CircZKSCAN1 Suppresses Hepatocellular Carcinoma Tumorigenesis by Regulating miR-873-5p/Downregulation of Deleted in Liver Cancer 1

Investigation of Circular RNA Expression Profiles in Ultrasound-guided Incomplete Radiofrequency Ablation Transplanted Tumor Models of Human Liver Cancer

BACKGROUND

Abnormally expressed circular RNAs (circRNAs) are associated with many diseases and have important biological effects on the regulation of gene expression. However, the circRNA expression profile in incomplete radiofrequency ablation (RFA)-treated liver cancer (LC) patients has not been characterized. This study investigated the potential biological effects of differentially expressed (DE) circRNAs in an incomplete RFA-treated transplantation tumor model of human LC.

MATERIAL/METHODS

A circRNA microarray was utilized to analyze changes in the circRNA expression profiles. CircRNA host gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were also conducted using computational biology. Quantitative real-time PCR (qPCR) was also performed on the selected DE-circRNAs to verify the reliability of the microarray. The circRNA/miRNA interactions were predicted by Arraystar software and confirmed by a dual-luciferase assay.

RESULTS

Following RFA incomplete ablation, 76 DE-circRNAs were detected (|fold change |>1.5, P-value < 0.05), 21 of which were upregulated and 55 of which were downregulated. Computational biological analysis revealed that the T-cell receptor signaling pathway was the most significantly enriched pathway of the genes related to altered expression, as indicated by enrichment of LCK, AKT3 and DLG1. PCR results for the upregulated hsa_circRNA_103595 and downregulated hsa_circRNA_001264 indicated that the circRNA microarray sequencing results were reliable. Double luciferase reporter assays confirmed that hsa-miR-185-3p was the target miRNA of hsa_circRNA_103595.

CONCLUSIONS

The current study confirmed the changes in the expression profiles of circRNAs in tumor transplantation models after incomplete ablation, these changes may play a crucial role in the pathophysiological process of residual cancer transplantation tumors. These findings could lead to new directions for investigating the molecular biological mechanisms underlying RFA-treated LC as well as new ideas for treating LC by regulating circRNAs.

Regulation and functions of the DLC family of RhoGAP proteins: Implications for development and cancer

The DLC (Deleted in Liver Cancer) family of RhoGAP (Rho GTPase-activating) proteins has been extensively studied since the identification of the first family member nearly 30 years ago. Rho GTPase signaling is essential for various cellular processes, including cytoskeletal dynamics, cell migration, and proliferation. Members of the DLC family are key regulators of this signaling pathway, with well-established roles in development and carcinogenesis. Here, we provide a comprehensive review of research into DLC regulation and cellular functions over the last three decades. In particular, we summarize control mechanisms of DLC gene expression at both the transcriptional and post-transcriptional level. Additionally, recent advances in understanding the post-translational regulation of DLC proteins that allow for tuning of protein activity and localization are highlighted. This detailed overview will serve as resource for future studies aimed at further elucidating the complex regulatory mechanisms of DLC family proteins and exploring their potential as targets for therapeutic applications.

Invention of circRNA promoting RNA to specifically promote circRNA production

CircRNA, an essential RNA molecule involved in various biological functions and diseases, often exhibits decreased expression in tumor tissues, playing a role as a tumor suppressor, and suggesting therapeutic potential for cancer. However, current methods for promoting circRNA production are limited. This study introduces a novel approach for enhancing circRNA biogenesis, termed circRNA promoting RNA (cpRNA). CpRNA is designed to complement the flanking sequences of reverse complementary matches (RCMs) within pre-mRNA, thereby facilitating circRNA formation through improved exon circularization. Using a split-GFP reporter system, we demonstrated that cpRNA significantly enhance circGFP production. Optimization identified the best conditions for cpRNA to promote circRNA biogenesis, and these cpRNAs were then used to augment the production of endogenous circRNAs. These results indicate that cpRNAs can specifically increase the production of endogenous circRNAs with RCMs, such as circZKSCAN1 and circSMARCA5 in cancer cells, thereby inhibiting cell proliferation and migration by modulating circRNA-related pathways, showcasing the therapeutic potential of cpRNAs. Mechanistic studies have also shown that cpRNA promotes circRNA biogenesis, in part, by antagonizing the unwinding function of DHX9. Overall, these findings suggest that cpRNA represents a promising strategy for circRNA overexpression, offering a potential treatment for diseases marked by low circRNA levels.

Crosstalk between circRNAs and the PI3K/AKT and/or MEK/ERK signaling pathways in digestive tract malignancy progression

Evidence indicates that circular RNAs (circRNAs) may play an important role in regulating gene expression by binding to miRNAs through miRNA response elements. circRNAs are formed by back-splicing and have a covalently closed structure. The biogenesis of circRNAs also appears to be regulated by certain cell-specific and/or gene-specific mechanisms, and thus some circRNAs are tissue specific and tumor-expression specific. Furthermore, the high stability and tissue specificity of circRNAs may be of value for early diagnosis, survival prediction and precision medicine. This review summarizes current knowledge regarding the classification and functions of circRNAs and the role of circRNAs in regulating the PI3K/AKT and/or MEK/ERK signaling pathways in digestive tract malignancy tumors.

Circular RNAs: New layer of complexity evading breast cancer heterogeneity

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

A novel polypeptide encoded by the circular RNA ZKSCAN1 suppresses HCC via degradation of mTOR

BACKGROUND

hsa_circ_0001727 (circZKSCAN1) has been reported to be a tumor-associated circRNA by sponging microRNAs. Intriguingly, we found that circZKSCAN1 encoded a secretory peptide (circZKSaa) in the liver. The present study aims to elucidate the potential role and molecular mechanism of circZKSaa in the regulation of hepatocellular carcinoma (HCC) progression.

METHODS

The circRNA profiling datasets (RNA-seq data GSE143233 and GSE140202) were reanalyzed and circZKSCAN1 was selected for further study. Mass spectrometry, polysome fractionation assay, dual-luciferase reporter, and a series of experiments showed that circZKSCAN1 encodes circZKSaa. Cell proliferation, apoptosis, and tumorigenesis in nude mice were examined to investigate the functions of circZKSaa. Mechanistically, the relationship between the circZKSaa and mTOR in HCC was verified by immunoprecipitation analyses, mass spectrometry, and immunofluorescence staining analyses.

RESULTS

Receiver operating characteristic (ROC) analysis demonstrated that the secretory peptide circZKSaa encoded by circZKSCAN1 might be the potential biomarker for HCC tissues. Through a series of experiments, we found that circZKSaa inhibited HCC progression and sensitize HCC cells to sorafenib. Mechanistically, we found that the sponge function of circZKSCAN1 to microRNA is weak in HCC, while overexpression of circZKSaa promoted the interaction of FBXW7 with the mammalian target of rapamycin (mTOR) to promote the ubiquitination of mTOR, thereby inhibiting the PI3K/AKT/mTOR pathway. Furthermore, we found that the high expression of cicZKSCAN1 in sorafenib-treated HCC cells was regulated by QKI-5.

CONCLUSIONS

These results reveal that a novel circZKSCAN1-encoded peptide acts as a tumor suppressor on PI3K/AKT/mTOR pathway, and sensitizes HCC cells to sorafenib via ubiquitination of mTOR. These findings demonstrated that circZKSaa has the potential to serve as a therapeutic target and biomarker for HCC treatment.

Mesenchymal stem cell-derived exosomes and non-coding RNAs: Regulatory and therapeutic role in liver diseases

Liver disease has become a major health problem worldwide due to its high morbidity and mortality. In recent years, a large body of literature has shown that mesenchymal stem cell-derived exosomes (MSC-Exo) are able to play similar physiological roles as mesenchymal stem cells (MSCs). More importantly, there is no immune rejection caused by transplanted cells and the risk of tumor formation, which has become a new strategy for the treatment of various liver diseases. Moreover, accumulating evidence suggests that non-coding RNAs (ncRNAs) are the main effectors by which they exert hepatoprotective effects. Therefore, by searching the databases of Web of Science, PubMed, ScienceDirect, Google Scholar and CNKI, this review comprehensively reviewed the therapeutic effects of MSC-Exo and ncRNAs in liver diseases, including liver injury, liver fibrosis, and hepatocellular carcinoma. According to the data, the therapeutic effects of MSC-Exo and ncRNAs on liver diseases are closely related to a variety of molecular mechanisms, including inhibition of inflammatory response, alleviation of liver oxidative stress, inhibition of apoptosis of hepatocytes and endothelial cells, promotion of angiogenesis, blocking the cell cycle of hepatocellular carcinoma, and inhibition of activation and proliferation of hepatic stellate cells. These important findings will provide a direction and basis for us to explore the potential of MSC-Exo and ncRNAs in the clinical treatment of liver diseases in the future.

Circ_0091579 exerts an oncogenic role in hepatocellular carcinoma via mediating miR-136-5p/TRIM27

BACKGROUND

Circular RNAs (circRNAs) act as crucial regulators in tumorigenesis. In this study, the working mechanism of circ_0091579 in hepatocellular carcinoma (HCC) progression was investigated.

METHODS

The expression of RNA and protein was measured via RT-qPCR and Western blot assay. Cell proliferation ability was analyzed via CCK8, EdU and colony formation assays. Cell migration and invasion abilities were detected via transwell assays. Flow cytometry was applied to assess cell cycle and apoptosis. The target relation between miR-136-5p and circ_0091579 or tripartite motif containing 27 (TRIM27) was certified using dual-luciferase reporter assay. Xenograft tumor model was utilized to assess the role of circ_0091579 in tumor growth in vivo. The protein level of Ki67 in tumor tissues was analyzed by immunohistochemistry (IHC) assay.

RESULTS

Circ_0091579 expression was elevated in HCC tissues and cell lines. HCC patients with high circ_0091579 expression displayed low survival rate. Circ_0091579 knockdown suppressed the proliferation, migration, invasion, cell cycle progression and epithelial-mesenchymal transition (EMT) and induced apoptosis of HCC cells. Circ_0091579 acted as a molecular sponge for miR-136-5p, and circ_0091579 silencing-mediated effects were largely overturned by the knockdown of miR-136-5p in HCC cells. MiR-136-5p interacted with the 3' untranslated region (3'UTR) of TRIM27, and TRIM27 overexpression largely counteracted miR-136-5p overexpression-induced influences in HCC cells. Circ_0091579 sponged miR-136-5p to up-regulate TRIM27 expression in HCC cells. Circ_0091579 silencing suppressed xenograft tumor growth in vivo.

CONCLUSION

Circ_0091579 exhibited an oncogenic role to enhance the malignant potential of HCC cells through mediating miR-136-5p/TRIM27 axis in vitro and in vivo.

KLF2-induced circZKSCAN1 potentiates the tumorigenic properties of clear cell renal cell carcinoma by targeting the miR-1294/PIM1 axis

Clear cell renal cell carcinoma (ccRCC) is one of the most common and lethal types of urologic cancer. With low survival rates among patients in advanced stages of disease, and increasing rate of morbidity and mortality worldwide, novel therapeutic targets for ccRCC clinical intervention are necessary. In this study, we investigated the functional role of circZKSCAN1 in ccRCC progression. Our results suggested that circZKSCAN1 was abundantly expressed in ccRCC tumor tissues and cells. CircZKSCAN1 knockdown significantly inhibited cell proliferation, migration, invasion, and epithelial-to-mesenchymal transition of renal cell carcinoma (RCC) cells, whereas potentiated Natural Killer (NK) cell-mediated cytotoxicity against RCC cells in vitro and repressed tumor growth in vivo. Furthermore, we identified a novel circZKSCAN1/miR-1294/PIM1 axis was identified in RCC progression, showing that the expression of circZKSCAN1 expression in RCC cells was transcriptionally regulated by Kruppel-like factor 2. The results of our study may provide new insights for ccRCC basic research.Abbreviations: ccRCC: clear cell renal cell carcinoma; ChIP: chromatin immunoprecipitation; circRNA: circular RNA; EDU: 5-ethynyl-2'-deoxyuridine; EMT: epithelial-mesenchymal transition; FBS: fetal bovine serum; FISH: RNA fluorescent in situ hybridization; KLF2: Kruppel-like factor 2; NC: normal control; NK cell: natural killer cell; NOD/SCID: nonobese severe diabetic/severe combined immunodeficiency; PIM1: Pim-1 proto-oncogene, serine/threonine kinase; RCC: renal cell carcinoma; ZKSCAN1: zinc finger with KRAB and SCAN domains 1.

Circular RNA circ_GLIS2 suppresses hepatocellular carcinoma growth and metastasis

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is one of the leading causes of tumour-related death. Here, we investigated the molecular mechanism of HCC by studying the function of circ_GLIS2.

METHODS

Human HCC specimens and cell lines were used. Sanger sequencing, actinomycin D and RNase R treatment were performed to validate circular RNA features of circ_GLIS2. qRT-PCR, western blotting, immunostaining, and IHC were employed to examine levels of circ_GLIS2, GLIS2 mRNA, and EMT-related markers. CCK-8, colony formation, flow cytometry, wound healing assay, and transwell assays were performed to evaluate cancer cell proliferation, apoptosis, migration, and invasion. RIP and RNA pull-down assay were used to validate EIF4A3/GLIS2 mRNA interaction. MSP was performed to measure the methylation status of GLIS2 promoter. Nude mouse xenograft model was used to examine tumour growth and metastasis in vivo.

RESULTS

Circ_GLIS2 and linear GLIS2 mRNA were reduced in human HCC tissues and cells. Their low levels correlated with a poor survival rate of HCC patients. Overexpression of circ_GLIS2 and GLIS2 suppressed HCC cell proliferation, migration, and invasion but promoted cell apoptosis. GLIS2 promoter region was hypermethylated in HCC cells. EIF4A3 was directly bound with GLIS2 mRNA and promoted circ_GLIS2/GLIS2 expression. Moreover, overexpression of circ_GLIS2 restrained HCC tumour growth and metastasis in vivo.

CONCLUSION

Circ_GLIS2 suppresses HCC growth and metastasis by inhibiting cell proliferation, migration, and invasion, but promoting cell apoptosis. These findings provide molecular insights into the mechanism of HCC and indicate that circ_GLIS2 could serve as a diagnosis marker or therapeutic target for HCC.

Circular RNAs Modulate Cancer Hallmark and Molecular Pathways to Support Cancer Progression and Metastasis

Simple Summary

Circular RNAs (circRNA) are a type of RNA molecule of circular shape that are now being extensively studied due to the important roles they play in different biological processes. In addition, they were also shown to be implicated in disease such as cancer. Cancer is a complex process which is often defined by a combination of specific processes called cancer hallmarks. In this review, we summarize the literature on circRNAs in cancer and classify them as being implicated in specific cancer hallmarks.

Abstract

Circular RNAs (circRNAs) are noncoding products of backsplicing of pre-mRNAs which have been established to possess potent biological functions. Dysregulated circRNA expression has been linked to diseases including different types of cancer. Cancer progression is known to result from the dysregulation of several molecular mechanisms responsible for the maintenance of cellular and tissue homeostasis. The dysregulation of these processes is defined as cancer hallmarks, and the molecular pathways implicated in them are regarded as the targets of therapeutic interference. In this review, we summarize the literature on the investigation of circRNAs implicated in cancer hallmark molecular signaling. First, we present general information on the properties of circRNAs, such as their biogenesis and degradation mechanisms, as well as their basic molecular functions. Subsequently, we summarize the roles of circRNAs in the framework of each cancer hallmark and finally discuss the potential as therapeutic targets.

MiR-873-5p: A Potential Molecular Marker for Cancer Diagnosis and Prognosis

miR-873 is a microRNA located on chromosome 9p21.1. miR-873-5p and miR-873-3p are the two main members of the miR-873 family. Most studies focus on miR-873-5p, and there are a few studies on miR-873-3p. The expression level of miR-873-5p was down-regulated in 14 cancers and up-regulated in 4 cancers. miR-873-5p has many targeted genes, which have unique molecular functions such as catalytic activity, transcription regulation, and binding. miR-873-5p affects cancer development through the PIK3/AKT/mTOR, Wnt/β-Catenin, NF-κβ, and MEK/ERK signaling pathways. In addition, the target genes of miR-873-5p are closely related to the proliferation, apoptosis, migration, invasion, cell cycle, cell stemness, and glycolysis of cancer cells. The target genes of miR-873-5p are also related to the efficacy of several anti-cancer drugs. Currently, in cancer, the expression of miR-873-5p is regulated by a variety of epigenetic factors. This review summarizes the role and mechanism of miR-873-5p in human tumors shows the potential value of miR-873-5p as a molecular marker for cancer diagnosis and prognosis.

Predicting circRNA-Disease Associations Based on Deep Matrix Factorization with Multi-source Fusion

Recently, circRNAs with covalently closed loops have been discovered to play important parts in the progression of diseases. Nevertheless, the study of circRNA-disease associations is highly dependent on biological experiments, which are time-consuming and expensive. Hence, a computational approach to predict circRNA-disease associations is urgently needed. In this paper, we presented an approach that is based on deep matrix factorization with multi-source fusion (DMFMSF). In DMFMSF, several useful circRNA and disease similarities were selected and then combined by similarity kernel fusion. Then, linear and non-linear characteristics were mined using singular value decomposition (SVD) and deep matrix factorization to infer potential circRNA-disease associations. Performance of the proposed DMFMSF on two benchmark datasets are rigorously validated by leave-one-out cross-validation(LOOCV) and fivefold cross-validation (5-fold CV). The experimental results showed that DMFMSF is superior over several existing computational approaches. In addition, five important diseases, hepatocellular carcinoma, breast cancer, acute myeloid leukemia, colorectal cancer, and coronary artery disease were applied in case studies. The results suggest that DMFMSF can be used as an accurate and efficient computational tool for predicting circRNA-disease associations.

Tumor suppressor gene DLC1: Its modifications, interactive molecules, and potential prospects for clinical cancer application

Deleted in liver cancer 1 (DLC1) is a recognized tumor suppressor gene that negatively regulates Rho family proteins by hydrolyzing the active GTP-bound state to its inactive GDP-bound state. Active Rho proteins play a positive role in tumorigenesis. Numerous in vitro and in vivo experiments have shown that DLC1 is downregulated or inactivated in various solid tumors, which may be due to the following five reasons: genomic deletion, epigenetic modification and ubiquitin-dependent proteasomal degradation may cause DLC1 underexpression; phosphorylation at the post-translation level may cause DLC1 inactivation; and failure to localize at focal adhesions (FAs) may prevent DLC1 from exerting full activity. All of the causes could be attributed to molecular binding. Experimental evidence suggests that direct or indirect targeting of DLC1 is feasible for cancer treatment. Therefore, elucidating the interaction of DLC1 with its binding partners might provide novel targeted therapies for cancer. In this review, we summarized the binding partners of DLC1 at both the gene and protein levels and expounded a variety of anticancer drugs targeting DLC1 to provide information about DLC1 as a cancer diagnostic indicator or therapeutic target.