Circ_0067934 promotes non-small cell lung cancer development by regulating miR-1182/KLF8 axis and activating Wnt/β-catenin pathway

Circular RNA PRKCI (hsa_circ_0067934): a potential target in the pathogenesis of human malignancies

Circular RNAs (circRNAs) are a new type of endogenous non-coding RNA formed by a covalent closed loop. CircRNAs are characterized by specificity, universality, conservation, and stability. They are abundant in eukaryotic cells and have biological regulatory roles at various transcriptional and post-transcriptional levels. The upregulation of circPRKCI has been observed in a variety of tumors and is directly related to the clinicopathological characteristics of tumors and prognosis. More importantly, circPRKCI can participate in the tumorigenesis, progression, recurrence, and metastasis of various tumors through many functional mechanisms, including the activation of signaling pathways, such as the phosphatidylinositol-3-kinase (PI3K)/AKT pathway, and sponging of many microRNAs (miRNAs). This review summarizes the progress achieved in understanding the biological functions of circRNA PRKCI in various tumors. The goal is to inform the discovery of more functional mechanisms and new anticancer molecular targets.

The dual roles of circRNAs in Wnt/β-Catenin signaling and cancer progression

Cancer, a complex pathophysiological condition, arises from the abnormal proliferation and survival of cells due to genetic mutations. Dysregulation of cell cycle control, apoptosis, and genomic stability contribute to uncontrolled growth and metastasis. Tumor heterogeneity, microenvironmental influences, and immune evasion further complicate cancer dynamics. The intricate interplay between circular RNAs (circRNAs) and the Wnt/β-Catenin signalling pathway has emerged as a pivotal axis in the landscape of cancer biology. The Wnt/β-Catenin pathway, a critical regulator of cell fate and proliferation, is frequently dysregulated in various cancers. CircRNAs, a class of non-coding RNAs with closed-loop structures, have garnered increasing attention for their diverse regulatory functions. This review systematically explores the intricate crosstalk between circRNAs and the Wnt/β-Catenin pathway, shedding light on their collective impact on cancer initiation and progression. The review explores the diverse mechanisms through which circRNAs modulate the Wnt/β-Catenin pathway, including sponging microRNAs, interacting with RNA-binding proteins, and influencing the expression of key components in the pathway. Furthermore, the review highlights specific circRNAs implicated in various cancer types, elucidating their roles as either oncogenic or tumour-suppressive players in the context of Wnt/β-Catenin signaling. The intricate regulatory networks formed by circRNAs in conjunction with the Wnt/β-Catenin pathway are discussed, providing insights into potential therapeutic targets and diagnostic biomarkers. This comprehensive review delves into the multifaceted roles of circRNAs in orchestrating tumorigenesis through their regulatory influence on the Wnt/β-Catenin pathway.

Wnt/β-catenin-driven EMT regulation in human cancers

Metastasis accounts for 90% of cancer-related deaths among the patients. The transformation of epithelial cells into mesenchymal cells with molecular alterations can occur during epithelial-mesenchymal transition (EMT). The EMT mechanism accelerates the cancer metastasis and drug resistance ability in human cancers. Among the different regulators of EMT, Wnt/β-catenin axis has been emerged as a versatile modulator. Wnt is in active form in physiological condition due to the function of GSK-3β that destructs β-catenin, while ligand-receptor interaction impairs GSK-3β function to increase β-catenin stability and promote its nuclear transfer. Regarding the oncogenic function of Wnt/β-catenin, its upregulation occurs in human cancers and it can accelerate EMT-mediated metastasis and drug resistance. The stimulation of Wnt by binding Wnt ligands into Frizzled receptors can enhance β-catenin accumulation in cytoplasm that stimulates EMT and related genes upon nuclear translocation. Wnt/β-catenin/EMT axis has been implicated in augmenting metastasis of both solid and hematological tumors. The Wnt/EMT-mediated cancer metastasis promotes the malignant behavior of tumor cells, causing therapy resistance. The Wnt/β-catenin/EMT axis can be modulated by upstream mediators in which non-coding RNAs are main regulators. Moreover, pharmacological intervention, mainly using phytochemicals, suppresses Wnt/EMT axis in metastasis suppression.

Prognostic and clinical value of circPRKCI expression in diverse human cancers

BACKGROUND

Highly expressed in various human cancers, circular RNA Protein Kinase C Iota (circPRKCI) has been reported to play an important role in cancer development and progression. Herein, we sought to reveal the prognostic and clinical value of circPRKCI expression in diverse human cancers.

METHODS

We searched the Pubmed, Web of Science, and the Cochrane Library databases from inception until May 16, 2021. The relationship between circPRKCI expression and cancer patients' survival, including overall survival (OS) and disease-free survival (DFS), was assessed by pooled hazard ratios (HR) with corresponding 95% confidence interval (CI). The correlation between circPRKCI expression and clinical outcomes was evaluated using odds ratios (OR) with corresponding 95% CI. The data were analyzed by STATA software (version 12.0) or Review Manager (RevMan 5.3).

RESULTS

A total of 15 studies with 1109 patients were incorporated into our meta-analysis. The results demonstrated that high circPRKCI expression was significantly related to poor OS (HR = 1.96, 95% CI: 1.61, 2.39, P <0.001) when compared with low circPRKCI expression in diverse human cancers. However, elevated circPRKCI expression was not associated with DFS (HR = 1.34, 95% CI: 0.93, 1.95, P = 0.121). Furthermore, the patient with a higher circPRKCI expression was prone to have a larger tumor size, advanced clinical stage, and lymph node metastasis, but it was not significantly correlated with age, gender, and distant metastasis.

CONCLUSION

Elevated circPRKCI expression was correlated with worse OS and unfavorable clinical features, suggesting a novel prognostic and predictive role of circPRKCI in diverse human cancers.

Analysis of Potential Circular RNAs in Regulating Imatinib Resistance of Gastrointestinal Stromal Tumor

INTRODUCTION

Recent studies have found that circular RNA is an abundant RNA species that belongs to part of the competing endogenous RNA network (ceRNA), which was proven to play an important role in the development, diagnosis and progress of diseases. However, the function of circRNAs in imatinib resistance in Gastrointestinal stromal tumor (GIST) are poorly understood so for. The present study aimed to screen and predict the potential circRNAs in imatinib resistance of GIST using microarray analysis.

METHODS

We determined the expression of circular RNAs in paired normal gastric tissues (N), primary GIST (gastrointestinal stromal tumor) tissues (YC) and imatinib mesylate secondary resistance GIST tissues (C) with microarray and predicted 8677 dysregulated circular RNAs.

RESULTS

Compared with the YC group, we identified 15 circRNAs that were up-regulated and 8 circRNAs that were down-regulated in the C group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that these host linear transcripts that differentially express circular RNAs are involved in many key biological pathways, predicting the potential tumor-genesis and drug resistance mechanismrelated to HIF-1 pathway, later we draw the cirRNA-miRNA-mRNA network involved in the HIF-1 pathway and found several dysregulated circRNAs and the relationship between circRNA-miRNAs-mRNA, such as circRNA_06551, circRNA_14668, circRNA_04497, circRNA_08683, circRNA_09923(Green, down-regulation) and circRNA_23636, circRNA_15734 (Red, up-regulation).

CONCLUSION

Taken together, we identified a panel of dysregulated circRNAs that may be potential biomarkers even therapy relevant to the GIST, especially imatinib secondary resistance GIST.

The role of circRNAs in regulation of drug resistance in ovarian cancer

Ovarian cancer is one of the female reproductive system tumors. Chemotherapy is used for advanced ovarian cancer patients; however, drug resistance is a pivotal cause of chemotherapeutic failure. Hence, it is critical to explore the molecular mechanisms of drug resistance of ovarian cancer cells and to ameliorate chemoresistance. Noncoding RNAs (ncRNAs) have been identified to critically participate in drug sensitivity in a variety of human cancers, including ovarian cancer. Among ncRNAs, circRNAs sponge miRNAs and prevent miRNAs from regulation of their target mRNAs. CircRNAs can interact with DNA or proteins to modulate gene expression. In this review, we briefly describe the biological functions of circRNAs in the development and progression of ovarian cancer. Moreover, we discuss the underneath regulatory molecular mechanisms of circRNAs on governing drug resistance in ovarian cancer. Furthermore, we mention the novel strategies to overcome drug resistance via targeting circRNAs in ovarian cancer. Due to that circRNAs play a key role in modulation of drug resistance in ovarian cancer, targeting circRNAs could be a novel approach for attenuation of chemoresistance in ovarian cancer.

In-depth study of anticancer drug diffusion through a cross-linked -pH-responsive polymeric vesicle membrane

Post-encapsulation and release of the anticancer drug doxorubicin hydrochloride (DOX·HCl) through cell-like transmission functions of polymeric vesicles were studied using cross-linked pH-responsive polymeric vesicles. The vesicles were fabricated for the first time via the redox-initiated reversible addition-fragmentation chain transfer dispersion polymerization in ethanol-water mixture, using 2-(diisopropylamino)ethyl methacrylate and glycidyl methacrylate, and the vesicle membrane was modified post-cross-linking by using ethylenediamine. A phase diagram was constructed for reproducible fabrication of the polymeric vesicles, and well-shaped vesicles were formed when the target degree of polymerization of the hydrophobic polymer chains was equal to or higher than 50 with solid content in the range of 10-30 wt%. The cross-linked vesicle membrane served as a gate enabling "open" and "closed" states in response to pH stimulation. Up to 50% drug loading efficiency and 39% drug loading content could be achieved, and in vitro release of the DOX-loaded vesicles in aqueous buffer solutions showed a much faster DOX release rate at pH 5.0 than at pH 6.5. The polymeric vesicles were of very low cytotoxicity to A549 cells up to the concentration of 2 mg/mL, and the IC₅₀ of DOX-loaded vesicles were higher than that of the free DOX. The intracellular DOX release study indicated higher cellular uptake capability for DOX-loaded vesicles than that of free DOX.

Circ_0067934: a circular RNA with roles in human cancer

A circular RNA (circRNA) is a non-coding RNA (ncRNA) derived from reverse splicing from pre-mRNA and is characterized by the absence of a cap structure at the 5' end and a poly-adenylated tail at the 3' end. Owing to the development of RNA sequencing and bioinformatics approaches in recent years, the important clinical value of circRNAs has been increasingly revealed. Circ_0067934 is an RNA molecule of 170 nucleotides located on chromosome 3q26.2. Circ_0067934 is formed via the reverse splicing of exons 15 and 16 in PRKCI (protein kinase C Iota). Recent studies revealed the upregulation or downregulation of circ_0067934 in various tumors. The expression of circ_0067934 was found to be correlated with tumor size, TNM stage, and poor prognosis. Based on experiments with cancer cells, circ_0067934 promotes cancer cell proliferation, migratory activity, and invasion when overexpressed or downregulated. The potential mechanism involves the binding of circ_0067934 to microRNAs (miRNAs; miR-545, miR-1304, miR-1301-3p, miR-1182, miR-7, and miR-1324) to regulate the post-transcriptional expression of genes. Other mechanisms include inhibition of the Wnt/β-catenin and PI3K/AKT signaling pathways. Here, we summarized the biological functions and possible mechanisms of circ_0067934 in different tumors to enable further exploration of its translational applications in clinical diagnosis, therapy, and prognostic assessments.

Circular RNAs: novel actors of Wnt signaling pathway in lung cancer progression

Circular RNAs (CircRNAs) are a class of regulatory RNA transcripts, which are ubiquitously expressed in eukaryotes. CircRNA dysregulation has been shown to disrupt the interaction of the Wnt/β-catenin pathway, which regulates several biological processes involved in tumorigenesis, thereby contributing to the development and progression of cancer. Interactions of tumor-derived circRNAs with the Wnt/β-catenin signaling pathway provide both clinical diagnostic biomarkers and promising therapeutic targets. In this review, we outlined current evidence on the roles of circRNAs associated with the Wnt/β-catenin pathway in regulating lung cancer formation and development. We believe that our findings will assist in the advancement or establishment of circRNA-based lung cancer therapeutic approaches.

Non-coding RNA-based therapeutics in cancer therapy: An emphasis on Wnt/β-catenin control

Non-coding RNA transcripts are RNA molecules that have mainly regulatory functions and they do not encode proteins. microRNAs (miRNAs), lncRNAs and circRNAs are major types of this family and these epigenetic factors participate in disease pathogenesis, especially cancer that their abnormal expression may lead to cancer progression. miRNAs and lncRNAs possess a linear structure, whereas circRNAs possess ring structures and high stability. Wnt/β-catenin is an important factor in cancer with oncogenic function and it can increase growth, invasion and therapy resistance in tumors. Wnt upregulation occurs upon transfer of β-catenin to nucleus. Interaction of ncRNAs with Wnt/β-catenin signaling can determine tumorigenesis. Wnt upregulation is observed in cancers and miRNAs are able to bind to 3'-UTR of Wnt to reduce its level. LncRNAs can directly/indirectly regulate Wnt and in indirect manner, lncRNAs sponge miRNAs. CircRNAs are new emerging regulators of Wnt and by its stimulation, they increase tumor progression. CircRNA/miRNA axis can affect Wnt and carcinogenesis. Overall, interaction of ncRNAs with Wnt can determine proliferation rate, migration ability and therapy response of cancers. Furthermore, ncRNA/Wnt/β-catenin axis can be utilized as biomarker in cancer and for prognostic applications in patients.

Circ_0067934 as a novel therapeutic target in cancer: From mechanistic to clinical perspectives

Circular RNAs, as a type of non-coding RNAs, are identified in a various cell. Circular RNAs have stable structures, conserved sequence, and tissue and cell-specific level. High throughput technologies have proposed that circular RNAs act via various mechanisms like sponging microRNAs and proteins, regulating transcription factors, and scaffolding mediators. Cancer is one of the major threat for human health. Emerging data have proposed that circular RNAs are dysregulated in cancers as well as are associated with aggressive behaviors of cancer -related behaviors like cell cycle, proliferation, apoptosis, invasion, migration, and epithelial-mesenchymal transition (EMT). Among them, circ_0067934 was shown to act as an oncogene in cancers to enhance migration, invasion, proliferation, cell cycle, EMT, and inhibit cell apoptosis. In addition, these studies have proposed that it could be a promising diagnostic and prognostic biomarker in cancer. This study aimed to review the expression and molecular mechanism of circ_0067934 in modulating the malignant behaviors of cancers as well as to explore its potential as a target in cancer chemotherapy, diagnosis, prognosis and treatment.

hsa_circ_0136839 regulates the malignant phenotypes of nasopharyngeal carcinoma via the Wnt/β-catenin signaling pathway

With the development of RNA sequencing (RNA-seq) technology, circular RNA (circRNA), a new class of RNA, has received much attention in cancer research. However, information available on the biogenesis and functional value of circRNAs in nasopharyngeal carcinoma (NPC) is scarce. In the present study, we screened the circRNA profile of the NPC cell line C666-1 compared with that of the normal control NP69 by RNA-seq and identified a novel and relatively higher expressed circRNA, hsa_circ_0136839. Hsa_circ_0136839 was markedly downregulated in NPC tissues, as confirmed by quantitative reverse transcription polymerase chain reaction. Functional in vitro studies revealed that hsa_circ_0136839 knockdown in C666-1 cell notably promoted cell proliferation, migration, and invasion abilities, as well as affected cell cycle distribution with an S-phase arrest. However, hsa_circ_0136839 overexpression in CNE2 cells resulted in an opposite response. Mechanistically, we demonstrated that aberrant hsa_circ_0136839 expression might affect the malignant phenotypes of NPC cells by activating the wnt/β-catenin signaling pathway. Thus, our findings contribute to further the understanding of NPC pathogenesis and provide new ideas for NPC clinical diagnosis and treatment.

Circular RNAs in chemotherapy resistance of lung cancer and their potential therapeutic application

Lung cancer is one of the high malignancy-related incidence and mortality worldwide, accounting for about 13% of total cancer diagnoses. Currently, the use of anti-cancer agents is still the main therapeutic method for lung cancer. However, cancer cells will gradually show resistance to these drugs with the progress of treatment. And the molecular mechanisms underlying chemotherapy agents resistance remain unclear. circRNAs are newly identified noncoding RNAs molecules with covalently closed circular structures. Previous studies have shown that circRNAs are associated with tumorigenesis and progression of various cancers, including lung cancer. Recently, growing reports have suggested that circRNAs could contribute to drug resistance of lung cancer cell through different mechanisms. Therefore, in this review, we summarized the functions and underlying mechanisms of circRNAs in regulating chemoresistance of lung cancer and discussed their potential applications for diagnosis, prognosis, and treatment of lung cancer.

Circ-HSP90A expedites cell growth, stemness, and immune evasion in non-small cell lung cancer by regulating STAT3 signaling and PD-1/PD-L1 checkpoint

BACKGROUND

Circular RNAs (circRNAs) are important participators in tumor progression for their stable structure and high tissue-specific expression. The purpose of this research was to clarify the potential and mechanism of a novel circRNA-circ-HSP90A in non-small cell lung cancer (NSCLC).

METHODS

Biological potentials of circ-HSP90A in NSCLC were measured by functional assays. Molecular interaction was assessed by bioinformatics analysis and mechanical assays.

RESULTS

Results depicted that circ-HSP90A was cyclization from its host gene heat shock protein 90 alpha (HSP90A) and was up-regulated in NSCLC cells. Circ-HSP90A depletion retarded proliferation, migration, invasion, and immune evasion. Mechanistically, circ-HSP90A recruited ubiquitin specific peptidase 30 (USP30) to stabilize HSP90A and then stimulated the signal transducer and activator of transcription 3 (STAT3) signaling. Meanwhile, circ-HSP90A sponged miR-424-5p to programmed cell death ligand 1 (PD-L1).

CONCLUSIONS

Our study firstly showed that circ-HSP90A promoted cell growth, stemness, and immune evasion in NSCLC through regulating STAT3 signaling and programmed cell death 1 (PD-1)/PD-L1 checkpoint, mirroring that targeting circ-HSP90A might become a novel target of immunotherapy in NSCLC.

The emerging role of circular RNAs in drug resistance of non-small cell lung cancer

Due to the characteristics of aggressiveness and high risk of postoperative recurrence, non-small cell lung cancer (NSCLC) is a serious hazard to human health, accounting for 85% of all lung cancer cases. Drug therapies, including chemotherapy, targeted therapy and immunotherapy, are effective treatments for NSCLC in clinics. However, most patients ultimately develop drug resistance, which is also the leading cause of treatment failure in cancer. To date, the mechanisms of drug resistance have yet to be fully elucidated, thus original strategies are developed to overcome this issue. Emerging studies have illustrated that circular RNAs (circRNAs) participate in the generation of therapeutic resistance in NSCLC. CircRNAs mediate the modulations of immune cells, cytokines, autophagy, ferroptosis and metabolism in the tumor microenvironment (TME), which play essential roles in the generation of drug resistance of NSCLC. More importantly, circRNAs function as miRNAs sponges to affect specific signaling pathways, directly leading to the generation of drug resistance. Consequently, this review highlights the mechanisms underlying the relationship between circRNAs and drug resistance in NSCLC. Additionally, several therapeutic drugs associated with circRNAs are summarized, aiming to provide references for circRNAs serving as potential therapeutic targets in overcoming drug resistance in NSCLC.

Circ_0002476 regulates cell growth, invasion, and mtDNA damage in non-small cell lung cancer by targeting miR-1182/TFAM axis

BACKGROUND

Many circular RNAs (circRNAs) have been identified as potential targets for cancer therapy. However, the role of circ_0002476 in non-small cell lung cancer (NSCLC) progression has not been explored.

METHODS

The expression levels of circ_0002476, microRNA (miR)-1182, and mitochondrial transcription factor A (TFAM) were detected by quantitative real-time polymerase chain reaction. Cell functions were measured by cell counting kit 8 assay, EdU assay, colony formation assay, flow cytometry and transwell assay. Mitochondrial DNA (mtDNA) damage was assessed by measuring mtDNA copy number and transcript levels of ND1 and ATP6. Protein expression was examined by western blot. The interaction between miR-1182 and circ_0002476 or TFAM was detected by dual-luciferase reporter assay and RNA pull-down assay. Animal experiments were performed to explore circ_0002476 role in vivo. Exosomes (Exs) were extracted and identified by transmission electron microscopy and nanoparticle tracking analysis.

RESULTS

Circ_0002476 was overexpressed in NSCLC tissues and cells. Circ_0002476 knockdown suppressed NSCLC cell proliferation and invasion, while promoted apoptosis and mtDNA damage. Circ_0002476 could sponge miR-1182, and miR-1182 inhibitor reversed the influence induced by circ_0002476 knockdown. Moreover, TFAM was targeted by miR-1182, and miR-1182 hindered NSCLC cell progression by regulating TFAM. Additionally, circ_0002476 silencing could reduce NSCLC tumor growth by miR-1182/TFAM. Further analyzed showed that Exs were involved in the transport of circ_0002476 between cells.

CONCLUSION

Taken together, our findings suggested that circ_0002476 might be a potential molecular target for NSCLC treatment.

Immunomodulatory functions of the circ_001678/miRNA-326/ZEB1 axis in non-small cell lung cancer via the regulation of PD-1/PD-L1 pathway

High-throughput circRNA sequencing identified circRNA_001678 (circ_001678) as an upregulated circRNA in NSCLC tissues. Hence, the current study sought to investigate the function and the underlying mechanism of circRNA_001678 in immune escape of NSCLC. Briefly, commercially purchased NSCLC cell lines were adopted for in vitro experiment to evaluate the effects of circ_001678 over-expression or knockdown on cell biological functions, including proliferation, migration, and invasive abilities. In addition, the effects of circ_001678 on the in vivo tumorigenicity ability were evaluated for verification. Accordingly, we uncovered that circ_001678 over-expression augmented NSCLC progression in vitro and enhanced tumorigenicity ability in vivo. The interaction between circ_001678 and miR-326 predicted online was verified by means of luciferase and RNA pull-down assays. Furthermore, circ_001678 could sponge miR-326 to up-regulate ZEB1. On the other hand, the tumor-promoting effects of circ_001678 could be inhibited by anti-PD-L1/PD-1 treatment. Mechanistically, circ_001678 led to the activation of the PD-1/PD-L1 pathway to promote CD8+ T cell apoptosis, thereby inducing NSCLC cell immune escape via regulation of the miR-326/ZEB1 axis. To conclude, our findings revealed that circ_001678 sponges miR-326 to up-regulate ZEB1 expression and induce the PD-1/PD-L1 pathway-dependent immune escape, thereby promoting the malignant progression of NSCLC.

hsa_circ_0000518 Facilitates Non-Small-Cell Lung Cancer Progression via Moderating miR-330-3p and Positively Regulating SLC1A5

Background/Aim

Non-small-cell lung cancer (NSCLC) is the principal agent of cancer deaths globally. The goal of this study was to determine how circular RNA_0000518 (circ_0000518) regulates tumor progression. Materials/Methods. circ_0000518 was selected as a study target involved in NSCLC from GEO (Gene Expression Omnibus) database. circ_0000518 level was gauged by qRT-PCR. It was confirmed as circRNA by actinomycin D inhibition and RNase R assay. Subcellular localization of circ_0000518 was identified by FISH. Cell function was determined by CCK-8, Transwell, and western blot. Glutamine metabolic factors were detected by ELISA. The target regulation relationship between genes was clarified by dual-luciferase reporter assay. In vivo models were established to evaluate the impact of circ_0000518 on tumor growth. Immunohistochemical staining for Ki67, vimentin, and E-cadherin was used to detect cell proliferation and metastasis, respectively.

Results

circ_0000518 expression was enhanced in NSCLC. si-circ_0000518 inhibited cell proliferation, invasion, and glutamine metabolism. circ_0000518 functioned as a molecular sponge for miR-330-3p, and inhibition of miR-330-3p in cells markedly reversed circ_0000518 interference-mediated antitumor effects. miR-330-3p interacted with 3′-UTR of SLC1A5. miR-330-3p inhibitor-mediated protumor effect was remarkably reversed in cells after the knockdown of SLC1A5. circ_0000518 knockdown reduced glutamine, glutamate, and α-KG by targeting miR-330-3p. Intertumoral injection of circ_0000518 shRNA adeno-associated virus effectively halted xenograft tumor growth.

Conclusion

The current study revealed that circ_0000518 may have a prooncogenic function in the formation and progression of NSCLC, which might be achieved through moderating the miR-330-3p/SLC1A5 axis.

CircRNAs in lung cancer- role and clinical application

Lung cancer holds the highest mortality rate among malignancies worldwide. Nevertheless, the potential molecular mechanisms of its tumorigenesis and evolution remain obscure. Circular RNAs (circRNAs), a broad category of covalently closed molecules, follow a malignancy-restricted expression pattern. Leading-edge studies have demonstrated the clinical application prospects of circRNAs in lung cancer. Herein, this review elucidates the biogenesis, biological functions, and pathophysiology of circRNAs. Furthermore, we underscore the forefront of the diagnostic, prognostic, and therapeutic potential of circRNAs in lung cancer as well as discuss the bottleneck that needs to be overcome to translate the basic advances of circRNAs into clinical practice.

Critical Roles of Circular RNA in Tumor Metastasis via Acting as a Sponge of miRNA/isomiR

Circular RNAs (circRNAs), a class of new endogenous non-coding RNAs (ncRNAs), are closely related to the carcinogenic process and play a critical role in tumor metastasis. CircRNAs can lay the foundation for tumor metastasis via promoting tumor angiogenesis, make tumor cells gain the ability of migration and invasion by regulating epithelial-mesenchymal transition (EMT), interact with immune cells, cytokines, chemokines, and other non-cellular components in the tumor microenvironment, damage the normal immune function or escape the immunosuppressive network, and further promote cell survival and metastasis. Herein, based on the characteristics and biological functions of circRNA, we elaborated on the effect of circRNA via circRNA-associated competing endogenous RNA (ceRNA) network by acting as miRNA/isomiR sponges on tumor angiogenesis, cancer cell migration and invasion, and interaction with the tumor microenvironment (TME), then explored the potential interactions across different RNAs, and finally discussed the potential clinical value and application as a promising biomarker. These results provide a theoretical basis for the further application of metastasis-related circRNAs in cancer treatment. In summary, we briefly summarize the diverse roles of a circRNA-associated ceRNA network in cancer metastasis and the potential clinical application, especially the interaction of circRNA and miRNA/isomiR, which may complicate the RNA regulatory network and which will contribute to a novel insight into circRNA in the future.

Knockdown of circ_0067934 inhibits gastric cancer cell proliferation, migration and invasion via the miR‑1301‑3p/KIF23 axis

In recent years, circular RNAs (circRNAs/circs) have attracted significant attention due to their potentially important functions in a variety of human cancer types. circ_0067934 is a newly identified circRNA, the role of which in gastric cancer (GC) has yet to be reported, to the best of our knowledge. In the present study, the expression levels of circ_0067934, microRNA (miR)‑1301‑3p and kinesin family member 23 (KIF23) in GC cells were detected via reverse transcription‑quantitative PCR. Cell proliferation was measured using Cell Counting Kit‑8 assays and EdU staining. Wound healing and Transwell assays were performed to assess cell migration and invasion, respectively. Western blotting was performed to measure the protein expression levels of Ki67, proliferating cell nuclear antigen, MMP2, MMP9 and KIF23. The starBase database and luciferase reporter assays were used to predict and verify the binding between circ_0067934 and miR‑1301‑3p, as well as KIF23, in GC cells. The results demonstrated that circ_0067934 expression was upregulated in GC cells, and circ_0067934 silencing significantly inhibited GC cell proliferation, migration and invasion. In addition, miR‑1301‑3p was regulated by circ_0067934, and miR‑1301‑3p overexpression suppressed GC cell migration, invasion and proliferation. miR‑1301‑3p was found to target KIF23, and KIF23 overexpression reversed the effects of circ_0067934 silencing and miR‑1301‑3p overexpression on cell proliferation, migration and invasion. In conclusion, circ_0067934 may regulate the proliferation, invasion and migration of GC cells via the miR‑1301‑3p/KIF23 signaling axis, which may represent a novel therapeutic target for GC metastasis.

The functional roles of the circRNA/Wnt axis in cancer

CircRNAs, covalently closed noncoding RNAs, are widely expressed in a wide range of species ranging from viruses to plants to mammals. CircRNAs were enriched in the Wnt pathway. Aberrant Wnt pathway activation is involved in the development of various types of cancers. Accumulating evidence indicates that the circRNA/Wnt axis modulates the expression of cancer-associated genes and then regulates cancer progression. Wnt pathway-related circRNA expression is obviously associated with many clinical characteristics. CircRNAs could regulate cell biological functions by interacting with the Wnt pathway. Moreover, Wnt pathway-related circRNAs are promising potential biomarkers for cancer diagnosis, prognosis evaluation, and treatment. In our review, we summarized the recent research progress on the role and clinical application of Wnt pathway-related circRNAs in tumorigenesis and progression.

Identification of circ_0000375 and circ_0011536 as novel diagnostic biomarkers of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) imposes a tremendous burden on human health, with high morbidity and mortality. Circular ribonucleic acids (circRNAs), a new type of noncoding RNA, are considered to participate in cancer pathogenesis as microRNA (miRNA) sponges. However, the dysregulation and biological functions of circRNAs in CRC remain to be explored.

AIM

To identify potential circRNA biomarkers of CRC and explore their functions in CRC carcinogenesis.

METHODS

CircRNAs and miRNAs differentially expressed in CRC tissues were identified by analyzing expression profiles from the Gene Expression Omnibus (GEO) database. Circ_0000375 and circ_0011536 were selected as CRC biomarker candidates. Quantitative real-time polymerase chain reaction was utilized to evaluate the expression of these 2 circRNAs in CRC tissues, serums and cell lines. Receiver operating characteristic curves were generated to assess the diagnostic performances of these 2 circRNAs. Then, functional experiments, including cell counting kit-8, wound healing and Transwell invasion assays, were performed after the overexpression of circ_0000375 and circ_0011536 in CRC cell lines. Furthermore, candidate target miRNAs of circ_0000375 and circ_0011536 were predicted via bioinformatics analysis. The expression levels of these miRNAs were explored in CRC cell lines and tissues from GEO datasets. A luciferase reporter assay was developed to examine the interactions between circRNAs and miRNAs. Based on the target miRNAs and downstream genes, functional enrichment analyses were applied to reveal the critical signaling pathways involved in CRC carcinogenesis.

RESULTS

Downregulated circ_0000375 and circ_0011536 expression was observed in CRC tissues in GSE126095, clinical CRC tissue and serum samples and CRC cell lines. The areas under the curve for circ_0000375 and circ_0011536 were 0.911 and 0.885 in CRC tissue and 0.976 and 0.982 in CRC serum, respectively. Moreover, the serum levels of these 2 circRNAs were higher in patients at 30 d postsurgery than in patients before surgery, suggesting that the serum expression of circ_0000375 and circ_0011536 is related to CRC tumorigenesis. Circ_0000375 and circ_0011536 overexpression inhibited the proliferation, migration and invasion of CRC cells. Furthermore, miR-1182 and miR-1246, which were overexpressed in CRC tissues in GSE41655, GSE49246 and GSE115513, were verified as target miRNAs of circ_0000375 and circ_0011536, respectively, by luciferase reporter assays. The downstream genes of miR-1182 and miR-1246 were enriched in some CRC-associated pathways, such as the Wnt signaling pathway.

CONCLUSION

Circ_0000375 and circ_0011536 may function as tumor suppressors in CRC progression, serving as novel biomarkers for CRC diagnosis and as promising candidates for therapeutic exploration.

Kruppel like factor 16 promotes lung adenocarcinoma progression by upregulating lamin B2

Lung cancer is one of the most common causes of cancer-related death. In the past decade, the treatment and diagnosis of lung cancer have progressed significantly in early efforts to promote the survival of lung cancer patients. Kruppel like factor 16 (KLF16) is a zinc finger transcription factor that regulates a diverse array of developmental events and cellular processes. KLF16 is involved in the progression of various cancer types. However, the role of KLF16 in the development of lung cancer remains unknown. In this study, KLF16 was overexpressed in lung cancer samples. KLF16 downregulation inhibited lung cancer cell proliferation and migration. Conversely, KLF16 overexpression promoted lung cancer cell growth and invasion. Mechanistically, the expression level LMNB2 was suppressed by KLF16 knockdown and was promoted by KLF16 overexpression. The overall survival of patients with high LMNB2 levels was poor. Luciferase assays showed that KLF16 promoted the transcription activity of LMNB2 gene. Concomitantly, the expression level of LMNB2 was also higher in lung adenocarcinoma (LUAD) than in normal tissues, and its knockdown or overexpression can reverse the effect of KLF16 overexpression or knockdown on lung cancer cell proliferation, migration, and even tumorigenesis, indicating that LMNB2 also functions as an oncogene. In conclusion, KLF16 can be used as a potential therapeutic and preventive biomarker in lung cancer treatment and prognosis by actively regulating the expression of LMNB2.

Biogenesis, functions, and clinical implications of circular RNAs in non-small cell lung cancer

Lung cancer (LC) is the leading cause of cancer-related deaths worldwide, with high morbidity and mortality. Non-small cell lung cancer (NSCLC) is a major pathological type of LC and accounts for more than 80% of all cases. Circular RNAs (circRNAs) are a large class of non-coding RNAs (ncRNAs) with covalently closed-loop structures, a high abundance, and tissue-specific expression patterns. They participate in various pathophysiological processes by regulating complex gene networks involved in proliferation, apoptosis, migration, and epithelial-to-mesenchymal transition (EMT), as well as metastasis. A growing number of studies have revealed that the dysregulation of circRNAs contributes to many aspects of cancer progression, such as its occurrence, metastasis, and recurrence, suggesting their great potential as efficient and specific biomarkers in the diagnosis, prognosis, and therapeutic targeting of NSCLC. In this review, we systematically elucidate the characteristics, biogenesis, and functions of circRNAs and focus on their molecular mechanisms in NSCLC progression. Moreover, we highlight their clinical implications in NSCLC treatment.

Circ_0067934 reduces JNK phosphorylation through a microRNA-545-3p/PPA1 axis to enhance tumorigenesis and cisplatin resistance in ovarian cancer

BACKGROUND

Circular RNA 0067934 (circ_0067934) has been revealed as a cancer driver in multiple human malignancies, whereas its action in the pathogenesis of ovarian cancer (OC) remains unclear. This study focuses on the function of circ_0067934 in tumorigenesis and cisplatin (DDP) resistance in OC and the molecular mechanism.

METHODS

Expression of circ_0067934 in OC tissues and cells was examined, and its correlation with the clinical characteristics of patients was analyzed. Candidate targets of circ_0067934 were predicted using bioinformatics systems. Binding relationships between circ_0067934 and microRNA (miR)-545-3p and between miR-545-3p and inorganic pyrophosphatase 1 (PPA1) were validated via luciferase assays. Gain- and loss-of functions of circ_0067934, miR-545-3p and PPA1 were performed to determine their functions in proliferation, invasion, apoptosis and DDP resistance of OC cells in vitro and in vivo.

RESULTS

Circ_0067934 was overexpressed in OC samples and associated with advanced tumor staging and lymph node metastasis. Downregulation of circ_0067934 reduced DDP resistance of the DDP-resistant A2780/DDP cell line and reduced cell proliferation and invasion, but the malignant behaviors of OC cells were restored after further miR-545-3p downregulation. Circ_0067934 served as a sponge for miR-545-3p and diminished its suppressive effect on PPA1 translation. Artificial upregulation of PPA1 enhanced proliferation, invasion and DDP resistance of A2780/DDP cells, and it reduced phosphorylation of the pro-apoptotic JNK signaling. Similar results were found in vivo.

CONCLUSION

This study suggests that circ_0067934 sequesters miR-545-3p and enhances PPA1 expression to promote tumorigenesis and DDP resistance in OC. This study may provide novel approaches in the management of OC.

Circular RNA Circ_0067934 Attenuates Ferroptosis of Thyroid Cancer Cells by miR-545-3p/SLC7A11 Signaling

Ferroptosis is an emerging programmed cell death distinguished from apoptosis and autophagy and plays essential roles in tumorigenesis. Thyroid cancer is a prevalent endocrine tumor, but the molecular mechanism of ferroptosis during thyroid cancer development remains unclear. Here, we identified the critical function of circular RNA circ_0067934 in repressing ferroptosis of thyroid cancer cells. Our data showed that the ferroptosis activator erastin decreased thyroid cancer cell viabilities, while the circ_0067934 shRNA further attenuated erastin-inhibited cell viabilities. The silencing of circ_0067934 enhanced the levels of ferroptosis-related markers, including Fe2+, iron, and ROS in the cells. The knockdown of circ_0067934 induced thyroid cancer cell apoptosis and repressed thyroid cancer cell proliferation in vitro and in vivo. Circ_0067934 upregulated the expression of the ferroptosis-negative regulator SLC7A11 by sponging and inhibiting miR-545-3p in thyroid cancer cells. The overexpression of SLC7A11 or the inhibitor of miR-545-3p reversed circ_0067934 silencing-regulated thyroid cancer cell proliferation. Therefore, we concluded that Circ_0067934 attenuated ferroptosis of thyroid cancer cells by miR-545-3p/SLC7A11 signaling. Circ_0067934 may serve as a potential therapeutic target by regulating ferroptosis for the treatment of thyroid cancer.

The Circ_CARM1 controls cell migration by regulating CTNNBIP1 in anti-benzo[a]pyrene-trans-7,8-dihydrodiol-9,10-epoxide-transformed 16HBE cells

BACKGROUND

Circular RNAs (circRNAs) have an important role in the development and progression of human tumors, including lung cancer. Yet, their role in lung cancer induced by benzo(a)pyrene (B[a]P) remains unclear. In this study, circRNA chips and qRT-PCR were used to examine downregulated circRNAs in malignantly transformed 16HBE cells (16HBE-T) induced by B[a]P. Five down-regulated circRNAs were found, among which hsa_circ_0004552 (circ_CARM1) had the most significant downregulation. Consequently, the role of circ_CARM1 on 16HBE-T cells biological behavior was further examined using several in vitro experiments.

MATERIALS AND METHODS

Detecting RNA expression via qRT-PCR. Fluorescence in situ hybridization (FISH) was used to identify the localization of circ_CARM1 in 16HBE-T. The effect of circ_CARM1 on cell behavior (cell migration, proliferation, and apoptosis) was explored by transfecting cells with a vector carrying an overexpression and then using wound healing, transwell migration assay, and flow cytometry. Also, the regulation mechanism for circ_CARM1, miR-1288-3p, and CTNNBIP1 was studied by Dual-Luciferase® Reporter (DLR™) Assay System and western blotting.

RESULTS

Reduced expression of circ_CARM1 is observed in 16HBE-T. The overexpression of circ_CARM1 further inhibited the migration of 16HBE-T cells but did not affect cell proliferation and apoptosis. Furthermore, bioinformatic analysis and Dual-Luciferase® Reporter (DLR™) Assay System showed that the competitive binding of circ_CARM1 and miR-1288-3p enhanced the expression of CTNNBIP1, thereby inhibiting the migration of 16HBE-T cells.

CONCLUSION

Downregulation of circ_CARM1 can stimulate the expression of miR-1288-3p, thereby reducing the expression of CTNNBIP1, spurring cell migration.

Hsa_circ_0032131 knockdown inhibits osteoarthritis progression via the miR-502-5p/PRDX3 axis

Osteoarthritis (OA) is a chronic disease characterized by progressive loss of cartilage and failure of the diarthrodial joint. Circular RNAs (circRNAs) are known to participate in the pathogenesis of multiple diseases, including OA. We investigated the functions of hsa_circ_0032131, a circRNA upregulated in OA, using CHON-001 cells and an in vivo OA rat model. CHON-001 cells were treated with interleukin (IL)-1β to mimic OA in vitro. IL-1β-induced inhibition of CHON-001 growth was reversed by silencing hsa_circ_0032131. In addition, hsa_circ_0032131 knockdown reversed IL-1β-induced activation of Trx1, Cyclin D and PRDX3, whereas overexpression of PRDX3, a direct target of miR-502-5p, reversed this effect. Hsa_circ_0032131 served as a competing endogenous RNA for miR-502-5p. Moreover, knockdown of hsa_circ_0032131 attenuated OA symptoms in vivo by inactivating the STAT3 signaling pathway. Thus, silencing of hsa_circ_0032131 inhibited the progression of OA by inactivating the miR-502-5p/PRDX3/Trx1/STAT3 axis, which highlights its potential as a therapeutic target for OA.

Circ_0001806 Promotes the Proliferation, Migration and Invasion of NSCLC Cells Through miR-1182/NOVA2 Axis

Background

Circular RNAs (circRNAs) are non-coding RNAs with a covalently closed loop. circRNAs affect the progression of diverse cancers. Nonetheless, circ_0001806 expression and function in non-small cell lung cancer (NSCLC) are undefined.

Methods

qRT-PCR was executed to examine circ_0001806, miR-1182 and NOVA2 mRNA expression levels in NSCLC tissues and cells. CCK-8, EdU, cell scratch test and Transwell assay were conducted to examine the viability, multiplication, migration and invasion of NSCLC cell lines H1650 and HCC827. The binding sites between circ_0001806 and miR-1182, miR-1182 and NOVA2 mRNA were predicted by the circular RNA Interactome and TargetScan databases, and the dual-luciferase reporter gene experiment was employed for verification. Western blot was implemented to examine NOVA2 expression.

Results

Circ_0001806 expression in NSCLC tissues and cell lines was substantially augmented, while miR-1182 expression was markedly decreased. Circ_0001806 facilitated the multiplication, migration and invasion of H1650 and HCC827 cells, while miR-1182 exerted the opposite effect. Circ_0001806 indirectly enhanced NOVA2 expression by specifically down-modulating miR-1182.

Conclusion

Circ_0001806 augments NOVA2 expression by targeting miR-1182 to enhance the multiplication, migration and invasion of NSCLC cells.

Therapeutic effects of blocking β-catenin against hepatocellular carcinoma-induced activation of inflammation, fibrosis and tumor invasion

Destructive effects of hepatocellular carcinoma (HCC) is enhanced by many cellular mechanisms including activation of fibrosis, inflammation and tumor invasion. Therefore, this study was conducted to investigate the therapeutic effects of iCRT14, β-catenin blocker, on HCC. In addition, the molecular effects of iCRT14 will be investigated on inflammation, fibrosis and tumor invasion pathways. After inducting HCC in rats, hepatic tissues were used for determination of the expression of β-catenin, nuclear factor (NF)κB, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, matrix metalloproteinase (MMP)9, transforming growth factor (TGF)-β1, fibroblast growth factor (FGF)-2 and integrin-β6. Hepatic tissues were stained with hematoxylin/eosin and with anti-Ki67. Results revealed that iCRT14 significantly increased the survival percent of HCC rats, reduced both α-fetoprotein and average number of nodules. In parallel, hepatic sections from HCC rats stained with hematoxylin/eosin revealed vacuolated cytoplasm and necrotic nodules, which were attenuated by treatment with iCRT14. Finally, treating HCC rats with iCRT14 resulted in reduction of the expression of NFκB, TNF-α, IL-1β, TGF-β1, MMP9, FGF-2 and integrin-β6. In conclusion, iCRT14 treatment exhibited antitumor effects against HCC through impairing β-catenin signaling pathway. iCRT14 suppressed liver tissue inflammation, fibrosis and angiogenesis, possibly via reducing expression of NFκB, TNF-α, IL-1β, TGF-β1, MMP-9, FGF-2.

Circular RNA CircCDYL Regulates Proliferation and Apoptosis in Non-Small Cell Lung Cancer Cells by Sponging miR-185-5p and Upregulating TNRC6A

Aim

A series of research reveal that circular RNA (circRNA) plays a vital role in regulating the development of tumor cells. In this research, we would explore the role and mechanism of circCDYL in non-small cell lung cancer (NSCLC).

Methods

RT-PCR was performed to detect the expression of circCDYL in NSCLC tissues, plasma, and cell lines. The tumor cell proliferation ability was evaluated by clone formation assay, and cell cycle determination. Flow cytometry was used to detect apoptosis in NSCLC cell lines. Western blot and RT-PCR were used to assess the expression of proteins and genes. Luciferase assay was performed to confirm the relationship of circRNA-miRNA-mRNA.

Results

The decreased level of circCDYL was observed in NSCLC patients' tissues and plasma, which was also downregulated in NSCLC cell lines. Forced expression of circCDYL inhibited cell viability, proliferation and induced apoptosis in A549 cells. Luciferase assay verified that circCDYL could bind with miR-185-5p and confirmed that TNRC6A was a downstream target of miR-185-5p. Overexpression of miR-185-5p or silencing of TNRC6A could inhibit the anti-tumor effect of circCDYL in A549 cells via regulating the ERK1/2 signal.

Conclusion

Here, we revealed that circCDYL inhibited proliferation and induced apoptosis in NSCLC cell lines via regulating ERK1/2 signal, and the mechanism of this progression may target miR-185-5p/TNRC6A, which provided a theoretical basis for clinical therapy.

The role of Krüppel-like factor 8 in cancer biology: Current research and its clinical relevance

Cancer is one of the leading causes of mortality worldwide, ranked second after heart disease. Despite recent advancements in diagnosis and treatment, there are still numerous problems associated with cancer progression, disease recurrence, and therapeutic resistance that are partially explored. Several studies have recently revealed that Krüppel-like factor 8 (KLF8) regulates transcription of genes linked with diverse biological processes, including proliferation, epithelial to mesenchymal transition (EMT), migration, invasion, and inflammation. KLF8 is expressed ubiquitously in mammalian cells, and its aberrant expression has been manifested with several cancer types. Earlier studies demonstrated the crucial role of KLF8 in DNA repair and resistance to apoptosis in numerous cancer types. Hence, studying the function of KLF8 from the perspective of cancer progression and therapy resistance would help develop a new therapeutic avenue. In this review, we summarize the clinical relevance of KLF8 expression in various malignancies, focusing on recent updates in EMT, cellular signaling, and cancer stem cells. We also address the contribution of KLF8 in development, DNA repair, chemoresistance, and its clinical utility as a predictive biomarker.