CircTHBS1 drives gastric cancer progression by increasing INHBA mRNA expression and stability in a ceRNA- and RBP-dependent manner

Curcumin alleviates renal fibrosis in chronic kidney disease by targeting the circ_0008925-related pathway

BACKGROUND

Curcumin has been shown to inhibit renal fibrosis, but whether curcumin mediates renal fibrosis progression by regulating the circular RNA (circRNA)-related pathway remain unclear.

METHODS

TGF-β1 was used to construct renal injury and fibrosis cell model. Cell growth was evaluated by cell counting kit 8 assay, EdU assay and flow cytometry. Fibrosis marker and interleukin 6 signal transducer (IL6ST) protein levels were measured using western bolt analysis. Inflammation factor concentrations were determined by ELISA. Circ_0008925, miR-204-5p and IL6ST expression was assessed by qRT-PCR. Unilateral ureteral obstruction (UUO) mice models were constructed to assess the role of curcumin in vivo.

RESULTS

Curcumin treatment alleviated TGF-β1-induced HK-2 cell apoptosis, inflammation and fibrosis in vitro, as well as relieved renal injury in UUO mice models in vivo. Circ_0008925 was highly expressed in TGF-β1-induced HK-2 cells and its expression was inhibited by curcumin. Circ_0008925 could sponge miR-204-5p to positively regulate IL6ST. The inhibition effect of curcumin on TGF-β1-induced HK-2 cell injury and fibrosis was reversed by circ_0008925 overexpression, miR-204-5p inhibitor or IL6ST upregulation. Besides, circ_0008925 knockdown inhibited TGF-β1-induced HK-2 cell injury and fibrosis by suppressing IL6ST expression.

CONCLUSION

Curcumin relieved renal fibrosis through regulating circ_0008925/miR-204-5p/IL6ST axis.

CircATP5C1 promotes triple-negative breast cancer progression by binding IGF2BP2 to modulate CSF-1 secretion

Triple-negative breast cancer (TNBC) is a common malignant disease among females and severely threatens the health of women worldwide. Nowadays, circular RNAs (circRNAs) aroused our interest for their functions in human cancers, including TNBC. However, the mechanism of most circRNAs in the progression of TNBC remains unclear. We found a novel circRNA named circATP5C1, whose function in TNBC remains uncovered. Tissue microarray was used to analyze the association between the expression of circATP5C1 and the prognoses of TNBC patients. Gain-and loss-of-function experiments were performed to validate the biological functions of circATP5C1 in different TNBC cell lines. RNA-seq analyses were conducted to find out the target genes regulated by circATP5C1. RNA pull-down assay and mass spectrometry were used to select the proteins associated with circATP5C1. RNA FISH-immunofluorescence and RNA immunoprecipitation (RIP) were complemented to validate the interaction between circATP5C1 and its binding protein. CircATP5C1 was identified to have predictive function in prognosis of TNBC patients. CircATP5C1 advanced the progression of TNBC cells. Mechanistically, Colony stimulating factor 1 (CSF-1) is a vital downstream gene regulated by circATP5C1. The alteration of CSF-1 expression level was validated due to the interaction between circATP5C1 and insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2). Rescue experiments demonstrated that circATP5C1 accelerates the progression of TNBC partly via binding with IGF2BP2 to increase the secretion of CSF-1. This study uncovers a novel mechanism of circATP5C1/IGF2BP2/CSF-1 pathway in regulating progression of TNBC.

Emerging role and clinical applications of circular RNAs in human diseases

Circular RNAs (circRNAs) are a large family of non-coding RNAs characterized by a single-stranded, covalently closed structure, predominantly synthesized through a back-splicing mechanism. While thousands of circRNAs have been identified, only a few have been functionally characterized. Although circRNAs are less abundant than other RNA types, they exhibit exceptional stability due to their covalently closed structure and demonstrate high cell and tissue specificity. CircRNAs play a critical role in maintaining cellular homeostasis by influencing gene transcription, translation, and post-translation processes, modulating the immune system, and interacting with mRNA, miRNA, and proteins. Abnormal circRNA expression has been associated with a wide range of human diseases and various infections. Due to their remarkable stability in body fluids and tissues, emerging research suggests that circRNAs could serve as diagnostic and therapeutic biomarkers for these diseases. This review focuses on the emerging role of circRNAs in various human diseases, exploring their biogenesis, molecular functions, and potential clinical applications as diagnostic and therapeutic biomarkers with current evidence, challenges, and future perspectives. The key theme highlights the significance of circRNAs in regulating gene expression, their involvement in diseases like cancer, neurodegenerative disorders, cardiovascular diseases, and diabetes, and their potential use in translational medicine for developing novel therapeutic strategies. We also discuss recent clinical trials involving circRNAs. Thus, this review is important for both basic researchers and clinical scientists, as it provides updated insights into the role of circRNAs in human diseases, aiding further exploration and advancements in the field.

CircDUSP16 mediates the effect of triple-negative breast cancer in pirarubicin via the miR-1224-3p/TFDP2 axis

Triple-negative breast cancer (TNBC) is an aggressive molecular subtype of breast cancer characterized by a high recurrence rate, poor prognosis, and elevated mortality. Identifying novel molecular targets is crucial for developing more effective therapeutic strategies against TNBC. Recent studies have highlighted the role of circular RNAs (circRNAs) in the progression of TNBC. In this study, we identified and validated that circDUSP16 (hsa_circ_0003855) is significantly upregulated in TNBC cells, tissues, and plasma exosomes. Functional assays in vitro demonstrated that overexpression of circDUSP16 promoted the proliferation, migration and invasion of TNBC cells, weathers circDUSP16 knockdown exerted the opposite effect. In vivo studies confirmed that circDUSP16 knockdown can inhibit tumor growth. Using bioinformatics analysis, circDUSP16/miR-1224-3p/TFDP2 pathway was predicted and cascaded. Mechanistically, circDUSP16 was shown to promote the progression of TNBC via the miR-1224-3p/TFDP2 axis. Additionally, THP, a commonly used anthracycline chemotherapy drug, was found to downregulate circDUSP16, suggesting that its therapeutic effects on TNBC may be mediated through circDUSP16/miR-1224-3p/TFDP2 pathway. Our findings suggest that circDUSP16 is a promising biomarker and potential therapeutic target for TNBC.

CircINADL promotes nasopharyngeal carcinoma metastasis by inhibiting HuR ubiquitin degradation and disrupting the hippo signaling pathway

Distant metastasis is a primary factor contributing to the low survival rate of patients with nasopharyngeal carcinoma (NPC). Circular RNAs (circRNAs) are increasingly recognized for their roles in cancer initiation and progression. However, the mechanisms underlying the abnormal expression and biological function of circRNA in NPC remain unclear. In this study, we identified a new circRNA, circINADL, which was upregulated in NPC tissues and positively correlated with the clinical stage of NPC. We found that the FUS RNA binding protein (FUS) promoted the transcription of circINADL in NPC cells. Elevated circINADL levels were shown to enhance NPC cells metastasis. Mechanistically, circINADL attenuated the interaction between human antigen R (HuR) and the E3 ubiquitin ligase β-TrCP, thereby inhibited the ubiquitination and degradation of HuR. Consequently, CircINADL enhanced the stability of the HuR target gene Yes1-associated transcriptional regulator (YAP1), leading to the dysregulation of the Hippo signaling pathway. In conclusion, our study reveals the function of circINADL in promoting NPC metastasis and highlights its potential as a biomarker and therapeutic target for NPC treatment.

Identification of tumor-antigen signatures and immune subtypes for mRNA vaccine selection in muscle-invasive bladder cancer

BACKGROUND

Muscle-invasive bladder cancer continues to lack reliable diagnostic and prognostic biomarkers. Recently, tumor vaccines targeting specific molecules have emerged as a promising treatment in inhibiting tumor progression, which was rekindled under the background of coronavirus disease-2019 pandemic. However, the application of mRNA vaccine targeting muscle-invasive bladder cancer-specific antigens remains limited, and there has been a lack of comprehensive studies or validations to identify suitable patient subgroups for vaccination. This study aims to explore novel muscle-invasive bladder cancer antigen signatures to identify patients most likely to benefit from vaccination.

METHODS

Gene expression profiles of muscle-invasive bladder cancer samples, along with corresponding clinical data, were retrieved from the Cancer Genome Atlas Program. The least absolute shrinkage and selection operator model was applied to develop signatures for stratifying muscle-invasive bladder cancer patients. Prognostic accuracy of each factor was assessed using receiver operating characteristic analysis. Tumor Immune Estimation Resource was employed to visualize the relationship between the proportion of antigen-presenting cells and the expression of selected genes. The CIBERSORT and WGCNA R packages were used to identify differences in immune infiltration levels across muscle-invasive bladder cancer subgroups. Additionally, the STRING database and Cytoscape were used to construct the protein-protein interaction network. CCK-8 and colony formation assays were employed in invitro experiments.

RESULTS

A total of 49 potential tumor antigens were identified. Using least absolute shrinkage and selection operator Cox regression, 14 tumor antigens were selected to develop a risk evaluation signature. The risk score signature can serve as a valuable tool for predicting the outcomes of muscle-invasive bladder cancer patients. Based on differential clinical, molecular, and immune-related gene profiles, muscle-invasive bladder cancer patients were classified into 2 subtypes: the immune "cold" subtype (immune score 1) and the immune "hot" subtype (immune score 2). The immune score signature, developed using a logistic score model, effectively distinguishes between patients more likely to belong to immune score 1 or 2. Notably, patients with a high risk score exhibited a higher proportion of immune score 2 compared to those with a low risk score. Additionally, the prognostic accuracy was significantly enhanced when the risk score and immune score were combined. Different tumor subtypes displayed distinct immune landscapes and signaling pathways. Moreover, novel tumor antigens associated with oxidative stress were identified.

CONCLUSION

The risk score and immune score signatures based on tumor antigens have identified potential effective neo-antigens for the development of mRNA vaccines targeting muscle-invasive bladder cancer. Patients with low risk score and immune score 1 subtype are more likely to benefit from mRNA vaccination. Additionally, this study highlights the critical role of oxidative stress in modulating the efficacy of the mRNA vaccine.

hsa_circ_0001599 promotes odontogenic differentiation of human dental pulp stem cells by increasing ITGA2 expression and stability

Dental pulp regeneration is significantly aided by human dental pulp stem cells (hDPSCs). An increasing number of studies have demonstrated that circular RNAs (circRNAs) are crucial in the multidirectional differentiation of many mesenchymal stem cells, but their specific functions and mechanisms remain unknown. This work aimed at elucidating the molecular mechanism by which hsa_circ_0001599 works in hDPSCs during odontogenic differentiation. The expression of hsa_circ_0001599 in hDPSCs and dental pulp tissue was determined by using quantitative real-time PCR (qRT‒PCR). The role of hsa_circ_0001599 in the odontogenic differentiation of hDPSCs and its mechanism were studied using a variety of in vivo and in vitro assessments. The odontogenic differentiation of hDPSCs was facilitated by the overexpression of hsa_circ_0001599, which activated the PI3K/AKT signalling pathway in vitro. In vivo, hsa_circ_0001599 can promote the formation of new dentin-like structures. Mechanistically, hsa_circ_0001599 enhanced ITGA2 expression by sponging miR-889-3p. Furthermore, hsa_circ_0001599 interacts with the methylation reader hnRNPA2B1, promoting hnRNPA2B1 translocation from the nucleus to the cytoplasm and increasing ITGA2 mRNA stability. This research revealed the important role of hsa_circ_0001599 in odontogenic differentiation. Thus, hDPSCs engineered with hsa_circ_0001599 have the potential to be effective therapeutic targets for dental pulp repair and regeneration.

Senescence-related circRNA circHIF-1α is associated with pancreatic cancer progression

Recently, there has been growing interest in the role of circular RNAs (circRNAs) in the progression of human cancers. Cellular senescence, a known anti-tumour mechanism, has been observed in several types of cancer. However, the regulatory interplay of circRNAs with cellular senescence in pancreatic cancer (PC) is still unknown. Therefore, we identified circHIF-1α, hsa_circ_0007976, which was downregulated in senescent cells using circRNA microarray analysis. Meanwhile, significantly upregulated expression of circHIF-1α in pancreatic cancer tissue detected by reverse transcription-polymerase chain reaction (RT-qPCR) and in situ hybridization (ISH). High circHIF-1α expression levels were found to independently predict poor survival outcomes. Subsequent treatments with DOX and H2O2 resulted in significantly lower levels of circHIF-1α. CircHIF-1α knockdown induces cellular senescence and suppresses PC proliferation in vitro experiments. The ability of circHIF-1α knockdown to suppress the progression of PC cells was further confirmed in vivo experiments. Our results showed that circHIF-1α is mainly presented in the nucleus of PC cells, also in the cytoplasm. Mechanistically, circHIF-1α inhibited senescence and accelerated the progression of PC cells through miR-375 sponging, thereby promoting HIF-1α expression levels. Nuclear circHIF-1α interacted with human antigen R protein (HUR) to increase HIF-1α expression. Thus, our results demonstrated that circHIF-1α ameliorates senescence and exacerbates growth in PC cells by increasing HIF-1α through targeting miR-375 and HUR, suggesting that targeting circHIF-1α offers a potential therapeutic candidate for PC.

Comprehensive analysis of inhibin-β A as a potential biomarker for gastrointestinal tract cancers through bioinformatics approaches

Inhibin, β, which is also known as INHBA, encodes a protein that belongs to the Transforming Growth factor-β (TGF-β) superfamily, which plays a pivotal role in cancer. Gastrointestinal tract (GI tract) cancer refers to the cancers that develop in the colon, liver, esophagus, stomach, rectum, pancreas, and bile ducts of the digestive system. The role of INHBA in all GI tract cancers remains understudied. By utilizing GEPIA2, which uses transcriptomic data from TCGA, we examined the expression of INHBA across different GI tract cancers. The results revealed consistent upregulation of INHBA in all TCGA GI tract cancers, except for liver hepatocellular carcinoma, where it showed downregulation compared to normal tissues, along with GTEx normal samples. Significant differences in INHBA expression were noted in adenocarcinomas of the colon, pancreas, rectum, and stomach, while no such differences were observed in cholangiocarcinoma and liver cancer. Moreover, a comprehensive bioinformatics analysis has been done to demonstrate that the differences in expression levels are significantly related to pathological tumor stages and prognosis in different GI tract cancers. Mucinous adenocarcinoma, esophageal squamous cell carcinoma, and stomach adenocarcinoma show a higher frequency of INHBA alteration and are primarily linked to mutations and amplifications. DNA methylation, immune infiltration, functional enrichment analysis, the genes associated with INHBA, and survival analysis in all TCGA GI tract cancers have been extensively analyzed. In colon and stomach cancers, increased INHBA expression significantly correlates with poorer overall survival (OS). However, in colon and pancreatic adenocarcinoma, higher expression is significantly associated with worse disease-free survival (DFS). Additionally, INHBA expression exhibited a positive correlation with cancer-associated fibroblasts across all gastrointestinal (GI) tract cancers. The KEGG pathway analysis revealed that INHBA and its interacting proteins are involved in several pathways, including TGF-beta signaling, Signalling pathways regulating pluripotency of stem cells, colorectal cancer, pancreatic cancer, AGE-RAGE signaling, and so on as major pathways. These findings demonstrate that INHBA could serve as a potential biomarker therapeutic target for GI tract cancer.

LINC01094 promotes gastric cancer through dual targeting of CDKN1A by directly binding RBMS2 and HDAC1

BACKGROUND

Accumulating studies have focused on long noncoding RNAs (lncRNAs) because of their regulatory effects on multiple cancers. However, the biological functions and molecular mechanisms of lncRNAs in gastric cancer (GC) remain to be elucidated in depth.

METHODS

Long intergenic nonprotein coding RNA 1094 (LINC01094), a differentially expressed lncRNA between GC tissues and adjacent normal tissues, was identified. Moreover, gain- and loss-of-function experiments in vitro and in vivo were carried out. To understand the mechanisms underlying the regulatory effects of LINC01094, we performed RNA pull-down assays, RNA immunoprecipitation assays, chromatin immunoprecipitation assays, luciferase reporter assays, etc. RESULTS: LINC01094 was markedly upregulated in GC tissues and cell lines, and LINC01094 upregulation was positively correlated with GC malignant behaviours in vitro and in vivo. Mechanistically, LINC01094 downregulated the expression of CDKN1A by interacting with RNA binding motif single stranded interacting protein 2 (RBMS2) and histone deacetylase 1 (HDAC1). Additionally, LINC01094 was confirmed to sponge miR-128-3p and participate in the LINC01094-miR-128-3p-RUNX family transcription factor 1 (RUNX1) feedback loop. Finally, Ro 5-3335, a validated RUNX1 inhibitor, was explored for anticancer drug development in GC.

CONCLUSIONS

The LINC01094-miR-128-3p-RUNX1 feedback loop downregulates CDKN1A and promotes GC cooperatively with RBMS2 and HDAC1. Furthermore, Ro 5-3335 may hold promising therapeutic potential in the treatment of GC. Hence, our study found an oncogenic lncRNA, LINC01094, which could be a promising target for cancer treatment and diagnosis.

The potential of circular RNAs as biomarkers and therapeutic targets for gastric cancer: A comprehensive review

BACKGROUND

Gastric cancer (GC) is a global health concern, contributing significantly to cancer-related mortality rates. Early detection is vital for improving patient outcomes. Recently, circular RNAs (circRNAs) have emerged as crucial players in the development and progression of various cancers, including GC.

AIM

This comprehensive review underscores the promising potential of circRNAs as innovative biomarkers for the early diagnosis of GC, as well as their possible utility as therapeutic targets for this life-threatening disease. Specifically, the review focuses on recent findings, mechanistic insights, and clinical applications of circRNAs in GC.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Dysregulation of circRNAs has been consistently observed in GC tissues, offering potential diagnostic value due to their stability in bodily fluids such as blood and urine. For instance, circPTPN22 and hsa_circ_000200. Furthermore, the expression levels of circRNAs such as circCUL2, hsa_circ_0000705 and circSHKBP1 have shown strong associations with critical clinical features of GC, including diagnosis, prognosis, tumor size, lymph node metastasis, tumor-node-metastasis (TNM) stage, and treatment response. Additionally, circRNAs such as circBGN, circLMO7, and circMAP7D1 have shown interactions with specific microRNAs (miRNAs), proteins, and other molecules that play key roles in development and progression of GC. This further highlighting their potential as therapeutic targets. Despite their potential, several challenges need to be addressed to effectively apply circRNAs as GC biomarkers. These include standardizing detection methods, establishing cutoff values for diagnostic accuracy, and validating findings in larger patient cohorts. Moreover, the functional mechanisms by which circRNAs contribute to GC pathogenesis and therapeutic resistance warrant further investigation. Advances in circRNAs research could provide valuable insights into the early detection and targeted treatment of GC, ultimately improving patient outcomes.

m6A-modified circXPO1 accelerates colorectal cancer progression via interaction with FMRP to promote WWC2 mRNA decay

BACKGROUND

Recent evidence has demonstrated the vital roles of circular RNAs (circRNAs) in the progression of colorectal cancer (CRC); however, their functions and mechanisms in CRC need to be further explored. This study aimed to uncover the biological function of circXPO1 in CRC progression.

METHODS

CircXPO1 was identified by Sanger sequencing, RNase R, and actinomycin D treatment assays. Colony formation, scratch, transwell assays, and mouse xenograft models were adopted to evaluate CRC cell growth and metastasis in vitro and in vivo. Subcellular expression of circXPO1 was detected by FISH and nuclear-cytoplasmic separation assays. Molecular mechanisms were investigated by MeRIP, RIP, and RNA pull-down assays. Target molecular expression was detected by RT-qPCR, Western blotting and immunohistochemical staining.

RESULTS

circXPO1 was up-regulated in CRC tissues and cells, which indicated a poor prognosis of CRC patients. circXPO1 deficiency delayed the growth, EMT, and metastasis of CRC cells. Mechanistical experiments indicated that down-regulation of ALKBH5 enhanced IGF2BP2-mediated m6A modification of circXPO1 to increase circXPO1 expression. Furthermore, circXPO1 interacted with FMRP to reduce the mRNA stability of WWC2, which consequently resulted in Hippo-YAP pathway activation. Rescue experiments suggested that WWC2 overexpression abrogated circXPO1-mediated malignant capacities of CRC cells. The in vivo growth and liver metastasis of CRC cells were restrained by circXPO1 depletion or WWC2 overexpression.

CONCLUSIONS

m6A-modified circXPO1 by ALKBH5/IGF2BP2 axis destabilized WWC2 via interaction with FMRP to activate Hippo-YAP pathway, thereby facilitating CRC growth and metastasis. Targeting circXPO1 might be a potential therapeutic strategy for CRC.

Hsa_circ_0000825 promotes the progression of laryngeal squamous cell carcinoma by sponging miR-766 and interacting with ELAVL1

Emerging evidence suggests that circular RNAs (circRNAs) are involved in the regulation of tumourigenesis and progression of a variety of malignant tumours. In this study, we aimed to identify laryngeal squamous cell carcinoma (LSCC)-specific circRNAs and explore their biological functions and underlying molecular mechanisms. Employing microarray and qRT-PCR, hsa_circ_0000825 was found to be significantly increased in LSCC tissues versus para-cancerous tissues. High hsa_circ_0000825 expression was positively associated with advanced clinical stages, lymph node metastasis, and poor survival. Furthermore, the overexpression of hsa_circ_0000825 in TU177 and AMC-HN-8 cells promoted cell proliferation. Transwell assays showed enhanced migration and invasion of TU177 and AMC-HN-8 cells upon overexpression of hsa_circ_0000825. Conversely, the knockdown of hsa_circ_0000825 had the opposite effect. Xenograft tumours in BALB/c nude mice derived from hsa_circ_0000825-overexpressed TU177 cells showed greater volume and weight than those derived from control TU177 cells. Mechanistically, nuclear-cytoplasmic fractionation assay confirmed that hsa_circ_0000825 was mainly located in the cytoplasm of TU177 and AMC-HN-8 cells. The AGO2-RNA immunoprecipitation (RIP) assay revealed that hsa_circ_0000825 was significantly enriched in the AGO2-precipitated complex in both TU177 and AMC-HN-8 cells, suggesting that this circRNA may function via a competitive endogenous RNA (ceRNA) mechanism. Next, bioinformatics analysis, biotinylated-oligo pull-down assay and dual-luciferase reporter assay verified that miR-766 could be sponged by hsa_circ_0000825 and also target 3'UTR of HOXD10 mRNA. Moreover, miR-766 was shown to be involved in the pro-oncogenic effect of hsa_circ_0000825. This occurred via the mediation of hsa_circ_0000825-enhanced HOXD10 mRNA by the ceRNA mechanism in TU177 and AMC-HN-8 cells. Besides, RNA-binding protein (RBP) ELAVL1 interacted with hsa_circ_0000825 in TU177 and AMC-HN-8 cells, as revealed through bioinformatics analysis, biotinylated-oligo pull-down assays, and RIP assays. ELAVL1 knockdown decreased cell proliferation by 38 % and 34 % in hsa_circ_0000825-overexpressed TU177 and AMC-HN-8 cells (P < 0.05). Similarly, ELAVL1 was involved in the pro-migration and pro-invasion effects of hsa_circ_0000825 overexpression. In addition, comprehensive analysis of mRNA-seq in hsa_circ_0000825-overexpressed TU177 cells, as well as catRAPID and TCGA databases, suggested that ITGB2, HOXD10, and MTCL1 might be crucial downstream target mRNAs of ELAVL1 in LSCC, participating in the hsa_circ_0000825-ELAVL1 axis pro-oncogenic effect. Taken together, hsa_circ_0000825 plays a pro-oncogenic role in LSCC via the miR-766/HOXD10 axis and ELAVL1 and may serve as a promising specific biomarker and therapeutic target for LSCC.

CircZFR promotes colorectal cancer progression via stabilizing BCLAF1 and regulating the miR-3127-5p/RTKN2 axis

Aberrant expression of circular RNAs (circRNAs) is frequently linked to colorectal cancer (CRC). Here, we identified circZFR as a promising biomarker for CRC diagnosis and prognosis. CircZFR was upregulated in CRC tissues and serum exosomes and its level was linked to cancer incidence, advanced-stages, and metastasis. In both in vitro and in vivo settings, circZFR promoted the growth and spread while suppressing apoptosis of CRC. Exosomes with circZFR overexpression promoted the proliferation and migration of cocultured CRC cells. Mechanistically, epithelial splicing regulatory protein 1 (ESRP1) in CRC cells may enhance the production of circZFR. BCL2-associated transcription factor 1 (BCLAF1) bound to circZFR, which prevented its ubiquitinated degradation. Additionally, circZFR sponged miR-3127-5p to boost rhotekin 2 (RTKN2) expression. Our TCP1-CD-QDs nanocarrier was able to carry and deliver circZFR siRNA (si-circZFR) to the vasculature of CRC tissues and cells, which inhibited the growth of tumors in patient-derived xenograft (PDX) models. Taken together, our results show that circZFR is an oncogenic circRNA, which promotes the development and spread of CRC in a BCLAF1 and miR-3127-5p-dependent manner. CircZFR is a possible serum biopsy marker for the diagnosis and a desirable target for further treatment of CRC.

Nanoparticles-Delivered Circular RNA Strategy as a Novel Antitumor Approach

Anticancer therapy urgently needs the development of novel strategies. An innovative molecular target is represented by circular RNAs (circRNAs), single-strand RNA molecules with the 5' and 3' ends joined, characterized by a high stability. Although circRNA properties and biological functions have only been partially elucidated, their relationship and involvement in the onset and progression of cancer have emerged. Specific targeting of circRNAs may be obtained with antisense oligonucleotides and silencing RNAs. Nanotechnology is at the forefront of research for perfecting their delivery. Continuous efforts have been made to develop novel nanoparticles (NPs) and improve their performance, materials, and properties regarding biocompatibility and targeting capabilities. Applications in various fields, from imaging to gene therapy, have been explored. This review sums up the smart strategies developed to directly target circRNAs with the fruitful application of NPs in this context.

CircUBA2 promotes the cancer stem cell-like properties of gastric cancer through upregulating STC1 via sponging miR-144-5p

BACKGROUND

Cancer stem cells (CSCs) are critical factors that limit the effectiveness of gastric cancer (GC) therapy. Circular RNAs (circRNAs) are confirmed as important regulators of many cancers. However, their role in regulating CSC-like properties of GC remains largely unknown. Our study aimed to investigate the role of circUBA2 in CSC maintenance and the underlying mechanisms.

METHODS

We identified circUBA2 as an upregulated gene using circRNA microarray analysis. qRT-PCR was used to examine the circUBA2 levels in normal and GC tissues. In vitro and in vivo functional assays were performed to validate the role of circUBA2 in proliferation, migration, metastasis and CSC-like properties of GC cell. The relationship between circUBA2, miR-144-5p and STC1 was characterised using bioinformatics analysis, a dual fluorescence reporter system, FISH, and RIP assays.

RESULTS

CircUBA2 expression was significantly increased in GC tissues, and patients with GC with high circUBA2 expression had a poor prognosis. CircUBA2 enhances CSC-like properties of GC, thereby promoting cell proliferation, migration, and metastasis. Mechanistically, circUBA2 promoted GC malignancy and CSC-like properties by acting as a sponge for miR-144-5p to upregulate STC1 expression and further activate the IL-6/JAK2/STAT3 signaling pathway. More importantly, the ability of circUBA2 to enhance CSC-like properties was inhibited by tocilizumab, a humanised Interleukin-6 receptor (IL-6R) antibody. Thus, circUBA2 knockdown and tocilizumab synergistically inhibited CSC-like properties.

CONCLUSIONS

Our study demonstrated the critical role of circUBA2 in regulating CSC-like properties in GC. CircUBA2 may be a promising prognostic biomarker for GC.

hsa_circ_0000518 stimulates the malignant progression of hepatocellular carcinoma via regulating ITGA5 to activate the Warburg effect

Studies have shown that the abnormal expression of circular RNA (circRNA) is inextricably linked to hepatocellular carcinoma (HCC). Recently, hsa_circ_0000518 (circ_0000518) was discovered in many cancer progressions. However, its function in HCC is still unclear. Through GEO database analysis combined with gene expression detection of HCC related clinical samples and cell lines, we identified that circ_0000518 was abnormally overexpressed in HCC. Cell and animal model experiments jointly indicated that circ_0000518 can stimulate HCC cell proliferation, migration, invasion and suppress apoptosis. Furthermore, we also found that knocking down the circ_0000518 could inhibit the Warburg effect in HCC cells. Mechanistically, circ_0000518 was found to be primarily localized in the cytoplasm, and sponge hsa-miR-326 (miR-326) promoted integrin alpha 5 (ITGA5) expression. In addition, circ_0000518 could enhance the stability of HuR-mediated ITGA5 mRNA, thereby activating the Warburg effect. In conclusion, this study elucidated that circ_0000518 was a cancer-promoting circRNA, which could enhance ITGA5 expression through competing endogenous RNAs (ceRNA) and RNA Binding Protein (RBP) mechanisms, thus facilitating the development of HCC. It provides a meaningful diagnostic and therapeutic target for HCC.

Positive GLI1/INHBA feedback loop drives tumor progression in gastric cancer

GLI1, a key transcription factor of the Hedgehog (Hh) signaling pathway, plays an important role in the development of cancer. However, the function and mechanisms by which GLI1 regulates gene transcription are not fully understood in gastric cancer (GC). Here, we found that GLI1 induced the proliferation and metastasis of GC cells, accompanied by transcriptional upregulation of INHBA. This increased INHBA expression exerted a promoting activity on Smads signaling and then transcriptionally activated GLI1 expression. Notably, our results demonstrate that disrupting the interaction between GLI1 and INHBA could inhibit GC tumorigenesis in vivo. More intriguingly, we confirmed the N6-methyladenosine (m6A) activation mechanism of the Helicobacter pylori/FTO/YTHDF2/GLI1 pathway in GC cells. In conclusion, our study confirmed that the GLI1/INHBA positive feedback loop influences GC progression and revealed the mechanism by which H. pylori upregulates GLI1 expression through m6A modification. This positive GLI1/INHBA feedback loop suggests a novel noncanonical mechanism of GLI1 activity in GC and provides potential therapeutic targets for GC treatment.

CircRNA Regulation of T Cells in Cancer: Unraveling Potential Targets

T lymphocytes play a critical role in antitumor immunity, but their exhaustion poses a significant challenge for immune evasion by malignant cells. Circular RNAs (circRNAs), characterized by their covalently closed looped structure, have emerged as pivotal regulators within the neoplastic landscape. Recent studies have highlighted their multifaceted roles in cellular processes, including gene expression modulation and protein function regulation, which are often disrupted in cancer. In this review, we systematically explore the intricate interplay between circRNAs and T cell modulation within the tumor microenvironment. By dissecting the regulatory mechanisms through which circRNAs impact T cell exhaustion, we aim to uncover pathways crucial for immune evasion and T cell dysfunction. These insights can inform innovative immunotherapeutic strategies targeting circRNA-mediated molecular pathways. Additionally, we discuss the translational potential of circRNAs as biomarkers for therapeutic response prediction and as intervention targets. Our comprehensive analysis aims to enhance the understanding of immune evasion dynamics in the tumor microenvironment by facilitating the development of precision immunotherapy.

Potential therapeutic strategy for cancer: Multi-dimensional cross-talk between circRNAs and parental genes

In many ways, circular RNAs (circRNAs) have been demonstrated to be crucial in the onset and advancement of cancer throughout the last ten years and have become a new focus of intense research in the field of RNAs. Accumulating studies have demonstrated that circRNAs can regulate parental gene expression via a variety of biological pathways. Furthermore, research into the complex interactions between circRNAs and their parental genes will shed light on their biological roles and open up new avenues for circRNAs' potential clinical translational uses. However, to date, multi-dimensional cross-talk between circRNAs and parental genes have not been systematically elucidated. Particularly intriguing is circRNA's exploration of tumor targeting, and potential therapeutic uses based on the parental gene regulation perspective. Here, we discuss their biogenesis, take a fresh look at the molecular mechanisms through which circRNAs control the expression of their parental genes in cancer. We further highlight We further highlight the latest circRNA clinical translational applications, including prognostic diagnostic markers, cancer vaccines, gDNA, and so on. Demonstrating the potential benefits and future applications of circRNA therapy.

CircPRMT5 promotes progression of osteosarcoma by recruiting CNBP to regulate the translation and stability of CDK6 mRNA

Research has demonstrated that circular RNAs (circRNAs) exert critical functions in the occurrence and progression of numerous malignant tumors. CircPRMT5 was recently reported to be involved in the pathogenesis of cancers. However, the potential role of circPRMT5 in osteosarcoma needs further investigation. In present study, our results suggested that circPRMT5 was highly upregulated in osteosarcoma cells and mainly localizes in the cytoplasm. CircPRMT5 promoted the proliferation, migration and invasion capacities of osteosarcoma cells, and suppressed cell apoptosis. Knockdown of circPRMT5 exerted the opposite effects. Mechanically, circPRMT5 promoted the binding of CNBP to CDK6 mRNA, which enhanced the stability of CDK6 mRNA and facilitated its translation, thereby promoting the progression of osteosarcoma. Knockdown of CDK6 reversed the promoting effect of circPRMT5 on osteosarcoma cells. These findings suggest that circPRMT5 promotes osteosarcoma cell malignant activity by recruiting CNBP to regulate the translation and stability of CDK6 mRNA. Thus, circPRMT5 may represent a promising therapeutic target for osteosarcoma.

CircTHBS1 promotes trophoblast cell migration and invasion and inhibits trophoblast apoptosis by regulating miR-136-3p/IGF2R axis

The precise molecular mechanism behind fetal growth restriction (FGR) is still unclear, although there is a strong connection between placental dysfunction, inadequate trophoblast invasion, and its etiology and pathogenesis. As a new type of non-coding RNA, circRNA has been shown to play a crucial role in the development of FGR. This investigation identified the downregulation of hsa_circ_0034533 (circTHBS1) in FGR placentas through high-sequencing analysis and confirmed this finding in 25 clinical placenta samples using qRT-PCR. Subsequent in vitro functional assays demonstrated that silencing circTHBS1 inhibited trophoblast proliferation, migration, invasion, and epithelial mesenchymal transition (EMT) progression and promoted apoptosis. Furthermore, when circTHBS1 was overexpressed, cell function experiments showed the opposite result. Analysis using fluorescence in situ hybridization revealed that circTHBS1 was primarily found in the cytoplasmic region. Through bioinformatics analysis, we anticipated the involvement of miR-136-3p and IGF2R in downstream processes, which was subsequently validated through qRT-PCR and dual-luciferase assays. Moreover, the inhibition of miR-136-3p or the overexpression of IGF2R partially reinstated proliferation, migration, and invasion abilities following the silencing of circTHBS1. In summary, the circTHBS1/miR-136-3p/IGF2R axis plays a crucial role in the progression and development of FGR, offering potential avenues for the exploration of biological indicators and treatment targets.

Emerging roles of circular RNAs in regulating the hallmarks of thyroid cancer

Thyroid cancer is a prevalent endocrine malignancy with increasing incidence in recent years. Although most thyroid cancers grow slowly, they can become refractory, leading to a high mortality rate once they exhibit recurrence, metastasis, resistance to radioiodine therapy, or a lack of differentiation. However, the mechanisms underlying these malignant characteristics remain unclear. Circular RNAs, a type of closed-loop non-coding RNAs, play multiple roles in cancer. Several studies have demonstrated that circular RNAs significantly influence the development of thyroid cancers. In this review, we summarize the circular RNAs identified in thyroid cancers over the past decade according to the hallmarks of cancer. We found that eight of the 14 hallmarks of thyroid cancers are regulated by circular RNAs, whereas the other six have not been reported to be correlated with circular RNAs. This review is expected to help us better understand the roles of circular RNAs in thyroid cancers and accelerate research on the mechanisms and cure strategies for thyroid cancers.

CircNUP54 promotes hepatocellular carcinoma progression via facilitating HuR cytoplasmic export and stabilizing BIRC3 mRNA

Circular RNAs (circRNAs) have been implicated in tumorigenesis and progression of various cancers. However, the underlying mechanisms of circRNAs in hepatocellular carcinoma (HCC) have not been fully elucidated. Herein, a new oncogenic circRNA, hsa_circ_0070039 (circNUP54), was identified to be significantly upregulated in HCC through circRNA sequencing. As verified in 68 HCC samples, circNUP54 overexpression was correlated with aggressive cancerous behaviors and poor outcomes. Moreover, the function experiments showed that knockdown of circNUP54 inhibited the malignant progression of HCC in vitro and in vivo, whereas overexpression of circNUP54 had the opposite role. Mechanistic investigations carried out by RNA pull-down, RNA immunoprecipitation, and immunofluorescence revealed that circNUP54 interacted with the RNA-binding protein Hu-antigen R (HuR) and promoted its cytoplasmic export. The cytoplasmic accumulation of HuR stabilized the downstream BIRC3 mRNA through its binding to the 3' UTR region. Consequently, the encoded protein of BIRC3, cellular inhibitor of apoptosis 2 (cIAP2), proceeded to activate the NF-κB signal pathway and ultimately contributed to HCC progression. In addition, depletion of BIRC3 rescued the pro-tumorigenic effect of circNUP54 on HCC cells. Overall, this study demonstrated that circNUP54 facilitates HCC progression via regulating the HuR/BIRC3/NF-κB axis, which may serve as a promising therapeutic target for HCC treatment.

Circular RNA circWNK1 inhibits the progression of gastric cancer via regulating the miR-21-3p/SMAD7 axis

Gastric cancer (GC) is a highly aggressive malignancy with limited treatment options for advanced-stage patients. Recent studies have highlighted the role of circular RNA (circRNA) as a novel regulator of cancer progression in various malignancies. However, the underlying mechanisms by which circRNA contributes to the development and progression of GC remain poorly understood. In this study, we utilized microarrays and real-time quantitative polymerase chain reaction (qRT-PCR) to identify and validate a downregulated circRNA, hsa_circ_0003251 (referred to as circWNK1), in paired GC and normal tissues. Through a series of in vitro and in vivo gain-of-function and loss-of-function assays, we demonstrated that circWNK1 exerts inhibitory effects on the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of GC cells. Additionally, we discovered that circWNK1 acts as a competitive endogenous RNA (ceRNA) for SMAD7 by sequestering miR-21-3p. Our findings were supported by comprehensive biological information analysis, as well as RNA pull-down, luciferase reporter gene, and western blot assays. Notably, the downregulation of circWNK1 in GC cells resulted in reduced SMAD7 expression, subsequently activating the TGF-β signaling pathway. Collectively, our study reveals that circWNK1 functions as a tumor suppressor in GC by regulating the miR-21-3p/SMAD7-mediated TGF-β signaling pathway. Furthermore, circWNK1 holds promise as a potential biomarker for the diagnosis and treatment of GC.

Emerging roles of circular RNAs in tumorigenesis, progression, and treatment of gastric cancer

With an estimated one million new cases reported annually, gastric cancer (GC) ranks as the fifth most diagnosed malignancy worldwide. The early detection of GC remains a major challenge, and the prognosis worsens either when patients develop resistance to chemotherapy or radiotherapy or when the cancer metastasizes. The precise pathogenesis underlying GC is not well understood, which further complicates its treatment. Circular RNAs (circRNAs), a recently discovered class of noncoding RNAs that originate from parental genes through "back-splicing", have been shown to play a key role in various biological processes in both eukaryotes and prokaryotes. CircRNAs have been linked to cardiovascular diseases, diabetes, hypertension, Alzheimer's disease, and the occurrence and progression of tumors. Prior studies have established that circRNAs play a crucial role in GC, impacting tumorigenesis, diagnosis, progression, and therapy resistance. This review aims to summarize how circRNAs contribute to GC tumorigenesis and progression, examine their roles in the development of drug resistance, discuss their potential as biotechnological drugs, and summarize their response to therapeutic drugs and microorganism in GC.

Bioinformatics analysis identifies coagulation factor II receptor as a potential biomarker in stomach adenocarcinoma

Coagulation factor 2 thrombin receptor (F2R), a member of the G protein-coupled receptor family, plays an important role in regulating blood clotting through protein hydrolytic cleavage mediated receptor activation. However, the underlying biological mechanisms by which F2R affects the development of gastric adenocarcinoma are not fully understood. This study aimed to systematically analyze the role of F2R in gastric adenocarcinoma. Stomach adenocarcinoma (STAD)-related gene microarray data and corresponding clinicopathological information were downloaded from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Differential expression genes (DEGs) associated with F2R were analyzed using Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), gene set enrichment analysis (GSEA), and protein-protein interaction (PPI) networks. F2R mRNA expression data were utilized to estimate stromal cell and immune cell scores in gastric cancer tissue samples, including stromal score, immune score, and ESTIMATE score, derived from single-sample enrichment studies. Analysis of TCGA and GEO databases revealed significantly higher F2R expression in STAD tissues compared to normal tissues. Patients with high F2R expression had shorter survival times than those with low F2R expression. F2R expression was significantly correlated with tumor (T) stage, node (N) stage, histological grade and pathological stage. Enrichment analysis of F2R-related genes showed that GO terms were mainly related to circulation-mediated human immune response, immunoglobulin, cell recognition and phagocytosis. KEGG analysis indicated associations to extracellular matrix (ECM) receptor interactions, neuroactive ligand-receptor interactions, the phosphoinositide-3-kinase-protein kinase B/Akt (PI3K-AKT) signaling pathway, the Wnt signaling pathway and the transforming growth factor-beta (TGF-β) signaling pathway. GSEA revealed connections to DNA replication, the Janus kinase/signal transducers and activators of transcription (JAK-STAT) signaling pathway, the mitogen-activated protein kinase (MAPK) signaling pathway and oxidative phosphorylation. Drug sensitivity analysis demonstrated positive correlations between F2R and several drugs, including BEZ235, CGP-60474, Dasatinib, HG-6-64-1, Aazopanib, Rapamycin, Sunitinib and TGX221, while negative correlation with CP724714, FH535, GSK1904529A, JNK-9L, LY317615, pyrimidine, rTRAIL and Vinorelbine. Knocking down F2R in GC cell lines resulted in slowed proliferation, migration, and invasion. All statistical analyses were performed using R software (version 4.2.1) and GraphPad Prism 9.0. p < 0.05 was considered statistically significant. In conclusion, this study underscores the significance of F2R as a potential biomarker in gastric adenocarcinoma, shedding light on its molecular mechanisms in tumorigenesis. F2R holds promise for aiding in the diagnosis, prognosis, and targeted therapy of STAD.

Circular RNAs: Promising Treatment Targets and Biomarkers of Ischemic Stroke

Ischemic stroke is one of the most significant causes of morbidity and mortality worldwide. However, there is a dearth of effective drugs and treatment methods for ischemic stroke. Significant numbers of circular RNAs (circRNAs) exhibit abnormal expression following ischemic stroke and are considered potential therapeutic targets. CircRNAs have emerged as promising biomarkers due to their stable expression in peripheral blood and their potential significance in ischemic stroke diagnosis and prognosis. This review provides a summary of 31 circRNAs involved in the pathophysiological processes of apoptosis, autophagy, inflammation, oxidative stress, and angiogenesis following ischemic stroke. Furthermore, we discuss the mechanisms of action of said circRNAs and their potential clinical applications. Ultimately, circRNAs exhibit promise as both therapeutic targets and biomarkers for ischemic stroke.

Circular RNA CDR1as Mediated by Human Antigen R (HuR) Promotes Gastric Cancer Growth via miR-299-3p/TGIF1 Axis

Background: Gastric cancer (GC) remains a common malignancy worldwide with a limited understanding of the disease mechanisms. A novel circular RNA CDR1as has been recently reported to be a crucial regulator of human cancer. However, its biological role and mechanism in the GC growth are still far from clear. Methods: Small interfering RNAs (siRNAs), lentivirus or plasmid vectors were applied for gene manipulation. The CDR1as effects on the GC growth were evaluated in CCK8 and colony formation assays, a flow cytometry analysis and mouse xenograft tumor models. A bioinformatics analysis combined with RNA immunoprecipitation (RIP), RNA pull-down assays, dual-luciferase reporter gene assays, Western blot, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and functional rescue experiments were used to identify the CDR1as target miRNA, the downstream target gene and its interaction with human antigen R (HuR). Results: The CDR1as overexpression promoted the GC growth in vitro and in vivo and reduced the apoptotic rate of GC cells. Its knockdown inhibited the GC cell proliferation and viability and increased the cell apoptotic rate. Proliferation-related proteins PCNA and Cyclin D1 and apoptosis-related proteins Bax, Bcl-2, Caspase-3 and Caspase-9 were regulated. Mechanically, the cytoplasmic CDR1as acted as a miR-299-3p sponge to relieve its suppressive effects on the GC cell growth. Oncogenic TGIF1 was a miR-299-3p downstream target gene that mediated the promotive effects of CDR1as and regulated the PCNA and Bax levels. HuR interacted with CDR1as via the RRM2 domain and positively regulated the CDR1as level and its oncogenic role as well as downstream target TGIF1. Conclusions: CDR1as promotes the GC growth through the HuR/CDR1as/miR-299-3p/TGIF1 axis and could be used as a new therapeutic target for GC.

INHBA gene silencing inhibits proliferation, migration, and invasion of osteosarcoma cells by repressing TGF-β signaling pathway activation

BACKGROUND

Osteosarcoma (OS) is a refractory malignancy. This study aimed to explore the roles and mechanisms of Inhibin subunit beta A (INHBA) in OS.

METHODS

INHBA expression levels in OS tissues and cells were assessed using RT-qPCR and western blotting. The impact of INHBA silencing on OS development was then explored by transfecting the OS cell lines U2OS and MG63 with INHBA-small interfering RNA (siRNA). The influence of INHBA silencing on U2OS and MG63 cell proliferation, migration, and invasion was examined using MTT and Transwell assays. Epithelial-mesenchymal transition (EMT) markers (E-cadherin and N-cadherin) were analyzed by RT-qPCR. The expression of genes involved in cell proliferation, migration, invasion, and the TGF-β signaling pathway was evaluated by western blotting and RT-qPCR.

RESULTS

INHBA levels were elevated in the OS tissues and cells. Furthermore, the transforming growth factor-β (TGF-β) signaling pathway of OS cells was suppressed in response to INHBA-siRNA, whereas proliferation, migration, and invasion of OS cells were inhibited. Besides, INHBA-siRNA significantly inhibited OS cell EMT, evidenced by enhanced E-cadherin mRNA expression and reduced N-cadherin mRNA expression. Further mechanistic studies revealed that the TGF-β1 agonist SRI-011381 hydrochloride increased OS cell proliferation, migration, and invasion after INHBA downregulation.

CONCLUSION

We found that INHBA silencing could play a vital role in OS via TGF-β1-regulated proliferation, migration, and invasion.

Non-coding RNAs' function in cancer development, diagnosis and therapy

While previous research on cancer biology has focused on genes that code for proteins, in recent years it has been discovered that non-coding RNAs (ncRNAs)play key regulatory roles in cell biological functions. NcRNAs account for more than 95% of human transcripts and are an important entry point for the study of the mechanism of cancer development. An increasing number of studies have demonstrated that ncRNAs can act as tumor suppressor genes or oncogenes to regulate tumor development at the epigenetic level, transcriptional level, as well as post-transcriptional level. Because of the importance of ncRNAs in cancer, most clinical trials have focused on ncRNAs to explore whether ncRNAs can be used as new biomarkers or therapies. In this review, we focus on recent studies of ncRNAs including microRNAs (miRNAs), long ncRNAs (lncRNAs), circle RNAs (circRNAs), PIWI interacting RNAs (piRNAs), and tRNA in different types of cancer and explore the application of these ncRNAs in the development of cancer and the identification of relevant therapeutic targets and tumor biomarkers. Graphical abstract drawn by Fidraw.

Circular RNA_0000285: A novel double-edged sword circular RNA in human malignancies

Circular RNAs (circRNAs) are a class of RNA molecules that are characterized by their covalently closed structure, which is formed through a process of back splicing of the precursor mRNA. Abnormal expression of circRNAs has been shown to indirectly affect their interaction with microRNAs (miRNAs), thereby modulating gene transcription. One such circRNA, circ_0000285, is known to be dysregulated in various cancers and human diseases. This circRNA is derived from the HIPK3 gene on chromosome 11 and acts as a competing endogenous RNA for several miRNAs, including miR-654-3p, miR-197-3p, miR-1278, miR-582-3p, and miR-599. Notably, circ_0000285 has been linked to poor overall survival and several clinicopathological features in multiple human cancers. In this review, we present a comprehensive summary of the oncogenic effect of circ_0000285 in various cancers, drawing on experiment performed on cell lines, animals, and human tissues. Furthermore, we predicted potential miRNAs and RNA-binding proteins that may interact with circ_0000285, thereby providing new insights for further studies.

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.

The Role of the Transforming Growth Factor-β Signaling Pathway in Gastrointestinal Cancers

Transforming growth factor-β (TGF-β) has attracted attention as a tumor suppressor because of its potent growth-suppressive effect on epithelial cells. Dysregulation of the TGF-β signaling pathway is considered to be one of the key factors in carcinogenesis, and genetic alterations affecting TGF-β signaling are extraordinarily common in cancers of the gastrointestinal system, such as hereditary nonpolyposis colon cancer and pancreatic cancer. Accumulating evidence suggests that TGF-β is produced from various types of cells in the tumor microenvironment and mediates extracellular matrix deposition, tumor angiogenesis, the formation of CAFs, and suppression of the anti-tumor immune reaction. It is also being considered as a factor that promotes the malignant transformation of cancer, particularly the invasion and metastasis of cancer cells, including epithelial-mesenchymal transition. Therefore, elucidating the role of TGF-β signaling in carcinogenesis, cancer invasion, and metastasis will provide novel basic insight for diagnosis and prognosis and the development of new molecularly targeted therapies for gastrointestinal cancers. In this review, we outline an overview of the complex mechanisms and functions of TGF-β signaling. Furthermore, we discuss the therapeutic potentials of targeting the TGF-β signaling pathway for gastrointestinal cancer treatment and discuss the remaining challenges and future perspectives on targeting this pathway.

Gastric cancer-derived LBP promotes liver metastasis by driving intrahepatic fibrotic pre-metastatic niche formation

BACKGROUND

Liver metastasis (LM) is one of the most common distant metastases of gastric cancer (GC). However, the mechanisms underlying the LM of GC (GC-LM) remain poorly understood. This study aimed to identify the tumour-secreted protein associated with GC-LM and to investigate the mechanisms by which this secreted protein remodels the liver microenvironment to promote GC-LM.

METHODS

Data-independent acquisition mass spectrometry (DIA-MS), mRNA expression microarray, quantitative real-time PCR, enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (IHC) were performed to identify and validate the GC-secreted proteins associated with GC-LM. A modified intrasplenic injection mouse model of LM was used to evaluate the progression and tumour burden of LM in vivo. Flow cytometry, immunofluorescence (IF), western blots (WB) and IHC were performed to validate the pre-metastatic niche (PMN) formation in the pre-modelling mouse models. mRNA sequencing of PMA-treated THP-1 cells with or without lipopolysaccharide binding protein (LBP) treatment was used to identify the functional target genes of LBP in macrophages. Co-immunoprecipitation (Co-IP), WB, ELISA, IF and Transwell assays were performed to explore the underlying mechanism of LBP in inducing intrahepatic PMN formation.

RESULTS

LBP was identified as a critical secreted protein associated with GC-LM and correlated with a worse prognosis in patients with GC. LBP activated the TLR4/NF-κB pathway to promote TGF-β1 secretion in intrahepatic macrophages, which, in turn, activated hepatic satellite cells (HSCs) to direct intrahepatic fibrotic PMN formation. Additionally, TGF-β1 enhanced the migration and invasion of incoming metastatic GC cells in the liver. Consequently, selective targeting of the TGF-β/Smad signaling pathway with galunisertib demonstrated its efficacy in effectively preventing GC-LM in vivo.

CONCLUSIONS

The results of this study provide compelling evidence that serological LBP can serve as a valuable diagnostic biomarker for the early detection of GC-LM. Mechanistically, GC-derived LBP mediates the crosstalk between primary GC cells and the intrahepatic microenvironment by promoting TGF-β1 secretion in intrahepatic macrophages, which induces intrahepatic fibrotic PMN formation to promote GC-LM. Importantly, selectively targeting the TGF-β/Smad signaling pathway with galunisertib represents a promising preventive and therapeutic strategy for GC-LM.

Integrated analysis of high‑throughput sequencing reveals the regulatory potential of hsa_circ_0035431 in HNSCC

Circular RNAs (circRNAs) are molecular sponges that are involved in regulation of multiple types of cancer. The present study aimed to screen and explore the key circRNA/microRNA (miRNA or miR)/mRNA interactions in head and neck squamous cell carcinoma (HNSCC) using bioinformatics. A total of six pairs of cancerous and adjacent healthy tissue were obtained from patients with HNSCC and genome-wide transcriptional sequencing was performed. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses were performed on differentially expressed genes (DEGs). Moreover, expression levels of DEGs were verified in HNSCC cells and tissues using reverse transcription-quantitative (RT-q)PCR. A molecular regulatory network consisting of three circRNAs, seven miRNAs and seven mRNAs was constructed, resulting in identification of two signaling axes, hsa_circ_0035431/hsa-miR-940/fucosyltransferase 6 (FUT6) and hsa_circ_0035431/hsa-miR-940/cingulin-like 1 (CGNL1). FUT6 and CGNL1 were downregulated in HNSCC compared with adjacent healthy tissue and the expression levels of these genes were associated with tumor stage. Low FUT6 and CGNL1 expression levels were associated with lower overall survival rate and progression-free intervals in HNSCC. RT-qPCR demonstrated that hsa_circ_0035431, FUT6 and CGNL1 were downregulated in HNSCC cells and tissue and hsa-miR-940 was upregulated. Notably, these results were consistent with those obtained using high-throughput sequencing. In conclusion, hsa_circ_0035431 may participate in regulation of FUT6 and CGNL1 expression by sponging hsa-miR-940, thus, impacting the occurrence, development and prognosis of HNSCC.

CircRNA_15430 reduced by Helicobacter pylori infection and suppressed gastric cancer progression via miR-382-5p/ZCCHC14 axis

BACKGROUND

Helicobacter pylori (H.pylori, HP) is one of the main causes of gastric cancer (GC). CircRNAs have been reported to play a crucial role in developing many types of cancer. However, the role of circRNAs in the development and progression of HP infected-GC has not been studied.

METHODS

The location of circRNA_15430 in GC cells were detected by nuclear and cytoplasmic RNA fractionation and RNA fluorescence in situ hybridization analysis (FISH) assays, and circRNA_15430, miR-382-5p and ZCCHC14 expression in GC cell lines and tissues were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). The function of circRNA_15430 in GC cells were examined by using colony formation, cell counting kit-8 (CCK-8) and Transwell assays, flow cytometry and laser scanning confocal microscopy. The protein levels were detected by Western blotting. Whether circRNA_15430 sponges miR-382-5p was monitored with a dual-luciferase reporter assay. Furthermore, circRNA_15430 was analyzed in vivo in tumor growth with nude mice.

RESULTS

CircRNA_15430 is primarily localized in the cytoplasm of GC cells, and downregulated in the GC cell lines and tissues, and is negatively correlated with the tumor size. Downregulation of circRNA_15430 promotes proliferation, migration and suppresses cell apoptosis and autophagy in GC cells. Mechanically, circRNA_15430 acts as a miR-382-5p sponge, alleviating the inhibitory effect of miR-382-5p on its target ZCCHC14. Knockdown circRNA_15430 enhances tumor growth in vivo. In addition, circRNA_15430 was reduced in HP + gastritis tissues and HP-infected MGC-803 cells, reversing the pro-HP effect on autophagy. Additionally, miR-382-5p was increased in HP + gastritis tissue and HP-infected MGC-803 cells while ZCCHC14 decreased in HP-infected MGC-803 cells. MiR-382-5p reverses the effect of si-ZCCHC14 on autophagosome numbers in MGC-803 cells.

CONCLUSIONS

Therefore, circRNA_15430 plays an inhibitory role in GC and regulates the progression of HP infection-related GC, providing a novel molecular marker for GC therapy.

Exosomal hsa_circ_000200 as a potential biomarker and metastasis enhancer of gastric cancer via miR-4659a/b-3p/HBEGF axis

BACKGROUND

Exosome, a component of liquid biopsy, loaded protein, DNA, RNA and lipid gradually emerges as biomarker in tumors. However, exosomal circRNAs as biomarker and function mechanism in gastric cancer (GC) are not well understood.

METHODS

Differentially expressed circRNAs in GC and healthy people were screened by database. The identification of hsa_circ_000200 was verified by RNase R and sequencing, and the expression of hsa_circ_000200 was evaluated using qRT-PCR. The biological function of hsa_circ_000200 in GC was verified in vitro. Western blot, RIP, RNA fluorescence in situ hybridization, and double luciferase assay were utilized to explore the potential mechanism of hsa_circ_000200.

RESULTS

Hsa_circ_000200 up-regulated in GC tissue, serum and serum exosomes. Hsa_circ_000200 in serum exosomes showed better diagnostic ability than that of tissues and serum. Combined with clinicopathological parameters, its level was related to invasion depth, TNM staging, and distal metastasis. Functionally, knockdown of hsa_circ_000200 inhibited GC cells proliferation, migration and invasion in vitro, while its overexpression played the opposite role. Importantly, exosomes with up-regulated hsa_circ_000200 promoted the proliferation and migration of co-cultured GC cells. Mechanistically, hsa_circ_000200 acted as a "ceRNA" for miR-4659a/b-3p to increase HBEGF and TGF-β/Smad expression, then promoted the development of GC.

CONCLUSIONS

Our findings suggest that hsa_circ_000200 promotes the progression of GC through hsa_circ_000200/miR-4659a/b-3p/HBEGF axis and affecting the expression of TGF-β/Smad. Serum exosomal hsa_circ_000200 may serve as a potential biomarker for GC.

RNA binding protein: coordinated expression between the nuclear and mitochondrial genomes in tumors

Mitochondria are the only organelles regulated by two genomes. The coordinated translation of nuclear DNA (nDNA) and mitochondrial DNA (mtDNA), which together co-encode the subunits of the oxidative phosphorylation (OXPHOS) complex, is critical for determining the metabolic plasticity of tumor cells. RNA-binding protein (RBP) is a post-transcriptional regulatory factor that plays a pivotal role in determining the fate of mRNA. RBP rapidly and effectively reshapes the mitochondrial proteome in response to intracellular and extracellular stressors, mediating the cytoplasmic and mitochondrial translation balance to adjust mitochondrial respiratory capacity and provide energy for tumor cells to adapt to different environmental pressures and growth needs. This review highlights the ability of RBPs to use liquid-liquid phase separation (LLPS) as a platform for translation regulation, integrating nuclear-mitochondrial positive and retrograde signals to coordinate cross-department translation, reshape mitochondrial energy metabolism, and promote the development and survival of tumor cells.

CircRNAs regulate the crosstalk between inflammation and tumorigenesis: The bilateral association and molecular mechanisms

Inflammation, a hallmark of cancer, has been associated with tumor progression, transition into malignant phenotype and efficacy of the chemotherapeutic agents in cancer. Chronic inflammation provides a favorable environment for tumorigenesis by inducing immunosuppression, whereas acute inflammation prompts tumor suppression by generating anti-tumor immune responses. Inflammatory factors derived from interstitial cells or tumor cells can stimulate cell proliferation and survival by modulating oncogenes and/or tumor suppressors. Recently, a new class of RNAs, i.e., circular RNAs (circRNAs), has been implicated in inflammatory diseases. Although there are reports on circRNAs imparting functions in inflammatory insults, whether these circularized transcripts hold the potential to regulate inflammation-induced cancer or tumor-related inflammation, and modulate the interactions between tumor microenvironment (TME) and the inflammatory stromal/immune cells, awaits further elucidation. Contextually, the current review describes the molecular association between inflammation and cancer, and spotlights the regulatory mechanisms by which circRNAs can moderate TME in response to inflammatory signals/triggers. We also present comprehensive information about the immune cell(s)-specific expression and functions of the circRNAs in TME, modulation of inflammatory signaling pathways to drive tumorigenesis, and their plausible roles in inflammasomes and tumor development. Moreover, the therapeutic potential of these circRNAs in harnessing inflammatory responses in cancer is also discussed.

Cigarette Smoke-Induced Gastric Cancer Cell Exosomes Affected the Fate of Surrounding Normal Cells via the Circ0000670/Wnt/β-Catenin Axis

Cigarette smoke is a major risk factor for gastric cancer. Exosomes are an important part of intercellular and intra-organ communication systems and can carry circRNA and other components to play a regulatory role in the occurrence and development of gastric cancer. However, it is unclear whether cigarette smoke can affect exosomes and exosomal circRNA to promote the development of gastric cancer. Exosomes secreted by cancer cells promote cancer development by affecting surrounding normal cells. Herein, we aimed to clarify whether the exosomes secreted by cigarette smoke-induced gastric cancer cells can promote the development of gastric cancer by affecting the surrounding gastric mucosal epithelial cells (GES-1). In the present study, we treated gastric cancer cells with cigarette smoke extract for 4 days and demonstrated that cigarette smoke promotes the stemness and EMT of gastric cancer cells and cigarette smoke-induced exosomes promote stemness gene expression, EMT processes and the proliferation of GES-1 cells. We further found that circ0000670 was up-regulated in tissues of gastric cancer patients with smoking history, cigarette smoke-induced gastric cancer cells and their exosomes. Functional assays showed that circ0000670 knockdown inhibited the promoting effects of cigarette smoke-induced exosomes on the stemness and EMT characteristic of GES-1 cells, whereas its overexpression had the opposite effect. In addition, exosomal circ0000670 was found to promote the development of gastric cancer by regulating the Wnt/β-catenin pathway. Our findings indicated that exosomal circ0000670 promotes cigarette smoke-induced gastric cancer development, which might provide a new basis for the treatment of cigarette smoke-related gastric cancer.

CircRNF10-DHX15 interaction suppressed breast cancer progression by antagonizing DHX15-NF-κB p65 positive feedback loop

BACKGROUND

Breast cancer (BC) is a common threat to women. The continuous activation of nuclear factor kappa B (NF-κB) signaling pathway contributes to the development of BC. This study aimed to investigate the role of a circular RNA (circRNF10) in BC progression and regulating NF-κB signaling pathway.

METHODS

Bioinformatics analysis, RT-qPCR, subcellular fractionation, FISH, RNase R treatment, and actinomycin D assay were used to explore the expression and characteristics of circRNF10 in BC. The biological functions of circRNF10 in BC were analyzed by MTT assay, colony formation assay, wound healing assay, and Transwell assay. RNA pulldown and RIP assay were used to identify the interaction between circRNF10 and DEAH (Asp-Glu-Ala-His) box helicase 15 (DHX15). The impact of circRNF10-DHX15 interaction on NF-κB signaling pathway was explored by western blot, IF, and co-IP. Furthermore, dual-luciferase reporter assay, ChIP, and EMSA were performed to assess the effect of NF-κB p65 on DHX15 transcription.

RESULTS

CircRNF10 was downregulated in BC, and lower expression of circRNF10 was related to poor prognosis of patients with BC. CircRNF10 inhibited the proliferation and migration of BC. Mechanically, circRNF10-DHX15 interaction sequestered DHX15 from NF-κB p65, thereby inhibiting the activation of NF-κB signaling pathway. On the other hand, NF-κB p65 enhanced DHX15 transcription by binding to the promoter of DHX15. Altogether, circRNF10 impaired the DHX15-NF-κB p65 positive feedback loop and suppressed the progression of BC.

CONCLUSION

CircRNF10-DHX15 interaction suppressed the DHX15-NF-κB p65 positive feedback loop, thereby inhibiting BC progression. These findings provide new insights in the continuous activation of NF-κB signaling pathway and raised potential therapeutic approach for BC treatment.

Exosomal circular RNAs: A chief culprit in cancer chemotherapy resistance

Chemotherapy is one of the primary treatments for malignant tumors. However, the acquired drug resistance hinders clinical efficacy and leads to treatment failure in most patients. Exosomes are cell-derived vesicles with a diameter of 30-150 nm carrying and delivering substances such as DNAs, RNAs, lipids, and proteins for cellular communication in tumor development. Circular RNAs (circRNAs) present covalently closed-loop RNA structures, which regulate tumor cell proliferation, apoptosis, and metastasis by controlling different genes and signaling pathways. CircRNAs are abundant and stably expressed in exosomes. Recent studies have shown that they play critical roles in chemotherapy resistance in various cancers. In this review, we summarized the origin of exosomes and discussed the regulation mechanism of exosomal circRNAs in cancer drug resistance.

Role of circRNAs in gastric cancer

Circular RNAs (circRNAs) are a large class of non-coding RNAs with single-strand covalently closed loops, formed by reverse splicing, which widely exist in many cell lines and diverse species. Some circRNAs have highly evolutionarily conserved sequences, or tissue-specific or cell-specific expression patterns, and many circRNAs are extremely stable. In the past decades, accumulating evidence has indicated that circRNAs participate in the mechanisms associated with the development of many kinds of tumors, exert important biological functions by acting as microRNA or protein ‘sponges’, transcriptional regulatory factors, and protein translation templates, and play key roles in the occurrence and development of gastric cancer. This review comprehensively summarizes the biogenesis, characteristics, and biological functions of circRNAs, and the molecular mechanisms underlying the role of circRNAs in the carcinogenesis and progression of gastric cancer.

Regulatory mechanism of circular RNA involvement in osteoarthritis

Osteoarthritis (OA) causes joint pain, stiffness, and dysfunction in middle-aged and older adults; however, its pathogenesis remains unclear. Circular RNAs (circRNAs) are differentially expressed in patients with OA and participate in a multigene, multitarget regulatory network. CircRNAs are involved in the development of OA through inflammatory responses, including proliferation, apoptosis, autophagy, differentiation, oxidative stress, and mechanical stress. Most circRNAs are used as intracellular miRNA sponges in chondrocytes, endplate chondrocytes, mesenchymal stem cells, synoviocytes, and macrophages to promote the progression of OA. However, a small portion of circRNAs participates in the pathogenesis of OA by intracellular mechanisms, such as protein binding, methylation, or intercellular exosome pathways. In this sense, circRNAs might serve as potential novel biomarkers and therapeutic targets for OA.

circCYP24A1 facilitates esophageal squamous cell carcinoma progression through binding PKM2 to regulate NF-κB-induced CCL5 secretion

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a common gastrointestinal malignant tumor, while the molecular mechanisms have not been fully elucidated. Multiple circular RNAs have been reported to involve in the onset and progression of malignant tumors through various molecular mechanisms. However, the clinical significance and functional mechanism of most circRNAs involved in the progression of ESCC remains obscure.

METHODS

RNA-Seq was used to explore potential circRNAs in participated in 5 pairs of ESCC and their corresponding normal esophageal tissues. The up-regulated circCYP24A1 was selected. Fluorescence in situ hybridization was cunducted to verificated the expression and intracellular localization of circCYP24A1 by using the tissue microarray. The Kaplan-Meier method and Cox proportional hazards model was used to examine the potential prognostic value of circCYP24A1 on overall survival of ESCC patients. The biological function were confirmed by gain- and loss-of-function approaches in vivo. mRNA expression profile microarray was proformed to investigate the downstream signaling pathways involved in circCYP24A1. RNA pull-down assay and mass spectrometry were performed to identify the proteins associated with circCYP24A1. Rescue experiments were carried out to identified hypothetical regulatory role of circCYP24A1 on ESCC progression in vivo and in virto.

RESULTS

In this study, we identified circCYP24A1 in ESCC tissues by RNA sequencing, which is up-regulated in 114 cases of ESCC tissues and acts as a novel prognosis-related factor. Moreover, circCYP24A1 promoted the ability of proliferation, migration, invasion and clone formation in vitro, as well as tumor growth in vivo. Mechanistically, chemokine (C-Cmotif) ligand 5 (CCL5) is functional downstream mediator for circCYP24A1, which is screened by mRNA microarray. Moreover, circCYP24A1 physically interacts with M2 isoform of pyruvate kinase (PKM2). Rescue experiments showed that PKM2 knockdown partly reverses the promotional effects of circCYP24A1. It was revealed that circCYP24A1 increases secretion of CCL5 through the mechanism mainly by interacting with PKM2, an activator of NF-κB pathway, and thereby accelerate malignant progression of ESCC.

CONCLUSIONS

Up-regulated circCYP24A1 could activate NF-κB pathway by binding PKM2, which promotes the secretion of CCL5 and accelerate malignant progression of ESCC. Our fndings recommended a novel function for circCYP24A1 as a potential effective biomarker for judging prognosis and a therapeutic target in ESCC.

Emerging roles of circular RNAs in gastric cancer metastasis and drug resistance

Gastric cancer (GC) is an aggressive malignancy with a high mortality rate and poor prognosis, primarily caused by metastatic lesions. Improved understanding of GC metastasis at the molecular level yields meaningful insights into potential biomarkers and therapeutic targets. Covalently closed circular RNAs (circRNAs) have emerged as crucial regulators in diverse human cancers including GC. Furthermore, accumulating evidence has demonstrated that circRNAs exhibit the dysregulated patterns in GC and have emerged as crucial regulators in GC invasion and metastasis. However, systematic knowledge regarding the involvement of circRNAs in metastatic GC remains obscure. In this review, we outline the functional circRNAs related to GC metastasis and drug resistance and discuss their underlying mechanisms, providing a comprehensive delineation of circRNA functions on metastatic GC and shedding new light on future therapeutic interventions for GC metastases.

BMSCs overexpressed ISL1 reduces the apoptosis of islet cells through ANLN carrying exosome, INHBA, and caffeine

Early apoptosis of grafted islets is one of the main factors affecting the efficacy of islet transplantation. The combined transplantation of islet cells and bone marrow mesenchymal stem cells (BMSCs) can significantly improve the survival rate of grafted islets. Transcription factor insulin gene enhancer binding protein 1 (ISL1) is shown to promote the angiogenesis of grafted islets and the paracrine function of mesenchymal stem cells during the co-transplantation, yet the regulatory mechanism remains unclear. By using ISL1-overexpressing BMSCs and the subtherapeutic doses of islets for co-transplantation, we managed to reduce the apoptosis and improve the survival rate of the grafts. Our metabolomics and proteomics data suggested that ISL1 upregulates aniline (ANLN) and Inhibin beta A chain (INHBA), and stimulated the release of caffeine in the BMSCs. We then demonstrated that the upregulation of ANLN and INHBA was achieved by the binding of ISL1 to the promoter regions of the two genes. In addition, ISL1 could also promote BMSCs to release exosomes with high expression of ANLN, secrete INHBA and caffeine, and reduce streptozocin (STZ)-induced islets apoptosis. Thus, our study provides mechanical insight into the islet/BMSCs co-transplantation and paves the foundation for using conditioned medium to mimic the ISL1-overexpressing BMSCs co-transplantation.

Mechanism underlying circRNA dysregulation in the TME of digestive system cancer

Circular RNAs (circRNAs) are a new series of noncoding RNAs (ncRNAs) that have been reported to be expressed in eukaryotic cells and have a variety of biological functions in the regulation of cancer pathogenesis and progression. The TME, as a microscopic ecological environment, consists of a variety of cells, including tumor cells, immune cells and other normal cells, ECM and a large number of signaling molecules. The crosstalk between circRNAs and the TME plays a complicated role in affecting the malignant behaviors of digestive system cancers. Herein, we summarize the mechanisms underlying aberrant circRNA expression in the TME of the digestive system cancers, including immune surveillance, angiogenesis, EMT, and ECM remodelling. The regulation of the TME by circRNA is expected to be a new therapeutic method.