circ_0003418 Inhibits Tumorigenesis And Cisplatin Chemoresistance Through Wnt/β-Catenin Pathway In Hepatocellular Carcinoma

Targeting Wnt signaling in cancer drug resistance: Insights from pre-clinical and clinical research

Cancer drug resistance, encompassing both acquired and intrinsic chemoresistance, remains a significant challenge in the clinical management of tumors. While advancements in drug discovery and the development of various small molecules and anti-cancer compounds have improved patient responses to chemotherapy, the frequent and prolonged use of these drugs continues to pose a high risk of developing chemoresistance. Therefore, understanding the primary mechanisms underlying drug resistance is crucial. Wnt proteins, as secreted signaling molecules, play a pivotal role in transmitting signals from the cell surface to the nucleus. Aberrant expression of Wnt proteins has been observed in a variety of solid and hematological tumors, where they contribute to key processes such as proliferation, metastasis, stemness, and immune evasion, often acting in an oncogenic manner. Notably, the role of the Wnt signaling pathway in modulating chemotherapy response in human cancers has garnered significant attention. This review focuses on the involvement of Wnt signaling and its related molecular pathways in drug resistance, highlighting their associations with cancer hallmarks, stemness, and tumorigenesis linked to chemoresistance. Additionally, the overexpression of Wnt proteins has been shown to accelerate cancer drug resistance, with regulation mediated by non-coding RNAs. Elevated Wnt activity reduces cell death in cancers, particularly by affecting mechanisms like apoptosis, autophagy, and ferroptosis. Furthermore, pharmacological compounds and small molecules have demonstrated the potential to modulate Wnt signaling in cancer therapy. Given its impact, Wnt expression can also serve as a prognostic marker and a factor influencing survival outcomes in human cancers.

Circular RNA in Pancreatic Cancer: Biogenesis, Mechanism, Function and Clinical Application

Circular RNAs (circRNAs) are a class of novel RNA molecules featured by single-strand covalently closed circular structure, which not only are extensively found in eukaryotes and are highly conserved, but also conduct paramount roles in the occurrence and progression of pancreatic cancer (PC) through diverse mechanisms. As recent studies have demonstrated, circRNAs typically exhibit tissue-specific and cell specific expression patterns, with strong potential as biomarkers for disease diagnosis and prognosis. On the basis of their localization and specific interactions with DNA, RNA, and proteins, circRNAs are considered to possess specific biological functions by acting as microRNA (miRNA) sponges, RNA binding protein (RBP) sponges, transcriptional regulators, molecular scaffolds and translation templates. On that account, further addressing the technical difficulties in the detection and research of circRNAs and filling gaps in their biological knowledge will definitely push ahead this comparatively young research field and bring circRNAs to the forefront of clinical practice. Thus, this review systematically summarizes the biogenesis, function, molecular mechanisms, biomarkers and therapeutic targets of circRNAs in PC.

The regulatory role of mitotic catastrophe in hepatocellular carcinoma drug resistance mechanisms and its therapeutic potential

This review focuses on the role and underlying mechanisms of mitotic catastrophe (MC) in the regulation of drug resistance in hepatocellular carcinoma (HCC). HCC is one of the leading causes of cancer-related mortality worldwide, posing significant treatment challenges due to its high recurrence rates and drug resistance. Research suggests that MC, as a mechanism of cell death, plays a crucial role in enhancing the efficacy of HCC treatment by disrupting the replication and division mechanisms of tumor cells. The present review summarizes the molecular mechanisms of MC and its role in HCC drug resistance and explores the potential of combining MC with existing cancer therapies to improve treatment outcomes. Future research should focus on the in-depth elucidation of the molecular mechanisms of MC and its application in HCC therapy, providing new insights for the development of more effective treatments.

New insights into the potential of exosomal circular RNAs in mediating cancer chemotherapy resistance and their clinical applications

Chemotherapy resistance typically leads to tumour recurrence and is a major obstacle to cancer treatment. Increasing numbers of circular RNAs (circRNAs) have been confirmed to be abnormally expressed in various tumours, where they participate in the malignant progression of tumours, and play important roles in regulating the sensitivity of tumours to chemotherapy drugs. As exosomes mediate intercellular communication, they are rich in circRNAs and exhibit a specific RNA cargo sorting mechanism. By carrying and delivering circRNAs, exosomes can promote the efflux of chemotherapeutic drugs and reduce intracellular drug concentrations in recipient cells, thus affecting the cell cycle, apoptosis, autophagy, angiogenesis, invasion and migration. The mechanisms that affect the phenotype of tumour stem cells, epithelial-mesenchymal transformation and DNA damage repair also mediate chemotherapy resistance in many tumours. Exosomal circRNAs are diagnostic biomarkers and potential therapeutic targets for reversing chemotherapy resistance in tumours. Currently, the rise of new fields, such as machine learning and artificial intelligence, and new technologies such as biosensors, multimolecular diagnostic systems and platforms based on circRNAs, as well as the application of exosome-based vaccines, has provided novel ideas for precision cancer treatment. In this review, the recent progress in understanding how exosomal circRNAs mediate tumour chemotherapy resistance is reviewed, and the potential of exosomal circRNAs in tumour diagnosis, treatment and immune regulation is discussed, providing new ideas for inhibiting tumour chemotherapy resistance.

A Comprehensive Insight and In Silico Analysis of CircRNAs in Hepatocellular Carcinoma: A Step toward ncRNA-Based Precision Medicine

Circular RNAs (circRNAs) are cardinal players in numerous physiological and pathological processes. CircRNAs play dual roles as tumor suppressors and oncogenes in different oncological contexts, including hepatocellular carcinoma (HCC). Their roles significantly impact the disease at all stages, including initiation, development, progression, invasion, and metastasis, in addition to the response to treatment. In this review, we discuss the biogenesis and regulatory functional roles of circRNAs, as well as circRNA-protein-mRNA ternary complex formation, elucidating the intricate pathways tuned by circRNAs to modulate gene expression and cellular processes through a comprehensive literature search, in silico search, and bioinformatics analysis. With a particular focus on the interplay between circRNAs, epigenetics, and HCC pathology, the article sets the stage for further exploration of circRNAs as novel investigational theranostic agents in the dynamic realm of HCC.

A new strategy for overcoming drug resistance in liver cancer: Epigenetic regulation

Drug resistance in hepatocellular carcinoma has posed significant obstacles to effective treatment. Recent evidence indicates that, in addition to traditional gene mutations, epigenetic recoding plays a crucial role in HCC drug resistance. Unlike irreversible gene mutations, epigenetic changes are reversible, offering a promising avenue for preventing and overcoming drug resistance in liver cancer. This review focuses on various epigenetic modifications relevant to drug resistance in HCC and their underlying mechanisms. Additionally, we introduce current clinical epigenetic drugs and clinical trials of these drugs as regulators of drug resistance in other solid tumors. Although there is no clinical study to prevent the occurrence of drug resistance in liver cancer, the development of liquid biopsy and other technologies has provided a bridge to achieve this goal.

DEAD-Box Helicase 17 circRNA (circDDX17) Reduces Sorafenib Resistance and Tumorigenesis in Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is the most common type of liver malignancy. Despite significant progress in HCC treatment, resistance to chemotherapy and tumor metastasis are the main reasons for the unsatisfactory prognosis of HCC. Circular RNAs (circRNAs) have been extensively documented to play a role in the development of various types of cancer.

AIMS

Here, we investigated the role of DEAD-box helicase 17 circRNA (circDDX17) in HCC and its underlying molecular mechanisms.

METHODS

Our research employed various techniques including reverse transcription-quantitative polymerase chain reaction (RT-qPCR), cell counting kit-8 (CCK-8), flow cytometry, dual luciferase reporter assay, RNA immunoprecipitation (RIP), and western blot analysis. Additionally, we conducted a tumor xenograft assay to investigate the in vivo function of circDDX17.

RESULTS

Firstly, the expression of circDDX17 was downregulated in HCC tissues and cells. Through functional experiments, it was observed that the overexpression of circDDX17 enhanced the sensitivity of sorafenib, promoted apoptosis, and inhibited the process of epithelial-mesenchymal transition (EMT) in vitro. Additionally, in vivo studies revealed that circDDX17 reduced tumor growth and increased sorafenib sensitivity. Mechanically, circDDX17 competitively combined miR-21-5p to suppress PTEN expression and activate the PI3K/AKT pathway. Furthermore, our rescue assays demonstrated that circDDX17 act as a tumor suppressor by blocking sorafenib resistance and tumorigenesis, while the inhibitory effect caused by circDDX17 upregulation was neutralized when miR-21-5p was overexpressed, PTEN was silenced, or the PI3K/AKT pathway was activated.

CONCLUSION

Our findings firstly confirmed that circDDX17 suppressed sorafenib resistance and HCC progression by regulating miR-21-5p/PTEN/PI3K/AKT pathway, which may provide novel biomarkers for the diagnosis, treatment and prognosis of HCC.

Noncoding RNAs and programmed cell death in hepatocellular carcinoma: Significant role of epigenetic modifications in prognosis, chemoresistance, and tumor recurrence rate

Hepatocellular carcinoma (HCC) is the most common type of liver cancer with a high death rate in the world. The molecular mechanisms related to the pathogenesis of HCC have not been precisely defined so far. Hence, this review aimed to address the potential cross-talk between noncoding RNAs (ncRNAs) and programmed cell death in HCC. All related papers in the English language up to June 2023 were collected and screened. The searched keywords in scientific databases, including Scopus, PubMed, and Google Scholar, were HCC, ncRNAs, Epigenetic, Programmed cell death, Autophagy, Apoptosis, Ferroptosis, Chemoresistance, Tumor recurrence, Prognosis, and Prediction. According to the reports, ncRNAs, comprising long ncRNAs, microRNAs, circular RNAs, and small nucleolar RNAs can affect cell proliferation, migration, invasion, and metastasis, as well as cell death-related processes, such as autophagy, ferroptosis, necroptosis, and apoptosis in HCC by regulating cancer-associated genes and signaling pathways, for example, phosphoinositide 3-kinase/Akt, extracellular signal-regulated kinase/MAPK, and Wnt/β-catenin signaling pathways. It seems that ncRNAs, as epigenetic regulators, can be utilized as biomarkers in diagnosis, prognosis, survival and recurrence rates prediction, chemoresistance, and evaluation of therapeutic response in HCC patients. However, more scientific evidence is suggested to be accomplished to confirm these results.

Competitive endogenous RNA networks: Decoding the role of long non-coding RNAs and circular RNAs in colorectal cancer chemoresistance

Colorectal cancer (CRC) is recognized as one of the most common gastrointestinal malignancies across the globe. Despite significant progress in designing novel treatments for CRC, there is a pressing need for more effective therapeutic approaches. Unfortunately, many patients undergoing chemotherapy develop drug resistance, posing a significant challenge for cancer treatment. Non-coding RNAs (ncRNAs) have been found to play crucial roles in CRC development and its response to chemotherapy. However, there are still gaps in our understanding of interactions among various ncRNAs, such as long non-coding RNAs (lncRNAs), circular RNAs (circRNAs) and microRNAs (miRNAs). These ncRNAs can act as either oncogenes or tumour suppressors, affecting numerous biological functions in different cancers including CRC. A class of ncRNA molecules known as competitive endogenous RNAs (ceRNAs) has emerged as a key player in various cellular processes. These molecules form networks through lncRNA/miRNA/mRNA and circRNA/miRNA/mRNA interactions. In CRC, dysregulation of ceRNA networks has been observed across various cellular processes, including proliferation, apoptosis and angiogenesis. These dysregulations are believed to play a significant role in the progression of CRC and, in certain instances, may contribute to the development of chemoresistance. Enriching our knowledge of these dysregulations holds promise for advancing the field of diagnostic and therapeutic modalities for CRC. In this review, we discuss lncRNA- and circRNA-associated ceRNA networks implicated in the emergence and advancement of drug resistance in colorectal carcinogenesis.

The dual roles of circRNAs in Wnt/β-Catenin signaling and cancer progression

Cancer, a complex pathophysiological condition, arises from the abnormal proliferation and survival of cells due to genetic mutations. Dysregulation of cell cycle control, apoptosis, and genomic stability contribute to uncontrolled growth and metastasis. Tumor heterogeneity, microenvironmental influences, and immune evasion further complicate cancer dynamics. The intricate interplay between circular RNAs (circRNAs) and the Wnt/β-Catenin signalling pathway has emerged as a pivotal axis in the landscape of cancer biology. The Wnt/β-Catenin pathway, a critical regulator of cell fate and proliferation, is frequently dysregulated in various cancers. CircRNAs, a class of non-coding RNAs with closed-loop structures, have garnered increasing attention for their diverse regulatory functions. This review systematically explores the intricate crosstalk between circRNAs and the Wnt/β-Catenin pathway, shedding light on their collective impact on cancer initiation and progression. The review explores the diverse mechanisms through which circRNAs modulate the Wnt/β-Catenin pathway, including sponging microRNAs, interacting with RNA-binding proteins, and influencing the expression of key components in the pathway. Furthermore, the review highlights specific circRNAs implicated in various cancer types, elucidating their roles as either oncogenic or tumour-suppressive players in the context of Wnt/β-Catenin signaling. The intricate regulatory networks formed by circRNAs in conjunction with the Wnt/β-Catenin pathway are discussed, providing insights into potential therapeutic targets and diagnostic biomarkers. This comprehensive review delves into the multifaceted roles of circRNAs in orchestrating tumorigenesis through their regulatory influence on the Wnt/β-Catenin pathway.

The dual role of autophagy in the regulation of cancer treatment

As a catabolic process, autophagy through lysosomes degrades defective and damaged cellular materials to support homeostasis in stressful conditions. Therefore, autophagy dysregulation is associated with the induction of several human pathologies, including cancer. Although the role of autophagy in cancer progression has been extensively studied, many issues need to be addressed. The available evidence suggest that autophagy shows both cytoprotective and cytotoxic mechanisms. This dual role of autophagy in cancer has supplied a renewed interest in the development of novel and effective cancer therapies. Considering this, a deeper understanding of the molecular mechanisms of autophagy in cancer treatment is crucial. This article provides a summary of the recent advances regarding the dual and different mechanisms of autophagy-mediated therapeutic efficacy in cancer.

Circ_0091579 Knockdown Inhibited HCC Proliferation and Glutamine Metabolism Through miR-1270/YAP1 Axis

A growing number of studies have indicated that circRNAs play an important role in the progression of malignant tumors, including hepatocellular carcinoma (HCC). In this study, we designed to explore the abnormal expression of hsa_circ_0091579 (circ_0091579) and its role in the pathogenesis of HCC. In this study, the mRNA levels of circ_0091579, miR-1270, and Yes-associated protein (YAP1) were assessed by quantitative real-time polymerase chain reaction (qRT-PCR). RNase R and Actinomycin D were used to test the stability of circ_0091579. Cell Counting Kit-8 (CCK-8) was used to measure cell viability. Tubule formation assay was used to determine the effect of HCC cells on the number of tubes. Cell apoptosis was detected by flow cytometry. Western blot was used for the protein levels. Transwell and wound healing tests were used to measure the abilities of invasion and migration. The effect of circ_0091579 knockdown on tumor growth was verified in vivo by xenograft tumor assay and Immunohistochemistry (IHC) analysis. Dual-luciferase reporter or RIP assay was used to detect the relationship between miR-1270 and circ_0091579 or YAP1. Glutamine metabolism was determined by ELISA and western blot assays. In the present study, we found that circ_0091579 was upregulated in HCC tissues and cells. Inhibited circ_0091579 expression significantly suppressed proliferation and promoted apoptosis of HCC cells. Moreover, circ_0091579 knockdown inhibited tumor growth in vivo. Bioinformatic prediction and luciferase assay showed that circ_0091579 acted as a molecular sponge for miR-1270 and YAP1 was a target gene of miR-1270. MiR-1270 silencing could reverse the inhibitory effect of circ_0091579 knockdown on HCC progression, and YAP1 overexpression also could reverse the suppressive effect of circ_0091579 silencing on HCC progression. Meanwhile, miR-1270 inhibitor could invert the negative regulation effect of circ_0091579 silencing on YAP1 expression. Circ_0091579 promoted HCC progression by regulating the miR-1270/YAP1 axis, and our study might offer novel biomarkers and therapeutic targets for HCC.

Characterization of circRNAs in established osimertinib‑resistant non‑small cell lung cancer cell lines

Drug resistance is an urgent problem to be solved in the treatment of non‑small‑cell lung cancer (NSCLC). Osimertinib is a third‑generation EGFR‑tyrosine kinase inhibitor, which can improve the efficacy and quality of life of patients; however, the inevitable resistance after long‑term use of osimertinib often leads to treatment failure. Cell lines are key tools for basic and preclinical studies. At present, few osimertinib‑resistant cell lines (HCC827‑OR and H1975‑OR) have been established. In the present study, osimertinib‑resistant cell lines were established by gradually increasing the drug concentration. Half‑maximal inhibitory concentration (IC50), cell morphology, whole exon sequencing, Cell Counting Kit‑8 assay, EdU staining and flow cytometry were used to evaluate the osimertinib‑resistant cell lines. Western blot analysis was used to detect the expression levels of key proteins involved in osimertinib resistance. The circular RNA (circRNA) expression profile was identified by RNA sequencing (RNA‑seq) analysis of HCC827, HCC827‑OR, H1975 and H1975‑OR cells. Subsequently, the biological roles of differentially expressed circRNAs were explored in in vitro studies. Osimertinib‑resistant cell lines were successfully established via treatment with an increasing concentration of osimertinib. Osimertinib IC50 and proliferation of resistant cells were much higher than those of sensitive cells. Notably, phosphorylated (p)‑AKT and p‑ERK were markedly activated in resistant cells, and the inhibitory effect of osimertinib on p‑AKT and p‑ERK was weaker in resistant cells than that in parental cells. RNA‑seq analysis identified differentially expressed circRNAs in HCC827, HCC827‑OR, H1975 and H1975‑OR cells. The most dysregulated circRNAs (circPDLIM5 and circPPP4R1) were selected for further functional study. Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the host genes of differentially expressed circRNAs were associated with 'endocytosis' and 'regulation of autophagy'. In conclusion, the present study established osimertinib‑resistant cell lines and revealed that circRNAs may serve as a promising biomarker in NSCLC osimertinib resistance.

Combating drug resistance in hepatocellular carcinoma: No awareness today, no action tomorrow

Hepatocellular carcinoma (HCC), the sixth most common cancer worldwide, is associated with a high degree of malignancy and poor prognosis. Patients with early HCC may benefit from surgical resection to remove tumor tissue and a margin of healthy tissue surrounding it. Unfortunately, most patients with HCC are diagnosed at an advanced or distant stage, at which point resection is not feasible. Systemic therapy is now routinely prescribed to patients with advanced HCC; however, drug resistance has become a major obstacle to the treatment of HCC and exploring purported mechanisms promoting drug resistance remains a challenge. Here, we focus on the determinants of drug resistance from the perspective of non-coding RNAs (ncRNAs), liver cancer stem cells (LCSCs), autophagy, epithelial-mesenchymal transition (EMT), exosomes, ferroptosis, and the tumor microenvironment (TME), with the aim to provide new insights into HCC treatment.

Serum Exosomes-Based Biomarker circ_0008928 Regulates Cisplatin Sensitivity, Tumor Progression, and Glycolysis Metabolism by miR-488/HK2 Axis in Cisplatin-Resistant Nonsmall Cell Lung Carcinoma

Background: Nonsmall cell lung carcinoma (NSCLC) is a major cause of cancer-related death worldwide. The resistance of NSCLC to chemical drugs, such as cisplatin (CDDP), poses a heavy burden for NSCLC therapy. Herein, the effects of circular_0008928 (circ_0008928) on the CDDP sensitivity and biological behavior of CDDP-resistant NSCLC cells and underlying mechanism are revealed. Materials and Methods: The expression of circ_0008928 and microRNA-488 (miR-488) was detected by quantitative real-time polymerase chain reaction. The expression of hexokinase 2 (HK2) protein and exosome-specific proteins was determined by Western blot. The half-maximal inhibitory concentration (IC50) value of CDDP was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cell proliferation and migratory and invasive abilities were illustrated by cell counting kit-8 and transwell assays. Cell glycolysis metabolism was illustrated by extracellular acidification rate assay, glucose kit and lactate kit assays and Western blot analysis. The binding sites between miR-488 and circ_0008928 or HK2 were predicted by starbase or microT-CDS online database, and identified by dual-luciferase reporter and RNA immunoprecipitation assays. Results: Circ_0008928 expression and HK2 protein expression were significantly upregulated, while miR-488 expression was obviously downregulated in NSCLC cells and CDDP-resistant NSCLC cells. Circ_0008928 expression was increased in serum exosomes of CDDP-resistant NSCLC patients compared with CDDP-sensitive NSCLC patients. In addition, circ_0008928 silencing improved CDDP sensitivity and attenuated CDDP-induced cell proliferation, migration, invasion, and glycolysis metabolism. Circ_0008928 was a sponge of miR-488, and miR-488 bound to HK2 in CDDP-resistant NSCLC cells. Furthermore, both miR-488 inhibitor and HK2 overexpression attenuated circ_0008928 absence-mediated impacts on CDDP sensitivity and tumor process in CDDP-resistant NSCLC. Conclusions: Circ_0008928 knockdown improved CDDP sensitivity and hindered cell proliferation, migration, invasion, and glycolysis metabolism by miR-488/HK2 axis in CDDP-resistant NSCLC. This finding provides a new mechanism for studying CDDP-resistant therapy in NSCLC.

A spotlight on the interplay between Wnt/β-catenin signaling and circular RNAs in hepatocellular carcinoma progression

Hepatocellular carcinoma (HCC) is one of the deadliest cancers due to multifocal development and distant metastasis resulting from late diagnosis. Consequently, new approaches to HCC diagnosis and treatment are required to reduce mortality rates. A large body of evidence suggests that non-coding RNAs (ncRNAs) are important in cancer initiation and progression. Cancer cells release many of these ncRNAs into the blood or urine, enabling their use as a diagnostic tool. Circular RNAs (CircRNAs) are as a members of the ncRNAs that regulate cancer cell expansion, migration, metastasis, and chemoresistance through different mechanisms such as the Wnt/β-catenin Signaling pathway. The Wnt/β-catenin pathway plays prominent roles in several biological processes including organogenesis, stem cell regeneration, and cell survival. Aberrant signaling of both pathways mentioned above could affect the progression and metastasis of many cancers, including HCC. Based on several studies investigated in the current review, circRNAs have an effect on HCC formation and progression by sponging miRNAs and RNA-binding proteins (RBPs) and regulating the Wnt/β-catenin signaling pathway. Therefore, circRNAs/miRNAs or RBPs/Wnt/β-catenin signaling pathway could be considered promising prognostic and therapeutic targets in HCC.

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

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

Multifaceted role of NF-κB in hepatocellular carcinoma therapy: Molecular landscape, therapeutic compounds and nanomaterial approaches

The predominant kind of liver cancer is hepatocellular carcinoma (HCC) that its treatment have been troublesome difficulties for physicians due to aggressive behavior of tumor cells in proliferation and metastasis. Moreover, stemness of HCC cells can result in tumor recurrence and angiogenesis occurs. Another problem is development of resistance to chemotherapy and radiotherapy in HCC cells. Genomic mutations participate in malignant behavior of HCC and nuclear factor-kappaB (NF-κB) has been one of the oncogenic factors in different human cancers that after nuclear translocation, it binds to promoter of genes in regulating their expression. Overexpression of NF-κB has been well-documented in increasing proliferation and invasion of tumor cells and notably, when its expression enhances, it induces chemoresistance and radio-resistance. Highlighting function of NF-κB in HCC can shed some light on the pathways regulating progression of tumor cells. The first aspect is proliferation acceleration and apoptosis inhibition in HCC cells mediated by enhancement in expression level of NF-κB. Moreover, NF-κB is able to enhance invasion of HCC cells via upregulation of MMPs and EMT, and it triggers angiogenesis as another step for increasing spread of tumor cells in tissues and organs. When NF-κB expression enhances, it stimulates chemoresistance and radio-resistance in HCC cells and by increasing stemness and population of cancer-stem cells, it can provide the way for recurrence of tumor. Overexpression of NF-κB mediates therapy resistance in HCC cells and it can be regulated by non-coding RNAs in HCC. Moreover, inhibition of NF-κB by anti-cancer and epigenetic drugs suppresses HCC tumorigenesis. More importantly, nanoparticles are considered for suppressing NF-κB axis in cancer and their prospectives and results can also be utilized for treatment of HCC. Nanomaterials are promising factors in treatment of HCC and by delivery of genes and drugs, they suppress HCC progression. Furthermore, nanomaterials provide phototherapy in HCC ablation.

Non-coding RNA-based therapeutics in cancer therapy: An emphasis on Wnt/β-catenin control

Non-coding RNA transcripts are RNA molecules that have mainly regulatory functions and they do not encode proteins. microRNAs (miRNAs), lncRNAs and circRNAs are major types of this family and these epigenetic factors participate in disease pathogenesis, especially cancer that their abnormal expression may lead to cancer progression. miRNAs and lncRNAs possess a linear structure, whereas circRNAs possess ring structures and high stability. Wnt/β-catenin is an important factor in cancer with oncogenic function and it can increase growth, invasion and therapy resistance in tumors. Wnt upregulation occurs upon transfer of β-catenin to nucleus. Interaction of ncRNAs with Wnt/β-catenin signaling can determine tumorigenesis. Wnt upregulation is observed in cancers and miRNAs are able to bind to 3'-UTR of Wnt to reduce its level. LncRNAs can directly/indirectly regulate Wnt and in indirect manner, lncRNAs sponge miRNAs. CircRNAs are new emerging regulators of Wnt and by its stimulation, they increase tumor progression. CircRNA/miRNA axis can affect Wnt and carcinogenesis. Overall, interaction of ncRNAs with Wnt can determine proliferation rate, migration ability and therapy response of cancers. Furthermore, ncRNA/Wnt/β-catenin axis can be utilized as biomarker in cancer and for prognostic applications in patients.

The critical role of circular RNAs in drug resistance in gastrointestinal cancers

Nowadays, drug resistance (DR) in gastrointestinal (GI) cancers, as the main reason for cancer-related mortality worldwide, has become a serious problem in the management of patients. Several mechanisms have been proposed for resistance to anticancer drugs, including altered transport and metabolism of drugs, mutation of drug targets, altered DNA repair system, inhibited apoptosis and autophagy, cancer stem cells, tumor heterogeneity, and epithelial-mesenchymal transition. Compelling evidence has revealed that genetic and epigenetic factors are strongly linked to DR. Non-coding RNA (ncRNA) interferences are the most crucial epigenetic alterations explored so far, and among these ncRNAs, circular RNAs (circRNAs) are the most emerging members known to have unique properties. Due to the absence of 5' and 3' ends in these novel RNAs, the two ends are covalently bonded together and are generated from pre-mRNA in a process known as back-splicing, which makes them more stable than other RNAs. As far as the unique structure and function of circRNAs is concerned, they are implicated in proliferation, migration, invasion, angiogenesis, metastasis, and DR. A clear understanding of the molecular mechanisms responsible for circRNAs-mediated DR in the GI cancers will open a new window to the management of GI cancers. Hence, in the present review, we will describe briefly the biogenesis, multiple features, and different biological functions of circRNAs. Then, we will summarize current mechanisms of DR, and finally, discuss molecular mechanisms through which circRNAs regulate DR development in esophageal cancer, pancreatic cancer, gastric cancer, colorectal cancer, and hepatocellular carcinoma.

Role of circular RNA and its delivery strategies to cancer - An overview

With the passage of years and the progress of research on ribonucleic acids, the range of forms in which these molecules have been observed grows. One of them, discovered relatively recently, is circular RNA - covalently closed circles (circRNA). In recent years, there has been a huge increase in the interest of researchers in this group of molecules. It entailed a significant increase in the state of knowledge about them, which in turn caused a dramatic change in their perception. Rather than seeing circular RNAs as curiosities that represent a minor information noise in a cell or a result of RNA misprocessing, they came to be regarded as a common, essential, and potentially extremely useful group of molecules. Nevertheless, the current state of the art of circRNA is full of white cards. A lot of valuable information has been obtained from high-throughput methods to study whole transcriptomes, but many issues related to circular RNAs still need to be clarified. Presumably, each answer obtained will raise several new questions. However, circRNAs have a wealth of potential applications, including therapeutic applications.

Circular RNA circPOFUT1 enhances malignant phenotypes and autophagy-associated chemoresistance via sequestrating miR-488-3p to activate the PLAG1-ATG12 axis in gastric cancer

Circular RNAs are key regulators in regulating the progression and chemoresistance of gastric cancer (GC), suggesting circular RNAs as potential therapeutic targets for GC. The roles of a novel circular RNA circPOFUT1 in GC are unknown. Here, we found that circPOFUT1 was upregulated in GC tissues and cells, and increased circPOFUT1 expression indicated poor prognosis. Overexpression of circPOFUT1 enhanced cell proliferation, migration, invasion and autophagy-associated chemoresistance in GC, which were suppressed by miR-488-3p overexpression. CircPOFUT1 reduced miR-488-3p expression via sponging miR-488-3p in GC cells. PLAG1 interacted with ATG12 and promoted its expression. MiR-488-3p bound to PLAG1 and suppressed the expression of PLAG1 and ATG12 in GC cells. Overexpression of circPOFUT1 enhanced autophagy-associated chemoresistance of GC cells in vivo, but it was inhibited by overexpression of miR-488-3p. Collectively, circPOFUT1 directly sponged miR-488-3p to activate the expression of PLAG1 and ATG12, thus enhancing malignant phenotypes and autophagy-associated chemoresistance in GC. Our findings show the potential of circPOFUT1 as biomarkers and targeting circPOFUT1 as a therapeutic strategy for GC.

Pathogenesis and Current Treatment Strategies of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most frequent liver cancer with high lethality and low five-year survival rates leading to a substantial worldwide burden for healthcare systems. HCC initiation and progression are favored by different etiological risk factors including hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, non-/and alcoholic fatty liver disease (N/AFLD), and tobacco smoking. In molecular pathogenesis, endogenous alteration in genetics (TP53, TERT, CTNNB1, etc.), epigenetics (DNA-methylation, miRNA, lncRNA, etc.), and dysregulation of key signaling pathways (Wnt/β-catenin, JAK/STAT, etc.) strongly contribute to the development of HCC. The multitude and complexity of different pathomechanisms also reflect the difficulties in tailored medical therapy of HCC. Treatment options for HCC are strictly dependent on tumor staging and liver function, which are structured by the updated Barcelona Clinic Liver Cancer classification system. Surgical resection, local ablative techniques, and liver transplantation are valid and curative therapeutic options for early tumor stages. For multifocal and metastatic diseases, systemic therapy is recommended. While Sorafenib had been the standalone HCC first-line therapy for decades, recent developments had led to the approval of new treatment options as first-line as well as second-line treatment. Anti-PD-L1 directed combination therapies either with anti-VEGF directed agents or with anti-CTLA-4 active substances have been implemented as the new treatment standard in the first-line setting. However, data from clinical trials indicate different responses on specific therapeutic regimens depending on the underlying pathogenesis of hepatocellular cancer. Therefore, histopathological examinations have been re-emphasized by current international clinical guidelines in addition to the standardized radiological diagnosis using contrast-enhanced cross-sectional imaging. In this review, we emphasize the current knowledge on molecular pathogenesis of hepatocellular carcinoma. On this occasion, the treatment sequences for early and advanced tumor stages according to the recently updated Barcelona Clinic Liver Cancer classification system and the current algorithm of systemic therapy (first-, second-, and third-line treatment) are summarized. Furthermore, we discuss novel precautional and pre-therapeutic approaches including therapeutic vaccination, adoptive cell transfer, locoregional therapy enhancement, and non-coding RNA-based therapy as promising treatment options. These novel treatments may prolong overall survival rates in regard with quality of life and liver function as mainstay of HCC therapy.

Inhibition of insulin-like growth factor 2 mRNA-binding protein 1 sensitizes colorectal cancer cells to chemotherapeutics

Although colorectal cancer (CRC) treatment has seen a remarkable improvement in the recent years, many patients will develop metastasis due to the resistance of cancer cells to chemotherapeutics. Targeting mechanisms driving the resistance of CRC cells to treatment would significantly reduce cases of metastasis and death. Induction of insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1), a direct target of the Wnt/β-catenin signaling pathway, might promote resistance of CRC cells to treatment via activation of anti-apoptotic pathways and induction of the multidrug resistance (MDR1) membrane transporter that pumps drugs out of the cells. We hypothesized that inhibition of IGF2BP1 will sensitize CRC cells to chemotherapeutics. We used CRC cell lines with different status of activation of Wnt signaling to show that inhibition of IGF2BP1 potentiates the anti-growth and anti-proliferative effects of chemotherapeutics on CRC cells with activated Wnt/β-catenin signaling pathway. We observed that the inhibition of IGF2BP1 significantly increases apoptosis in the same cells. A remarkable reduction in the migratory capability of those cells was noted as well. We found that inhibition of IGF2BP1 is sufficient to decrease the resistance of chemotherapy-resistant cancer cells with activated Wnt/β-catenin signaling pathway. These findings portray IGF2BP1 as a good candidate for CRC therapy.

CircFMN2 Boosts Sorafenib Resistance in Hepatocellular Carcinoma Cells via Upregulating CNBP by Restraining Ubiquitination

Purpose

Noncoding RNAs exert critical biological effects in hepatocellular carcinoma (HCC). The role of circFMN2, a newly discovered functional RNA in prostate cancer and colorectal cancer, was investigated for the first time in sorafenib-resistance HCC cells.

Methods

The level of circFMN2 was assessed via quantitative real-time PCR (qRT-PCR). Cell proliferation was detected via CCK-8 and colony formation assay. Cell apoptosis was measured via the TUNEL assay and flow cytometry analysis. A Western blot assay was conducted to detect the CCHC-type zinc finger nucleic acid binding protein (CNBP) level and ubiquitination. RNA pull-down assay and RNA immunoprecipitation were carried out to explore the interaction between circFMN2 and CNBP.

Results

CircFMN2 was highly expressed in multidrug-resistant (MDR) cells. CircFMN2 overexpression exerted pro-proliferation effects in sorafenib-treated HCC cells, while depletion of circFMN2 displayed negative effect on sorafenib-treated MDR cells. Moreover, CNBP was verified as the binding protein of circFMN2. CNBP was upregulated in MDR cells, which was achieved by inhibition of ubiquitination by circFMN2. Besides, CNBP overexpression was found to boost sorafenib resistance in HCC cells.

Conclusions

CircFMN2 is aberrantly expressed in sorafenib-resistant HCC cells and contributes to sorafenib resistance in HCC cells via upregulation of CNBP by restraining ubiquitination.

Circular RNAs in hepatocellular carcinoma: Recent advances

Circular RNAs (circRNAs) have covalently closed loop structures at both ends, exhibiting characteristics dissimilar to those of linear RNAs. Emerging evidence suggests that aberrantly expressed circRNAs play crucial roles in hepatocellular carcinoma (HCC) by affecting the proliferation, apoptosis and invasive capacity of HCC cells. Certain circRNAs may be used as biomarkers to diagnose and predict the prognosis of HCC. Therefore, circRNAs are expected to become novel biomarkers and therapeutic targets for HCC. Herein, we briefly review the characteristics and biological functions of circRNAs, focusing on their roles in HCC to provide new insights for the early diagnosis and targeted therapy of HCC.

Circ_0001955 Acts as a miR-646 Sponge to Promote the Proliferation, Metastasis and Angiogenesis of Hepatocellular Carcinoma

BACKGROUND

Circular RNA (circRNA) exerts a crucial role in the progression of many cancers, including hepatocellular carcinoma (HCC). However, the function of circ_0001955 in HCC progression has been poorly studied.

AIMS

Elucidating the role and molecular mechanism of circ_0001955 in HCC progression.

METHODS

Quantitative real-time PCR was employed to detect the expression of circ_0001955 and miR-646. Cell counting kit 8 assay, Ethynyl-2-deoxyuridine assay, flow cytometry, transwell assay, and tube formation assay were conducted to measure cell proliferation, metastasis, angiogenesis and apoptosis. Dual-luciferase reporter assay and biotin-labeled RNA pull-down assay were performed to analyze the interactions among circ_0001955, miR-646 and frizzled class receptor 4 (FZD4). Moreover, animal experiments were performed to examine the influence of circ_0001955 on HCC tumor growth in vivo.

RESULTS

Circ_0001955 was a highly expressed circRNA in HCC tissues and cells. Circ_0001955 knockdown inhibited the proliferation, metastasis, angiogenesis, and enhanced the apoptosis of HCC cells. Meanwhile, miR-646 could be sponged by circ_0001955, and its inhibitor could reverse the negative regulation of circ_0001955 knockdown on HCC progression. Further, FZD4 was a target of miR-646, and its overexpression could invert the inhibition effect of miR-646 mimic on HCC progression. Besides, our results also indicated that circ_0001955 promoted FZD4 expression by sponging miR-646. Animal experiment results showed that circ_0001955 silencing restrained HCC tumor growth in vivo.

CONCLUSION

Our findings suggested that circ_0001955 might play a positive role in HCC progression via regulating the miR-646/FZD4 axis, indicating that circ_0001955 might be a potential therapeutic target for HCC.

CircLIFR suppresses hepatocellular carcinoma progression by sponging miR-624-5p and inactivating the GSK-3β/β-catenin signaling pathway

Circular RNAs have been reported to play essential roles in the tumorigenesis and progression of various cancers. However, the biological processes and mechanisms involved in hepatocellular carcinoma (HCC) remain unclear. Initial RNA-sequencing data and qRT-PCR results in our cohort showed that hsa_circ_0072309 (also called circLIFR) was markedly downregulated in HCC tissues. Kaplan-Meier analysis indicated that higher levels of circLIFR in HCC patients correlated with favorable overall survival and recurrence-free survival rates. Both in vitro and in vivo experiments indicated that circLIFR inhibited the proliferation and invasion abilities of HCC cells. We therefore conducted related experiments to explore the mechanism of circLIFR in HCC. Fluorescence in situ hybridization results revealed that circLIFR was mainly located in the cytoplasm, and RNA immunoprecipitation assays indicated that circLIFR was significantly enriched by Ago2 protein. These results suggested that circLIFR may function as a sponge of miRNAs to regulate HCC progression. We further conducted bioinformatics prediction as well as dual-luciferase reporter assays, and the results of which showed that circLIFR could sponge miR-624-5p to stabilize glycogen synthase kinase 3β (GSK-3β) expression. Loss and gain of function experiments demonstrated that regulation of the expression of miR-624-5p or GSK-3β markedly affected HCC progression induced by circLIFR. Importantly, we also proved that circLIFR could facilitate the degradation of β-catenin and prevent its translocation to the nucleus in HCC cells. Overall, our study demonstrated that circLIFR acts as a tumor suppressor in HCC by regulating miR-624-5p and inactivating the GSK-3β/β-catenin signaling pathway.

The functional roles of the circRNA/Wnt axis in cancer

CircRNAs, covalently closed noncoding RNAs, are widely expressed in a wide range of species ranging from viruses to plants to mammals. CircRNAs were enriched in the Wnt pathway. Aberrant Wnt pathway activation is involved in the development of various types of cancers. Accumulating evidence indicates that the circRNA/Wnt axis modulates the expression of cancer-associated genes and then regulates cancer progression. Wnt pathway-related circRNA expression is obviously associated with many clinical characteristics. CircRNAs could regulate cell biological functions by interacting with the Wnt pathway. Moreover, Wnt pathway-related circRNAs are promising potential biomarkers for cancer diagnosis, prognosis evaluation, and treatment. In our review, we summarized the recent research progress on the role and clinical application of Wnt pathway-related circRNAs in tumorigenesis and progression.

Emerging roles of circular RNAs in liver cancer

Hepatocellular carcinoma and cholangiocarcinoma are the most common primary liver tumours, whose incidence and associated mortality have increased over recent decades. Liver cancer is often diagnosed late when curative treatments are no longer an option. Characterising new molecular determinants of liver carcinogenesis is crucial for the development of innovative treatments and clinically relevant biomarkers. Recently, circular RNAs (circRNAs) emerged as promising regulatory molecules involved in cancer onset and progression. Mechanistically, circRNAs are mainly known for their ability to sponge and regulate the activity of microRNAs and RNA-binding proteins, although other functions are emerging (e.g. transcriptional and post-transcriptional regulation, protein scaffolding). In liver cancer, circRNAs have been shown to regulate tumour cell proliferation, migration, invasion and cell death resistance. Their roles in regulating angiogenesis, genome instability, immune surveillance and metabolic switching are emerging. Importantly, circRNAs are detected in body fluids. Due to their circular structure, circRNAs are often more stable than mRNAs or miRNAs and could therefore serve as promising biomarkers - quantifiable with high specificity and sensitivity through minimally invasive methods. This review focuses on the role and the clinical relevance of circRNAs in liver cancer, including the development of innovative biomarkers and therapeutic strategies.

Noncoding RNAs in Drug Resistance of Gastrointestinal Stromal Tumor

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor in the gastrointestinal tracts and a model for the targeted therapy of solid tumors because of the oncogenic driver mutations in KIT and PDGDRA genes, which could be effectively inhibited by the very first targeted agent, imatinib mesylate. Most of the GIST patients could benefit a lot from the targeted treatment of this receptor tyrosine kinase inhibitor. However, more than 50% of the patients developed resistance within 2 years after imatinib administration, limiting the long-term effect of imatinib. Noncoding RNAs (ncRNAs), the non-protein coding transcripts of human, were demonstrated to play pivotal roles in the resistance of various chemotherapy drugs. In this review, we summarized the mechanisms of how ncRNAs functioning on the drug resistance in GIST. During the drug resistance of GIST, there were five regulating mechanisms where the functions of ncRNAs concentrated: oxidative phosphorylation, autophagy, apoptosis, drug target changes, and some signaling pathways. Also, these effects of ncRNAs in drug resistance were divided into two aspects. How ncRNAs regulate drug resistance in GIST was further summarized according to ncRNA types, different drugs and categories of resistance. Moreover, clinical applications of these ncRNAs in GIST chemotherapies concentrated on the prognostic biomarkers and novel therapeutic targets.

CircRNA_0040705 promotes the progression of hepatocellular carcinoma

BACKGROUND

Circular RNAs (circRNAs) are involved in cancer progression. Nonetheless, the role and mechanism of circ_0040705 in hepatocellular carcinoma (HCC) are unclear.

METHODS

The aberrantly expressed circRNAs and microRNAs (miRNAs) in HCC tissues were screened by bioinformatics. Circ_0040705, miR-557, SRY-box transcription factor 2 (SOX2), E-cadherin, and N-cadherin expressions were determined using quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot. Cell counting kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU), Transwell experiments were utilized to examine the changes in HCC cell growth, migration and invasion after circ_0040475 was overexpressed or knocked down. Lung metastasis assay was used to validate the effects of circRNA_0040705 on the lung metastasis of HCC cells in vivo. Binding sequences between circ_0040705 and miR-557, and between miR-557 and SOX2 were verified using dual-luciferase reporter gene experiments.

RESULTS

The expression levels of circ_0040705 and SOX2 mRNA were markedly increased in HCC tissues but miR-557 expression was down-regulated. Circ_0040705 overexpression enhanced the growth, migration, invasion, and the expressions of E-cadherin and N-cadherin of HCC cells, and promoted lung metastasis in vivo whereas circ_0040705 knockdown exerted the opposite effects in HCC cells. Circ_0040705 worked as a sponge for miR-557 to down-modulate miR-557 expression, and miR-557 could specifically down-modulate SOX2 expression.

CONCLUSION

Circ_0040705 facilitates HCC cell growth, migration, and invasion by down-modulating miR-557 expression and up-modulating SOX2 expression.

Circular RNA Circ_0000098 Elevates ALX4 Expression via Adsorbing miR-1204 to Inhibit the Progression of Hepatocellular Carcinoma

Background

Circular RNAs (CircRNAs) feature prominently in the progression of various cancers. However, the biological functions of many circRNAs in hepatocellular carcinoma (HCC) are far from fully clarified. This work is performed to decipher the function of circ_0000098 (circSLC30A7) in modulating the progression of HCC and its molecular mechanism.

Methods

Microarray data (GSE97332) were available from the Gene Expression Omnibus (GEO) database, and circRNA differentially expressed in HCC tissues was screened out by GEO2R tool. Circ_0000098, microRNA-1204 (miR-1204), and aristaless-like homeobox-4 (ALX4) mRNA expressions were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell counting kit-8 (CCK-8), scratch wound healing, and Transwell assays were adopted to determine proliferation, migration, and invasion of HCC cells. ALX4 protein, E-cadherin, N-cadherin, and Vimentin expressions were evaluated by Western blot. In addition, the targeting relationship between miR-1204 and circ_0000098 or ALX4 was studied with dual-luciferase reporter assay and RIP assay.

Results

Circ_0000098 expression level was markedly declined in HCC tissues and cells, and its underexpression was associated with larger tumor size of HCC patients. Knocking down circ_0000098 observably promoted the multiplication, migration, invasion, and epithelial-mesenchymal transition (EMT) of Huh7 and SMMC-7721 cells. Additionally, circ_0000098 was mainly distributed in the cytoplasm of HCC cells, and up-regulated ALX4 expression through competitively decoying miR-1204.

Conclusion

Circ_0000098, as a competitive endogenous RNA (ceRNA) of miR-1204, upregulates ALX4 expression and suppresses the growth, migration, invasion, and EMT of HCC cells.

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.

Circ_0000212 affects proliferation, migration, invasion, apoptosis, and paclitaxel sensitivity of liver cancer cells by targeting miR-139-5p

BACKGROUND

Circ_0000212 is a newly discovered non-coding RNA whose high expression promotes the progression of colorectal cancer. However, the expression patterns and roles of circ_0000212 in liver cancer remain unknown.

AIM

To investigate the effect of circ_0000212 targeting miR-139-5p on cell proliferation, migration, invasion, apoptosis, and paclitaxel sensitivity in liver cancer.

METHODS

RT-qPCR was applied to detect the expression of circ_0000212 and miR-139-5p in liver cancer tissues and adjacent tissues. Pearson correlation analysis was performed to determine the relationship between circ_0000212 and miR-139-5p expression in liver cancer tissues. Dual luciferase reporter assay was used to verify the targeting relationship between circ_0000212 and miR-139-5p. Liver cancer HCC9204 cells were divided into a control group, circ_0000212 interference group, circ_0000212 interference + miR-139-5p inhibitor group, paclitaxel group, paclitaxel + circ_0000212 interference group, and paclitaxel + circ_0000212 interference + miR-139-5p inhibitor group. The rate of inhibited HCC9204 cells was detected using CCK-8 method; the number of clones formed by HCC9204 cells was calculated using colony formation assay; the apoptotic rate of HCC9204 cells was evaluated by flow cytometry; and the migration and invasion of HCC9204 cells were detected by Transwell assay.

RESULTS

Compared with adjacent tissue, the expression level of circ_0000212 in liver cancer tissue was significantly increased (P < 0.05), while the expression level of miR-139-5p was significantly decreased (P < 0.05). There was a negative correlation between the expression of circ_0000212 and miR-139-5p in liver cancer tissues. Circ_0000212 directly interacted with miR-139-5p. Compared with the control group, circ_0000212 expression in HCC9204 cells in the paclitaxel group was significantly reduced (P < 0.05), while miR-139-5p expression was significantly increased (P < 0.05). Compared with the control group, the numbers of clones formed and migrating and invading HCC9204 cells in the interference circ_0000212 group and paclitaxel group were significantly reduced (P < 0.05), and the inhibition rate and apoptosis rate were significantly increased (P < 0.05). Compared with the circ_0000212 interference group, the numbers of clone formed and migrating and invading HCC9204 cells in the interference circ_0000212+miR-139-5p inhibitor group were significantly increased (P < 0.05), and the inhibition rate and apoptosis rate were significantly reduced (P < 0.05). Compared with the paclitaxel group, the numbers of clones formed and migrating and invading HCC9204 cells in the paclitaxel + circ_0000212 interference group were significantly reduced (P < 0.05), and the inhibition rate and apoptosis rate were significantly increased (P < 0.05). Compared with the paclitaxel + circ_0000212 interference group, the numbers of clones formed and migrating and invading HCC9204 cells in the paclitaxel + circ_0000212 interference + miR-139-5p inhibitor group were significantly increased (P < 0.05), and the inhibition rate and apoptosis rate were significantly reduced (P < 0.05).

CONCLUSION

Interfering with circ_0000212 can inhibit cell proliferation, migration, and invasion, induce cell apoptosis, and increase its sensitivity to paclitaxel in liver cancer cells by targeting and up-regulating miR-139-5p.

Research progress of circRNAs in chemotherapy resistance of digestive system neoplasms

Circular RNAs (circRNAs) are a novel class of noncoding RNA molecules with a unique closed continuous loop structure. CircRNAs are abundant in eukaryotic cells, have unique stability and tissue specificity, and can play a biological regulatory role at various levels, such as transcriptional and posttranscriptional levels. Accumulating evidence indicates that circRNAs play critical roles in tumor genesis, development, and chemotherapy. Chemotherapy is a primary type of intervention for most cancers, but its therapeutic efficacy is usually retarded by intrinsic and acquired resistance. CircRNAs regulate tumor chemoresistance through various molecular mechanisms, such as affecting apoptosis, promoting drug transportation, promoting DNA repair, promoting epithelial-mesenchymal transformation, regulating the characteristics of tumor stem cells, and affecting autophagy. This review summarizes the recent progress and mechanisms of circRNAs in cancer cell resistance to chemotherapy.

Dysregulation of Non-coding RNAs mediates Cisplatin Resistance in Hepatocellular Carcinoma and therapeutic strategies

Hepatocellular carcinoma (HCC) is the fourth major contributor to cancer-related deaths worldwide, and patients mostly have poor prognosis. Although several drugs have been approved for the treatment of HCC, cisplatin (CDDP) is still applied in treatment of HCC as a classical chemotherapeutic drug. Unfortunately, the emergence of CDDP resistance has caused HCC patients to exhibit poor drug response. How to mitigate or even reverse CDDP resistance is an urgent clinical issue to be solved. Because of critical roles in biological functional processes and disease developments, non-coding RNAs (ncRNAs) have been extensively studied in HCC in recent years. Importantly, ncRNAs have also been demonstrated to be involved in the development of HCC to CDDP resistance process. Therefore, this review highlighted the regulatory roles of ncRNAs in CDDP resistance of HCC, elucidated the multiple potential mechanisms by which HCC develops CDDP resistance, and attempted to propose multiple drug delivery systems to alleviate CDDP resistance. Recently, ncRNA-based therapy may be a feasible strategy to alleviate CDDP resistance in HCC. Meanwhile, nanoparticles can overcome the deficiencies in ncRNA-based therapy and make it possible to reverse tumor drug resistance. The combined use of these strategies provides clues for reversing CDDP resistance and overcoming the poor prognosis of HCC.

Research Progress on the Functions and Mechanism of circRNA in Cisplatin Resistance in Tumors

Cisplatin is a common chemotherapeutic drug that has been used to treat of numerous tumors, including testicular, lung, bladder, ovarian, liver and head and neck cancers. Although clinical chemotherapy based on cisplatin has shown a remarkable therapeutic effect, the resistance to cisplatin becomes increasingly obvious as a patient uses it for a prolonged period. It not only affects the prognosis of these tumors, but also causes the recurrence of cancer and decreases the overall survival rate. The development of cisplatin resistance involves several mechanisms, including DNA damage repair, ATP-binding cassette (ABC) transporter, autophagy, cancer stem cells (CSCs), epithelial-mesenchymal transition (EMT), and other related signaling pathways. Interestingly, these mechanisms have been found to be influenced by circular RNAs (circRNAs) to regulate tumor proliferation, invasion, chemosensitivity, and other biological behaviors in the tumor microenvironment (TME). In recent years, circRNAs in cisplatin resistance in tumors, especially lung cancer and gastric cancer, have gradually drawn peoples' attention. This review summarizes recent studies on the functions and mechanisms of circRNAs in cisplatin resistance. We emphasize that circRNA can be used as a promising target gene to improve drug resistance and therapeutic efficacy.

The functional roles, cross-talk and clinical implications of m6A modification and circRNA in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide. HCC has high rates of death and recurrence, as well as very low survival rates. N6-methyladenosine (m6A) is the most abundant modification in eukaryotic RNAs, and circRNAs are a class of circular noncoding RNAs that are generated by back-splicing and they modulate multiple functions in a variety of cellular processes. Although the carcinogenesis of HCC is complex, emerging evidence has indicated that m6A modification and circRNA play vital roles in HCC development and progression. However, the underlying mechanisms governing HCC, their cross-talk, and clinical implications have not been fully elucidated. Therefore, in this paper, we elucidated the biological functions and molecular mechanisms of m6A modification in the carcinogenesis of HCC by illustrating three different regulatory factors ("writer", "eraser", and "reader") of the m6A modification process. Additionally, we dissected the functional roles of circRNAs in various malignant behaviors of HCC, thereby contributing to HCC initiation, progression and relapse. Furthermore, we demonstrated the cross-talk and interplay between m6A modification and circRNA by revealing the effects of the collaboration of circRNA and m6A modification on HCC progression. Finally, we proposed the clinical potential and implications of m6A modifiers and circRNAs as diagnostic biomarkers and therapeutic targets for HCC diagnosis, treatment and prognosis evaluation.

Current Molecular Biology and Therapeutic Strategy Status and Prospects for circRNAs in HBV-Associated Hepatocellular Carcinoma

Circular RNAs (circRNAs) are newly classified noncoding RNA (ncRNA) members with a covalently closed continuous loop structure that are involved in immune responses against hepatitis B virus (HBV) infections and play important biological roles in the occurrence and pathogenesis of HCC progression. The roles of circRNAs in HBV-associated HCC (HBV-HCC) have gained increasing attention. Substantial evidence has revealed that both tissue and circulating circRNAs may serve as potential biomarkers for diagnostic, prognostic and therapeutic purposes. So far, at least four circRNA/miRNA regulatory axes such as circRNA_101764/miR-181, circRNA_100338/miR-141-3p, circ-ARL3/miR-1305, circ-ATP5H/miR-138-5p, and several circulating circRNAs were reported to be associated with HBV-HCC development. Notably, TGF/SMAD, JAK/STAT, Notch and Wnt/β-catenin signaling pathways may play pivotal roles in this HBV-driven HCC via several circRNAs. Moreover, in non-HBV HCC patients or HCC patients partially infected by HBV, numerous circRNAs have been identified to be important regulators impacting the malignant biological behavior of HCC. Furthermore, the role of circRNAs in HCC drug resistance has become a focus of research with the aim of reversing chemoresistance and immune resistance. Herein, we review the molecular biology of circRNAs in HBV-HCC and their potential in therapeutic strategies.

Berberine Sensitizes Human Hepatoma Cells to Regorafenib via Modulating Expression of Circular RNAs

Regorafenib resistance is a key limiting factor in the treatment of advanced hepatocellular carcinoma (HCC). Increasing evidence has demonstrated that Berberine (BBR) can synergistically enhance the therapeutic effect of various chemotherapeutic agents. However, the contribution of BBR on regorafenib therapy remains unclear. The purpose of this study was to explore the combined treatment effect of berberine and regorafenib in HCC. We found that BBR enhanced the cytotoxicity of regorafenib in HCC cells. Compared with regorafenib alone, the combined treatment of BBR and regorafenib significantly inhibited the proliferation of HCC cells and induced cellular apoptosis. Meanwhile, the combined treatment group with BBR (10mg/kg/day) and regorafenib (5mg/kg/day) had a dramatic inhibitory effect on the growth of HCC xenograft tumors in nude mice. The increased apoptosis of xenograft tumors was seen in the combined treatment group. Moreover, a comprehensive circular RNA sequencing was performed to identify differentially expressed circRNAs in HCC cells after exposure to 100µM BBR and 5µM regorafenib. The volcano plot and scatter plot analyses revealed that there were 58 up-regulated and 19 down-regulated differentially expressed circRNAs between the combination treatment and control groups. Among them, the expression of hsa_circ_0032029 and hsa_circ_0008928 were up-regulated in HCC cells after treatment with 100µM BBR and 5µM regorafenib. Taken together, this study demonstrated that BBR enhanced the anti-HCC effect of regorafenib both in vitro and in vivo. The synergistic anti-tumor effect of BBR and regorafenib might be related to the up-regulation of hsa_circ_0032029 and hsa_circ_0008928 in HCC cells.

Circular RNAs in Hepatocellular Carcinoma: Emerging Functions to Clinical Significances

Hepatocellular carcinoma (HCC) is the most common primary cancer of the liver and carries high morbidity and mortality. Diagnosing HCC at an early stage is challenging. Therefore, finding new, highly sensitive and specific diagnostic biomarkers for the diagnosis and prognosis of HCC patients is extremely important. Circular RNAs (circRNAs) are a class of non-coding RNAs with covalently closed loop structures. They are characterized by remarkable stability, long half-life, abundance and evolutionary conservation. Recent studies have shown that many circRNAs are expressed aberrantly in HCC tissues and have important regulatory roles during the development and progression of HCC. Hence, circRNAs are promising biomarkers for the diagnosis and prognosis of HCC. This review: (i) summarizes the biogenesis, categories, and functions of circRNAs; (ii) focuses on current progress of dysregulated expression of circRNAs in HCC with regard to regulation of the tumor hallmarks, “stemness” of cancer cells, and immunotherapy; (iii) highlights circRNAs as potential biomarkers and therapeutic targets for HCC; and (iv) discusses some of the challenges, questions and future perspectives of circRNAs research in HCC.

Circular RNAs: new biomarkers of chemoresistance in cancer

Chemotherapeutics are validated conventional treatments for patients with advanced cancer. However, with continual application of chemotherapeutics, chemoresistance, which is often predictive of poor prognosis, has gradually become a concern in recent years. Circular RNAs (circRNAs), a class of endogenous noncoding RNAs (ncRNAs) with a closed-loop structure, have been reported to be notable targets and markers for the prognosis, diagnosis, and treatment of many diseases, particularly cancer. Although dozens of studies have shown that circRNAs play major roles in drug-resistance activity in tumors, the mechanisms by which circRNAs affect chemoresistance have yet to be explored. In this review, we describe the detailed mechanisms of circRNAs and chemotherapeutics in various cancers and summarize potential therapeutic targets for drug-resistant tumors.

The Latest Overview of circRNA in the Progression, Diagnosis, Prognosis, Treatment, and Drug Resistance of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the main causes of tumor-related deaths worldwide. Due to the lack of obvious early symptoms and the lack of sensitive screening indicators in the early stage of HCC, the vast majority of patients are diagnosed with advanced or metastatic HCC, resulting in dissatisfactory treatment result. Therefore, it is urgent to determine effective and sensitive diagnostic and prognostic indicators and to determine new therapeutic targets. Circular RNA (circRNA) is a type of non-coding RNA that has been neglected for a long time. In recent years, it has been proved to play an important role in the development of many human diseases. Increasing evidence shows that change in circRNA expression has an extensive effect on the biological behavior of HCC. In this study, we comprehensively tracked the latest progress of circRNA in the pathogenesis of HCC, and reviewed its role as a biomarker for diagnosis and prognosis prediction in patients with HCC. In addition, we also summarized the potential of circRNA as therapeutic target in HCC and its relationship with HCC drug resistance, providing clues for the clinical development of circRNA-based therapeutic strategies.

The Roles of circRNAs in Liver Cancer Immunity

Circular RNAs (circRNAs) are stable covalently closed non-coding RNAs (ncRNAs). Many studies indicate that circRNAs are involved in the pathological and physiological processes of liver cancer. However, the functions of circRNAs in liver cancer immunity are less known. In this review, we summarized the functions of circRNAs in liver cancer, including proliferative, metastasis and apoptosis, liver cancer stemness, cell cycle, immune evasion, glycolysis, angiogenesis, drug resistance/sensitizer, and senescence. Immune escape is considered to be one of the hallmarks of cancer development, and circRNA participates in the immune escape of liver cancer cells by regulating natural killer (NK) cell function. CircRNAs may provide new ideas for immunotherapy in liver cancer.

Circ_0031242 Silencing Mitigates the Progression and Drug Resistance in DDP-Resistant Hepatoma Cells by the miR-924/POU3F2 Axis

Background

Circular RNAs (circRNAs) have been implicated in the progression and chemoresistance development of hepatocellular carcinoma (HCC). However, the precise parts of circ_0031242 in HCC chemoresistance are still not fully understood.

Methods

The levels of circ_0031242, miR-924 and POU class 3 homeobox 2 (POU3F2) were detected by quantitative real-time polymerase chain reaction (qRT-PCR) assay or Western blot analysis. IC₅₀ value for cisplatin (DDP) and cell viability were measured by the cell counting kit-8 (CCK-8) assay. Cell migration, invasion and apoptosis were assessed by transwell assay and flow cytometry, respectively. Targeted correlations among circ_0031242, miR-924 and POU3F2 were verified by the dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.

Results

Our data revealed that circ_0031242 was associated with HCC resistance to DDP. The silencing of circ_0031242 diminished DDP resistance, suppressed cell viability, migration, invasion and promoted apoptosis of DDP-resistant HCC cells (Huh7-R and SNU-387-R) in vitro, as well as enhanced DDP sensitivity in vivo. Mechanistically, circ_0031242 directly interacted with miR-924 by binding to miR-924. Moreover, miR-924 was a downstream effector of circ_0031242 function. POU3F2 was a direct target of miR-924, and miR-924 overexpression regulated DDP-resistant HCC cell progression and DDP resistance by down-regulating POU3F2. Furthermore, circ_0031242 modulated POU3F2 expression through sponging miR-924.

Conclusion

Our findings identified that circ_0031242 functioned as an important regulator in DDP-resistant HCC cell progression and DDP resistance through the miR-924/POU3F2 axis, illuminating circ_0031242 as a potential therapeutic target for the chemoresistant HCC.

Circ_LDLR Knockdown Suppresses Progression of Hepatocellular Carcinoma via Modulating miR-7/RNF38 Axis

Background

Hepatocellular carcinoma (HCC) is a horrible malignancy derived from liver. Circular RNAs (circRNAs) act important roles in the pathogenesis and progression of human diseases, including HCC. The current assay intended to investigate the function of circRNA low-density lipoprotein receptor (circ_LDLR) in HCC and clarify the underlying mechanism.

Materials and Methods

Expression of circ_LDLR, microRNA (miR)-7 and ring finger protein 38 (RNF38) was determined by quantitative real-time PCR (qRT-PCR) or Western blot analysis. Flow cytometry was used to detect cell cycle distribution and apoptosis. Cell colony formation ability and viability were examined by colony formation and methyl thiazolyl tetrazolium (MTT) assays, respectively. Levels of cell proliferation and epithelia-mesenchymal transition (EMT) biomarker proteins were analyzed via Western blot assay. Cell migration and invasion were monitored by Transwell assay, and target relationship between miR-7 and circ_LDLR or RNF38 was validated by dual-luciferase reporter assay. Xenograft model was established to explore the role of circ_LDLR in vivo.

Results

Expression of circ_LDLR and RNF38 was upregulated, but miR-7 expression was downregulated in HCC tissues and cells. Circ_LDLR knockdown significantly inhibited cell proliferation, migration, invasion and EMT in HCC cells. Circ_LDLR acted as a sponge of miR-7, and interference of miR-7 could attenuate circ_LDLR knockdown-induced inhibitory effects on malignant behaviors of HCC cells. Besides, miR-7 also repressed cell proliferation and metastasis of HCC cells, by targeting RNF38. Depletion of circ_LDLR could suppress tumor growth in vivo.

Conclusion

Depletion of circ_LDLR restrained HCC cell proliferation, metastasis and tumorigenesis through the regulation on miR-7/RNF38 axis, affording a promising therapeutic target for HCC.

The role of microRNA-338-3p in cancer: growth, invasion, chemoresistance, and mediators

Cancer still remains as one of the leading causes of death worldwide. Metastasis and proliferation are abnormally increased in cancer cells that subsequently, mediate resistance of cancer cells to different therapies such as radio-, chemo- and immune-therapy. MicroRNAs (miRNAs) are endogenous short non-coding RNAs that can regulate expression of target genes at post-transcriptional level and capable of interaction with mRNA-coding genes. Vital biological mechanisms including apoptosis, migration and differentiation are modulated by these small molecules. MiRNAs are key players in regulating cancer proliferation and metastasis as well as cancer therapy response. MiRNAs can function as both tumor-suppressing and tumor-promoting factors. In the present review, regulatory impact of miRNA-338-3p on cancer growth and migration is discussed. This new emerging miRNA can regulate response of cancer cells to chemotherapy and radiotherapy. It seems that miRNA-338-3p has dual role in cancer chemotherapy, acting as tumor-promoting or tumor-suppressor factor. Experiments reveal anti-tumor activity of miRNA-338-3p in cancer. Hence, increasing miRNA-338-3p expression is of importance in effective cancer therapy. Long non-coding RNAs, circular RNAs and hypoxia are potential upstream mediators of miRNA-338-3p in cancer. Anti-tumor agents including baicalin and arbutin can promote expression of miRNA-338-3p in suppressing cancer progression. These topics are discussed to shed some light on function of miRNA-338-3p in cancer cells.

Circular RNA circ_0004507 contributes to laryngeal cancer progression and cisplatin resistance by sponging miR-873 to upregulate multidrug resistance 1 and multidrug resistance protein 1

BACKGROUND

Circular RNAs (circRNAs) play critical roles in various types of cancer and chemosensitivity.

METHODS

The expression levels of circ_0004507 and microRNA-873 (miR-873) were measured by quantitative real-time polymerase chain reaction (qRT-PCR). The interaction between circ_0004507 and miR-873 was predicted by circinteractome and verified by dual-luciferase reporter assay and RNA pull-down assay. Xenograft tumor model was established to confirm the biological role of circ_0004507 in vivo.

RESULTS

circ_0004507 was highly expressed and miR-873 was lowly expressed in laryngeal cancer tissues. circ_0004507 knockdown or miR-873 overexpression inhibited cell proliferation, migration and invasion, and increased apoptosis and cisplatin sensitivity in laryngeal cancer cells. miR-873 was identified as a direct target of circ_0004507. circ_0004507 interference inhibited tumor growth and promoted cisplatin sensitivity by upregulating miR-873 in vivo.

CONCLUSION

Knockdown of circ_0004507 inhibited laryngeal cancer progression and cisplatin resistance by sponging miR-873, providing a potential target for laryngeal cancer therapy.

N6-methyladenosine-modified CircRNA-SORE sustains sorafenib resistance in hepatocellular carcinoma by regulating β-catenin signaling

Background and aims

Accumulating evidence suggests that the primary and acquired resistance of hepatocellular carcinoma (HCC) to sorafenib is mediated by multiple molecular, cellular, and microenvironmental mechanisms. Understanding these mechanisms will enhance the likelihood of effective sorafenib therapy.

Methods

In vitro and in vivo experiments were performed and clinical samples and online databases were acquired for clinical investigation.

Results

In this study, we found that a circular RNA, circRNA-SORE, which is up-regulated in sorafenib-resistant HCC cells, was necessary for the maintenance of sorafenib resistance, and that silencing circRNA-SORE substantially increased the efficacy of sorafenib-induced apoptosis. Mechanistic studies determined that circRNA-SORE sequestered miR-103a-2-5p and miR-660-3p by acting as a microRNA sponge, thereby competitively activating the Wnt/β-catenin pathway and inducing sorafenib resistance. The increased level of circRNA-SORE in sorafenib-resistant cells resulted from increased RNA stability. This was caused by an increased level of N⁶-methyladenosine (m⁶A) at a specific adenosine in circRNA-SORE. In vivo delivery of circRNA-SORE interfering RNA by local short hairpin RNA lentivirus injection substantially enhanced sorafenib efficacy in animal models.

Conclusions

This work indicates a novel mechanism for maintaining sorafenib resistance and is a proof-of-concept study for targeting circRNA-SORE in sorafenib-treated HCC patients as a novel pharmaceutical intervention for advanced HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-020-01281-8.