Hsa_circ_0006948 enhances cancer progression and epithelial-mesenchymal transition through the miR-490-3p/HMGA2 axis in esophageal squamous cell carcinoma

Association of deletion polymorphism rs10573247 in the HMGA2 gene with the risk of breast cancer: bioinformatic and experimental analyses

BACKGROUND

The high mobility group A2 (HMGA2) gene is expressed extensively during early embryonic development but is inactivated in adulthood, and it is also reactivated in various benign and malignant tumors, including breast cancer. We first assessed the potential functional significance of the unstudied deletion polymorphism rs10573247 at the 3'UTR of HMGA2 on miRNA binding using bioinformatic tools, and subsequently, the association between this polymorphism and breast cancer susceptibility was investigated.

MATERIALS AND METHODS

We applied the RNAhybrid tool to predict the functional effects of polymorphism rs10573247 located within the 3' UTR of the HMGA2 gene on miRNA binding. Then, following DNA extraction, 141 breast cancer patients and 123 healthy controls were genotyped for polymorphism rs10573247 using RFLP-PCR with the restriction enzyme Eam1104I.

RESULTS

Our bioinformatic data have shown that polymorphism rs10573247 is located in the region that serves as a potential target site for eight miRNAs binding. Among them, miR-3125 exhibited decreased binding affinity for the allele delTT (MFE = -21.8) when compared to the allele TT (MFE = -23.9), but miR-4476 increased binding affinity for the allele delTT (MFE = -22.4) compared to the allele TT (MFE = -22.2). In addition, our results showed that the genotype TT/delTT (p = 0.005) and the genotype delTT/delTT (p = 0.029) were significantly associated with an increased risk of developing breast cancer compared to the genotype TT/TT using RFLP-PCR.

DISCUSSION AND CONCLUSION

Our findings suggest that polymorphism rs10573247 may contribute to the risk of breast cancer through the functional effect of this polymorphism on miRNA binding.

MicroRNAs: A novel signature in the metastasis of esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a malignant epithelial tumor, characterized by squamous cell differentiation, it is the sixth leading cause of cancer-related deaths globally. The increased mortality rate of ESCC patients is predominantly due to the advanced stage of the disease when discovered, coupled with higher risk of metastasis, which is an exceedingly malignant characteristic of cancer, frequently leading to a high mortality rate. Unfortunately, there is currently no specific and effective marker to predict and treat metastasis in ESCC. MicroRNAs (miRNAs) are a class of small non-coding RNA molecules, approximately 22 nucleotides in length. miRNAs are vital in modulating gene expression and serve pivotal regulatory roles in the occurrence, progression, and prognosis of cancer. Here, we have examined the literature to highlight the intimate correlations between miRNAs and ESCC metastasis, and show that ESCC metastasis is predominantly regulated or regulated by genetic and epigenetic factors. This review proposes a potential role for miRNAs as diagnostic and therapeutic biomarkers for metastasis in ESCC metastasis, with the ultimate aim of reducing the mortality rate among patients with ESCC.

Hsa_circ_0001707 regulates endothelial-mesenchymal transition in esophageal squamous cell carcinoma via miR-203a-3p/Snail2 pathway

Esophageal squamous cell carcinoma (ESCC) is a malignant tumor with high mortality and poor prognosis. Despite intensive research focused on tumor suppression, the 5-year survival rate of ESCC is lower than 15%. Therefore, investigate fundamental mechanisms involved in ESCC is on-demand crucial for diagnostics and developing targeted therapeutic drugs. Circular RNAs (circRNAs), as an emerging class of non-coding RNA, have been elucidated that circRNAs participated in regulating a variety of pathological processes and tumorigenesis. Nevertheless, the functional role of circRNAs in the occurrence and development of ESCC remains unclear. We identify a novel circRNA (hsa_circ_0001707), which was highly expressed in ESCC patients' tissues and cell lines. Furthermore, gain- and loss-of-function assays were performed and found that overexpression of hsa_circ_0001707 significantly promote tumor proliferation, metastasis, and invasion. By functioning as a competing endogenous RNA (ceRNA), the dual-luciferase activity assay verified that hsa_circ_0001707 can endogenously bind with miR-203a-3p and regulate its downstream gene Snail2. Rescue assay further confirms that hsa_circ_0001707 downregulation could partially attenuate the facilitation effect of miR-203a-3p, thereby inhibiting the endothelial-mesenchymal transition (EMT) process of ESCC. Our results suggested that hsa_circ_0001707 play an oncogenic role in the pathogenesis of ESCC, which might be a potential biomarker for diagnostics and targeting therapy.

Triptolide inhibits esophageal squamous cell carcinoma progression by regulating the circNOX4/miR-153-3p/SATB1 signaling pathway

BACKGROUND

To explore the role and mechanism of triptolide in regulating esophageal squamous cell carcinoma (ESCC) progression by mediating the circular RNA (circRNA)-related pathway.

METHODS

The expression levels of circNOX4, miR-153-3p and special AT-rich sequence binding protein-1 (SATB1) were measured by qRT-PCR. Cell proliferation was confirmed by cell counting kit-8 assay and colony formation assay. Flow cytometry was employed to measure cell apoptosis and cell cycle process. Moreover, cell migration and invasion were detected using transwell assay. The protein levels of epithelial-mesenchymal transformation markers and SATB1 were determined by western blot analysis. Furthermore, dual-luciferase reporter assay and RIP assay were performed to confirm the interaction between miR-153-3p and circNOX4 or SATB1. Xenograft tumor models were built to verify the effects of triptolide and circNOX4 on ESCC tumor growth.

RESULTS

CircNOX4 was highly expressed in ESCC tissues and cells, and its expression could be reduced by triptolide. Triptolide could inhibit ESCC proliferation, cell cycle process, migration, invasion, EMT process, and promote apoptosis, while these effects were reversed by circNOX4 overexpression. MiR-153-3p could be sponged by circNOX4, and the promotion effect of circNOX4 on the progression of triptolide-treated ESCC cells was abolished by miR-153-3p overexpression. SATB1 was a target of miR-153-3p. Also, SATB1 knockdown reversed the enhancing effect of miR-153-3p inhibitor on the progression of triptolide-treated ESCC cells. Triptolide reduced ESCC tumor growth by regulating the circNOX4/miR-153-3p/SATB1 axis.

CONCLUSION

Triptolide could hinder ESCC progression, which was mainly achieved by regulating the circNOX4/miR-153-3p/SATB1 axis.

Appraising the value of CircRNAs for the diagnosis and prognosis of esophageal squamous cell cancer: An updated meta-analysis

OBJECTIVE

The purpose of this study was to thoroughly assess the relevance of circular RNAs (circRNAs) in the diagnosis and prognosis of esophageal squamous cell carcinoma (ESCC)， and design a systematic review and meta-analysis.

METHODS

Using Stata 14.0 software, a meta-analysis was carried out by looking for pertinent studies up to February 20, 2023, in the online databases PubMed, Embase, Web of Science, and CNKI. The clinicopathologic and prognostic data were evaluated using the combined advantage ratio (OR) and combined hazard ratio (HR), respectively. The threshold effects and publication bias were quantified using Spearman's correlation and the Deeks funnel plot asymmetry tests, respectively.

RESULTS

A total of 36 pertinent studies with a literature quality score of 7 or above were included in this study. Of them, 22 papers dealt with clinicopathological characterization, 15 dealt with prognostic analysis, and 13 dealt with diagnostic analysis. The findings demonstrated that high expression of upregulated circRNAs was associated with worse clinicopathological features (tumor size: OR=3.61, 95% CI:1.45-5.78; TNM stage: OR=2.12, 95% CI:1.41-2.83; lymph node metastasis: OR=2.87, 95% CI:1.67-4.07) and worse OS (HR=1.49, 95% CI:1.26-1.77). High downregulated circRNAs expression was linked to improved clinicopathologic characteristics (TNM staging: OR=0.35, 95% CI:0.13- 0.95) and longer survival (HR=0.48, 95% CI:0.27-0.84); combined sensitivity was 0.77 (95% CI: 0.71-0.82), specificity was 0.80 (95% CI:0.74-0.86), and area under the subject operating characteristic curve (AUC) was 0.86 (95% CI:0.82- 0.88).

CONCLUSION

CircRNAs are useful for ESCC patient diagnosis and prognosis, and they are anticipated to be unique potential biomarkers for ESCC clinical diagnosis.

HMGA2 promotes cancer metastasis by regulating epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is a complex physiological process that transforms polarized epithelial cells into moving mesenchymal cells. Dysfunction of EMT promotes the invasion and metastasis of cancer. The architectural transcription factor high mobility group AT-hook 2 (HMGA2) is highly overexpressed in various types of cancer (e.g., colorectal cancer, liver cancer, breast cancer, uterine leiomyomas) and significantly correlated with poor survival rates. Evidence indicated that HMGA2 overexpression markedly decreased the expression of epithelial marker E-cadherin (CDH1) and increased that of vimentin (VIM), Snail, N-cadherin (CDH2), and zinc finger E-box binding homeobox 1 (ZEB1) by targeting the transforming growth factor beta/SMAD (TGFβ/SMAD), mitogen-activated protein kinase (MAPK), and WNT/beta-catenin (WNT/β-catenin) signaling pathways. Furthermore, a new class of non-coding RNAs (miRNAs, circular RNAs, and long non-coding RNAs) plays an essential role in the process of HMGA2-induced metastasis and invasion of cancer by accelerating the EMT process. In this review, we discuss alterations in the expression of HMGA2 in various types of cancer. Furthermore, we highlight the role of HMGA2-induced EMT in promoting tumor growth, migration, and invasion. More importantly, we discuss extensively the mechanism through which HMGA2 regulates the EMT process and invasion in most cancers, including signaling pathways and the interacting RNA signaling axis. Thus, the elucidation of molecular mechanisms that underlie the effects of HMGA2 on cancer invasion and patient survival by mediating EMT may offer new therapeutic methods for preventing cancer progression.

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

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

Circ_FNDC3B Promotes Cell Proliferation and Metastasis in Esophageal Squamous Cell Carcinoma via Regulating MAPK1 by Binding to miR-136-5p

A handful of circular RNAs (circRNAs) associated with cancer progression have been indicated in esophageal squamous cell carcinoma (ESCC). The current study aimed to investigate the functional mechanism of circular RNA Fibronectin type III domain containing 3B (circ_FNDC3B) in ESCC. Circ_FNDC3B, FNDC3B, microRNA-136-5p (miR-136-5p) and mitogen-activated protein kinase 1 (MAPK1) were examined via the quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation was evaluated by Cell Counting Kit-8 (CCK-8) and colony formation assays. Transwell assay was performed to measure cell migration and invasion. Protein analysis was implemented by western blot. Cell apoptosis was assessed via flow cytometry. Target interaction was affirmed using dual-luciferase reporter assay. The function analysis of circ_FNDC3B in vivo was explored by xenograft models. The upregulation of circ_FNDC3B was detected in ESCC tissues and cells. Functionally, ESCC cell proliferation and metastasis were repressed but apoptosis was promoted by circ_FNDC3B knockdown. Besides, circ_FNDC3B silence inhibited ESCC progression through MAPK1 downregulation. Further target analysis identified miR-136-5p as a target of circ_FNDC3B and an upstream control of MAPK1. Additionally, the regulation of si-circ_FNDC3B in ESCC was also dependent on targeting miR-136-5p. Moreover, circ_FNDC3B targeted miR-136-5p to affect MAPK1 level. Tumorigenesis in vivo was also suppressed by downregulating circ_FNDC3B to regulate miR-136-5p/MAPK1 axis. Circ_FNDC3B downregulation impeded the development of ESCC via the mediation of miR-136-5p/MAPK1 axis. This report afforded a novel insight into the functional mechanism of circ_FNDC3B in ESCC.

Targeting epigenetic deregulations for the management of esophageal carcinoma: recent advances and emerging approaches

Ranking from seventh in incidence to sixth in mortality, esophageal carcinoma is considered a severe malignancy of food pipe. Later-stage diagnosis, drug resistance, and a high mortality rate contribute to its lethality. Esophageal squamous cell carcinoma and esophageal adenocarcinoma are the two main histological subtypes of esophageal carcinoma, with squamous cell carcinoma alone accounting for more than eighty percent of its cases. While genetic anomalies are well known in esophageal cancer, accountability of epigenetic deregulations is also being explored for the recent two decades. DNA methylation, histone modifications, and functional non-coding RNAs are the crucial epigenetic players involved in the modulation of different malignancies, including esophageal carcinoma. Targeting these epigenetic aberrations will provide new insights into the development of biomarker tools for risk stratification, early diagnosis, and effective therapeutic intervention. This review discusses different epigenetic alterations, emphasizing the most significant developments in esophageal cancer epigenetics and their potential implication for the detection, prognosis, and treatment of esophageal carcinoma. Further, the preclinical and clinical status of various epigenetic drugs has also been reviewed.

circSSPO boosts growth of esophageal squamous cell carcinoma through upregulation of micrRNA-6820-5p-mediated KLK8 and PKD1 expression

Investigation on a competitive endogenous RNA (ceRNA) network attracted lots of attention due its function in cancer regulation. Here, we probed into the possible molecular mechanism of circSSPO/microRNA-6820-5p (miR-6820-5p)/kallikrein-related peptidase 8 (KLK8)/PKD1 network in the esophageal squamous cell carcinoma (ESCC). Following whole-transcriptome sequencing and differential analysis in collected ESCC tissue samples, circRNA-miRNA-mRNA regulatory network affecting ESCC was investigated. After interaction measurement among circSSPO/miR-6820-5p/KLK8/PKD1, their regulatory roles in ESCC cell functions in vitro and xenograft tumor growth and lung metastasis in vivo were analyzed. The bioinformatics prediction and sequencing results screened that circSSPO, miR-6820-5p, KLK8, and PKD1 were associated with ESCC development. In ESCC, miR-6820-5p was expressed at very low levels, while circSSPO, KLK8, and PKD1 were highly expressed. In vitro cell experiments further proved that circSSPO competitively inhibited miR-6820-5p to induce ESCC cell malignant properties. Moreover, knockdown of KLK8 or PKD1 inhibited ESCC cell malignant properties. circSSPO also promoted the tumorigenic and metastasis of ESCC through the upregulation of KLK8 and PKD1 expression in vivo. We found that circSSPO was an oncogenic circRNA that was significantly abundant in ESCC tissues and circSSPO exhibited an oncogenic activity in ESCC by elevating expression of KLK8 and PKD1 through suppressing miR-6820-5p expression.

Circ_0058063 regulates cell vitality and proliferation in oesophageal squamous-cell carcinomas

Oesophageal squamous-cell carcinoma (ESCC) is a malignant tumor of the digestive system with a poor prognosis. Recent studies have shown the promoting effect of hsa_circ_0058063 (circ_0058063) on ESCC, but the potential regulatory mechanisms of circ_0058063 in ESCC remain largely unclear. The levels of circ_0058063, microRNA-4319 (miR-4319) and mRNA of thrombospondin-1 (THBS1) were indicated by quantitative real-time polymerase chain reaction in ESCC tissues and cells. Meanwhile, the level of THBS1 was quantified by western blot analysis. In addition, the cell functions were examined by CCK8 assay, Edu assay, flow cytometry assay and transwell assay. Furthermore, the interplay between miR-4319 and circ_0058063 or THBS1 was detected by dual-luciferase reporter assay. Finally, an in vivo experiment was implemented to confirm the effect of circ_0058063. The level of circ_0058063 and THBS1 were increased, and the miR-4319 level was decreased in ESCC tissues in contrast to that in normal tissues and cells. For functional analysis, circ_0058063 deficiency inhibited cell vitality, cell proliferation, migration and invasion in ESCC cells, whereas promoted cell apoptosis. Moreover, miR-4319 was confirmed to repress the progression of ESCC cells by suppressing THBS1. In mechanism, circ_0058063 acted as a miR-4319 sponge to regulate the level of THBS1. Besides, circ_0058063 knockdown also attenuated tumour growth in vivo. Circ_0058063 facilitates the development of ESCC through increasing THBS1 expression by regulating miR-4319, which also offered an underlying targeted therapy for ESCC treatment.

MiR-671-5p sponging activity of circMMP1 promotes esophageal squamous cancer progression

BACKGROUND

The aim of this study was to explore the function and mechanism of circular RNA (circRNA) matrix metallopeptidase 1 (circMMP1) in the progression of esophageal squamous cell carcinoma (ESCC).

METHODS

CircMMP1 expression was detected by quantitative real-time PCR (qRT-PCR), and its relationship with the prognosis of ESCC patients was evaluated by Kaplan-Meier analysis. Cells were transfected using corresponding plasmids, and the cell proliferation activity, migration and invasion capabilities in vitro were assessed. The protein level in tissues and cells was analyzed using western blotting. RNA pulldown, dual-luciferase reporter assay and RNA immunoprecipitation assay were performed in ESCC cells to detect the interaction between circMMP1 and miR-671-5p, or the correlation between miR-671-5p and ANO1. Xenograft tumor experiment was carried out to uncover the function of circMMP1 in vivo.

RESULTS

The high level of circMMP1 in tumor tissues was associated with poor prognoses of ESCC patients. Knockdown of circMMP1 suppressed ESCC cell proliferation, migration and invasion in vitro. MiR-671-5p was the target of circMMP1 and mediated the inhibition effect of circMMP1 on ESCC cells. CircMMP1 targeted miR-671-5p to regulate ANO1 expression, which was downstream of miR-671-5p. Overexpression of ANO1 weakened tumor-repressive function of circMMP1 knockdown in ESCC cells. Moreover, silencing of circMMP1 impeded ESCC tumor growth in vivo.

CONCLUSION

Our study provided novel evidence that circMMP1 accelerated ESCC progression by acting as a miR-671-5p sponge to enhance ANO1 expression.

The possible molecular mechanism underlying the involvement of the variable shear factor QKI in the epithelial-mesenchymal transformation of oesophageal cancer

OBJECTIVE

Based on the GEO, TCGA and GTEx databases, we reveal the possible molecular mechanism of the variable shear factor QKI in epithelial mesenchymal transformation (EMT) of oesophageal cancer.

METHODS

Based on the TCGA and GTEx databases, the differential expression of the variable shear factor QKI in oesophageal cancer samples was analysed, and functional enrichment analysis of QKI was performed based on the TCGA-ESCA dataset. The percent-spliced in (PSI) data of oesophageal cancer samples were downloaded from the TCGASpliceSeq database, and the genes and variable splicing types that were significantly related to the expression of the variable splicing factor QKI were screened out. We further identified the significantly upregulated circRNAs and their corresponding coding genes in oesophageal cancer, screened the EMT-related genes that were significantly positively correlated with QKI expression, predicted the circRNA-miRNA binding relationship through the circBank database, predicted the miRNA-mRNA binding relationship through the TargetScan database, and finally obtained the circRNA-miRNA-mRNA network through which QKI promoted the EMT process.

RESULTS

Compared with normal control tissue, QKI expression was significantly upregulated in tumour tissue samples of oesophageal cancer patients. High expression of QKI may promote the EMT process in oesophageal cancer. QKI promotes hsa_circ_0006646 and hsa_circ_0061395 generation by regulating the variable shear of BACH1 and PTK2. In oesophageal cancer, QKI may promote the production of the above two circRNAs by regulating variable splicing, and these circRNAs further competitively bind miRNAs to relieve the targeted inhibition of IL-11, MFAP2, MMP10, and MMP1 and finally promote the EMT process.

CONCLUSION

Variable shear factor QKI promotes hsa_circ_0006646 and hsa_circ_0061395 generation, and downstream related miRNAs can relieve the targeted inhibition of EMT-related genes (IL11, MFAP2, MMP10, MMP1) and promote the occurrence and development of oesophageal cancer, providing a new theoretical basis for screening prognostic markers of oesophageal cancer patients.

Roles of circRNA dysregulation in esophageal squamous cell carcinoma tumor microenvironment

Esophageal squamous cell carcinoma (ESCC) is the most prevalent histological esophageal cancer characterized by advanced diagnosis, metastasis, resistance to treatment, and frequent recurrence. In recent years, numerous human disorders such as ESCC, have been linked to abnormal expression of circular RNAs (circRNAs), suggesting that they are fundamental to the intricate system of gene regulation that governs ESCC formation. The tumor microenvironment (TME), referring to the area surrounding the tumor cells, is composed of multiple components, including stromal cells, immune cells, the vascular system, extracellular matrix (ECM), and numerous signaling molecules. In this review, we briefly described the biological purposes and mechanisms of aberrant circRNA expression in the TME of ESCC, including the immune microenvironment, angiogenesis, epithelial-to-mesenchymal transition, hypoxia, metabolism, and radiotherapy resistance. As in-depth research into the processes of circRNAs in the TME of ESCC continues, circRNAs are promising therapeutic targets or delivery systems for cancer therapy and diagnostic and prognostic indicators for ESCC.

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

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

Circular RNAs as the pivotal regulators of epithelial-mesenchymal transition in gastrointestinal tumor cells

Gastrointestinal (GI) cancers, as the most common human malignancies are always considered one of the most important health challenges in the world. Late diagnosis in advanced tumor stages is one of the main reasons for the high mortality rate and treatment failure in these patients. Therefore, investigating the molecular pathways involved in GI tumor progression is required to introduce the efficient markers for the early tumor diagnosis. Epithelial-mesenchymal transition (EMT) is one of the main cellular mechanisms involved in the GI tumor metastasis. Non-coding RNAs (ncRNAs) are one of the main regulatory factors in EMT process. Circular RNAs (circRNAs) are a group of covalently closed loop ncRNAs that have higher stability in body fluids compared with other ncRNAs. Considering the importance of circRNAs in regulation of EMT process, in the present review we discussed the role of circRNAs in EMT process during GI tumor invasion. It has been reported that circRNAs mainly affect the EMT process through the regulation of EMT-specific transcription factors and signaling pathways such as WNT, PI3K/AKT, TGF-β, and MAPK. This review can be an effective step in introducing a circRNA/EMT based diagnostic panel marker for the early tumor detection among GI cancer patients.

HMGA2 regulation by miRNAs in cancer: affecting cancer hallmarks and therapy response

High mobility group A 2 (HMGA2) is a protein that modulates the structure of chromatin in the nucleus. Importantly, aberrant expression of HMGA2 occurs during carcinogenesis, and this protein is an upstream mediator of cancer hallmarks including evasion of apoptosis, proliferation, invasion, metastasis, and therapy resistance. HMGA2 targets critical signaling pathways such as Wnt/β-catenin and mTOR in cancer cells. Therefore, suppression of HMGA2 function notably decreases cancer progression and improves outcome in patients. As HMGA2 is mainly oncogenic, targeting expression by non-coding RNAs (ncRNAs) is crucial to take into consideration since it affects HMGA2 function. MicroRNAs (miRNAs) belong to ncRNAs and are master regulators of vital cell processes, which affect all aspects of cancer hallmarks. Long ncRNAs (lncRNAs) and circular RNAs (circRNAs), other members of ncRNAs, are upstream mediators of miRNAs. The current review intends to discuss the importance of the miRNA/HMGA2 axis in modulation of various types of cancer, and mentions lncRNAs and circRNAs, which regulate this axis as upstream mediators. Finally, we discuss the effect of miRNAs and HMGA2 interactions on the response of cancer cells to therapy. Regarding the critical role of HMGA2 in regulation of critical signaling pathways in cancer cells, and considering the confirmed interaction between HMGA2 and one of the master regulators of cancer, miRNAs, targeting miRNA/HMGA2 axis in cancer therapy is promising and this could be the subject of future clinical trial experiments.

Exosomal circ_0026611 contributes to lymphangiogenesis by reducing PROX1 acetylation and ubiquitination in human lymphatic endothelial cells (HLECs)

BACKGROUND

Esophageal squamous carcinoma (ESCC) is a common malignancy that originates in the digestive tract. Lymph node metastasis (LNM) is a complicated process, and tumor lymphangiogenesis has been reported to be associated with the spread of tumor cells to lymph nodes (LNs), including in ESCC. However, little is currently known about the mechanisms involved in lymphangiogenesis in ESCC tumors. According to previous literature, we know that hsa_circ_0026611 expresses at a high level in serum exosomes of patients with ESCC and shows a close association with LNM and poor prognosis. However, details on the functions of circ_0026611 in ESCC remain unclear. We aim to explore the effects of circ_0026611 in ESCC cell-derived exosomes on lymphangiogenesis and its potential molecular mechanism.

METHODS

We firstly examined how circ_0026611 may express in ESCC cells and exosomes by quantitative reverse transcription real-time polymerase chain reaction (RT-qPCR). The potential effects circ_0026611 may exert on lymphangiogenesis in ESCC cell-derived exosomes were assessed afterward via mechanism experiments.

RESULTS

circ_0026611 high expression pattern was confirmed in ESCC cells and exosomes. ESCC cell-derived exosomes promoted lymphangiogenesis by transferring circ_0026611. Besides, circ_0026611 interacted with N-α-acetyltransferase 10 (NAA10) to inhibit NAA10-mediated prospero homeobox 1 (PROX1) acetylation with subsequent ubiquitination and degradation. Furthermore, circ_0026611 was verified to promote lymphangiogenesis in a PROX1-mediated manner.

CONCLUSIONS

Exosomal circ_0026611 inhibited PROX1 acetylation and ubiquitination to promote lymphangiogenesis in ESCC.

Circular RNA circ-AGFG1 contributes to esophageal squamous cell carcinoma progression and glutamine catabolism by targeting microRNA-497-5p/solute carrier family 1 member 5 axis

Circular RNAs (circRNAs) have been shown to play important regulatory roles in human malignancies. However, the role of circRNA ArfGAP with FG repeats 1 (circ-AGFG1) in esophageal squamous cell carcinoma (ESCC) progression and its associated mechanism are still largely undefined. Cell proliferation was analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and 5-ethynyl-2'-deoxyuridine assay. Cell apoptosis was assessed by flow cytometry analysis. Transwell assay and wound healing assay were used to analyze cell invasion and migration abilities. The uptake of glutamine and the production of α-ketoglutarate and glutamate were analyzed using Glutamine Determination Kit, α-ketoglutarate Assay Kit and Glutamate Determination Kit. A xenograft tumor model was used to analyze the biological role of circ-AGFG1 in vivo . The interaction between microRNA-497-5p (miR-497-5p) and circ-AGFG1 or solute carrier family 1 member 5 (SLC1A5) was verified by dual-luciferase reporter assay. Circ-AGFG1 expression was upregulated in ESCC tissues and cell lines. Circ-AGFG1 silencing suppressed the proliferation, migration, invasion and glutaminolysis and triggered the apoptosis of ESCC cells. Circ-AGFG1 knockdown significantly slowed down tumor growth in vivo . Circ-AGFG1 acted as a sponge for miR-497-5p, and miR-497-5p interacted with the 3' untranslated region (3'UTR) of SLC1A5. miR-497-5p silencing largely abolished circ-AGFG1 silencing-induced effects in ESCC cells. miR-497-5p overexpression-mediated influences in ESCC cells were largely reversed by the addition of SLC1A5 expressing plasmid. Circ-AGFG1 could upregulate SLC1A5 expression by sponging miR-497-5p. In summary, circ-AGFG1 acted as an oncogene to elevate the malignant potential and promote the glutamine catabolism of ESCC cells by targeting the miR-497-5p/SLC1A5 axis.

circRNA: A New Biomarker and Therapeutic Target for Esophageal Cancer

Circular RNAs (circRNAs) comprise a large class of endogenous non-coding RNA with covalently closed loops and have independent functions as linear transcripts transcribed from identical genes. circRNAs are generated by a “back-splicing” process regulated by regulatory elements in cis and associating proteins in trans. Many studies have shown that circRNAs play important roles in multiple processes, including splicing, transcription, chromatin modification, miRNA sponges, and protein decoys. circRNAs are highly stable because of their closed ring structure, which prevents them from degradation by exonucleases, and are more abundant in terminally differentiated cells, such as brains. Recently, it was demonstrated that numerous circRNAs are differentially expressed in cancer cells, and their dysfunction is involved in tumorigenesis and metastasis. However, the crucial functions of these circRNAs and the dysregulation of circRNAs in cancer are still unknown. In this review, we summarize the recent reports on the biogenesis and biology of circRNAs and then catalog the advances in using circRNAs as biomarkers and therapeutic targets for cancer therapy, particularly esophageal cancer.

A novel circ_0000654/miR-375/E2F3 ceRNA network in esophageal squamous cell carcinoma

Background

The competing endogenous RNA (ceRNA) activity of circular RNAs (circRNAs) has been implicated in the pathogenesis of cancers, including esophageal squamous cell carcinoma (ESCC). Here, we identified the ceRNA mechanism of circ_0000654 regulation in ESCC.

Methods

The levels of circ_0000654, E2F transcription factor 3 (E2F3), and microRNA (miR)‐375 were gauged by quantitative real‐time PCR (qRT‐PCR) and western blot. Cell proliferation was assessed by 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium (MTS) and 5‐ethynyl‐2′‐deoxyuridine (EdU) assays. Cell apoptosis was detected by flow cytometry. Cell colony formation was tested by colony formation assay. Dual‐luciferase reporter, RNA pull‐down and RNA immunoprecipitation (RIP) assays were performed to confirm the direct relationship between miR‐375 and circ_0000654 or E2F3. Xenograft model assays were used to evaluate the effect of circ_0000654 in vivo.

Results

Circ_0000654 and E2F3 were upregulated in ESCC. Circ_0000654 depletion enhanced cell apoptosis and hindered cell proliferation and glycolysis in vitro, as well as weakened tumor growth in vivo. Increased expression of E2F3 counteracted the effects of circ_0000654 depletion. Mechanistically, E2F3 was a target of miR‐375, and circ_0000654 modulated E2F3 expression through sequestering miR‐375. Furthermore, miR‐375 upregulation phenocopied circ_0000654 knockdown in inhibiting ESCC progression.

Conclusion

Our findings identify a new circ_0000654/miR‐375/E2F3 ceRNA crosstalk for the oncogenic role of circ_0000654 in ESCC and establish a notion that targeting circ_0000654 and its pathways may have the potential to improve ESCC outcome.

Circular RNA circ_0006948 Promotes Esophageal Squamous Cell Carcinoma Progression by Regulating microRNA-3612/LASP1 Axis

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is the most prevalent malignancy worldwide. Circular RNAs (circRNAs) circ_0006948 is reported to be upregulated in ESCC cells.

AIMS

This study is designed to explore the role and mechanism of circ_0006948 in ESCC progression.

METHODS

Circ_0006948, linear FNDC3B, microRNA-3612 (miR-3612), and LIM and SH3 protein 1 (LASP1) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). Cell viability, colony number, migration, invasion, and apoptosis were examined by Cell Counting Kit-8 (CCK-8), colony formation, transwell, and flow cytometry assays, severally. Glucose consumption, lactate production, and ATP level were measured by the corresponding kits. Protein levels of hexokinase 2 (HK2) and lactate dehydrogenase A (LDHA), and LASP1 were assessed by western blot assay. The cytoplasmic localization of circ_0006948 was identified by the subcellular fractionation assay. The binding relationship between miR-3612 and circ_0006948 or LASP1 was predicted by starBase or TargetScan and then verified by a dual-luciferase reporter assay. The biological role of circ_0006948 on ESCC tumor growth was examined by the xenograft tumor model in vivo.

RESULTS

Circ_0006948 and LASP1 were increased, and miR-3612 was decreased in ESCC tissues and cells. Furthermore, circ_0006948 knockdown could suppress cell viability, colony number, migration, invasion, glycolysis, and boost apoptosis in ESCC cells. Mechanically, circ_0006948 could act as a sponge of miR-3612 to regulate LASP1 expression. In addition, circ_0006948 silencing inhibited ESCC tumor growth in vivo.

CONCLUSION

Circ_0006948 boosted ESCC progression partly by regulating the miR-3612/LASP1 axis, providing an underlying therapeutic target for the ESCC treatment.

circRNA TCFL5 Promote Esophageal Cancer Progression by Modulating M2 Macrophage Polarization via the miR-543-FMNL2 Axis

Objective

The mechanism of circRNA on M2 macrophage polarization, which contributes to esophageal cancer, remains unclear. This study is aimed at clarifying the mechanism of circRNA on esophageal cancer by regulating M2 macrophage polarization.

Methods

The expression of circRNA TCFL5 and miR-543 was detected by qRT-PCR. Western blot was used to detect the expression of FMNL2 and CD163. CCK-8 and transwell assay was used to detect the proliferation, migration, and invasion of Eca109 and KYSE150, respectively. Flow cytometry was used to detect the CD163 positive cells. The contents of IL-10, TGF-β, TNF-α, IL-6, and IL-1β were detected by ELISA. A dual-luciferase reporter system was used to detect the regulation of miR-543 to circRNA TCFL5 and FMNL2.

Results

156 upregulated circRNAs and 91 downregulated circRNAs in esophageal cancer tissues were identified, and the expression of circRNA TCFL5 showed the most significant upregulation. Overexpression of circRNA TCFL5 promotes proliferation, invasion, and migration of Eca109 and KYSE150 and promotes tumor growth in vivo. circRNA TCFL5 served as a sponge of miR-543, and FMNL2 was a downstream target gene of miR-543. circRNA TCFL5 promotes cell proliferation, migration, and invasion of Eca109 and KYSE150 by modulating the miR-543/FMNL2 axis. Macrophage M2 polarization promoted proliferation, invasion, and migration of Eca109 and KYSE150 cells, and circRNA TCFL5 mediated macrophage M2 polarization by regulating the FMNL2/miR-543 axis.

Conclusion

In the present study, we identified that circRNA TCFL5 was dramatically upregulated in esophageal cancer, and circRNA TCFL5 promotes esophageal cancer progression by modulating M2 macrophage polarization via the miR-543-FMNL2 axis, which provides a potential target for the treatment of esophageal cancer.

Circ_0001273 downregulation inhibits the growth, migration and glutamine metabolism of esophageal cancer cells via targeting the miR-622/SLC1A5 signaling axis

BACKGROUND

Esophageal cancer is a relatively rare cancer. However, its death rate is not to be taken lightly. Accumulating evidence indicates circular RNA (circRNA) is implicated in cancer development. The objective of this study was to unveil the role of circ_0001273 in esophageal cancer (EC).

METHODS

For expression analysis of circ_0001273, miR-622 and solute carrier family 1 member 5 (SLC1A5), quantitative real-time PCR (qPCR) and Western blot were conducted. Cell proliferation was evaluated by cell counting kit-8 (CCK-8), EdU and colony formation assays. Cell apoptosis and cell migration were investigated using flow cytometry assay and wound healing assay. Glutamine metabolism was assessed by glutamine consumption and glutamate production using matched kits. The predicted binding relationship between miR-622 and circ_0001273 or SLC1A5 was validated by dual-luciferase reporter assay. An in vivo xenograft model was established to determine the role of circ_0001273 on tumor growth.

RESULTS

Circ_0001273 was upregulated in EC tumor tissues and cells. Knockdown of circ_0001273 repressed EC cell proliferation, migration, epithelial-mesenchymal transition (EMT) and glutamine metabolism. Circ_0001273 knockdown also blocked tumor development in animal models. MiR-622 was targeted by circ_0001273, and its inhibition reversed the functional effects of circ_0001273 knockdown. SLC1A5 was a target gene of miR-622, and circ_0001273 targeted miR-622 to positively regulate SLC1A5 expression. The inhibitory effects of miR-622 enrichment on EC cell proliferation, migration, EMT and glutamine metabolism were recovered by SLC1A5 overexpression.

CONCLUSION

Circ_0001273 high expression contributed to EC progression via modulating the miR-622/SLC1A5 signaling axis.

Hsa_circ_0023984 Regulates Cell Proliferation, Migration, and Invasion in Esophageal Squamous Cancer via Regulating miR-1294/PI3K/Akt/c-Myc Pathway

Circular RNAs (circRNAs) exert an essential function in the tumorigenesis and progression of esophageal squamous cancer (ESCC). Nonetheless, the role and potential mechanism of circ_0023984 in ESCC are blurred. circRNA expression profile data from Gene Expression Omnibus (GEO) database was applied to analyze circRNAs that were differentially expressed between ESCC tissues and paracancerous tissues. Quantitative real-time polymerase chain reaction (qRT-PCR) was conducted to analyze circ_0023984 expression and miR-1294 expression in ESCC tissues and cells. Then a series of functional experiments were executed to validate the role of circ_0023984 and miR-1294 in modulating the proliferation, migration, invasion, and cell cycle progression of ESCC cells. Luciferase reporter experiment was performed to confirm the targeting relationship between circ_0023984 and miR-1294. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were carried out with DAVID database. Western blot assay was utilized to detect phosphorylated-Akt (p-Akt) expression and c-Myc expression. circ_0023984 was remarkably upmodulated in ESCC tumor tissues and cell lines. circ_0023984 overexpression was correlated with advanced clinical stage and lymph node metastasis of ESCC patients. circ_0023984 overexpression remarkably enhanced ESCC cell proliferation, migration, invasion, and cell cycle progression, while knockdown of circ_0023984 showed the opposite effect. circ_0023984 was the molecular sponge of miR-1294. miR-1294 could significantly inhibit ESCC cell proliferation, migration, invasion, and induce cell cycle arrest at G0/G1 phase. circ_0023984 affected ESCC progression through regulating miR-1294 expression. The target genes of miR-1294 were associated with cell cycle arrest and PI3K-Akt signaling pathway. circ_0023984 upregulated the expression of p-Akt and c-Myc by repressing miR-1294. circ_0023984 facilitates the malignant biological behaviors of ESCC cells through inhibiting miR-1294 and activating PI3K/Akt/c-myc pathway.

Exosomal circRNA FNDC3B promotes the progression of esophageal squamous cell carcinoma by sponging miR-490-5p and regulating thioredoxin reductase 1 expression

Exosomal circular RNAs (circRNAs) have been reported to play critical roles in esophageal squamous cell carcinoma (ESCC). We aimed to investigate the function of exosomal circRNA FNDC3B (circFNDC3B). The RNA levels and protein levels were examined using RT-qPCR and western blot (WB) assays. Colony formation and EdU assays were used to assess cell proliferative ability. Cell migratory and invasive abilities were detected by wound healing and transwell assays. Cell apoptosis was measured by flow cytometry. Glycolysis was measured using commercial kits. Transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA) were applied to examine the morphology and size of exosomes. Dual-luciferase reporter, RIP and RNA pull-down assays assessed the interaction of miR-490-5p with circFNDC3B or thioredoxin reductase 1 (TXNRD1). Xenograft tumor model determined the role of exosomal circFNDC3B in vivo. We observed that circFNDC3B was upregulated in ESCC samples and cells, as well as ESCC-derived exosomes. CircFNDC3B could be delivered via exosomes in tumor cells, and the colony formation, proliferation, migration, invasion, glycolysis, and in vivo growth ability of recipient cells were weakened after co-incubation with exosomal circFNDC3B-knockdown donor cells. CircFNDC3B was a miR-490-5p sponge, and miR-490-5p inhibition reversed the role of exosomal circFNDC3B-downregulating in ESCC cells. TXNRD1 was a miR-490-5p target, and TXNRD1 elevation weakened the anti-cancer function of miR-490-5p upregulation in ESCC cells. CircFNDC3B mediated TXNRD1 expression by interacting with miR-490-5p. In conclusion, exosomal circFNDC3B drove ESCC progression via regulating the miR-490-5p/TXNRD1 axis.AbbreviationsEC: esophageal cancer; ESCC: esophageal squamous cell carcinoma; circRNA: circular RNA; WB: western blot; TEM: transmission electron microscopy; NTA: nanoparticle tracking analysis; TXNRD1: thioredoxin reductase 1; IHC: immunohistochemistry; RT-qPCR: reverse transcription-polymerase quantitative chain reaction; GLUT1: glucose transport protein type 1; LDHA: lactate dehydrogenase A.

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

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

Exosomal circDNER enhances paclitaxel resistance and tumorigenicity of lung cancer via targeting miR-139-5p/ITGB8

BACKGROUND

Circular RNAs (circRNAs) are regarded as vital regulatory factors in various cancers. However, the biological functions of circDNER in the paclitaxel (PTX) resistance of lung cancer remain largely unexplored.

METHODS

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to analyze circDNER, miR-139-5p, and ITGB8. Cell proliferation was assessed via colony formation and MTT assays. Cell apoptosis was evaluated by flow cytometry. Western blot was performed to assess protein expression. The targeted interaction among circDNER, miR-139-5p, and ITGB8 were validated using dual-luciferase reporter or RNA immunoprecipitation assays.

RESULTS

Inhibition of circDNER reduced IC50 of PTX, inhibited cell proliferation, invasion and migration, as well as promoted cell apoptosis in PTX-resistant lung cancer cells. Mechanistically, circDNER sponged miR-139-5p to upregulate ITGB8 expression. Overexpression of miR-139-5p reversed the biological functions mediated by circDNER in PTX-resistant lung cancer cells. MiR-139-5p overexpression suppressed PTX resistance and malignant behaviors of PTX-resistant lung cancer cells, with ITGB8 elevation rescued the impacts. Moreover, we demonstrated that circDNER was upregulated in plasma exosomes from lung cancer patients. The plasma exosomes derived from these patients are the key factors enhancing the migration and invasion potential of lung cancer cells.

CONCLUSION

The circDNER mediated miR-139-5p/ITGB8 axis suppresses lung cancer progression. Our findings suggest that circDNER might act as a potential prognostic biomarker and therapeutic target for lung cancer treatment.

LncRNA HCG11 Facilitates Nasopharyngeal Carcinoma Progression Through Regulating miRNA-490-3p/MAP3K9 Axis

Purpose

Long noncoding RNAs (LncRNAs) play complex but important roles in the progression of various tumors. This study aimed to elucidate the functional mechanisms of the HLA complex group 11 (HCG11) in nasopharyngeal carcinoma (NPC).

Patients and Methods

HCG11 levels in NPC specimens were determined by fluorescence in situ hybridization (FISH) and qPCR. Proliferation, apoptosis, and metastasis of NPC cells were determined using CCK8, colony formation, annexin V-PI, and transwell assays. A murine tumor xenograft model was used to investigate the regulatory function of HCG11 in NPC in vivo, and immunohistochemical staining was used to determine the Ki-67 level in tumors. The target relationships between HCG11, microRNA miR-490-3p, and MAPK kinase kinase 9 (MAP3K9) were detected using bioinformatics, qPCR, western blotting, and luciferase reporter assays.

Results

HCG11 was highly expressed in NPC tissues and was positively associated with tumor stage, lymphatic metastasis, and poor prognosis. Functionally, HCG11 knockdown inhibited proliferation and migration and induced apoptosis of NPC cells. Mechanistically, miR-490-3p is a direct target of HCG11, oncogenic functions of HCG11 in NPC cell proliferation and migration can be partially reversed by the miR-490-3p inhibitor. HCG11 significantly increased mitogen-activated protein kinase MAPK kinase 9 (MAP3K9) levels by inhibiting miR-490-3p.

Conclusion

HCG11 facilitates NPC progression via MAP3K9 signaling by sponging miRNA-490-3p, which may contribute to new prognostic markers and promising therapeutic targets.

CircRNA circ_0023984 promotes the progression of esophageal squamous cell carcinoma via regulating miR-134-5p/cystatin-s axis

Recent studies have shown that circRNAs can act as oncogenic factors or tumor suppressors by sponging microRNAs (miRNAs). The upregulation of circ_0023984 was reported in esophageal squamous cell carcinoma (ESCC). However, its functional role in ESCC remain unclear. In the present study, circ_0023984 expression in ESCC cells and tissues were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting (WB). Subcellular fraction experiment was performed to determine relative nuclear-cytoplasmic localization. The loss-of-function effects of circ_0023984 in ESCC cell lines were investigated by shRNA-mediated knockdown. Functional assays including cell Counting Kit-8 (CCK-8), 5-Ethynyl-2’-deoxyuridine (EDU) incorporation, colony formation and Transwell migration assays were conducted to assess the malignant phenotype. The interaction between the two molecules was analyzed by RNA pull-down, luciferase reporter assay and RNA immunoprecipitation (RIP). The subcutaneous tumor model in nude mice was used to assess the role of circ-0023984 in tumorigenesis. We found that ESCC patients with high circ_0023984 expression was associated with a poor prognosis. The knockdown of circ_0023984 suppressed cell growth, invasion, and migration in ESCC cells. Circ_0023984 interacted with miR-134-5p and inhibited its activity, which promoted the expression of CST4 (Cystatin-S). Circ_0023984 also regulated tumorigenesis in a CST4-dependent manner. Together, our study indicates that the oncogenic role of Circ_0023984 is mediated by miR-134-5p/CST4 Axis in ESCC, which could serve as potential targets for future therapeutic strategies.

Circular RNA hsa_circ_0000277 promotes tumor progression and DDP resistance in esophageal squamous cell carcinoma

Background

Circular RNAs (circRNAs) are well-known regulators of cancer progression and chemoresistance in various types of cancers. This study was performed to investigate the function of hsa_circ_0000277 in esophageal squamous cell carcinoma (ESCC).

Methods

RNA levels were analyzed via the reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Cell Counting Kit-8 (CCK-8) assay was applied to determine cell proliferation and half maximal inhibitory concentration (IC50) of cisplatin (DDP). Colony formation ability was evaluated by colony formation assay. Cell cycle and apoptosis were measured using flow cytometry. RNA immunoprecipitation (RIP), pull-down assay and dual-luciferase reporter assays were performed for target interaction analysis. The protein levels were determined through western blot. Xenograft models were established for researching hsa_circ_0000277 function in vivo.

Results

Hsa_circ_0000277 expression was increased in ESCC cells and tissues, and it had important clinical significance. Downregulation of hsa_circ_0000277 repressed ESCC cell proliferation, colony formation, cell cycle, and DDP resistance. Hsa_circ_0000277 acted as a microRNA-873-5p (miR-873-5p) sponge and Sry-related high-mobility group box 4 (SOX4) was validated as a target of miR-873-5p. Moreover, hsa_circ_0000277/miR-873-5p axis and miR-873-5p/SOX4 axis regulated ESCC cell progression and DDP resistance. Hsa_circ_0000277/miR-873-5p axis activated SOX4/Wnt/β-catenin signaling pathway. Hsa_circ_0000277 facilitated tumorigenesis and DDP resistance by miR-873-5p/SOX4 axis in vivo.

Conclusion

These findings unraveled that hsa_circ_0000277 promoted ESCC progression and DDP resistance via miR-873-5p/SOX4/Wnt/β-catenin axis, showing a specific molecular mechanism of carcinogenesis and chemoresistance in ESCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09241-9.

CircRNA circ_0000554 promotes ovarian cancer invasion and proliferation by regulating miR-567

Circular RNAs (circRNAs) indicated potential modulating effects in tumor development. However, the specific role of circ_0000554 in ovarian tumor remains unknown. We found that circ_0000554 was overexpressed in ovarian tumor specimens and cells. Forced expression of circ_0000554 promoted cell growth, invasion, and epithelial to mesenchymal transition (EMT). We illustrated that miR-567 was downregulated in ovarian tumor specimens and cells. circ_0000554 was negatively correlated with miR-567 in ovarian tumor specimens. circ_0000554 sponged miR-567 expression in ovarian tumor. RIP assay showed that elevated expression of miR-567 could be enriched with circ_0000554. Luciferase reporter assay indicated that luciferase intensity was inhibited after treated with miR-567 mimic; however, the luciferase value of mut type was not decreased. Elevated expression of circ_0000554 suppressed miR-567 expression in HO8910 cell. circ_0000554 promoted ovarian tumor cell growth, invasion, and EMT via sponging miR-567. It suggested that circ_0000554 represent a potential therapy target for ovarian tumor.

Circ_0023984 Facilitates Esophageal Squamous Cell Carcinoma Progression by Regulating miR-433-3p/REV3L Axis

BACKGROUND

It has been revealed that circular RNAs (circRNAs) play an important role in regulating the malignant phenotype of tumor cells, thus involving in the progression of malignancies. However, the role of circ_0023984 in esophageal squamous cell carcinoma (ESCC) remains largely unclear.

METHODS

The quantitative real-time polymerase chain reaction and Western blot assays were used to detect the expression of circ_0023984, microRNA (miR)-443-3p, and protein reversionless 3-like (REV3L). In vitro and in vivo assays were performed using cell counting kit-8, colony formation, transwell, wound healing, flow cytometry, and xenograft assays. The interaction miR-433-3p and circ_0023984 or REV3L was confirmed by dual-luciferase reporter, pull-down or RIP assays.

RESULTS

Circ_0023984 was highly expressed in ESCC tissues and cells, knockdown of circ_0023984 suppressed cancer cell proliferation, migration, invasion, and promoted cell apoptosis in vitro. Mechanistic analysis confirmed that circ_0023984 functioned as a sponge for miR-433-3p to positively regulate the expression of REV3L that was verified to be a target of miR-433-3p. Circ_0023984 knockdown repressed the tumorigenesis of ESCC cells via targeting miR-433-3p. Additionally, miR-433-3p performed anti-proliferative, anti-migratory, and anti-invasive abilities in ESCC cells, which were reversed by REV3L overexpression. Pre-clinically, silencing of circ_0023984 suppresses the tumorigenesis and growth of xenografts in nude mice.

CONCLUSION

Circ_0023984 exerted an oncogenic role in ESCC tumorigenesis and aggressiveness through promoting cell growth, migration, and invasion via miR-433-3p/REV3L axis.

Circ_0006948 Contributes to Cell Growth, Migration, Invasion and Epithelial-Mesenchymal Transition in Esophageal Carcinoma

BACKGROUND

Circular RNAs (circRNAs) can act as promoters or inhibitors in cancer progression. Has_circ_0006948 (circ_0006948) was reported to aggravate the malignant behaviors of esophageal carcinoma (EC).

AIMS

This study focused on investigating the molecular mechanism of circ_0006948 in EC progression.

METHODS

The quantitative real-time polymerase chain reaction was performed to detect the expression of circ_0006948, microRNA-4262 (miR-4262) and fibronectin type III domain containing 3B (FNDC3B). Cell growth analysis was conducted by Cell Counting Kit-8 and colony formation assays. Cell migration and invasion were assessed by transwell assay. Epithelial-mesenchymal transition (EMT)-associated proteins and FNDC3B protein expression were assayed using western blot. Dual-luciferase reporter and RNA pull-down assays were performed to validate the target combination. Xenograft tumor assay was used for investigating the role of circ_0006948 in vivo.

RESULTS

Circ_0006948 was upregulated in EC tissues and cells. Downregulating the expression of circ_0006948 or FNDC3B repressed cell growth, migration, invasion and EMT in EC cells. Target analysis indicated that miR-4262 was a target for circ_0006948 and FNDC3B was a downstream gene for miR-4262. Moreover, circ_0006948 could affect the expression of FNDC3B via sponging miR-4262. The effects of si-circ_0006948#1 on EC cells were partly restored by miR-4262 inhibition or FNDC3B overexpression. In addition, circ_0006948 also facilitated EC tumorigenesis in vivo by targeting the miR-4262/FNDC3B axis.

CONCLUSION

Taken together, circ_0006948 functioned as an oncogenic factor in EC by the miR-4262-mediated FNDC3B expression regulation.

Role of circular RNAs in gastrointestinal tumors and drug resistance

The incidence of gastrointestinal cancers has increased significantly over the past decade and gastrointestinal malignancies now rank among the leading causes of mortality globally. Although newer therapeutic strategies such as targeted therapies have greatly improved patient outcomes, their clinical success is limited by drug resistance, treatment failure and recurrence of metastatic disease. Therefore, there is an urgent need for further research identifying accurate and reliable biomarkers for precise treatment strategies. Circular RNAs (circRNAs) exhibit a covalently closed structure, high stability and biological conservation, and their expression is associated with the occurrence and development of gastrointestinal tumors. Moreover, circRNAs may significantly influence drug resistance of gastrointestinal cancers. In this article, we review the role of circRNAs in the occurrence and development of gastrointestinal cancer, their association with drug resistance, and potential application for early diagnosis, treatment and prognosis in gastrointestinal malignancies. Furthermore, we summarize characteristics of circRNA, including mechanism of formation and biological effects via mRNA sponging, chromatin replication, gene regulation, translational modification, signal transduction, and damage repair. Finally, we discuss whether circRNA-related noninvasive testing may be clinically provided in the future. This review provides new insights for the future development of diagnostics and therapeutics based on circRNAs in gastrointestinal tumors.

Dysregulated circular RNAs as novel biomarkers in esophageal squamous cell carcinoma: a meta-analysis

Introduction

Circular RNAs (circRNAs) play critical roles in tumorigenesis, but their clinical efficacy in esophageal squamous cell carcinoma (ESCC) still retains controversial. This meta‐analysis aims at evaluating the associations between circRNA expressions and clinicopathologic features as well as the diagnostic and prognostic values of circRNAs in ESCC.

Materials & Methods

PubMed, EMBASE, and other online databases were systematically searched to collect studies on circRNAs and clinicopathological features, diagnostic, and/or prognostic assessments of ESCC. The quality of included studies was evaluated using the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS‐2) and Newcastle‐Ottawa Scale (NOS) scales. The included studies were quantitatively weighted and merged, and diagnostic indicators, hazard ratios (HRs) and the corresponding 95% confidence intervals (CIs) were calculated. P values were merged by Fisher᾽s method. Sources of heterogeneity were traced using subgroup, sensitivity, and meta‐regression analyses.

Results

As a result, 12 studies were included, representing 769 ESCC patients. The meta‐analysis showed that abnormal expressions of circRNAs were associated to TNM stage as well as lymph node and distant metastases in ESCC cases. CircRNA was used to distinguish ESCC patients from healthy controls, and the merged sensitivity, specificity, and the area under the curve (AUC) of ESCC were 0.78 (95% CI: 0.74–0.81), 0.79 (95% CI: 0.75–0.83), and 0.86, respectively. The survival analysis showed that upregulated oncogenic circRNA levels in ESCC tissues was associated with the shorter overall survival (OS) of the patients (univariate analysis: HR = 2.25, 95% CI: 1.71–2.95, p = 0.000, I² = 0.0%; multivariate analysis: HR = 2.50, 95% CI: 1.61–3.89, p = 0.000, I² = 0.0%), while the OS of ESCC patients presenting overexpressions of tumor‐suppressive circRNAs was significantly ameliorated (HR = 0.29, 95% CI: 0.20–0.42, p = 0.000, I² = 0.0%). The subgroup analyses based on circRNA biofunctions, sample size, and reference gene also revealed robust results.

Conclusion

CircRNAs can be used as promising molecular biomarkers for the early diagnosis and prognosis monitoring of ESCC.

LINC00958 promotes bladder cancer carcinogenesis by targeting miR-490-3p and AURKA

Background

Bladder cancer is a prevalent malignancy of the urinary system, in which long non-coding RNAs (lncRNAs) are highly associated. We aimed to elucidate the role of LINC00958 in bladder cancer.

Methods

LINC00958 expression levels were measured using qRT-PCR. The interaction of LINC00958-miR-490-3p-AURKA was analyzed by luciferase, RIP, and RNA pull-down assays. The biological roles of LINC00958, miR-490-3p, and AURKA in bladder cancer cells were analyzed using CCK8, BrdU, and transwell assays.

Results

Increased expression of LINC00958 and AURKA was observed in bladder cancer tissues and cell lines. Decreased LINC00958 expression repressed bladder cancer progression and downregulation of miR-490-3p accelerated bladder cancer cell progression. Moreover, LINC00958 sponges miR-490-3p to upregulate AURKA expression, thereby promoting carcinogenesis in bladder cancer cells.

Conclusions

Our study revealed that LINC00958 facilitated cell proliferation and invasion, and suppressed cell apoptosis by sponging miR-490-3p and upregulating AURKA, thus inspiring a new treatment method for bladder cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-021-08882-6.

Hsa_circ_0026628 promotes the development of colorectal cancer by targeting SP1 to activate the Wnt/β-catenin pathway

Circular RNAs (circRNAs) have been reported to play crucial roles in the progression of various cancers, including colorectal cancer (CRC). SP1 (Sp1 transcription factor) is a well-recognized oncogene in CRC and is deemed to trigger the Wnt/β-catenin pathway. The present study was designed to investigate the role of circRNAs which shared the same pre-mRNA with SP1 in CRC cells. We identified that hsa_circ_0026628 (circ_0026628), a circular RNA that originated from SP1 pre-mRNA, was upregulated in CRC cells. Sanger sequencing and agarose gel electrophoresis verified the circular characteristic of circ_0026628. Functional assays including CCK-8, colony formation, transwell, immunofluorescence staining, and sphere formation assay revealed the function of circ_0026628. RNA pull-down and mass spectrometry disclosed the proteins interacting with circ_0026628. Mechanistic assays including RIP, RNA pull-down, CoIP, ChIP, and luciferase reporter assays demonstrated the interplays between molecules. The results depicted that circ_0026628 functioned as a contributor to CRC cell proliferation, migration, EMT, and stemness. Mechanistically, circ_0026628 served as the endogenous sponge of miR-346 and FUS to elevate SP1 expression at the post-transcriptional level, thus strengthening the interaction between SP1 and β-catenin to activate the Wnt/β-catenin pathway. In turn, the downstream gene of Wnt/β-catenin signaling, SOX2 (SRY-box transcription factor 2), transcriptionally activated SP1 and therefore boosted circ_0026628 level. On the whole, SOX2-induced circ_0026628 sponged miR-346 and recruited FUS protein to augment SP1, triggering the downstream Wnt/β-catenin pathway to facilitate CRC progression.

MicroRNA-490-3p and -490-5p in carcinogenesis: Separate or the same goal?

MicroRNA (miR)-490-3p and miR-490-5p, located on chromosome 7q33, are two independent mature products of miR-490 exerting distinct effects on tumor progression. miR-490-3p and miR-490-5p possess antitumor properties. miR-490-3p dysfunction has been associated with malignancies including colorectal cancer, while the abnormal function of miR-490-5p has been more considerably associated with bladder cancer (for example). At present, there are 30 and 11 target genes of miR-490-3p and miR-490-5p, respectively, that have been experimentally verified, of which the cyclin D1 (CCND1) gene is a common target. Through these target genes, miR-490-3p and miR-490-5p are involved in 7 and 3 signaling pathways, respectively, of which only 2 are shared regulatory signaling pathways. The present review introduces two competing endogenous RNA (ceRNA) regulatory networks centered on miR-490-3p and miR-490-5p. These networks may be important promoters of tumor cell proliferation, invasiveness, metastatic potential and apoptosis. Unlike miR-490-5p, miR-490-3p plays a unique role in promoting cancer. However, both are promising molecular markers for early cancer diagnosis and prognosis. In addition, miR-490-3p was also found to be associated with the chemical resistance of cisplatin and paclitaxel. The present review focuses on the abnormal expression of miR-490-3p and miR-490-5p in different tumor types, and their complex ceRNA regulatory networks. The clinical value of miR-490-3p and miR-490-5p in cancer diagnosis, prognosis and treatment is also clarified, and an explanation for the opposing effects of miR-490-3p in tumor research is provided.

Association of HMGA2 Polymorphisms with Glioma Susceptibility in Chinese Children

Background

Glioma is a malignant central nervous system tumor in children, with poor outcomes and prognosis. HMGA2 is a proto-oncogene with increased expression in various malignancies.

Methods

We explored the association of HMGA2 polymorphisms with glioma susceptibility in Chinese children using a case-control study (191 cases, 248 controls). HMGA2 single nucleotide polymorphisms (rs6581658 A>G; rs8756 A>C; rs968697 T>C) were genotyped using PCR-based TaqMan.

Results

Increased glioma susceptibility was associated with rs6581658 A>G; AG (adjusted odds ratio (OR) = 1.71, 95% confidence interval (CI) = 1.13–2.58, P = 0.010) or GG (adjusted OR = 3.12, 95% CI = 1.26–7.74, P = 0.014) genotype carriers had significantly raised glioma risk compared with AA genotype carriers. The rs6581658 AG/GG (adjusted OR = 1.85, 95% CI = 1.25–2.73, P = 0.002) and AA/GG (adjusted OR = 2.58, 95% CI = 1.05–6.33, P = 0.038) genotypes were associated with an increased risk of glioma relative to the AA genotype. Subjects with 2–3 risk genotypes had a significantly elevated risk (adjusted OR = 1.93, 95% CI = 1.31–2.84, P = 0.001) relative to those with 0–1 risk genotype.

Conclusion

HMGA2 rs6581658 A>G is associated with glioma susceptibility in Chinese children.

Silencing of circRNA circ_0001666 Represses EMT in Pancreatic Cancer Through Upregulating miR-1251 and Downregulating SOX4

Background

Pancreatic cancer (PC) is an aggressive malignancy and has a poor prognosis. Although emerging research has revealed that circular RNAs (circRNAs) are crucial modulators that control tumor development and metastasis, their functional involvement in PC has not been well characterized. Here, we examined whether and how circRNA circ_0001666 governs epithelial-mesenchymal transition (EMT) in PC.

Methods

We investigated the effects of circ_0001666 on EMT and PC cell invasion by gain- and loss-of-function assays. We also explored the mechanisms underlying the functions of circ_0001666 in PC cells.

Results

We found that circ_0001666 is highly expressed in PC tissues and PC cell lines. Patients with high circ_0001666 expression had shorter survival times. In vitro and in vivo experiments have demonstrated that upregulation of circ_0001666 facilitates PC cell proliferation, EMT and invasiveness, whereas knockdown of circ_0001666 exhibits opposite functions. Moreover, circ_0001666 is able to bind to miR-1251, thus increasing the expression of SOX4, which is a direct downstream effector of miR-1251. The oncogenic effects of circ_0001666 on EMT and PC cell invasion were rescued by miR-1251 overexpression.

Conclusions

These results suggested that circ_0001666 acts as an oncogenic circRNA to promote EMT and invasion of PC cells through sponging miR-1251, and indicated that circ_0001666 could be explored as a potential therapeutic target for PC.

CircRNA_2646 functions as a ceRNA to promote progression of esophageal squamous cell carcinoma via inhibiting miR-124/PLP2 signaling pathway

MicroRNA-124 (miR-124) has been predicted as a tumor suppressor in esophageal squamous cell carcinoma (ESCC). However, factors contributing to miR-124 reduction remain unclear. Circular RNAs (circRNAs) are a new family of non-coding RNAs with gene regulatory potential via interacting with miRNAs. We predicted three circRNAs, including CircRNA_14359, CircRNA_2646, and CircRNA_129, that could interact with miR-124 by bioinformatics analysis and determined their expressions in ESCC tissues and adjacent normal tissues. We found that CircRNA_2646 was up-regulated in ESCC, negatively correlated with the expression of miR-124 and positively associated with TNM stage and lymph node metastasis of ESCC. Luciferase reporter assay showed that CircRNA_2646 interacted with miR-124 in ESCC Eca109 and TE-1 cells. Moreover, ectopical overexpression of CircRNA_2646 accelerated cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition (EMT), but restoration of miR-124 abrogated these functions and promoted Bcl-2-dependent cell apoptosis. Furthermore, it was found that the oncogene Proteolipid Protein 2 (PLP2) was the target gene of miR-124. In Eca109 and TE-1 cells, restoration of miR-124 decreased the level of PLP2 and inhibited PLP2-induced cell proliferation, migration, invasion, and EMT, but enhanced cell apoptosis. The in vivo study confirmed that CircRNA_2646 promoted ESCC development by repressing miR-124 and activating PLP2. Taken together, we identified that CircRNA_2646 functioned as an inhibitor in miR-124 signaling pathway in ESCC for carcinogenesis and could be a promising target for ESCC therapy.

circ_NRIP1 is oncogenic in malignant development of esophageal squamous cell carcinoma (ESCC) via miR-595/SEMA4D axis and PI3K/AKT pathway

BACKGROUND

The hsa_circ_0004771 derived from NRIP1 (called circ_NRIP1) is a recently identified oncogenic circRNA. Here, we intended to investigate the role and mechanism of circ_NRIP1 in esophageal squamous cell carcinoma (ESCC), a prevalent and aggressive type of esophageal cancer.

METHODS

Expression of circ_NRIP1, miRNA-595-5p (miR-595) and semaphorin 4D (SEMA4D) was detected by RT-qPCR and western blotting. Cell growth was assessed by colony formation assay, MTS assay, flow cytometry, and xenograft experiment; migration and invasion were evaluated by transwell assay and western blotting. Dual-luciferase reporter assay identified the relationship among circ_NRIP1, miR-595 and SEMA4D. Western blotting measured phosphatidylinositol-3-hydroxykinase (PI3K)/AKT pathway-related proteins.

RESULTS

Expression of circ_NRIP1 was upregulated in ESCC tissues and cells. Knockdown of circ_NRIP1 could enhance apoptosis rate and E-cadherin expression, but suppress colony formation, cell viability, migration, invasion, and snail expression in KYSE30 and KYSE450 cells, as well as retarded tumor growth in mice. The suppressive role of circ_NRIP1 knockdown in cell growth, migration and invasion in vitro was abated by blocking miR-595; meanwhile, miR-595 overexpression elicited similar anti-tumor role in KYSE30 and KYSE450 cells, which was abrogated by restoring SEMA4D. Notably, circ_NRIP1 was a sponge for miR-595, and SEMA4D was a target of miR-595. Besides, PI3K/AKT signal was inhibited by circ_NRIP1 knockdown and/or miR-595 overexpression via indirectly or directly regulating SEMA4D.

CONCLUSION

circ_NRIP1 functioned as an oncogene in ESCC, and modulated ESCC cell growth, migration and invasion both in vitro and in vivo via targeting miR-595/SEMA4D axis and inhibiting PI3K/AKT signaling pathway.

The diverse roles of circular RNAs in pancreatic cancer

Pancreatic cancer is one of the malignant tumors with poor prognosis. The molecular mechanisms of pancreatic oncogenesis and malignant progression are not fully elucidated. Several key signaling pathways, such as Notch, Wnt and hedgehog pathways, are important to drive pancreatic carcinogenesis. Recently, noncoding RNAs, especially circular RNAs (circRNAs), have been characterized to participate into pancreatic cancer development. Therefore, in this review article, we describe the association between circRNAs and pancreatic cancer prognosis. Moreover, we discuss how circRNAs are involved in regulation of cellular processes in pancreatic cancer, including proliferation, apoptosis, cell cycle, migration, invasion, EMT, metastasis, angiogenesis, drug resistance and immune escape. Furthermore, we mention that several compounds could regulate the expression of circRNAs, indicating that targeting circRNAs by compounds might be helpful for treating pancreatic cancer patients.

Circ_0006168 Promotes the Migration, Invasion and Proliferation of Esophageal Squamous Cell Carcinoma Cells via miR-516b-5p-Dependent Regulation of XBP1

Background

Circular RNAs (circRNAs) exert important roles in carcinogenesis. Here, we aimed to uncover the working mechanism of circ_0006168 in esophageal squamous cell carcinoma (ESCC) development.

Methods

Western blot assay and real-time quantitative polymerase chain reaction (RT-qPCR) were used to determine protein and RNA expression, respectively. Wound healing assay and transwell migration assay were performed to assess cell migration ability, whereas cell invasion ability was evaluated by transwell invasion assay. 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and colony formation assay were utilized to analyze cell proliferation ability. Xenograft tumor model was utilized to assess the role of X-box binding protein 1 (XBP1) in xenograft tumor growth in vivo. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA pull down assay were used to verify intermolecular interactions.

Results

XBP1 silencing suppressed the migration, invasion and proliferation of ESCC cells in vitro and restrained the xenograft tumor growth in vivo. MicroRNA-516b-5p (miR-516b-5p) interacted with the 3ʹ untranslated region (3ʹUTR) of XBP1 in ESCC cells. MiR-516b-5p overexpression inhibited the proliferation and motility of ESCC cells. MiR-516b-5p was a molecular target of circ_0006168 in ESCC cells. The interference of circ_0006168 restrained the motility and proliferation of ESCC cells. Circ_0006168 acted as miR-516b-5p sponge to up-regulate XBP1 expression in ESCC cells. MiR-516b-5p silencing or the accumulation of XBP1 largely rescued the proliferation ability and motility in circ_0006168-silenced ESCC cells.

Conclusion

In conclusion, circ_0006168 contributed to ESCC development through promoting the proliferation and motility of ESCC cells via mediating miR-516b-5p/XBP1 axis.

CircDUSP16 Contributes to Cell Development in Esophageal Squamous Cell Carcinoma by Regulating miR-497-5p/TKTL1 Axis

BACKGROUND

The vital roles of circular RNAs in human cancers have been demonstrated. In this study, we aimed to investigate the functions of circDUSP16 in esophageal squamous cell carcinoma (ESCC) development.

METHODS

Quantitative real-time polymerase chain reaction was executed for the expression levels of circDUSP16, DUSP16, miR-497-5p, and transketolase-like-1 (TKTL1) messenger RNA. Actinomycin D assay and RNase R digestion assay were used to determine the characteristics of circDUSP16. Cell Counting Kit-8 assay and colony formation assay were applied for cell proliferation. Transwell assay was performed to assess cell migration and invasion. The glycolysis level was evaluated using specific kits. Protein levels were measured by Western blot assay. RNA pull-down assay and dual-luciferase reporter assay were adopted to explore the relationships among circDUSP16, miR-497-5p, and TKTL1. Murine xenograft model was used to determine the role of circDUSP16 in ESCC in vivo.

RESULTS

CircDUSP16 level was elevated in ESCC tissues, cells, and hypoxia-stimulated ESCC cells. Knockdown of circDUSP16 suppressed hypoxia-induced ESCC cell viability, colony formation, migration, invasion, and glycolysis. For mechanism analysis, circDUSP16 could positively regulate TKTL1 expression by sponging miR-497-5p in ESCC cells. Moreover, miR-497-5p inhibition restored the effects of circDUSP16 knockdown on the malignant behaviors of ESCC cells under hypoxia condition. MiR-497-5p overexpression suppressed hypoxia-induced ESCC cell progression by targeting TKTL1. In addition, circDUSP16 knockdown repressed the tumorigenesis of ESCC in vivo.

CONCLUSIONS

CircDUSP16 knockdown suppressed hypoxia-induced ESCC cell growth, invasion, and glycolysis by regulating TKTL1 expression through sponging miR-497-5p.

Circular RNA hsa_circ_0000700 promotes cell proliferation and migration in Esophageal Squamous Cell Carcinoma by sponging miR-1229

Accumulating evidence has demonstrated that circular RNAs (circRNAs) are involved in the pathogenesis of cancer, including that of esophageal squamous cell carcinoma (ESCC). The current study aimed to investigate the role of hsa_circ_0000700 in ESCC. hsa_circ_0000700, miR-1229, and related functional gene expression was measured by RT-qPCR. To characterize the functions of hsa_circ_0000700 and miR-1229, ESCC cells were infected with hsa_circ_0000700-specific siRNA, miR-1229 mimics, and an inhibitor alone or in combination. Cell Counting Kit-8 (CCK8), colony formation, EdU, flow cytometry, and Transwell assays were employed to evaluate cell proliferation, apoptosis, and migration. Luciferase reporter and RNA immunoprecipitation assays were used to confirm the targeting relationship between hsa_circ_0000700 and miR-1229. Finally, a competing endogenous RNAs (ceRNA) network was built for hsa_circ_0000700, and miR-1229 targets were analyzed by bioinformatics. circ_0000700 expression was significantly upregulated in ESCC cell lines. Actinomycin D and RNase R treatment confirmed that circ_0000700 was more stable than its linear CDH9 mRNA form. Moreover, a cytoplasmic and nuclear fractionation assay suggested that circ_0000700 was mainly distributed in the cytoplasm of ECA-109 and TE-1 cells. In vitro, the proliferative and migratory capacities of ECA-109 and TE-1 cells were inhibited by knocking down circ_0000700 expression. Additionally, miR-1229 silencing reversed the circ_0000700-specific siRNA-induced attenuation of malignant phenotypes. Mechanistically, circ_0000700 was identified as a sponge of miR-1229 and could activate PRRG4, REEP5, and PSMB5 indirectly to promote ESCC progression. In summary, our results suggest that hsa_circ_0000700 functions as an oncogenic factor by sponging miR-1229 in ESCC.

Circular RNA circCLK3 promotes the progression of tongue squamous cell carcinoma via miR-455-5p/PARVA axis

A previous study has elucidated that circular RNA circCLK3 acts as an oncogenic gene in cervical cancer. However, the role and regulatory mechanism of circCLK3 in tongue squamous cell carcinoma (TSCC) remain unknown. Quantitative real-time PCR was used to examine targeted gene expression in different groups. Cell viability and proliferation were investigated by MTT and 5-ethynyl-2'-deoxyuridine assays. Cell migration and invasion were detected by Transwell assays, and cell apoptosis was measured by flow cytometry analysis. The interaction among genes was investigated using luciferase reporter assay, RNA pull-down assay, and RNA immunoprecipitation assay. In the present study, our findings revealed the upregulated expression of circCLK3 in TSCC tissues and cell lines. CircCLK3 knockdown suppressed cell proliferation, migration invasion, and induced cell cycle arrest at G0/G1 phase in TSCC. Moreover, circCLK3 acted as a molecular sponge for miR-455-5p. PARVA was the target gene of miR-455-5p. Furthermore, the negative correlation between expression of miR-455-5p and circCLK3 or PARVA in TSCC tissues was discovered. Rescue assays indicated that PARVA overexpression reversed the circCLK3 knockdown-mediated inhibitory effects on the progression of TSCC. In summary, circCLK3 exerts its carcinogenic effects on TSCC progression via absorbing miR-455-5p to upregulate PARVA, which expands our knowledge on the underlying mechanism of TSCC.