circNDUFB2 inhibits non-small cell lung cancer progression via destabilizing IGF2BPs and activating anti-tumor immunity

Crosstalk between m6A and coding/non-coding RNA in cancer and detection methods of m6A modification residues

N6-methyladenosine (m6A) is one of the most common and well-known internal RNA modifications that occur on mRNAs or ncRNAs. It affects various aspects of RNA metabolism, including splicing, stability, translocation, and translation. An abundance of evidence demonstrates that m6A plays a crucial role in various pathological and biological processes, especially in tumorigenesis and tumor progression. In this article, we introduce the potential functions of m6A regulators, including "writers" that install m6A marks, "erasers" that demethylate m6A, and "readers" that determine the fate of m6A-modified targets. We have conducted a review on the molecular functions of m6A, focusing on both coding and noncoding RNAs. Additionally, we have compiled an overview of the effects noncoding RNAs have on m6A regulators and explored the dual roles of m6A in the development and advancement of cancer. Our review also includes a detailed summary of the most advanced databases for m6A, state-of-the-art experimental and sequencing detection methods, and machine learning-based computational predictors for identifying m6A sites.

CircGNB1 facilitates the malignant phenotype of GSCs by regulating miR-515-5p/miR-582-3p-XPR1 axis

Glioma is the most common and aggressive primary malignant brain tumor. Circular RNAs (circRNAs) and RNA-binding proteins (RBPs) have been verified to mediate diverse biological behaviors in various human cancers. Therefore, the aim of this study was to explore a novel circRNA termed circGNB1 and elucidate relative molecular mechanism in functional phenotypes, which might be a potential prognostic biomarker and therapeutic approach for glioma. CircGNB1 was upregulated in glioma and closely associated with the low poor prognosis. Functional assays demonstrated that circGNB1 overexpression promoted glioma stem cells (GSCs) viability proliferation, invasion, and neurosphere formation. Mechanistically, circGNB1 upregulated the expression of oncogene XPR1 via sponging miR-515-5p and miR-582-3p. The following experiments proved XPR1 could promote the malignant phenotype of GSCs via upregulating IL6 expression and activating JAK2/STAT3 signaling. Moreover, the RNA binding protein IGF2BP3 could bind to and maintain the stability of circGNB1, thus promoting the effects of circGNB1 on GSCs. Our study reveals that circGNB1 plays a crucial role in promoting tumorigenesis and malignant progression in glioma, which provides a promising cancer biomarker.

The critical roles of m6A RNA methylation in lung cancer: from mechanism to prognosis and therapy

Lung cancer, a highly malignant disease, greatly affects patients' quality of life. N6-methyladenosine (m6A) is one of the most common posttranscriptional modifications of various RNAs, including mRNAs and ncRNAs. Emerging studies have demonstrated that m6A participates in normal physiological processes and that its dysregulation is involved in many diseases, especially pulmonary tumorigenesis and progression. Among these, regulators including m6A writers, readers and erasers mediate m6A modification of lung cancer-related molecular RNAs to regulate their expression. Furthermore, the imbalance of this regulatory effect adversely affects signalling pathways related to lung cancer cell proliferation, invasion, metastasis and other biological behaviours. Based on the close association between m6A and lung cancer, various prognostic risk models have been established and novel drugs have been developed. Overall, this review comprehensively elaborates the mechanism of m6A regulation in the development of lung cancer, suggesting its potential for clinical application in the therapy and prognostic assessment of lung cancer.

CircNFATC3 promotes the proliferation of gastric cancer through binding to IGF2BP3 and restricting its ubiquitination to enhance CCND1 mRNA stability

BACKGROUND

Insulin like growth factor II mRNA binding protein 3 (IGF2BP3) is an RNA binding protein with multiple roles in regulation of gene expression at the post-transcriptional level and is implicated in tumorigenesis and progression of numerous cancers including gastric cancer (GC). Circular RNAs (circRNAs) are a diverse endogenous noncoding RNA population that have important regulatory roles in cancer. However, circRNAs that regulate the expression of IGF2BP3 in GC is largely unknown.

METHODS

CircRNAs that bound to IGF2BP3 were screened in GC cells using RNA immunoprecipitation and sequencing (RIP-seq). The identification and localization of circular nuclear factor of activated T cells 3 (circNFATC3) were identified using Sanger sequencing, RNase R assays, qRT-PCR, nuclear-cytoplasmic fractionation and RNA-FISH assays. CircNFATC3 expression in human GC tissues and adjacent normal tissues were measured by qRT-PCR and ISH. The biological role of circNFATC3 in GC was confirmed by in vivo and in vitro experiments. Furthermore, RIP, RNA-FISH/IF, IP and rescue experiments were performed to uncover interactions between circNFATC3, IGF2BP3 and cyclin D1 (CCND1).

RESULTS

We identified a GC-associated circRNA, circNFATC3, that interacted with IGF2BP3. CircNFATC3 was significantly overexpressed in GC tissues and was positively associated with tumor volume. Functionally, the proliferation of GC cells decreased significantly after circNFATC3 knockdown in vivo and in vitro. Mechanistically, circNFATC3 bound to IGF2BP3 in the cytoplasm, which enhanced the stability of IGF2BP3 by preventing ubiquitin E3 ligase TRIM25-mediated ubiquitination, thereby enhancing the regulatory axis of IGF2BP3-CCND1 and promoting CCND1 mRNA stability.

CONCLUSIONS

Our findings demonstrate that circNFATC3 promotes GC proliferation by stabilizing IGF2BP3 protein to enhance CCND1 mRNA stability. Therefore, circNFATC3 is a potential novel target for the treatment of GC.

Exosomal lncRNA GAS5 promotes M1 macrophage polarization in allergic rhinitis via restraining mTORC1/ULK1/ATG13-mediated autophagy and subsequently activating NF-кB signaling

Macrophages are involved in the pathogenesis of allergic rhinitis (AR), but how these macrophages are polarized to M1 or M2 type is undetermined. Long non-coding RNA growth arrest specific transcript 5 (GAS5) is upregulated in exosomes isolated from nasal mucus of AR patients (AR-EXO) and aggravates nasal symptoms in AR mice. In the present study, we are aimed to elucidate the potential role of GAS5 in macrophage polarization during AR pathogenesis. An AR mice model was constructed. The potential function of GAS5 was evaluated by western blot, RNA immunoprecipitation (RIP), biotinylated RNA pull-down assay, co-immunoprecipitation (co-IP) assay, flow cytometry, enzyme-linked immunosorbent assay (ELISA) assay, and immunohistochemistry (IHC) staining. We found that GAS5 is upregulated in ovalbumin-treated human nasal epithelial cells RPMI 2650 (OVA-EXO) and nasal mucus of AR mice. OVA-EXO treatment or forced GAS5 expression promoted M1 macrophage polarization of peripheral blood monocytes (PB monocytes) and THP-1 macrophages in vitro. GAS5 overexpression aggravated the allergic nasal symptoms induced by OVA in AR mice and facilitated M1 macrophage polarization and allergic inflammation, while knockdown of GAS5 exhibited opposite effects in vivo. GAS5 activated NF-кB signaling via suppressing autophagy-dependent degradation of IKKα/β in macrophages. Furthermore, GAS5 acted as a scaffold to strengthen the interaction between mTORC1 and ULK1, thus impaired ULK1/ATG13-mediated autophagy via increasing mTORC1 activity. Finally, restored autophagy by ATG13 overexpression suppressed the effect of GAS5 on M1 macrophage polarization. In conclusion, these results suggested that exosomal transfer of GAS5 promoted M1 macrophage polarization via restraining mTORC1/ULK1/ATG13-mediated autophagy and subsequently activating NF-кB signaling in allergic rhinitis.

The short inverted repeats-induced circEXOC6B inhibits prostate cancer metastasis by enhancing the binding of RBMS1 and HuR

Circular RNAs (circRNAs) are a novel class of endogenous RNAs with a covalently closed loop structure. Many circRNAs have been found to participate in cancer progression. However, the detailed generation process, functions, and related mechanisms of circRNAs in prostate cancer (PCa) remain largely unknown. In the present study, we identified circEXOC6B, a novel suppressor in the metastasis of PCa. Functionally, circEXOC6B, originating from the exocyst complex component 6B (EXOC6B) gene, inhibited migration and invasion of PCa in vitro and in vivo. Mechanistically, by acting as a protein scaffold, circEXOC6B enhanced the binding of human RNA binding motif single strand interacting protein 1 (RBMS1) and human antigen R (HuR) and further increased A-kinase anchoring protein 12 (AKAP12) expression to inhibit PCa metastasis. Unlike previous studies, we found that one pair of short inverted repeats in flanking introns at least partly promoted the circularization of circEXOC6B. Our study presents a novel mechanism for the inhibitory role of circEXOC6B in PCa metastasis and provides new insight into the molecular process of circRNA generation.

A novel protein encoded by circUBE4B promotes progression of esophageal squamous cell carcinoma by augmenting MAPK/ERK signaling

Esophageal squamous carcinoma (ESCC) is a common malignant cancer. Although the non-coding roles of circRNAs in the pathogenesis of human tumors have been well studied, whether circRNAs participate in the progression of ESCC by encoding novel proteins remains unclear. In this study, we identified an overexpression circRNA with protein-coding ability in ESCC tissues, called circUBE4B, whose expression level is correlated with tumor size and tumor differentiation level of ESCC patients. Moreover, a higher level of circUBE4B in ESCC patients is correlated with a worse prognosis. Functionally, we found that circUBE4B promoted the proliferation of ESCC cells by encoding a novel cancer-promoting protein, circUBE4B-173aa. Mechanistically, the circUBE4B-173aa protein interacts with MAPK1 and promotes the phosphorylation level of MAPK1 to eventually activate MAPK/ERK signaling pathway. The xenograft model revealed that overexpression of circUBE4B-173aa in ESCC cells significantly promoted the growth of grafts. Our study provides new insights into the mechanism of circRNA in the development of ESCC and circUBE4B-173aa has the potential to serve as a biomarker and a novel therapeutic target for ESCC therapy.

Epigenetic regulation in the tumor microenvironment: molecular mechanisms and therapeutic targets

Over decades, researchers have focused on the epigenetic control of DNA-templated processes. Histone modification, DNA methylation, chromatin remodeling, RNA modification, and noncoding RNAs modulate many biological processes that are crucial to the development of cancers. Dysregulation of the epigenome drives aberrant transcriptional programs. A growing body of evidence suggests that the mechanisms of epigenetic modification are dysregulated in human cancers and might be excellent targets for tumor treatment. Epigenetics has also been shown to influence tumor immunogenicity and immune cells involved in antitumor responses. Thus, the development and application of epigenetic therapy and cancer immunotherapy and their combinations may have important implications for cancer treatment. Here, we present an up-to-date and thorough description of how epigenetic modifications in tumor cells influence immune cell responses in the tumor microenvironment (TME) and how epigenetics influence immune cells internally to modify the TME. Additionally, we highlight the therapeutic potential of targeting epigenetic regulators for cancer immunotherapy. Harnessing the complex interplay between epigenetics and cancer immunology to develop therapeutics that combine thereof is challenging but could yield significant benefits. The purpose of this review is to assist researchers in understanding how epigenetics impact immune responses in the TME, so that better cancer immunotherapies can be developed.

RIG-I-like receptors: Molecular mechanism of activation and signaling

During RNA viral infection, RIG-I-like receptors (RLRs) recognize the intracellular pathogenic RNA species derived from viral replication and activate antiviral innate immune response by stimulating type 1 interferon expression. Three RLR members, namely, RIG-I, MDA5, and LGP2 are homologous and belong to a subgroup of superfamily 2 Helicase/ATPase that is preferably activated by double-stranded RNA. RLRs are significantly different in gene architecture, RNA ligand preference, activation, and molecular functions. As switchable macromolecular sensors, RLRs' activities are tightly regulated by RNA ligands, ATP, posttranslational modifications, and cellular cofactors. We provide a comprehensive review of the structure and function of the RLRs and summarize the molecular understanding of sensing and signaling events during the RLR activation process. The key roles RLR signaling play in both anti-infection and immune disease conditions highlight the therapeutic potential in targeting this important molecular pathway.

The roles and mechanism of m6A RNA methylation regulators in cancer immunity

N⁶-methyladenosine (m⁶A), the most common internal modification in RNA, can be regulated by three types of regulators, including methyltransferases (writers), demethylases (erasers), and m⁶A binding proteins (readers). Recently, immunotherapy represented by immune checkpoint blocking has increasingly become an effective cancer treatment, and increasing shreds of evidence show that m⁶A RNA methylation affects cancer immunity in various cancers. Until now, there have been few reviews about the role and mechanism of m⁶A modification in cancer immunity. Here, we first summarized the regulation of m⁶A regulators on the expression of target messenger RNAs (mRNA) and their corresponding roles in inflammation, immunity response, immune process and immunotherapy in various cancer cells. Meanwhile, we described the roles and mechanisms of m⁶A RNA modification in tumor microenvironment and immune response by affecting the stability of non-coding RNA (ncRNA). Moreover, we also discussed the m⁶A regulators or its target RNAs which might be used as predictor of cancer diagnosis and prognosis, and shed light on the potentiality of m⁶A methylation regulators as therapeutic targets in cancer immunity.

Cigarette smoking, by accelerating the cell cycle, promotes the progression of non-small cell lung cancer through an HIF-1α-METTL3-m6A/CDK2AP2 axis

Cigarette smoking killed about 8 million people every year and promoted non-small cell lung cancer (NSCLC). We investigated the molecular mechanism of smoking-promoted NSCLC progression. Relative to non-smokers, NSCLC patients who were smokers had a higher tumor malignancy. For NSCLC cells, cigarette smoke extract (CSE) increased levels of HIF-1α, METTL3, Cyclin E1, and CDK2 and promoted the G1/S transition, which promoted cell proliferation. Down-regulation HIF-1α or METTL3 reversed these effects. meRIP-seq and RNA-seq revealed the m⁶A modification in Cyclin Dependent Kinase 2 Associated Protein 2 (CDK2AP2) mRNA as the key downstream target. Further, for NSCLC cells exposed to CSE, HIF-1α activated METTL3 transcription. Xenografts in nude mice demonstrated that HIF-1α via METTL3 participated in tumor growth. In NSCLC tissues of smokers, protein levels of HIF-1α and METTL3 were higher, and levels of CDK2AP2 were lower. In conclusion, HIF-1α via METTL3 regulation of the m⁶A modification of CDK2AP2 mRNA drives smoking-induced progression of NSCLC through promoting cell proliferation. This is a previously unknown molecular mechanism for smoking-induced NSCLC progression. The results have potential value for treatment of NSCLC, especially for patients who smoke.

Splicing factor SNRPA associated with microvascular invasion promotes hepatocellular carcinoma metastasis through activating NOTCH1/Snail pathway and is mediated by circSEC62/miR-625-5p axis

Microvascular invasion (MVI) is a crucial risk factor related to the metastasis of hepatocellular carcinoma (HCC), but the underlying mechanisms remain to be revealed. Characterizing the inherent mechanisms of MVI may aid in the development of effective treatment strategies to improve the prognosis of HCC patients with metastasis. Through the Gene Expression Omnibus (GEO) database, we identified that small nuclear ribonucleoprotein polypeptide A (SNRPA) was related to MVI in HCC. SNRPA was overexpressed in MVI-HCC and correlated with poor patient survival. Mechanistically, SNRPA promoted the epithelial-mesenchymal transition (EMT)-like process for HCC cells to accelerate metastasis by activating the NOTCH1/Snail pathway in vitro and in vivo. Importantly, circSEC62 upregulated SNRPA expression in HCC cells via miR-625-5p sponging. Taking these results together, our study identified a novel regulatory mechanism among SNRPA, miR-625-5p, circSEC62 and the NOTCH1/Snail pathway in HCC, which promoted metastasis of HCC and may provide effective suggestions for improving the prognosis of HCC patients with metastasis.

EIF4A3-induced circular RNA SCAP facilitates tumorigenesis and progression of non-small-cell lung cancer via miR-7/SMAD2 signaling

The eukaryotic translation initiation factor 4A (eIF4A) family determines transcription efficiency by directly binding to precursor RNAs. One member, EIF4A3, modulates the expression of circRNAs. Circular RNA SCAP (circSCAP), a newly found circRNA, has been implicated in atherosclerosis. Yet, how circSCAP regulates cancer development and progression remains understudied. Here, we investigated the function of circSCAP and the molecular mechanism in the tumorigenesis and progression of non-small-cell lung cancer (NSCLC). CircSCAP was upregulated in both NSCLC tissues and cell lines and was mainly located in the cytoplasm. CircSCAP expression was promoted by EIF4A3, which was associated with poor prognosis in patients with NSCLC. CircSCAP sponged miR-7 to upregulate small mothers against decapentaplegic 2 (SMAD2). CircSCAP knockdown undermined cell proliferation, migration, and invasion abilities in NSCLC cell lines (SPCA1 and A549), which was rescued by either inhibiting miR-7 or overexpressing SMAD2. Moreover, circSCAP knockdown upregulated E-cadherin, while downregulating N-cadherin, Vimentin, and MMP9 in SPCA1 and A549 cells, which were abolished by either inhibiting miR-7 or overexpressing SMAD2. Additionally, miR-7 was markedly downregulated, whereas SMAD2 was significantly upregulated in NSCLC tissues. MiR-7 expression was inversely correlated with circSCAP and SMAD2 expression in NSCLC tissues. In conclusion, this study demonstrates that circSCAP is significantly upregulated in NSCLC cell lines and tissues and elucidates that circSCAP facilitates NSCLC progression by sponging miR-7 and upregulating SMAD2. The study provides a novel molecular target for early diagnosis and treatment of NSCLC.

LncRNA DGUOK-AS1 facilitates non-small cell lung cancer growth and metastasis through increasing TRPM7 stability via m6A modification

BACKGROUND

N6-methyladenosine (m6A) modification plays key roles in tumor progression. LncRNA deoxyguanosine kinase antisense RNA 1 (DGUOK-AS1) has been reported as a promoter in tumors, but its role and mechanism in non-small cell lung cancer (NSCLC) development remain uncertain.

METHODS

Cell proliferation, migration, invasion and angiogenesis were investigated via CCK-8, colony formation, transwell, and tube formation assays, respectively. The location of DGUOK-AS1 was detected via FISH assay. The interaction relationship among DGUOK-AS1, IGF2BP2 and TRPM7 was confirmed by RIP and MeRIP assays. The effects of DGUOK-AS1 on NSCLC growth and metastasis in vivo were investigated using xenograft and pulmonary metastatic models.

RESULTS

DGUOK-AS1 was upregulated in NSCLC. DGUOK-AS1 silencing inhibited NSCLC cell proliferation, migration, invasion and angiogenesis. DGUOK-AS1 was mostly expressed in cytoplasm, and positively regulated IGF2BP2. METTL3/IGF2BP2 axis could increase TRPM7 mRNA stability in m6A-dependent manner. TRPM7 overexpression reversed the inhibitive function of DGUOK-AS1 silencing on NSCLC development. DGUOK-AS1 knockdown suppressed NSCLC cell growth and metastasis in nude mice.

CONCLUSION

DGUOK-AS1 silencing restrains NSCLC cell growth and metastasis through decreasing TRPM7 stability via regulation of the METTL3/IGF2BP2-mediated m6A modification.

Circular RNA ARHGAP5 inhibits cisplatin resistance in cervical squamous cell carcinoma by interacting with AUF1

Cervical squamous cell carcinoma (CSCC) is one of the leading causes of cancer death in women worldwide. Patients with advanced cervical carcinoma always have a poor prognosis once resistant to cisplatin due to the lack of effective treatment. It is urgent to investigate the molecular mechanisms of cisplatin resistance. Circular RNAs (circRNAs) are known to exert their regulatory functions in a series of malignancies. However, their effects on CSCC remain to be elucidated. Here, we found that cytoplasmic circARHGAP5, derived from second and third exons of the ARHGAP5 gene, was downregulated in cisplatin-resistant tissues compared with normal cervix tissues and untreated cervical cancer tissues. In addition, experiments from overexpression/knockdown cell lines revealed that circARHGAP5 could inhibit cisplatin-mediated cell apoptosis in CSCC cells both in vitro and in vivo. Mechanistically, circARHGAP5 interacted with AU-rich element RNA-binding protein (AUF1) directly. Overexpression of AUF1 could also inhibit cell apoptosis mediated by cisplatin. Furthermore, we detected the potential targets of AUF1 related to the apoptotic pathway and found that bcl-2-like protein 11 (BIM) was not only negatively regulated by AUF1 but positively regulated by circARHGAP5, which indicated that BIM mRNA might be degraded by AUF1 and thereby inhibited tumor cell apoptosis. Collectively, our data indicated that circARHGAP5 directly bound to AUF1 and prevented AUF1 from interacting with BIM mRNA, thereby playing a pivotal role in cisplatin resistance in CSCC. Our study provides insights into overcoming cancer resistance to cisplatin treatment.

Inhibition of circular RNA ASPH reduces the proliferation and promotes the apoptosis of hepatic stellate cells in hepatic fibrosis

Circular RNAs (circRNAs) are a newly identified form of non-coding RNA that play a crucial role in various pathological processes. However, the expression profile and function of circRNAs in hepatic fibrosis (HF) remain largely unknown. In this study, we showed that a novel circRNA ASPH (circASPH) mediates HF by targeting the miR-139-5p/Notch1 axis. We investigated the expression profile of circRNAs in hepatocyte exosomes of mice with HF using circRNA-sequencing and found significant upregulation of circASPH. Loss- and gain-of-function analysis of circASPH was performed to assess its role in HF. Furthermore, we performed luciferase reporter assay, RNA pull-down, and fluorescence in situ hybridization analyses and confirmed that circASPH directly binds to miR-139-5p. We also found that circASPH was upregulated in liver fibrogenesis. Downregulation of circASPH expression inhibited hepatic stellate cell (HSC) activation and proliferation, induced apoptosis, and attenuated mouse liver fibrogenic injury. Mechanistically, circASPH directly targeted miR-139-5p to regulate the expression of Notch1 in HF. Thus, downregulation of circASPH may suppress the activation of HSCs and HF through the circASPH/miR-139-5p/Notch1 axis. Our findings indicated that circASPH may be a potential biomarker for HF diagnosis and therapy.

CircSCN8A suppresses malignant progression and induces ferroptosis in non-small cell lung cancer by regulating miR-1290/ACSL4 axis

Circular RNAs (CircRNAs) are reported to exert vital regulatory roles in the occurrence and development of various human malignancies, including non-small cell lung cancer (NSCLC). Bioinformatics methods identified the down-regulation of circSCN8A (circBase ID: hsa_circ_0026337) in NSCLC tissues. However, its biological functions and molecular mechanisms in NSCLC remain unknown. In this study, we found that circSCN8A expression was down-regulated in NSCLC tissues and cells. Low circSCN8A expression was positively associated with aggressive clinicopathological characteristics and poor prognosis in NSCLC patients. CircSCN8A suppressed cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) in vitro and blocked tumor growth in vivo. Moreover, circSCN8A promoted cell ferroptosis in NSCLC. Mechanistically, circSCN8A acted as a competing endogenous RNA (ceRNA) by sponging miR-1290 to enhance the expression of long-chain acyl-CoA synthetase-4 (ACSL4). Furthermore, the knockdown of ACSL4 or overexpression of miR-1290 reversed the effect of circSCN8A on facilitating ferroptosis and inhibiting cell proliferation and metastasis. In summary, circSCN8A represses cell proliferation and metastasis in NSCLC by regulating the miR-1290/ACSL4 axis to induce ferroptosis. Thus, circSCN8A may represent a promising therapeutic target against NSCLC.

Regulation of NcRNA-protein binding in diabetic foot

Non-coding RNA (ncRNA) is a special type of RNA transcript that makes up more than 90 % of the human genome. Although ncRNA typically does not encode proteins, it indirectly controls a wide range of biological processes, including cellular metabolism, development, proliferation, transcription, and post-transcriptional modification. NcRNAs include small interfering RNA (siRNA), PIWI-interacting RNA (piRNA), tRNA-derived small RNA (tsRNA), etc. The most researched of these are miRNA, lncRNA, and circRNA, which are crucial regulators in the onset of diabetes and the development of associated consequences. The ncRNAs indicated above are linked to numerous diabetes problems by binding proteins, including diabetic foot (DF), diabetic nephropathy, diabetic cardiomyopathy, and diabetic peripheral neuropathy. According to recent studies, Mir-146a can control the AKAP12 axis to promote the proliferation and migration of diabetic foot ulcer (DFU) cells, while lncRNA GAS5 can activate HIF1A/VEGF pathway by binding to TAF15 to promote DFU wound healing. However, there are still many unanswered questions about the mechanism of action of ncRNAs. In this study, we explored the mechanism and new progress of ncRNA-protein binding in DF, which can provide help and guidance for the application of ncRNA in the early diagnosis and potential targeted intervention of DFU.

Regulation of CD8+ T cells infiltration and immunotherapy by circMGA/HNRNPL complex in bladder cancer

The limited success of immunotherapies targeting immune checkpoint inhibitors is largely ascribed to the lack of infiltrating CD8+ T lymphocytes. Circular RNAs (circRNAs) are a novel type of prevalent noncoding RNA that have been implicated in tumorigenesis and progression, while their roles in modulating CD8+ T cells infiltration and immunotherapy in bladder cancer have not yet been investigated. Herein, we uncover circMGA as a tumor-suppressing circRNA triggering CD8+ T cells chemoattraction and boosting the immunotherapy efficacy. Mechanistically, circMGA functions to stabilize CCL5 mRNA by interacting with HNRNPL. In turn, HNRNPL increases the stability of circMGA, forming a feedback loop that enhances the function of circMGA/HNRNPL complex. Intriguingly, therapeutic synergy between circMGA and anti-PD-1 could significantly suppress xenograft bladder cancer growth. Taken together, the results demonstrate that circMGA/HNRNPL complex may be targetable for cancer immunotherapy and the study advances our understanding of the physiological roles of circRNAs in antitumor immunity.

circNEIL3 inhibits tumor metastasis through recruiting the E3 ubiquitin ligase Nedd4L to degrade YBX1

Distant metastasis is a major contributor to cancer-related mortality. However, the role of circRNAs in this process remains unclear. Herein, we profiled the circRNA expression in a cohort of 68 colorectal carcinoma (CRC) primary tumors and their paired liver metastatic lesions. By overlapping with the TGFβ-responsive circRNAs, circNEIL3 (hsa_circ_0001460) was identified as a TGFβ-repressive and metastasis-related circRNA. Functionally, circNEIL3 effectively inhibited tumor metastasis in both and in vivo and in vivo models of various cancer types. Mechanistically, circNEIL3 exerts its metastasis-repressive function through its direct interaction with oncogenic protein, Y-box-binding protein 1 (YBX1), which consequently promotes the Nedd4L-mediated proteasomal degradation of YBX1. Importantly, circNEIL3 expression was negatively correlated to YBX1 protein level and metastatic tendency in CRC patient samples. Collectively, our findings indicate the YBX1-dependent antimetastatic function of circNEIL3 and highlight the potential of circNEIL3 as a biomarker and therapeutic option in cancer treatment.

Role of mitochondrial stress and the NLRP3 inflammasome in lung diseases

BACKGROUND

As an organelle essential for intracellular energy supply, mitochondria are involved in intracellular metabolism and inflammation, and cell death. The interaction of mitochondria with the NLRP3 inflammasome in the development of lung diseases has been extensively studied. However, the exact mechanism by which mitochondria mediate the activation of the NLRP3 inflammasome and trigger lung disease is still unclear.

METHODS

The literatures related to mitochondrial stress, NLRP3 inflammasome and lung diseases were searched in PubMed.

RESULTS

This review aims to provide new insights into the recently discovered mitochondrial regulation of the NLRP3 inflammasome in lung diseases. It also describes the crucial roles of mitochondrial autophagy, long noncoding RNA, micro RNA, altered mitochondrial membrane potential, cell membrane receptors, and ion channels in mitochondrial stress and regulation of the NLRP3 inflammasome, in addition to the reduction of mitochondrial stress by nuclear factor erythroid 2-related factor 2 (Nrf2). The effective components of potential drugs for the treatment of lung diseases under this mechanism are also summarized.

CONCLUSION

This review provides a resource for the discovery of new therapeutic mechanisms and suggests ideas for the development of new therapeutic drugs, thus promoting the rapid treatment of lung diseases.

Circular RNA circDLG1 (has_circ_0068706) functions as an oncogene in nonsmall cell lung cancer through regulating AKT/mTOR signaling and direct binding to miR-144

Nonsmall cell lung cancer (NSCLC) is a major subtype of lung cancer, causing substantial cancer-related deaths worldwide. However, the molecular basis of NSCLC development and progression remains understudied. Recently, a circular RNA, circDLG1, has been implicated in carcinogenesis and cancer metastasis. Yet, how circDLG1 affects NSCLC progression has not been reported. Here this study aims to elucidate the role of circDLG1 in NSCLC. First, we found that circDLG1 was significantly upregulated in both the GEO dataset and NSCLC tissues. Next, we silenced the expression of circDLG1 in NSCLC cell lines. Knockdown of circDLG1 upregulated miR-144 and downregulated Protein kinase B (AKT)/mechanistic target of rapamycin (mTOR), resulting in suppression of the proliferation activity and metastasis ability of NSCLC. In addition, circDLG1 knockdown significantly decreased the expression of the mesenchymal markers, proliferating cell nuclear antigen (PCNA), and N-cadherin, while increasing the expression level of E-cadherin. In conclusion, we demonstrate that circDLG1 promotes the pathogenesis and progression of NSCLC by regulating the miR-144/AKT/mTOR signaling axis, providing potential diagnostic and therapeutic targets for designing innovative treatment strategies.

Circular RNAs: implications of signaling pathways and bioinformatics in human cancer

Circular RNAs (circRNAs) form a class of endogenous single-stranded RNA transcripts that are widely expressed in eukaryotic cells. These RNAs mediate post-transcriptional control of gene expression and have multiple functions in biological processes, such as transcriptional regulation and splicing. They serve predominantly as microRNA sponges, RNA-binding proteins, and templates for translation. More importantly, circRNAs are involved in cancer progression, and may serve as promising biomarkers for tumor diagnosis and therapy. Although traditional experimental methods are usually time-consuming and laborious, substantial progress has been made in exploring potential circRNA-disease associations by using computational models, summarized signaling pathway data, and other databases. Here, we review the biological characteristics and functions of circRNAs, including their roles in cancer. Specifically, we focus on the signaling pathways associated with carcinogenesis, and the status of circRNA-associated bioinformatics databases. Finally, we explore the potential roles of circRNAs as prognostic biomarkers in cancer.

Circular RNAs: New layer of complexity evading breast cancer heterogeneity

Advances in high-throughput sequencing techniques and bioinformatic analysis have refuted the "junk" RNA hypothesis that was claimed against non-coding RNAs (ncRNAs). Circular RNAs (circRNAs); a class of single-stranded covalently closed loop RNA molecules have recently emerged as stable epigenetic regulators. Although the exact regulatory role of circRNAs is still to be clarified, it has been proven that circRNAs could exert their functions by interacting with other ncRNAs or proteins in their own physiologically authentic environment, regulating multiple cellular signaling pathways and other classes of ncRNAs. CircRNAs have also been reported to exhibit a tissue-specific expression and have been associated with the malignant transformation process of several hematological and solid malignancies. Along this line of reasoning, this review aims to highlight the importance of circRNAs in Breast Cancer (BC), which is ranked as the most prevalent malignancy among females. Notwithstanding the substantial efforts to develop a suitable anticancer therapeutic regimen against the heterogenous BC, inter- and intra-tumoral heterogeneity have resulted in an arduous challenge for drug development research, which in turn necessitates the investigation of other markers to be therapeutically targeted. Herein, the potential of circRNAs as possible diagnostic and prognostic biomarkers have been highlighted together with their possible application as novel therapeutic targets.

The roles of N6-methyladenosine and its target regulatory noncoding RNAs in tumors: classification, mechanisms, and potential therapeutic implications

N6-methyladenosine (m6A) is one of the epigenetic modifications of RNA. The addition of this chemical mark to RNA molecules regulates gene expression by affecting the fate of the RNA molecules. This posttranscriptional RNA modification is reversible and regulated by methyltransferase "writers" and demethylase "erasers". The fate of m6A-modified RNAs depends on the function of different "readers" that recognize and bind to them. Research on m6A methylation modification has recently increased due to its important role in regulating cancer progression. Noncoding RNAs (ncRNAs) are a class of RNA molecules that are transcribed from the genome but whose roles have been overlooked due to their lack of well-defined potential for translation into proteins or peptides. However, this misconception has now been completely overturned. ncRNAs regulate various diseases, especially tumors, and it has been confirmed that they play either tumor-promoting or tumor-suppressing roles in almost all types of tumors. In this review, we discuss the m6A modification of different types of ncRNA and summarize the mechanisms involved. Finally, we discuss the progress of research on clinical treatment and discuss the important significance of the m6A modification of ncRNAs in the clinical treatment of tumors.

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-N4BP2L2 enhances mitochondrial function in non-small cell lung cancer cells through regulating the miR-135a-5p/ARL5B axis

Non-small cell lung cancer (NSCLC) is the main histological subtype of lung cancer with a high incidence and mortality. Circular RNAs (circRNAs) exert vital functions in various cancers by acting as a sponge of miRNAs to abolish their inhibitory effect on target genes. This study aims to explore the biological function of circRNA NEDD4 binding protein 2 like 2 (circ-N4BP2L2) in NSCLC. We found that circ-N4BP2L2 was upregulated in NSCLC tissues and cells by using RT-qPCR. A549 cells were transfected with pcDNA-circN4BP2L2 or sh-circN4BP2L2 to obtain circN4BP2L2-overexpressed or -silenced cells, and then cell proliferation, invasion and apoptosis were determined. The results showed that knockdown of circ-N4BP2L2 repressed cell proliferation, invasion as well as mitochondrial function, and promoted cell apoptosis; while overexpression of circ-N4BP2L2 resulted in the opposite results. Mechanistically, the targeting correlations between miR-135a-5p and circ-N4BP2L2 or ADP-ribosylation factorlike 5B (ARL5B) were confirmed by using dual luciferase reporter, RNA pull-down and RNA immunoprecipitation assays. In addition, we found that circ-N4BP2L2 could promote the expression of ARL5B by serving as a sponge of miR-135a-5p. Moreover, rescue assays revealed that silencing miR-135a-5p or overexpressing ARL5B was able to abate the effects of circ-N4BP2L2 knockdown on malignant phenotypes and mitochondrial function of A549 cells. Finally, tumorigenicity assay demonstrated that circ-N4BP2L2 facilitated NSCLC tumor growth in vivo. Taken together, circ-N4BP2L2 enhanced NSCLC progression via the miR-135a-5p/ARL5B axis, which may provide a novel therapeutic target of NSCLC.

Increased levels of N6-methyladenosine in peripheral blood RNA: a perspective diagnostic biomarker and therapeutic target for non-small cell lung cancer

OBJECTIVES

Due to lack of effective biomarkers for non-small cell lung cancer (NSCLC), many patients are diagnosed at an advanced stage, which leads to poor prognosis. Dysregulation of N6-methyladenosine (m⁶A) RNA contributes significantly to tumorigenesis and tumor progression. However, the diagnostic value of m⁶A RNA status in peripheral blood to screen NSCLC remains unclear.

METHODS

Peripheral blood samples from 152 NSCLC patients and 64 normal controls (NCs) were applied to assess the m⁶A RNA levels. Bioinformatics and qRT-PCR analysis were performed to identify the specific immune cells in peripheral blood cells and investigate the mechanism of the alteration of m⁶A RNA levels.

RESULTS

Robust elevation of m⁶A RNA levels of peripheral blood cells was exhibited in the NSCLC group. Moreover, the m⁶A levels increased as NSCLC progressed, and reduced after treatment. The m⁶A levels contained area under the curve (AUC) was 0.912, which was remarkably greater than the AUCs for CEA (0.740), CA125 (0.743), SCC (0.654), and Cyfra21-1 (0.730). Furthermore, the combination of these traditional biomarkers with m⁶A levels elevated the AUC to 0.970. Further analysis established that the expression of m⁶A erasers FTO and ALKBH5 were both markedly reduced and negatively correlated with m⁶A levels in peripheral blood of NSCLC. Additionally, GEO database and flow cytometry analysis implied that FTO and ALKBH5 attributes to peripheral CD4⁺ T cells proportion and activated the immune functions of T cells.

CONCLUSIONS

These findings unraveled that m⁶A RNA of peripheral blood immune cells was a prospective biomarker for the diagnosis of NSCLC.

Overview of m6A and circRNAs in human cancers

N⁶-methyladenosine (m⁶A), the richest post-transcriptional modification of RNA in eukaryotic cells, is dynamically installed/uninstalled by the RNA methylase complex ("writer") and demethylase ("eraser") and recognized by the m⁶A-binding protein ("reader"). M⁶A modification on RNA metabolism involves maturation, nuclear export, translation and splicing, thereby playing a critical role in cellular pathophysiology and disease processes. Circular RNAs (circRNAs) are a class of non-coding RNAs with a covalently closed loop structure. Due to its conserved and stable properties, circRNAs could participate in physiological and pathological processes through unique pathways. Despite the recent discovery of m⁶A and circRNAs remains in the initial stage, research has shown that m⁶A modifications are widespread in circRNAs and regulates circRNA metabolism, including biogenesis, cell localization, translation, and degradation. In this review, we describe the functional crosstalk between m⁶A and circRNAs, and illustrate their roles in cancer development. Moreover, we discuss the potential mechanisms and future research directions of m⁶A modification and circRNAs.

m6A-modified circRNA MYO1C participates in the tumor immune surveillance of pancreatic ductal adenocarcinoma through m6A/PD-L1 manner

Emerging evidence indicates the critical roles of N⁶-methyladenosine (m⁶A) modification in human cancers. Herein, our work reported that a novel m⁶A-modified circRNA from the MYO1C gene, circMYO1C, upregulated in the pancreatic ductal adenocarcinoma (PDAC). Our findings demonstrated that circMYO1C is highly expressed in PDAC tissues. Functionally, circMYO1C promoted the proliferation and migration of PDAC cells in vitro and its silencing reduced the tumor growth in vivo. Mechanistically, circMYO1C cyclization was mediated by m⁶A methyltransferase METTL3. Moreover, methylated RNA immunoprecipitation sequencing (MeRIP-seq) unveiled the remarkable m⁶A modification on PD-L1 mRNA. Moreover, circMYO1C targeted the m⁶A site of PD-L1 mRNA to enhance its stability by cooperating with IGF2BP2, thereby accelerating PDAC immune escape. In conclusion, these findings highlight the oncogenic role of METTL3-induced circMYO1C in PDAC tumorigenesis via an m⁶A-dependent manner, inspiring a novel strategy to explore PDAC epigenetic therapy.

CircFOXP1 alleviates brain injury after acute ischemic stroke by regulating STAT3/apoptotic signaling

According to previous studies, circular RNAs (circRNAs) are involved in multiple pathological processes of acute ischemic stroke (AIS). However, the relationship between circFOXP1 and IS has not yet been reported. Here, we found that circFOXP1 expression was significantly decreased in the peripheral blood of AIS patients compared to controls and was associated with the severity and prognosis of AIS. Functionally, knockdown and overexpression of circFOXP1 promoted and inhibited apoptotic signaling, respectively, following oxygen-glucose deprivation/reperfusion (OGD/R) treatment in vitro. Adeno-associated virus (AAV)-mediated circFOXP1 overexpression attenuated neurological deficits and improved functional recovery after transient middle cerebral artery occlusion (tMCAO) treatment in vivo. Mechanistically, decreased QKI expression inhibited circFOXP1 biogenesis under hypoxic conditions. Decreased circFOXP1 expression accelerated signal transducer and activator of transcription 3 (STAT3) protein degradation by binding to and increasing STAT3 protein ubiquitination, ultimately aggravating brain injury after cerebral ischemia by activating apoptotic signaling. In summary, our study is the first to reveal that circFOXP1 alleviates brain injury after cerebral ischemia by regulating STAT3/apoptotic signaling, which provides a potentially novel therapeutic target for AIS.

Recent Progress on Circular RNAs in the Development of Skeletal Muscle and Adipose Tissues of Farm Animals

Circular RNAs (circRNAs) are a highly conserved and specifically expressed novel class of covalently closed non-coding RNAs. CircRNAs can function as miRNA sponges, protein scaffolds, and regulatory factors, and play various roles in development and other biological processes in mammals. With the rapid development of high-throughput sequencing technology, thousands of circRNAs have been discovered in farm animals; some reportedly play vital roles in skeletal muscle and adipose development. These are critical factors affecting meat yield and quality. In this review, we have highlighted the recent advances in circRNA-related studies of skeletal muscle and adipose in farm animals. We have also described the biogenesis, properties, and biological functions of circRNAs. Furthermore, we have comprehensively summarized the functions and regulatory mechanisms of circRNAs in skeletal muscle and adipose development in farm animals and their effects on economic traits such as meat yield and quality. Finally, we propose that circRNAs are putative novel targets to improve meat yield and quality traits during animal breeding.

circPHF16 suppresses prostate cancer metastasis via modulating miR-581/RNF128/Wnt/β-catenin pathway

Circular RNAs (circRNAs) have been recognized as important regulators in tumorigenesis. However, the specific role of circRNAs in prostate cancer is still largely unknown. Here, we identified that circPHF16 was downregulated in prostate cancer (PCa) tissues compared with normal tissues. Functionally, circPHF16 restrained prostate cancer metastasis both in vivo and in vitro. Mechanistically, circPHF16 directly interacted with miR-581, leading to the downregulation of ring finger protein 128 (RNF128) and inhibiting the metastatic ability of PCa. Furthermore, circPHF16-dependent upregulation of RNF128 inactivated Wnt/β-catenin signaling. In total, our findings revealed that circPHF16 suppressed prostate cancer metastasis through the circPHF16/miR-581/Wnt/β-catenin pathways.

circRNA_0067717 promotes paclitaxel resistance in nasopharyngeal carcinoma by acting as a scaffold for TRIM41 and p53

PURPOSE

Circular RNAs (circRNAs) play important roles in tumour progression. This study aimed to explore the mechanism of hsa_circ_0067717 (termed circRNA_0067717) promoting paclitaxel resistance in nasopharyngeal carcinoma (NPC).

METHODS

We assayed CNE-1 and HNE-2 parental cell lines and the corresponding paclitaxel-resistant NPC cell lines using circRNA microarrays. RNA pull-down assay, RNA immunoprecipitation, and RNA fluorescence in situ hybridization were used to identify the molecular mechanisms.

RESULTS

Here, we confirm that circRNA_0067717 is significantly upregulated in NPC paclitaxel-resistant cells and is associated with paclitaxel resistance in NPC. Mechanistically, circRNA_0067717 functions as a scaffold for TRIM41 protein (a ubiquitin E3 ligase) and p53 protein. In nasopharyngeal carcinoma paclitaxel-resistant cells, the highly expressed circRNA_0067717 can bind to more TRIM41 and p53 protein, promoting TRIM41-induced p53 ubiquitination and degradation, resulting in a decrease in p53 protein level. Moreover, the 1-176 nt area of circRNA_0067717 and the 301-425 nt region of circRNA_0067717 are the binding sites for p53 and TRIM41, respectively. The resistance of NPC cells to paclitaxel can be reduced by blocking these binding regions of circRNA_0067717.

CONCLUSION

We demonstrate that circRNA_0067717 acts as a scaffold for TRIM41 and p53, enhancing paclitaxel chemoresistance in NPC by promoting TRIM41-induced p53 degradation via ubiquitination.

ncRNAs mediated RPS6KA2 inhibits ovarian cancer proliferation via p38/MAPK signaling pathway

Background

Ovarian cancer is the most lethal gynecology malignancy in the world, therefore, research on the molecular biological mechanism of ovarian cancer tumorigenesis and progression has received widespread attention.

Methods

We identified RPS6KA2 as the prognosis-related gene of ovarian cancer from TCGA, GSE26712 and GSE26193 database via bioinformatic analysis. qRT-PCR and western blot detected the differential expression of RPS6KA2 in normal ovaries and ovarian cancer tissues. The biological functions of RPS6KA2 were verified by in vitro and in vivo. GSEA analysis was used to select candidate signaling pathway of RPS6KA2 which was further verified by western blot. The possible binding sites of RPS6KA2 with miRNAs and circRNAs were predicted by bioinformatics analysis, and then a circRNA-miRNA-mRNA interaction network was constructed.

Results

We found the expression of RPS6KA2 was down-regulated in ovarian cancer tissues. Overexpression of RPS6KA2 could suppress cell proliferation, whereas knockdown of RPS6KA2 had the opposite effects on proliferation. GSEA analysis showed that the MARK signaling pathway was closely associated with RPS6KA2. Bioinformatics analysis and dual-luciferase reporter assay showed that RPS6KA2 was regulated with miR-19a-3p, miR-106a-5p and miR-519d-3p. Further analysis showed that circFAM169A was the common ceRNA of miR-19a-3p, miR-106a-5p and miR-519d-3p. Dual-luciferase reporter assay showed the relationship of circFAM169A and miR-106a-5p and miR-519d-3p. After network analysis, one circRNA-miRNA-mRNA axis (circFAM169A/miR-106a-5p, miR-519d-3p/RPS6KA2) was identified.

Conclusions

We demonstrated that circFAM169A/miR-106a-5p, miR-519d-3p mediated low expression of RPS6KA2 could affect the proliferation of ovarian cancer cells via p38/MAPK signaling pathway.

N6-methyladenosine writer METTL3 accelerates the sepsis-induced myocardial injury by regulating m6A-dependent ferroptosis

Ferroptosis is an iron-dependent and phospholipid peroxidation-mediated cell death, which has been identified to be involved in sepsis-induced injury. However, the in-depth molecular mechanisms of N⁶-methyladenosine (m⁶A) and ferroptosis on sepsis-induced myocardial injury are still unclear. Here, in the septic myocardial injury, m⁶A methyltransferase METTL3 level and methylation level high-expressed in lipopolysaccharide (LPS)-induced cardiomyocytes (H9C2). Functionally, METTL3 silencing repressed the ferroptosis phenotype induced by LPS. Mechanistically, METTL3-mediated m⁶A methylation on solute carrier family 7 member 11 (SLC7A11) empowered its mRNA with high methylation level. Moreover, YTHDF2 directly bound to the m⁶A modification sites of SLC7A11 to mediate the mRNA degradation. The m⁶A modified SLC7A11 mRNA was recognized by YTHDF2, which promoted the decay of SLC7A11 mRNA, consequently up-regulating ferroptosis in sepsis-induced myocardial injury. Together, these findings establish a role of METTL3 in the ferroptosis of LPS-induced cardiomyocytes, and provide potential therapeutic target to treat the sepsis-induced myocardial injury.

The significance of the crosstalk between ubiquitination or deubiquitination and ncRNAs in non-small cell lung cancer

Lung cancer (LC) remains the leading cause of cancer-related deaths worldwide, with extremely high morbidity and mortality rates. Non-small cell lung cancer (NSCLC) is the most critical type of LC. It seriously threatens the life and health of patients because of its early metastasis, late clinical symptoms, limited early screening methods, and poor treatment outcomes. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs), participate in cell proliferation, metastasis, and chemoresistance. Several previous studies have proven that ncRNAs are vital regulators of tumorigenesis. Ubiquitination plays the most crucial role in protein post-translational modification (PTM). Deubiquitination and ubiquitination form a homeostasis. In summary, ubiquitination and deubiquitination play essential roles in mediating the degradation or overexpression of a range of crucial proteins in various cancers. A growing number of researchers have found that interactions between ncRNAs and ubiquitination (or deubiquitination) play a crucial role in NSCLC. This review presents several typical examples of the important effects of ncRNAs and ubiquitination (or deubiquitination) in NSCLC, aiming to provide more creative ideas for exploring the diagnosis and treatment of NSCLC.

The U2AF65/circNCAPG/RREB1 feedback loop promotes malignant phenotypes of glioma stem cells through activating the TGF-β pathway

Glioma is the most aggressive and common malignant neoplasms in human brain tumors. Numerous studies have showed that glioma stem cells (GSCs)drive the malignant progression of gliomas. Recent studies have revealed that circRNAs can maintain stemness and promote malignant progression of glioma stem cells. We used bioinformatics analysis to identify circRNAs and potential RNA-binding proteins (RBPs) in glioma. qRT-PCR, western blotting, RNA FISH, RNA pull-down, RNA immunoprecipitation assay, ChIP, immunohistochemistry, and immunofluorescence methods were used to quantified the expression of circNCAPG, U2AF65, RREB1 and TGF-β1, and the underlying mechanisms between them. MTS, EDU, neurosphere formation, limiting dilution neurosphere formation and transwell assays examined the proliferation and invasive capability of GSCs, respectively. We identified a novel circRNA named circNCAPG was overexpressed and indicated the poor prognosis in glioma patients. Upregulating circNCAPG promoted the malignant progression of GSCs. RNA binding protein U2AF65 could stabilize circNCAPG by direct binding. Mechanically, circNCAPG interacted with and stabilized RREB1, as well as stimulated RREB1 nuclear translocation to activate TGF-β1 signaling pathway. Furthermore, RREB1 transcriptionally upregulated U2AF65 expression to improve the stability of circNCAPG in GSCs, which established a feedback loop involving U2AF65, circNCAPG and RREB1. Since circRNA is more stable than mRNA and can execute its function continuously, targeting circNCAPG in glioma may be a novel promising therapeutic.

CircRNA MBOAT2 promotes intrahepatic cholangiocarcinoma progression and lipid metabolism reprogramming by stabilizing PTBP1 to facilitate FASN mRNA cytoplasmic export

The carcinogenic role of FASN by regulating lipid metabolism reprogramming has been well-established in multiple tumors. However, whether mechanisms during intrahepatic cholangiocarcinoma (ICC) progression, such as circRNAs, regulate FASN expression remains unknown. Here we demonstrate a lipid metabolism-related circRNA, circMBOAT2 (hsa_circ_0007334 in circBase), frequently upregulated in ICC tissues, and positively correlated with ICC malignant features. CircMBOAT2 knockdown inhibits the growth and metastasis of ICC cells. Mechanistically, circMBOAT2 combines with PTBP1 and protects PTBP1 from ubiquitin/proteasome-dependent degradation, impairing the function of PTBP1 to transfer FASN mRNA from the nucleus to the cytoplasm. Moreover, circMBOAT2 and FASN have the same effect on fatty acid profile, unsaturated fatty acids instead of saturated fatty acids are primarily regulated and associated with malignant behaviors of ICC cells. The levels of lipid peroxidation and ROS were significantly higher when FASN was knocked down and recovered when circMBOAT2 was overexpressed. Our results identified that circMBOAT2 was upregulated in ICC and promoted progression by stabilizing PTBP1 to facilitate FASN mRNA cytoplasmic export, which altered lipid metabolic profile and regulated redox homeostasis in ICC, suggesting that circMBOAT2 may serve as an available therapeutic target for ICC with active lipid metabolism.

Circular RNA circTRPS1-2 inhibits the proliferation and migration of esophageal squamous cell carcinoma by reducing the production of ribosomes

Circular RNAs play important roles in many cancers, including esophageal squamous cell carcinoma (ESCC), but the precise functions of most circular RNAs are poorly understood. Here we detected significant downregulation of circTRPS1-2 in ESCC based on high-throughput sequencing of three pairs of ESCC tissue and adjacent normal tissue, followed by PCR validation with another 30 tissue pairs. Patients with ESCC whose circTRPS1-2 expression was below the median level for the sample showed significantly shorter median overall survival (13 months) than patients whose circTRPS1-2 expression was above the median (36 months). Overexpressing circTRPS1-2 in the human ESCC cell lines K150 and E109, which express low endogenous levels of circTRPS1-2, inhibited cell proliferation and migration. Conversely, knocking down circTRPS1-2 using short interfering RNA promoted cell proliferation and migration. Similar results were observed in mice bearing K150 xenografts in which circTRPS1-2 was overexpressed or knocked down. Several ribosomal proteins co-immunoprecipitated with circTRPS1-2 from K150 cells in culture, and K150 cells overexpressing circTRPS1-2 showed reduced numbers of ribosomes by A260 absorbance measure and electron microscopy. Our results suggest that circTRPS1-2 can inhibit ESCC proliferation and migration by reducing the production of ribosomes, establishing its potential usefulness in ESCC treatment and prediction of prognosis.

Circular RNA, circular RARS, promotes aerobic glycolysis of non-small-cell lung cancer by binding with LDHA

PURPOSE

Accumulating evidence has highlighted the critical roles of circular RNAs (circRNAs) in non-small-cell lung cancer (NSCLC). This study aims to unveil the roles of circRARS (circular RARS) (hsa_circ_0001551) in NSCLC.

METHODS

Quantitative real-time PCR was used to determine the expression of circRARS in NSCLC tissues and cells. Kaplan-Meier analysis was used to determine the prognostic value of circRARS expression. CCK8, transwell, and wound healing assays were used to assess the proliferation, invasion, and migration abilities of NSCLC cells. RNA pull-down, cell fraction, glucose consumption, lactate production, and lactate dehydrogenase activity assays were conducted to explore the potential mechanisms of circRARS in NSCLC.

RESULTS

circRARS is upregulated in NSCLC tissues and positively correlated with smoking status, lymph node metastasis, and higher tumor stages. NSCLC patients with high expression of circRARS have poor overall survival. Functional assays demonstrated that circRARS accelerated the proliferation, invasion, and migration of NSCLC cells in vitro. The cell fraction suggested that circRARS mainly accumulated in cytoplasm and the RNA pull-down assay showed lactate dehydrogenase (LDHA) could bind with circRARS. Furthermore, circRARS positively regulates LDHA activity and LDHA expression at the transcription level. Moreover, downregulated circRARS decreases glucose consumption and lactate production and compromises aerobic glycolysis in NSCLC cells. Finally, rescue assays showed circRARS could promote NSCLC cell proliferation by regulating LDHA activity.

CONCLUSION

This study shows that circRARS can promote glycolysis and tumor progression in NSCLC by regulating LDHA.

Silencing of circCRIM1 Drives IGF2BP1-Mediated NSCLC Immune Evasion

OBJECTIVES

Circular RNAs (circRNAs) have been found to have significant impacts on non-small cell lung cancer (NSCLC) progression through various mechanisms. However, the mechanism of circRNAs modulating tumor immune evasion in NSCLC has yet to be well-revealed.

MATERIALS AND METHODS

Through analyzing the expression profiles of circRNAs in NSCLC tissues, RNA FISH, pull-down assay, mass spectrometry analysis, and RIP, circCRIM1 was identified, and its interaction with IGF2BP1 was confirmed. The effects of circCRIM1 on modulating tumor immune evasion were explored via co-culture in vitro and in tumor xenograft models. Subsequently, we evaluated the regulatory effects of circCRIM1 on IGF2BP1 and screened its target genes through RNA sequencing. Finally, we explored the underlying molecular mechanisms that circCRIM1 could regulate the stability of target mRNA.

RESULTS

circCRIM1 was downregulated in NSCLC, and its expression was positively correlated with favorable prognoses. Furthermore, circCRIM1 was more stable than its linear transcript and was mainly localized in the cytoplasm. Mechanistically, circCRIM1 destabilized HLA-F mRNA via competitive binding to IGF2BP1. Importantly, the overexpression of circCRIM1 suppressed the immune evasion of NSCLC and promoted the expressions of Granzyme B, IFN-γ, and TNF-α of CD8+ T and NK cell in vitro co-culture assays and tumor xenograft models.

CONCLUSIONS

This study identifies circCRIM1 as a new tumor suppressor that inhibits tumor immune evasion through a competitive combination with IGF2BP1 to destabilize HLA-F mRNA.

A pan-cancer landscape of IGF2BPs and their association with prognosis, stemness and tumor immune microenvironment

Background

The human insulin-like growth factor 2 mRNA binding proteins 1-3 (IGF2BP1-3, also called IMP1-3) play essential roles in mRNA regulation, including its splicing, translocation, stability, and translation. However, knowledge regarding the involvement of IGF2BPs in tumor immunity and stemness across cancer types is still lacking.

Methods

In this study, we comprehensively analyzed pan-cancer multi-omic data to determine the correlation of IGF2BPs mRNA and protein expression with various cancer parameters such as mutation frequency, prognostic value, the tumor microenvironment (TME), checkpoint blockade, tumor immune infiltration, stemness and drug sensitivity. Validation of the expression of IGF2BPs in cancer samples and glioma cells were performed by quantitative real-time (qRT)-PCR, and immunofluorescence staining. Investigation of the functional role of IGF2BP3 in glioma stem cells(GSCs) were performed by sphere formation, cytotoxicity, transwell, and wound healing assays.

Results

We found that IGF2BP1 and 3 are either absent or expressed at very low levels in most normal tissues. However, IGF2BP1-3 can be re-expressed in a broad range of cancer types and diverse cancer cell lines, where their expression often correlates with poor prognosis. Immunofluorescence staining and qRT-PCR analyses also showed that the expression of IGF2BP2 and IGF2BP3 were higher in cancer tissues than that in adjacent normal tissues. Moreover, IGF2BPs are associated with TME and stemness in human pan-cancer. Remarkably, IGF2BP3 participated in the maintenance and self-renewal of glioma stem cell (GSCs). Knockdown of IGF2BP3 attenuated GSC and glioma cell proliferation, invasion, and migration.

Conclusions

Our systematic pan-cancer study confirmed the identification of IGF2BPs as therapeutic targets and highlighted the need to study their association with stemness, and the TME, which contribute to the cancer drug-discovery research. Especially, preliminary studies demonstrate the IGF2BP3 as a potential negative regulator of glioma tumorigenesis by modulating stemness.

Research progress of extracellular vesicles as biomarkers in immunotherapy for non-small cell lung cancer

Lung cancer is one of the most severe forms of malignancy and a leading cause of cancer-related death worldwide, of which non-small cell lung cancer (NSCLC) is the most primary type observed in the clinic. NSCLC is mainly treated with surgery, radiotherapy, and chemotherapy. Additionally, targeted therapy and immunotherapy have also shown promising results. Several immunotherapies, including immune checkpoint inhibitors, have been developed for clinical use and have benefited patients with NSCLC. However, immunotherapy faces several challenges like poor response and unknown effective population. It is essential to identify novel predictive markers to further advance precision immunotherapy for NSCLC. Extracellular vesicles (EVs) present an important research direction. In this review, we focus on the role of EVs as a biomarker in NSCLC immunotherapy considering various perspectives, including the definition and properties of EVs, their role as biomarkers in current NSCLC immunotherapy, and different EV components as biomarkers in NSCLC immunotherapy research. We describe the cross-talk between the role of EVs as biomarkers and novel technical approaches or research concepts in NSCLC immunotherapy, such as neoadjuvants, multi-omics analysis, and the tumour microenvironment. This review will provide a reference for future research to improve the benefits of immunotherapy for patients with NSCLC.

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.

Novel hypoxia-induced HIF1α-circTDRD3-positive feedback loop promotes the growth and metastasis of colorectal cancer

Tumor hypoxia and circular RNAs (circRNAs) are considered to play key roles in tumor progression and malignancy, respectively. Nevertheless, the biological functions and underlying mechanisms of specific circRNAs exposed to hypoxic microenvironments in colorectal cancer (CRC) remain largely elusive. Herein, a novel circRNA, circTDRD3, which is upregulated under hypoxic conditions, was identified. The expression of circTDRD3 was highly expressed in CRC tissues and positively correlated with overall survival, tumor size, lymph node invasion and clinical stage. CircTDRD3 facilitated CRC cell proliferation, migration and metastasis in vitro and in vivo. Mechanistically, circTDRD3 promoted HIF1α expression by sponging miR-1231, which facilitated CRC progression. Meanwhile, HIF1α directly combined with TDRD3 promoter to increase the expression of TDRD3 pre-mRNA. Then HIF1a-induced PTBP1 accelerated the formation of circTDRD3. Our findings reveal that circTDRD3 facilitates the proliferation and metastasis of CRC through a positive feedback loop mediated by the HIF1α/PTBP1/circTDRD3/miR-1231/HIF1α axis. Therefore, circTDRD3 may serve as a prognostic biomarker and therapeutic target for patients with CRC.

CircCDR1as mediates PM2.5-induced lung cancer progression by binding to SRSF1

Research indicates that particulate matter with an aerodynamic equivalent diameter of less than or equal to 2.5 µm in ambient air may induce lung cancer progression. Circular RNAs are a special kind of endogenous noncoding RNA, and their functions are reflected in various diseases and physiological processes, but there are still few studies related to PM_2.5-induced lung cancer. Here, we identified that circCDR1as was upregulated in lung cancer cells stimulated with PM_2.5 and positively correlated with the malignant features of lung cancer. The lower expression of CircCDR1as reduced the adverse progression of lung cancer cells after PM_2.5 treatment; the lower expression of circCDR1as impaired the growth size and metastatic ability of lung cancer cells in mouse tumour models. Mechanistically, circCDR1as specifically bound to serine/arginine-rich splicing Factor 1 (SRSF1) and affected the splicing of vascular endothelial growth factor-A (VEGFA) by SRSF1. Furthermore, circCDR1as affected SRSF1 function by regulating PARK2-mediated SRSF1 ubiquitination, protein production and degradation. CircCDR1as also affected C-myc and cyclin D1 expression by regulating SRSF1 and affecting the wnt/β-catenin signalling pathway, ultimately promoting malignant behavior and inhibiting the apoptosis of lung cancer cells, thereby causing PM_2.5-induced lung cancer development.

Whole Blood-Derived circUSP10 Acts as a Diagnostic Biomarker in Patients With Early-Stage Non-Small-Cell Lung Cancer

Accumulating evidence has indicated that differentially expressed noncoding circular RNAs (circRNAs) play essential roles in the occurrence and development of various types of cancer. Here, we aimed to identify and explore the diagnostic value of hsa_circ_0003026 (named circUSP10) in patients with early non-small-cell lung cancer (NSCLC). The differentially expressed circRNAs were screened from the microarray-based assay of human NSCLC tissues and their corresponding noncancerous tissues, and the candidate circRNAs were further verified in patients with NSCLC using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Circulating circUSP10 was isolated from whole blood of healthy people and patients with NSCLC and was detected by RT-qPCR. In addition, the diagnostic value of circUSP10 in early NSCLC was evaluated by receiver operating characteristic (ROC) curve analysis. We found that circUSP10 was upregulated in tumor tissues from patients with early NSCLC and associated with tumor size and tumor-node-metastasis (TNM) stage. Importantly, circUSP10 was obviously upregulated in the whole blood of patients with NSCLC. Additionally, whole blood-derived circUSP10 showed good diagnostic performance for screening early NSCLC and was relatively stable in blood under adverse conditions. These findings demonstrate that circUSP10 may act as a novel biomarker for the diagnosis of early-stage NSCLC, suggesting the potential of circUSP10 in RNA-based therapy for cancer.

circHECTD1 Promotes the Proliferation and Migration of Human Brain Vascular Smooth Muscle Cells via Interacting with KHDRBS3 to Stabilize EZH2 mRNA Expression

Purpose

The objective of this paper is to explore the role of circHECTD1 in vascular smooth muscle cells (VSMCs) and atherosclerosis (AS).

Methods

VSMCs were treated with platelet-derived growth factor-BB (PDGF-BB) in vitro, and the level of circHECTD1 was determined using qRT-PCR. Cell proliferation, migration, and invasion were analyzed using CCK8 and transwell assays. Cell apoptosis and cell cycle were analyzed using flow cytometry. The binding interaction between circHECTD1 and KHDRBS3 or EZH2 was investigated using the RIP, RNA pull-down.

Results

CircHECTD1 was upregulated in PDGF-BB-induced VSMCs with a dose-dependent and time-dependent manner. Knockdown of circHECTD1 suppressed VSMCsproliferation and migration and enhanced cell apoptosis in VSMCs, while circHECTD1 overexpression yielded opposite effects. Mechanistically, circHECTD1 could interact with KHDRBS3, thus enhanced the stability of EZH2 mRNA and increased EZH2 protein level. In addition, silencing EZH2 in VSMCs reversed the proliferation-enhancing effect of circHECTD1 overexpression.

Conclusion

Our findings provided providing a potential prognostic and therapy biomarker for AS.

New insights into circRNA and its mechanisms in angiogenesis regulation in ischemic stroke: a biomarker and therapeutic target

Ischemic stroke accounts for about 71% of strokes worldwide. Due to limited recommended therapeutics for ischemic stroke, more attention is focused on angiogenesis in ischemic stroke. Not long after ischemic stroke, angiogenesis arises and is vital for the prognosis. Various pro-angiogenic, anti-angiogenic factors and their downstream pathways engage in angiogenesis regulation. CircRNAs are differentially expressed after ischemic stroke. Up to now, circRNAs have been found to exert many functions in regulating apoptosis, autophagy, proliferation, and differentiation of neurons and neural stem cells mainly as miRNAs sponges or proteins decoy. Thus, many circRNAs are considered promising biomarkers or therapeutic targets for ischemic stroke. Besides, circRNAs participate in the modulation of endothelial-mesenchymal transition and blood-brain barrier maintenance. Moreover, circRNAs play significant roles in endothelial dysfunction concerning inflammation responses, apoptosis, proliferation, and migration. They correlate with many angiogenesis-related signaling pathways and genes via the circRNA/miRNA/mRNA network. Novel insights into circRNAs significance in angiogenesis regulation in ischemic stroke could be provided for further researches on the clinical application of circRNAs in ischemic stroke.