Comprehensive landscape and future perspectives of circular RNAs in colorectal cancer

CircANXA4 (hsa_circ_0055087) regulates the miR-1256/PRM1 axis to promote tumor progression in colorectal cancer

Colorectal cancer (CRC) incidence ranks third among malignant cancers with a high propensity for distant metastasis. Despite continuous efforts to improve treatment, the prognosis especially in patients with advanced distant metastasis is low. The mechanism of development and progression of CRC is not fully understood. Non-coding RNAs (ncRNAs) have emerged as essential regulators in cancer progression. Here, we aim to dissect the role of one critical ncRNA, circANXA4, in CRC progression. CircANXA4 expression was analyzed by the GEO database. Differentially expressed circRNAs were identified by the Limma package R software. Expression of circANXA4 and miR-1256 was detected by qRT-PCR. The regulation of circANXA4 on cell proliferation and progression was confirmed with the cell viability assay using cell counting kit-8 (CCK-8) and transwell migration assay. RNA pull-down assay, RNA immunoprecipitation (RIP), and western blot were used to determine the interaction between circANXA4, miR-1256, and protamine1 (PRM1). CircANXA4 was upregulated in both CRC tissues and cell lines. Knockdown of circANXA4 effectively reduced cell proliferation, progression, and migration. Additionally, silencing circANXA4 remarkably increased miR-1256 expression, while reducing PRM1 expression, thereby demonstrating that circANXA4 downregulates miR-1256 expression through a complementary binding site. Rescue experiments revealed the interactions between circANXA4, miR-1256, and PRM1. Pearson correlation analysis revealed that circANXA4 expression positively correlated with PRM1 expression and miR-1256 expression inversely correlated with PRM1 expression. In sum, we demonstrated that circANXA4 promotes cancer cell proliferation and progression by sponging miR-1256 and upregulating PRM1 in CRC.

Unraveling the crosstalk: circRNAs and the wnt signaling pathway in cancers of the digestive system

Circular RNA (circRNA) is a unique type of noncoding RNA molecule characterized by its closed-loop structure. Functionally versatile, circRNAs play pivotal roles in gene expression regulation, protein activity modulation, and participation in cell signaling processes. In the context of cancers of the digestive system, the Wnt signaling pathway holds particular significance. Anomalous activation of the Wnt pathway serves as a primary catalyst for the development of colorectal cancer. Extensive research underscores the notable participation of circRNAs associated with the Wnt pathway in the progression of digestive system tumors. These circRNAs exhibit pronounced dysregulation across esophageal cancer, gastric cancer, liver cancer, colorectal cancer, pancreatic cancer, and cholangiocarcinoma. Furthermore, the altered expression of circRNAs linked to the Wnt pathway correlates with prognostic factors in digestive system tumors. Additionally, circRNAs related to the Wnt pathway showcase potential as diagnostic, therapeutic, and prognostic markers within the realm of digestive system tumors. This comprehensive review outlines the interplay between circRNAs and the Wnt signaling pathway in cancers of the digestive system. It seeks to provide a comprehensive perspective on their association while delving into ongoing research that explores the clinical applications of circRNAs associated with the Wnt pathway.

METTL3-induced circ_0008345 contributes to the progression of colorectal cancer via the microRNA-182-5p/CYP1A2 pathway

BACKGROUND

Circular RNA (circRNAs) have been found to play major roles in the progression of colorectal cancer (CRC). However, the functions of circ_0008345 (transcribed by PTK2) in regulating CRC development remain undefined. In this study, we aimed to explore the roles and underlying mechanisms of circ_0008345 in CRC.

METHODS

RNase R-treated total cellular RNA was used to verify the circular structure of circ_0008345, and a subcellular fractionation assay was performed to detect the subcellular localization of circ_0008345. RNA pull-down and dual-luciferase assays were used to verify the binding relation between microRNA (miR)-182-5p and circ_0008345 and/or CYP1A2. Colony formation assay, EdU, and Transwell assays were performed to detect the biological behavior of CRC cells in vitro, and CRC cells were injected into mice to observe the tumor formation. m6A immunoprecipitation was used to detect the m6A modification of circ_0008345 in CRC cells.

RESULTS

Circ_0008345, upregulated in CRC tissues and cells, was mainly present in the cytoplasm. Circ_0008345 bound to miR-182-5p, and miR-182-5p targeted CYP1A2, an oncogene in CRC. The colony formation, mobility, EdU-positive cell rate in vitro, and tumor growth in mice were inhibited after the knockdown of circ_0008345. However, the suppressing effects of sh-circ_0008345 on CRC and CYP1A2 expression were significantly reversed after further knockdown of miR-182-5p. METTL3 was the m6A modifier mediating circ_0008345 expression, and the suppression of METTL3 reduced the expression of circ_0008345.

CONCLUSIONS

METTL3-dependent m6A methylation upregulated circ_0008345, which blocked the inhibitory effect of miR-182-5p on CYP1A2, thereby exacerbating the malignant phenotype of CRC cells.

Exploring non-coding RNA mechanisms in hepatocellular carcinoma: implications for therapy and prognosis

Hepatocellular carcinoma (HCC) is a significant contributor to cancer-related deaths in the world. The development and progression of HCC are closely correlated with the abnormal regulation of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs). Important biological pathways in cancer biology, such as cell proliferation, death, and metastasis, are impacted by these ncRNAs, which modulate gene expression. The abnormal expression of non-coding RNAs in HCC raises the possibility that they could be applied as new biomarkers for diagnosis, prognosis, and treatment targets. Furthermore, by controlling the expression of cancer-related genes, miRNAs can function as either tumor suppressors or oncogenes. On the other hand, lncRNAs play a role in the advancement of cancer by interacting with other molecules within the cell, which, in turn, affects processes such as chromatin remodeling, transcription, and post-transcriptional processes. The importance of ncRNA-driven regulatory systems in HCC is being highlighted by current research, which sheds light on tumor behavior and therapy response. This research highlights the great potential of ncRNAs to improve patient outcomes in this difficult disease landscape by augmenting the present methods of HCC care through the use of precision medicine approaches.

Role of STAT3 in cancer cell epithelial‑mesenchymal transition (Review)

Since its discovery, the role of the transcription factor, signal transducer and activator of transcription 3 (STAT3), in both normal physiology and the pathology of numerous diseases, including cancer, has been extensively studied. STAT3 is aberrantly activated in different types of cancer, fulfilling a critical role in cancer progression. The biological process, epithelial‑mesenchymal transition (EMT), is indispensable for embryonic morphogenesis. During the development of cancer, EMT is hijacked to confer motility, tumor cell stemness, drug resistance and adaptation to changes in the microenvironment. The aim of the present review was to outline recent advances in knowledge of the role of STAT3 in EMT, which may contribute to the understanding of the function of STAT3 in EMT in various types of cancer. Delineating the underlying mechanisms associated with the STAT3‑EMT signaling axis may generate novel diagnostic and therapeutic options for cancer treatment.

CircROR1 upregulates CCNE1 expression to promote melanoma invasion and metastasis by recruiting KAT2A

Circular RNAs (circRNAs) play important roles in cancer occurrence and progression. To explore and elucidate the clinical significance of specific circular RNA in melanoma and its potential molecular mechanism. CircROR1 expression in melanoma cells and tissues was confirmed by qRT-PCR and ISH. qRT-PCR and Western blotting were performed to measure the levels of CCNE1, KAT2A, MMP9 and TIMP2. MTT, Transwell and wound healing assays were performed to evaluate cell proliferation, invasion and metastasis. A xenograft mouse model was established to further verify the CircROR1/CCNE1 axis in vivo. RNA pull-down and RIP assays were performed to detect the direct interaction KAT2A and CircROR1. A ChIP assay was used to investigate the enrichment of H3K9ac acetylation in the CCNE1 promoter. CircROR1 was significantly upregulated in metastatic melanoma cells and tissues, promoting proliferation, invasion and metastasis in vitro and tumour growth in vivo. CircROR1 overexpression increased CCNE1 and MMP9 protein expression and decreased TIMP2 protein expression. Functional rescue assays demonstrated that CircROR1 played a role in promoting malignant progression through CCNE1. CircROR1 specifically bound to the KAT2A protein without affecting its expression. CircROR1 overexpression increased the level of H3K9ac modification in the CCNE1 promoter region by recruiting KAT2A, thus upregulating CCNE1 expression. CircROR1 upregulates CCNE1 expression through KAT2A-mediated histone acetylation. Our research confirms the critical role of CircROR1 in melanoma invasion and metastasis, and CircROR1 could serve as a potential therapeutic target for melanoma treatment.

CircTBC1D22A inhibits the progression of colorectal cancer through autophagy regulated via miR-1825/ATG14 axis

Distant metastasis is the main cause of death in patients with colorectal cancer (CRC). A better understanding of the mechanisms of metastasis can greatly improve the outcome of patients with CRC. Accumulating evidence suggests that circRNA plays pivotal roles in cancer progression and metastasis, especially acting as a miRNA sponge to regulate the expression of the target gene. A public database bioinformatics analysis found that miR-1825 was highly expressed in CRC tissues. In this study, miR-1825 was highly expressed in CRC tissues, which was positively correlated with lymph node metastasis and distant metastasis. In vitro and in vivo experiments confirmed that miR-1825 was positively correlated with the proliferation and migration of CRC cells. This event can be inhibited by circTBC1D22A. CircTBC1D22A can directly interact with miR-1825 and subsequently act as a miRNA sponge to regulate the expression of the target gene ATG14, which collectively advances the autophagy-mediated progression and metastasis of CRC.

The potential role and mechanism of circRNAs in Ferroptosis: A comprehensive review

Cell death encompasses various mechanisms, including necrosis and apoptosis. Ferroptosis, a unique form of regulated cell death, emerged as a non-apoptotic process reliant on iron and reactive oxygen species (ROS). Distinguishing itself from other forms of cell death, ferroptosis exhibits distinct morphological, biochemical, and genetic features. Circular RNAs (circRNAs), a novel class of RNA molecules, play crucial regulatory roles in ferroptosis-mediated pathways and cellular processes. With their circular structure and stability, circRNAs function as microRNA sponges and participate in protein regulation, offering diverse mechanisms for cellular control. Accumulating evidence indicates that circRNAs are key players in diseases associated with ferroptosis, presenting opportunities for diagnostic and therapeutic applications. This study explores the regulatory roles of circRNAs in ferroptosis and their potential in diseases such as cancer, neurological disorders, and cardiovascular diseases. By investigating the relationship between circRNAs and ferroptosis, this research provides new insights into the diagnosis, treatment, and prognosis of ferroptosis-related diseases. Furthermore, the therapeutic implications of targeting circRNAs in cancer treatment and the modulation of ferroptosis pathways demonstrate the potential of circRNAs as diagnostic markers and therapeutic targets. Overall, understanding the involvement of circRNAs in regulating ferroptosis opens up new avenues for advancements in disease management.

circCD2AP promotes epithelial mesenchymal transition and stemness in bladder cancer by regulating FOXQ1/USP21 axis

Bladder cancer (BC) is a prevalent and deadly disease. circCD2AP was suggested to be highly expressed in BC. However, the exact mechanism needs further investigation. In this study, circCD2AP was observed to be upregulated in BC and linked to poor prognosis in individuals. Functionally, circCD2AP or USP21 knockdown inhibited BC cell EMT and stemness both in vitro and in vivo. Mechanistically, circCD2AP interacted with ELAVL1 to enhance the stability of USP21 mRNA, which, in turn, inhibited the ubiquitination degradation of FOXQ1. Through rescue assay, USP21 or FOXQ1 knockdown was found to abolish the promoting effects of circCD2AP or USP21 overexpression on BC cell EMT and stemness. Overall, this study has unveiled the role of circCD2AP/ELAVL1/USP21/FOXQ1 axis in BC EMT and stemness regulation, offering insights into the mechanisms underlying BC progression, with potential implications for therapeutic strategies.

The Emerging Role of Non-Coding RNAs (ncRNAs) in Plant Growth, Development, and Stress Response Signaling

Plant species utilize a variety of regulatory mechanisms to ensure sustainable productivity. Within this intricate framework, numerous non-coding RNAs (ncRNAs) play a crucial regulatory role in plant biology, surpassing the essential functions of RNA molecules as messengers, ribosomal, and transfer RNAs. ncRNAs represent an emerging class of regulators, operating directly in the form of small interfering RNAs (siRNAs), microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs). These ncRNAs exert control at various levels, including transcription, post-transcription, translation, and epigenetic. Furthermore, they interact with each other, contributing to a variety of biological processes and mechanisms associated with stress resilience. This review primarily concentrates on the recent advancements in plant ncRNAs, delineating their functions in growth and development across various organs such as root, leaf, seed/endosperm, and seed nutrient development. Additionally, this review broadens its scope by examining the role of ncRNAs in response to environmental stresses such as drought, salt, flood, heat, and cold in plants. This compilation offers updated information and insights to guide the characterization of the potential functions of ncRNAs in plant growth, development, and stress resilience in future research.

Exosomal circRNAs in gastrointestinal cancer: Role in occurrence, development, diagnosis and clinical application (Review)

Gastrointestinal cancer is frequently detected at an advanced stage and has an undesirable prognosis due to the absence of efficient and precise biomarkers and therapeutic targets. Exosomes are small, living‑cell‑derived vesicles that serve a critical role in facilitating intercellular communication by transporting molecules from donor cells to receiver cells. circular RNAs (circRNAs) are mis‑expressed in a variety of diseases, including gastrointestinal cancer, and are promising as diagnostic biomarkers and tumor therapeutic targets for gastrointestinal cancer. The main features of exosomes and circRNAs are discussed in the present review, along with research on the biological function of exosomal circRNAs in the development and progression of gastrointestinal cancer. It also assesses the advantages and disadvantages of implementing these findings in clinical applications.

Circular RNA RHBDD1 regulates tumorigenicity and ferroptosis in colorectal cancer by mediating the ELAVL1/SCD mRNA interaction

Circular RNAs (circRNAs) are covalently closed noncoding RNA molecules that play multiple roles in tumorigenesis and metastasis. Ferroptosis is an iron-dependent, regulated form of cell death and has emerged as a promising target for cancer treatment. However, whether and how circRNAs regulate ferroptotic cell death in colorectal cancer (CRC) remains largely unknown. Three circRNA microarrays were used to screen differentially expressed circRNAs in CRC tissues. A series of functional experiments were conducted to investigate the effects of circRNA on CRC cell proliferation, migration and ferroptosis. We found that hsa_circ_0058495 (circRHBDD1), a novel circRNA, was significantly upregulated in colorectal cancer tissues and cells. The expression levels of circRHBDD1 in serum samples were strongly associated with the advancement of CRC. Silencing of circRHBDD1 remarkably suppressed the proliferation and migration of CRC cells in vitro. Moreover, the depletion of circRHBDD1 notably increased ferroptotic cell death and enhanced RSL3-induced ferroptosis in CRC cells. Mechanistically, circRHBDD1 upregulated the expression of stearoyl-CoA desaturase (SCD), a ferroptosis suppressor mediating lipid remodelling, by enhancing the ELAVL1/SCD mRNA interaction. Finally, circRHBDD1 knockdown repressed the tumorigenesis and ferroptosis of CRC cells in vivo. In conclusion, circRHBDD1 facilitates tumour progression and obstructs ferroptosis in CRC by regulating SCD expression in an ELAVL1-dependent manner.

Omics-based molecular classifications empowering in precision oncology

BACKGROUND

In the past decades, cancer enigmatical heterogeneity at distinct expression levels could interpret disparities in therapeutic response and prognosis. It built hindrances to precision medicine, a tactic to tailor customized treatment informed by the tumors' molecular profile. Single-omics analysis dissected the biological features associated with carcinogenesis to some extent but still failed to revolutionize cancer treatment as expected. Integrated omics analysis incorporated tumor biological networks from diverse layers and deciphered a holistic overview of cancer behaviors, yielding precise molecular classification to facilitate the evolution and refinement of precision medicine.

CONCLUSION

This review outlined the biomarkers at multiple expression layers to tutor molecular classification and pinpoint tumor diagnosis, and explored the paradigm shift in precision therapy: from single- to multi-omics-based subtyping to optimize therapeutic regimens. Ultimately, we firmly believe that by parsing molecular characteristics, omics-based typing will be a powerful assistant for precision oncology.

Integrated whole transcriptome profiling revealed a convoluted circular RNA-based competing endogenous RNAs regulatory network in colorectal cancer

Recently, it has been identified that circRNAs can act as miRNA sponge to regulate gene expression in various types of cancers, associating them with cancer initiation and progression. The present study aims to identify colorectal cancer-related circRNAs and the underpinning mechanisms of circRNA/miRNA/mRNA networks in the development and progress of Colorectal Cancer. Differentially expressed circRNAs, miRNAs, and mRNAs were identified in GEO microarray datasets using the Limma package of R. The analysis of differentially expressed circRNAs resulted in 23 upregulated and 31 downregulated circRNAs. CeRNAs networks were constructed by intersecting the results of predicted and experimentally validated databases, circbank and miRWalk, and by performing DEMs and DEGs analysis using Cytoscape. Next, functional enrichment analysis was performed for DEGs included in ceRNA networks. Followed by survival analysis, expression profile assessment using TCGA and GEO data, and ROC curve analysis we identified a ceRNA sub-networks that revealed the potential regulatory effect of hsa_circ_0001955 and hsa_circ_0071681 on survival-related genes, namely KLF4, MYC, CCNA2, RACGAP1, and CD44. Overall, we constructed a convoluted regulatory network and outlined its likely mechanisms of action in CRC, which may contribute to the development of more effective approaches for early diagnosis, prognosis, and treatment of CRC.

Multilevel Heterogeneity of Colorectal Cancer Liver Metastasis

Colorectal cancer liver metastasis (CRLM) is a highly heterogeneous disease. Therapies that target both primary foci and liver metastasis are severely lacking. Therefore, understanding the features of metastatic tumor cells in the liver is valuable for the overall control of CRLM patients. In this review, we summarize the heterogeneity exhibited in CRLM from five aspects (gene, transcriptome, protein, metabolism, and immunity). In addition to genetic heterogeneity, the other four aspects exhibit significant heterogeneity. Compared to primary CRC, the dysregulation of epithelial-mesenchymal transition (EMT)-related proteins, the enhanced metabolic activity, and the increased infiltration of immunosuppressive cells are detected in CRLM. Preclinical evidence shows that targeting the EMT process or enhancing cellular metabolism may represent a novel approach to increasing the therapeutic efficacy of CRLM.

Hsa_circ_0009092/miR-665/NLK signaling axis suppresses colorectal cancer progression via recruiting TAMs in the tumor microenvironment

BACKGROUND

It has been demonstrated that circularRNA (circRNAs) plays a critical role in various cancers. While the potential molecular mechanism of circRNAs in the progression of colorectal cancer (CRC) remains uncertain.

METHODS

Differentially expressed circRNAs were identified by RNA sequencing. RT-qPCR detected the expression of circ_0009092, miR-665, and NLK in CRC tissues and cells. Functions of circ_0009092 on tumor cell proliferation, migration, and invasion were investigated by a series of in vitro assays. The underlying mechanism of circ_0009092 was explored by bioinformatics analysis, RNA immunoprecipitation (RIP) and luciferase assays. A co-culture assay in vitro was performed to detect the affection of circ_0009092 on macrophage recruitment in the tumor microenvironment (TME). A xenograft mouse model was used to explore the effect of circ_0009092 on tumor growth.

RESULTS

Circ_0009092 was downregulated in CRCand predicted a good prognosis. Overexpression of circ_0009092 reduced tumor cell EMT, proliferation, migration, and invasion in vitro and in vivo. Mechanistically, circ_0009092 elevated the NLK expression via sponging miR-665 and suppressed the Wnt/β-catenin signaling pathway. EIF4EA3 induced circ_0009092 expression in CRC cells. In addition, NLK regulates phosphorylation and O-GlcNAcylation of STAT3 by binding to STAT3, thereby inhibiting CCL2 expression, in which it inhibits macrophage recruitment in the tumor microenvironment (TME).

CONCLUSION

EIF4A3 suppressed circ_0009092 biogenesis, whichinhibits CRC progression by sponging miR-665 to downregulate NLK. Circ_0009092/miR-665/NLK suppressed tumor EMT, proliferation, migration, and invasion by acting on the Wnt/β-catenin signaling pathway. NLK directly interacted with STAT3 and decreased the CCL2 expression, inhibiting the recruitment of tumor-associated macrophages (TAMs) in the TME. Our study provided novel insights into the roles of circ_0009092 as a novel promising prognostic and therapeutic target in CRC.

Colorectal cancer cell exosome and cytoplasmic membrane for homotypic delivery of therapeutic molecules

Colorectal cancer (CRC) is one of the most common causes of death in the world. The multi-drug resistance, especially in metastatic colorectal cancer, drives the development of new strategies that secure a positive outcome and reduce undesirable side effects. Nanotechnology has made an impact in addressing some pharmacokinetic and safety issues related to administration of free therapeutic agents. However, demands of managing complex biointerfacing require equally complex methods for introducing stimuli-responsive or targeting elements. In order to procure a more efficient solution to the overcoming of biological barriers, the physiological functions of cancer cell plasma and exosomal membranes provided the source of highly functionalized coatings. Biomimetic nanovehicles based on colorectal cancer (CRC) membranes imparted enhanced biological compatibility, immune escape and protection to diverse classes of therapeutic molecules. When loaded with therapeutic load or used as a coating for other therapeutic nanovehicles, they provide highly efficient and selective cell targeting and uptake. This review presents a detailed overview of the recent application of homotypic biomimetic nanovehicles in the management of CRC. We also address some of the current possibilities and challenges associated with the CRC membrane biomimetics.

CircRNA circ_0013339 Regulates the Progression of Colorectal Cancer Through miR-136-5p/SOX9 Axis

BACKGROUND

Colorectal cancer (CRC) is a common gastrointestinal malignancy. Dysregulation of circular RNAs (circRNAs) is associated with the progression of CRC. However, the role of circ_0013339 (hsa_circ_0013339) in CRC is still not clear.

METHODS

The levels of circ_0013339, miR-136-5p, and SRY-box transcription factor 9 (SOX9) in CRC were gauged by quantitative real-time polymerase chain reaction (qRT-PCR). Colony formation and 5-Ethynyl-2'-deoxyuridine (EdU) assays were used to detect cell proliferation. Cell counting kit-8 (CCK8) assay was used to measure cell viability. Western blot assay was performed to examine protein expression. The relationship between miR-136-5p and circ_0013339 or SOX9 was tested by dual-luciferase reporter assay. The effect of sh-circ_0013339 on tumor growth in vivo was examined by xenograft experiments.

RESULTS

Circ_0013339 expression was elevated in CRC tissues and cells, and circ_0013339 knockdown diminished the growth of CRC cells. MiR-136-5p was regulated by circ_0013339. MiR-136-5p deficiency ameliorated the effects of circ_0013339 silencing on CRC cell malignant behaviors. Circ_0013339 modulated SOX9 expression through miR-136-5p. SOX9 addition reversed the effects of miR-136-5p overexpression on CRC cell behaviors. Moreover, silencing of circ_0013339 suppressed the growth of xenograft tumors in vivo.

CONCLUSION

Circ_0013339 regulates the progression of CRC through miR-136-5p-dependent regulation of SOX9, uncovering a novel regulatory mechanism of circ_0013339 in CRC.

A circRNA-based ceRNA network shows its diagnostic value in non-small-cell lung cancer

BACKGROUND

Numerous studies have reported the vital roles of circular RNA (circRNA)-based competitive endogenous RNA (ceRNA) regulatory networks in cancers. Here, we established a non-small-cell lung cancer (NSCLC)-related circRNA-miRNA-mRNA axis and estimated its diagnostic value in NSCLC.

METHODS

The circ_0061235-miR-3180-5p-PPM1L axis was constructed by small RNA deep sequencing, bioinformatics databases, and preliminary testing. The serum levels of the selected circ_0061235, miR-3180-5p, and PPM1L were quantified using quantitative polymerase chain reaction. Receiver operating characteristic analyses were conducted to evaluate the diagnostic power.

RESULTS

The levels of circ_0061235, miR-3180-5p, and PPM1L showed close correlations according to the ceRNA regulation rule. They were significantly dysregulated in NSCLC and showed the diagnostic ability to discriminate between healthy and NSCLC, and remarkably, between benign lung tumors and NSCLC. Additionally, the down-regulated levels of hsa_circ_0061235, the up-regulated levels of miR-3180-5p, and the decreased levels of PPM1L were correlated to more aggressive features of NSCLC, such as lymph node metastasis, distant metastasis, and higher stages. Intriguingly, compared to the single circ_0061235, miR-3180-5p, PPM1L, and traditional tumor markers, the diverse combinations of circ_0061235, miR-3180-5p, and PPM1L showed much higher sensitivity and specificity to differentiate greater or lesser severity of NSCLC. GO annotation and KEGG pathway analyses revealed the underlying role of the circ_0061235-miR-3180-5p-PPM1L axis in NSCLC.

CONCLUSIONS

We established a specific circRNA-miRNA-mRNA network with higher sensitivity and specificity to diagnose NSCLC, particularly more aggressive NSCLC, providing a new strategy for further developing tumor biomarkers.

Hsa_circRNA_001676 accelerates the proliferation, migration and stemness in colorectal cancer through regulating miR-556-3p/G3BP2 axis

Circular RNAs (circRNAs) play key roles in colorectal cancer (CRC) progression, but little is known about the biological functions of hsa_circRNA_001676 in CRC. Therefore, we explored the potential role of hsa_circRNA_001676 in CRC development. RT-qPCR was performed to determine hsa_circRNA_001676, miR-556-3p and Ras-GTPase-activating SH3 domain-binding-proteins 2 (G3BP2) levels in CRC tissues. Meanwhile, to evaluate the roles of hsa_circRNA_001676, miR-556-3p and G3BP2 on CRC, functional analysis of cell proliferation, migration and stemness were then performed. Our results showed that compared to normal tissues, hsa_circRNA_001676 and G3BP2 level was elevated, but miR-556-3p level was reduced in CRC tissues. Additionally, luciferase reporter results showed that hsa_circRNA_001676 was shown to target miR-556-3p, and G3BP2 was targeted by miR-556-3p. Hsa_circRNA_001676 or G3BP2 overexpression promoted CRC cell proliferation and migration. Conversely, miR-556-3p overexpression suppressed CRC cell proliferation and migration. Moreover, deficiency of hsa_circRNA_001676 or G3BP2 repressed the CRC cell proliferation, migration and stemness. Meanwhile, hsa_circRNA_001676 deficiency obviously reduced tumor growth and stemness in a CRC mouse xenograft model. Furthermore, hsa_circRNA_001676 deficiency notably reduced G3BP2 level, but elevated miR-556-3p level in tumor tissues from tumor-bearing mice. Mechanistically, hsa_circRNA_001676 targeted miR-556-3p to increase G3BP2 level, contributing to the progression of CRC. Collectively, hsa_circRNA_001676 was able to accelerate proliferation, migration and stemness in CRC through regulating miR-556-3p/G3BP2 axis, suggesting that hsa_circRNA_001676 may become a potential therapeutic target in treating CRC.

Extracellular vesicle biomarkers in circulation for the diagnosis of gastric cancer: A systematic review and meta‑analysis

The prognosis of a gastric cancer (GC) diagnosis is poor due to the current lack of effective early diagnostic methods. Extracellular vesicle (EV) biomarkers have previously demonstrated strong diagnostic efficiency for certain types of cancer, including pancreatic and lung cancer. The present review aimed to summarize the diagnostic value of circulating EV biomarkers for early stage GC. The PubMed, Medline and Web of Science databases were searched from May 1983 to September 18, 2022. All studies that reported the diagnostic performance of EV biomarkers for GC were included for analysis. Overall, 27 studies were selected containing 2,831 patients with GC and 2,117 controls. A total of 58 EV RNAs were reported in 26 studies, including 39 microRNAs (miRNAs), 10 long non-coding RNAs (lncRNAs), five circular RNAs, three PIWI-interacting RNAs and one mRNA, in addition to one protein in the remaining study. Meta-analysis of the aforementioned studies demonstrated that the pooled sensitivity, specificity and AUC value of the total RNAs were 84, 67% and 0.822, respectively. The diagnostic values of miRNAs were consistent with the total RNA, as the pooled sensitivity, specificity and AUC value were 84, 67% and 0.808, respectively. The pooled sensitivity, specificity and AUC values of lncRNAs were 89, 69% and 0.872, respectively, markedly higher compared with that of miRNAs. A total of five studies reported the diagnostic performance of EV RNA panels for early stage GC and reported powerful diagnostic values with a pooled sensitivity, specificity and AUC value of 80, 77% and 0.879, respectively. Circulating EV RNAs could have the potential to be used in the future as effective, noninvasive biomarkers for early GC diagnosis. Further research in this field is necessary to translate these findings into clinical practice.

Role of Epithelial to Mesenchymal Transition in Colorectal Cancer

The epithelial-mesenchymal transition (EMT) is a cellular reprogramming process that occurs during embryonic development and adult tissue homeostasis. This process involves epithelial cells acquiring a mesenchymal phenotype. Through EMT, cancer cells acquire properties associated with a more aggressive phenotype. EMT and its opposite, mesenchymal-epithelial transition (MET), have been described in more tumors over the past ten years, including colorectal cancer (CRC). When EMT is activated, the expression of the epithelial marker E-cadherin is decreased and the expression of the mesenchymal marker vimentin is raised. As a result, cells temporarily take on a mesenchymal phenotype, becoming motile and promoting the spread of tumor cells. Epithelial-mesenchymal plasticity (EMP) has become a hot issue in CRC because strong inducers of EMT (such as transforming growth factor β, TGF-β) can initiate EMT and regulate metastasis, microenvironment, and immune system resistance in CRC. In this review, we take into account the significance of EMT-MET in CRC and the impact of the epithelial cells' plasticity on the prognosis of CRC. The analysis of connection between EMT and colorectal cancer stem cells (CCSCs) will help to further clarify the current meager understandings of EMT. Recent advances affecting important EMT transcription factors and EMT and CCSCs are highlighted. We come to the conclusion that the regulatory network for EMT in CRC is complicated, with a great deal of crosstalk and alternate paths. More thorough research is required to more effectively connect the clinical management of CRC with biomarkers and targeted treatments associated with EMT.

The Glioblastoma CircularRNAome

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

Therapeutic potential of gene therapy for gastrointestinal diseases: Advancements and future perspectives

Advancements in understanding the pathogenesis mechanisms underlying gastrointestinal diseases, encompassing inflammatory bowel disease, gastrointestinal cancer, and gastroesophageal reflux disease, have led to the identification of numerous novel therapeutic targets. These discoveries have opened up exciting possibilities for developing gene therapy strategies to treat gastrointestinal diseases. These strategies include gene replacement, gene enhancement, gene overexpression, gene function blocking, and transgenic somatic cell transplantation. In this review, we introduce the important gene therapy targets and targeted delivery systems within the field of gastroenterology. Furthermore, we provide a comprehensive overview of recent progress in gene therapy related to gastrointestinal disorders and shed light on the application of innovative gene-editing technologies in treating these conditions. These developments are fueling a revolution in the management of gastrointestinal diseases. Ultimately, we discuss the current challenges (particularly regarding safety, oral efficacy, and cost) and explore potential future directions for implementing gene therapy in the clinical settings for gastrointestinal diseases.

Advancements in Understanding the Role of Circular RNA in Osteosarcoma

Osteosarcoma, the most prevalent primary malignant bone tumor and the third most frequent cancer in children and adolescents worldwide, still poses a significant therapeutic challenge. Even though combined chemotherapy and surgical resection have improved survival rates up to 60%, the prognosis for most patients with metastatic osteosarcoma continues to be dismal. The specific pathogenesis and key regulators of tumor invasion and metastasis remain largely elusive. Circular RNAs (circRNAs), novel endogenous non-coding RNA molecules that form covalently closed continuous loops through splicing, play a crucial role in the development, progression, clinical diagnosis, and treatment of various diseases. Recently, an escalating number of circular structures have been identified in osteosarcoma. Understanding their role in osteosarcoma is advantageous for early detection, diagnosis, and treatment of this disease. The primary function of circRNA involves its unique ability to bind specifically to miRNA, although their biological functions also extend to interacting with proteins, regulating gene transcription, and serving as translation templates. In this review, we explore the mechanisms and clinical applications of circRNAs in the pathogenesis and progression of osteosarcoma, with a particular emphasis on the regulatory mechanisms and functions of circRNAs as miRNA sponges in osteosarcoma development.

Circ-MALAT1 accelerates cell proliferation and epithelial mesenchymal transformation of colorectal cancer through regulating miR-506-3p/KAT6B axis

Colorectal cancer (CRC) is a prevalent malignant tumor of the digestive tract. Circular RNAs may play important roles in the progression of CRC. In this study, we investigated the roles and mechanisms of action of circ-MALAT1 in CRC. Gene expression and protein abundance were determined using qRT-PCR and western blot, respectively. Cell proliferation and migration were assessed by MTT, clone formation, and wound-healing assays. The interactions among the long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (circ-MALAT1), miR-506-3p, and lysine acetyltransferase 6B (KAT6B) were predicted using the StarBase software and confirmed by the luciferase activity assay. Circ-MALAT1 and KAT6B were upregulated, while miR-506-3p was downregulated in CRC cells. We validated that knocking down of circ-MALAT1 suppressed proliferation, migration, and epithelial-mesenchymal transition (EMT) of CRC cells, and these effects were abolished by miR-506-3p downregulation or KAT6B sufficiency. Our study suggests that circ-MALAT1 could sponge miR-506-3p to regulate the expression of KAT6B. Moreover, KAT6B sufficiency could neutralize miR-506-3p-dependent growth arrest, migration, and EMT. Circ-MALAT1 promotes cell proliferation, migration, and EMT of CRC cells via the miR-506-3p/KAT6B axis, thereby acting as a novel potential therapeutic target for the treatment of colorectal cancer.

Circ_0087862 promotes tumorigenesis and glycolysis in colorectal cancer by sponging miR-296-3p to regulate PGK1 expression

BACKGROUND

Circular RNAs (circRNAs) exert crucial roles in tumor progression of multiple cancers, including colorectal cancer (CRC). However, the functions of most circRNAs are not been fully elucidated. In this study, the role and mechanism of circ_0087862 in CRC were investigated.

METHODS

The expression of circ_0087862, microRNA-296-3p (miR-296-3p) and phosphoglycerate kinase 1 (PGK1) was detected by quantitative real-time PCR (qRT-PCR). Cell Counting Kit-8 (CCK-8) assay and 5-ethynyl-2'-deoxyuridine (EdU) assay were used to assess cell proliferation. Flow cytometry was employed to analyze cell apoptosis. Transwell assay was employed to evaluate cell invasion. Western blot assay was employed to detect the level of related protein markers and PGK1. The glucose consumption, lactate production were tested by corresponding kits. The relationship between miR-296-3p and circ_0087862 or PGK1 was verified by dual-luciferase reporter assay or RNA immunoprecipitation (RIP) assay. The in vivo function of circ_0087862 was examined by xenograft mice model.

RESULTS

The expression levels of circ_0087862 and PGK1 were up-regulated in CRC tissues and cells, while miR-296-3p was down-regulated. Circ_0087862 silencing suppressed cell proliferation, invasion and glycolysis and promoted cell apoptosis in CRC cells. Circ_0087862 targeted miR-296-3p in CRC cells. MiR-296-3p inhibition reversed circ_0087862 silencing-mediated inhibition effect on cell proliferation, invasion and glycolysis, as well as the promotion effect on cell apoptosis. PGK1 was a target of miR-296-3p, and the overexpression of PGK1 attenuated miR-296-3p-mediated tumor suppression effect on CRC progression. Moreover, knockdown of circ_0087862 inhibited tumorigenesis in vivo.

CONCLUSION

Circ_0087862 promoted CRC progression via miR-296-3p/PGK1 axis and might act as a potential target for CRC therapy.

Intergenic CircRNA Circ_0007379 Inhibits Colorectal Cancer Progression by Modulating miR-320a Biogenesis in a KSRP-Dependent Manner

Circular RNAs (circRNAs) are covalently closed RNA structures that play multiple roles in tumorigenesis and progression. Compared with exon‒intron circRNAs, the biological functions and implications of intergenic circRNAs in human cancer are still poorly understood. Here, we performed circRNA microarray analysis and identified an intergenic circRNA, circ_0007379, that was significantly downregulated in patients with colorectal cancer (CRC). The biogenesis of circ_0007379 was mediated by reverse complementary matches (RCMs) and was negatively regulated by the RNA helicase DHX9. Functionally, circ_0007379 suppressed CRC cell growth and metastasis in cell culture as well as in patient-derived organoid and xenograft models. Mechanistically, circ_0007379 acted as a scaffold to facilitate the processing of both pri-miR-320a and pre-miR-320a in a KSRP-dependent manner, leading to miR-320a maturation and subsequent repression of transcription factor RUNX1 expression. Thus, our findings establish a previously unrecognized function of circRNA in inhibiting CRC progression.

Progress of regulatory RNA in small extracellular vesicles in colorectal cancer

Colorectal cancer (CRC) is the second most common malignant tumor of the gastrointestinal tract with the second highest mortality rate and the third highest incidence rate. Early diagnosis and treatment are important measures to reduce CRC mortality. Small extracellular vesicles (sEVs) have emerged as key mediators that facilitate communication between tumor cells and various other cells, playing a significant role in the growth, invasion, and metastasis of cancer cells. Regulatory RNAs have been identified as potential biomarkers for early diagnosis and prognosis of CRC, serving as crucial factors in promoting CRC cell proliferation, invasion and metastasis, angiogenesis, drug resistance, and immune cell differentiation. This review provides a comprehensive summary of the vital role of sEVs as biomarkers in CRC diagnosis and their potential application in CRC treatment, highlighting their importance as a promising avenue for further research and clinical translation.

Circular RNAs in hepatocellular carcinoma: biogenesis, function, and pathology

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Both genetic and environmental factors through a multitude of underlying molecular mechanisms participate in the pathogenesis of HCC. Recently, numerous studies have shown that circular RNAs (circRNAs), an emerging class of non-coding RNAs characterized by the presence of covalent bonds linking 3' and 5' ends, play an important role in the initiation and progression of cancers, including HCC. In this review, we outline the current status of the field of circRNAs, with an emphasis on the functions and mechanisms of circRNAs in HCC and its microenvironment. We also summarize and discuss recent advances of circRNAs as biomarkers and therapeutic targets. These efforts are anticipated to throw new insights into future perspectives about circRNAs in basic, translational and clinical research, eventually advancing the diagnosis, prevention and treatment of HCC.

CircRNAs in colorectal cancer: potential biomarkers and therapeutic targets

Globally, colorectal cancer (CRC) is the third most prevalent cancer and the second leading cause of cancer-related deaths. Circular RNAs (circRNAs) are single-stranded RNA with covalently closed-loop structures and are highly stable, conserved, and abundantly expressed in various organs and tissues. Recent research found abnormal circRNA expression in CRC patients' blood/serum, cells, CRC tissues, and exosomes. Furthermore, mounting data demonstrated that circRNAs are crucial to the development of CRC. CircRNAs have been shown to exert biological functions by acting as microRNA sponges, RNA-binding protein sponges, regulators of gene splicing and transcription, and protein/peptide translators. These characteristics make circRNAs potential markers for CRC diagnosis and prognosis, potential therapeutic targets, and circRNA-based therapies. However, further studies are still necessary to improve the understanding of the roles and biological mechanisms of circRNAs in the development of CRC. In this review, up-to-date research on the role of circRNAs in CRC was examined, focusing on their potential application in CRC diagnosis and targeted therapy, which would advance the knowledge of the functions of circRNAs in the development and progression of CRC.

Diagnostic and prognostic role of circRNAs in pancreatic cancer: a meta-analysis

Background

Circular RNAs (circRNAs) are types of endogenous noncoding RNAs produced by selective splicing that are expressed highly specifically in various organisms and tissues and have numerous clinical implications in the regulation of cancer development and progression. Since circRNA is resistant to digestion by ribonucleases and has a long half-life, there is increasing evidence that circRNA can be used as an ideal candidate biomarker for the early diagnosis and prognosis of tumors. In this study, we aimed to reveal the diagnostic and prognostic value of circRNA in human pancreatic cancer (PC).

Methods

A systematic search for publications from inception to 22 July 2022 was conducted on Embase, PubMed, Web of Science (WOS), and the Cochrane Library databases. Available studies that correlated circRNA expression in tissue or serum with the clinicopathological, diagnostic, and prognostic values of PC patients were enrolled. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to evaluate clinical pathological characteristics. Area under the curve (AUC), sensitivity, and specificity were adopted to assess diagnostic value. Hazard ratios (HRs) were utilized to assess disease-free survival (DFS) and overall survival (OS).

Results

This meta-analysis enrolled 32 eligible studies, including six on diagnosis and 21 on prognosis, which accounted for 2,396 cases from 245 references. For clinical parameters, high expression of carcinogenic circRNA was significantly associated with degree of differentiation (OR = 1.85, 95% CI = 1.47-2.34), TNM stage (OR = 0.46, 95% CI = 0.35-0.62), lymph node metastasis (OR = 0.39, 95% CI = 0.32-0.48), and distant metastasis (OR = 0.26, 95% CI = 0.13-0.51). As for clinical diagnostic utility, circRNA could discriminate patients with pancreatic cancer from controls, with an AUC of 0.86 (95% CI: 0.82-0.88), a relatively high sensitivity of 84%, and a specificity of 80% in tissue. In terms of prognostic significance, carcinogenic circRNA was correlated with poor OS (HR = 2.00, 95% CI: 1.76-2.26) and DFS (HR = 1.96, 95% CI: 1.47-2.62).

Conclusion

In summary, this study demonstrated that circRNA may act as a significant diagnostic and prognostic biomarker for pancreatic cancer.

Hsa_circ_0057104, by competitive adsorption of miR-627-5p, mediates CCND2 expression to promote malignant proliferation and Warburg effect of colorectal cancer

OBJECTIVE

hsa_circ_0057104 (circPDK1) has been elucidated to regulate malignant behavior in pancreatic and renal cell carcinoma. The study functionally aimed at how circPDK1 modifies colorectal cancer (CRC) progression, along with its potential molecular mechanism.

METHODS

circPDK1 expression patterns in CRC tissues and cell lines were analyzed by RT-qPCR. circPDK1/miR-627-5p/CCND2 expression levels were changed by transient transfection. CCK-8 assay, flow cytometry, Transwell, immunoblotting, and commercial kits were utilized to measure CRC cell proliferation, apoptosis, invasion/migration, and glycolysis processes. Dual luciferase reporting assay and RIP assay were employed to evaluate the targeting relationship between circPDK1/miR-627-5p/CCND2.

RESULTS

circPDK1 was highly expressed in CRC. circPDK1 knockdown inhibited CRC cell proliferation, invasion/migration, and warburg effect and forced apoptosis. Overexpressing circPDK1 had the opposite effect. The effects of circPDK1 knockdown or circPDK1 overexpression on CRC cells were mitigated by downregulating miR-627-5p or CCND2, respectively. CircPDK1, by competitive adsorption of miR-627-5p, mediated CCND2 expression.

CONCLUSION

CircPDK1 induces the malignant behavior of CRC by competitive adsorption of miR-627-5p mediating CCND2 expression, offering new insights into the future development of CRC-targeted drugs.

Circ_0060967 contributes to colorectal cancer progression by sponging miR-1184 to up-regulate SRC proto-oncogene

BACKGROUND AND STUDY AIMS

Circular RNAs (circRNAs) are closely associated with cancer pathogenesis. The purpose of our current study was to explore the role and mechanism of circ_0060967 in colorectal cancer (CRC) development.

PATIENTS AND METHODS

Human CRC specimens and paired healthy tissues were used to examine variable expression. The expression of circ_0060967 and microRNA (miR)-1184 was examined by quantitative reverse transcription-PCR. The protein levels of proliferating cell nuclear antigen, BCL2-associated X, apoptosis regulator (Bax), proto-oncogene nonreceptor tyrosine kinase Src (SRC), nuclear factor-κB inhibitor alpha (IκBα), phosphorylated-IκBα (p-IκBα), RELA proto-oncogene, nuclear factor-κB subunit (p65), and phosphorylated-p65 (p-p65) were determined by western blot. Proliferation and motility of HCT-116 and SW480 CRC cells were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and transwell assays, respectively. Dual-luciferase reporter assay and RNA immunoprecipitation assay were used to determine the binding relation between miR-1184 and circ_0060967 or SRC. Animal studies were used to detect the role of circ_0060967 in CRC cell tumorigenicity.

RESULTS

Circ_0060967 abundance was enhanced in human CRC tissue samples versus paired normal colorectal tissues and in HCT-116 and SW480 CRC cells versus normal HCO cells. Decreased expression of circ_0060967 could suppress cell growth, motility, and invasiveness of CRC cells in vitro and tumor growth in vivo. Circ_0060967 sponged miR-1184, and miR-1184 targeted SRC. Furthermore, we also found circ_0060967 affected cell growth by modulating miR-1184/SRC axis in CRC.

CONCLUSION

This study demonstrates a novel circ_0060967/miR-1184/SRC regulatory cascade in affecting CRC cell malignant behaviors, which can have a broad effect on the field of molecularly targeted therapeutics.

The Crosstalk and Clinical Implications of CircRNAs and Glucose Metabolism in Gastrointestinal Cancers

The majority of glucose in tumor cells is converted to lactate despite the presence of sufficient oxygen and functional mitochondria, a phenomenon known as the "Warburg effect" or "aerobic glycolysis". Aerobic glycolysis supplies large amounts of ATP, raw material for macromolecule synthesis, and also lactate, thereby contributing to cancer progression and immunosuppression. Increased aerobic glycolysis has been identified as a key hallmark of cancer. Circular RNAs (circRNAs) are a type of endogenous single-stranded RNAs characterized by covalently circular structures. Accumulating evidence suggests that circRNAs influence the glycolytic phenotype of various cancers. In gastrointestinal (GI) cancers, circRNAs are related to glucose metabolism by regulating specific glycolysis-associated enzymes and transporters as well as some pivotal signaling pathways. Here, we provide a comprehensive review of glucose-metabolism-associated circRNAs in GI cancers. Furthermore, we also discuss the potential clinical prospects of glycolysis-associated circRNAs as diagnostic and prognostic biomarkers and therapeutic targets in GI cancers.

CircRNAs: emerging factors for regulating glucose metabolism in colorectal cancer

Colorectal cancer is a malignant disease with a high incidence and low survival rate, and the effectiveness of traditional treatments, such as surgery and radiotherapy, is very limited. CircRNAs, a kind of stable endogenous circular RNA, generally function by sponging miRNAs and binding or translating proteins. CircRNAs have been identified to play an important role in regulating the proliferation and metabolism of CRC. In recent years, many reports have indicated that by regulating the expression of glycolysis-related proteins, such as GLUT1 and HK2, or directly translating proteins, circRNAs can promote the Warburg effect in cancer cells, thereby driving CRC metabolism. Moreover, the Warburg effect increases lactate production in cancer cells and promotes acidification of the TME, which further drives cancer progression. In this review, we summarized the remarkable role of circRNAs in regulating glucose metabolism in CRC in recent years, which might be useful for finding new targets for the clinical treatment of CRC.

CircSTK3 drives the metastasis of colorectal cancer by regulating epithelial-mesenchymal transition

Circular RNAs (circRNAs) play crucial roles in malignancies. We aimed to delineate the functions and clinical importance of dysregulated circRNAs in colorectal cancer (CRC). We determined the circRNA expression profile from five CRC and paired adjacent normal tissues using circRNA microarray. We found that a novel circRNA, hsa_circ_0004592 (named circSTK3), was significantly upregulated in CRC tissues and correlated with decreased survival. Loss- and gain-of-function assays revealed that circSTK3 promoted the migration and invasion but not proliferation of cells. Whole genome expression microarray identified potential downstream targets and the regulatory networks of circSTK3; Gene Ontology analysis confirmed circSTK3 involvement in the CRC metastasis phenotype. Abnormal circSTK3 expression affected a subset of genes associated with CRC metastasis and triggered epithelial-mesenchymal transition programming, maintaining a tumor-promoting signature. Moreover, circSTK3 was transcriptionally regulated by CTCF. These findings reveal the functional and prognostic roles of circSTK3 and expose circRNAs as key players in metastasis.

Circular RNA ACACA negatively regulated p53-modulated mevalonate pathway to promote colorectal tumorigenesis via regulating miR-193a/b-3p/HDAC3 axis

This study aimed to explore the biological functions and underlying mechanism of circRNA acetyl-CoA carboxylase alpha (circACACA) in colorectal cancer (CRC). The RNA and protein levels were detected by qRT-PCR and western blot assays. The malignant capacities of CRC cells were analyzed by cell counting kit-8 (CCK-8), colony formation, flow cytometry, and transwell assays. The target relationship between miR-193a/b-3p and circACACA/histone deacetylase 3 (HDAC3) was determined by luciferase reporter assay and RNA immunoprecipitation. The binding of HDAC3 to the p53 promoter was validated by chromatin immunoprecipitation (ChIP). CRC cell growth and lung metastasis were evaluated in nude mice in vivo. High expression of circACACA was found in CRC tissues and cells, which was closely associated with the advanced tumor, lymph node, metastasis (TNM) stage, metastasis, and low overall survival rate. circACACA downregulation effectively delayed CRC cell proliferation and metastasis, but triggered apoptosis via inactivating the mevalonic acid (MVA) pathway. However, circACACA overexpression resulted in the opposite effects. Mechanistically, circACACA enhanced HDAC3 expression through sponging miR-193a/b-3p, which activated the MVA pathway via inhibiting the acetylation and transcription of p53. Moreover, rescue experiments confirmed that miR-193a/b-3p inhibition reversed the inhibitory effect of circACACA deficiency on CRC growth and metastasis. Moreover, circACACA overexpression-mediated malignant phenotypes of CRC cells were abrogated by HDAC3 knockdown. circACACA promoted CRC progression via regulating the miR-193a/b-3p/HDAC3/p53 axis to activate the MVA pathway, providing evidence for circACACA as a promising therapeutic target for CRC.

Exosomal circTUBGCP4 promotes vascular endothelial cell tipping and colorectal cancer metastasis by activating Akt signaling pathway

BACKGROUND

Exosome is crucial mediator and play an important role in tumor angiogenesis. Tip cell formation is a prerequisite for persistent tumor angiogenesis which causes tumor metastasis. However, the functions and underlying mechanisms of tumor cell-derived exosomes in angiogenesis and tip cell formation remain less understood.

METHODS

Exosomes derived from serum of colorectal cancer (CRC) patients with metastasis/non-metastasis and CRC cells were isolated by ultracentrifugation. CircRNAs in these exosomes were analyzed by circRNA microarray. Then, exosomal circTUBGCP4 was identified and verified by quantitative real-time PCR (qRT-PCR) and in situ hybridization (ISH). Loss- and gain-of-function assays were performed to explore the effect of exosomal circTUBGCP4 on vascular endothelial cell tipping and colorectal cancer metastasis in vitro and in vivo. Mechanically, bioinformatics analysis, biotin-labeled circTUBGCP4/ miR-146b-3p RNA pulldown, RNA immunoprecipitation (RIP), and luciferase reporter assay were used to confirm the interaction among circTUBGCP4, miR-146b-3p, and PDK2.

RESULTS

Here, we showed that exosomes derived from CRC cells enhanced vascular endothelial cell migration and tube formation via inducing filopodia formation and endothelial cell tipping. We further screened the upregulated circTUBGCP4 in serum of CRC patients with metastasis compared to non-metastasis. Silencing circTUBGCP4 expression in CRC cell-derived exosomes (CRC-CDEs) inhibited endothelial cell migration, tube formation, tip cell formation, and CRC metastasis. Overexpression of circTUBGCP4 had opposite results in vitro and in vivo. Mechanically, circTUBGCP4 upregulated PDK2 to activate Akt signaling pathway by sponging miR-146b-3p. Moreover, we found that miR-146b-3p could be a key regulator for vascular endothelial cell dysfunction. Exosomal circTUBGCP4 promoted tip cell formation and activated the Akt signaling pathway by inhibiting miR-146b-3p.

CONCLUSIONS

Our results suggest that colorectal cancer cells generate exosomal circTUBGCP4, which causes vascular endothelial cell tipping to promote angiogenesis and tumor metastasis by activating Akt signaling pathway.

CircZBTB46 Protects Acute Myeloid Leukemia Cells from Ferroptotic Cell Death by Upregulating SCD

Circular RNAs (circRNAs) have been shown to be closely linked to the tumorigenesis and treatment response of hematological malignancies. However, the biological functions and clinical implications of circRNAs in acute myeloid leukemia (AML) remain largely unknown. CircRNA microarray datasets were analyzed to screen differentially expressed circRNAs in AML patients. It was found that circZBTB46 was significantly upregulated in AML patients and AML cells. Moreover, the expression of circZBTB46 was associated with the stages of AML patients and showed high sensitivity and specificity for diagnosing AML. Silencing of circZBTB46 inhibited AML cell proliferation and induced cell cycle arrest. Importantly, the depletion of circZBTB46 notably increased ferroptosis and enhanced RSL3-induced ferroptosis in AML cells. Mechanistically, circZBTB46 upregulated the expression of stearoyl-CoA desaturase 1 (SCD) possibly by acting as a miRNA sponge. Finally, the circZBTB46 knockdown repressed the tumor growth of AML in vivo. In conclusion, circZBTB46 protects AML cells from ferroptosis and promotes the proliferation by upregulating SCD, thus suggesting that circZBTB46 may be a potential therapeutic target for AML.

Unveiling the prominent roles of circular RNAs ubiquitin binding associated protein 2 in cancers

Circular RNAs (circRNAs), a novel type of covalently closed non-coding RNAs, are widely expressed in eukaryotes and viruses. Accumulating evidence has shown that circRNAs play key roles in the pathophysiological changes process of human diseases and can affect cancer development and progression through regulating target genes expression, linear RNA transcription and protein generation. Recent studies had found that circRNA-UBAP2 (ubiquitin binding associated protein 2) was aberrantly expressed in various human tumors and could affect tumor cells proliferation, migration, invasion, cell cycle, anti-apoptosis, radioresistance, chemoresistance and other malignant biological behavioral progress. Mechanistic studies further revealed that circUBAP2 could affect the occurrence and development of human tumors through multiple different molecular regulatory pathways in vivo and in vitro. In addition, the abnormal expression of circUBAP2 was significantly correlated with the clinicopathological characteristics of malignant tumors and had potential value as biomarkers for the diagnosis and prognosis evaluation of cancer patients, which deserved further study. This review had summarized and discussed the oncogenic roles and clinical performances of circUBAP2 in various human malignancies with a focus on biological functions and molecular mechanisms, which could help to elevate the understanding to the roles of circRNAs and continue subsequent studies on circUBAP2.

The hsa_circ_0039857/miR-338-3p/RAB32 axis promotes the malignant progression of colorectal cancer

BACKGROUND

Colorectal cancer (CRC) is a prevalent malignancy of the gastrointestinal. Circular RNAs (circRNAs) act as important roles in CRC malignant progression. However, the role of circ_0039857 in CRC is still unclear. Therefore, this study aimed to explore the function and mechanism of hsa_circ_0039857 in the CRC.

METHODS

The mRNA and protein expression were measured via RT-qPCR. RNase R assay and Actinomycin D were employed to evaluate the stability of circ_0039857. Functional experiments, such as proliferation and apoptosis, were applied to study the function of circ_0039857 in CRC cells. The underlying mechanisms of circ_0039857 were then analyzed by bioinformatics, dual-luciferase reporter gene assay, RNA pull-down and rescue experiments.

RESULTS

We revealed that circ_0039857 was significantly enhanced in CRC. Circ_0039857 was stabler than linear RNA in cells and valuable for the disease diagnosis. In addition, circ_0039857 knockdown inhibited proliferation and promoted apoptosis. Mechanistically, circ_0039857 positively regulated the expression of RAB32 via sponging miR-338-3p.

CONCLUSION

This study demonstrated that circ_0039857 knockdown suppressed CRC malignant progression through miR-338-3p/RAB32 axis. Most importantly, this will help us to better understand the circRNA network in CRC, and may find potential biomarkers and targets for CRC clinical treatment.

The roles and mechanisms of circular RNAs related to mTOR in cancers

BACKGROUND

Circular RNAs (circRNAs) are stable molecules with covalently closed structures that have an irreplaceable role in the occurrence, progression, and even treatment of plenty of cancers. Mammalian/mechanistic target of rapamycin (mTOR) is a key regulator in cancers and plays several biological functions, such as proliferation, migration, invasion, autophagy, and apoptosis.

METHODS

All data were collected through PubMed and CNKI, using terms including "circRNA," "mTOR," "caner," "signaling pathway," "biomarker," "diagnosis," "treatment." Articles published in Chinese and English were included.

RESULTS

In this review, the expression, function, and mechanism of circRNA-associated mTOR in cancers were described. CircRNA-associated-mTOR can regulate the progression and therapy of a variety of cancers in multiple signaling pathways, such as phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/mTOR, mitogen-activated protein kinase (MAPK)/mTOR, and AMP-activated protein kinase (AMPK)/mTOR axis. These cancers including esophageal carcinoma (circLPAR3, ciRS-7), gastric cancer (circNRIP1, hsa_circ_0010882, hsa_circ_0000117, hsa_circ_0072309, and circST3GAL6), colorectal cancer (hsa_circ_0000392, hsa_circ_0084927, hsa_circ_0104631, and circFBXW7), liver cancer (circC16orf62, hsa_circ_100338, hsa_circ_0004001, hsa_circ_0004123, hsa_circ_0075792, hsa_circ_0079299, and hsa_circ_0002130), pancreatic cancer (circ-IARS and circRHOBTB3), renal carcinoma (ciRS-7), bladder cancer (circUBE2K), prostate cancer (circMBOAT2 and circ-ITCH), ovarian cancer (circEEF2, circRAB11FIP1, circMYLK, and circTPCN), endometrial cancer (hsa_circ_0002577 and circWHSC1), lung cancer (circHIPK3, hsa_circ_0001666), thyroid cancer (hsa_circ_0007694 and hsa_circ_0008274), glioma (circGFRA1, circ-MAPK4, circPCMTD1, and hsa_circ_0037251), osteosarcoma (circTCF25), leukemia (circ-PRKDC), and breast cancer (hsa_circ_0000199, circUBAP2, and circWHSC1).

Circular RNA hsa_circ_0051040 Promotes Hepatocellular Carcinoma Progression by Sponging miR-569 and Regulating ITGAV Expression

Accumulating evidence has demonstrated the roles of circular RNAs (circRNAs) in hepatocellular carcinoma (HCC); however, their roles in HCC need to be further studied. Through high-throughput human circRNA microarray analysis of HCC and adjacent normal tissues, we identified hsa_circ_0051040 as a novel candidate circRNA for the diagnosis and treatment of HCC. In this study, we found that hsa_circ_0051040 was overexpressed in HCC tissues and cell lines and that its expression was correlated with poor prognosis. Knockdown of hsa_circ_0051040 inhibited the migration, invasion, and proliferation of HCC cells in vitro and in vivo, whereas overexpression of hsa_circ_0051040 had the opposite effects. Moreover, our data demonstrated that hsa_circ_0051040 acted as a sponge for miR-569 to regulate ITGAV expression and induce EMT progression. Our findings indicated that hsa_circ_0051040 promotes HCC development and progression by sponging miR-569 to increase ITGAV expression. Thus, hsa_circ_0051040 is a good candidate as a therapeutic target.

The lncRNAs involved in regulating the RIG-I signaling pathway

Understanding the targets and interactions of long non-coding RNAs (lncRNAs) related to the retinoic acid-inducible gene-I (RIG-I) signaling pathway is essential for developing interventions, which would enable directing the host inflammatory response regulation toward protective immunity. In the RIG-I signaling pathway, lncRNAs are involved in the important processes of ubiquitination, phosphorylation, and glycolysis, thus promoting the transport of the interferon regulatory factors 3 and 7 (IRF3 and IRF7) and the nuclear factor kappa B (NF-κB) into the nucleus, and activating recruitment of type I interferons (IFN-I) and inflammatory factors to the antiviral action site. In addition, the RIG-I signaling pathway has recently been reported to contain the targets of coronavirus disease-19 (COVID-19)-related lncRNAs. The molecules in the RIG-I signaling pathway are directly regulated by the lncRNA-microRNAs (miRNAs)-messenger RNA (mRNA) axis. Therefore, targeting this axis has become a novel strategy for the diagnosis and treatment of cancer. In this paper, the studies on the regulation of the RIG-I signaling pathway by lncRNAs during viral infections and cancer are comprehensively analyzed. The aim is to provide a solid foundation of information for conducting further detailed studies on lncRNAs and RIG-I in the future and also contribute to clinical drug development.

Exosomal circZNF451 restrains anti-PD1 treatment in lung adenocarcinoma via polarizing macrophages by complexing with TRIM56 and FXR1

BACKGROUND

Although success was achieved in the therapy for a minority of advanced lung adenocarcinoma (LUAD) patients, anti-programmed death 1 (PD1) resistance was found in most LUAD patients. Here, we aimed to uncover a potential role of exosomal circular RNAs (circRNAs) in LUAD refractory to PD1 blockade.  METHODS: circRNA sequencing and qRT-PCR were performed to determine the level of exosomal circRNAs in LUAD patients subsequently treated with anti-PD1. Then, the RNA pulldown, RNA immunoprecipitation, mass spectrometry, chromatin immunoprecipitation, luciferase reporter assays, flow cytometry, RNA sequencing, and in vitro and in vivo models were used to uncover the biological functions and underlying mechanism of circZNF451 in LUAD anti-PD1 treatment resistance.

RESULTS

circRNA sequencing and qRT-PCR identified the up-regulation of exosomal circZNF451 from LUAD patients with progressive disease (PD) compared to those with partial remission (PR) after PD1 blockade therapy. Furthermore, elevated circZNF451 was revealed to be associated with poor prognosis of LUAD patients. Additionally, exosomal circZNF451 was demonstrated to induce an anti-inflammatory phenotype in macrophages and exhaustion of cytotoxic CD8⁺ T cells, and enhanced TRIM56-mediated degradation of FXR1 to activate the ELF4-IRF4 pathway in macrophages. By transgenic mice, knockout of ELF4 in macrophages was found to rescue immunotherapy efficacy in tumors with high level of exosomal circZNF451.

CONCLUSION

Exosomal circZNF451 reshapes the tumor immune microenvironment by inducing macrophages polarization via the FXR1- ELF4-IRF4 axis and is a novel biomarker for predicting the sensitivity of PD1 blockade in LUAD.

Circ_0000064 knockdown attenuates high glucose-induced proliferation, inflammation and extracellular matrix deposition of mesangial cells through miR-424-5p-mediated WNT2B inhibition in cell models of diabetic nephropathy

BACKGROUND

Circular RNA (circRNA) is widely shown to be associated with the development of diabetic nephropathy (DN). Our study aimed to further explore the role of circ_0000064 and provide a new mechanism for its action in DN.

METHODS

Cell models of DN in vitro were constructed by treating human renal mesangial cells (HRMCs) with high glucose (HG). The expression of circ_0000064, microRNA-424-5p (miR-424-5p) and Wnt family member 2B (WNT2B) mRNA was detected by quantitative real-time PCR (qPCR). Cell proliferation was assessed by CCK-8 assay and EdU assay. Cell cycle was characterized by DNA content using flow cytometry. The releases of pro-inflammatory factors were checked using commercial ELISA kits. The expression of cell cycle- and fibrosis-associated proteins was detected by western blot. The interplays between miR-424-5p and circ_0000064 or WNT2B were verified by dual-luciferase reporter assay and RIP assay.

RESULTS

Circ_0000064 and WNT2B were upregulated, while miR-424-5p was downregulated in HG-treated HRMCs. Circ_0000064 knockdown largely attenuated HG-induced proliferation, inflammatory responses and extracellular matrix (ECM) accumulation in HRMCs, and miR-424-5p deficiency reversed the role of circ_0000064 knockdown. MiR-424-5p was a target of circ_0000064, and miR-424-5p directly bound to WNT2B. MiR-424-5p restoration alleviated HG-induced proliferation, inflammatory responses and ECM accumulation in HRMCs, and WNT2B overexpression partially abolished the effects of miR-424-5p.

CONCLUSION

Circ_0000064 knockdown ameliorated HG-induced HRMC dysfunctions through miR-424-5p enrichment-mediated WNT2B inhibition, hinting that circ_0000064 contributed to DN development.

Circular RNA hsa_circ_0003823 promotes the Tumor Progression, Metastasis and Apatinib Resistance of Esophageal Squamous Cell Carcinoma by miR-607/CRISP3 Axis

Background: Circular RNAs (CircRNAs) have attracted a growing interest of research in cancer. The regulatory roles and mechanisms of circRNAs in progression, metastasis and drug resistance of esophageal squamous cell carcinoma (ESCC) needed to be clarified. Our previous study revealed the crucial role of Apatinib in ESCC therapy. However, the correlation between circRNAs and Apatinib resistance remained unclear. Methods: 3 pairs of tumor and paracancerous tissues of ESCC patients were used for RNA sequencing. Western blot analysis, RNA immunoprecipitation (RIP), dual-luciferase reporter assays, apoptosis and animal assays were conducted to confirm the roles and specific mechanisms of hsa_circ_0003823 as well as the effects of it on Apatinib sensitivity in ESCC. Results: Our results revealed that hsa_circ_0003823 was highly expressed in ESCC and associated with poor prognosis. Further results indicated that hsa_circ_0003823 promoted proliferation and metastasis ability of ESCC. In the section of mechanism experiments, hsa_circ_0003823 regulated CRISP3 by targeting microRNA-607 (miR-607) to promote progression of ESCC. Besides, we found that silencing hsa_circ_0003823 improved Apatinib sensitivity. hsa_circ_0003823 resulted in Apatinib resistance by miR-607/CRISP3 axis. Conclusions: In this study, we elucidated the function of hsa_circ_0003823 and its role in promoting tumor progression, metastasis and Apatinib resistance of ESCC through miR-607/CRISP3 axis.

N6-methyladenosine modification of circ_0003215 suppresses the pentose phosphate pathway and malignancy of colorectal cancer through the miR-663b/DLG4/G6PD axis

Circular RNAs (circRNAs) are a recently discovered kind of regulatory RNAs that have emerged as critical biomarkers of various types of cancers. Metabolic reprogramming has gradually been identified as a distinct hallmark of cancer cells. The pentose phosphate pathway (PPP) plays an indispensable role in satisfying the bioenergetic and biosynthetic demands of cancer cells. However, little is known about the role of circRNAs and PPP in colorectal cancer (CRC). The novel circ_0003215 was identified at low levels in CRC and was negatively correlated with larger tumor size, higher TNM stage, and lymph node metastasis. The decreased level of circ_0003215 was resulted from the RNA degradation by m6A writer protein YTHDF2. A series of functional assays demonstrated that circ_0003215 inhibited cell proliferation, migration, invasion, and CRC tumor metastasis in vivo and in vitro. Moreover, circ_0003215 regulated the expression of DLG4 via sponging miR-663b, thereby inducing the metabolic reprogramming in CRC. Mechanismly, DLG4 inhibited the PPP through the K48-linked ubiquitination of glucose-6-phosphate dehydrogenase (G6PD). Taken together, we have identified m6A-modified circ_0003215 as a novel regulator of metabolic glucose reprogramming that inhibited the PPP and the malignant phenotype of CRC via the miR-663b/DLG4/G6PD axis.