HCC) progression remains unknown. MTT assay, transwell invasion assay, and TUNEL assay were employed to examine cell viability, invasion, and apoptosis. In vivo tumor growth was determined by xenograft experiment. Reverse transcription-quantitative PCR was used to detect circCCT3 and HK2 gene expression. We utilized glucose consumption and lactate production assay to examine glucose metabolism state. Conditioned medium of coptisine-treated cancer-associated fibroblast (CAF) suppressed cell viability and invasion of HepG2 and Huh-7, whereas increased cell apoptosis. Coptisine significantly inhibited tumor growth of HepG2 cells in immunodeficient mice. Mechanistically, coptisine blocked secretion of exosomal circCCT3 from CAF. More notably, circCCT3 was upregulated in clinical HCC tumors. Moreover, circCCT3 was confirmed to affect glucose metabolism of HCC cells. We identified HK2 as a key downstream effector for circCCT3-modulated HCC tumorigenesis. In summary, our research revealed novel molecular mechanism of coptisine-blocked HCC progression, thereby providing solid rationale for using coptisine to treat HCC.

CircRNAs: A New Chapter in Oral Squamous Cell Carcinoma Biology

With the rapid development of bioinformatics and gene sequencing technologies, understanding of circular RNAs (circRNAs) has been extended, and numerous studies have identified the key regulator role of circRNAs in a variety of diseases, especially in cancer. Recently, accumulated studies of oral squamous cell carcinoma (OSCC) have discovered the great potential of circRNAs, which can serve as prognostic or diagnostic biomarkers and affect the development and therapy of OSCC. In this review, we detail the new progress of circRNA research for OSCC in order to provide new strategies for clinical diagnosis and treatment.

Circ-SLC8A1 regulates osteoporosis through blocking the inhibitory effect of miR-516b-5p on AKAP2 expression

BACKGROUND

Osteoporosis is a disease characterized by bone loss, imbalance of bone metabolism and destruction of trabecular microarchitecture. Circular RNAs (circRNAs) have been revealed as important biological regulators in human diseases. The expression characteristics and mechanism of circRNAs in osteoporosis are unclear.

METHODS

The binding sites of miR-516b-5p on circ-SLC8A1 and AKAP2 mRNA were predicted using circAtlas (http://circatlas.biols.ac.cn) and miRDB (http://mirdb.org). Target sites of miR-516b-5p on circ-SLC8A1 and AKAP2 mRNA were confirmed by a dual luciferase assay. The relationship between miR-516b-5p and AKAP2 was determined by a quantitative reverse transcriptase-polymerase chain reaction. Alizarin red S staining and alkaline phosphatase staining were used to observe the level of osteogenic differentiation after transfection.

RESULTS

The first six circRNAs captured from the 30 circRNAs with highest expression in the bone marrow were examined in a mouse model of osteoporosis and the expression of circ-SLC8A1 was found to be significantly reduced in osteoporosis. Circ-SLC8A1 negatively regulated the expression of miR-516b-5p. Overexpression of circ-SLC8A1 blocked the inhibition of AKAP2 by miR-516b-5p.

CONCLUSIONS

Circ-SLC8A1 blocks the inhibitory effect of miR-516b-5p on the downstream target gene AKAP2 and promotes osteoporosis. The findings of the present might help to provide a new strategy for the treatment of osteoporosis.

The Circular RNA-miRNA Axis: A Special RNA Signature Regulatory Transcriptome as a Potential Biomarker for OSCC

Oral squamous cell carcinoma (OSCC) is a highly recurrent form of cancer arising from the oral epithelium, which is the result of mutational change due to etiological factors such as tobacco, smoking, chewing of areca nuts, and alcohol consumption. OSCC occurrence has been observed to be prevalent in different regions of Pacific countries and in most Asian countries. Despite the accessibility of the oral cavity, OSCC is diagnosed at an extremely late stage of pathogenic tumor node metastasis pTNM (III–IV), resulting in a poor prognosis for the individual. Therefore, it is important to make definitive, early, and efficient diagnoses. Owing to the development of omic-natured studies, the presence of proteins, transcribed elements, metabolic products, and even microflora detected in saliva helps us to select biomarkers, which is an especially exciting potential because of the availability and the non-invasive nature of sample collection. Since the discovery of circular RNA (circRNA) by Sanger sequencing, it has been reported to play a pivotal role in several human diseases, including cancer. circRNA functions as a microRNA (miRNA) sponge in the regulation of mRNA expression, forming the circRNA-miRNA regulatory axis. In the case of OSCC, overexpression of different circRNAs exhibits both tumor-progressive and tumor-suppressive effects.

Upregulation of circ_0000199 in circulating exosomes is associated with survival outcome in OSCC

Studies have found that circRNA in exosomes is associated with oral squamous cell carcinoma (OSCC) progression. In this study, we examined the expression of circ_0000199 in circulating exosomes from patients with OSCC and its role in the evaluation of relapse and prognosis. Real‐time quantitative reverse transcription–polymerase chain reaction was performed to assess circ_0000199 expression in circulating exosomes from 108 patients with OSCC and 50 healthy people. Gain- and loss-functional experiments were performed to assess the role of circ_0000199 on cell proliferation and apoptosis in OSCC cells. Our results showed that the high level of circ_0000199 in circulating exosomes was significantly associated with betel quid chewing, tumor size, lymphatic metastasis, and TNM stage in patients with OSCC. In addition, the patients with high exosomal circ_0000199 had higher tumor recurrence rate and higher mortality rate than the patients with low exosomal circ_0000199. Overexpression of circ_0000199 promoted, while knockdown of circ_0000199 inhibited OSCC cell growth. Bioinformatics analysis predicted that circ_0000199 interacted with miR-145-5p and miR-29b-3p simultaneously, which were involved in multiple tumor‐related signaling pathways. In conclusion, upregulation of circ_0000199 in circulating exosomes from patients with OSCC is positively associated with poor survival outcome. Circulating exosomal circ_0000199 can be used as a biomarker and potential therapeutic target for OSCC.

Circular RNA ITCH suppresses proliferation, invasion, and glycolysis of ovarian cancer cells by up-regulating CDH1 via sponging miR-106a

Background

Accumulating data suggested that circular RNAs (circRNAs) played important roles in the development of human cancer. However, the potential mechanism of circRNAs in ovarian cancer remains unclear.

Methods

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to measure the levels of circRNA itchy E3 ubiquitin protein ligase (circ-ITCH), microRNA-106a (miR-106a) and E-cadherin (CDH1). Cell Counting Kit-8 (CCK-8) and Transwell assay were carried out to measure cell proliferation and invasion. Glucose consumption, lactate production, and ATP level were assessed by the glucose, lactate, and ATP assay kits, respectively. Cell apoptosis was detected by Flow cytometry. The binding sites were predicted by StarBase v.2.0 or microT-CDS and verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assays. CDH1 protein level was determined by western blot. The functional role of circ-ITCH was measured by xenograft tumor model in vivo.

Results

Circ-ITCH was down-regulated in ovarian cancer and positively correlated with 5-year overall survival of patients with ovarian cancer. RNase R digestion assay confirmed that circ-ITCH was more stable than its linear mRNA form. Moreover, circ-ITCH was mainly distributed in the cytoplasm of ovarian cancer cells.Functionally, circ-ITCH overexpression hindered proliferation, invasion, glycolysis and promoted apoptosis of ovarian cancer cells. Besides, circ-ITCH overexpression inhibited ovarian cancer cell progression by targeting miR-106a. Additionally, CDH1 was a target of miR-106a, and the protein level of CDH1 was negatively regulated by miR-106a. Similarly, CDH1 knockdown recovered the inhibition effects of miR-106a inhibitor or circ-ITCH overexpression on the progression of ovarian cancer cells. Importantly, circ-ITCH up-regulated the protein level of CDH1 by sponging miR-106a in ovarian cancer cells. Circ-ITCH overexpression suppressed the growth of ovarian cancer cells in vivo.

Conclusion

Circ-ITCH suppressed proliferation, invasion, glycolysis, and promoted apoptosis of ovarian cancer cells by modulating the miR-106a/CDH1 axis.

circ_KIAA1429 accelerates hepatocellular carcinoma advancement through the mechanism of m6A-YTHDF3-Zeb1

AIMS

Hepatocellular carcinoma (HCC), one of the most common cancer, causes the fourth cancer-related deaths around the world. N6-methyladenosine (m⁶A) has been reported to mediate circRNA translation in cancer biology. However, the mechanisms by which m⁶A and circRNA in post-transcriptional in HCC progression remain poorly understood. This study aimed to explore the mechanisms by which m⁶A and circRNA in post-transcriptional in HCC progression.

MAIN METHODS

circ_KIAA1429 (hsa_circ_0084922) expression profiles in matched normal and HCC tissues were detected using microarray analysis. The biological roles of circ_KIAA1429 in progression of HCCC were measured both in vitro and in vivo.

KEY FINDINGS

In this study, we found hsa_circ_0084922, which came from KIAA1429, named circ_KIAA1429, was upregulated in HCC cells and tumor tissues. Overexpression of circ_KIAA1429 can facilitate HCC migration, invasion, and EMT process. However, knockdown of circ_KIAA1429 lead to the opposite results. Furthermore, it was demonstrated that Zeb1 was the downstream target of circ_KIAA1429. Up-regulation of Zeb1 led to HCC cells metastasis induced by circ_KIAA1429. In addition, YTHDF3 enhanced Zeb1 mRNA stability via an m⁶A dependent manner.

SIGNIFICANCE

This study revealed that circ_KIAA1429 could accelerate HCC advancement, maintained the expression of Zeb1 through the mechanism of m⁶A-YTHDF3-Zeb1 in HCC. What's more, it might represent a potential therapeutic target in HCC.

Circ_0000745 Promotes the Progression of Cervical Cancer by Regulating miR-409-3p/ATF1 Axis

Background: Cervical cancer (CC) is a common gynecological malignancy with a high risk of recurrence and death. Circular RNAs play a crucial role in the occurrence and development of tumors. This study aimed to investigate the function and mechanism of circ_0000745 in CC. Methods: The levels of circ_0000745, miR-409-3p, and activating transcription factor 1 (ATF1) were determined by quantitative real-time polymerase chain reaction or western blot assay. Cell proliferation was assessed by colony formation assay. Cell migration and invasion were evaluated by transwell assay. Glycolysis was analyzed by measuring extracellular acidification rate, glucose uptake, and lactate production. Also, the protein levels of glucose transporter 1 and lactate dehydrogenase A were detected using western blot. The relationship among circ_0000745, miR-409-3p, and ATF1 were confirmed by dual-luciferase reporter assay. Moreover, xenograft assay was performed to analyze tumor growth in vivo. Results: Circ_0000745 and ATF1 were upregulated, whereas miR-409-3p was downregulated in CC tissues and cells. Knockdown of circ_0000745 repressed proliferation, migration, invasion, and glycolysis of CC cells. Circ_0000745 regulated CC progression by targeting miR-409-3p. Circ_0000745 modulated ATF1 expression through sponging miR-409-3p. MiR-409-3p hindered CC progression by targeting ATF1. Furthermore, depletion of circ_0000745 impeded tumor growth in vivo. Conclusion: Circ_0000745 promoted the progression of CC through modulating miR-409-3p/ATF1 axis, indicating a promising biomarker for CC therapy.

Long non-coding RNA DNM3OS/miR-204-5p/HIP1 axis modulates oral cancer cell viability and migration

BACKGROUND

Non-coding RNAs play a critical role in the occurrence and development of oral cancer. The present study is aimed to identify long non-coding RNA (lncRNA) that might be novel effective targets for the treatments of oral cancer and the underlying mechanism.

METHODS

The microarray profiling and RNA-sequencing analysis were performed to identify lncRNAs related to oral cancer development, and lncRNA DNM3OS was selected. DNM3OS knockdown was generated in cancer cell lines, and the specific effects of DNM3OS knockdown on cell phenotype were examined. DNM3OS targeted miRNA and miRNA targeted downstream mRNA were selected, the predicted bindings were verified, and the specific effects of miRNA on oral cancer cells were examined. Finally, the dynamic effects of DNM3OS and miRNA on target mRNA expression and oral cancer cell phenotype were examined.

RESULTS

DNM3OS was upregulated in oral cancer tissues and cells. DNM3OS knockdown in CAL27 and SCC-9 cells inhibited cell viability and migration. DNM3OS targeted miR-204-5p to inhibit miR-204-5p expression. miR-204-5p overexpression suppressed oral cancer cell aggressiveness. miR-204-5p targeted HIP1 to inhibit HIP1 expression. HIP1 knockdown inhibited oral cancer cell viability and migration. The effects of DNM3OS knockdown were significantly reversed by miR-204-5p inhibition. Within oral carcinoma tissue samples, expression of DNM3OS and HIP1 was increased whereas the miR-204-5p expression was downregulated; miR-204-5p had a negative correlation with DNM3OS and HIP1, respectively, while DNM3OS and HIP1 were positively correlated with each other.

CONCLUSION

Long non-coding RNA DNM3OS, miR-204-5p, and HIP1 form an axis that modulates oral cancer cell viability and migration.

Circular RNA circ_0000284 plays an oncogenic role in the progression of non-small cell lung cancer through the miR-377-3p-mediated PD-L1 promotion

Background

Circular RNAs (circRNAs), a subgroup of non-coding RNAs, are recognized as pivotal mediators in various types of cancers. CircRNA_0000284 (circ_0000284) was manifested to participate in the development of non-small cell lung cancer (NSCLC). The novel functional mechanism of circ_0000284 in NSCLC was investigated in our current study.

Methods

We exploited quantitative real-time polymerase chain reaction (qRT-PCR) to analyze the relative RNA (circRNA, miRNA and mRNA) expression. The assessment of cell proliferation and colony formation was executed by Cell Counting Kit-8 (CCK-8) and colony formation assay, respectively. Transwell assay was implemented to examine cell migration and invasion. All protein levels were assayed using western blot. The role of circ_0000284 in vivo was evaluated via xenograft model. The target relation was estimated by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.

Results

As for the biological characterization, circ_0000284 was highly stable and localized in the cytoplasm. Circ_0000284 was up-regulated in NSCLC and could predict poor prognosis of NSCLC patients. Both in vitro and in vivo, down-regulation of circ_0000284 refrained tumorigenesis of NSCLC. Besides, microRNA-377-3p (miR-377-3p) was a miRNA target of circ_0000284, and targeted programmed death-ligand 1 (PD-L1). Circ_0000284 was a cancer-promoting circRNA in NSCLC via regulating the miR-377-3p/PD-L1 axis.

Conclusion

Thus, our results unraveled that circ_0000284 facilitated the progression of NSCLC by up-regulating the PD-L1 expression as a competing endogenous RNA (ceRNA) of miR-377, possibly developing a different perspective in understanding the molecular pathogenesis of NSCLC.

Circle RNA circABCB10 Modulates PFN2 to Promote Breast Cancer Progression, as Well as Aggravate Radioresistance Through Facilitating Glycolytic Metabolism Via miR-223-3p

Background: Breast cancer (BC) is a common tumor in women worldwide, and irradiation (IR) resistance is a major obstacle for BC therapy. Circle RNAs (circRNAs) were identified as implicated in the progression of cancer and IR resistance. However, the role of circABCB10 in BC progression and IR resistance is not well defined. Materials and Methods: The levels of circABCB10, miR-223-3p, and profilin-2 (PFN2) were detected by quantitative real-time polymerase chain reaction. The cell viability and survival rate were monitored by MTT assay. The glucose consumption, lactic acid production, LDH-A activity, and ATP production were evaluated to measure glycolysis. The protein levels of hypoxia inducible factor-1α (HIF-1α), hexokinase 2 (HK2), lactate dehydrogenase A chain (LDH-A), and PFN2 were estimated by Western blot assay. The colony formation rate was tested by colony formation assay. Dual-luciferase reporter assay was constructed to validate the interaction between miR-223-3p and circABCB10 or PFN2. The mice xenograft assay was performed to further verify the effects of circABCB10 on BC progression in vivo. Results: CircABCB10 and PFN2 were elevated, while miR-223-3p was reduced in BC tissues and cells. CircABCB10 sponged miR-223-3p, and PFN2 was a target of miR-223-3p in BC cells. CircABCB10 silencing inhibited cell proliferation, glycolysis, colony formation, and decreased IR resistance in BC cells by modulating miR-223-3p. Meanwhile, circABCB10 depletion restrained xenograft tumor growth in vivo. Also, miR-223-3p overexpression refrained cell proliferation, glycolysis, and colony formation while improving IR sensitivity in BC cells by regulating PFN2. Besides, circABCB10 knockdown declined PFN2 in BC cells via miR-223-3p. The glycolysis inhibitor 2-deoxy-D-glucose enhanced IR sensitivity in BC cells via circABCB10. Conclusion: CircABCB10 knockdown contributed to irradiation sensitivity by negatively regulating glycolysis via the miR-223-3p/PFN axis in breast cancer.

Suppression of Circular RNA Hsa_circ_0109320 Attenuates Non-Small Cell Lung Cancer Progression via MiR-595/E2F7 Axis

Background

Circular RNAs (circRNAs) are frequently aberrantly expressed in non-small cell lung cancer (NSCLC) and are considered to exert a pivotal role in the occurrence and development of NSCLC via targeting and negatively regulating microRNAs (miRNAs). We aimed to investigate the role of hsa_circ_0109320 in the proliferation, invasion and apoptosis of NSCLC, and explore its underlying molecular mechanism.

Material/Methods

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis was performed to determine the circ_0109320 and miR-595 expression in tissues or cells. Western blot analysis was conducted to examine the cleaved caspase-3, Bax, Bcl-2, and E2F7 protein expression. Transwell detection was used to evaluate the invasion level of NSCLC cell lines.

Results

The results of present study indicated that circ_0109320 expression in NSCLC patients was upregulated significantly in tumor tissues compared with tissues adjacent to carcinoma. Upregulated circ_0109320 level was significantly associated with TNM stages as well as lymph node metastasis of NSCLC. Moreover, downregulation of circ_0109320 attenuated proliferation and invasion while promoting apoptosis in NSCLC cells. We further confirmed that circ_0109320 could sponge miR-595 to upregulate E2F7 expression. Silencing of miR-595 or overexpression of E2F2 could partially reversed the inhibitory role of circ_0109320 knockdown in NSCLC cells. These data provided evidence that the suppression of circ_0109320 attenuates NSCLC cell proliferation and invasion and enhances apoptosis through the miR-595/E2F7 pathway.

Conclusions

Circ_0109320/miR-595/E2F2 axis may exert a pivotal role in the pathological mechanism of NSCLC progression, and it has potential application in the future treatment of NSCLC.

Circular RNA circMDM2 accelerates the glycolysis of oral squamous cell carcinoma by targeting miR-532-3p/HK2

Circular RNAs (circRNAs) function as an essential regulator in the progression of oral squamous cell carcinoma (OSCC). However, the potential roles and mechanism of circRNAs in OSCC are still elusive. Here, this research investigates the roles and molecular mechanism of novel circRNA (circMDM2) in OSCC progression. Clinically, circMDM2 was overexpressed in OSCC tissue and cells, and the overexpression served as a poor prognostic factor for OSCC patients. Functionally, cellular experiments confirmed that circMDM2 accelerated OSCC cell proliferation and glycolysis in vitro and circMDM2 knockdown repressed the tumour growth in vivo. Mechanistically, circMDM2 sponged miR‐532‐3p to promote the hexokinase 2 (HK2), forming the circMDM2/miR‐532‐3p/HK2 axis. In conclusion, these findings demonstrated that circMDM2/miR‐532‐3p/HK2 axis promotes the proliferation and glycolysis of OSCC, rendering a potential diagnostic biomarker and prospective therapeutic target for OSCC.

Dysregulation of CircRNA_0001946 Contributes to the Proliferation and Metastasis of Colorectal Cancer Cells by Targeting MicroRNA-135a-5p

This study was aimed to evaluate the potential function of circ-0001946 in the progression of colorectal cancer (CRC) and the related regulatory mechanism. First, the expression levels of circRNA_0001946 and microRNA-135a-5p (miR-135a-5p) in normal and CRC tissues were measured by quantitative real-time polymerase chain reaction (RT-qPCR). In addition, cell proliferation was assessed by the Cell Counting Kit-8 (CCK-8) assay, cell migration and invasion were evaluated by Transwell assays, and the cell cycle patterns were determined by flow cytometry. The relationship between the expression levels of circ_0001946 and miR-135a-5p was determined by dual-luciferase reporter assays. Our data showed that the expression of circ_0001946 was upregulated in CRC tissues, which was negatively correlated with tumor size, histologic grade, lymphatic metastasis, and TMN stage, and patients with circ_0001946 overexpression were more likely to have a poor prognosis. In addition, in vitro experiments showed that silencing circ_0001946 inhibited the epithelial–mesenchymal transition (EMT) pathway and markedly suppressed CRC cell growth, migration, and invasion. Furthermore, we discovered that the transfection of miR-135a-5p mimics could reverse the antitumor effects of circRNA_0001946 downregulation. To summarize, this study revealed that circRNA_0001946 might act as a tumor promoter by activating the miR-135a-5p/EMT axis and may be a promising treatment target for CRC.

CircLARP4 Suppresses Cell Proliferation, Invasion and Glycolysis and Promotes Apoptosis in Non-Small Cell Lung Cancer by Targeting miR-135b

Background

CircLARP4 is reported to act as a tumor suppressor in some cancers. However, the detailed roles and molecular basis of circLARP4 in non-small cell lung cancer (NSCLC) tumorigenesis are still unclear. The aim of the study is to explore the potential roles and molecular basis of circLARP4 in NSCLC tumorigenesis.

Materials and Methods

qRT-PCR was taken to detect circLARP4 and miR-135b expressions. MTT assay, transwell invasion assay and flow cytometry analysis were applied to evaluate cell proliferation, invasion and apoptosis, respectively. Glycolysis was assessed by measuring hexokinase2 (HK2) expression, glucose consumption and lactate production. Association between circLARP4 and miR-135a was examined by luciferase reporter and RIP assays. The changes of the phosphatase and tension homolog (PTEN)/protein kinase B (AKT)/hypoxia-inducible factor-1α (HIF-1α) pathway were evaluated by Western blot. The nude mouse xenograft models were applied to verify the regulation of circLARP4 in vivo.

Results

CircLARP4 was decreased in NSCLC tissues and cells. CircLARP4 overexpression blocked cell proliferation and invasion, and facilitated apoptosis in NSCLC cells. Meanwhile, circLARP4 overexpression suppressed glycolysis in NSCLC cells, as evidenced by the reduced HK2, glucose consumption and lactate production levels. Further analyses proved a downregulation of miR-135b by circLARP4 in a ceRNA-dependent manner in NSCLC cells. CircLARP4-mediated tumor suppression on NSCLC progression was partially overturned by overexpressing miR-135b. Moreover, we confirmed that circLARP4 had antitumor effect on xenograft tumors and downregulated miR-135b. Furthermore, circLARP4 overexpression inhibited the PTEN/AKT/HIF-1α pathway in NSCLC cells and xenograft tumors by downregulating miR-135b.

Conclusion

Our findings suggested that circLARP4 suppressed NSCLC progression by sponging miR-135b through inactivation of the PTEN/AKT/HIF-1α pathway, which broadens our understanding concerning the roles of circLARP4 in NSCLC tumorigenesis.

Functional and Clinical Impact of CircRNAs in Oral Cancer

The increasing number of recently published works regarding the role of circular RNAs (circRNAs) in oral cancer highlights the key contribution of this novel class of endogenous noncoding RNAs as regulators of critical signaling pathways and their clinical value as novel biomarkers. This review summarizes and puts into context the existing literature in order to clarify the relevance of circRNAs as novel mediators of oral cancer pathogenesis as well as their potential usefulness as predictors of clinical outcome and response to therapy in this disease.

Non-coding RNAs: Key regulators of aerobic glycolysis in breast cancer

Although extensive research progress has been made in breast cancer in recent years, yet the morbidity and mortality rates of breast cancer are rising, making it the major disease that endangers women's health. Energy metabolism reprogramming is featured by a state termed "aerobic glycolysis" or the Warburg effect that glycolysis is preferred even under aerobic conditions in neoplastic diseases. Widely acknowledged as an emerging hallmark in cancers, this metabolic switch shows a sophisticated role in the pathogenesis of breast cancer. The regulating effect of non-coding RNAs (ncRNAs) composed of microRNAs, long non-coding RNAs and circular RNAs is closely related to the glycolysis in breast cancer. Therefore, understand the mechanisms of ncRNAs of aerobic glycolysis in breast cancer may provide new strategy for the disease.

CircRNA_0005075 suppresses carcinogenesis via regulating miR-431/p53/epithelial-mesenchymal transition axis in gastric cancer

This study was aimed to explore the expression and biological function of circRNA_0005075 in gastric cancer (GC) progression and its underlying mechanism. First, the expression level of circRNA_0005075 and microRNA-431 (miR-431) in GC tissues were detected with the quantitative real-time polymerase chain reaction. In addition, after down-regulated the circRNA_0005075 expression by plasmid transfection in GC cells, the Cell Counting Kit-8 (CCK-8), EDU, transwell assay were conducted to evaluate the function of circRNA_0005075 or miR-431 on cell proliferation, metastasis in vitro. Moreover, p53 and Epithelial-mesenchymal transition (EMT) pathway related proteins were also measured with western blotting. Then, our data revealed that CircRNA_0005075 was found to be significantly up-regulated in GC tissues as well as GC cell lines, and the GC patients with higher CircRNA_0005075 expression were more likely to have poor outcomes. Down-regulation of CircRNA_0005075 could significantly suppress the GC cell proliferation and cell metastasis ability, while the addition of miR-431 inhibitors could counteract this effect. Importantly, we discovered that the silencing of circRNA_0005075 could weaken the micro-RNA sponge function for miR-431, and then upregulate the expression of p53 and forbid the EMT signalling pathway, and finally suppress the tumourigenesis of GC. To sum up, CircRNA_0005075 could inhibit cell growth and metastasis of GC through regulating the miR-431/p53/EMT axis. SIGNIFICANCE OF THE STUDY: The research clearly elucidated the potential role and relative regulatory mechanism of circRNA_0005075 in gastric cancer (GC) progression. Briefly, circRNA_0005075 could directly inhibit the expression level of miR-431, then regulate the p53/Epithelial-mesenchymal transition axis, and finally inhibit cell growth and metastasis in GC. Consequently, circRNA_0005075 might act as an oncogene in the GC procession, which provides a promising way for the treatment of GC.

miR-4999-5p Predicts Colorectal Cancer Survival Outcome and Reprograms Glucose Metabolism by Targeting PRKAA2

Purpose

Colorectal cancer (CRC) is the third most common cancer, and the second leading cause of cancer death worldwide. Dysregulation of microRNAs has been shown to modulate glucose metabolic reprogramming in CRC. However, the functional role of miR-4999-5p in the CRC glucose metabolic shift has not been characterized.

Patients and Methods

The levels of miR-4999-5p and PRKAA2 were evaluated by RT-qPCR. Univariate and multivariate survival analyses were conducted to evaluate the prognostic value of miR-4999-5p. Cell proliferation was assessed using the CCK-8 and colony formation assays. Extracellular acidification rate, glucose uptake, cellular glucose-6-phosphate level, and lactate production were evaluated to assess the effects of miR-4999-5p on CRC glycolysis. Dual-luciferase reporter assay was conducted to investigate the direct interaction between miR-4999-5p and PRKAA2. Mouse xenograft models were established to assess the functions of miR-4999-5p in vivo.

Results

miR-4999-5p was highly expressed in CRC tissues and cell lines. In addition, miR-4999-5p was associated with tumor differentiation and TNM stage, and elevated expression of miR-4999-5p was an independent predictor of poorer overall survival. Furthermore, miR-4999-5p promoted cell proliferation and glycolysis in CRC. miR-4999-5p targeted PRKAA2 to exert its tumor-promoting functions, and PRKAA2 knockdown rescued decreased cell proliferation and glycolysis in miR-4999-5p-silenced CRC cells. In vivo experiments showed that miR-4999-5p promoted CRC growth.

Conclusion

miR-4999-5p facilitated cell growth and glucose metabolic reprogramming through direct targeting of PRKAA2. Our results showed that miR-4999-5p may be a novel prognostic marker and therapeutic target for CRC.

circRNA_0000140 suppresses oral squamous cell carcinoma growth and metastasis by targeting miR-31 to inhibit Hippo signaling pathway

Oral squamous cell carcinoma (OSCC) is one of the most common malignancies and has a poor prognosis. Circular RNA (circRNA) has been increasingly recognized as a crucial contributor to carcinogenesis. circRNA_0000140 has been aberrantly expressed in OSCC, but its role in tumor growth and metastasis remains largely unclear. Sanger sequencing, actinomycin D, and RNase R treatments were used to confirm head-to-tail junction sequences and the stability of circ_0000140. In vitro cell activities, including proliferation, migration, invasion, and apoptosis, were determined by colony formation, transwell, and flow cytometry assays. The expression levels of circ_0000140, Hippo signaling pathway, and serial epithelial–mesenchymal transition (EMT) markers were measured by quantitative real-time PCR, western blotting, immunofluorescence, and immunohistochemistry. Dual luciferase reporter assays and Argonaute 2-RNA immunoprecipitation assays were performed to explore the interplay among circ_0000140, miR-31, and LATS2. Subcutaneous tumor growth was observed in nude mice, in which in vivo metastasis was observed following tail vein injection of OSCC cells. circ_0000140 is derived from exons 7 to 10 of the KIAA0907 gene. It was down-regulated in OSCC tissues and cell lines, and correlated negatively with poor prognostic outcomes in OSCC patients. Gain-of-function experiments demonstrated that circ_0000140 enhancement suppressed cell proliferation, migration, and invasion, and facilitated cell apoptosis in vitro. In xenograft mouse models, overexpression of circ_0000140 was able to repress tumor growth and lung metastasis. Furthermore, mechanistic studies showed that circ_0000140 could bind with miR-31 and up-regulate its target gene LATS2, thus affecting OSCC cellular EMT. Our findings demonstrated the roles of circ_0000140 in OSCC tumorigenesis as well as in metastasis, and circ_0000140 exerts its tumor-suppressing effect through miR-31/LATS2 axis of Hippo signaling pathway in OSCC.

Overexpression of circRNA_100290 promotes the progression of laryngeal squamous cell carcinoma through the miR-136-5p/RAP2C axis

Circular RNAs (circRNAs) exert critical functions in tumorigenesis and tumor development, but whether and how circRNAs contribute to laryngeal squamous cell carcinoma (LSCC) is unclear. In this study, we explored the function and mechanisms of circRNA_100290 in LSCC. Tissue samples were obtained from 40 patients with LSCC. The expression of circRNA_100290 and other targets was measured through quantitative reverse transcription-polymerase chain reaction and western blot analysis. Cell proliferation, colony-forming ability, and apoptosis were tested using CCK-8 assay and EdU assay, colony formation assay, and flow cytometry, respectively. Cell migration and invasion were detected by Transwell assay. Moreover, the interactions between circRNA_100290, miR-136-5p, and RAP2C were analyzed by bioinformatics, and verified by dual-luciferase reporter assays. Here, we found that circRNA_100290 expression was significantly upregulated in LSCC tissues and cell lines compared with the normal controls. Expression of circRNA_100290 positively correlated with advanced TNM stage and lymph node metastasis in LSCC patients. In cell culture, upregulation of circRNA_100290 promoted LSCC cell proliferation, migration, and invasion, while it inhibited cell apoptosis; downregulating circRNA_100290 exerted the opposite effects. In vivo, circRNA_100290 overexpression dramatically promoted tumor growth. Mechanistically, circRNA_100290 may act as a sponge of miR-136-5p, and inhibiting miR-136-5p in LSCC cells indeed reversed the effects of circRNA_100290 downregulation. The RAS oncogene RAP2C was predicted to be a target of miR-136-5p, and downregulating RAP2C in LSCC cells partially reversed the oncogenic effects of circRNA_100290 overexpression or miR-136-5p decrease. Our findings suggest that circRNA_100290 promotes LSCC progression by targeting the miR-136-5p/RAP2C axis, which may lead to the identification of potential therapeutic targets.

Retracted Article: Overexpression of circ_0034642 contributes to hypoxia-induced glycolysis, cell proliferation, migration and invasion in gliomas by facilitating TAGLN2 expression via sponging miR-625-5p

Glioma is an aggressive brain cancer with poor prognosis and high invasiveness. Dysregulation of circular RNAs (circRNAs) has been widely discovered in various cancers, including glioma. However, the molecular mechanism of circ_0034642 in glioma is still unclear. The expression of circ_0034642, microRNA (miR)-625-5p and transgelin-2 (TAGLN2) in glioma tumors and cells was detected by performing a quantitative real-time polymerase chain reaction (qRT-PCR). The stability of circ_0034642 was determined by carrying out RNase R treatment. Cell proliferation was evaluated by performing the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. Glycolysis was analyzed by measuring the extracellular acidification rate (ECAR) using glucose detection and lactic acid detection kits. Cell migration and invasion were determined by performing the transwell assay. Protein expression levels of the proteins hexokinase 2 (HK2), matrix metalloproteinase-2 (MMP2), matrix metalloproteinase-9 (MMP9) and TAGLN2 were analyzed using western blots. The interaction between miR-625-5p and circ_0034642 or TAGLN2 was proved using a dual-luciferase reporter system. Animal models were established by subcutaneously injecting glioma cells stably transfected with sh-NC or sh-circ_0034642. Circ_0034642 and TAGLN2 were overexpressed whereas miR-625-5p was expressed at low levels in glioma tumors and cells. Moreover, circ_0034642 and TAGLN2 were upregulated while miR-625-5p was downregulated under hypoxic conditions in a time-dependent manner. Next, elimination of circ_0034642 was shown to inhibit cell glycolysis, proliferation, migration and invasion under hypoxic conditions in gliomas. Then, we found that circ_0034642 acted as a “sponge” of miR-625-5p while TAGLN2 acted as a target of miR-625-5p. In addition, recovery of circ_0034642 attenuated the repression mediated by miR-625-5p on glioma cell glycolysis and progression under hypoxic conditions. Meanwhile, an inhibitor of miR-625-5p alleviated TAGLN2 deficiency-induced inhibition of glioma cell development under hypoxic conditions. We also discovered that circ_0034642 could interact with miR-625-5p and further alter the expression of TAGLN2. Lastly, a circ_0034642 knockdown hindered tumor growth in vivo by regulating the miR-625-5p/TAGLN2 axis. Enhanced expression of circ_0034642 was found to promote cell glycolysis, proliferation, migration and invasion under hypoxic conditions in gliomas by sponging miR-625-5p to improve TAGLN2 expression, providing prospective biomarkers for the diagnosis of glioma.

Circ_0034642 was upregulated under hypoxic conditions in gliomas.

Identification of Serum Exosomal hsa-circ-0004771 as a Novel Diagnostic Biomarker of Colorectal Cancer

Background: Exosomal circular RNAs (circRNAs) in peripheral blood are considered as emerging diagnostic biomarkers of cancers. Owing to the lack of sensitive and specific biomarkers, a large number of colorectal cancer (CRC) patients were diagnosed in advanced stages leading to high mortality. This study aimed to identify circulating exosomal circRNAs as novel diagnostic biomarkers of CRC.

Materials and Methods: Candidate circRNA was selected by integrating analysis of Gene Expression Omnibus (GEO) database with online program GEO2R. A total of 170 patients and 45 healthy controls were enrolled to assess the diagnostic value of circRNAs for CRC. Exosomes isolated from the serum of participants and cell cultured media were confirmed by transmission electron microscope (TEM), Nanoparticle Tracking Analysis and western blot. The expression and the diagnostic utility of circRNA were tested by qRT-PCR and receiver operating characteristic (ROC) analysis, respectively.

Results: The circulating exosomal hsa-circ-0004771 with most abundant among the top ten differentially expressed circRNAs (fold change ≥1.5) was selected for further study based on the results of GEO dataset analysis. The up-regulated exosomal hsa-circ-0004771 was verified in serum of CRC patients compared to healthy controls (HCs) and patients with benign intestinal diseases (BIDs) by qRT-PCR. The area under the ROC curves (AUCs) of circulating exosomal hsa-circ-0004771 were 0.59 (95%CI, 0.457–0.725), 0.86 (95%CI, 0.785–0.933) and 0.88 (95%CI, 0.815–0.940) to differentiate BIDs, stage I/II CRC patients and CRC patients from HCs, respectively. The AUC was 0.816 (95%CI, 0.728–0.9) to differentiate stage I/II CRC patients from patients with BIDs. In addition, the elevated expression of exosomal hsa-circ-0004771 in the serum of CRC patients was tumor-derived. It was found that the expression of exosomal hsa-circ-0004771 was down-regulated expression of in the serum of postoperative CRC patients as well as cultured media of CRC cells treated with GW4869.

Conclusions: Circulating exosomal hsa-circ-0004771 was significantly up-regulated in CRC patients and served as a novel potential diagnostic biomarker of CRC.