CircRNA fibroblast growth factor receptor 3 promotes tumor progression in non-small cell lung cancer by regulating Galectin-1-AKT/ERK1/2 signaling

Advanced approaches of the use of circRNAs as a replacement for cancer therapy

Cancer is a broad name for a group of diseases in which abnormal cells grow out of control and are characterized by their complexity and recurrence. Although there has been progress in cancer therapy with the entry of precision medicine and immunotherapy, cancer incidence rates have increased globally. Non-coding RNAs in the form of circular RNAs (circRNAs) play crucial roles in the pathogenesis, clinical diagnosis, and therapy of different diseases, including cancer. According to recent studies, circRNAs appear to serve as accurate indicators and therapeutic targets for cancer treatment. However, circRNAs are promising candidates for cutting-edge cancer therapy because of their distinctive circular structure, stability, and wide range of capabilities; many challenges persist that decrease the applications of circRNA-based cancer therapeutics. Here, we explore the roles of circRNAs as a replacement for cancer therapy, highlight the main challenges facing circRNA-based cancer therapies, and discuss the key strategies to overcome these challenges to improve advanced innovative therapies based on circRNAs with long-term health effects.

The functional significance of circRNA/miRNA/mRNA interactions as a regulatory network in lung cancer biology

Lung cancer, the leading cause of cancer-related deaths, presents significant challenges to patients due to its poor prognosis. Recent research has increasingly implicated circular RNAs in the development and progression of lung cancer. These circular RNAs have been found to impact various aspects of tumor behavior, including proliferation, metastasis, cell cycle regulation, apoptosis, cancer stem cells, therapy response, and the tumor microenvironment. One of the key mechanisms by which circular RNAs exert their influence is through their ability to act as miRNA sponges, sequestering microRNAs and preventing them from targeting other RNA molecules. Accumulating evidence suggests that circular RNAs can function as competing endogenous RNAs, affecting the expression of target mRNAs by sequestering microRNAs. Dysregulation of competing endogenous RNAs networks involving circular RNAs, microRNAs, and mRNAs leads to the aberrant expression of oncogenes and tumor suppressors involved in lung cancer pathogenesis. Understanding the dynamic interplay and molecular mechanisms among circular RNAs, microRNAs, and mRNAs holds great promise for advancing early diagnosis, personalized therapeutic interventions, and improved patient outcomes in lung cancer. Therefore, this study aims to provide an in-depth exploration of the executive roles of circular RNAs/microRNAs/ mRNAs interactions in lung cancer pathogenesis and their potential utility for diagnosing lung cancer, predicting patient prognosis, and guiding targeted therapies. By offering a comprehensive overview of the dysregulation of the axes as driving factors in lung cancer, we aim to pave the way for their translation into clinical practice in the future.

Translation regulatory long non-coding RNA 1 negatively regulates cell radiosensitivity via the miR-22-3p/SP1 axis in non-small cell lung cancer

OBJECTIVE

Non-small cell lung cancer (NSCLC) occupies 85% of lung cancer. Long non-coding RNAs (LncRNAs) can regulate the radiosensitivity of cancers. This study explored the mechanism of lncRNA TRERNA1 in the radiosensitivity of NSCLC cells.

METHODS

LncRNA TRERNA1 level in NSCLC cell lines was determined. NSCLC cell radiation tolerance was measured. TRERNA1 expression was silenced or overexpressed in A549/HCC827 cells with the highest/lowest radiation tolerance, respectively. The contents of γ-H2AX and SA-β-gal in NSCLC cells after radiation induction were detected. The targeted binding of TRERNA1 to miR-22-3p and miR-22-3p to SP1 were verified by dual-luciferase assay. SP1 expression were detected. Functional rescue experiments were implemented to confirm the roles of miR-22-3p and SP1 in the regulatory mechanism of TRERNA1.

RESULTS

TRERNA1 was upregulated in NSCLC cells. TRERNA1 silencing enhanced radiosensitivity of NSCLC cells. TRERNA1 silencing elevated the contents of γ-H2AX and SA-β-gal in A549 cells after radiation induction, while TRERNA1 overexpression showed an opposite trend in HCC827 cells. There were targeting relationships between TRERNA1 and miR-22-3p, and miR-22-3p and SP1. miR-22-3p repression or SP1 overexpression abolished the effects of TRERNA1 silencing.

CONCLUSION

TRERNA1 silencing enhanced radiosensitivity of NSCLC cells via the miR-22-3p/SP1 axis. This study may offer new targets for NSCLC treatment.

Identification of circRNA-associated ceRNA networks in peripheral blood mononuclear cells as potential biomarkers for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), which is a common respiratory disorder with high morbidity and mortality globally, has a complex pathogenesis that is not fully understood. Some circular RNAs (circRNAs) have been recognized to serve as miRNA sponges for regulating target RNA transcripts during the processes of human diseases. In the present study, we aimed to investigate novel circRNA-associated biomarkers for COPD, 245 differentially expressed circRNAs were identified, including 111 up-regulated and 134 down-regulated circRNAs. These candidate circRNAs were enriched in inflammation-associated pathways (such as mTOR, B-cell receptor, and NF-κB signaling pathways) via Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses. A combination of two circRNAs (up-regulated hsa_circ_0067209 and down-regulated hsa_circ_0000673) demonstrated good diagnostic value (area under the receiver operating characteristic curve [AUC] = 0.866) for COPD by receiver operating characteristic curve (ROC) analysis and qRT-PCR validation. Subsequently, hsa-miR-8082 and hsa-miR-1248 were identified as targets for hsa_circ_0067209 and hsa_circ_0000673, respectively, via bioinformatics analysis and a dual-luciferase reporter assay, and the combination of these two miRNAs displayed better diagnosis potential for COPD (AUC = 0.967) than each other. Evaluation of COPD-related mRNA profiles revealed that the up-regulated genes ABR and TRPM6 were predicted downstream targets for hsa_circ_0067209/hsa-miR-8082, whereas the down-regulated gene RORC was a predicted downstream target for hsa_circ_0000673/hsa-miR-1248. In summary, hsa_circ_0067209 and hsa_circ_0000673 have potential as novel diagnostic biomarkers of COPD. In addition, competing endogenous RNA networks of hsa_circ_0067209/hsa-miR-8082/ABR/TRPM6 and hsa_circ_0000673/hsa-miR-1248/RORC may play critical regulation roles for COPD pathogenesis.

CircRNAs and lung cancer: Insight into their roles in metastasis

Lung cancer is the leading cause of cancer-related mortality worldwide. A major contributing factor to the poor survival rates in lung cancer is the high prevalence of metastasis at the time of diagnosis. To address this critical issue, it is imperative to investigate the mechanisms underlying lung cancer metastasis. Circular RNAs (circRNAs), a distinct type of ribonucleic acid characterized by their unique circular structure, have been implicated in the progression of various diseases. Recent studies have highlighted the close association between circRNAs and the occurrence and development of lung cancer, particularly in relation to metastasis. In this review, we provide a concise overview of the expression patterns and prognostic significance of circRNAs in lung cancer. Additionally, we summarized the current understanding of the clinical relevance of circRNAs in lung cancer metastasis. Furthermore, we systematically focused on the roles of circRNAs in each step of lung cancer metastasis, reflecting the sequential progression of this process. Notably, circRNAs exhibit dual functionality in lung cancer metastasis, acting both as facilitators and inhibitors of metastatic processes. Given their potential, circRNAs hold promise as novel biomarkers and therapeutic targets for lung cancer metastasis, warranting further investigation.

FGFR families: biological functions and therapeutic interventions in tumors

There are five fibroblast growth factor receptors (FGFRs), namely, FGFR1-FGFR5. When FGFR binds to its ligand, namely, fibroblast growth factor (FGF), it dimerizes and autophosphorylates, thereby activating several key downstream pathways that play an important role in normal physiology, such as the Ras/Raf/mitogen-activated protein kinase kinase/extracellular signal-regulated kinase, phosphoinositide 3-kinase (PI3K)/AKT, phospholipase C gamma/diacylglycerol/protein kinase c, and signal transducer and activator of transcription pathways. Furthermore, as an oncogene, FGFR genetic alterations were found in 7.1% of tumors, and these alterations include gene amplification, gene mutations, gene fusions or rearrangements. Therefore, FGFR amplification, mutations, rearrangements, or fusions are considered as potential biomarkers of FGFR therapeutic response for tyrosine kinase inhibitors (TKIs). However, it is worth noting that with increased use, resistance to TKIs inevitably develops, such as the well-known gatekeeper mutations. Thus, overcoming the development of drug resistance becomes a serious problem. This review mainly outlines the FGFR family functions, related pathways, and therapeutic agents in tumors with the aim of obtaining better outcomes for cancer patients with FGFR changes. The information provided in this review may provide additional therapeutic ideas for tumor patients with FGFR abnormalities.

Melatonin targeting non-coding RNAs in cancer: Focus on mechanisms and potential therapeutic targets

Despite, melatonin is mainly known as a regulatory factor for circadian rhythm, its notable role in other fundamental biological processes, such as redox homeostasis and programmed cell death, has been found. In this line, a growing body of evidence indicated that melatonin could apply an inhibitory effect on the tumorigenic processes. Hence, melatonin might be considered an efficient adjuvant agent for cancer treatment. Besides, the physiological and pathological functions of non-coding RNAs (ncRNAs) in various disease, particularly cancers, have been expanded over the past two decades. It is well-established that ncRNAs can modulate the gene expression at various levels, thereby, ncRNAs. can regulate the numerous biological processes, including cell proliferation, cell metabolism, apoptosis, and cell cycle. Recently, targeting the ncRNAs expression provides a novel insight in the therapeutic approaches for cancer treatment. Moreover, accumulating investigations have revealed that melatonin could impact the expression of different ncRNAs in a multiple disorders, including cancer. Therefore, in the precent study, we discuss the potential roles of melatonin in modulating the expression of ncRNAs and the related molecular pathways in different types of cancer. Also, we highlighted its importance in therapeutic application and translational medicine in cancer treatment.

TTI1 promotes non-small-cell lung cancer progression by regulating the mTOR signaling pathway

The role of TELO2-interacting protein 1 (TTI1) in the progression of several types of cancer has been reported recently. The aim of this study was to estimate the expression and potential value of TTI1 in non-small-cell lung cancer (NSCLC) patients. The expression of TTI1 and its prognostic value in NSCLC from The Cancer Genome Atlas (TCGA) database and Gene Expression Omnibus (GEO) database were analyzed. To verify the bioinformatics findings, a tissue microarray containing 160 NSCLC and paired peritumoral tissues from NSCLC patients was analyzed by immunohistochemistry for TTI1. Subsequently, the roles of TTI1 in NSCLC cells were investigated in vivo by establishing xenograft models in nude mice and in vitro by transwell, CCK-8, wound healing, and colony formation assays. In addition, quantitative real-time polymerase chain reaction and western blot were applied to explore the underlying mechanism by which TTI1 promotes tumor progression. Finally, the relationship between TTI1 and Ki67 expression level in NSCLC was probed, and Kaplan-Meier and Cox analyses were performed to assess the prognostic merit of TTI1 and Ki67 in NSCLC patients. We found that the expression of TTI1 was significantly upregulated in NSCLC tissues compared to paired peritumoral tissues, which coincides with the bioinformatics findings from the TCGA and GEO databases. TTI1 was highly expressed in NSCLC patients with large tumors, advanced tumor stage, and lymphatic metastasis. In addition, the prognostic analysis identified TTI1 as an independent indication for poor prognosis of NSCLC patients. In vitro, upregulation of TTI1 in NSCLC cells could facilitate cell invasion, metastasis, viability, and proliferation. Mechanistically, our study verified that TTI1 could regulate mTOR activity, which has a pivotal role in human cancer. Consistently, the expressions of TTI1 and Ki67 had a positive relationship in NSCLC cells and tissues. Notably, patients with overexpression of TTI1 or Ki67 had a shorter overall survival rate and a higher disease-free survival rate compared to patients with low expression of TTI1 or Ki67, and the combination of TTI1 and Ki67 was an independent parameter predicting the prognosis and recurrence of NSCLC patients. We conclude that TTI1 promotes NSCLC cell proliferation, metastasis, and invasion by regulating mTOR activity, and the combination of TTI1 and Ki67 is a valuable molecular biomarker for the survival and recurrence of NSCLC patients.

Inhibition of galectins in cancer: Biological challenges for their clinical application

Galectins play relevant roles in tumor development, progression and metastasis. Accordingly, galectins are certainly enticing targets for medical intervention in cancer. To date, however, clinical trials based on galectin inhibitors reported inconclusive results. This review summarizes the galectin inhibitors currently being evaluated and discusses some of the biological challenges that need to be addressed to improve these strategies for the benefit of cancer patients.

Hsa‐circ‐0052001 promotes gastric cancer cell proliferation and invasion via the MAPK pathway

BACKGROUND

Gastric cancer (GC) ranks fourth among the causes of death from malignant tumors in the world. Studies have implicated the dysregulation of circRNAs with GC. However, the relationship between hsa-circ-0052001 and GC is unclear.

METHODS

In our current study, we assessed the expression levels of hsa-circ-0052001 in GC cells and tissues using quantitative real-time PCR (qPCR). The role of hsa-circ-0052001 expression on the proliferation and invasion of GC cells was assessed using in vitro experiments. The role of hsa-circ-0052001 on the proliferation of GC cells was also analyzed using in vivo models. The pathways downstream of hsa-circ-0052001 were identified using bioinformatics analyses, western blot (WB) assays, and qRT-PCR.

RESULTS

We found that compared with normal gastric mucosa epithelial cells and adjacent paracancer tissues, hsa-circ-0052001 was overexpressed in GC cells and tissues. Also, the hsa-circ-0052001 level was linked to patient clinicopathological characteristics of GC. Cell proliferation and metastatic ability were inhibited in gastric cancer cells when hsa-circ-0052001 was knocked down in vitro and cancer growth in vivo. Mechanistically, hsa-circ-0052001 promoted the carcinogenesis of GC cells via the MAPK signal pathway.

CONCLUSION

Hsa-circ-0052001 functions as a tumor gene in promoting the progression of GC through MAPK pathway, which has provided a promising target for patients with GC.

circRanGAP1/miR-27b-3p/NRAS Axis may promote the progression of hepatocellular Carcinoma

Background

Though circular RNAs (circRNAs) are the key regulators in tumor carcinogenesis, they remain largely unexplored in hepatocellular carcinoma (HCC).

Methods

The expression of RanGAP1-derived circRNAs (circ_0063531, circ_0063534, circ_0063513, circ_0063518, circ_0063507, circ_0063723) were evaluated in eight paired HCC and normal tissues, and the correlation between circRanGAP1 (circ_0063531) expression and clinicopathological characteristics in 40 HCC patients was determined. The association between miR-27b-3p and circRanGAP1 or NRAS was predicted using bioinformatics analysis. The expression of circRanGAP1, miR-27b-3p, and NRAS were detected by quantitative real-time polymerase chain reaction (qRT-PCR). The potential oncogenic role of circ-RanGAP1 was assessed using CCK-8, colony formation, transwell assays in vitro, subcutaneous tumor mouse model, vein tail metastatic model, and orthotopically implanted intrahepatic HCC model in vivo. Luciferase reporter and RNA immunoprecipitation (RIP) assays were used to explore the binding site between miR-27b-3p and circ-RanGAP1 or NRAS. Protein expression was detected using western blotting. The localization of miR-27b-3p and circ-RanGAP1 was investigated using fluorescence in situ hybridization (FISH). The level of immune infiltration was assessed by bioinformatics analysis, flow cytometry, and orthotopically implanted intrahepatic HCC models.

Results

Here, we found elevated circRanGAP1 in the cells and clinical tissues of patients with HCC. Increased circRanGAP1 levels are associated with enlarged tumors and the advanced stage of TNM. CircRanGAP1 promotes the growth, migration, and HCC cell invasion, concurrently with the growth and metastasis of tumors in-vivo. Moreover, circRanGAP1 is mainly located inside the cytoplasm. Mechanistically, circRanGAP1 as an oncogene promotes HCC progression by miR-27b-3p/NRAS/ERK axis, furthermore, affects the infiltration level of tumor-associated macrophages probably by sponging miR-27b-3p. Immune infiltration analysis shows that NRAS is positively correlated with the levels of CD68+ tumor-associated macrophages in HCC samples and that NRAS and CD68 are related to the poor outcome of HCC.

Conclusion

These results reveal that circRanGAP1 is a HCC oncogene that function by the miR-27b-3p/NRAS/ERK axis and regulates the infiltration levels of tumor-associated macrophages by sponging miR-27b-3p. Therefore, circRANGAP1/ NRAS axis may be an important potential treatment target against HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40164-022-00342-6.

A Novel P53 Nanomedicine Reduces Immunosuppression and Augments Anti-PD-1 Therapy for Non-Small Cell Lung Cancer in Syngeneic Mouse Models

Lung cancer is among the most common and lethal cancers and warrants novel therapeutic approaches to improving patient outcomes. Although immune checkpoint inhibitors (ICIs) have demonstrated substantial clinical benefits, most patients remain unresponsive to currently approved ICIs or develop resistance after initial response. Many ongoing clinical studies are investigating combination therapies to address the limited efficacy of ICIs. Here, we have assessed whether p53 gene therapy via a tumor-targeting nanomedicine (termed SGT-53) can augment anti-programmed cell death-1 (PD-1) immunotherapy to expand its use in non-responding patients. Using syngeneic mouse models of lung cancers that are resistant to anti-PD-1, we demonstrate that restoration of normal p53 function potentiates anti-PD-1 to inhibit tumor growth and prolong survival of tumor-bearing animals. Our data indicate that SGT-53 can restore effective immune responses against lung cancer cells by reducing immuno-suppressive cells (M2 macrophages and regulatory T cells) and by downregulating immunosuppressive molecules (e.g., galectin-1, a negative regulator of T cell activation and survival) while increasing activity of cytotoxic T cells. These results suggest that combining SGT-53 with anti-PD-1 immunotherapy could increase the fraction of lung cancer patients that responds to anti-PD-1 therapy and support evaluation of this combination particularly in patients with ICI-resistant lung cancers.

The function and clinical implication of circular RNAs in lung cancer

Lung cancer is the leading cause of cancer-related deaths worldwide. Despite the recent advent of promising new targeted therapies, lung cancer diagnostic strategies still have difficulty in identifying the disease at an early stage. Therefore, the characterizations of more sensible and specific cancer biomarkers have become an important goal for clinicians. Circular RNAs are covalently close, endogenous RNAs without 5' end caps or 3'poly (A) tails and have been characterized by high stability, abundance, and conservation as well as display cell/tissue/developmental stage-specific expressions. Numerous studies have confirmed that circRNAs act as microRNA (miRNA) sponges, RNA-binding protein, and transcriptional regulators; some circRNAs even act as translation templates that participate in multiple pathophysiological processes. Growing evidence have confirmed that circRNAs are involved in the pathogenesis of lung cancers through the regulation of proliferation and invasion, cell cycle, autophagy, apoptosis, stemness, tumor microenvironment, and chemotherapy resistance. Moreover, circRNAs have emerged as potential biomarkers for lung cancer diagnosis and prognosis and targets for developing new treatments. In this review, we will summarize recent progresses in identifying the biogenesis, biological functions, potential mechanisms, and clinical applications of these molecules for lung cancer diagnosis, prognosis, and targeted therapy.

Melatonin may suppress lung adenocarcinoma progression via regulation of the circular noncoding RNA hsa_circ_0017109/miR-135b-3p/TOX3 axis

Melatonin is a hormone synthesized in the pineal gland and has widespread physiological and pharmacological functions. Moreover, it can activate protective receptor-dependent processes. These processes can prevent tissue carcinogenesis and inhibit malignant tumor progression and metastasis. Therefore, we investigated the regulatory effects of melatonin on dysregulated circular RNAs in human lung adenocarcinoma (LUAD) cells. In this study, we treated LUAD cells with melatonin and measured the expression of hsa_circ_0017109, miR-135b-3p, and TOX3 by quantitative reverse transcription polymerase chain reaction. Colony formation and cell counting kit-8 assays were used to determine cell proliferation. The wound-healing assay and Transwell experiment were carried out to evaluate the migration potential and invasive capacity of LUAD cells. Also, cell apoptosis was detected using a cell apoptosis kit, and protein production was identified by Western blot. It was suggested that melatonin could inhibit LUAD progression in vivo and in vitro, and the role of TOX3 in this process was explored. Additionally, hsa_circ_0017109 was found to sponge miR-135b-3p, a downstream factor of circ_0017109, which was demonstrated to target TOX3 in LUAD cells and could promote the Hippo pathway and epithelial-mesenchymal transition pathway. To summarize, we demonstrated that melatonin decreases the expression of circ_0017109 and suppresses the non-small-cell lung cancer cell migration, invasion, and proliferation through decreasing TOX3 expression via direct activation of miR-135b-3p.

The Role of NcRNAs to Regulate Immune Checkpoints in Cancer

At present, the incidence of cancer is becoming more and more common, but its treatment has always been a problem. Although a small number of cancers can be treated, the recurrence rates are generally high and cannot be completely cured. At present, conventional cancer therapies mainly include chemotherapy and radiotherapy, which are the first-line therapies for most cancer patients, but there are palliatives. Approaches to cancer treatment are not as fast as cancer development. The current cancer treatments have not been effective in stopping the development of cancer, and cancer treatment needs to be imported into new strategies. Non-coding RNAs (ncRNAs) is a hot research topic at present. NcRNAs, which include microRNAs (miRNAs), circular RNAs (circRNAs), and long non-coding RNAs (lncRNAs), participate in all aspects of cancer biology. They are involved in the progression of tumors into a new form, including B-cell lymphoma, glioma, or the parenchymal tumors such as gastric cancer and colon cancer, among others. NcRNAs target various immune checkpoints to affect tumor proliferation, differentiation, and development. This might represent a new strategy for cancer treatment.

circRNA circMED27 acts as a prognostic factor and mediator to promote lenvatinib resistance of hepatocellular carcinoma

Circular RNAs (circRNAs) have been proven to play key roles in the development and progression of various types of cancers. However, there were no reported studies on the roles of circRNA mediator complex subunit 27 (circMED27) in tumors including hepatocellular carcinoma (HCC). In this study, we found that circMED27 was significantly increased in HCC serum and that higher levels of circMED27 were correlated with bad clinical characteristics and poor prognoses of patients with HCC. Furthermore, upregulated circMED27 promoted HCC resistance to lenvatinib. Our mechanistic investigations revealed that circMED27 functions as a competing endogenous RNA (ceRNA) for miR-655-3p to upregulate ubiquitin-specific peptidase 28 (USP28) expression. Thus, we are led to conclude that circMED27 acts as a potential therapeutic target for HCC patients receiving lenvatinib therapy and may represent a promising molecular biomarker for forecasting lenvatinib-resistant HCC.

Biogenesis, functions, and clinical implications of circular RNAs in non-small cell lung cancer

Lung cancer (LC) is the leading cause of cancer-related deaths worldwide, with high morbidity and mortality. Non-small cell lung cancer (NSCLC) is a major pathological type of LC and accounts for more than 80% of all cases. Circular RNAs (circRNAs) are a large class of non-coding RNAs (ncRNAs) with covalently closed-loop structures, a high abundance, and tissue-specific expression patterns. They participate in various pathophysiological processes by regulating complex gene networks involved in proliferation, apoptosis, migration, and epithelial-to-mesenchymal transition (EMT), as well as metastasis. A growing number of studies have revealed that the dysregulation of circRNAs contributes to many aspects of cancer progression, such as its occurrence, metastasis, and recurrence, suggesting their great potential as efficient and specific biomarkers in the diagnosis, prognosis, and therapeutic targeting of NSCLC. In this review, we systematically elucidate the characteristics, biogenesis, and functions of circRNAs and focus on their molecular mechanisms in NSCLC progression. Moreover, we highlight their clinical implications in NSCLC treatment.

Galectin-1-Dependent Mitochondria Apoptosis Plays an Essential Role in the Potential Protein Targets of DBDCT-Induced Hepatotoxicity as Revealed by Quantitative Proteomic Analyses

Di-n-butyl-di-(4-chlorobenzohydroxamato) tin(IV) (DBDCT), a new patent agent, exhibited strong antitumor activity. In some cases, its activity was close to or even higher than cisplatin, a first-line clinical metallic agent. Similar to platinum compounds, it also showed toxicity. However, the effective targets and mechanisms for specific toxicity and biological activity are still unclear. In this study, proteomic analysis revealed that 146 proteins (98 upregulated and 48 downregulated) were differentially identified by label-free LC-MS/MS after DBDCT treatment. Meanwhile, network analysis of these differential proteins suggested that protein Galectin-1 (Gal-1) could regulate the apoptosis process (15 related proteins), which played an essential role in the potential targets of DBDCT-induced hepatotoxicity. Furthermore, it was demonstrated that DBDCT might promote ROS production, activate NF-κB p65, inhibit Ras and p-ERK1/2 expressions, increase the level of Gal-1, subsequently upregulate the expressions of Bax, p53, Fas, and FasL, and downregulate the expression of Bcl-2. As a result of these modulations, caspase cascades were finally activated, which executed apoptosis in HL7702 liver cells. Correspondingly, NAC (inhibitor of ROS), PDTC (inhibitor of NF-κB), EGF (ERK1/2 activator), and OTX008 (inhibitor of Gal-1) were found to reverse and abolish the DBDCT-associated cytotoxicity partially. In conclusion, Gal-1 might be the potential target for toxicity and biological activity. Moreover, the present study will lay the groundwork for future research about di-n-butyl-di-(4-chlorobenzohydroxamato) tin structure optimization and developing it into a new potential anticancer agent.

Circ_0006220 promotes non-small cell lung cancer progression via sponging miR-203-3p and regulating RGS17 expression

BACKGROUND

Lung cancer is the most common malignancy, and its mortality ranks first among malignancies. Non-small cell lung carcinoma (NSCLC) is the most common pathological subtype of lung cancer. It is reported that circular RNAs (circRNAs) feature prominently in the occurrence and metastasis of NSCLC.

PURPOSE

This study aims to decipher the biological functions of circ_0006220 in NSCLC and the underlying mechanism.

METHODS

The microarray data (GSE101586) were downloaded from the Gene Expression Omnibus database, and differentially expressed circRNAs in NSCLC tissues were screened using the GEO2R tool. Quantitative real-time polymerase chain reaction was used for detecting the expression of circ_0006220, miR-203-3p, and regulator of G-protein signaling 17 (RGS17) mRNA in NSCLC tissues and cells. The connection between circ_0006220 expression and clinicopathological indicators was analyzed through the chi-square test. EdU and cell counting kit-8 assays were carried out to detect cell growth. Cell migration and invasion were detected by transwell assays. Bioinformatics was used to predict, and RNA immunoprecipitation assay and dual-luciferase reporter gene assay were conducted for verifying, the targeted relationship among circ_0006220, miR-203-3p, and RGS17.

RESULTS

The expression of circ_0006220 was elevated in NSCLC cells and tissues, and high circ_0006220 expression was significantly associated with unfavorable clinicopathological indicators. In addition, it was revealed that circ_0006220 overexpression facilitated NSCLC cell growth, migration, and invasion, whereas knocking down circ_0006220 had contrary effects. Furthermore, miR-203-3p was identified as a downstream target of circ_0006220, and circ_0006220 could sponge miR-203-3p; RGS17 was identified as a downstream target of miR-203-3p and was positively modulated by circ_0006220.

CONCLUSIONS

Circ_0006220 up-regulates RGS17 expression by adsorbing miR-203-3p to promote NSCLC development.

Circular RNA circFGFR1 Functions as an Oncogene in Glioblastoma Cells through Sponging to hsa-miR-224-5p

Recently, increased studies have shown the important regulatory role of circular RNA (circRNA) in cancer progression and development, including glioblastoma (GBM). However, the function of circRNAs in glioblastoma is still largely unclear. Here, we state that circFGFR1 is elevated in glioma cells, resulting in aggravated glioma aggravated malignancy. The upregulation of circFGFR1 also promotes glioma growth in mouse xenograft models. Furthermore, CXCR4 level in glioma cells is positively correlated with circFGFR1 level, and higher CXCR4 expression is found in circFGFR1 overexpression groups. The effect of circFGFR1 on glioma malignancy is abolished in CXCR4 knockout cells. Then, RIP, RNA pull-down, and luciferase reporter assay results showed that hsa-miR-224-5p directly binds to circFGFR1 and CXCR4 mRNA. The CXCR4 3′-untranslated region (UTR) activated luciferase activity was reduced with hsa-miR-224-5p transfection, while it is reversed when cotransfected with circFGFR1, indicating that circFGFR1 acts as a hsa-miR-244-5p sponge to increase CXCR4 expression. The hsa-miR-224-5p expression is negatively corrected with the glioma malignancy through inhibiting CXCR4 level. Besides, the circFGFR1-induced regulation in glioma malignancy is also abrogated in hsa-miR-224-5p knockout cells. Taken together, our findings suggest that circFGFR1 plays a critical role in the tumorigenic behaviors in glioma cells by upregulating CXCR4 expression via sponging to hsa-miR-224-5p. These findings provide a new perspective on circRNAs during GBM development.

Circular RNA regulates the onset and progression of cancer through the mitogen-activated protein kinase signaling pathway

The rapid increase in cancer morbidity and mortality worldwide is a major challenge for public health providers. Therefore, there is an urgent need to explore the molecular mechanism of tumorigenesis and identify potential diagnostic biomarkers and therapeutic methods. Circular RNA (circRNA) is characterized by a stable structure and tissue-specific expression; these features are useful in medical research and clinical applications. In recent years, with the development of high-throughput sequencing technology, the potential use of circRNA in cancer prognosis and treatment has been extensively explored. Abnormal circRNA expression interferes with specific signaling pathways such as the MAPK pathway; this phenomenon may provide potential diagnostic biomarkers and new therapeutic targets. The present article discusses the research progress on the regulatory roles of MAPK/ERK pathway-related circRNA molecules in the development and progression of different types of tumors. This review may provide insight into the development of circRNA-based cancer management strategies.

Critical appraisal of epigenetic regulation of galectins in cancer

Galectins are defined as the glycan-binding protein containing either one or two carbohydrate-binding domains and participate in various biological functions such as developmental processes, vascularisation programs, cell migration, and immune-regulation and apoptosis. Galectins are also linked to many diseases, including cancer. They are widely spread in extracellular and intracellular spaces, and their altered expression in cancer leads to tumor progression, metastasis, angiogenesis and stemness through different signalling pathways. Promoter methylation, microRNA, and histone modification constitute the epigenetic changes that regulate galectin activity in cancer. Our review discusses the concept of epigenetics in cancer and how the aforementioned factors i.e., promoter methylation, histone modification, change in miRNAs expression affect the glycomic changes in malignancies.

Biogenesis, Functions, and Role of CircRNAs in Lung Cancer

CircRNAs, a class of endogenous non-coding RNAs with closed-loop structures, have attracted increasing attention because of their good stability, high specificity of tissue expression, long half-life, and highly conserved sequence. CircRNAs have multiple biological functions, including miRNA sponge, transcription regulator, protein translation, interaction with protein, RNA maturation, and so on. These functions indicate the important role of circRNAs in tumorigenesis and malignant progression and their potential as potent diagnostic biomarkers and therapeutic molecules. In recent years, an increasing body of evidence suggests that circRNAs play a crucial role in proliferation, migration, invasion, and apoptosis of lung cancer cells. Therefore, circRNAs have gradually become a research focus in the diagnosis and treatment of lung cancer patients. This review summarizes the classification, biogenesis, and function of circRNAs, and discusses the role of circRNAs in the diagnosis, prognosis, and treatment of lung cancer patients.

Benzo[a]pyrene diol epoxide-induced transformed cells identify the significance of hsa_circ_0051488, a ERCC1-derived circular RNA in pulmonary squamous cell carcinoma

ERCC1 is a gene for repairing DNA damage whose function is related to carcinogenic-induced tumorigenesis and the effectiveness of platinum therapies. Circular RNAs (circRNAs) are products of posttranscriptional regulation with pleiotropic effects on the pathogenesis of lung cancer. We aim to identify that specific circRNAs derived from ERCC1 can regulate key biological processes involved in the development of lung cancer. We performed bioinformatics analysis, in vitro experiments, and analyzed clinical samples, to determine the biological features of a certain ERCC1-derived circRNA termed as hsa_circ_0051488 in benzo[a]pyrene diol epoxide-induced malignant transformed cell and lung cancer cell. The well-established model of transformed cells provided an ideal platform for analyzing the molecular characteristics of this circRNA in the malignant transformation of lung epithelial cell, which supports that hsa_circ_0051488 functions in the onset and growth of lung squamous cell carcinoma (LUSC). Further analysis indicates that the absence of hsa_circ_0051488 promoted the proliferation of cells with the malignant phenotype. Extensive experiments confirm that hsa_circ_0051488 is present in the cytoplasm and functioned as a competing endogenous RNA. In particular, hsa_circ_0051488 binds to mir-6717-5p, thereby modulating the expression of SATB2 gene, a lung cancer suppressor. Furthermore, our in silico experiments indicate that SATB2 can inhibit multiple tumor pathways and its expression positively correlated with the tumor suppressor gene CRMP1. These findings suggest a possible regulatory mechanism of hsa_circ_0051488 in LUSC, and that the newly discovered hsa_circ_0051488/miR-6717-5p/SATB2 axis may be a potential route for therapeutic intervention of LUSC.

Circular RNA circEGFR regulates tumor progression via the miR-106a-5p/DDX5 axis in colorectal cancer

Recently, an increasing number of studies have reported that dysregulation of circular RNA (circRNA) expression plays critical roles in the progression of several cancers, including colorectal cancer (CRC). However, the detailed molecular mechanisms of circRNAs involvement in CRC remain largely unknown. Here, we confirmed that the level of circEGFR was significantly increased in CRC tissues compared to matched adjacent non-tumor tissues, and a high level of circEGFR was correlated with poor clinicopathological characteristics and poor prognosis in patients with CRC. Moreover, increased circEGFR expression promoted CRC cell proliferation, migration, and invasion in vitro. Mechanistically, circEGFR acted as a ceRNA for miR-106a-5p to relieve the repressive effect of miR-106a-5p on DDX5 mRNA. Moreover, circEGFR enhanced DDX5 expression, thereby upregulating p-AKT levels. Together, these findings showed that circEGFR promoted CRC cell proliferation, migration, and invasion through the miR-106a-5p/DDX5/AKT axis, and may serve as a promising diagnostic marker and therapeutic target for CRC patients.

Circular RNAs in Lung Cancer: Recent Advances and Future Perspectives

Globally, lung cancer is the most commonly diagnosed cancer and carries with it the greatest mortality rate, with 5-year survival rates varying from 4–17% depending on stage and geographical differences. For decades, researchers have studied disease mechanisms, occurrence rates and disease development, however, the mechanisms underlying disease progression are not yet fully elucidated, thus an increased understanding of disease pathogenesis is key to developing new strategies towards specific disease diagnoses and targeted treatments. Circular RNAs (circRNAs) are a class of non-coding RNA widely expressed in eukaryotic cells, and participate in various biological processes implicated in human disease. Recent studies have indicated that circRNAs both positively and negatively regulate lung cancer cell proliferation, migration, invasion and apoptosis. Additionally, circRNAs could be promising biomarkers and targets for lung cancer therapies. This review systematically highlights recent advances in circRNA regulatory roles in lung cancer, and sheds light on their use as potential biomarkers and treatment targets for this disease.

Circular RNA hsa_circ_0072309 promotes tumorigenesis and invasion by regulating the miR-607/FTO axis in non-small cell lung carcinoma

Emerging evidence has demonstrated that circular RNAs (circRNAs) are abnormally expressed in non-small cell lung carcinoma (NSCLC). However, the contributions of circRNAs to the tumorigenesis of lung adenocarcinoma (LUAD), one of the subtypes of NSCLC, remain unclear. Based on a microarray assay, we found that hsa_circ_0072309 was significantly upregulated in NSCLC compared with matched normal samples. Moreover, functional experiments demonstrated that hsa_circ_0072309 promotes the proliferation, migration, and invasion of NSCLC cells. In vitro precipitation of circRNAs, luciferase reporter assays, and biotin-coupled microRNA capture assays were carried out to investigate the mechanisms by which hsa_circ_0072309 regulates NSCLC. Through the above work, we found that hsa_circ_0072309 interacted with miR-607 via its miRNA response element to upregulate the expression of FTO, an m6A demethylase and downstream target of miR-607, thus promoting tumorigenesis of NSCLC. In total, our findings indicated the oncogenic role of hsa_circ_0072309 in NSCLC and provide a potential target for treatment.

Clinicopathological and prognostic significance of circRNAs in lung cancer: A systematic review and meta-analysis

BACKGROUND

Circular RNAs (circRNAs) regulate multiple pathways during lung cancer pathogenesis. Apart from functional significance, many circRNAs have been shown to be associated with clinicopathological characteristics and predict lung cancer prognosis. Our aim is to summarize the expanding knowledge of clinical roles of circRNAs in lung cancer.

METHODS

A thorough search of literature was conducted to identify articles about the correlation between circRNA expression and its prognostic and clinicopathological values. Biological mechanisms were summarized.

RESULTS

This study included 35 original articles and 32 circRNAs with prognostic roles for lung cancer. Increased expression of 25 circRNAs and decreased expression of 7 circRNAs predicted poor prognosis. For non-small cell lung cancer, changes of circRNAs were correlated with tumor size, lymph node metastasis, distant metastasis, tumor node metastasis (TNM) stage, and differentiation, indicating the major function of circRNAs is to promote lung cancer invasion and migration. Particularly, meta-analysis of ciRS-7, hsa_circ_0020123, hsa_circ_0067934 showed increase of the 3 circRNAs was associated with positive lymph node metastasis. Increase of ciRS-7 and hsa_circ_0067934 was also related with advanced TNM stage. The biological effects depend on the general function of circRNA as microRNA sponge.

CONCLUSIONS

CircRNAs have the potential to function as prognostic markers and are associated with lung cancer progression and metastasis.

TRPM2-AS Promotes Bladder Cancer by Targeting miR-22-3p and Regulating GINS2 mRNA Expression

Background

Bladder cancer (BLCA) refers to the malignancy growth that spreads from the bladder linings to the bladder muscles. However, the impact of miR-22-3p and lncRNA TRPM2-AS on this tumor has generated divergent views in the literature. This research aimed to study the effects of lncRNA TRPM2-AS on BLCA and its interaction with miR-22-3p and GINS2 mRNA.

Methods

qRT-PCR was employed to measure the expression of TRPM2-AS, miR-22-3p and GINS2 mRNA in bladder tissues and cells. The subcellular localization of TRPM2-AS in T24 and 5637 cell lines was identified using a cell fractionation system. Luciferase assay, RIP assay and RNA pull-down assay were later performed to validate the direct binding relationship between TRPM2-AS, miR-22-3p and GINS2 mRNA. Several experiments were conducted to determine the viability, proliferation, colony formation and apoptosis of the cell lines.

Results

Findings indicated that TRPM2-AS was significantly upregulated in BLCA tissues and cell lines. Apart from that, it was observed that TRPM2-AS knockdown significantly inhibited the viability, proliferation and colony formation of BCLA cells, but it promoted the apoptosis of the BCLA cells. A significant downstream target of TRPM2-AS, miR-22-3p was found to show a lower expression level in BLCA tissues and cell lines. However, the inhibition of miR-22-3p considerably enhanced BLCA cell phenotypes. As well as discovering that GINS2 mRNA was a downstream target of miR-22-3p and was significantly upregulated in BLCA, experimental results also indicated that the knockdown of GINS2 suppressed BLCA cell phenotypes.

Conclusion

This research confirmed that TRPM2-AS could promote BCLA by binding to miR-22-3p to increase GINS2 expression. This novel interactome in BLCA cell lines might provide more insights into BLCA therapy.

Insights Into circRNAs: Functional Roles in Lung Cancer Management and the Potential Mechanisms

Lung cancer is the most prevalent cancer globally. It is also the leading cause of cancer-related death because of the late diagnosis and the frequent resistance to therapeutics. Therefore, it is impending to identify novel biomarkers and effective therapeutic targets to improve the clinical outcomes. Identified as a new class of RNAs, circular RNAs (circRNAs) derive from pre-mRNA back splicing with considerable stability and conservation. Accumulating research reveal that circRNAs can function as microRNA (miRNA) sponges, regulators of gene transcription and alternative splicing, as well as interact with RNA-binding proteins (RBPs), or even be translated into proteins directly. Currently, a large body of circRNAs have been demonstrated differentially expressed in physiological and pathological processes including cancer. In lung cancer, circRNAs play multiple roles in carcinogenesis, development, and response to different therapies, indicating their potential as diagnostic and prognostic biomarkers as well as novel therapeutics. In this review, we summarize the multi-faceted functions of circRNAs in lung cancer and the underlying mechanisms, together with the possible future of these discoveries in clinical application.

CircRNAs as promising biomarker in diagnostic and prognostic of lung cancer: An updated meta-analysis

BACKGROUND

As a class of endogenous non-coding RNAs with closed-loop structure, circular RNAs (circRNAs) are receiving more and more attention. CircRNAs have been reported to be widely expressed in various human cancers and are implicated in tumorigenesis and progression. The present study aimed to systematically evaluate the clinicopathological, diagnostic and prognostic values of circRNAs in lung cancer.

METHODS

We searched literature from PubMed, Web of science, Cochrane Library, EMBASE and Ovid online databases up to May 29, 2020. Statistical analyses were undertaken based on Stata 11.0, Meta-DiSc 1.4, and RevMan 5.3 software.

RESULTS

Finally, a total of 63 eligible articles were included in our meta-analysis, including 18 studies for diagnosis, 22 studies for prognosis and 57 studies for clinicopathological features. In terms of diagnostic values, circRNAs could discriminate between lung cancer patients and the normal individuals with a relatively high pooled area under the curve (AUC) of 0.83 (95%CI, 0.80-0.86). For the prognostic values, we found that elevated expression of oncogenic circRNAs could predict poor survival outcomes based on multivariate analysis (HR = 2.430, 95%CI = 2.003-2.948, P < 0.001 for OS; HR = 2.228, 95%CI = 1.289-3.853, P = 0.004 for DFS) while tumor-suppressor circRNAs was correlated with better OS in univariate analysis (HR = 0.627, 95%CI = 0.519-0.757, P < 0.001). The pooled results suggested that elevated expression of carcinogenic circRNAs was associated with tumor size (OR = 1.676, 95%CI = 1.209-2.323, P = 0.002), smoking statue (OR = 1.260, 95%CI = 1.062-1.494, P = 0.008), TNM stage (OR = 2.345, 95%CI = 1.617-3.399, P < 0.001), differentiation grade (OR = 1.843, 95%CI = 1.228-2.765, P = 0.003), and lymphatic metastasis (OR = 2.097, 95%CI = 1.482-2.967, P < 0.001). Moreover, the expression of tumor-suppressor circRNAs was related to the improved clinicopathological features (lymphatic metastasis: OR = 0.536, 95%CI = 0.311-0.926, P = 0.025).

CONCLUSIONS

Our meta-analysis demonstrated that circRNAs could be used as feasible and important biomarkers for diagnosis, prognosis and clinicopathological features in lung cancer.

Circular RNAs: Emerging Role in Cancer Diagnostics and Therapeutics

Circular RNAs (circRNAs) are rapidly coming to the fore as major regulators of gene expression and cellular functions. They elicit their influence via a plethora of diverse molecular mechanisms. It is not surprising that aberrant circRNA expression is common in cancers and they have been implicated in multiple aspects of cancer pathophysiology such as apoptosis, invasion, migration, and proliferation. We summarize the emerging role of circRNAs as biomarkers and therapeutic targets in cancer.

Oncolytic Vaccinia Virus-Mediated Antitumor Effect and Cell Proliferation Were Promoted in PTC by Regulating circRNA_103598/miR-23a-3p/IL-6 Axis

BACKGROUND

Papillary thyroid carcinoma (PTC) is the most common type of thyroid malignancy, and cases have been rising steadily worldwide in the past few decades. Despite great progress having been made in surgery and chemotherapy for PTC, the survival rate of PTC patients has not increased significantly. Therefore, there is an urgent need to explore novel treatment strategies.

MATERIALS AND METHODS

The levels of circRNA_103598, miR-23a-3p and IL-6 mRNA in PTC tissues and cells were examined by qRT-PCR assay. Cell proliferation and IC50 values of oncolytic vaccinia virus (OVV) were detected by CCK-8 assay. A dual-luciferase reporter assay was performed to detect the relationships among circRNA_103598, miR-23a-3p and IL-6. ELISA was carried out to detect the expression of IL-6.

RESULTS

We found that circRNA_103598 was increased in PTC tissues and cell lines and acted as a sponge for miR-23a-3p. Moreover, knockdown of miR-23a-3p suppressed the OVV-mediated antitumor effect and cell proliferation in PTC. In addition, we revealed that circRNA_103598 bound to miR-23a-3p as a sponge to promote IL-6 expression.

CONCLUSION

Our study first revealed the high expression and oncogenic function of circRNA_103598 in PTC cells. Then, circRNA_103598 sponged miR-23a-3p to upregulate IL-6 expression, with the resulted that cell proliferation was promoted and the OVV-mediated antitumor effect was enhanced by strengthening the viral replication, providing new insights into future therapy for PTC.

CircRNA circ_POLA2 promotes lung cancer cell stemness via regulating the miR-326/GNB1 axis

Circular RNAs (CircRNAs) are a group of noncoding RNAs that have essential function in the development and progression of various cancers. The expression pattern and function of circRNA in lung cancer is not fully understood. In the present study, we aimed to investigate the expression profiles and underlying mechanism of circRNA circ_POLA2 in lung cancer cell stemness. Circ_POLA2 was highly expressed in lung cancer tissues and predicted a poor prognosis in lung cancer patients. Knockdown of circ_POLA2 inhibited the stemness of lung cancer cells, which is evident by the decreased sphere-formation ability, ALDH1 activity, and stemness marker expression, but had no effects on cell viability. Mechanistically, circ_POLA2 functioned as a ceRNA by sponging miR-326. Furthermore, miR-326 negatively regulated G protein subunit beta 1 (GNB1) expression by targeting its 3'-UTR (untranslated region). Intriguingly, we found that GNB1 was overexpressed and associated with poor prognosis in lung cancer patients. Overexpression of GNB1 could antagonize the inhibitory effect of circ_POLA2 knockdown on lung cancer cell stemness. In conclusion, circ_POLA2 promotes lung cancer cell stemness and progression via regulating the miR-326/GNB1 axis, which might serve as a novel therapeutic target for lung cancer patients.

Knockdown of circPRKCA Restrained Cell Growth, Migration, and Invasion of NSCLC Cells Both in vitro and in vivo via Regulating miR-330-5p/PDK1/AKT Pathway

Background

Protein kinase Cα (PRKCA) is an oncogene in multiple cancers including non-small-cell lung cancer (NSCLC) and can be transcribed into a number of circular PRKCAs (circPRKCAs). Here, we aimed to elaborate the role and mechanism of circPRKCA_024 (circPRKCA) in malignant progression of NSCLC.

Methods

Expression of circPRKCA, miRNA (miR)-330-5p and 3-phosphoinositide-dependent protein kinase-1 (PDK1) was measured by real-time quantitative PCR and Western blotting, and their relationship was testified by dual-luciferase reporter assay, RNA immunoprecipitation, and RNA pull-down assay. Cell behaviors were evaluated by cell counting kit (CCK)-8, flow cytometry, and transwell assays. AKT activity was confirmed by Western blotting. Xenograft experiment assessed tumor growth.

Results

Expression of circPRKCA and PDK1 was upregulated, and miR-330-5p was downregulated in NSCLC tissues and cell lines. High circPRKCA was correlated with TNM stage and lymph node metastasis of NSCLC patients. Silencing circPRKCA could suppress cell viability, migration, and invasion in A549 and H1299 cells, accompanied with apoptosis rate promotion. Moreover, circPRKCA knockdown retarded tumor growth of A549 cells in vivo. Molecularly, miR-330-5p was sponged by circPRKCA, and PDK1 was a target of miR-330-5p. Inhibiting miR-330-5p could attenuate the suppression of circPRKCA knockdown on cell growth, migration, and invasion; contrarily, promoting miR-330-5p caused inhibition on those cell behaviors by downregulating PDK1. Analogously, AKT activity was suppressed by circPRKCA downregulation and miR-330-5p upregulation in NSCLC cells both in vitro and in vivo.

Conclusion

Depleting circPRKCA inhibited PDK1 to suppress NSCLC cell malignant behaviors through miR-330-5p/PDK1/AKT pathway.

Circular RNAs and cancer: Opportunities and challenges

Circular RNAs (circRNAs) are covalently circularized RNA moieties that despite being relatively abundant were only recently identified and have only begun to be investigated within the last couple of years. Even though there are many thousands of genes that appear capable of producing circRNAs, and the fact that many circRNAs appear to be highly evolutionarily conserved, the function of all but a few remain to be fully explored. What has been determined, however, is that circRNAs play key regulatory roles in many aspects of biology with focus being given to their function in cancer. Most of the studies to date have found that circRNAs act as master regulator of gene expression most often than not acting to regulate levels though sequestration or "sponging" of other gene expression regulators, particularly miRNAs. They can also function directly modulating transcription, or by interfering with splicing mechanisms. Some circRNAs can also be translated into functional proteins or peptides. A combination of tissue and developmental stage specific expression along with an innate resistance to RNAse activity means that circRNAs show perhaps their greatest potential as novel biomarkers of cancer. In this chapter we consider the current state of knowledge regarding these molecules, their synthesis, function, and association with cancer. We also consider some of the challenges that remain to be overcome to allow this emerging class of RNAs to fulfill their potential in clinical practice.

Circular RNA DGKB Promotes the Progression of Neuroblastoma by Targeting miR-873/GLI1 Axis

Accumulated evidences suggested that circular RNAs (circRNA) played critical roles in tumorigenesis and progression. To our knowledge, no study reported the function of circular RNA DGKB (circDGKB, circRNA ID: hsa_circ_0133622) on progression of neuroblastoma (NB). Here, we showed that circDGKB was upregulated in NB tissues compared to the normal dorsal root ganglia. Moreover, the expression level of circDGKB was negatively correlated with the survival rate of NB patients. Mechanically, overexpression of circDGKB promoted the proliferation, migration, invasion, and tumorigenesis of NB cells and reduced cell apoptosis, and vice versa. In addition, qRT-PCR and/or Western blot results showed that circDGKB overexpression inhibited the expression level of miR-873 and enhanced GLI1 expression. Moreover, miR-873 functioned an opposite role to circDGKB and significantly weakened circDGKB role in promoting NB progression. Furthermore, GLI1 upregulation also rescued the miR-873 role in inhibiting NB progression. In conclusion, our work proved that circDGKB promoted NB progression via targeting miR-873/GLI1 axis in vitro and in vivo. Our study provided a new target for NB treatment and indicated that circDGKB could act as a novel diagnostic marker for NB.

circMET promotes NSCLC cell proliferation, metastasis, and immune evasion by regulating the miR-145-5p/CXCL3 axis

In recent years, circular RNAs (circRNAs) have been increasingly reported to play a crucial role in the proliferation, migration, and invasion of non-small-cell lung cancer (NSCLC) cells. However, the circRNA MET (circMET) oncogenic mechanism that drives NSCLC development and progression remains largely unknown. In this study, the present results demonstrated that circMET expression was significantly higher in NSCLC tissues than in peritumoral tissues using quantitative real-time polymerase chain reaction. Notably, NSCLC patients with a large tumor diameter, poor differentiation and lymphatic metastasis had high RNA levels of circMET. Moreover, high circMET expression served as an independent risk factor for short overall survival (OS) and progression-free survival (PFS) in NSCLC patients. Next, we validated that circMET overexpression can enhance NSCLC cell proliferation, metastasis, and immune evasion in vitro. Mechanistically, our study uncovers that circMET acts as a miR-145-5p sponge to upregulate CXCL3 expression. Collectively, circMET regulates the miR-145-5p/CXCL3 axis and serves as a novel, promising diagnostic and prognostic biomarker in patients with NSCLC.

Diagnostic and prognostic values of circular RNAs for lung cancer: a meta-analysis

Circular RNAs (circRNAs) may serve as potential biomarkers for patients with lung cancer. The aim of this meta-analysis was to analyse the diagnostic, prognostic and clinicopathological values of circRNAs in lung cancer patients. A systematic search of PubMed, Embase, Web of Science, Scopus and the Cochrane Library databases was performed for relevant articles from inception to 29 January 2020. Pooled parameters including sensitivity, specificity and area under the curve (AUC) were used to assess the diagnostic performance, HRs and 95% CIs were used to evaluate overall survival (OS) and ORs were used to estimate clinicopathological parameters. 52 studies from 45 articles were enrolled in this study, including 17 on diagnosis and 35 on prognosis. For diagnostic values, circRNAs could discriminate lung cancer patients from the controls, with AUC of 0.83 (95% CI: 0.79 to 0.86), a relatively high sensitivity of 0.77 (95% CI: 0.73 to 0.81) and specificity of 0.75 (95% CI: 0.71 to 0.79). For prognostic significances, overexpression of 23 upregulated circRNAs was relevant to a poor prognosis (OS: HR=2.21, 95% CI: 1.96 to 2.49, p<0.001), and overexpression of 9 downregulated circRNAs was correlated with a favourable prognosis (OS: HR=0.62, 95% CI: 0.53 to 0.73, p<0.001). As for clinicopathological parameters, high expression of 23 upregulated circRNAs was associated with unfavourable clinicopathological features while 9 downregulated circRNAs proved the contrary. In conclusion, this study confirmed that circRNAs might serve as important biomarkers for diagnostic and prognostic values of lung cancer.

circRNA-miRNA-mRNA regulatory network in human lung cancer: an update

Circular RNAs, as hopeful diagnosis markers and therapeutic molecules, have been studied, probed and applied into several diseases, such as cardiovascular diseases, systemic lupus erythematosus, leukemia, pulmonary tuberculosis, and cancer especially. Recently, mounting evidence has supported that circRNAs play a key role in the tumorigenesis, progress, invasion and metastasis in lung cancer. Its special structure—3′–5′ covalent loop—allow it to execute several special functions in both normal eukaryotic cells and cancer cells. Our review summaries the latest studies on characteristics and biogenesis of circRNAs, and highlight the regulatory functions about miRNA sponge of lung-cancer-related circRNAs. In addition, the interaction of the circRNA-miRNA-mRNA regulatory network will also be elaborated in detail in this review. Therefore, this review can provide a new idea or strategy for further development and application in clinical setting in terms of early-diagnosis and better treatment.

Critical function of circular RNAs in lung cancer

Lung cancer is one of the main causes of cancer-related death in the world, especially due to its frequency and ineffective therapeutically approaches in the late stages of the disease. Despite the recent advent of promising new targeted therapies, lung cancer diagnostic strategies still have difficulty in identifying the disease at an early stage. Therefore, the characterizations of more sensible and specific cancer biomarkers have become an important goal for clinicians. Circular RNAs (circRNAs), a type of RNA with covalently closed continuous loop structures that display high structural resistance and tissue specificity pointed toward a potential biomarker role. Current investigations have identified that circRNAs have a prominent function in the regulation of oncogenic pathways, by regulating gene expression both at transcriptional and post-transcriptional level. The aim of this review is to provide novel information regarding the implications of circRNAs in lung cancer, with an emphasis on the role in disease development and progression. Initially, we explored the potential utility of circRNAs as biomarkers, focusing on function, mechanisms, and correlation with disease progression in lung cancer. Further, we will describe the interaction between circRNAs and other non-coding species of RNA (particularly microRNA) and their biological significance in lung cancer. Describing the nature of these interactions and their therapeutic potential will provide additional insight regarding the altered molecular landscape of lung cancer and consolidate the potential clinical value of these circular transcripts. This article is categorized under: RNA Structure and Dynamics > Influence of RNA Structure in Biological Systems RNA in Disease and Development > RNA in Disease RNA in Disease and Development > RNA in Development.

High level of H3K4 tri-methylation modification predicts poor prognosis in esophageal cancer

Objectives: An increase in the trimethylation of lysine 4 of histone 3 (H3K4me3) has been reported to be involved in the development of several types of tumors. However, the level and role of H3K4me3 in human esophageal cancer (HEC) remain unknown. Here, we assessed the role and clinical significance of H3K4me3 in HEC.

Methods: The level of H3K4me3 was determined in 15 pairs of HEC and paracancerous tissues by Western blotting. A tissue microarray including samples from 100 HEC patients was analyzed by immunohistochemistry to determine the relationship between the level of H3K4me3 and the clinicopathological features of HEC patients. Then, the levels of H3K4me3 in HEC cells were elevated via knockdown of inhibitor of growth family member 4(Ing4) expression. Finally, the prognostic significance of H3K4me3 levels in HEC patients was further analyzed.

Results: We found that H3K4me3 levels were frequently elevated in HEC tissues compared with adjacent esophageal tissues, and elevated H3K4me3 was significantly associated with poor tumor differentiation (p =1.39×10-5) and advanced tumor stage (p=8.5×10-5). After Ing4 knockdown in HEC cells, we found that the cell proliferation, metastasis, invasion and colony formation abilities were enhanced compared to those in the control cells. Notably, we found that HEC patients with a high level of H3K4me3 exhibited an unfavorable 5-year survival rate compared to those with a low level of H3K4me3 (p=6.8×10-5). The univariate analysis showed that the tumor differentiation, TNM stage, and H3K4me3 level were predictors of the overall survival rate of HEC patients. In the multivariate analysis, tumor stage (p=0.015) and H3K4me3 level (p=0.034) were revealed to be independent parameters for predicting the prognosis of HEC patients.

Conclusions: Thus, high levels of H3K4me3 may be used as a meaningful biomarker for HEC prognosis evaluation.

Insights into the regulatory role of circRNA in angiogenesis and clinical implications

Angiogenesis is the physiological process of new blood vessel formation from existing capillary vessels or posterior capillary veins. Its dysfunction could result in a number of diseases, such as cardiovascular diseases and cancer, contributing to death and disability worldwide. Circular RNAs (circRNAs) are a class of novel identified RNA molecules with a special covalent loop structure without a 5' cap and 3' tail, which can lead to novel back-splicing or skipping events from precursor mRNAs. Accumulating evidence suggests that circRNA play critical roles in diseases; in particular, they are abundantly and abnormally expressed in angiogenesis-related diseases. In this review, we describe the role of circRNA under pathological conditions, discuss the association between circRNA and angiogenesis, classify the regulatory mechanisms and suggest that circRNA can be used as potential therapeutic targets for angiogenesis-related diseases under clinical evaluation.

Long non-coding RNA PSMA3-AS1 promotes malignant phenotypes of esophageal cancer by modulating the miR-101/EZH2 axis as a ceRNA

Backgrounds: Emerging evidences has demonstrated that dysregulation of long non-coding RNAs (lncRNAs) is critically involved in esophageal squamous cell carcinoma (ESCC) progression. However, the function of lncRNA PSMA3-AS1 in ESCC is unclear. Therefore, we aimed to explore the functions and potential mechanisms of PSMA3-AS1 in ESCC cells progression.

Results: Here, we found that PSMA3-AS1 expression was significantly up-regulated in ESCC tissues. Forced PSMA3-AS1 expression was correlated with tumor size, distant metastasis, and poor prognosis in ESCC patients. Functionally, PSMA3-AS1-overexpression promoted ESCC cells proliferation, invasion, and migration in vitro. Mechanistically, PSMA3-AS1 up-regulated EZH2 expression by competitively binding to miR-101.

Conclusion: PSMA3-AS1 is significantly up-regulated in ESCC tissues, and the PSMA3-AS1/miR-101/EZH2 axis plays a critical role in ESCC progression. Taken together, our results may provide promising targets for ESCC therapy.

Methods: PSMA3-AS1 and miR-101 expression were explored using qRT-PCR in ESCC tissues and cell lines. Immunohistochemistry assays were carried out to analyze EZH2 (enhancer of zeste homolog) protein expression. RIP, dual-luciferase reporter, fluorescence in situ hybridization, and biotin pull-down assays were used to detect the interactions of PSMA3-AS1, miR-101 and EZH2. The biological functions of PSMA3-AS1 in PSMA3-AS1-altered cells were explored using CCK-8, colony formation, wound healing, and transwell assays in vitro.

Effects of Galectin-1 on Biological Behavior in Cervical Cancer

Background: We previously revealed that the expression of galectin-1 (LGALS1) was significantly reduced after neoadjuvant chemotherapy treatment in cervical cancer patients. The objective of this study is to investigate the effects of LGALS1 expression on biological behaviors of cervical cancer cells.

Methods: Immunohistochemistry and immunocytochemistry were performed to detect the expression of LGALS1 in cervical cancer tissues and cells (SiHa and C33A). Western blot analysis was performed to evaluate the efficacy of lentivirus-mediated upregulation or downregulation of LGALS1 in cervical cancer cells. Cell viability and proliferation were detected by CCK-8 and BrdU assays, respectively. Annexin V-FITC/PI apoptosis detection kit was employed to measure the apoptosis of cervical cancer cells. Transwell invasion and migration assays were also conducted to explore the invasive and migratory capabilities of cervical cancer cells. The expression of apoptosis- (Bcl-2 and Bax), invasion- (MMP-2 and MMP-9), and migration-related (Fascin and Ezrin) proteins, were detected by Western blot analysis. Xenograft mouse model of cervical cancer was generated to explore whether LGALS1 overexpression could promote tumor growth in vivo.

Results: LGALS1 was overexpressed in cervical cancer tissues and cell lines compared to that in normal cervical tissues and epithelium cells. Upregulation of LGALS1 significantly promoted the cell proliferation, inhibited cell apoptosis, and enhanced the migratory and invasive abilities of both SiHa and C33A cells, whereas downregulation of LGALS1 led to the opposite results. The level of Bcl-2, MMP-2, MMP-9, Fascin, and Erzin expression was significantly upregulated in cervical cancer cells with LGALS1 overexpression, while converse results were obtained in LGALS1 knockdown cancer cells. In vivo study also showed that LGALS1 overexpression facilitated tumor growth of cervical cancer cells.

Conclusion: Overexpression of LGALS1 significantly promoted and enhanced the aggressive features of cervical cancer both in vitro and in vivo, which may be associated with high expression of Bcl-2, MMP-2, MMP-9, Fascin, and Erzin proteins.

LncRNA NNT-AS1 promotes non-small cell lung cancer progression through regulating miR-22-3p/YAP1 axis

Background

Lung cancer is the leading cause of cancer‐related mortality worldwide. Studies have demonstrated that long noncoding RNA nicotinamide nucleotide transhydrogenase‐antisense RNA1 (NNT‐AS1) functioned as an oncogene in most malignancies, including non‐small cell lung cancer (NSCLC). This study aimed to investigate the underlying mechanisms of NNT‐AS1 in NSCLC progression.

Methods

The levels of NNT‐AS1, miR‐22‐3p and Yes‐associated protein (YAP1) were detected by qRT‐PCR in NSCLC tissues and cells. Kaplan‐Meier analysis was conducted to analyze the correlation between NNT‐AS1 expression and overall survival of NSCLC patients. Cell proliferation was evaluated by MTT assay. Cell migration and invasion were assessed using transwell assay. The protein levels of YAP1 and EMT‐related proteins were detected by western blot. The molecular mechanism was predicted by starBase2.0 and validated by dual‐luciferase reporter assay or RNA pull‐down assay. Xenograft analysis was carried out to analyze tumor growth in vivo.

Results

We found that the levels of NNT‐AS1 and YAP1 were enhanced, while miR‐22‐3p expression was decreased in NSCLC tissues and cells. High NNT‐AS1 expression was correlated with poor prognosis. NNT‐AS1 knockdown impeded proliferation, migration, invasion and EMT of NSCLC cells. NNT‐AS1 targeted miR‐22‐3p, and YAP1 was a target of miR‐22‐3p in NSCLC cells. Furthermore, NNT‐AS1 facilitated the progression of NSCLC by regulating miR‐22‐3p/YAP1 axis. NNT‐AS1 knockdown repressed tumor growth in vivo.

Conclusion

NNT‐AS1 facilitated proliferation, migration, invasion and EMT of NSCLC cells by sponging miR‐22‐3p and regulating YAP1 expression, which might provide a potential biomarker and therapeutic target for NSCLC.

Non-coding RNA and lung cancer progression

Lung cancer (LC) is a major killer disease globally. This situation is further supported by yearly increase in new LC cases and its poor 5-year survival which is less than 15%. Although a large percentage of LC cases have been attributed to smoking, a considerable amount of nonsmokers also develops this disease, thereby suggesting a genetic and/or epigenetic undertone to LC development. Several growth-related genes such as epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) as well as tumor suppressor genes such as p53 have been implicated in LC pathogenesis and progression. Likewise, the genome only contains approximately 1% of coding regions. Hence, noncoding portion of the genome such as noncoding RNAs (ncRNAs) has been studied and discovered to play a cogent role in LC pathogenesis. More precisely, microRNAs (miRNAs) and long ncRNAs (lncRNAs) have been studied for decades. Posttranscriptional gene modulation function of miRNAs is well established and characterized. Likewise, the antagonizing interaction between lncRNAs and miRNAs had also been proven to further control gene expression during healthy and disease conditions like LC. More recently, renewed attention toward circular RNAs [circular RNAs (circRNAs)] study showed that circRNAs can also sponge miRNAs to modulate gene expressions too. Hence, miRNAs, lncRNAs, and circRNAs seem to function within a circuit to optimally determine which gene is needed to be upregulated or downregulated in biological system. Therefore, this review will discuss important ncRNAs, namely miRNA, lncRNA, and circRNA in LC progression. Paracrine effect of exosomal ncRNA will be also reviewed. In addition, the prospect of these ncRNAs in enhancing better LC treatment will be highlighted as well.

Identification of prognostic markers of lung cancer through bioinformatics analysis and in vitro experiments

Lung cancer is one of the most common types of cancer worldwide. Understanding the molecular mechanisms underlying the development and progression of lung cancer may improve early diagnosis, treatment and prognosis. The aim of the present study was to examine the pathogenesis of lung cancer and to identify potentially novel biomarkers. Gene expression datasets of patients with lung cancer were obtained from the Gene Expression Omnibus. Genes which were most closely associated with lung cancer (core genes) were screened by weighted gene co‑expression network analysis. In vitro cell based experiments were further utilized to verify the effects of the core genes on the proliferation of lung cancer cells, adhesion between cells and the matrix, and the associated metabolic pathways. Based on WGCNA screening, two gene modules and five core genes closely associated with lung cancer, including immunoglobulin superfamily member 10 (IGSF10) from the turquoise module, and ribonucleotide reductase regulatory subunit M2, protein regulator of cytokinesis 1, kinesin family member (KIF)14 and KIF2C from the brown module were identified as relevant. Survival analysis and differential gene expression analysis showed that there were significant differences in IGSF10 expression levels between the healthy controls and patients with lung cancer. In patients with lung cancer, IGSF10 expression was decreased, and the overall survival time of patients with lung cancer was significantly shortened. An MTT and colony formation assay showed that IGSF10‑knockout significantly increased proliferation of lung cancer cells, and Transwell assays and adhesion experiments further suggested that the adhesion between cells and the matrix was significantly increased in IGSF10‑knockout cells. Gene Set Enrichment Analysis showed that the expression level of IGSF10 was significantly associated with the activation of the integrin‑β1/focal adhesion kinase (FAK) pathway. Western blotting revealed that knockout of IGSF10 resulted in the activation of the integrin‑β1/FAK pathway, as the protein expression levels of integrin‑β1, phosphorylated (p)‑FAK and p‑AKT were significantly upregulated. Activation of the integrin‑β1/FAK pathway, following knockout of IGSF10, affected the proliferation and adhesion of lung cancer cells. Therefore, IGSF10 my serve as a potential prognostic marker of lung cancer.

hsa_circ_0062389 promotes the progression of non-small cell lung cancer by sponging miR-103a-3p to mediate CCNE1 expression

Recently, increasing evidence showed that circular RNAs (circRNAs) play critical roles in tumor progression. However, the roles of hsa_circ_0062389 in non-small cell lung cancer (NSCLC) development remain unclear. In the present study, hsa_circ_0062389 expression was significantly increased in NSCLC tissues and cell lines. High hsa_circ_0062389 expression was associated with advanced TNM stage and lymph-node metastasis. Function assays showed that hsa_circ_0062389 suppression reduced NSCLC cells proliferation and arrested cell cycle in G0/G1 phase. In mechanism, hsa_circ_0062389 directly interacted with miR-103a-3p in NSCLC, and CCNE1 acted as a target of miR-103a-3p. Furthermore, rescue assays showed that miR-103a-3p suppression or CCNE1 overexpression abolished the effects of hsa_circ_0062389 suppression on lung cancer cells progression. Therefore, our results showed that the hsa_circ_0062389/miR-103a-3p/CCNE1 axis might contribute to the tumorigenesis of NSCLC, which provided a new strategy for cancer treatment.

Circular RNA circFGFR1 promotes progression and anti-PD-1 resistance by sponging miR-381-3p in non-small cell lung cancer cells

BACKGROUND

Immune system evasion, distance tumor metastases, and increased cell proliferation are the main reasons for the progression of non-small cell lung cancer (NSCLC) and the death of NSCLC patients. Dysregulation of circular RNAs plays a critical role in the progression of NSCLC; therefore, further understanding the biological mechanisms of abnormally expressed circRNAs is critical to discovering novel, promising therapeutic targets for NSCLC treatment.

METHODS

The expression of circular RNA fibroblast growth factor receptor 1 (circFGFR1) in NSCLC tissues, paired nontumor tissues, and cell lines was detected by RT-qPCR. The role of circFGFR1 in NSCLC progression was assessed both in vitro by CCK-8, clonal formation, wound healing, and Matrigel Transwell assays and in vivo by a subcutaneous tumor mouse assay. In vivo circRNA precipitation, RNA immunoprecipitation, and luciferase reporter assays were performed to explore the interaction between circFGFR1 and miR-381-3p.

RESULTS

Here, we report that circFGFR1 is upregulated in NSCLC tissues, and circFGFR1 expression is associated with deleterious clinicopathological characteristics and poor prognoses for NSCLC patients. Forced circFGFR1 expression promoted the migration, invasion, proliferation, and immune evasion of NSCLC cells. Mechanistically, circFGFR1 could directly interact with miR-381-3p and subsequently act as a miRNA sponge to upregulate the expression of the miR-381-3p target gene C-X-C motif chemokine receptor 4 (CXCR4), which promoted NSCLC progression and resistance to anti-programmed cell death 1 (PD-1)- based therapy.

CONCLUSION

Taken together, our results suggest the critical role of circFGFR1 in the proliferation, migration, invasion, and immune evasion abilities of NSCLC cells and provide a new perspective on circRNAs during NSCLC progression.