Comprehensive circular RNA expression profile in radiation-treated HeLa cells and analysis of radioresistance-related circRNAs

The role of circRNAs in resistance to doxorubicin

Doxorubicin is an anthracyline recognized as an antitumor antibiotic agent. It is widely used in the chemotherapeutic regimens in different types of cancers. Resistance to doxorubicin is a major clinical obstacle and main cause of failure in cancer chemotherapy. Among different mechanisms involved in this process, the role of epigenetic factors has been highlighted. Circular RNAs (circRNAs) have a prominent role in this process. Here, we summarize the recent findings on the role of circRNAs in doxorubicin resistance, particularly in breast cancer and osteosarcoma and underscore their clinical application as potential biomarkers and therapeutic targets in this field. Recognition of the underlying mechanism of circRNAs involvement in doxorubicin resistance will expand our understanding of chemoresistance establishment and may provide a prospect to develop circRNA-based predictive biomarkers of chemotherapy or therapeutic strategies for cancer patients.

CircFOXO3 upregulation mediates the radioresistance of glioblastoma by affecting cellular metabolome

Introduction

Radioresistance remains a significant challenge in the treatment of glioblastoma multiforme (GBM), the most prevalent and lethal brain cancer in adults. Metabolic alterations are known to contribute to radioresistance by activating antioxidant responses and promoting DNA repair. However, the role of circular RNAs in this process, particularly circFOXO3, is not well understood.

Methods

In this study, we investigated the expression of circFOXO3 in glioma cells exposed to radiation and in recurrent GBM tissues. We performed knockdown and overexpression experiments in vitro and in vivo to assess the effects of circFOXO3 on radiosensitivity. Metabolomic profiling was conducted to explore the metabolic changes associated with circFOXO3 overexpression following irradiation.

Results

Our results showed significant upregulation of circFOXO3 in glioma cells upon radiation exposure and in recurrent GBM tissues. Knockdown of circFOXO3 increased radiosensitivity both in vitro and in vivo, whereas overexpression of circFOXO3 attenuated radiosensitivity. Metabolomic analysis revealed substantial alterations in lipid and organic compound profiles between circFOXO3-overexpressing and control groups. Additionally, circFOXO3 suppression increased proapoptotic protein levels (Caspase 7 and Bax) and decreased anti-apoptotic protein Bcl-2 levels following radiotherapy.

Discussion

These findings demonstrate the pivotal role of circFOXO3 in promoting tumor radioresistance through metabolic modulation, suggesting that circFOXO3 could serve as a potential diagnostic and therapeutic target for GBM.

Circular RNAs: Novel Players in Cancer Mechanisms and Therapeutic Strategies

Circular RNAs (circRNAs) are a novel class of noncoding RNAs that have emerged as pivotal players in gene regulation. Our understanding of circRNAs has greatly expanded over the last decade, with studies elucidating their biology and exploring their therapeutic applications. In this review, we provide an overview of the current understanding of circRNA biogenesis, outline their mechanisms of action in cancer, and assess their clinical potential as biomarkers. Furthermore, we discuss circRNAs as a potential therapeutic strategy, including recent advances in circRNA production and translation, along with proof-of-concept preclinical studies of cancer vaccines.

CircRNA_101491 regulated the radiation sensitivity of esophageal squamous cell carcinomas via sponging miR-125a-5p

BACKGROUND

At present, it has been found that many patients have acquired resistance to radiotherapy, which greatly reduces the effect of radiotherapy and further affects the prognosis. CircRNAs is involved in the regulation of radiosensitivity of many kinds of tumor cells. Therefore, the main purpose of this study is to explore the regulatory effect of CircRNA_101491 on radiosensitivity of ESCC and its related mechanism.

METHODS

We established ESCC radiation-resistant cell line (KYSE150R cell) by gradient dose method, and tested the difference of KYSE150 between KYSE150R cell and parent cell in vitro. Then, after knocking down the expression of CircRNA_101491, a series of in vitro experiments were conducted to verify the effects of CircRNA_101491 on the phenotype and radiosensitivity of KYSE150R cells, and further analyzed the related regulatory mechanism. In addition, we also used the model of transplanted tumor in nude mice to investigate the effect of CircRNA_101491 on the radiosensitivity of ESCC in vivo.

RESULTS

According to a series of in vitro experiments, we confirmed that KYSE150R cells lost the epithelial phenotype and obtained interstitial cell-like phenotype, and found that CircRNA_101491 was highly expressed in KYSE150R cells. In addition, we found that knocking down the expression of CircRNA_101491 will lift the inhibition of miR-125a-5p, and then reverse the process of EMT, accelerate the process of apoptosis, thus play a role in radiosensitization. The in vivo experiment of transplanted tumor in nude mice also showed that knocking down the expression of CircRNA_101491 could enhance the radiosensitivity of ESCC.

CONCLUSION

In conclusion, we confirmed that interfering with the expression of CircRNA_101491 can relieve the inhibition of miR-125a-5p, thus reverse the process of interstitial phenotype, accelerate the process of apoptosis, and enhance the radiosensitivity of ESCC.

The research progress on radiation resistance of cervical cancer

Cervical carcinoma is the most prevalent gynecology malignant tumor and ranks as the fourth most common cancer worldwide, thus posing a significant threat to the lives and health of women. Advanced and early-stage cervical carcinoma patients with high-risk factors require adjuvant treatment following surgery, with radiotherapy being the primary approach. However, the tolerance of cervical cancer to radiotherapy has become a major obstacle in its treatment. Recent studies have demonstrated that radiation resistance in cervical cancer is closely associated with DNA damage repair pathways, the tumor microenvironment, tumor stem cells, hypoxia, cell cycle arrest, and epigenetic mechanisms, among other factors. The development of tumor radiation resistance involves complex interactions between multiple genes, pathways, and mechanisms, wherein each factor interacts through one or more signaling pathways. This paper provides an overview of research progress on an understanding of the mechanism underlying radiation resistance in cervical cancer.

Association of long noncoding RNA MALAT1 with the radiosensitivity of lung adenocarcinoma cells via the miR-140/PD-L1 axis

Objective

To investigate the effect of MALAT1 on the modulating the radiosensitivity of lung adenocarcinoma, through regulation of the expression of the miR-140/PD-L1 axis.

Methods

The online databases UALCAN and dbDEMC were searched for the MALAT1 and miR-140 expressions in patients with lung adenocarcinoma (LUAD), respectively. Then analyze their relationship with overall survival rates separately in the UALCAN and ONCOMIR databases. A functional analysis was performed for A549 cells by transfecting small-interfering RNAs or corresponding plasmids after radiotherapy. Xenograft models of LUAD exposed to radiation were established to further observe the effects of MALAT1 on the radiosensitivity of LUAD. The luciferase assay and reverse transcription-polymerase chain reaction were performed to assess the interaction between miR-140 and MALAT1 or PD-L1.

Results

MALAT1 were overexpressed in human LUAD tumor tissues and cell lines, while miR-140 were inhibited. MALAT1 knockdown or miR-140 increase suppressed cell proliferation and promoted cell apoptosis in LUAD after irradiation. LUAD xenograft tumor growth was also inhibited by MALAT1 knockdown combined with irradiation. miR-140 could directly bind with MALAT1 or PD-L1. Furthermore, MALAT1 knockdown inhibited PD-L1 mRNA and protein expressions by upregulating miR-140 in LUAD cells.

Conclusion

MALAT1 may function as a sponge for miR-140a-3p to enhance the PD-L1 expression and decrease the radiosensitivity of LUAD. Our results suggest that MALAT1 might be a promising therapeutic target for the radiotherapy sensitization of LUAD.

Targeting the radiation-induced ARv7-mediated circNHS/miR-512-5p/XRCC5 signaling with Quercetin increases prostate cancer radiosensitivity

Background

Radiation therapy (RT) with androgen deprivation therapy (ADT) is an effective therapy to suppress the locally advanced prostate cancer (PCa). However, we unexpectedly found that RT could also induce the androgen receptor splice variant 7 (ARv7) expression to decrease the radiosensitivity.

Methods

The study was designed to target ARv7 expression with Quercetin or ARv7-shRNA that leads to enhancing and increasing the radiation sensitivity to better suppress the PCa that involved the modulation of the circNHS/miR-512-5p/XRCC5 signaling.

Results

Mechanism studies revealed that RT-induced ARv7 may function via altering the circNHS/miR-512-5p/XRCC5 signaling to decrease the radiosensitivity. Results from preclinical studies using multiple in vitro cell lines and in vivo mouse models concluded that combining RT with the small molecule of Quercetin to target full-length AR and ARv7 could lead to better efficacy to suppress PCa progression.

Conclusion

Together, these results suggest that ARv7 may play key roles to alter the PCa radiosensitivity, and targeting this newly identified ARv7 mediated circNHS/miR-512-5p/XRCC5 signaling with Quercetin may help physicians to develop a novel RT to better suppress the progression of PCa.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02287-4.

CircRNAs in Tumor Radioresistance

Circular RNAs (circRNAs) are endogenous, non-coding RNAs, which are derived from host genes that are present in several species and can be involved in the progression of various diseases. circRNAs’ leading role is to act as RNA sponges. In recent years, the other roles of circRNAs have been discovered, such as regulating transcription and translation, regulating host genes, and even being translated into proteins. As some tumor cells are no longer radiosensitive, tumor radioresistance has since become a challenge in treating tumors. In recent years, circRNAs are differentially expressed in tumor cells and can be used as biological markers of tumors. In addition, circRNAs can regulate the radiosensitivity of tumors. Here, we list the mechanisms of circRNAs in glioma, nasopharyngeal carcinoma, and non-small cell lung cancer; further, these studies also provide new ideas for the purposes of eliminating radioresistance in tumors.

Mechanism and Function of Circular RNA in Regulating Solid Tumor Radiosensitivity

Radiotherapy is an important tool in the treatment of malignant tumors, and exploring how to make radiotherapy more effective is a new way to break through the current bottleneck in the development of radiation oncology. Circular RNAs (circRNAs) are a special class of endogenous non-coding RNAs. Numerous studies have shown that circRNAs have shown great potential in regulating the biological functions of tumors, including proliferation, migration, invasion, and treatment resistance, and that differences in their expression levels are closely related to the clinical prognosis of tumor patients. This review systematically compares the mechanisms of circRNAs in the process of tumor development and radiosensitivity and provides insight into the clinical translation of circRNAs in radiotherapy.

Investigation into Chronic Low-Dose Ionizing Radiation Effect on Gene Expression Profile of Human HUVECs Cells

Introduction: Understanding the molecular mechanism of chronic low-dose ionizing radiation (LDIR) effects on the human body is the subject of many research studies. Several aspects of cell function such as cell proliferation, apoptosis, inflammation, and tumorigenesis are affected by LDIR. Detection of the main biological process that is targeted by LIDR via network analysis is the main aim of this study. Methods: GSE66720 consisting of gene expression profiles of human umbilical vein endothelial cells (HUVECs) (a suitable cell line to be investigated), including irradiated and control cells, was downloaded from Gene Expression Omnibus (GEO). The significant differentially expressed genes (DEGs) were determined and analyzed via protein-protein interaction (PPI) network analysis to find the central individuals. The main cell function which was related to the central nodes was introduced. Results: Among 64 queried DEGs, 48 genes were recognized by the STRING database. C-X-C motif chemokine ligand 8 (CXCL8), intercellular adhesion molecule 1 (ICAM1), Melanoma growth-stimulatory activity/growth-regulated protein α (CXCL1), vascular cell adhesion molecule 1 (VCAM-1), and nerve growth factor (NGF) were introduced as hub nodes. Conclusion: Findings indicate that inflammation is the main initial target of LDIR at the cellular level which is associated with alteration in the other essential functions of the irradiated cells.

Metadata analysis to explore hub of the hub-genes highlighting their functions, pathways and regulators for cervical cancer diagnosis and therapies

Cervical cancer (CC) is considered as the fourth most common women cancer globally.that shows malignant features of local infiltration and invasion into adjacent organs and tissues. There are several individual studies in the literature that explored CC-causing hub-genes (HubGs), however, we observed that their results are not so consistent. Therefore, the main objective of this study was to explore hub of the HubGs (hHubGs) that might be more representative CC-causing HubGs compare to the single study based HubGs. We reviewed 52 published articles and found 255 HubGs/studied-genes in total. Among them, we selected 10 HubGs (CDK1, CDK2, CHEK1, MKI67, TOP2A, BRCA1, PLK1, CCNA2, CCNB1, TYMS) as the hHubGs by the protein-protein interaction (PPI) network analysis. Then, we validated their differential expression patterns between CC and control samples through the GPEA database. The enrichment analysis of HubGs revealed some crucial CC-causing biological processes (BPs), molecular functions (MFs) and cellular components (CCs) by involving hHubGs. The gene regulatory network (GRN) analysis identified four TFs proteins and three miRNAs as the key transcriptional and post-transcriptional regulators of hHubGs. Then, we identified hHubGs-guided top-ranked FDA-approved 10 candidate drugs and validated them against the state-of-the-arts independent receptors by molecular docking analysis. Finally, we investigated the binding stability of the top-ranked three candidate drugs (Docetaxel, Temsirolimus, Paclitaxel) by using 100 ns MD-based MM-PBSA simulations and observed their stable performance. Therefore the finding of this study might be the useful resources for CC diagnosis and therapies.

Effect of circPUM1 on radioresistance of cervical cancer cells through targeting miR-144-3p

OBJECTIVE

To investigate the effect of circular RNA pumilio RNA binding family member (circPUM) 1 on radioresistance of cervical cancer cells and its mechanism.

METHODS

Cancer tissue and corresponding paricancerous tissue samples were collected from 47 patients with cervical cancer who underwent surgical treatment in the Second Affiliated Hospital of Zhengzhou University from August 2019 to February 2020. The expression levels of circPUM1 and miR-144-3p in cervical cancer tissues and paricancerous tissues were detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The Pearson method was used to analyze the correlation between circPUM1 and miR-144-3p expression in cervical cancer tissues. circPUM1 lentiviral short hairpin RNA (sh-circPUM1) and its negative control (sh-NC), miR-144-3p oligonucleotide mimic (miR-144-3p mimic) and its negative control (miR-NC), sh-circPUM1 and miR-144-3p inhibitor (anti-miR), and sh-circPUM1 and anti-miR negative control (anti-miR-NC) were transfected into human cervical carcinoma SiHa cells, respectively, and the cells were irradiated with 0 and 4 Gy irradiation doses. Cell proliferation, colony formation, apoptosis, migration and invasion were detected by cell counting kit (CCK-8 method), plate colony formation assay, flow cytometry and Transwell assay, respectively. The protein expression of cleaved-caspase3 was detected by Western blotting. The targeting relationship between circPUM1 and miR-144-3p was analyzed with Starbase platform.

RESULTS

Compared with adjacent tissue, the expression of circPUM1 in cervical cancer tissue was significantly increased ( P<0.05), while the expression of miR-144-3p was decreased ( P<0.05). The circPUM1 was negatively correlated with miR-144-3p ( r=-0.9282, P<0.01). After transfection with sh-circPUM1 or miR-144-3p mimic, the inhibition rate of cell proliferation, the rate of apoptosis and the expression level of cleaved-caspase3 protein increased (all P<0.05), while the number of colonies formed, migrated and invaded cells decreased (all P<0.05). CircPUM1 could targeted to miR-144-3p. After co-transfection of sh-circPUM1 and anti-miR, the inhibition rate of cell proliferation, the rate of apoptosis and the expression level of cleaved-caspase3 protein significantly decreased (all P<0.05), while the number of colonies formed, migrated and invaded cells increased (all P<0.05).

CONCLUSION

Silencing circPUM1 may inhibit the proliferation, colony formation, migration, invasion and induce apoptosis of cervical cancer cells through targeting and regulating the expression of miR-144-3p.

CircRNAs in Malignant Tumor Radiation: The New Frontier as Radiotherapy Biomarkers

World Health Organization (WHO) data show that of the top 20 factors that threaten human life and health, cancer is at the forefront, and the therapeutic approaches for cancer consist of surgery, radiotherapy, chemotherapy and immunotherapy. For most highly metastatic and recurrent cancer, radiation therapy is an essential modality to mitigate tumor burden and improve patient survival. Despite the great accomplishments that have been made in clinical therapy, an inevitable challenge in effective treatment is radioresistance, the mechanisms of which have not yet been completely elucidated. In addition, radiosensitization methods based on molecular mechanisms and targets, and clinical applications are still inadequate. Evidence indicates that circular RNAs (circRNAs) are important components in altering tumor progression, and in influencing resistance and susceptibility to radiotherapy. This review summarizes the reasons for tumor radiotherapy resistance induced by circRNAs, and clarifies the molecular mechanisms and targets of action. Moreover, we determine the potential value of circRNAs as clinical indicators in radiotherapy, providing a theoretical basis for circRNAs-based strategies for cancer radiotherapy.

Bioinformatics Screening of Potential Biomarkers from mRNA Expression Profiles to Discover Drug Targets and Agents for Cervical Cancer

Bioinformatics analysis has been playing a vital role in identifying potential genomic biomarkers more accurately from an enormous number of candidates by reducing time and cost compared to the wet-lab-based experimental procedures for disease diagnosis, prognosis, and therapies. Cervical cancer (CC) is one of the most malignant diseases seen in women worldwide. This study aimed at identifying potential key genes (KGs), highlighting their functions, signaling pathways, and candidate drugs for CC diagnosis and targeting therapies. Four publicly available microarray datasets of CC were analyzed for identifying differentially expressed genes (DEGs) by the LIMMA approach through GEO2R online tool. We identified 116 common DEGs (cDEGs) that were utilized to identify seven KGs (AURKA, BRCA1, CCNB1, CDK1, MCM2, NCAPG2, and TOP2A) by the protein–protein interaction (PPI) network analysis. The GO functional and KEGG pathway enrichment analyses of KGs revealed some important functions and signaling pathways that were significantly associated with CC infections. The interaction network analysis identified four TFs proteins and two miRNAs as the key transcriptional and post-transcriptional regulators of KGs. Considering seven KGs-based proteins, four key TFs proteins, and already published top-ranked seven KGs-based proteins (where five KGs were common with our proposed seven KGs) as drug target receptors, we performed their docking analysis with the 80 meta-drug agents that were already published by different reputed journals as CC drugs. We found Paclitaxel, Vinorelbine, Vincristine, Docetaxel, Everolimus, Temsirolimus, and Cabazitaxel as the top-ranked seven candidate drugs. Finally, we investigated the binding stability of the top-ranked three drugs (Paclitaxel, Vincristine, Vinorelbine) by using 100 ns MD-based MM-PBSA simulations with the three top-ranked proposed receptors (AURKA, CDK1, TOP2A) and observed their stable performance. Therefore, the proposed drugs might play a vital role in the treatment against CC.

The emerging roles of circRNAs in cancer and oncology

Over the past decade, circular RNAs (circRNAs) have emerged as a large class of primarily non-coding RNA molecules, many of which have key roles in cancer development and progression through diverse mechanisms of action. CircRNAs often have tissue-restricted and cancer-specific expression patterns, and accumulating data suggest that these molecules are of potential clinical relevance and utility. In particular, circRNAs have strong potential as diagnostic, prognostic and predictive biomarkers, which is underscored by their detectability in liquid biopsy samples such as in plasma, saliva and urine. However, technical issues in the detection and assessment of circRNAs as well as biological knowledge gaps need to be addressed to move this relatively young field of research forward and bring circRNAs to the forefront of clinical practice. Herein, we review the current knowledge regarding circRNA biogenesis, regulation and functions in cancer as well as their clinical potential as biomarkers, therapeutic agents and drug targets.

Circ_0008500 Knockdown Improves Radiosensitivity and Inhibits Tumorigenesis in Breast Cancer Through the miR-758-3p/PFN2 Axis

Breast cancer is one of the most common malignancies worldwide. Circular RNAs (CircRNAs) were revealed to be implicated in the development of breast cancer. In this research, we aimed to investigate the role and underlying mechanism of circ_0008500 in the development and radiosensitivity of breast cancer. Using real-time quantitative PCR (RT-qPCR) and western blot, we found that hsa_circ_0008500 (circ_0008500) and profilin 2 (PFN2) were increased, while microRNA-758-3p (miR-758-3p) was decreased in breast cancer tissues and cells. Cell viability, the number of colonies, proliferation and apoptosis were detected using CCK-8, colony formation, EdU assays and flow cytometry, respectively. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were devoted to test the interaction between miR-758-3p and circ_0008500 or PFN2. The results showed that circ_0008500 knockdown inhibited cell growth, and facilitated cell apoptosis and radiosensitivity in breast cancer cells in vitro. Moreover, circ_0008500 regulated PFN2 expression by sponging miR-758-3p. Functionally, circ_0008500 knockdown regulated cell behaviors and radiosensitivity by targeting miR-758-3p to downregulate PFN2 expression in vitro. Additionally, in vivo tumor formation assay and immunohistochemistry (IHC) assay demonstrated that circ_0008500 knockdown enhanced the radiosensitivity and repressed tumor growth in vivo. In conclusion, circ_0008500 inhibition promoted the radiosensitivity and restrained the development of breast cancer by downregulating PFN2 expression via targeting miR-758-3p.

CircNEIL3 mediates pyroptosis to influence lung adenocarcinoma radiotherapy by upregulating PIF1 through miR-1184 inhibition

Circular RNAs (circRNAs) belong to an abundant category of non-coding RNAs that are stable and specific, and thus have great potential in cancer treatment. However, little is known about the role of circRNAs during radiotherapy in lung adenocarcinoma (LUAD). Here, we established the expression profiles of 1,875 dysregulated circRNAs in non-irradiated and irradiated A549 cells and identified circNEIL3 as a significantly downregulated circRNA in A549 cells treated with 0, 2, or 4 Gy of radiation, respectively. Functional assays demonstrated that circNEIL3 knockdown promoted radiation-induced cell pyroptosis, whereas circNEIL3 overexpression had the opposite effects. Importantly, the effects of circNEIL3 overexpression on inhibiting pyroptosis were reversed by PIF1 knockdown. Mechanistically, circNEIL3-mediated pyroptosis was achieved through directly binding to miR-1184 as a sponge, thereby releasing the inhibition of miR-1184 on PIF1, which ultimately induces DNA damage and triggers AIM2 inflammasome activation. In vivo, circNEIL3 knockdown significantly enhanced the efficacy of radiotherapy as evidenced by decreases in tumor volume and weight. Collectively, the circNEIL3/miR-1184/PIF1 axis that mediate pyroptosis induction may be a novel, promising therapeutic strategy for the clinical treatment of lung cancer.

MicroRNA-217: a therapeutic and diagnostic tumor marker

INTRODUCTION

Cancer as one of the most common causes of death has always been one of the major health challenges globally. Since, the identification of tumors in the early tumor stages can significantly reduce mortality rates; it is required to introduce novel early detection tumor markers. MicroRNAs (miRNAs) have pivotal roles in regulation of cell proliferation, migration, apoptosis, and tumor progression. Moreover, due to the higher stability of miRNAs than mRNAs in body fluids, they can be considered as non-invasive diagnostic or prognostic markers in cancer patients.

AREAS COVERED

In the present review we have summarized the role of miR-217 during tumor progressions. The miR-217 functions were categorized based on its target molecular mechanisms and signaling pathways.

EXPERT OPINION

It was observed that miR-217 mainly exerts its function by regulation of the transcription factors during tumor progressions. The WNT, MAPK, and PI3K/AKT signaling pathways were also important molecular targets of miR-217 in different cancers. The present review clarifies the molecular biology of miR-217 and paves the way of introducing miR-217 as a non-invasive diagnostic marker and therapeutic target in cancer therapy.

GADD45B induced the enhancing of cell viability and proliferation in radiotherapy and increased the radioresistance of HONE1 cells

This study aimed to investigate the key role and mechanism of GADD45B in the radiation resistance of nasopharyngeal carcinoma (NPC) cell lines. Radiotherapy-resistant HONE1 (HONE1-R) cells with stable genetic radioresistance were cultured under continuous radiation stimulation. CCK-8 and clone formation assays were used to verify the radioresistance of the cell line. Transcriptome sequencing was used to identify the most important differential signaling pathway in the cell line. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analysis were used to verify the sequencing results. GADD45B-siRNA was used to knock down the key gene so as to verify the downstream gene expression and analyze its mechanism. The transcriptome analysis showed that 702 genes were upregulated and 772 genes were downregulated in the HONE1-R cell lines. The core differential signaling pathway was mitogen-activated protein kinase (MAPK) signaling pathway, and the core differential gene was GADD45B. After GADD45B was knocked down, the cell viability and proliferation ability of HONE1-R cell lines significantly decreased under radiation, and the expression of cyclin B1 and p-CDK1 decreased significantly. MAPK is the core signaling pathway in radioresistance of NPC. GADD45B plays an important role by affecting cell viability and proliferation in NPC radioresistance. GADD45B is a potential target of radioresistance in NPC.

[Research Progress in CircRNA and Radiotherapy Resistance of Non-small Cell Lung Cancer]

As the main type of lung cancer, non-small cell lung cancer (NSCLC) is a common cancer which is characterized by low 5-year survival rate and worse prognosis. Nowadays, some studies show that the low survival rate and worse prognosis are due to the resistance to radiotherapy caused by circRNA. Therefore, to find out the relationship between circRNA and radiotherapy resistance of NSCLC was imoprtant. According to research the relevant literatures, the relationship between circRNA and radiotherapy resistance of NSCLC was explored. CircRNA plays an important role in the invasion, metastasis, proliferation and treatment resistance of NSCLC. The radiation resistance of tumor cells induced by circRNA has become a crucial problem in radiotherapy. CircRNA plays an important role in the radiotherapy resistance of NSCLC.
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Hsa_circ_0000520 overexpression increases CDK2 expression via miR-1296 to facilitate cervical cancer cell proliferation

Background

Circular RNA (circRNA) has been demonstrated to participate in cervical cancer development. In this study, we analyzed the role of hsa_circ_0000520 in cervical cancer.

Methods

Fifty-two pairs of cervical cancer and adjacent normal tissue samples were collected, and five human cervical cancer cell lines were obtained followed by the detection of hsa_circ_0000520 expression. Nuclear-cytoplasmic isolation and fluorescence in situ hybridization were performed to analyze the subcellular localization of hsa_circ_0000520 while linear RNA was digested by RNase R. Gain- or loss-of function experiments on hsa_circ_0000520 were performed, followed by detection of cell proliferation and cell cycle by EdU, Cell Counting Kit-8, colony formation assay, and flow cytometry respectively.

Results

Hsa_circ_0000520 and cyclin-dependent kinase 2 (CDK2) were highly expressed in cervical cancer tissues. Binding sites between microRNA-1296 (miR-1296) and hsa_circ_0000520 or CDK2 were verified. Antibody to Argonaute 2 (Ago2) could precipitate hsa_circ_0000520, indicating that hsa_circ_0000520 could competitively bind to miR-1296 via Ago2. Silencing hsa_circ_0000520 inhibited cervical cancer cell proliferation and promoted the inhibitory effects of miR-1296 on CDK2, thereby blocking cell cycle progression and promoting apoptosis.

Conclusion

These results support the premise that targeting hsa_circ_0000520 can be a potential approach to combat cervical cancer.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02953-9.

Radio-Susceptibility of Nasopharyngeal Carcinoma: Focus on Epstein- Barr Virus, MicroRNAs, Long Non-Coding RNAs and Circular RNAs

Nasopharyngeal carcinoma (NPC) is a type of head and neck cancer. As a neoplastic disorder, NPC is a highly malignant squamous cell carcinoma that is derived from the nasopharyngeal epithelium. NPC is radiosensitive; radiotherapy or radiotherapy combining with chemotherapy are the main treatment strategies. However, both modalities are usually accompanied by complications and acquired resistance to radiotherapy is a significant impediment to effective NPC therapy. Therefore, there is an urgent need to discover effective radio-sensitization and radio-resistance biomarkers for NPC. Recent studies have shown that Epstein-Barr virus (EBV)-encoded products, microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), which share several common signaling pathways, can function in radio-related NPC cells or tissues. Understanding these interconnected regulatory networks will reveal the details of NPC radiation sensitivity and resistance. In this review, we discuss and summarize the specific molecular mechanisms of NPC radio-sensitization and radio-resistance, focusing on EBV-encoded products, miRNAs, lncRNAs and circRNAs. This will provide a foundation for the discovery of more accurate, effective and specific markers related to NPC radiotherapy. EBVencoded products, miRNAs, lncRNAs and circRNAs have emerged as crucial molecules mediating the radio-susceptibility of NPC. This understanding will improve the clinical application of markers and inform the development of novel therapeutics for NPC.

Silencing of hsa_circ_0009035 Suppresses Cervical Cancer Progression and Enhances Radiosensitivity through MicroRNA 889-3p-Dependent Regulation of HOXB7

Circular RNAs (circRNAs), a novel type of endogenous noncoding RNAs, have been identified as critical regulators in human carcinogenesis. Here, we investigated the precise actions of hsa_circ_0009035 in the progression and radioresistance of cervical cancer (CC). The levels of hsa_circ_0009035, microRNA 889-3p (miR-889-3p), and homeobox B7 (HOXB7) were detected by quantitative real-time PCR (qRT-PCR) or Western blotting. RNase R and actinomycin D assays were used to assess the stability of hsa_circ_0009035. Cell proliferation, cell cycle progression, apoptosis, migration, and invasion were gauged with Cell Counting Kit-8 (CCK-8), flow cytometry, and transwell assays. Cell colony formation and survival were determined by the colony formation assay. Targeted correlations among hsa_circ_0009035, miR-889-3p, and HOXB7 were examined by the dual-luciferase reporter, RNA immunoprecipitation (RIP), or RNA pulldown assay. Animal studies were performed to evaluate the impact of hsa_circ_0009035 on tumor growth. We found that hsa_circ_0009035 was highly expressed in CC tissues and cells, and it was associated with the radioresistance of CC patients. Moreover, the silencing of hsa_circ_0009035 inhibited CC cell proliferation, migration, invasion, and it enhanced apoptosis and radiosensitivity in vitro and weakened tumor growth in vivo. Mechanistically, hsa_circ_0009035 directly targeted miR-889-3p by binding to miR-889-3p, and hsa_circ_0009035 modulated HOXB7 expression through miR-889-3p. HOXB7 was a functional target of miR-889-3p in regulating CC progression and radioresistance in vitro, and hsa_circ_0009035 modulated CC progression and radioresistance in vitro by miR-889-3p. Our current study first identified hsa_circ_0009035 as an important regulator of CC progression and radioresistance at least in part through targeting the miR-889-3p/HOXB7 axis, highlighting its significance as a potential therapeutic target for CC treatment.

CircZNF208 enhances the sensitivity to X-rays instead of carbon-ions through the miR-7-5p /SNCA signal axis in non-small-cell lung cancer cells

BACKGROUND

Mounting evidence suggests that circular RNAs (circRNAs) are closely related to the regulation of gene expression during tumour development. However, the role of circRNAs in modulating the radiosensitivity of non-small cell lung cancer (NSCLC) cells has not been explored.

METHODS

Transcriptome sequencing was used to explore the expression profiles of circRNAs in NSCLC. The expression level of circRNAs was changed by inducing instantaneous knockdown or overexpression. Changes in proliferation and radiosensitivity of NSCLC cells were investigated using CCK-8, EDU, and clonal survivals.

RESULTS

By analysing the circRNA expression profile of NSCLC cells, we found that circRNA ZNF208 (circZNF208) was significantly upregulated in a radioresistant NSCLC cell line (A549-R11), which was acquired from the parental NSCLC cell line A549. Knockout experiments indicated that circZNF208 enhanced the radiosensitivity of A549 and A549-R11 cells to X-rays. Mechanistically, circZNF208 upregulated SNCA expression by acting as a sponge of miR-7-5p and subsequently promoted the resistance of NSCLC cells to low linear energy transfer (LET) X-rays. However, this effect was not observed in NSCLC cells exposed to high-LET carbon ions.

CONCLUSIONS

Knockdown of circZNF208 altered the radiosensitivity of patients with NSCLC to X-rays but did not significantly change the sensitivity to carbon ions. Therefore, circZNF208 might serve as a potential biomarker and therapeutic target for NSCLC treatment with radiotherapy of different modalities.

Circ_0055625 knockdown inhibits tumorigenesis and improves radiosensitivity by regulating miR-338-3p/MSI1 axis in colon cancer

BACKGROUND

Radiotherapy is a main therapeutic method for cancers, including colon cancer. In the current study, we aim to explore the effects of circular RNA (circRNA) circ_0055625 in the progression and radiosensitivity of colon cancer and the underlying mechanism.

METHODS

The expression of circ_0055625 and musashi homolog 1 (MSI1) mRNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). MSI1 protein expression was determined by Western blot. Cell proliferation was assessed by cell counting kit-8 (CCK-8) and colony formation assays. Cell survival fraction, apoptosis, and invasion were investigated by colony formation assay, flow cytometry analysis, and transwell invasion assay, respectively. Cell migration was detected by wound-healing and transwell migration assays. The binding relationship between microRNA-338-3p (miR-338-3p) and circ_0055625 or MSI1 was predicted by online databases and identified by Dual-Luciferase Reporter Assay. The effects of circ_0055625 silencing on the tumor formation and radiosensitivity of colon cancer in vivo were explored by in vivo tumor formation assay.

RESULTS

Circ_0055625 and MSI1 were upregulated in colon cancer tissues and cells relative to control groups. Radiation treatment apparently increased the expression of circ_0055625 and MSI1 in colon cancer cells. Circ_0055625 knockdown or MSI1 silencing repressed cell proliferation, migration, and invasion and promoted cell apoptosis and radiosensitivity in colon cancer. Also, circ_0055625 silencing-mediated effects were attenuated by MSI1 overexpression. Additionally, circ_0055625 silencing reduced MSI1 expression, which could be attenuated by miR-338-3p inhibitor. Mechanically, circ_0055625 acted as a sponge for miR-338-3p to regulate MSI1. Furthermore, circ_0055625 knockdown hindered tumor growth and improved radiosensitivity in vivo.

CONCLUSION

Circ_0055625 repression inhibited the progression and radioresistance of colon cancer by downregulating MSI1 through sponging miR-338-3p. This result might provide a theoretical basis for improving the therapy of colon cancer with radiation.

The Potential of circRNA as a Novel Diagnostic Biomarker in Cervical Cancer

Cervical cancer is the fourth most common cancer among females worldwide. In spite of advances in detection and treatment, it is still one of the most dangerous gynecological malignancies in the world, especially in developing countries, and seriously threatens human health. Circular RNA (circRNA) is a special new type of endogenous noncoding RNA discovered recently. They form a covalently closed continuous loop and are specifically expressed in the eukaryotic transcriptome. With further understanding of circular RNA, a large number of studies have determined the key regulatory role of circRNA in a variety of diseases, especially cancer (including cervical cancer, liver cancer, and lung cancer). In addition, it has also been found that the abnormal expression of circRNA is related to its pathological characteristics in cervical cancer tissue, which can be used as a potential indicator for early screening and diagnosis of cervical cancer, targeted therapy, and prognosis prediction. This article summarizes the recent research achievements of circRNAs in cervical cancer. We briefly described the abnormal expression of circRNA in cervical cancer and discussed the involvement of circRNA in the occurrence process of cervical cancer by regulating cell proliferation, migration, invasion, and apoptosis. We believe that circRNA has potential value as a biomarker in the diagnosis and prognosis of cervical cancer.

Investigating the Underlying Mechanisms of Circular RNAs and Their Application in Clinical Research of Cervical Cancer

Circular RNAs (circRNAs) are non-coding RNA molecules, and these are differentially expressed in various diseases, including cancer, suggesting that circRNAs can regulate certain diseases. CircRNAs can act as miRNAs sponges, RNA-binding protein (RBP) sponges, and translation regulators, and they can become an important part of the regulation of gene expression. Furthermore, because of their biomedical features in body fluids, such as high abundance, conservation, and stability, circRNAs are seen as potential biomarkers for various cancers. Cervical cancer (CC) is one of the main causes of cancer-related death in women, and there have been a large number of studies that analyze circRNAs as a new object to be evaluated in CC. Therefore, this review, by understanding the role of circRNAs in CC, may create innovative strategies in the future clinical diagnosis, treatment, and prognosis of CC and promote the development of personalized and highly accurate cancer therapy.

Emerging role of non-coding RNAs in response of cancer cells to radiotherapy

Radiotherapy is an effective method for treatment of a large proportion of human cancers. Yet, the efficacy of this method is precluded by the induction of radioresistance in tumor cells and the radiation-associated injury of normal cells surrounding the field of radiation. These restrictions necessitate the introduction of modalities for either radiosensitization of cancer cells or protection of normal cells against adverse effects of radiation. Non-coding RNAs (ncRNAs) have essential roles in the determination of radiosensitivity. Moreover, ncRNAs can modulate radiation-induced side effects in normal cells. Several microRNAs (miRNAs) such as miR-620, miR-21 and miR-96-5p confer radioresistance, while other miRNAs including miR-340/ 429 confer radiosensitivity. The expression levels of a number of miRNAs are associated with radiation-induced complications such as lung fibrosis or oral mucositis. The expression patterns of several long non-coding RNAs (lncRNAs) such as MALAT1, LINC00630, HOTAIR, UCA1 and TINCR are associated with response to radiotherapy. Taken together, lncRNAs and miRNAs contribute both in modulation of response of cancer cells to radiotherapy and in protection of normal cells from the associated side effects. The current review provides an overview of the roles of these transcripts in these aspects.

Identification and Bioinformatic Assessment of circRNA Expression After RMI1 Knockdown and Ionizing Radiation Exposure

RecQ-mediated genome instability protein 1 (RMI1) is an important component of the BLM-Topo IIIα-RMI1-RMI2 complex and plays a critical role in maintaining genome stability. However, the cellular functions of RMI1 in response to ionizing radiation (IR) are poorly understood. In this study, we found that RMI1 knockdown led to enhanced radiosensitivity and apoptosis after irradiation. To analyze the effect of RMI1 knockdown on the expression of circular RNAs (circRNAs), we performed high-throughput RNA sequencing on four groups of human embryonic kidney (HEK) 293T cells: control cells and RMI1 knockdown cells with or without IR exposure. A total of 179 and 160 differentially expressed circRNAs (DE-circRNAs) were identified under RMI1 knockdown without and with exposure to IR, respectively. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that these DE-circRNAs were involved in a variety of functions and signal pathways, including histone H3-K36 methylation, nuclear pore organization, mRNA destabilization, the mismatch repair pathway, and the apoptotic signaling pathway. Overall, our results indicate that RMI1 plays a crucial role in the response to IR and, more generally, that circRNAs are important in the regulatory mechanism of the radiation response.

Integrated analysis of circRNA-miRNA-mRNA network reveals potential prognostic biomarkers for radiotherapies with X-rays and carbon ions in non-small cell lung cancer

Background

This work was aimed at exploring the regulatory network of non-coding RNA (ncRNA) especially circular RNA (circRNA) and microRNA (miRNA), in the sensitivity of non-small cell lung cancer (NSCLC) cells to low linear energy transfer (LET) X-ray and high-LET carbon ion irradiations.

Methods

The radioresistant NSCLC cell line A549-R11 was obtained from its parental cell line A549 through irradiation with X-rays of 2.0 Gy per fraction for 30 times. The sensitivities of A549, A549-R11 and H1299 cells exposed to X-rays and carbon ions were verified using the colony formation assay. A comprehensive circRNA-miRNA-mRNA network was constructed through the sequencing data in parental A549, acquired radioresistant A549-R11 and intrinsic radioresistant H1299 cells, and the network was further optimized according to the prognostic results from the TCGA and GEO databases.

Results

Based on high-throughput sequencing of circRNAs, we found that 40 circRNAs were up-regulated while 184 circRNAs were down-regulated in the intersection of the sets of A549-R11 and H1299 cells. Subsequently, a circRNA- miRNA-mRNA network, including 14 interactive pairs and 8 circRNAs, 4 overall survival-associated miRNAs, and 4 mRNAs, was constructed through the high-throughput data screening and bioinformatics methods.

Conclusions

Our results provide a complete understanding to the regulatory mechanism of the sensitivities to low-LET X-ray and high-LET carbon ion irradiations, and might be helpful to screen potential biomarkers for predicting the Carbon-ion radiotherapy (CIRT) and X-ray radiotherapy responses in NSCLC.

The Potential of Circular RNAs as Cancer Biomarkers

Circular RNA (circRNA) is a covalently closed RNA structure that has several proposed functions related to cancer development. Recently, cancer-specific and tissue-specific circRNAs have been identified by high-throughput sequencing and are curated in publicly available databases. CircRNAs have features that are ideal properties of biomarkers, including conservation, abundance, and stability in plasma, saliva, and urine. Many circRNAs with predictive and prognostic significance in cancer have been described, and functional mechanisms for some circRNAs have been suggested. CircRNA also has great potential as a noninvasive biomarker for early cancer detection, although further investigation is necessary before clinical application is feasible.See all articles in this CEBP Focus section, "NCI Early Detection Research Network: Making Cancer Detection Possible."

Circular RNA PRKCI silencing represses esophageal cancer progression and elevates cell radiosensitivity through regulating the miR-186-5p/PARP9 axis

AIMS

Circular RNA PRKCI (circPRKCI) and poly ADP-ribose polymerase 9 (PARP9) are related to the development of cancers. In this study, we aimed to explore the regulatory mechanisms between circPRKCI and PARP9 in EC progression and radioresistance.

MATERIALS AND METHODS

The levels of circPRKCI, PARP9 mRNA, and miR-186-5p were assessed by quantitative real time polymerase chain reaction (qRT-PCR). Western blot analysis was employed to examine the levels of several proteins. The viability, colony formation, cell cycle progression, and apoptosis of EC cells were determined with CCK-8, colony formation, or flow cytometry assays. The relationship between circPRKCI or PARP9 and miR-186-5p was verified with the dual-luciferase reporter and RIP assays.

KEY FINDINGS

We observed that circPRKCI and PARP9 were upregulated while miR-186-5p was downregulated in EC tissues and cells. Furthermore, circPRKCI knockdown decreased tumor growth in vivo and constrained cell viability, colony formation, cell cycle progression, elevated cell radiosensitivity in EC cells in vitro. Importantly, circPRKCI modulated PARP9 expression through sponging miR-186-5p. Besides, PARP9 overexpression overturned circPRKCI silencing-mediated effects on the viability, colony formation, cell cycle progression, and radiosensitivity of EC cells.

SIGNIFICANCE

CircPRKCI regulated cell malignancy and radioresistance through modulating the miR-186-5p /PARP9 axis in EC, which provided a might target for EC treatment.

Serum exosomal microRNA-766-3p expression is associated with poor prognosis of esophageal squamous cell carcinoma

The aim was to analyze the association between exosomal microRNA (miR)‐766‐3p expression levels in serum and the prognosis of esophageal squamous cell carcinoma (ESCC). The serum global exosomal miRNA expression of ESCC patients was measured by microRNA microarray. Quantitative real‐time PCR was used to analyze the expression levels of candidate miRNAs in both serum and tissues from ESCC patients. Wilcoxon tests were applied to evaluate clinical characteristics and their association with serum levels of exosomal miR‐766‐3p. A Cox regression model was used to identify prognostic factors. The effects of miR‐766‐3p expression on cell migration and invasion were examined using Transwell assays, and CCK‐8 assays were carried out to measure cell proliferation. The TNM stage was associated with high serum exosomal miR‐766‐3p levels of ESCC patients (P = .030). Higher serum exosomal miR‐766‐3p expression levels were associated with poor prognosis (for overall survival, hazard ratio [HR] [95% confidence interval (CI)], 2.21 [1.00, 4.87]; for disease‐free survival, HR [95% CI], 2.15 [1.01, 4.59]). However, we found no association between the expression of miR‐766‐3p in tissue and ESCC prognosis. In vitro results showed that miR‐766‐3p promotes cell migration and invasion, but not cell proliferation. By using dual‐luciferase reporter assay, HOXA13 was confirmed as a direct target gene of miR‐766‐3p. The ESCC patients with highly expressed serum exosomal miR‐766‐3p had a significantly worse survival. Therefore, serum exosomal miR‐766‐3p could serve as a prognostic marker for the assessment of ESCC.

Targeting the radiation-induced TR4 nuclear receptor-mediated QKI/circZEB1/miR-141-3p/ZEB1 signaling increases prostate cancer radiosensitivity

Early studies indicated that the testicular nuclear receptor 4 (TR4) might play key roles in altering prostate cancer (PCa) progression; however, its ability to alter PCa radiosensitivity remains unclear. Here, we found that suppressing TR4 expression promoted radiosensitivity and better suppressed PCa by modulating the protein quaking (QKI)/circZEB1/miR-141-3p/ZEB1 signaling pathway. Mechanism dissection studies revealed that TR4 could transcriptionally increase the RNA-binding protein QKI to increase circZEB1 levels, which then sponges the miR-141-3p to increase the expression of its host gene ZEB1. Preclinical studies with an in vivo mouse model further proved that combining radiation therapy (RT) with metformin promoted radiosensitivity to suppress PCa progression. Together, these results suggest that TR4 may play key roles in altering PCa radiosensitivity and show that targeting this newly identified TR4-mediated QKI/circZEB1/miR-141-3p/ZEB1 signaling pathway may help in the development of a novel RT to better suppress the progression of PCa.

Circ_0000745 Promotes the Progression of Cervical Cancer by Regulating miR-409-3p/ATF1 Axis

Background: Cervical cancer (CC) is a common gynecological malignancy with a high risk of recurrence and death. Circular RNAs play a crucial role in the occurrence and development of tumors. This study aimed to investigate the function and mechanism of circ_0000745 in CC. Methods: The levels of circ_0000745, miR-409-3p, and activating transcription factor 1 (ATF1) were determined by quantitative real-time polymerase chain reaction or western blot assay. Cell proliferation was assessed by colony formation assay. Cell migration and invasion were evaluated by transwell assay. Glycolysis was analyzed by measuring extracellular acidification rate, glucose uptake, and lactate production. Also, the protein levels of glucose transporter 1 and lactate dehydrogenase A were detected using western blot. The relationship among circ_0000745, miR-409-3p, and ATF1 were confirmed by dual-luciferase reporter assay. Moreover, xenograft assay was performed to analyze tumor growth in vivo. Results: Circ_0000745 and ATF1 were upregulated, whereas miR-409-3p was downregulated in CC tissues and cells. Knockdown of circ_0000745 repressed proliferation, migration, invasion, and glycolysis of CC cells. Circ_0000745 regulated CC progression by targeting miR-409-3p. Circ_0000745 modulated ATF1 expression through sponging miR-409-3p. MiR-409-3p hindered CC progression by targeting ATF1. Furthermore, depletion of circ_0000745 impeded tumor growth in vivo. Conclusion: Circ_0000745 promoted the progression of CC through modulating miR-409-3p/ATF1 axis, indicating a promising biomarker for CC therapy.

Non-Coding RNAs in Cancer Radiosensitivity: MicroRNAs and lncRNAs as Regulators of Radiation-Induced Signaling Pathways

Radiotherapy is a cancer treatment that applies high doses of ionizing radiation to induce cell death, mainly by triggering DNA double-strand breaks. The outcome of radiotherapy greatly depends on radiosensitivity of cancer cells, which is determined by multiple proteins and cellular processes. In this review, we summarize current knowledge on the role of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in determining the response to radiation. Non-coding RNAs modulate ionizing radiation response by targeting key signaling pathways, including DNA damage repair, apoptosis, glycolysis, cell cycle arrest, and autophagy. Additionally, we indicate miRNAs and lncRNAs that upon overexpression or inhibition alter cellular radiosensitivity. Current data indicate the potential of using specific non-coding RNAs as modulators of cellular radiosensitivity to improve outcome of radiotherapy.

The Regulatory Role of circRNA_101308 in Cervical Cancer and the Prediction of Its Mechanism

Purpose

Accumulating evidence indicates that circular RNAs (circRNAs) are closely involved in canceration and cancer progression. However, the role of circRNAs in cervical cancer (CC) is largely unknown. Here, we characterized the role of circRNA_101308 in CC.

Materials and Methods

The expression of circRNA_101308 in CC tissues was measured by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Then, circRNA_101308 was overexpressed in CC cells to detect its function by proliferation and apoptosis assays, Transwell assays and animal experiments. The potential mechanism of circRNA_101308 in CC was explored by RNA pull-down, Gene Ontology (GO) and pathway analyses.

Results

CircRNA_101308 was significantly downregulated in CC tissues. The level of circRNA_101308 was much lower in CC patients with lymph node metastasis or deep myometrial invasion compared to those patients without lymph node metastasis and superficial myometrial invasion. CircRNA_101308 overexpression inhibited CC cell proliferation, invasion and migration. MiR-26a-5p, miR-196a-5p, miR-196b-5p, miR-335-3p, and miR-1307-3p were found to be sponged by circRNA_101308 in CC cells. Further, GO and pathway analyses predicted the potential functional processes and pathways of circRNA_101308 in CC.

Conclusion

CircRNA_101308 is downregulated and acts as a tumor suppressor in CC. CircRNA_101308 can participate in many different processes by sponging different miRNAs in CC cells. This exploration of circRNA_101308 provides new directions for research on cancer development and the clinical treatment of CC.

RNAseq profiling of circRNA expression in radiation-treated A549 cells and bioinformatics analysis of radiation-related circRNA-miRNA networks

With the development of new biochemical and computational methods, circular RNAs (circRNAs) have been identified as microRNA sponges. circRNAs are associated with many diseases, particularly cancer. The present study aimed to investigate the expression profile of circRNAs in irradiated A549 lung cancer cells using high-throughput sequencing. Bioinformatics analyses were used to examine the potential functions of circRNAs. RNA sequencing data demonstrated that 1,875 circRNA targets were differentially expressed in A549 cells in response to irradiation. A total of 30 circRNAs were upregulated and 37 circRNAs were downregulated significantly in irradiation-treated A549 cells (fold change ≥2.0; P<0.05). The top 5 upregulated and downregulated circRNAs were successfully validated by reverse transcription-quantitative PCR. In addition, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that differentially expressed circRNAs might be pivotal in biological irradiation responses to irradiation. circRNA-microRNA co-expression networks highlighted the biological significance of circRNA_0002174 and circRNA_0036627, which require further study. In conclusion, the present study is, to the best of the authors' knowledge, the first to describe the differentially expressed profile of circRNAs in response to irradiation in A549 cells. These results provide a new perspective to elucidate insight into the molecular mechanisms by which A549 cells respond to radiation, and a basis for a more in-depth analysis of the potential application of circRNAs in the treatment of lung cancer therapy.

The Expression, Functions and Mechanisms of Circular RNAs in Gynecological Cancers

Circular RNAs (circRNAs) are covalently closed, endogenous non-coding RNAs and certain circRNAs are linked to human tumors. Owing to their circular form, circRNAs are protected from degradation by exonucleases, and therefore, they are more stable than linear RNAs. Many circRNAs have been shown to sponge microRNAs, interact with RNA-binding proteins, regulate gene transcription, and be translated into proteins. Mounting evidence suggests that circRNAs are dysregulated in cancer tissues and can mediate various signaling pathways, thus affecting tumorigenesis, metastasis, and remodeling of the tumor microenvironment. First, we review the characteristics, biogenesis, and biological functions of circRNAs, and describe various mechanistic models of circRNAs. Then, we provide a systematic overview of the functional roles of circRNAs in gynecological cancers. Finally, we describe the potential future applications of circRNAs as biomarkers for prognostic stratification and as therapeutic targets in gynecological cancers. Although the function of most circRNAs remains elusive, some individual circRNAs have biologically relevant functions in cervical cancer, ovarian cancer, and endometrial cancer. Certain circRNAs have the potential to serve as biomarkers and therapeutic targets in gynecological cancers.

Circular RNA and tumor microenvironment

Circular RNAs (circRNAs) are small non-coding RNAs with a unique ring structure and play important roles as gene regulators. Disturbed expressions of circRNAs is closely related to varieties of pathological processes. The roles of circRNAs in cancers have gained increasing concerns. The communications between the cancer cells and tumor microenvironment (TME) play complicated roles to affect the malignant behaviors of cancers, which potentially present new therapeutic targets. Herein, we reviewed the roles of circRNAs in the TME.

CircRNAs: potency of protein translation and feasibility of novel biomarkers and therapeutic targets for head and neck cancers

Circular RNAs (circRNAs), a new star noncoding RNA (ncRNA), show stability, conservation, abundance, and tissue and stage specificity. They act as key regulators of biological processes. They target the mRNAs of many other different genes or signaling pathways, and closely link associated genes into regulatory networks. Growing evidence has demonstrated that circRNAs may play an important role in the carcinogenesis, progression and chemoradiation resistance of many cancers including head and neck cancers (HNC). CircRNA, like other ncRNA, such as miRNA, lncRNA, usually is considered to be non-protein coding transcript. However, recent studies indicated that abnormal translation of circRNAs may be involved in human diseases. In this review, we collected the origin, classification, characteristics, function of circRNAs, exosmal circRNAs, and then synthesize current study results to highlight aberration of circRNAs in various types of HNC, and try to clarify the molecular mechanisms of circRNAs affecting the pathogenesis and progression of HNC, as well as pay particular attention to provide a new avenue to the diagnosis and treatment strategy for HNC.

Functions and mechanisms of circular RNAs in cancer radiotherapy and chemotherapy resistance

Circular RNAs (circRNAs), one type of non-coding RNA, were initially misinterpreted as nonfunctional products of pre-mRNA mis-splicing. Currently, circRNAs have been proven to manipulate the functions of diverse molecules, including non-coding RNAs, mRNAs, DNAs and proteins, to regulate cell activities in physiology and pathology. Accumulating evidence indicates that circRNAs play critical roles in tumor genesis, development, and sensitivity to radiation and chemotherapy. Radiotherapy and chemotherapy are two primary types of intervention for most cancers, but their therapeutic efficacies are usually retarded by intrinsic and acquired resistance. Thus, it is urgent to develop new strategies to improve therapeutic responses. To achieve this, clarification of the underlying mechanisms affecting therapeutic responses in cancer is needed. This review summarizes recent progress and mechanisms of circRNAs in cancer resistance to radiation and chemotherapy, and it discusses the limitations of available knowledge and potential future directions.

Role of non-coding RNAs and RNA modifiers in cancer therapy resistance

As the standard treatments for cancer, chemotherapy and radiotherapy have been widely applied to clinical practice worldwide. However, the resistance to cancer therapies is a major challenge in clinics and scientific research, resulting in tumor recurrence and metastasis. The mechanisms of therapy resistance are complicated and result from multiple factors. Among them, non-coding RNAs (ncRNAs), along with their modifiers, have been investigated to play key roles in regulating tumor development and mediating therapy resistance within various cancers, such as hepatocellular carcinoma, breast cancer, lung cancer, gastric cancer, etc. In this review, we attempt to elucidate the mechanisms underlying ncRNA/modifier-modulated resistance to chemotherapy and radiotherapy, providing some therapeutic potential points for future cancer treatment.

CircRNA_100367 regulated the radiation sensitivity of esophageal squamous cell carcinomas through miR-217/Wnt3 pathway

Background: Circular RNAs (circRNAs) play important roles in regulating the radioresistance of esophageal squamous cell carcinoma (ESCC). This study aimed to determine the role of hsa_circRNA_100367 in regulating radioresistance of ESCC.

Results: Higher expression and potency of endothelial to mesenchymal transformation (EMT) was found in radioresistant ESCC cells (KYSE-150R) than in ESCC cells (KYSE-150). Silencing circRNA_100367 inhibited the proliferation and migration of KYSE-150R cells, and decreased the expression of β-catenin (an important molecule in Wnt pathway) in KYSE-150R cells. Additionally, circRNA_100367 bound to miR-217, and miR-217 targeted Wnt3. Low Wnt3 expression was associated with the short survival time in patients with ESCC and Wnt3 knockdown inhibited the proliferation and migration of KYSE-150R cells. CircRNA_100367 enhanced the radioresistance of KYSE-150R cells through miR-217/Wnt3 pathway. In vivo, circRNA_100367 silence reduced the growth of KYSE-150R cells under radiation.

Conclusion: Our results revealed that circRNA_100367 attenuated radioresistance of ESCC through miR-217/Wnt3 pathway.

Methods: CircRNAs related with the radioresistance of ESCC were analyzed by hierarchical cluster analysis. The relationship between circRNA_100367 and miR-217, Wnt3 was detected by RNA immunoprecipitation (RIP), RNA pull-down and luciferase reporte assays. The proliferation and migration ESCC cells were detected by MTT, Transwell and colony formation assays.

Circular RNAs: The star molecules in cancer

Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs with a closed loop structure. These RNAs are produced by pre-mRNA through variable shear processing and are highly conserved. Such highly conserved molecules play an important role in biology, especially in cancer biology. With the development of experimental techniques such as circRNA microarray screening and high-throughput sequencing technologies, the mystery of circRNAs has gradually been unveiled and the values of function and application have gradually emerged. Among them, cancer-related circRNAs are the most eye-catching. Numerous studies have shown that some circRNAs were involved in the pathogenesis of cancer. This review systematically introduced the cancer-related circRNAs and their origin, formation mechanisms, functions, and applications in the diagnosis and treatment of sixteen kinds of tumors.

CircRNA CBL.11 suppresses cell proliferation by sponging miR-6778-5p in colorectal cancer

BACKGROUND

Radiotherapy (RT) is considered an important therapeutic strategy in the fight against colorectal cancer (CRC). However, the existence of some radioresistance factors becomes the main challenge for the RT. Recently, non-coding RNAs (ncRNAs) have shown an important role in modulating cancer cell responses to ionizing radiation (IR). It is therefore of great significance to elucidate the exact mechanisms of ncRNAs in IR-mediated responses to CRC.

METHODS

Microarrays were used to identify specific miRNAs that may be altered in response to IR. Bioinformatics, luciferase reporter analyses were used to explore the targets of miR-6778-5p. CircRNA CBL.11 was identified to bind with miR-6778-5p by bioinformatic analysis, AGO2 immunoprecipitation and biotinylated RNA pull-down assay. Functional experiments, including CCK-8 assay, cell colony formation assay and EdU incorporation were conducted to investigate the biological roles of miR-6778-5p and circular RNA CBL.11.

RESULTS

MiR-6778-5p was suppressed in CRC cells after irradiation. Results of functional experiments indicated that miR-6778-5p promoted the proliferation of CRC cells. Luciferase reporter analyses showed that YWHAE was a target of miR-6778-5p, which mediated the function of miR-6778-5p in the proliferation of CRC cells via the p53 pathway. Furthermore, we have noticed that after carbon ion irradiation, circRNA CBL.11 was increased in CRC cells and could function as a competing endogenous RNA (ceRNA) to regulate YWHAE expression by sponging miR-6778-5p, resulting in regulation the proliferation of CRC cells.

CONCLUSION

CircRNA CBL.11 may play an important role in improving the efficacy of carbon ion RT against CRC.

hsa_circ_0000745 promotes cervical cancer by increasing cell proliferation, migration, and invasion

Circular RNAs (circRNAs) participate in gene regulation and malignant tumor progression, including uterine cervical cancer (CC). In this study, the expression profile of circRNAs in CC was detected using circRNA microarrays. Then, we selected hsa_circ_0000745 for further examination from the significantly dysregulated circRNAs. Proliferation assays, Transwell assays, quantitative reverse transcription polymerase chain reaction, western blot analysis and tumorigenesis tests in vivo were used to validate the role of hsa_circ_0000745 in CC. hsa_circ_0000745 was upregulated in CC, and its level positively correlated with the level of its linear messenger RNA isoform. Patients with poorly differentiated tumors or vascular/lymphatic invasion presented higher expression of hsa_circ_0000745. The role of hsa_circ_0000745 was illuminated by knocking down hsa_circ_0000745 in CC cells, and the results revealed that reducing hsa_circ_0000745 inhibited cell proliferation, migration, and invasion in CC by upregulating E‐cadherin (E‐cad) expression. In summary, as a tumor promoter in CC, hsa_circ_0000745 enhances the cell's ability to proliferate, migrate, and invade by reducing the expression of E‐cad. hsa_circ_0000745 is a candidate target for the treatment of CC in the clinic.

Circular RNAs in gynecological disease: promising biomarkers and diagnostic targets

Circular RNAs (circRNAs) are a category of RNA molecules with covalently closed circles lacking both a 5′ cap and a 3′ tail. In recent years, circRNAs have attracted much attention and become a research hotspot of the RNA field following miRNAs and lncRNAs. CircRNAs exhibit tissue specificity, structural stability, and evolutionary conservation. Although the biological effects of circRNAs are still underestimated, many studies have shown that circRNAs have functions including regulation of transcription, translation into proteins and miRNA sponges. In this review, we briefly described the biogenesis and function of circRNAs and present circular transcripts in gynecological disease.