Circular RNA circ_0000039 enhances gastric cancer progression through miR-1292-5p/DEK axis

Emerging roles of CircRNA-miRNA networks in cancer development and therapeutic response

The complex interplay of epigenetic factors is essential in regulating the hallmarks of cancer and orchestrating intricate molecular interactions during tumor progression. Circular RNAs (circRNAs), known for their covalently closed loop structures, are non-coding RNA molecules exceptionally resistant to enzymatic degradation, which enhances their stability and regulatory functions in cancer. Similarly, microRNAs (miRNAs) are endogenous non-coding RNAs with linear structures that regulate cellular biological processes akin to circRNAs. Both miRNAs and circRNAs exhibit aberrant expressions in various cancers. Notably, circRNAs can function as sponges for miRNAs, influencing their activity. The circRNA/miRNA interaction plays a pivotal role in the regulation of cancer progression, including in brain, gastrointestinal, gynecological, and urological cancers, influencing key processes such as proliferation, apoptosis, invasion, autophagy, epithelial-mesenchymal transition (EMT), and more. Additionally, this interaction impacts the response of tumor cells to radiotherapy and chemotherapy and contributes to immune evasion, a significant challenge in cancer therapy. Both circRNAs and miRNAs hold potential as biomarkers for cancer prognosis and diagnosis. In this review, we delve into the circRNA-miRNA circuit within human cancers, emphasizing their role in regulating cancer hallmarks and treatment responses. This discussion aims to provide insights for future research to better understand their functions and potentially guide targeted treatments for cancer patients using circRNA/miRNA-based strategies.

circ-ATAD1 as Competing Endogenous RNA for miR-191-5p Forces Non-small Cell Lung Cancer Progression

The association of circular RNAs (circRNAs) with non-small cell lung cancer (NSCLC) has been recognized extensively. In view of this, our study particularly surveyed the underlying mechanism of circ-ATAD1 in the disease. First, an analysis of the clinical expression of circ-ATPase family AAA domain containing 1 (ATAD1) was performed, followed by further evaluation of the relationship between circ-ATAD1 expression and prognosis. Then, A549 cells were treated with single transfection or combined transfection with the plasmid vectors that interfere with circ-ATAD1 or miR-191-5p. circ-ATAD1 and miR-191-5p levels were detected by reverse transcription quantitative polymerase chain reaction to verify the transfection success. Then, cell proliferation was checked by cell count kit-8 and clonal formation test. Cell apoptosis was analyzed by flow cytometry. Cell migration and invasion were examined by wound healing assay and Transwell. Finally, the targeting of miR-191-5p to circ-ATAD1 or Forkhead Box K1 (FOXK1) was verified by bioinformation website starBase analysis and dual-luciferase reporter assay. circ-ATAD1 was expressed abundantly in tumor tissues of NSCLC patients and had a predictive value in poor prognosis. circ-ATAD1 underexpression or miR-191-5p overexpression could obstruct A549 cells to behave aggressively, while circ-ATAD1 upregulation or miR-191-5p depletion resulted in the promotion of aggressiveness of A549 cells. Interestingly, circ-ATAD1 could decoy miR-191-5p. miR-191-5p negatively regulated FOXK1 expression, and downregulating miR-191-5p or upregulating FOXK1 rescued circ-ATAD1 downregulation-mediated influences on NSCLC cells. circ-ATAD1 accelerates NSCLC progression by absorbing miR-191-5p to upregulate FOXK1 expression.

Hsa_circ_0087862 contributes to the progression of colorectal cancer through regulating miR-512-3p/HK2 axis

BACKGROUND

Colorectal cancer (CRC) theratened thousands of people every year. Emerging evidences suggested that circular RNAs (circRNAs) were involved in CRC malignancies. However, the underlying mechanisms have yet not been revealed.

METHODS

Quantitative real-time PCR (qRT-PCR) was used to determine the expression of circ_0087862 and microRNA-512-3p (miR-512-3p). Western blot was performed to measure the protein expression of hexokinase 2 (HK2), B-cell lymphoma-2 (Bcl-2), BCL2-associated X (Bax) and BCL2 antagonist/killer 1 (Bak). Moreover, 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2-H-tetrazolium bromide (MTT) assay, colony formation and 5-ethynyl-2'-deoxyuridine (EdU) assay were employed to assess CRC cell proliferation. Also, migration/invasion abilities and apoptosis rates were investigated by transwell assay and flow cytometry. Glucose consumption, lactate production and ATP production were detected using the corresponding kits. Dual-luciferase reporter analysis and RNA immunoprecipitation (RIP) experiments were utilized to analyze the target association of miR-512-3p and circ_0087862 or HK2. Finally, xenograft assay was carried out to analyze the function of circ_0087862 in tumor growth in vivo.

RESULTS

Circ_0087862 expression was elevated in CRC tissues and cells. Circ_0087862 silencing repressed cell viabilities, proliferation, migration/invasion and glycolysis, and reinforced cell apoptosis. However, HK2 could weaken these impacts. Additionally, miR-512-3p targeted HK2, and circ_0087862 could regulate HK2 expression by miR-512-3p. Furthermore, circ_0087862 silencing decreased CRC cell xenograft tumor growth.

CONCLUSION

Collectively, our data suggested that circ_0087862 knockdown impeded cell viabilities, proliferation, and glycolysis, and contributed to cell apoptosis in CRC, indicating circ_0087862 as a promising tumor promoter.

CircPRDM5 inhibits the proliferation, migration, invasion, and glucose metabolism of gastric cancer cells by reducing GCNT4 expression in a miR-485-3p-dependent manner

Circular RNA (circRNA) plays a key part in the pathological process of gastric cancer (GC). The study is organized to analyze the function of circPRDM5 in GC cell tumor properties. Expression levels of circPRDM5, miR-485-3p, glucosaminyl (N-acetyl) transferase 4 (GCNT4), ki67, E-cadherin, N-cadherin, and hexokinase 2 (HK2) were analyzed by quantitative real-time polymerase chain reaction (PCR), Western blotting or immunohistochemistry assay. Cell proliferation was assessed by cell colony formation assay and 5-ethynyl-2'-deoxyuridine assay. Cell migration and invasion were investigated by transwell assay. Glycolysis was evaluated by the Seahorse XF Glycolysis Stress Test Kit. Dual-luciferase reporter assay and RNA pull-down assay were performed to identify the associations among circPRDM5, miR-485-3p, and GCNT4. Xenograft mouse model assay was conducted to determine the effects of circPRDM5 on tumor formation in vivo. CircPRDM5 and GCNT4 expression were downregulated, while miR-485-3p expression was upregulated in GC tissues and cells when compared with paracancerous tissues or human gastric epithelial cells. CircPRDM5 overexpression inhibited proliferation, migration, invasion, and glucose metabolism of GC cells; however, circPRDM5 depletion had the opposite effects. CircPRDM5 repressed tumor properties of GC cells in vivo. MiR-485-3p restoration relieved circPRDM5-induced effects in GC cells. GCNT4 overexpression remitted the promoting effects of miR-485-3p mimics on GC cell malignancy. CircPRDM5 acted as a sponge for miR-485-3p, and GCNT4 was identified as a target gene of miR-485-3p. Moreover, circPRDM5 regulated GCNT4 expression by interacting with miR-485-3p.CircPRDM5 acted as a miR-485-3p sponge to inhibit GC progression by increasing GCNT4 expression, proving a potential target for GC therapy.

The Tumorigenic Role of Circular RNA-MicroRNA Axis in Cancer

Circular RNAs (circRNAs) are a class of endogenous RNAs that control gene expression at the transcriptional and post-transcriptional levels. Recent studies have increasingly demonstrated that circRNAs act as novel diagnostic biomarkers and promising therapeutic targets for numerous cancer types by interacting with other non-coding RNAs such as microRNAs (miRNAs). The miRNAs are presented as crucial risk factors and regulatory elements in cancer by regulating the expression of their target genes. Some miRNAs are derived from transposable elements (MDTEs) that can transfer their location to another region of the genome. Genetic interactions between miRNAs and circular RNAs can form complex regulatory networks with various carcinogenic processes that play critical roles in tumorigenesis and cancer progression. This review focuses on the biological regulation of the correlative axis among circular RNAs, miRNAs, and their target genes in various cancer types and suggests the biological importance of MDTEs interacting with oncogenic or tumor-suppressive circRNAs in tumor progression.

CircBFAR correlates with poor prognosis and promotes laryngeal squamous cell cancer progression through miR-31-5p/COL5A1 axis

Introduction

Laryngeal squamous cell cancer (LSCC) is a highly malignant tumor originating from the respiratory system. Circular RNAs have been reported to be associated with the treatment and prognosis of a variety of cancers, including LSCC.

Methods

The expression of circBFAR, miR-31-5p, and collagen type V alpha 1 chain (COL5A1) in LSCC tissues and cells was detected by quantitative real-time polymerase chain reaction. Cell counting kit 8 and 5-Ethynyl-2'-deoxyuridine assays were used to detect cell proliferation. Wound healing assay and transwell assay were used to test cell migration and invasion, respectively. The protein expression in LSCC cells was detected with western blot. The relationships between miR-31-5p and circBFAR or COL5A1 were identified by dual-luciferase reporter assay, RNA-pull down assay, and immunoprecipitation assay. The effect of circBFAR on tumor growth in vivo was detected by tumor xenograft mice experiment. The protein expression of COL5A1 and KI-67 in LSCC tissues was measured by immunohistochemistry assay.

Results

CircBFAR was increased in LSCC tissues and cells, and was related to advanced clinical stage and overall survival of LSCC patients. The cell viability and proliferation were inhibited by circBFAR knockdown and silencing of circBFAR blocked migration and invasion of LSCC cells. CircBFAR knockdown suppressed cell tube formation, and the protein expression of KI-67, matrix metallopeptidase 2 (MMP2), and vascular endothelial growth factor A (VEGFA) in LSCC cells. MiR-31-5p was the target of circBFAR, and the inhibitory effects of circBFAR deficiency on viability, proliferation, migration, invasion, tube formation and the protein expression of KI-67, MMP2, and VEGFA in LSCC cells were rescued by miR-31-5p downregulation. COL5A1 was negatively regulated by miR-31-5p, and was boosted in LSCC tissues and cells. COL5A1 overexpression reversed the inhibitory effects of miR-31-5p on LSCC cells. CircBFAR insufficiency hindered tumor growth in vivo.

Conclusion

CircBFAR, miR-31-5p, and COL5A1 in LSCC progression might provide novel therapeutic targets for LSCC clinical intervention.

circFCHO2 promotes gastric cancer progression by activating the JAK1/STAT3 pathway via sponging miR-194-5p

circFCHO2 has been revealed to be overexpressed in gastric cancer (GC) patients. This article identified the function of circFCHO2 on GC progression. The expression of circFCHO2, miR-194-5p and JAK1 in 30 GC patients and cells was monitored by quantitative reverse transcription-polymerase chain reaction. circFCHO2 localization in GC cells was monitored by RNA fluorescence in situ hybridization. Cell counting kit-8 assay, 5-ethynyl-2-deoxyuridine staining, transwell experiment, tube formation and sphere formation experiments were applied to detect GC cell proliferation, invasion, angiogenesis and cancer stem cell characteristics. Dual-luciferase reporter gene assay, RNA pull down assay and RNA immunoprecipitation experiment were utilized to research the binding between two genes. In vivo tumorigenesis and lung metastasis were studied using nude mice. Immunohistochemistry and hematoxylin-eosin staining were conducted. Protein expression was assessed by Western blot. Serum exosomes of GC patients and healthy participants were isolated. circFCHO2 up-modulation in GC patients was related to poor outcome. circFCHO2 was located in the cytoplasm of GC cells. circFCHO2 silencing weakened the proliferation, invasion, angiogenesis and stem cell characteristics of GC cells. miR-194-5p knockdown counteracted this effect. circFCHO2 activated the JAK1/STAT3 pathway by sponging miR-194-5p. miR-194-5p overexpression attenuated the malignant phenotypes of GC cells. JAK1 overexpression abrogated this effect. circFCHO2 silencing weakened GC cells growth and lung metastasis in vivo. circFCHO2 was up-modulated in serum exosomes of GC patients. circFCHO2 was an oncogene in GC by activating the JAK1/STAT3 pathway via sponging miR-194-5p. circFCHO2 might be a novel target and diagnostic marker for GC.

The m6A Methyltransferase METTL3-Mediated N6-Methyladenosine Modification of DEK mRNA to Promote Gastric Cancer Cell Growth and Metastasis

Gastric cancer (GC) is the fifth most common cancer and the third deadliest cancer in the world, and the occurrence and development of GC are influenced by epigenetics. Methyltransferase-like 3 (METTL3) is a prominent RNA n6-adenosine methyltransferase (m6A) that plays an important role in tumor growth by controlling the work of RNA. This study aimed to reveal the biological function and molecular mechanism of METTL3 in GC. The expression level of METTL3 in GC tissues and cells was detected by qPCR, Western blot and immunohistochemistry, and the expression level and prognosis of METTL3 were predicted in public databases. CCK-8, colony formation, transwell and wound healing assays were used to study the effect of METTL3 on GC cell proliferation and migration. In addition, the enrichment effect of METTL3 on DEK mRNA was detected by the RIP experiment, the m6A modification effect of METTL3 on DEK was verified by the MeRIP experiment and the mRNA half-life of DEK when METTL3 was overexpressed was detected. The dot blot assay detects m6A modification at the mRNA level. The effect of METTL3 on cell migration ability in vivo was examined by tail vein injection of luciferase-labeled cells. The experimental results showed that METTL3 was highly expressed in GC tissues and cells, and the high expression of METTL3 was associated with a poor prognosis. In addition, the m6A modification level of mRNA was higher in GC tissues and GC cell lines. Overexpression of METTL3 in MGC80-3 cells and AGS promoted cell proliferation and migration, while the knockdown of METTL3 inhibited cell proliferation and migration. The results of in vitro rescue experiments showed that the knockdown of DEK reversed the promoting effects of METTL3 on cell proliferation and migration. In vivo experiments showed that the knockdown of DEK reversed the increase in lung metastases caused by the overexpression of METTL3 in mice. Mechanistically, the results of the RIP experiment showed that METTL3 could enrich DEK mRNA, and the results of the MePIP and RNA half-life experiments indicated that METTL3 binds to the 3'UTR of DEK, participates in the m6A modification of DEK and promotes the stability of DEK mRNA. Ultimately, we concluded that METTL3 promotes GC cell proliferation and migration by stabilizing DEK mRNA expression. Therefore, METTL3 is a potential biomarker for GC prognosis and a therapeutic target.

Long Non-Coding LEF1-AS1 Sponge miR-5100 Regulates Apoptosis and Autophagy in Gastric Cancer Cells via the miR-5100/DEK/AMPK-mTOR Axis

DEK and miR-5100 play critical roles in many steps of cancer initiation and progression and are directly or indirectly regulated by most promoters and repressors. LEF1-AS1 as a long non-coding RNA can regulate tumor development through sponge miRNA. The effect and regulatory mechanism of DEK on autophagy and apoptosis in gastric cancer (GC), and the role between miR-5100 and DEK or miR-5100 and LEF1-AS1 are still unclear. Our study found that DEK was highly expressed in gastric cancer tissues and cell lines, and knockdown of DEK inhibited the autophagy of cells, promoted apoptosis, and suppressed the malignant phenotype of gastric cancer. DEK regulates autophagy and apoptosis through the AMPK/mTOR signaling pathway. In addition, miR-5100 inhibits autophagy and promotes apoptosis in GC cells while LEF1-AS1 had the opposite effect. Studies have shown that miR-5100 acts by targeting the 3'UTR of DEK, and LEF1-AS1 regulates the expression of miR-5100 by sponging with mIR-5100. In conclusion, our results found that LEF1-AS1 and miR-5100 sponge function, and the miR-5100/DEK/AMPK/mTOR axis regulates autophagy and apoptosis in gastric cancer cells.

Monitoring Clinical-Pathological Grading of Hepatocellular Carcinoma Using MicroRNA-Guided Semiconducting Polymer Dots

MicroRNAs (miRNAs) are a class of small, noncoding RNAs involved in nearly all genetic central dogma processes and human biological behavior, which also play a significant role in the pathological activity of tumors, such as gene transcription, protein translation, and exosome secretion. Therefore, through the navigation of certain specific miRNAs, we can trace the specific physiological processes or image some specific tissues. Designing and accurately positioning microRNA (miRNA)-sensitive fluorescent nanoprobes with benign specificity and recognition in cells or tissues are a challenging research field. To solve the difficulties, we introduce four semiconducting polymer dots (Pdots) as nanoprobes linked by specific miRNA antisense sequences for monitoring the pathological grading by the variation in miRNA expression. Based on the base pairing principle, these miRNA-sensitive Pdots could bind to specific miRNAs within the cancerous cells. As impacted by the background of different pathology gradings, the proportions of the four hepatocellular carcinoma (HCC)-specific miRNAs within the cancerous cell are different, and the pathological grading of the patient tissues can be determined by comparing the palette combinations. The short single-stranded RNA-functionalized Pdots, which have excellent microRNA sensitivity, are observed in an experimental cell model and a series of tissue specimens from HCC patients for the first time. Using the Förster (or fluorescence) resonance energy transfer (FRET) model of Pdots and Cy3dt tag to simulate in vivo miRNA detection, the superior sensitivity and specificity of these nanoprobes are verified. The interference of subjective factors in traditional single/bis-dye emission intensity detection is abandoned, and multiple label staining is used to enhance sensitivity further and reduce the false-positive rate. The feasibility exhibited by this novel staining method is verified in normal hepatocellular HCC cell lines and 16 frozen ultrathin tissue sections, which are employed to quantify pathological grading-related color presentation systems for clinical doctors and pathologists' use. The intelligently designed miRNA-guided Pdots will emerge as an ideal platform with promising biological imaging.

The Circ_0001367/miR-545-3p/LUZP1 Axis Regulates Cell Proliferation, Migration and Invasion in Glioma Cells

Glioma is the most common primary intracranial malignant tumour in adults. It has a high incidence and poses a serious threat to human health. Circular RNA is a hotspot of cancer research. In this study, we aimed to explore the role of circ_0001367 in gliomagenesis and the underlying mechanism. First, qRT-PCR was conducted, which showed that circ_0001367 level was downregulated in glioma tissues and cells. Next, gain-of-function and loss-of-function assays were performed, which indicated that circ_0001367 inhibited the proliferation, migration and invasion of glioma cells. Subsequent bioinformatics analysis, dual-luciferase reporter assays, RNA immunoprecipitation assays and cell function assays demonstrated that circ_0001367 inhibited the proliferation, migration and invasion of glioma cells by absorbing miR-545-3p and thereby regulating the expression of leucine zipper protein (LUZP1). Finally, an in vivo experiment was conducted, which demonstrated that circ_0001367 inhibited glioma growth in vivo by modulating miR-545-3p and LUZP1. Taken together, the results of this study demonstrate that the circ_0001367/miR-545-3p/LUZP1 axis may be a novel target for glioma therapy.

Role of circular RNAs in gastrointestinal tumors and drug resistance

The incidence of gastrointestinal cancers has increased significantly over the past decade and gastrointestinal malignancies now rank among the leading causes of mortality globally. Although newer therapeutic strategies such as targeted therapies have greatly improved patient outcomes, their clinical success is limited by drug resistance, treatment failure and recurrence of metastatic disease. Therefore, there is an urgent need for further research identifying accurate and reliable biomarkers for precise treatment strategies. Circular RNAs (circRNAs) exhibit a covalently closed structure, high stability and biological conservation, and their expression is associated with the occurrence and development of gastrointestinal tumors. Moreover, circRNAs may significantly influence drug resistance of gastrointestinal cancers. In this article, we review the role of circRNAs in the occurrence and development of gastrointestinal cancer, their association with drug resistance, and potential application for early diagnosis, treatment and prognosis in gastrointestinal malignancies. Furthermore, we summarize characteristics of circRNA, including mechanism of formation and biological effects via mRNA sponging, chromatin replication, gene regulation, translational modification, signal transduction, and damage repair. Finally, we discuss whether circRNA-related noninvasive testing may be clinically provided in the future. This review provides new insights for the future development of diagnostics and therapeutics based on circRNAs in gastrointestinal tumors.