Biological Roles and Mechanisms of Circular RNA in Human Cancers

The circ_0003928/miR-31-5p/MAPK6 cascade affects high glucose-induced inflammatory response, fibrosis and oxidative stress in HK-2 cells

BACKGROUND

Diabetic nephropathy (DN) is a severe diabetic complication disorder. Circular RNAs (circRNAs) actively participate in DN pathogenesis. In this report, we sought to define a new mechanism of circ_0003928 in regulating high glucose (HG)-induced HK-2 cells.

METHODS

To construct a DN cell model, we treated HK-2 cells with HG. Cell viability and apoptosis were detected by CCK-8 and flow cytometry, respectively. The inflammatory cytokines were quantified by ELISA. Protein analysis was performed by immunoblotting, and mRNA expression was detected by quantitative PCR. The circ_0003928/miR-31-5p and miR-31-5p/MAPK6 relationships were validated by RNA pull-down and luciferase assays.

RESULTS

HG promoted HK-2 cell apoptosis, fibrosis and oxidative stress. Circ_0003928 and MAPK6 levels were enhanced and miR-31-5p level was decreased in HK-2 cells after HG treatment. Circ_0003928 disruption promoted cell growth and inhibited apoptosis, inflammatory response, fibrosis and oxidative stress in HG-induced HK-2 cells. Circ_0003928 targeted miR-31-5p, and MAPK6 was a target of miR-31-5p. Circ_0003928 regulated MAPK6 expression through miR-31-5p. The functions of circ_0003928 disruption in HG-induced HK-2 cells were reversed by miR-31-5p downregulation or MAPK6 upregulation.

CONCLUSION

Circ_0003928 exerts regulatory impacts on HG-induced apoptosis, inflammation, fibrosis and oxidative stress in human HK-2 cells by the miR-31-5p/MAPK6 axis.

Exploring the Key Signaling Pathways and ncRNAs in Colorectal Cancer

Colorectal cancer (CRC) is the third most prevalent cancer to be diagnosed, and it has a substantial mortality rate. Despite numerous studies being conducted on CRC, it remains a significant health concern. The disease-free survival rates notably decrease as CRC progresses, emphasizing the urgency for effective diagnostic and therapeutic approaches. CRC development is caused by environmental factors, which mostly lead to the disruption of signaling pathways. Among these pathways, the Wingless/Integrated (Wnt) signaling pathway, Phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling pathway, Mitogen-Activated Protein Kinase (MAPK) signaling pathway, Transforming Growth Factor-β (TGF-β) signaling pathway, and p53 signaling pathway are considered to be important. These signaling pathways are also regulated by non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). They have emerged as crucial regulators of gene expression in CRC by changing their expression levels. The altered expression patterns of these ncRNAs have been implicated in CRC progression and development, suggesting their potential as diagnostic and therapeutic targets. This review provides an overview of the five key signaling pathways and regulation of ncRNAs involved in CRC pathogenesis that are studied to identify promising avenues for diagnosis and treatment strategies.

CircRNA circRREB1 promotes tumorigenesis and progression of breast cancer by activating Erk1/2 signaling through interacting with GNB4

Current investigations have illuminated the essential roles played by circular RNAs (circRNAs) in driving breast cancer (BC) tumorigenesis. However, the functional implications and molecular underpinnings of most circRNAs in BC are not well characterized. Here, Circular RNA (circRNA) expression profiles were analyzed in four surgically resected BC cases along with adjacent non-cancerous tissues applying RNA microarray analysis. The levels and prognostic implications of circRREB1 in BC were subjected to quantitative real-time PCR (qRT-PCR) and in situ hybridization (ISH). Experimental manipulation of circRREB1 levels in both in vivo and in vitro settings further delineated its role in BC cell growth, invasion, and metastasis. The mechanical verification of circRREB1's interaction with GNB4 was established through RNA pull-down, mass spectrometry, Western blot analysis, RNA immunoprecipitation assays (RIP), fluorescence ISH (FISH), and rescue experiments. We found that circRREB1 exhibited significant upregulation in BC tissues and cells, implicating its association with an unfavorable prognosis in BC patients. CircRREB1 knockdown elicited anti-proliferative, anti-migratory, anti-invasive, and pro-apoptotic effects in BC cells, whereas its upregulation exerted opposing influences. Follow-up mechanistic examinations suggested that circRREB1 might interact with GNB4 directly, inducing the activation of Erk1/2 signaling and driving BC progression. Our findings collectively indicate that the interplay of circRREB1 with GNB4 promotes Erk1/2 signaling, thereby fostering BC progression, and positioning circRREB1 as a candidate therapeutic target for intervention in BC.

Biological role and regulation of circular RNA as an emerging biomarker and potential therapeutic target for cancer

Circular RNAs (circRNAs) are a unique family of endogenous RNAs devoid of 3' poly-A tails and 5' end caps. These single-stranded circRNAs, found in the cytoplasm, are synthesized via back-splicing mechanisms, merging introns, exons, or both, resulting in covalently closed circular loops. They are profusely expressed across the eukaryotic transcriptome and offer heightened stability against exonuclease RNase R compared to linear RNA counterparts. This review endeavors to provide a comprehensive overview of circRNAs' characteristics, biogenesis, and mechanisms of action. Furthermore, aimed to shed light on the potential of circRNAs as significant biomarkers in various cancer types. It has been performed an exhaustive literature review, drawing on recent studies and findings related to circRNA characteristics, synthesis, function, evaluation techniques, and their associations with oncogenesis. CircRNAs are intricately associated with tumor progression and development. Their multifaceted roles encompass gene regulation through the sponging of proteins and microRNAs, controlling transcription and splicing, interacting with RNA binding proteins (RBPs), and facilitating gene translation. Due to these varied roles, circRNAs have become a focal point in tumor pathology investigations, given their promising potential as both biomarkers and therapeutic agents. CircRNAs, due to their unique biogenesis and multifunctionality, hold immense promise in the realm of oncology. Their stability, widespread expression, and intricate involvement in gene regulation underscore their prospective utility as reliable biomarkers and therapeutic targets in cancer. As our understanding of circRNAs deepens, advanced techniques for their detection, evaluation, and manipulation will likely emerge. These advancements might catalyze the translation of circRNA-based diagnostics and therapeutics into clinical practice, potentially revolutionizing cancer care and prognosis.

Circ_0001944 depletion inhibits glycolysis and esophageal cancer progression by binding to miR-338-5p to reduce PDK1 expression

Circular RNA (circRNA) plays multiple roles in the development of esophageal cancer (EC). Herein, we investigate the function of circ_0001944 in EC progression and the related mechanism. Expression of circ_0001944, microRNA-338-5p (miR-338-5p), pyruvate dehydrogenase kinase 1 (PDK1), E-cadherin and N-cadherin was analyzed by quantitative real-time polymerase chain reaction, Western blotting or immunohistochemistry assay. Cell viability, proliferation, apoptosis, invasion and migration were investigated by cell counting kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU), flow cytometry, transwell invasion and wound-healing assays, respectively. Glucose consumption was detected by Glucose Assay Kit. Lactate production was analyzed by Lactate Assay Kit. ATP/ADP ratio was determined by ADP/ATP ratio Assay Kit. The associations among circ_0001944, miR-338-5p and PDK1 were identified by dual-luciferase reporter and RNA pull-down assays. Xenograft mouse model assay was used to explore the role of circ_0001944 on tumor tumorigenesis in vivo. Circ_0001944 and PDK1 expression were significantly upregulated, while miR-338-5p was downregulated in EC tissues and cells in contrast with normal esophageal tissues and cells. Circ_0001944 knockdown inhibited EC cell proliferation, invasion, migration and glycolysis but induced apoptosis. Meanwhile, circ_0001944 depletion suppressed tumor tumorigenesis in vivo. Mechanistically, circ_0001944 bound to miR-338-5p, and miR-338-5p targeted PDK1. In addition, miR-338-5p inhibitors attenuated circ_0001944 depletion-induced effects in EC cells. The regulation of miR-338-5p on EC progression involved the downregulation of PDK1. Further, circ_0001944 controlled PDK1 expression through miR-338-5p. Circ_0001944 knockdown inhibited EC development and glycolysis by regulating the miR-338-5p/PDK1 pathway, providing a promising target for EC therapy.

Circular RNA 0016142 Knockdown Induces Ferroptosis in Hepatocellular Carcinoma Cells via Modulation of the MicroRNA-188-3p/Glutathione Peroxidase 4 Axis

Hepatocellular carcinoma (HCC) has high incidence and mortality rates, and it is characterized by invasiveness, poor prognosis, and limited treatment opportunities. The objective of our research was to assess the role of circ_0016142 in HCC. The ferroptosis inducer RSL3 and the iron chelator deferoxamine were used to treat cells to induce or inhibit ferroptosis, respectively, and cell viability and proliferation were assessed in Hep3B and HA22T cells by CCK8 and EdU assays, respectively. ROS, MDA, GSH, and Fe2+ levels were determined using commercial kits. RT-qPCR and western blotting were performed to determine the relative expression levels of entities of interest. Dual-luciferase reporter and RNA pull-down assays were performed to assess the relationship between circ_0016142/GPX4 and miR-188-3p. The results showed that circ_0016142/GPX4 was overexpressed, whereas miR-188-3p was downregulated in HCC. Circ_0016142 silencing reduced cell proliferation and GSH levels and increased ROS, MDA, and Fe2+ levels in HCC cells, and this was reversed by the miR-188-3p inhibitor. GPX4-overexpression abolished the effect of miR-188-3p mimic in HCC cells. In conclusion, circ_0016142 silencing suppressed HCC cell proliferation by inducing ferroptosis via the miR-188-3p/GPX4 axis.

The Circular RNA circFOXK2 Enhances the Tumorigenesis of Non-Small Cell Lung Cancer Through the miR-149-3p/IL-6 Axis

Circular RNAs (circRNAs) are the non-coding types of RNAs and are thoughts to be linked with human cancer progression. circFOXK2 is believed to be associated with cancers, however, the molecular mechanisms of circFOXK2 in non-small cell lung cancer (NSCLC) are still unclear. Here we firstly reported that circFOXK2 enhances the tumorigenesis of NSCLC through the miR-149-3p/IL-6 axis. The expression of circFOXK2, microRNA-149-3p (miR-149-3p) and IL-6 were assessed by qRT-PCR and western blot. Transwell, colony formation, wound healing, and CCK-8 assays were used to elucidate NSCLC cells' proliferation, migration, and invasion. MiR-149-3p interaction with circFOXK2 was confirmed by dual-luciferase reporter gene assay (DLRGA). Furthermore, the biological effect of circFOXK2 on NSCLC progression was detected by tumor xenograft assay. CircFOXK2 were upregulated in NSCLC tissues and cells, miR-149-3p were downregulated in NSCLC tissues and cells. In addition, circFOXK2 stimulated NSCLC cell proliferation, migration and invasion in vitro. Mechanical analysis indicated that circFOXK2 modulated IL-6 via miR-149-3p sponging. Furthermore, circFOXK2 overexpression promoted tumor growth in vivo. Overall, this research verified that circFOXK2 enhances the tumorigenesis of NSCLC through the miR-149-3p/IL-6 axis.

Circ_0020123 promotes non-small cell lung cancer progression via miR-146a-5p mediated regulation of EIF4G2 expression

BACKGROUND

Circular RNAs (circRNAs) have been reported to be involved in the initiation and development of cancers. The aim of this study was to determine the role of a circRNA, circ_0020123, in the development of non-small cell lung cancer (NSCLC).

METHODS

The expression of circ_0020123, microRNA-146a-5p (miR-146a-5p), and eukaryotic translation initiation factor 4 gamma 2 (EIF4G2) mRNA was detected by quantitative real-time PCR (qPCR). Western blot was used to determine the protein levels of cyclin D1, Bax, MMP-9, and EIF4G2. Cell proliferation was assessed by cell counting kit-8 (CCK-8) assay and colony formation assay. Flow cytometry assay was applied to determine cell cycle apoptosis. Cell migration and invasion were assessed using transwell assay. The potential relationship between miR-146a-5p and circ_0020123 or EIF4G2 was ascertained by dual-luciferase reporter assay and RIP assay. The role of circ_0020123 in vivo was explored by xenograft assay.

RESULTS

Circ_0020123 was upregulated in NSCLC, and circ_0020123 knockdown repressed proliferation, migration, and invasion of NSCLC cells. Circ_0020123 targeted miR-146a-5p, and miR-146a-5p inhibitor reversed the effects of circ_0020123 knockdown on NSCLC cells. In addition, miR-146a-5p suppressed cell proliferation, migration, and invasion by targeting EIF4G2. Moreover, the antitumor role of circ_0020123 knockdown was verified in vivo.

CONCLUSION

Knockdown of circ_0020123 inhibited NSCLC cell progression and tumor growth by targeting the miR-146a-5p/EIF4G2 axis.

Non-coding RNAs in gynecologic cancer

The term "gynecologic cancer" pertains to neoplasms impacting the reproductive tissues and organs of women encompassing the endometrium, vagina, cervix, uterus, vulva, and ovaries. The progression of gynecologic cancer is linked to various molecular mechanisms. Historically, cancer research primarily focused on protein-coding genes. However, recent years have unveiled the involvement of non-coding RNAs (ncRNAs), including microRNAs, long non-coding RNAs (LncRNAs), and circular RNAs, in modulating cellular functions within gynecological cancer. Substantial evidence suggests that ncRNAs may wield a dual role in gynecological cancer, acting as either oncogenic or tumor-suppressive agents. Numerous clinical trials are presently investigating the roles of ncRNAs as biomarkers and therapeutic agents. These endeavors may introduce a fresh perspective on the diagnosis and treatment of gynecological cancer. In this overview, we highlight some of the ncRNAs associated with gynecological cancers.

Circ_MACF1 targets miR-421 to upregulate FMO2 to suppress paclitaxel resistance and malignant cellular behaviors in lung adenocarcinoma

BACKGROUND

Chemoresistance remains an enormous challenge in the treatment of lung adenocarcinoma (LADC). Circular RNAs (circRNAs) exhibit important regulation in tumor progression and chemoresistance. This research focused on exploring the regulatory function and mechanism of circ_MACF1 (has_circ_0011780) in paclitaxel (PTX) resistance in LADC.

METHODS

Circ_MACF1, miR-421 and flavin-containing monooxygenase 2 (FMO2) were determined by RT-qPCR. MTT was applied to detect IC50 of PTX. The proliferation analysis was performed using EdU and colony formation assay. Cell apoptosis and motility were examined using flow cytometry and transwell assay, respectively. Western blot was administered for protein detection. A dual-luciferase reporter assay was performed for confirming target interaction. PTX sensitivity in vivo was researched via xenograft tumor assay.

RESULTS

Expression of circ_MACF1 was decreased in PTX-resistant LADC tissues and cells. Circ_MACF1 overexpression reduced chemoresistance, proliferation, motility and accelerated apoptosis in PTX-resistant LADC cells. Circ_MACF1 targeted miR-421 and miR-421 upregulation reverted circ_MACF1-evoked effects. FMO2 served as a downstream target of miR-421 and circ_MACF1 sponged miR-421 to elevate the expression of FMO2. MiR-421 enhanced PTX resistance and LADC progression via targeting FMO2. FMO2 knockdown enhanced IC50 of PTX and cell proliferation. In vivo, circ_MACF1 elevated PTX sensitivity of LADC by mediating miR-421/FMO2 axis.

CONCLUSION

These findings elucidated that circ_MACF1 inhibited PTX resistance by absorbing miR-421 to upregulate FMO2 in LADC.

Depletion of circPDSS1 inhibits ITGA11 production to confer cisplatin sensitivity through miR-515-5p in gastric cancer

Chemoresistance limits cisplatin (DDP)-mediated treatment for gastric cancer (GC). Circular RNA (circRNA) acts an important role in chemoresistance. However, the underlying mechanism of circPDSS1 regulating DDP sensitivity in GC remains unclear. The expression patterns of circPDSS1, miR-515-5p and integrin subunit alpha 11 (ITGA11) were analyzed by qRT-PCR. Protein expression was checked by Western blotting analysis. Cell viability was investigated by 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation was evaluated by colony formation assay and 5-ethynyl-2'-deoxyuridine (EdU) assay. The analysis of cell apoptosis, migration and invasion was performed by flow cytometry analysis and transwell assays. Dual-luciferase reporter assay and RNA immunoprecipitation assay were conducted to identify the associations among circPDSS1, miR-515-5p and ITGA11. In vivo assay was implemented using a xenograft mouse model assay. CircPDSS1 and ITGA11 expression were significantly upregulated, whereas miR-515-5p was downregulated in DDP-resistant GC tissues and cells in comparison with controls. CircPDSS1 depletion reduced DDP resistance, cell proliferation, migration and invasion but induced cell apoptosis in DDP-resistant GC cells. CircPDSS1 directly bound to miR-515-5p. CircPDSS1-mediated actions were dependent on the regulation of miR-515-5p. Besides, miR-515-5p was associated with ITGA11, and circPDSS1 regulated ITGA11 expression by binding to miR-515-5p. Overexpression of miR-515-5p improved DDP sensitivity owing to the downregulation of ITGA11. Further, circPDSS1 mediated DDP sensitivity by regulating miR-515-5p and ITGA11 in vivo. CircPDSS1 conferred DDP resistance through the miR-515-5p/ITGA11 axis in GC cells.

The Glioblastoma CircularRNAome

Glioblastoma remains one of the most aggressive cancers of the brain, warranting new methods for early diagnosis and more efficient treatment options. Circular RNAs (circRNAs) are rather new entities with increased stability compared to their linear counterparts that interact with proteins and act as microRNA sponges, among other functions. Herein, we provide a critical overview of the recently described glioblastoma-related circRNAs in the literature, focusing on their roles on glioblastoma cancer cell proliferation, survival, migration, invasion and metastasis, metabolic reprogramming, and therapeutic resistance. The main roles of circRNAs in regulating cancer processes are due to their regulatory roles in essential oncogenic pathways, including MAPK, PI3K/AKT/mTOR, and Wnt, which are influenced by various circRNAs. The present work pictures the wide implication of circRNAs in glioblastoma, thus highlighting their potential as future biomarkers and therapeutic targets/agents.

Extracellular vesicles in gastric cancer: role of exosomal lncRNA and microRNA as diagnostic and therapeutic targets

Extracellular vesicles (EVs), including exosomes, play a crucial role in intercellular communication and have emerged as important mediators in the development and progression of gastric cancer. This review discusses the current understanding of the role of EVs, particularly exosomal lncRNA and microRNA, in gastric cancer and their potential as diagnostic and therapeutic targets. Exosomes are small membrane-bound particles secreted by both cancer cells and stromal cells within the tumor microenvironment. They contain various ncRNA and biomolecules, which can be transferred to recipient cells to promote tumor growth and metastasis. In this review, we highlighted the importance of exosomal lncRNA and microRNA in gastric cancer. Exosomal lncRNAs have been shown to regulate gene expression by interacting with transcription factors or chromatin-modifying enzymes, which regulate gene expression by binding to target mRNAs. We also discuss the potential use of exosomal lncRNAs and microRNAs as diagnostic biomarkers for gastric cancer. Exosomes can be isolated from various bodily fluids, including blood, urine, and saliva. They contain specific molecules that reflect the molecular characteristics of the tumor, making them promising candidates for non-invasive diagnostic tests. Finally, the potential of targeting exosomal lncRNAs and microRNAs as a therapeutic strategy for gastric cancer were reviewed as wee. Inhibition of specific molecules within exosomes has been shown to suppress tumor growth and metastasis in preclinical models. In conclusion, this review article provides an overview of the current understanding of the role of exosomal lncRNA and microRNA in gastric cancer. We suggest that further research into these molecules could lead to new diagnostic tools and therapeutic strategies for this deadly disease.

Propofol synergizes with circAPBB2 to protect against hypoxia/reoxygenation-induced oxidative stress, inflammation, and apoptosis of human cardiomyocytes

BACKGROUND

Myocardial injury is the main manifestation of cardiovascular diseases, and previous studies have shown that propofol (PPF) regulates myocardial injury. However, the mechanism of PPF in regulating myocardial injury remains to be further explored. This work aims to analyze the effects of PPF on human cardiomyocyte injury and the underlying mechanism.

METHODS

The regulatory and functional role of PPF and circAPBB2 in human cardiomyocyte injury were analyzed using an in vitro hypoxia/reoxygenation (H/R) cell model, which was established by treating human cardiomyocytes (AC16 cells) with H/R. The study evaluated AC16 cell injury by analyzing cytotoxicity, oxidative stress, inflammation and apoptosis of H/R-induced AC16 cells. Quantitative real-time polymerase chain reaction was performed to detect circAPBB2, miR-18a-5p and dual specificity phosphatase 14 (DUSP14) expression. Protein expression was analyzed by Western blot analysis assay. Dual-luciferase reporter assay, RNA pull-down assay and RNA immunoprecipitation assay were performed to identify the associations among circAPBB2, miR-18a-5p and DUSP14. Cytotoxicity was investigated by cell counting kit-8 assay and lactate dehydrogenase activity detection kit. Oxidative stress was evaluated by cellular reactive oxygen species assay kit and superoxide dismutase activity assay kit. The production of tumor necrosis factor-α and interleukin-1β was evaluated by enzyme-linked immunosorbent assays.

RESULTS

The expression of circAPBB2 and DUSP14 was significantly decreased, while miR-18a-5p was increased in H/R-induced AC16 cells when compared with controls. H/R treatment-induced cytotoxicity, oxidative stress, inflammation and cell apoptosis were attenuated after circAPBB2 overexpression or PPF treatment, whereas these effects were restored by increasing miR-18a-5p expression. PPF treatment improved the inhibitory effect of ectopic circAPBB2 expression on H/R-induced cell injury. MiR-18a-5p silencing ameliorated H/R-induced AC16 damage by interacting with DUSP14. Mechanically, circAPBB2 acted as a miR-18a-5p sponge, and miR-18a-5p targeted DUSP14 in AC16 cells.

CONCLUSION

PPF synergized with circAPBB2 to protect AC16 cells against H/R-induced oxidative stress, inflammation and apoptosis through the miR-18a-5p/DUSP14 pathway.

Core fucosylation and its roles in gastrointestinal glycoimmunology

Glycosylation is a common post-translational modification in eukaryotic cells. It is involved in the production of many biologically active glycoproteins and the regulation of protein structure and function. Core fucosylation plays a vital role in the immune response. Most immune system molecules are core fucosylated glycoproteins such as complements, cluster differentiation antigens, immunoglobulins, cytokines, major histocompatibility complex molecules, adhesion molecules, and immune molecule synthesis-related transcription factors. These core fucosylated glycoproteins play important roles in antigen recognition and clearance, cell adhesion, lymphocyte activation, apoptosis, signal transduction, and endocytosis. Core fucosylation is dominated by fucosyltransferase 8 (Fut8), which catalyzes the addition of α-1,6-fucose to the innermost GlcNAc residue of N-glycans. Fut8 is involved in humoral, cellular, and mucosal immunity. Tumor immunology is associated with aberrant core fucosylation. Here, we summarize the roles and potential modulatory mechanisms of Fut8 in various immune processes of the gastrointestinal system.

Extracellular Vesicles Derived circSH3PXD2A Inhibits Chemoresistance of Small Cell Lung Cancer by miR-375-3p/YAP1

Introduction

Small cell lung cancer (SCLC) is a subtype of lung cancer with high malignancy and poor prognosis. Rapid acquisition of chemoresistance is one of the main reasons leading to clinical treatment failure of SCLC. Studies have indicated that circRNAs participate in multiple processes of tumor progression, including chemoresistance. However, the molecular mechanisms of circRNAs driving the chemoresistance of SCLC are not well specified.

Methods

The differentially expressed circRNAs were screened by transcriptome sequencing of chemoresistant and chemosensitive SCLC cells. The EVs of SCLC cells were isolated and identified by ultracentrifugation, Western blotting, transmission electron microscopy, nanoparticle tracking analysis and EVs uptake assays. The expression levels of circSH3PXD2A in serum and EVs of SCLC patients and healthy individuals were detected by qRT‒PCR. The characteristics of circSH3PXD2A were detected by Sanger sequencing, RNase R assay, nuclear-cytoplasmic fraction assay, and fluorescence in situ hybridization assay. The mechanisms of circSH3PXD2A inhibiting SCLC progression were studied by bioinformatics analysis, chemoresistance assay, proliferation assay, apoptosis assay, transwell assay, pull-down assay, luciferase reporting assay, and mouse xenograft assay.

Results

It was identified that the circSH3PXD2A was a prominently downregulated circRNA in chemoresistant SCLC cells. The expression level of circSH3PXD2A in EVs of SCLC patients was negatively associated with chemoresistance, and the combination of EVs-derived circSH3PXD2A and serum ProGRP (Progastrin-releasing peptide) levels had better indications for DDP-resistant SCLC patients. CircSH3PXD2A inhibited the chemoresistance, proliferation, migration, and invasion of SCLC cells through miR-375-3p/YAP1 axis in vivo and in vitro. SCLC cells cocultured with EVs secreted by circSH3PXD2A-overexpressing cells exhibited decreased chemoresistance and cell proliferation.

Conclusion

Our results manifest that EVs-derived circSH3PXD2A inhibits the chemoresistance of SCLC through miR-375-3p/YAP1 axis. Moreover, EVs-derived circSH3PXD2A may serve as a predictive biomarker for DDP-resistant SCLC patients.

Emerging role of miRNAs, lncRNAs, and circRNAs in pregnancy-associated diseases

ABSTRACT

Accumulating studies have demonstrated that non-coding RNAs (ncRNAs), functioning as important regulators of transcription and translation, are involved in the establishment and maintenance of pregnancy, especially the maternal immune adaptation process. The endometrial stromal cells (ESCs), trophoblast cells, and decidua immune cells that reside at the maternal-fetal interface are thought to play significant roles in normal pregnancy and pregnancy-associated diseases. Here, we reviewed the up-to-date evidence on how microRNA, long non-coding RNA, and circular RNA regulate ESCs, trophoblast cells, and immune cells and discussed the potential applications of these ncRNAs as diagnostic and therapeutic markers in pregnancy complications.

Circ_0000471 suppresses the progression of ovarian cancer through mediating mir-135b-5p/dusp5 axis

BACKGROUND

Ovarian cancer (OC) is a common gynecologic cancer with high incidence and mortality. We attempted to investigate the role of circular RNA_0000471 (circ_0000471) in OC progression and its associated mechanism.

METHODS

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot assay were conducted to measure RNA and protein expression, respectively. Cell proliferation was analyzed by Cell Counting Kit-8 (CCK8) assay, colony formation assay, and 5-Ethynyl-2'-deoxyuridine (EdU) assay. Cell apoptosis was assessed by flow cytometry. Cell migration and invasion were analyzed by wound healing assay and transwell assay, respectively. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were conducted to verify the target relationships. Xenograft tumor model was established to assess the role of circ_0000471 on tumor growth in vivo.

RESULTS

Circ_0000471 expression was down-regulated in OC tissues and cell lines. Circ_0000471 overexpression blocked the proliferation, migration, and invasion and triggered the apoptosis of OC cells. Circ_0000471 served as a molecular sponge for microRNA-135b-5p (miR-135b-5p), and circ_0000471 overexpression-mediated anti-tumor influences in OC cells were largely reversed by the overexpression of miR-135b-5p. Dual specificity phosphatase 5 (DUSP5) was a target of miR-135b-5p, and miR-135b-5p silencing-induced anti-tumor effects were largely counteracted by the interference of DUSP5. Circ_0000471 increased DUSP5 expression by sponging miR-135b-5p in OC cells. Circ_0000471 overexpression restrained the growth of xenograft tumors in vivo.

CONCLUSION

Overexpression of circ_0000471 inhibited OC development by targeting miR-135b-5p/DUSP5 axis, indicating that circ_0000471 may be a new potential target for OC treatment.

Circ_0004585 Facilitates Tumorigenesis of Colorectal Cancer Via Modulating the miR-338-3p/ZFX Axis and Activating the MEK/ERK Pathway

Background

Colorectal cancer (CRC) is a common malignant tumor in the digestive tract. Circular RNAs (circRNAs) have been identified as crucial regulators of tumorigenesis. However, the role and potential mechanism of circ_0004585 in CRC are poorly understood.

Methods

The expression of circ_0004585, microRNA-338-3p (miR-338-3p), and zinc finger protein X-linked (ZFX) was detected by quantitative real-time PCR and Western blot. Cell proliferation, cell cycle arrest, apoptosis, and angiogenesis were evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT), 5-Ethynyl-2'-deoxyuridine (EdU), flow cytometry and tube formation assays. Western blot assay was applied to detect the expression of epithelial-mesenchymal transition (EMT)-related proteins and MEK/ERK signaling pathway-related proteins. A xenograft model was used to analyze tumor growth in vivo. The targeted relationship between miR-338-3p and circ_0004585/ZFX was verified by a dual-luciferase reporter assay.

Results

Circ_0004585 and ZFX were up-regulated, while miR-338-3p was down-regulated in CRC tissues and cells. Silencing of circ_0004585 inhibited proliferation, angiogenesis, and EMT and triggered apoptosis in CRC cells. Consistently, circ_0004585 depletion blocked tumor growth in vivo. Circ_0004585 contributed to CRC cell development via sequestering miR-338-3p. Also, miR-338-3p hindered the malignant progression of CRC cells by targeting ZFX. Circ_0004585 activated MEK/ERK pathway via regulating ZFX.

Conclusion

Circ_0004585 facilitated CRC progression through modulating miR-338-3p/ZFX/MEK/ERK pathway, which might provide a potential therapeutic target for CRC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-022-00756-6.

RNA sequencing reveals CircRNA expression profiles in chicken embryo fibroblasts infected with velogenic Newcastle disease virus

Introduction

Newcastle disease virus (NDV) is an important avian pathogen prevalent worldwide; it has an extensive host range and seriously harms the poultry industry. Velogenic NDV strains exhibit high pathogenicity and mortality in chickens. Circular RNAs (circRNAs) are among the most abundant and conserved eukaryotic transcripts. They are part of the innate immunity and antiviral response. However, the relationship between circRNAs and NDV infection is unclear.

Methods

In this study, we used circRNA transcriptome sequencing to analyze the differences in circRNA expression profiles post velogenic NDV infection in chicken embryo fibroblasts (CEFs). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to reveal significant enrichment of differentially expressed (DE) circRNAs. The circRNA- miRNA-mRNA interaction networks were further predicted. Moreover, circ-EZH2 was selected to determine its effect on NDV infection in CEFs.

Results

NDV infection altered circRNA expression profiles in CEFs, and 86 significantly DE circRNAs were identified. GO and KEGG enrichment analyses revealed significant enrichment of DE circRNAs for metabolism-related pathways, such as lysine degradation, glutaminergic synapse, and alanine, aspartic-acid, and glutamic-acid metabolism. The circRNA- miRNA-mRNA interaction networks further demonstrated that CEFs might combat NDV infection by regulating metabolism through circRNA-targeted mRNAs and miRNAs. Furthermore, we verified that circ-EZH2 overexpression and knockdown inhibited and promoted NDV replication, respectively, indicating that circRNAs are involved in NDV replication.

Conclusions

These results demonstrate that CEFs exert antiviral responses by forming circRNAs, offering new insights into the mechanisms underlying NDV-host interactions.

Circ_0056618 enhances PRRG4 expression by competitively binding to miR-411-5p to promote the malignant progression of colorectal cancer

The purpose of this paper was to explore the role of circ_0056618 and associated mechanisms in colorectal cancer (CRC). The expression of circ_0056618, proline rich and Gla domain 4 (PRRG4) mRNA and miR-411-5p was measured by quantitative real-time PCR (qPCR).The protein levels of PRRG4 and epithelial-mesenchymal transition (EMT)-related markers were detected by western blot. Cell proliferation was assessed by cell counting kit-8, EdU, and colony formation assays. Cell migration and invasion were assessed by transwell assay. Cell apoptosis was detected by flow cytometry assay. The putative relationship between miR-411-5p and circ_0056618 or PRRG4 was verified by dual-luciferase reporter assay. The effects of circ_0056618 on tumor growth in vivo were determined by animal study. Circ_0056618 and PRRG4 was upregulated, while miR-411-5p was downregulated in CRC tumor tissues and cells. Circ_0056618 knockdown or PRRG4 knockdown inhibited CRC cell proliferation, migration/invasion, EMT, and survival. Circ_0056618 positively modulated PRRG4 expression by targeting miR-411-5p. MiR-411-5p absence or PRRG4 overexpression could rescue circ_0056618 knockdown-induced inhibition on proliferation, migration/invasion, and EMT in CRC cells. Animal assay showed circ_0056618 knockdown impeded tumor growth in vivo. Circ_0056618 promoted CRC growth and development by upregulating PRRG4 expression via competitively targeting miR-411-5p.

circ_0000376 knockdown suppresses non-small cell lung cancer cell tumor properties by the miR-545-3p/PDPK1 pathway

Non-small cell lung cancer (NSCLC) accounts for 80% of total lung cancers, which are the main killer of cancer-related death worldwide. Circular RNA (circRNA) has been found to modulate NSCLC development. However, the role of circ_0000376 in NSCLC development has been underreported. The present work showed that circ_0000376 and 3-phos-phoinositide-dependent protein kinase-1 (PDPK1) expression were dramatically increased, but miR-545-3p was decreased in NSCLC tissues and cells. circ_0000376 expression was closely associated with lymph node metastasis, tumor-node-metastasis stage, and tumor size of NSCLC patients. circ_0000376 knockdown repressed NSCLC cell proliferation, migration, invasion, and glutaminolysis but induced cell apoptosis. Additionally, miR-545-3p bound to circ_0000376, and circ_0000376 regulated cell phenotypes by associating with miR-545-3p. MiR-545-3p also participated in NSCLC cell proliferation, migration, invasion, apoptosis, and glutaminolysis by targeting PDPK1. Further, circ_0000376 absence repressed tumor formation in vivo. Collectively, circ_0000376 regulated NSCLC cell tumor properties by the miR-545-3p/PDPK1 axis, suggesting that circ_0000376 could be employed as a therapeutic target for NSCLC.

Non-Coding RNAs Regulating Mitochondrial Functions and the Oxidative Stress Response as Putative Targets against Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is an ever-increasing, insidious disease which reduces the quality of life of millions of elderly people around the world. AMD is characterised by damage to the retinal pigment epithelium (RPE) in the macula region of the retina. The origins of this multi-factorial disease are complex and still not fully understood. Oxidative stress and mitochondrial imbalance in the RPE are believed to be important factors in the development of AMD. In this review, the regulation of the mitochondrial function and antioxidant stress response by non-coding RNAs (ncRNAs), newly emerged epigenetic factors, is discussed. These molecules include microRNAs, long non-coding RNAs, and circular non-coding RNAs. They act mainly as mRNA suppressors, controllers of other ncRNAs, or by interacting with proteins. We include here examples of these RNA molecules which affect various mitochondrial processes and antioxidant signaling of the cell. As a future prospect, the possibility to manipulate these ncRNAs to strengthen mitochondrial and antioxidant response functions is discussed. Non-coding RNAs could be used as potential diagnostic markers for AMD, and in the future, also as therapeutic targets, either by suppressing or increasing their expression. In addition to AMD, it is possible that non-coding RNAs could be regulators in other oxidative stress-related degenerative diseases.

Circ_0060937 Contributes to the Development of Lung Cancer via Positively Regulating LAD1 Expression by Binding to miR-1304-5p

In view of the significance of circular RNA (circRNA) in multiple carcinogeneses, our study focused on circ_0060937 and investigated its function and molecular mechanism in lung cancer. Quantitative real-time PCR (qPCR) and western blot assays were applied for expression analysis of circ_0060937, miR-1304-5p, LAD1, and several marker proteins. Functional experiments, including colony formation assay, EdU assay, transwell analysis, sphere formation assay, and flow cytometry experiment, were conducted for cell behavior analysis. The putative binding relationship between circ_0060937 and miR-1304-5p was validated by dual-luciferase reporter experiment and pull-down analysis. Animal models were established to ascertain the role of circ_0060937. Upregulation of circ_0060937 was shown in lung cancer tissues and cell lines. Circ_0060937 downregulation repressed A549 and H1299 cell proliferative, migratory, invasive, and sphere formation abilities, and circ_0060937 absence also decelerated tumorigenesis in animal models. Circ_0060937 bound to miR-1304-5p to positively regulate LAD1 expression. The inhibitory effects of circ_0060937 absence on A549 and H1299 cell malignant behaviors were largely reversed by miR-1304-5p inhibition or LAD1 overexpression, hinting that circ_0060937 affected lung cancer progression via modulating the miR-1304-5p/LAD1 axis. Circ_0060937 downregulation decreased the expression of LAD1 by releasing miR-1304-5p to effectively repress lung cancer cell growth and in vivo tumorigenesis.

Knockdown of Circ_0003506 Impedes Radioresistance, Cell Growth, Migration and Invasion in Gastric Cancer

BACKGROUND

Radioresistance is a major obstacle for clinical treatment of gastric cancer (GC). has_circ_0003506 (circ_0003506) was reported as an oncogenic factor in GC, but its effect on radioresistant GC is unclear.

AIMS

This study aimed to explore the role of circ_0003506 in radioresistance and regulatory mechanism.

METHODS

The expression detection was performed by real-time polymerase chain reaction. Cell survival was analyzed by colony formation assay. Cell proliferation was measured by Cell Counting Kit-8 assay and colony formation assay. Cell migration and invasion were examined using transwell assay. Cell apoptosis was assessed by flow cytometry. The target binding was confirmed via dual-luciferase reporter assay. The protein level was determined through western blot. Animal assay was performed for the functional exploration of circ_0003506 on radiosensitivity in vivo.

RESULTS

Circ_0003506 was upregulated in radioresistant GC cells. Downregulation of circ_0003506 inhibited radioresistance to repress proliferation, migration and invasion but increase apoptosis in radioresistant GC cells. Circ_0003506 was a sponge of miR-1256. The effects of si-circ_0003506 on radioresistant GC cells were reverted by miR-1256 inhibitor. MiR-1256 suppressed tumor progression in radioresistant GC cells by downregulating bone morphogenetic protein type 2 receptor. Circ_0003506 regulated the level of bone morphogenetic protein type 2 receptor by targeting miR-1256. Downregulating circ_0003506 increased radiosensitivity of GC in vivo via regulating miR-1256 and bone morphogenetic protein type 2 receptor.

CONCLUSION

Knockdown of circ_0003506 suppressed radioresistance in GC through the regulation of miR-1256/bone morphogenetic protein type 2 receptor axis. Circ_0003506 might be a therapeutic target in radiotherapy of GC.

Ferroptosis-associated circular RNAs: Opportunities and challenges in the diagnosis and treatment of cancer

Ferroptosis is an emerging form of non-apoptotic regulated cell death which is different from cell death mechanisms such as autophagy, apoptosis and necrosis. It is characterized by iron-dependent lipid peroxide accumulation. Circular RNA (circRNA) is a newly studied evolutionarily conserved type of non-coding RNA with a covalent closed-loop structure. It exhibits universality, conservatism, stability and particularity. At present, the functions that have been studied and found include microRNA sponge, protein scaffold, transcription regulation, translation and production of peptides, etc. CircRNA can be used as a biomarker of tumors and is a hotspot in RNA biology research. Studies have shown that ferroptosis can participate in tumor regulation through the circRNA molecular pathway and then affect cancer progression, which may become a direction of cancer diagnosis and treatment in the future. This paper reviews the molecular biological mechanism of ferroptosis and the role of circular RNA in tumors and summarizes the circRNA related to ferroptosis in tumors, which may inspire research prospects for the precise prevention and treatment of cancer in the future.

Circular RNAs: pivotal role in the leukemogenesis and novel indicators for the diagnosis and prognosis of acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive hematological malignancy and affected patients have poor overall survival (OS) rates. Circular RNAs (circRNAs) are a novel class of non-coding RNAs (ncRNAs) with a unique loop structure. In recent years, with the development of high-throughput RNA sequencing, many circRNAs have been identified exhibiting either up-regulation or down-regulation in AML patients compared with healthy controls. Recent studies have reported that circRNAs regulate leukemia cell proliferation, stemness, and apoptosis, both positively and negatively. Additionally, circRNAs could be promising biomarkers and therapeutic targets in AML. In this study, we present a comprehensive review of the regulatory roles and potentials of a number of dysregulated circRNAs in AML.

Circular RNA 0000157 depletion protects human bronchial epithelioid cells from cigarette smoke extract-induced human bronchial epithelioid cell injury through the microRNA-149-5p/bromodomain containing 4 pathway

BACKGROUND

Circular RNA (circRNA) has been reported to regulate respiratory diseases. In the study, we aimed to elucidate the role of circ_0000157 in smoke-related chronic obstructive pulmonary disease (COPD) and the inner mechanism.

METHODS

COPD-like cell injury was induced by treating human bronchial epithelioid cells (16HBE) with cigarette smoke extract (CSE). The expression of circ_0000157, miR-149-5p, bromodomain containing 4 (BRD4), BCL2-associated x protein (Bax) and B-cell lymphoma-2 (Bcl-2) was analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) or Western blotting. Enzyme-linked immunosorbent assay was performed to detect interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) levels. Malondialdehyde (MDA) production was detected by a lipid peroxidation MDA assay kit. Superoxide dismutase (SOD) activity was analyzed by a SOD activity assay kit.

RESULTS

Circ_0000157 and BRD4 expression were upregulated, while miR-149-5p expression was downregulated in the blood of smokers with COPD and CSE-induced 16HBE cells compared with control groups. CSE treatment inhibited 16HBE cell proliferation and induced cell apoptosis, inflammation, and oxidative stress; however, these effects were remitted when circ_0000157 expression was decreased. In addition, circ_0000157 acted as a miR-149-5p sponge and regulated CSE-caused 16HBE cell damage by targeting miR-149-5p. The overexpression of BRD4, a target gene of miR-149-5p, attenuated the inhibitory effects of miR-149-5p introduction on CSE-induced cell damage. Further, circ_0000157 modulated BRD4 expression by associating with miR-149-5p in CSE-treated 16HBE cells.

CONCLUSION

Circ_0000157 knockdown ameliorated CSE-caused 16HBE cell damage by targeting the miR-149-5p/BRD4 pathway, providing a potential therapeutic strategy for clinic intervention in COPD.

Chromosomally Unstable Gastric Cancers Overexpressing Claudin-6 Disclose Cross-Talk between HNF1A and HNF4A, and Upregulated Cholesterol Metabolism

(1) Abnormally increased expression of claudin-6 in gastric cancer is considered a prognostic marker of the chromosomal unstable molecular subtype. However, a detailed molecular profile analysis of differentially expressed genes and affected pathways associated with claudin-6 increased (Cldn6^high) expression has not been assessed. (2) The TCGA Stomach Adenocarcinoma Pan-Cancer Atlas Data was evaluated using Cytoscape's Gene Mania, MCODE, and Cytohubba bioinformatic software. (3) 96.88% of Cldn6^high gastric cancer tumors belonging to the chromosomal unstable molecular subtype are associated with a worse prognosis. Cldn6expression coincided with higher mutations in TP53, MIEN1, STARD3, PGAP3, and CCNE1 genes compared to Cldn6^low expression. In Cldn6^high cancers, 1316 genes were highly expressed. Cholesterol metabolism was the most affected pathway as APOA1, APOA2, APOH, APOC2, APOC3, APOB-100, LDL receptor-related protein 1/2, Sterol O-acyltransferase, STARD3, MAGEA-2, -3, -4, -6, -9B, and -12 genes were overexpressed in Cldn6^high gastric cancers; interestingly, APOA2 and MAGEA9b were identified as top hub genes. Functional enrichment of DEGs linked HNF-4α and HNF-1α genes as highly expressed in Cldn6^high gastric cancer. (4) Our results suggest that APOA2 and MAGEA9b could be considered as prognostic markers for Cldn6^high gastric cancers.

Circular RNA hsa_circ_0023404 promotes the proliferation, migration and invasion in endometrial cancer cells through regulating miR-217/MAPK1 axis

Background

Emerging studies indicated that circular RNA hsa_circ_ 0023404 and its target miR-217/MARK1 axis play a critical role in cancer progression such as non-small cell lung cancer and cervical cancer. However, the role of hsa_circ_0023404/miR-217/MARK1 involved in endometrial cancer (EC) was not investigated yet. The aim of this study is to investigate the functions of hsa_circ_0023404 in endometrial cancer (EC) and the potential molecular mechanism.

Methods

We used RT-qPCR and Western blot approach to detect the expressed levels of related genes in EC cell lines. Transfected siRNAs were applied to knockdown the level of related mRNA in cells. Cell proliferation by CCK-8 assay and colony formation assay were applied to detect cell proliferation. Transwell migration and invasion assay was for detecting the migration and invasion of the cells.

Results

RT-qPCR showed that the levels of hsa_circ_0023404 and MARK1 mRNA were upregulated, but mirR-217 was decreased in three endometrial cancer cell lines. Knockdown of hsa_circ_0023404 by siRNA markedly increased the level of miR-217 and reduced the proliferation of the Ishikawa cells. It also inhibited the cell migration and invasion. Anti-miR-217 can reverse the promoted proliferation, migrations and invasion of Ishikawa cells mediated by si-circ_0023404. si-MARK1 restored the inhibited cell proliferation, migration and invasion of the co-transfected Ishikawa cells with si- circ_0023404 and anti-miR-217.

Conclusion

hsa_circ_0023404 exerts a tumor-promoting role in endometrial cancer by regulating miR-217/MARK1 axis. hsa_circ_0023404 inhibit miR-217 as sponge which inhibit endometrial cancer cell growth and metastasis. MARK1 is downstream target of miR217 and upregulated by hsa_circ_ 0023404/miR-217 axis and involved in the endometrial cancer progression.

The comprehensive detection of miRNA and circRNA in the regulation of intramuscular and subcutaneous adipose tissue of Laiwu pig

circRNAs, as miRNA sponges, participate in many important biological processes. However, it remains unclear whether circRNAs can regulate lipid metabolism. This study aimed to explore the competing endogenouse RNA (ceRNA) regulatory network that affects the difference between intramuscular fat (IMF) and subcutaneous fat (SCF) deposition, and to screen key circRNAs and their regulatory genes. In this experiment, we identified 265 differentially expressed circRNAs, of which 187 up-regulated circRNA and 78 down-regulated circRNA in IMF. Subsequently, we annotated the function of DEcircRNA's host genes, and found that DEcircRNA's host genes were mainly involved in GO terms (including cellular response to fatty acids, lysophosphatidic acid acyltransferase activity, R-SMAD binding, etc.) and signaling pathways (fatty acid biosynthesis, Citrate cycle, TGF- β Signal pathway) related to adipogenesis, differentiation and lipid metabolism. By constructing a circRNA-miRNA network, we screened out DEcircRNA that can competitively bind to more miRNAs as key circRNAs (circRNA_06424 and circRNA_08840). Through the functional annotation of indirect target genes and protein network analysis, we found that circRNA_06424 affects the expression of PPARD, MMP9, UBA7 and other indirect target genes by competitively binding to miRNAs such as ssc-miR-339-5p, ssc-miR-744 and ssc-miR-328, and participates in PPAR signaling pathway, Wnt signaling pathway, unsaturated fatty acid and other signaling pathways, resulting in the difference of fat deposition between IMF and SCF. This study provide a theoretical basis for further research investigating the differences of lipid metabolism in different adipose tissues, providing potential therapeutic targets for ectopic fat deposition and lipid metabolism diseases.

The importance of regulatory pathway mediated by Circ0001955 in colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) has become one of the most common cancers in recent years. Given the importance that non-coding RNAs have recently acquired in various diseases including cancers, we decided to design this study to evaluate the expression levels of circ0001955/miR-145-5p/ONECUT2 axis in CRC.

METHODS

After bioinformatics analysis of GEO datasets related to CRC, a putative circ0001955/ miR-145-5p/ ONECUT2 pathway was assumed. Then, the expression levels of these genes were measured in 50 CRC samples and adjacent tissues by qRT- PCR. Also, correlation coefficients, receiver operating characteristic (ROC) curves, and correlation between circ0001955 levels with clinicopathological parameters of patients were analyzed.

RESULTS

Circ0001955 and ONECUT2 were considerably up-regulated, while the expression level of miR-145-5p was decreased in CRC samples compared with adjacent tissues (p < 0.05). Moreover, statistically significant correlations were observed between expression levels of circ0001955, miR-145-5p, and ONECUT2. We did not find any significant correlation between circ0001955 expression and clinicopathological parameters.

CONCLUSION

Our study showed that circ0001955 is dysregulated in CRC. This finding can open a new window for researchers for a better understanding of the potential pathways involved in CRC pathogenesis and, consequently, to find new treatment pathways.

CircPVT1 facilitates the progression of oral squamous cell carcinoma by regulating miR-143-3p/SLC7A11 axis through MAPK signaling pathway

Oral squamous cell carcinoma (OSCC) is a common malignant tumor occurring in the oral cavity. Circular RNAs (circRNAs) play a crucial regulatory role in many cancers. This study aimed to investigate the function of circRNA plasmacytoma variant translocation 1 (PVT1) (circPVT1) in OSCC and its potential mechanism. The levels of circPVT1, solute carrier family 7 member 11 (SLC7A11), and microRNA-143-3p (miR-143-3p) were examined by quantitative real-time PCR (qRT-PCR) or western blot assay. Cell proliferation, apoptosis, migration, and invasion were evaluated by Cell Counting Kit-8 (CCK-8), colony formation assay, flow cytometry, and transwell assay. The levels of apoptosis and proliferation-related proteins were examined by western blot. The targeting relationship between miR-143-3p and circPVT1 or SLC7A11 was verified by dual-luciferase reporter, RNA immunoprecipitation (RIP), and RNA pull-down assays. The levels of mitogen-activated protein kinase (MAPK) pathway-related proteins were measured by western blot. Xenograft assay was used to assess tumor growth in vivo. CircPVT1 and SLC7A11 were upregulated, while miR-143-3p was downregulated in OSCC tissues and cells. Silencing of circPVT1 or SLC7A11 suppressed proliferation, migration, and invasion and promoted apoptosis in OSCC cells. CircPVT1 upregulated SLC7A11 expression via sponging miR-143-3p. SLC7A11 upregulation alleviated the effect of circPVT1 knockdown on OSCC cell progression. Besides, circPVT1 modulated MAPK signaling pathway by regulating miR-143-3p. Moreover, circPVT1 knockdown inhibited tumor growth in vivo. Knockdown of circPVT1 impeded OSCC progression via the miR-143-3p/SLC7A11 axis through MAPK signaling pathway.

circKLHL24 Blocks Breast Cancer Development by Regulating the miR-1204/ALX4 Network

Background: Breast cancer is a major challenge affecting women's survival. Circular RNAs have been demonstrated to be vital regulators in the pathogenesis of human cancers. The authors' objective was to determine the functional role and mechanism of circKLHL24 in breast cancer development. Materials and Methods: The expression of circKLHL24, miR-1204, and aristaless-like 4 (ALX4) mRNA was measured using quantitative real-time polymerase chain reaction. The effects on cell viability, proliferation, migration/invasion, and glycolysis were identified using the Cell Counting Kit-8 (CCK-8) assay, colony formation assay, Transwell assay, and glycolysis stress test, respectively. For glycolysis progression analysis, glucose consumption and lactate production were assessed using corresponding kits, and the expression of glycolysis-related proteins was detected by Western blot. The putative interactions between miR-1204 and circKLHL24 or ALX4 were validated by dual-luciferase reporter assay or RNA pull-down assay. The expression of ALX4 at the protein level was detected by Western blot. Animal study was performed to clarify the role of circKLHL24 in vivo. Results: circKLHL24 and ALX4 were downregulated, while miR-1204 was upregulated in breast cancer tissues and cells. circKLHL24 overexpression blocked cell viability, colony formation, migration/invasion, and glycolysis progression. circKLHL24 competitively targeted miR-1204, and miR-1204 reintroduction reversed the effects of circKLHL24 restoration. miR-1204 bound to ALX4, and circKLHL24 sponged miR-1204 to upregulate ALX4. Cell viability, colony formation, migration/invasion, and glycolysis progression suppressed by miR-1204 deficiency were recovered by ALX4 knockdown. Besides, circKLHL24 blocked tumor growth in vivo by regulating miR-1204 and ALX4. Conclusions: circKLHL24 blocked the progression of breast cancer by activating ALX4 through targeting miR-1204, which might be a novel perspective to understand the pathogenesis of breast cancer.

The role of CircRNA/miRNA/mRNA axis in breast cancer drug resistance

Multidrug resistance is one of the major obstacles in the treatment of cancers. This undesirable feature increases the mortality rate of cancers, including breast cancer. Circular RNA (CircRNA)/microRNA (miRNA)/messenger RNA (mRNA) is one of the important axes with major roles in the promotion and resistance of breast cancer. This heterogeneous pathway includes mRNA of oncogenes and tumor suppressors, which are controlled by miRNAs and CircRNAs. Unfortunately, this network could be easily deregulated, resulting in drug resistance and tumor development. Therefore, understanding these dysregulations may thus help to identify effective therapeutic targets. On this basis, we try to review the latest findings in the field, which could help us to better comprehend this significant axis in breast cancer.

Genome-Wide Expression Profiling and Networking Reveals an Imperative Role of IMF-Associated Novel CircRNAs as ceRNA in Pigs

Intramuscular fat (IMF) deposition is a biological process that has a strong impact on the nutritional and sensorial properties of meat, with relevant consequences on human health. Pork loins determine the effects of marbling on the sensory attributes and meat quality properties, which differ among various pig breeds. This study explores the crosstalk of non-coding RNAs with mRNAs and analyzes the potential pathogenic role of IMF-associated competing endogenous RNA (ceRNA) in IMF tissues, which offer a framework for the functional validation of key/potential genes. A high-throughput whole-genome transcriptome analysis of IMF tissues from longissimus dorsi muscles of Large White (D_JN) and Laiwu (L_JN) pigs resulted in the identification of 283 differentially expressed circRNAs (DECs), including two key circRNAs (circRNA-23437, circRNA-08840) with potential binding sites for multiple miRNAs regulating the whole network. The potential ceRNA mechanism identified the DEC target miRNAs-mRNAs involved in lipid metabolism, fat deposition, meat quality, and metabolic syndrome via the circRNA-miRNA-mRNA network, concluding that ssc-mir-370 is the most important target miRNA shared by both key circRNAs. TGM2, SLC5A6, ECI1, FASN, PER1, SLC25A34, SOD1, and COL5A3 were identified as hub genes through an intensive protein-protein interaction (PPI) network analysis of target genes acquired from the ceRNA regulatory network. Functional enrichments, pathway examinations, and qRT-PCR analyses infer their implications in fat/cholesterol metabolism, insulin secretion, and fatty acid biosynthesis. Here, circRNAs and miRNA sequencing accompanied by computational techniques were performed to analyze their expressions in IMF tissues from the longissimus dorsi muscles of two pig breeds. Their target gene evolutionary trajectories, expression profiling, functional enrichments, subcellular localizations, and structural advances with high-throughput protein modeling, following genomic organizations, will provide new insights into the underlying molecular mechanisms of adipocyte differentiation and IMF deposition and a much-needed qualitative framework for future research to improve meat quality and its role as a biomarker to treat lipid metabolic syndromes.

Hsa_circ_0001020 Serves as a Potential Biomarker for Gastric Cancer Screening and Prognosis

Circular RNAs (circRNAs) are an intriguing class of RNAs with covalently closed-loop structures. With characteristics of high stability and disease-specific expression, circRNAs are emerging as ideal targets for cancer therapy. However, the screening utility and clinical value of circRNAs in gastric cancer (GC) remain largely elusive. We detected levels of hsa_circ_0001020 in cell lines and tissue and plasma samples and investigated its clinicopathological correlations. Kaplan-Meier survival curves and regression analyses were used to analyze its prognostic value. Receiver operating characteristic curves and biomarker combinations were examined to verify its screening value. Bioinformatics analysis was also performed to predict potential biological functions. Our tests found that hsa_circ_0001020 was significantly upregulated in GC cell lines, GC tissue samples, and even in plasma. High hsa_circ_0001020 expression levels in GC tissues were significantly associated with distal metastasis and blood carbohydrate antigen 19-9 (CA19-9). GC patients with high hsa_circ_0001020 had a lower overall survival and disease-free survival time than the low levels. Regression analysis suggested that the level of hsa_circ_0001020 expression was an independent prognostic factor for survival time. As a biomarker for GC, hsa_circ_0001020 showed a superior AUC, sensitivity, and specificity than carcinoembryonic antigen and CA19-9, and was suitable for combination with clinical tumor biomarkers. Bioinformatics analysis provided valuable clues for the possible oncogenic pathways of GC, such as the FoxO and p53 signaling pathways. In conclusion, our study found that hsa_circ_0001020 in GC could be a reliable biomarker to screen for GC and predict prognosis.

Circ_0005714/miR-223-3p/ADAM9 regulatory axis affects proliferation, migration, invasion, and angiopoiesis in trophoblast cells

BACKGROUND

Circular RNAs (circRNAs) have critical roles in various types of diseases, including preeclampsia (PE). Circ_0005714 function in PE was explored in this study.

METHODS

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was performed for level analysis of circ_0005714, micoRNA-223-3p (miR-223-3p), and a disintegrin and metalloproteinase 9 (ADAM9). Cell Counting Kit-8 (CCK-8) and colony formation assays were used for cell viability and colony formation detection. Cell proliferation was determined by EdU assay. The determination of migration and invasion was conducted by wound healing assay and transwell assay. Tube formation assay was applied to assess angiopoiesis. Target binding analysis was performed by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Western blot was used for protein examination.

RESULTS

Circ_0005714 was highly expressed in PE placenta tissues. The expression promotion of circ_0005714 reduced proliferation, migration, invasion, and angiopoiesis in trophoblast cells. Furthermore, circ_0005714 acted as a molecular sponge for miR-223-3p and the effects of circ_0005714 on trophoblast cells were achieved by sponging miR-223-3p. Moreover, miR-223-3p could target ADAM9 and knockdown of ADAM9 reversed cell progression inhibition induced by miR-223-3p inhibitor. In addition, circ_0005714 upregulated the ADAM9 expression and inactivated the Wnt/β-catenin pathway through targeting miR-223-3p.

CONCLUSIONS

All results manifested that circ_0005714 retarded the progression of PE by mediating the miR-223-3p/ADAM9 signal network.

A new circular RNA-encoded protein BIRC6-236aa inhibits transmissible gastroenteritis virus (TGEV)-induced mitochondrial dysfunction

Transmissible gastroenteritis virus (TGEV), a member of the coronavirus family, is the pathogen responsible for transmissible gastroenteritis, which results in mitochondrial dysfunction in host cells. Previously, we identified 123 differentially expressed circular RNAs (cRNA)from the TGEV-infected porcine intestinal epithelial cell line jejunum 2 (IPEC-J2). Previous bioinformatics analysis suggested that, of these, circBIRC6 had the potential to regulate mitochondrial function. Furthermore, mitochondrial permeability transition, a key step in the process of mitochondrial dysfunction, is known to be caused by abnormal opening of mitochondrial permeability transition pores (mPTPs) regulated by the voltage-dependent anion-selective channel protein 1 (VDAC)–Cyclophilin D (CypD) complex. Therefore, in the present study, we investigated the effects of circBIRC6-2 on mitochondrial dysfunction and opening of mPTPs. We found that TGEV infection reduced circBIRC6-2 levels, which in turn reduced mitochondrial calcium (Ca²⁺) levels, the decrease of mitochondrial membrane potential, and opening of mPTPs. In addition, we also identified ORFs and internal ribosomal entrance sites within the circBIRC6-2 RNA. We demonstrate circBIRC6-2 encodes a novel protein, BIRC6-236aa, which we show inhibits TGEV-induced opening of mPTPs during TGEV infection. Mechanistically, we identified an interaction between BIRC6-236aa and VDAC1, suggesting that BIRC6-236aa destabilizes the VDAC1–CypD complex. Taken together, the results suggest that the novel protein BIRC6-236aa encoded by cRNA circBIRC6-2 inhibits mPTP opening and subsequent mitochondrial dysfunction by interacting with VDAC1.

Prospect of exosomal circular RNAs in breast Cancer: presents and future

Implementing precision oncology for breast cancer (BC) is a critical method for improving patient outcomes, which relies on the use of reliable biomarkers to be effective and safe. exosomes represent a potential alternative for the diagnosis and therapy of BC, As a "liquid biopsy" and a novel source for biomarkers. Exosomes are nanoscale phospholipid bilayer vesicles released by most cells that contain a large payload of various RNA species that can alter recipient cell activity. Circular RNAs (circRNAs) were recently revealed as a looping subclass of competing endogenous noncoding RNAs (ceRNAs) capable of microRNA sponging to regulate gene expression. They provide critical regulatory functions in carcinogenesis, proliferation, invasion, metastasis, and treatment resistance, as well as cancer prognostic. However, there is still a major gap in our understanding of the role of circRNA in the advancement of BC. CircRNAs are abundant in exosomes, according to various studies, and exosomal circRNAs (exo-circRNAs) play a significant role in cancer biology. Exo-circRNAs can be picked up by nearby or distant cells, affecting many features of the target cells' pathophysiological states, thus boosting cell communication and tumor spread. In this review, we have briefly summarized the major properties and functions of exosomes. Then, we have focused on exo-circRNAs, discussing their potential roles in both driving and inhibiting BC, as well as for cancer diagnosis, prognosis, and monitoring.

Noncoding RNA-mediated macrophage and cancer cell crosstalk in hepatocellular carcinoma

The tumor microenvironment (TME) is a well-recognized system that plays an essential role in tumor initiation, development, and progression. Intense intercellular communication between tumor cells and other cells (especially macrophages) occurs in the TME and is mediated by cell-to-cell contact and/or soluble messengers. Emerging evidence indicates that noncoding RNAs (ncRNAs) are critical regulators of the relationship between cells within the TME. In this review, we provide an update on the regulation of ncRNAs (primarily micro RNAs [miRNAs], long ncRNAs [lncRNAs], and circular RNAs [circRNAs]) in the crosstalk between macrophages and tumor cells in hepatocellular carcinoma (HCC). These ncRNAs are derived from macrophages or tumor cells and act as oncogenes or tumor suppressors, contributing to tumor progression not only by regulating the physiological and pathological processes of tumor cells but also by controlling macrophage infiltration, activation, polarization, and function. Herein, we also explore the options available for clinical therapeutic strategies targeting crosstalk-related ncRNAs to treat HCC. A better understanding of the relationship between macrophages and tumor cells mediated by ncRNAs will uncover new diagnostic biomarkers and pharmacological targets in cancer.

Sevoflurane inhibits the malignant phenotypes of glioma through regulating miR-146b-5p/NFIB axis

PURPOSE

Sevoflurane is a common used inhaled anesthetic that was reported to regulate the progression of multiple cancers. Here, we aimed to investigate the function and regulatory mechanism underlying sevoflurane in glioma cells.

METHODS

A172 and U251 cells were treated with different concentrations of sevoflurane. Colony formation, EdU satining and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT), flow cytometry, and transwell assays were performed to evaluate cell proliferation, apoptosis, migration and invasion, respectively. Circ_VCAN, microRNA-146b-5p (miR-146b-5p) and nuclear factor I B (NFIB) expression levels were assessed by real-time quantitative PCR (RT-qPCR) or western blot. Bioinformatics analysis and dual-luciferase reporter assay were applied to evaluate the correlation between miR-146b-5p and circ_VCAN or NFIB. A xenograft glioma mice model was established to verify the effect of sevoflurane on tumor growth in vivo.

RESULTS

Sevoflurane (Sev) inhibited proliferation, migration, invasion, and elevated apoptosis of A172 and U251 cells. Sevoflurane treatment inhibited the expression of circ_VCAN and NFIB, but elevated the expression of miR-146b-5p in glioma cells. Overexpression of circ_VCAN alleviated the inhibition effects of sevoflurane on the malignant phenotypes of glioma in vitro and in vivo. Besides, miR-146b-5p is a target of circ_VCAN and negatively regulated NFIB expression. Overexpression of miR-146b-5p partly reversed the effects of circ_VCAN in Sev-treated glioma cells. Furthermore, miR-146b-5p deletion enhanced glioma progression in sevoflurane treated glioma cells by targeting NFIB. Moreover, circ_VCAN could upregulate NFIB expression by sponging miR-146b-5p in Sev-treated glioma cells.

CONCLUSION

Sevoflurane alleviated proliferation, migration and invasion, but enhanced apoptosis of glioma cells through regulating circ_VCAN/miR-146b-5p/NFIB axis.

Circ_0006790 carried by bone marrow mesenchymal stem cell-derived exosomes regulates S100A11 DNA methylation through binding to CBX7 in pancreatic ductal adenocarcinoma

Extracellular vesicles, particularly exosomes, play a vital role via their cargoes. Their potential in pancreatic ductal adenocarcinoma (PDAC), one of the leading causes of cancer-related mortality worldwide is attracting interests. However, the roles and underlying mechanisms of exosomal circular RNAs (circRNAs) in the development of PDAC remain unclear yet. We aimed to illuminate the mechanisms of exosomal hsa_circ_0006790 (thereafter termed circ_6790) released by exosomes (Exo) derived from bone marrow mesenchymal stem cell (BM-MSC) during immune escape in PDAC in this study. BM-MSC-derived Exo inhibited growth, metastasis, and immune escape in PDAC. Exo enhanced circ_6790 expression in PDAC cells. Knockdown of circ_6790 in Exo significantly attenuated the anti-tumor effect of Exo. Circ_6790 facilitated the nuclear translocation of chromobox 7 (CBX7). CBX7 increased the DNA methylation of S100A11 by recruiting DNA methyltransferases to its promoter region, thereby inhibiting the transcription of S100A11. Inhibition of CBX7 or overexpression of S100A11 annulled the inhibitory effects of Exo on PDAC growth, metastasis, and immune escape. In conclusion, our results suggest that MSC-derived exosomal circ_6790 could downregulate S100A11 in PDAC cells and hamper immune escape via CBX7-catalyzed DNA hypermethylation.

CircRNA protein tyrosine phosphatase receptor type a suppresses proliferation and induces apoptosis of lung adenocarcinoma cells via regulation of microRNA-582-3p

Circular RNAs (circRNAs) are associated with cancer progression. The present study aimed to examine the function of circRNA protein tyrosine phosphatase receptor type A (circRNA_PTPRA) in lung cancer cells and elucidate the underlying molecular mechanisms. The levels of circRNA_PTPRA and microRNA (miRNA/miR)-582-3p were measured in lung cancer tissue and cells using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Cell proliferation and apoptosis were evaluated using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry, respectively. The expression of cyclin D1, caspase-3, and cleaved caspase-3 was assessed via western blotting. The sites of circRNA_PTPRA/miR-582-3p interaction were identified using StarBase, and validated using a dual-luciferase reporter assay. We observed that circRNA_PTPRA levels were remarkably decreased, and miR-582-3p expression was up-regulated in lung cancer tissues and cells. circRNA_PTPRA directly interacts with miR-582-3p and downregulates miR-582-3p expression in lung cancer cells. Moreover, an miR-582-3p inhibitor decreased lung cancer cell proliferation and promoted apoptosis. The overexpression of circRNA_PTPRA decreased cell proliferation and increased apoptotic cell numbers, whereas miR-582-3p overexpression reversed these effects. These findings demonstrate that the up-regulation of circRNA_PTPRA significantly reduces lung cancer cell proliferation and induces apoptosis by regulating miR-582-3p expression.

The Emerging Roles of Circ-ABCB10 in Cancer

Circular RNAs (circRNAs) are non-coding RNAs (ncRNAs) without 5′ caps and 3′ tails, which are formed from precursor mRNAs (pre-mRNAs) that are inversely back-spliced by exons. CircRNAs are characterized by a covalently closed circular structure and are abundantly expressed in eukaryotic cells. With the development of RNA-sequencing, it was discovered that circRNAs play important roles in the regulation of numerous human genes and are related to the occurrence, development, and prognosis of diseases. Studies in various cancers have revealed that circRNAs have both positive and negative effects on the occurrence and development of tumors. Circ-ABCB10, a circular RNA originating from exons of ABCB10 located on chromosome 1q42, has been proven to play an important role in different types of cancers. Here, we report the primary findings of recent research studies by many contributors about the roles of circ-ABCB10 in cancer and clearly formulate its influence and functions in different aspects of cancer biology, which gives us a broad picture of circ-ABCB10. Thus, this study aimed to generalize the roles of circ-ABCB10 in the diagnosis and treatment of different types of tumors and its related miRNA genes. In this way, we wish to provide a sufficient understanding and assess the future development direction of the research on circ-ABCB10.

Factors influencing degradation kinetics of mRNAs and half-lives of microRNAs, circRNAs, lncRNAs in blood in vitro using quantitative PCR

RNAs are rapidly degraded in samples and during collection, processing and testing. In this study, we used the same method to explore the half-lives of different RNAs and the influencing factors, and compared the degradation kinetics and characteristics of different RNAs in whole blood and experimental samples. Fresh anticoagulant blood samples were incubated at room temperature for different durations, RNAs were extracted, and genes, including internal references, were amplified by real-time quantitative PCR. A linear half-life model was established according to cycle threshold (Ct) values. The effects of experimental operations on RNA degradation before and after RNA extraction were explored. Quantitative analysis of mRNA degradation in samples and during experimental processes were explored using an orthogonal experimental design. The storage duration of blood samples at room temperature had the greatest influence on RNA degradation. The half-lives of messenger RNAs (mRNAs) was 16.4 h. The half-lives of circular RNAs (circRNAs), long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) were 24.56 ± 5.2 h, 17.46 ± 3.0 h and 16.42 ± 4.2 h, respectively. RNA degradation occurred mainly in blood samples. The half-life of mRNAs was the shortest among the four kinds of RNAs. Quantitative experiments related to mRNAs should be completed within 2 h. The half-lives of circRNAs and lncRNAs were longer than those of the former two.

Hsa_circ_0060927 participates in the regulation of Caudatin on colorectal cancer malignant progression by sponging miR-421/miR-195-5p

BACKGROUND

Caudatin is extracted from radix cynanchi bungei and has an inhibitory effect on cancer progression. The study aims to reveal the impacts of hsa_circ_0060927 on Caudatin-mediated colorectal cancer (CRC) development and the underneath mechanism.

METHODS

The expression levels of hsa_circ_0060927, microRNA-421 (miR-421) and miR-195-5p were detected by quantitative real-time reverse transcription-polymerase chain reaction. The protein expression was analyzed by Western blot or immunohistochemistry assay. Cell viability and proliferation were analyzed by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide or 5-Ethynyl-29-deoxyuridine assay. Cell apoptosis was quantified by flow cytometry analysis. Cell migration and invasion were investigated by transwell assay. The putative associations among hsa_circ_0060927, miR-421 and miR-195-5p were predicted by the starbase online database, and identified by dual-luciferase reporter, RNA pull-down and RNA immunoprecipitation (RIP) assays. The impacts of Caudatin treatment on tumor growth in vivo were revealed by a xenograft tumor model assay.

RESULTS

Hsa_circ_0060927 expression was significantly upregulated, whereas miR-421 and miR-195-5p were downregulated in CRC tissues and cells compared with control groups. Hsa_circ_0060927 expression was closely associated with lymph node metastasis and tumor-node-metastasis stage. Caudatin treatment significantly decreased hsa_circ_0060927 expression but increased miR-421 and miR-195-5p expression. Caudatin exposure suppressed CRC cell proliferation, migration and invasion, and induced cell apoptosis; however, hsa_circ_0060927 overexpression hindered these impacts. Additionally, hsa_circ_0060927 was associated with miR-421/miR-195-5p. Depletion of miR-421 or miR-195-5p attenuated the influences of hsa_circ_0060927 silencing on CRC development. Furthermore, Caudatin treatment repressed tumor growth in vivo.

CONCLUSION

Caudatin inhibited CRC cell malignancy through the hsa_circ_0060927/miR-421/miR-195-5p pathway, which provided a potential therapeutic agent for CRC.

Circular RNAs With Efficacy in Preclinical In Vitro and In Vivo Models of Esophageal Squamous Cell Carcinoma

Esophageal cancer is associated with a dismal prognosis. The armamentarium of approved drugs is focused on chemotherapy with modest therapeutic benefit. Recently, checkpoint inhibitory monoclonal antibody Pembrolizumab was approved. In order to identify new targets and modalities for the treatment of esophagus squamous cell carcinoma (ESCC) we searched the literature for circRNAs involved in the pathogenesis of ESCC. We identified two down-regulated and 17 up-regulated circRNAs as well as a synthetic circRNA with efficacy in preclinical in vivo systems. Down-regulated circRNAs sponge microRNAs directed against tumor suppressor genes. Up-regulated circRNAs sponge microRNAs directed against mRNAs, which encode proteins with pro-tumoral functions. We discuss issues such as reconstitution of down-regulated circRNAs and inhibition of up-regulated circRNAs with short interfering RNA (siRNA)- related entities. Also, we address druggability issues of the identified targets.