Hsa_circ_0003998 promotes cell proliferation and invasion by targeting miR-326 in non-small cell lung cancer

Circular RNAs in EMT-driven metastasis regulation: modulation of cancer cell plasticity, tumorigenesis and therapy resistance

The non-coding RNAs comprise a large part of human genome lack of capacity in encoding functional proteins. Among various members of non-coding RNAs, the circular RNAs (circRNAs) have been of importance in the pathogenesis of human diseases, especially cancer. The circRNAs have a unique closed loop structure and due to their stability, they are potential diagnostic and prognostic factors in cancer. The increasing evidences have highlighted the role of circRNAs in the modulation of proliferation and metastasis of cancer cells. On the other hand, metastasis has been responsible for up to 90% of cancer-related deaths in patients, requiring more investigation regarding the underlying mechanisms modulating this mechanism. EMT enhances metastasis and invasion of tumor cells, and can trigger resistance to therapy. The cells demonstrate dynamic changes during EMT including transformation from epithelial phenotype into mesenchymal phenotype and increase in N-cadherin and vimentin levels. The process of EMT is reversible and its reprogramming can disrupt the progression of tumor cells. The aim of current review is to understanding the interaction of circRNAs and EMT in human cancers and such interaction is beyond the regulation of cancer metastasis and can affect the response of tumor cells to chemotherapy and radiotherapy. The onco-suppressor circRNAs inhibit EMT, while the tumor-promoting circRNAs mediate EMT for acceleration of carcinogenesis. Moreover, the EMT-inducing transcription factors can be controlled by circRNAs in different human tumors.

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.

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.

Colon cancer transcriptome

Over the last four decades, methodological innovations have continuously changed transcriptome profiling. It is now feasible to sequence and quantify the transcriptional outputs of individual cells or thousands of samples using RNA sequencing (RNA-seq). These transcriptomes serve as a connection between cellular behaviors and their underlying molecular mechanisms, such as mutations. This relationship, in the context of cancer, provides a chance to unravel tumor complexity and heterogeneity and uncover novel biomarkers or treatment options. Since colon cancer is one of the most frequent malignancies, its prognosis and diagnosis seem to be critical. The transcriptome technology is developing for an earlier and more accurate diagnosis of cancer which can provide better protectivity and prognostic utility to medical teams and patients. A transcriptome is a whole set of expressed coding and non-coding RNAs in an individual or cell population. The cancer transcriptome includes RNA-based changes. The combined genome and transcriptome of a patient may provide a comprehensive picture of their cancer, and this information is beginning to affect treatment decision-making in real-time. A full assessment of the transcriptome of colon (colorectal) cancer has been assessed in this review paper based on risk factors such as age, obesity, gender, alcohol use, race, and also different stages of cancer, as well as non-coding RNAs like circRNAs, miRNAs, lncRNAs, and siRNAs. Similarly, they have been examined independently in the transcriptome study of colon cancer.

The Tumorigenic Role of Circular RNA-MicroRNA Axis in Cancer

Circular RNAs (circRNAs) are a class of endogenous RNAs that control gene expression at the transcriptional and post-transcriptional levels. Recent studies have increasingly demonstrated that circRNAs act as novel diagnostic biomarkers and promising therapeutic targets for numerous cancer types by interacting with other non-coding RNAs such as microRNAs (miRNAs). The miRNAs are presented as crucial risk factors and regulatory elements in cancer by regulating the expression of their target genes. Some miRNAs are derived from transposable elements (MDTEs) that can transfer their location to another region of the genome. Genetic interactions between miRNAs and circular RNAs can form complex regulatory networks with various carcinogenic processes that play critical roles in tumorigenesis and cancer progression. This review focuses on the biological regulation of the correlative axis among circular RNAs, miRNAs, and their target genes in various cancer types and suggests the biological importance of MDTEs interacting with oncogenic or tumor-suppressive circRNAs in tumor progression.

Integration of TE Induces Cancer Specific Alternative Splicing Events

Alternative splicing of messenger RNA (mRNA) precursors contributes to genetic diversity by generating structurally and functionally distinct transcripts. In a disease state, alternative splicing promotes incidence and development of several cancer types through regulation of cancer-related biological processes. Transposable elements (TEs), having the genetic ability to jump to other regions of the genome, can bring about alternative splicing events in cancer. TEs can integrate into the genome, mostly in the intronic regions, and induce cancer-specific alternative splicing by adjusting various mechanisms, such as exonization, providing splicing donor/acceptor sites, alternative regulatory sequences or stop codons, and driving exon disruption or epigenetic regulation. Moreover, TEs can produce microRNAs (miRNAs) that control the proportion of transcripts by repressing translation or stimulating the degradation of transcripts at the post-transcriptional level. Notably, TE insertion creates a cancer-friendly environment by controlling the overall process of gene expression before and after transcription in cancer cells. This review emphasizes the correlative interaction between alternative splicing by TE integration and cancer-associated biological processes, suggesting a macroscopic mechanism controlling alternative splicing by TE insertion in cancer.

Immunomodulatory functions of the circ_001678/miRNA-326/ZEB1 axis in non-small cell lung cancer via the regulation of PD-1/PD-L1 pathway

High-throughput circRNA sequencing identified circRNA_001678 (circ_001678) as an upregulated circRNA in NSCLC tissues. Hence, the current study sought to investigate the function and the underlying mechanism of circRNA_001678 in immune escape of NSCLC. Briefly, commercially purchased NSCLC cell lines were adopted for in vitro experiment to evaluate the effects of circ_001678 over-expression or knockdown on cell biological functions, including proliferation, migration, and invasive abilities. In addition, the effects of circ_001678 on the in vivo tumorigenicity ability were evaluated for verification. Accordingly, we uncovered that circ_001678 over-expression augmented NSCLC progression in vitro and enhanced tumorigenicity ability in vivo. The interaction between circ_001678 and miR-326 predicted online was verified by means of luciferase and RNA pull-down assays. Furthermore, circ_001678 could sponge miR-326 to up-regulate ZEB1. On the other hand, the tumor-promoting effects of circ_001678 could be inhibited by anti-PD-L1/PD-1 treatment. Mechanistically, circ_001678 led to the activation of the PD-1/PD-L1 pathway to promote CD8+ T cell apoptosis, thereby inducing NSCLC cell immune escape via regulation of the miR-326/ZEB1 axis. To conclude, our findings revealed that circ_001678 sponges miR-326 to up-regulate ZEB1 expression and induce the PD-1/PD-L1 pathway-dependent immune escape, thereby promoting the malignant progression of NSCLC.

circBIRC6 contributes to the development of non-small cell lung cancer via regulating microRNA-217/amyloid beta precursor protein binding protein 2 axis

Background:

Circular RNAs (circRNAs) are considered to be important regulators in cancer biology. In this study, we focused on the effect of circRNA baculoviral inhibitor of apoptosis protein (IAP) repeat containing 6 (circBIRC6) on non-small cell lung cancer (NSCLC) progression.

Methods:

The NSCLC and adjacent non-tumor tissues were collected at Shanghai Ninth People's Hospital. Quantitative real-time polymerase chain reaction was conducted for assessing the levels of circBIRC6, amyloid beta precursor protein binding protein 2 (APPBP2) messenger RNA (mRNA), baculoviral IAP repeat containing 6 mRNA (BIRC6), and microRNA-217 (miR-217). Western blot assay was adopted for measuring the protein levels of APPBP2, E-cadherin, N-cadherin, and vimentin. Colony formation assay, transwell assay, and flow cytometry analysis were utilized for evaluating cell colony formation, metastasis, and apoptosis. Dualluciferase reporter assay and RNA immunoprecipitation assay were carried out to determine the interaction between miR-217 and circBIRC6 and APPBP2 in NSCLC tissues. The murine xenograft model assay was used to investigate the function of circBIRC6 in tumor formation in vivo. Differences were analyzed via Student's t test or one-way analysis of variance. Pearson's correlation coefficient analysis was used to analyze linear correlation.

Results:

CircBIRC6 was overexpressed in NSCLC tissues and cells. Knockdown of circBIRC6 repressed the colony formation and metastasis and facilitated apoptosis of NSCLC cells in vitro and restrained tumorigenesis in vivo. Mechanically, circBIRC6 functioned as miR-217 sponge to promote APPBP2 expression in NSCLC cells. MiR-217 inhibition rescued circBIRC6 knockdown-mediated effects on NSCLC cell colony formation, metastasis, and apoptosis. Overexpression of miR-217 inhibited the malignant phenotypes of NSCLC cells, while the effects were abrogated by elevating APPBP2.

Conclusion:

CircBIRC6 aggravated NSCLC cell progression by elevating APPBP2 via sponging miR-217, which might provide a fresh perspective on NSCLC therapy.

Hsa_circ_0020850 promotes the malignant behaviors of lung adenocarcinoma by regulating miR-326/BECN1 axis

Background

Circular RNAs (circRNAs) are a novel type of endogenous RNAs and play vital roles in lung adenocarcinoma. However, the function and underlying mechanism of circ_0020850 in lung adenocarcinoma remain unknown.

Methods

The levels of circ_0020850, microRNA-326 (miR-326), and Beclin1 (BECN1) were analyzed by real-time quantitative polymerase chain reaction and western blot analyses. The migration and invasion were determined by wound healing and transwell assays, respectively. Colony formation assay was used to assess cell proliferation ability. The angiogenic ability was analyzed by Matrigel angiogenesis assay. The apoptosis rate was calculated by flow cytometry assay. Dual-luciferase reporter, RNA immunoprecipitation (RIP), and RNA pull-down assays were conducted to confirm the interaction relationship among circ_0020850, miR-326, and BECN1. A xenograft mice model was established to assess the role of circ_0020850 in vivo.

Results

We found that circ_0020850 was obviously overexpressed in lung adenocarcinoma tissues and cells. Knockdown of circ_0020850 inhibited migration, invasion, proliferation, and angiogenesis but induced apoptosis in lung adenocarcinoma cells in vitro, as well as curbed tumor growth in vivo. MiR-326 was a target of circ_0020850, and knockdown of miR-326 abolished the suppression effect of circ_0020850 on the malignant behaviors of lung adenocarcinoma cells. Additionally, miR-326 could negatively regulate BECN1 expression, thereby regulating lung adenocarcinoma cell phenotypes. Importantly, circ_0020850 could directly bind to miR-326 and thus relieve miR-326-mediated inhibition on BECN1.

Conclusion

Circ_0020850 promoted the malignant development of lung adenocarcinoma by regulating miR-326/BECN1 axis, indicating that circ_0020850 might serve as a promising target for the diagnosis and treatment of lung adenocarcinoma patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02480-3.

Dissecting the Role of Circular RNAs in Sarcomas with Emphasis on Osteosarcomas

Circular RNAs (circRNAs) are single-stranded RNAs generated from exons back-splicing from a single pre-mRNA, forming covalently closed loop structures which lack 5'-3'-polarity or polyadenylated tail. Ongoing research depicts that circRNAs play a pivotal role in tumorigenesis, tumor progression, metastatic potential and chemoresistance by regulating transcription, microRNA (miRNA) sponging, RNA-binding protein interactions, alternative splicing and to a lesser degree, protein coding. Sarcomas are rare malignant tumors stemming from mesenchymal cells. Due to their clinically insidious onset, they often present at advanced stage and their treatment may require aggressive chemotherapeutic or surgical options. This review is mainly focused on the regulatory functions of circRNAs on osteosarcoma progression and their potential role as biomarkers, an area which has prompted lately extensive research. The attributed oncogenic role of circRNAs on other mesenchymal tumors such as Kaposi Sarcoma (KS), Rhabdomyosarcoma (RMS) or Gastrointestinal Stromal Tumors (GISTs) is also described. The involvement of circRNAs on sarcoma oncogenesis and relevant emerging diagnostic, prognostic and therapeutic applications are expected to gain more research interest in the future.

MicroRNA-326 impairs chemotherapy resistance in non small cell lung cancer by suppressing histone deacetylase SIRT1-mediated HIF1α and elevating VEGFA

Compelling evidence has implicated the role of microRNAs (miRs or miRNAs) in lung cancer. Sirtuin-1 (SIRT1) is key contributor to the progression of non small cell lung cancer (NSCLC). This study was intended to investigate whether miR-326 affected NSCLC associated with SIRT1. miR-326 and SIRT1 expression in H460 cells and chemoresistant cells H460-R was measured by RT-qPCR. Dual luciferase reporter gene assay and RIP assay were used to identify and validate the relationship between miR-326 and SIRT1. Using gain- and loss-of-function approaches, we evaluated their effects on the chemoresistance of NSCLC cells. ChIP assay was used to detect binding of SIRT1 to the promoter of HIF1α gene, and the binding H3K9Ac to HIF1α, binding of H3K9Ac and HIF1α after silencing SIRT1, and binding HIF1α to VEGFA promoter. In vivo experiments were performed to validate the in vitro findings. MiR-326 expression was decreased while SIRT1 expression was increased in NSCLC cells. SIRT1 was a target of miR-326. MiR-326 inhibited the proliferation of chemotherapy-resistant NSCLC cells and promoted their apoptosis by suppressing SIRT1. In addition, SIRT1 promoted chemoresistance of NSCLC cell by elevating VEGFA expression. Through this mechanism, miR-326 reduced the chemoresistance, which was validated in vivo. Taken together, miR-326 represses SIRT1 through impeding HIF1α expression, thus hindering chemotherapy resistance in lung cancer. These findings provide an exquisite therapeutic target for NSCLC.

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.

Mechanisms of circular RNA circ_0066147 on pancreatic cancer progression

Background

The purpose of the study was to explore the precise parts of circ_0066147 (circular RNA [circRNA] scm-like with four mbt domains 1, circSFMBT1) in pancreatic cancer (PC) progression.

Methods

Ribonuclease R assay was used to confirm the stability of circ_0066147. circ_0066147, miR-326 and E2F transcription factor 2 (E2F2) expression levels was detected by quantitative reverse-transcription polymerase chain reaction or Western blot. Cell proliferation, apoptosis, migration and invasion abilities were assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide, flow cytometry, wound-healing and transwell assays, respectively. Targeted relationships among circ_0066147, miR-326 and E2F2 were verified by the dual-luciferase reporter or RNA pull-down assay.

Results

circ_0066147 expression was upregulated in PC tissues and cells. circ_0066147 knockdown inhibited PC cell proliferation, migration, invasion and enhanced apoptosis in vitro, as well as weakened tumor growth in vivo. Mechanistically, circ_0066147 directly targeted miR-326 and circ_0066147 modulated E2F2 expression by miR-326. miR-326 mediated the regulation of circ_0066147 in PC cell behaviors in vitro. Furthermore, E2F2 was a functional target of miR-326 in modulating PC cell behaviors in vitro.

Conclusion

circ_0066147 regulated PC malignant progression in part depending on the miR-326/E2F2 axis, illuminating circ_0066147 was a potential prognostic marker and therapeutic target for PC management.

hsa_circ_0058357 acts as a ceRNA to promote non‑small cell lung cancer progression via the hsa‑miR‑24‑3p/AVL9 axis

Abnormal circular RNAs (circRNAs) are associated with biological processes in cancer; however, the function of circRNAs remains largely unknown in non-small cell lung cancer (NSCLC). The present study aimed to investigate the role of hsa_circ_0058357 on the progression of NSCLC. Cell proliferation, migration and apoptosis were determined using Cell Counting Kit-8, Transwell and flow cytometry assays, respectively. Gene [circRNA and microRNA (miR)] and protein expression levels were determined via reverse transcription-quantitative PCR and immunoblotting. A luciferase assay was employed to detect the binding of miR-24-3p with AVL9 cell migration associated (AVL9), while a cancer xenograft model was established to evaluate cancer growth in vivo. The results demonstrated that hsa_circ_0058357 was highly expressed in human NSCLC tissues and NSCLC cells compared with para-cancerous tissues and human bronchial epithelial (HBE) cells, respectively. Knockdown of hsa_circ_0058357 significantly suppressed cell viability, migration and tumor growth, while it promoted apoptosis in NSCLC cells. As a competing endogenous RNA, hsa_circ_0058357 knockdown contributed to the increase of miR-24-3p expression in NSCLC cells. Of note, overexpression of miR-24-3p markedly abolished the exogenous hsa_circ_0058357-induced excessive proliferation, migration and apoptosis resistance of NSCLC cells. Mechanistically, as a signaling molecule in late secretory pathway, AVL9 was also expressed at a high level in NSCLC tissues and cells, which could be directly suppressed by miR-24-3p. In the tumor tissues, along with growth inhibition, hsa_circ_0058357 knockdown also mediated the elevation of miR-24-3p and the reduction of AVL9. Thus, it was suggested that hsa_circ_0058357 may be a crucial regulation factor in NSCLC by sponging hsa-miR-24-3p, leading to a decrease in miR-24-3p expression, and subsequent increase in AVL9 expression. Therefore, hsa_circ_0058357 may serve as a potential target for diagnosis and gene therapy for NSCLC.

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.

Circ_0003998 Regulates the Progression and Docetaxel Sensitivity of DTX-Resistant Non-Small Cell Lung Cancer Cells by the miR-136-5p/CORO1C Axis

Background:

Drug resistance in cancer cells is a major challenge for anti-cancer therapy. Circular RNA (circRNA) circ_0003998 has been identified as an important regulator in the chemoresistance development of non-small cell lung cancer (NSCLC). The purpose of this study was to investigate the molecular basis underlying the resistance control of circ_0003998 in NSCLC.

Methods:

The levels of circ_0003998, miR-136-5p and coronin 1C (CORO1C) were gauged by the quantitative real-time polymerase chain reaction (qRT-PCR) or western blot. Cell viability, colony formation and apoptosis were evaluated by the Cell Counting Kit-8 (CCK-8), colony formation and flow cytometry assays, respectively. Targeted relationships among circ_0003998, miR-136-5p and CORO1C were confirmed by the dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Animal studies were performed to evaluate the function of circ_0003998 in vivo.

Results:

Our data indicated that circ_0003998 expression was associated with NSCLC resistance to docetaxel (DTX). The knockdown of circ_0003998 promoted DTX sensitivity, suppressed cell colony formation, and enhanced cell apoptosis of A549/DTX and H1299/DTX cells in vitro. Moreover, circ_0003998 knockdown hampered tumor growth and enhanced DTX sensitivity in vivo. Mechanistically, circ_0003998 directly targeted miR-136-5p, and miR-136-5p was a molecular mediator of circ_0003998 function in vitro. Furthermore, CORO1C was a functionally important target of miR-136-5p in regulating DTX-resistant NSCLC cell colony formation, apoptosis and DTX sensitivity in vitro. Additionally, circ_0003998 modulated CORO1C expression by working as a miR-136-5p sponge.

Conclusion:

Our present work identified that circ_0003998 regulated DTX-resistant NSCLC cell colony formation, apoptosis and DTX sensitivity at least partially by controlling CORO1C expression by sponging miR-136-5p, illuminating a rationale for developing circ_0003998 as a therapeutic target of chemoresistant NSCLC.

Propofol suppresses non-small cell lung cancer tumorigenesis by regulation of circ-RHOT1/miR-326/FOXM1 axis

BACKGROUND

Lung cancer is a common malignant tumor around the world. Propofol has been found to play an anti-tumor role. Therefore, the purpose of this study is to clarify the role and underlying molecular mechanisms of Propofol in non-small cell lung cancer (NSCLC).

METHODS

The real-time quantitative polymerase chain reaction (RT-qPCR) assay was conducted to measure the expression levels of circular_RHOT1 (circ-RHOT1), microRNA (miR)-326, and Forkhead Box M1 (FOXM1) in tissues and cells. The proliferation of cell was determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazol-3-ium bromide (MTT) and colony forming assays. The flow cytometry assay was used to evaluate cell apoptosis. The migration and invasion of NSCLC cells were determined by transwell assay. The protein expression level of FOXM1 was quantified by western blot assay. The association between miR-326 and circ-RHOT1 or FOXM1 was confirmed by dual-luciferase reporter assay.

RESULTS

Circ-RHOT1 was increased in NSCLC tissues and cells. Importantly, treatment with Propofol inhibited circ-RHOT1 expression in NSCLC cells. Propofol dose-dependently inhibited proliferation, migration and invasion while induced apoptosis of NSCLC cells, which was abolished by circ-RHOT1 overexpression, FOXM1 overexpression, or miR-326 silencing. MiR-326, interacted with FOXM1, was a target of circ-RHOT1 in NSCLC cells, which was confirmed by dual-luciferase reporter assay. Circ-RHOT1 regulated FOXM1 expression by sponging miR-326 in NSCLC cells. In addition, inhibition of circ-RHOT1 in combined with Propofol impeded tumorigenesis in vivo.

CONCLUSION

Propofol repressed proliferation, migration and invasion while induced apoptosis of NSCLC cells at least in part by regulation of circ-RHOT1/miR-326/FOXM1 axis in NSCLC cells.

Circ_0003998 enhances doxorubicin resistance in hepatocellular carcinoma by regulating miR-218-5p/EIF5A2 pathway

BACKGROUND

The involvement of circular RNAs (circRNAs) in chemoresistance of tumors has been identified. Herein, this study aims to investigate the role and the underlying mechanism of circ_0003998 in doxorubicin (DOX) resistance in hepatocellular carcinoma (HCC).

METHODS

The expression of circ_0003998 and microRNA (miR)-218-5p and eukaryotic translation initiation factor 5A-2 (EIF5A2) mRNA was detected using quantitative real-time polymerase chain reaction. Cell viability, migration and invasion were analyzed using cell counting kit-8, colony formation and transwell assay, respectively. The levels of matrix metallopeptidase 9 (MMP-9), E-cadherin, Vimentin, N-cadherin and EIF5A2 protein were detected using western blot. The interaction between miR-218-5p and circ_0003998 or EIF5A2 was confirmed by dual-luciferase reporter assay. In vivo experiments were performed using murine xenograft models.

RESULTS

Circ_0003998 was elevated in HCC tissues, DOX-resistant tissues and cells, and circ_0003998 knockdown promoted DOX-sensitivity in HCC by inhibiting resistant cell viability, migration, invasion and EMT in vitro and enhanced DOX cytotoxicity in vivo. Bioinformatics analysis revealed circ_0003998 inhibited miR-218-5p expression, which was clarified to be a target of circ_0003998, and circ_0003998 knockdown sensitized HCC cell to DOX by sponging miR-218-5p. EIF5A2 was a target of miR-218-5p, and miR-218-5p mitigated DOX resistance in HCC cells through modulating EIF5A2 expression. Additionally, circ_0003998 served as a competing endogenous RNA for miR-218-5p to regulate EIF5A2 expression.

CONCLUSION

Circ_0003998 knockdown sensitized HCC cell to DOX by regulating miR-218-5p/EIF5A2 axis, indicating new markers of poor response to DOX and potential therapeutic strategies for the chemotherapy of HCC.

TMPO-AS1, a Novel E2F1-Regulated lncRNA, Contributes to the Proliferation of Lung Adenocarcinoma Cells via Modulating miR-326/SOX12 Axis

Background

TMPO-AS1, an antisense lncRNA located at human chromosome 12p23.1, has been identified as an oncogene involved in cell proliferation in various cancers, including LUAD. In this study, we aimed to explore the novel molecular mechanism of TMPO-AS1 underlying LUAD growth.

Materials and Methods

The transcription levels of TMPO-AS1, miR-326, and SOX12 in LUAD tissues and cell lines were detected by quantitative real-time PCR (qRT-PCR). The cell proliferation ability was evaluatect 3d by cell counting kit-8 (CCK-8) assay. Cell cycle and apoptosis analysis was assessed by flow cytometry. The target relationship among TMPO-AS1, miR-326, and SOX12 and promoter activity of TMPO-AS1 was measured using dual-luciferase reporter assay. The protein levels of SOX12 in LUAD cells were determined by Western blot. ChIP-qPCR assay was performed to validate the direct binding between E2F1 and TMPO-AS1 promoter.

Results

TMPO-AS1 was up-regulated in LUAD tissues as well as cell lines. Boosted TMPO-AS1 expression was positively correlated with poor prognosis and pathological stage in LUAD. Down-regulation of TMPO-AS1 could restrain the proliferation of LUAD cells through arresting the cell cycle at G0/G1 phase and inducing apoptosis in vitro. Mechanically, we demonstrated that TMPO-AS1 could modulate the proliferation of LUAD cells through increasing SOX12 expression level via sponging miR-326 in accordance with bioinformatics analysis and experimental validation. Furthermore, we identified that TMPO-AS1 could be activated by E2F transcription factor 1 (E2F1) as a novel target gene.

Conclusion

TMPO-AS1 can modulate LUAD cell proliferation through E2F1/miR-326/SOX12 pathway.

CircRNA circ_POLA2 Promotes Cervical Squamous Cell Carcinoma Progression via Regulating miR-326/GNB1

Circular RNAs (circRNAs) are a group of non-coding RNAs that have an essential function in the development and progression of various cancers. The expression pattern and function of circRNA in cervical squamous cell carcinoma (CESC) are not fully understood. In the present study, we aimed to investigate the expression profiles and regulation mechanism of circRNA circ_POLA2 in CESC. Circ_POLA2 was highly expressed in CESC tissues and positively correlated with poor prognosis in CESC patients. Knockdown of circ_POLA2 using shRNA inhibited cervical cancer cell proliferation, migration, and invasion both in vitro and in vivo. Mechanistically, circ_POLA2 could sponge endogenous microRNA-326 (miR-326) and inhibit its expression. Furthermore, miR-326 negatively regulated G protein subunit beta 1 (GNB1) by targeting its 3'-UTR. Intriguingly, we found that GNB1 was overexpressed and associated with poor prognosis in CESC patients. Overexpression of GNB1 could antagonize the inhibitory effect of miR-326 on cervical cancer cell proliferation, migration, and invasion. In addition, we demonstrated that circ_POLA2/miR-326/GNB1 axis regulated ERK signaling. In conclusion, circ_POLA2 promotes cervical squamous cell carcinoma development and progression via regulating the miR-326/GNB1 axis, which might serve as a novel therapeutic target for CESC patients.

Value of circular RNA 0007385 in disease monitoring and prognosis estimation in non-small-cell lung cancer patients

Objective

This study aimed to assess the circular RNA_0007385 (hsa_circ_0007385) expression in tumor/adjacent non‐tumor tissues, and the correlation of its tumor expression with clinicopathological features as well as survival in non–small‐cell lung cancer (NSCLC) patients.

Methods

210 NSCLC patients who underwent tumor resection were reviewed in this retrospective study. 210 tumor specimens and 81 paired adjacent specimens were collected, in which the hsa_circ_0007385 expression was detected by reverse transcription‐quantitative polymerase chain reaction assay. Disease‐free survival (DFS) and overall survival (OS) were recorded, and the last follow‐up date was June 30, 2019.

Results

Hsa_circ_0007385 was upregulated in tumor tissue compared with adjacent non‐tumor tissue (P < .001), and ROC curve analysis revealed that hsa_circ_0007385 expression had an excellent value in distinguishing tumor tissue from adjacent non‐tumor tissue with an area under curve of 0.922 (95% CI: 0.890‐0.953). Tumor hsa_circ_0007385 high expression correlated with lymph node metastasis (P = .007) and higher TNM stage (P = .004). In addition, DFS (P = .028) and OS (P = .008) were both less favorable in patients with tumor hsa_circ_0007385 high expression compared to patients with tumor hsa_circ_0007385 low expression. Besides, the DFS (P = .008) and OS (P = .012) were also the worst in patients with tumor hsa_circ_0007385 high+++ expression, followed by patients with tumor hsa_circ_0007385 high++ expression and patients with tumor hsa_circ_0007385 high + expression, and the best in patients with tumor hsa_circ_0007385 low expression. Multivariate regression analysis elucidated that tumor hsa_circ_0007385 high expression independently predicted worse OS (P = .033).

Conclusion

Tumor hsa_circ_0007385 could be a novel biomarker for disease monitoring and prognosis prediction in NSCLC patients.

A Novel Circular RNA hsa_circRPPH1_015 Exerts an Oncogenic Role in Breast Cancer by Impairing miRNA-326-Mediated ELK1 Inhibition

Background: Breast cancer (BC) represents a heterogeneous disease with distinct subtypes and high tumor metastatic potentials. Recent researchers identify the implication of circular RNAs (circRNAs) in the initiation of BC. Herein, we uncover a novel circRNA hsa_circRPPH1_015 as a tumor promoter in BC.

Methods: A total of 86 paired cancerous and non-cancerous tissues were surgically resected and collected from BC patients. Cell proliferation, colony formation, and cell invasion were examined by Edu staining, clone formation assays, propidium iodide (PI)-labeled flow cytometry, and Transwell invasion assays. PCNA, Ki67, MMP-2, MMP-9, Cyclin D1, and CDK4 expression was assayed using Western blot analysis. RNA pull-down, dual-luciferase reporter gene assay, and RNA binding protein immunoprecipitation (RIP) assay were performed to investigate the relationships among hsa_circRPPH1_015, microRNA-326 (miR-326), and ELK1. The tumor growth of human BC MCF-7 cells in vivo was evaluated in nude mice by subcutaneous xenografts of MCF-7 cells.

Results: hsa_circRPPH1_015 expression was upregulated in BC tissues. Knockdown of hsa_circRPPH1_015 restrained the aggressive behavior of MCF-7. hsa_circRPPH1_015 could bind to miRNA-326 that negatively regulates ELK1. Elevation of miRNA-326 expression resulted in inhibition of cell proliferation, colony formation, and cell invasion of MCF-7. Disturbance of miRNA-326 or overexpression of ELK1 restored the proliferation and aggressiveness in hsa_circRPPH1_015-depleted MCF-7 cells. Tumor growth of MCF-7 cells in vivo was reduced in nude mice lack of endogenous hsa_circRPPH1_015 expression.

Conclusion: Overall, the present study demonstrates that hsa_circRPPH1_015 was an oncogene and unfavorable prognostic factor in BC, providing an exquisite therapeutic target for BC.

Hsa_circ_0003998 promotes epithelial to mesenchymal transition of hepatocellular carcinoma by sponging miR-143-3p and PCBP1

BACKGROUND

Circular RNAs (circRNAs) play a critical regulatory role in cancer progression. However, the underlying mechanisms of circRNAs in hepatocellular carcinoma (HCC) metastasis remain mostly unknown.

METHODS

Has_circ_0003998 (circ0003998) was identified by RNAs sequencing in HCC patients with /without portal vein tumor thrombus (PVTT) metastasis. The expression level of circ0003998 was further detected by in situ hybridization on tissues microarray (ISH-TMA) and qRT-PCR in 25 HCC patients with PVTT metastasis. Moreover, the 25 HCC patients with PVTT metastasis and 50 HCC patients without PVTT metastasis were recruited together to analyze the correlation between circ0003998 expression and HCC clinical characteristics. Transwell, migration and CCK8 assays, as well as nude mice model of lung or liver metastasis were used to evaluate the role of circ0003998 in epithelial to mesenchymal transition (EMT) in HCC. The regulatory mechanisms of circ0003998 in miR-143-3p and PCBP1 were determined by dual-luciferase reporter assay, nuclear-cytoplasmic fractionation, fluorescent in situ hybridization, RNA pull- down, microRNA sequence, western blot and RNA immunoprecipitation.

RESULTS

Compared with adjacent normal liver tissues (ANL), circ0003998 expression was significantly upregulated in PVTT tissues and HCC tissues, and its expression correlates with the aggressive characteristics of HCC patients. Further assays suggested that circ0003998 promoted EMT of HCC both in vitro and in vivo. Mechanistically, our data indicated that circ0003998 may act as a ceRNA (competing endogenous RNA) of microRNA-143-3p to relieve the repressive effect on EMT-related stimulator, FOSL2; meanwhile, circ0003998 could bind with PCBP1-poly(rC) binding protein 1 (PCBP1) to increase the expression level of EMT-related genes, CD44v6.

CONCLUSION

Circ0003998 promotes EMT of HCC by circ0003998/miR-143-3p/FOSL2 axis and circ0003998 /PCBP1/CD44v6 axis.

The circRNA circIFI30 promotes progression of triple-negative breast cancer and correlates with prognosis

Growing evidence suggests that circRNAs exert a critical role in tumorigenesis and cancer progression. To date, the molecular mechanisms underlying circRNAs in triple-negative breast cancer (TNBC) are still poorly known. Here, circRNA expression profile was investigated by RNA sequencing in TNBC tissues and matched para-carcinoma tissues. We found that circIFI30 was significantly up-regulated in TNBC tissues and cells using quantitative real-time PCR and in situ hybridization. High circIFI30 expression was positively correlated with clinical TNM stage, pathological grade and poor prognosis of TNBC patients. Functionally, a series of in vivo and in vitro experiments showed that knockdown of circIFI30 could markedly inhibit TNBC cell proliferation, migration, invasion and cell cycle progression, induce apoptosis as well as suppress tumorigenesis and metastasis. Up-regulation of circIFI30 exerted an opposite effect. Mechanistically, we demonstrated that circIFI30 might act as a competing endogenous RNA (ceRNA) of miR-520b-3p to abolish the suppressive effect on target gene CD44 by fluorescent in situ hybridization (FISH), dual luciferase reporter assay, RNA immunoprecipitation and RNA pull-down assays. Therefore, our work uncovers the mechanism by which circIFI30 could promote TNBC progression through circIFI30/miR-520b-3p/CD44 axis and circIFI30 could be a novel diagnostic/prognostic marker and therapeutic target for TNBC patients.

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.

Sevoflurane Inhibits Proliferation, Invasion, but Enhances Apoptosis of Lung Cancer Cells by Wnt/β-catenin Signaling via Regulating lncRNA PCAT6/miR-326 Axis

Sevoflurane was frequently used as a volatile anesthetic in cancer surgery. However, the potential mechanism of sevoflurane on lung cancer remains largely unclear. In this study, lung cancer cell lines (H446 and H1975) were treated by various concentrations of sevoflurane. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assessment and colony formation assay were performed to detect the cell viability and proliferation, separately. Also, transwell assay or flow cytometry assay was applied as well to evaluate the invasive ability or apoptosis in lung cancer cells, respectively. Western blot assay was employed to detect the protein levels of β-catenin and Wnt5a. Moreover, quantitative real-time polymerase chain reaction (qRT-PCR) was used to examine the expression level of prostate cancer-associated transcript 6 (PCAT6) and miR-326 in lung cancer tissues and cells. The target interaction between miR-326 and PCAT6 or Wnt5a was predicted by bioinformatics analysis and verified by the dual-luciferase reporter gene assay. Sevoflurane inhibited the abilities on viability, proliferation, invasion, and activation of Wnt/β-catenin signaling, but promoted apoptosis of H446 and H1975 cells in a dose-dependent manner. The expression of PCAT6 was increased in lung cancer tissues and cells, except for that of miR-326. Besides, sevoflurane could lead to expressed limitation of PCAT6 or improvement of miR-326. This process presented a stepwise manner. Up-regulation of PCAT6 restored the suppression of sevoflurane on abilities of proliferation, invasion, rather than apoptosis, and re-activated the Wnt5a/β-catenin signaling in cells. Moreover, the putative binding sites between miR-326 and PCTA6 or Wnt5a were predicted by starBase v2.0 software online. PCAT6 suppressing effects on cells could be reversed by pre-treatment with miR-326 vector. The promotion of Wnt5a inverted effects led from miR-326 or sevoflurane. Our study indicated that sevoflurane inhibited the proliferation, and invasion, but enhanced the apoptosis in lung cancer cells by regulating the lncRNA PCAT6/miR-326/Wnt5a/β-catenin axis.

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.

STAT3-induced upregulation of circCCDC66 facilitates the progression of non-small cell lung cancer by targeting miR-33a-5p/KPNA4 axis

Emerging evidence has manifested the critical effect of abnormally expressed circular RNAs (circRNAs) on the initiation and progression of non-small cell lung cancer (NSCLC). Although circRNA circCCDC66 has been revealed to elicit facilitating impact on cell growth and metastasis in colon cancer, the potential biological function and regulatory mechanism of it in NSCLC still require to be explored. In this study, circCCDC66 in NSCLC cells was highly expressed. Downregulation of circCCDC66 impaired cell proliferation, migration and invasion whereas boosted cell apoptosis in NSCLC. Data from molecular mechanism assays testified that circCCDC66 bound with miR-33a-5p in NSCLC cells. And miR-33a-5p inhibition could rescue the suppressive effect of circCCDC66 knockdown on NSCLC progression. In addition, karyopherin subunit alpha 4 (KPNA4) in NSCLC cells was proofed to be directly targeted by miR-33a-5p. Moreover, through rescued-function assays, we observed that upregulating KPNA4 expression could countervail the restraining function of silenced circCCDC66 on NSCLC progression. Furthermore, signal transducer and activator of transcription 3 (STAT3) was validated to activate CCDC66 transcription and thereby promote circCCDC66 expression in NSCLC cells. Briefly, STAT3-induced circCCDC66 upregulation accelerates NSCLC progression via miR-33a-5p/KPNA4 axis, suggesting circCCDC66 as a promising biomarker in NSCLC treatment.

Circular RNA CCDC66 promotes gastric cancer progression by regulating c-Myc and TGF-β signaling pathways

Background: CircRNAs play important roles in cancer development and progression and have the potential to serve as cancer biomarkers. The aim of this study was to investigate the role of circular RNA CCDC66 (circCCDC66) in gastric cancer and to reveal the underlying mechanisms.

Methods: The expression of circCCDC66 in GC tissues and cell lines was examined by qRT-PCR. The correlation between circCCDC66 expression level and clinicopathological characteristics was analyzed. The biological roles of circCCDC66 in GC cell apoptosis, proliferation, migration and invasion were determined by flow cytometry, cell counting, cell colony formation, wound healing, transwell migration and matrigel invasion assays. The role of circCCDC66 in GC growth was further confirmed by mouse xenograft tumor model. Western blot and qRT-PCR were used to explore the effects of circCCDC66 on epithelial-mesenchymal transition (EMT)-related gene and protein expression.

Results: CircCCDC66 expression was elevated in both GC tissues and cell lines compared to adjacent normal tissues and normal gastric epithelial cell line. The upregulation of circCCDC66 in GC tissues was related to tumor stage and lymphatic metastasis. CircCCDC66 knockdown significantly inhibited GC cell proliferation, migration and invasion and induced cell apoptosis in GC cells. On the contrary, circCCDC66 overexpression had the opposite effects. In addition, circCCDC66 knockdown suppressed the tumorigenesis of GC cells in nude mice. Furthermore, circCCDC66 knockdown inhibited the activation of c-Myc and TGF-β signaling pathways and reversed EMT in GC cells. c-Myc and TGF-β interference blocked circCCDC66-mediated promotion of gastric cancer cell proliferation, migration and invasion.

Conclusion: CircCCDC66 promotes GC growth and metastasis by activating c-Myc and TGF-β signaling pathways, suggesting that it may serve as a potential biomarker for GC.

Circular RNA hsa_circ_0061825 (circ-TFF1) contributes to breast cancer progression through targeting miR-326/TFF1 signalling

OBJECTIVES

Circular RNAs (circRNAs) are RNA transcripts that belong to non-coding RNAs (ncRNAs), whose implication in human cancers has been recently demonstrated. However, the specific role of multiple circRNAs in breast cancer remains unidentified.

MATERIALS AND METHODS

Microarray analysis and bioinformatics analysis were applied to select circRNA and miRNA, respectively. The loop structure of circ-TFF1 was confirmed using RNase R treatment, divergent primer PCR and Sanger sequencing. qRT-PCR and Western blot were employed for gene expressions. In vitro and in vivo experiments were conducted to assess the function of circ-TFF1 in biological processes in breast cancer cells. FISH and subcellular separation indicated circ-TFF1 cellular distribution. Luciferase reporter and RIP assays and Pearson's correlation analysis were performed to evaluate relationships between genes.

RESULTS

Circ-TFF1 and TFF1 were both upregulated and positively associated with each other in breast cancer. Knockdown of circ-TFF1 hindered breast cancer cell proliferation, migration, invasion and EMT in vitro and controlled tumour growth in vivo. Circ-TFF1 acted as a ceRNA of TFF1 by sponging miR-326, and its contribution to breast cancer progression was mediated by miR-326/TFF1 axis.

CONCLUSIONS

Circ-TFF1 is a facilitator in breast cancer relying on TFF1 by absorbing miR-326, providing a novel promising target for BC treatment.

CircTIMELESS regulates the proliferation and invasion of lung squamous cell carcinoma cells via the miR-136-5p/ROCK1 axis

Numerous studies demonstrate that circular RNAs (circRNAs) are critical regulators of the occurrence and progression of tumors. However, research on the involvement of circRNAs in lung squamous cell carcinoma (LUSC) is limited. In our study, circTIMELESS (also named hsa_circ_0000408 in the Human circRNA Database) was upregulated in both LUSC tissues and LUSC cells, and circTIMELESS expression was positively associated with the TNM stage. Moreover, circTIMELESS silencing markedly suppressed invasion in vitro and disrupted proliferation in vitro as well as in vivo. Additional investigations have shown that circTIMELESS functions as a miR-136-5p "sponge" and regulates miR-136-5p expression. Furthermore, the impact of miR-136-5p upregulation was consistent with the results of circTIMELESS silencing, both of which inhibited the proliferation and invasion of LUSC cells. Additional results showed that Rho-associated coiled-coil containing protein kinase 1 (ROCK1) is targeted by miR-136-5p. The results of recovery experiments showed that ROCK1 overexpression partly rescued the impact of circTIMELESS silencing and miR-136-5p upregulation on proliferation and invasion. Consequently, our findings confirmed that circTIMELESS exists in LUSC and acts as a tumor promoter through the miR-136-5p/ROCK1 axis. Based on these findings, circTIMELESS may be potentially utilized as a therapeutic target for LUSC.

Circular RNA hsa_circ_0000515 acts as a miR-326 sponge to promote cervical cancer progression through up-regulation of ELK1

This study investigates the role of circular RNA (circRNA) hsa_circ_0000515 in cervical cancer and the underlying mechanism associated with microRNA-326 (miR-326). hsa_circ_0000515 and ETS transcription factor ELK1 (ELK1) were initially over-expressed and miR-326 was down-regulated in cervical cancer tissues and cells. Low hsa_circ_0000515 expression was found to be associated with favorable prognosis of patients with cervical cancer. A series of mimics, inhibitors, over-expression plasmids or siRNAs were introduced into cervical cancer cells to alter the expression of hsa_circ_0000515, miR-326 and ELK1. In vitro experiments exhibited that silencing of hsa_circ_0000515 or upregulation of miR-326 resulted in suppressed proliferation and invasion, along with induced apoptosis and autophagy of cervical cancer cells. Dual-luciferase reporter assay, RNA pull-down and RIP assays highlighted that hsa_circ_0000515 was able to act as a ceRNA of miR-326 to increase ELK1. Furthermore, enhancement of ELK1 expression resulted in enhanced proliferation and invasion but repressed apoptosis and autophagy of cervical cancer cells. In vivo experiments further confirmed the suppressed tumor growth by hsa_circ_0000515 silencing. Our findings demonstrated that hsa_circ_0000515 acts as a tumor promoter in cervical cancer. The study provides evidence for targeting hsa_circ_0000515 for therapeutic purposes in treating cervical cancer.

Circular RNA circ-TSPAN4 promotes lung adenocarcinoma metastasis by upregulating ZEB1 via sponging miR-665

Background

Cancer metastasis is responsible for 90% of cancer‐related deaths. Recently, circular RNA (circRNA) is deemed to be an important regulator of cancer progression. However, little is known about the role of circRNA in the metastasis of lung adenocarcinoma (LUAD). Herein, we investigated the clinical implication and regulatory effect of circ‐TSPAN4 (hsa_circ_0020732) in LUAD.

Methods

Gene Expression Omnibus (GEO) database (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE104854) was used to identify the aberrantly expressed circRNAs in LUAD. The expression levels of circ‐TSPAN4, miR‐4731‐5p, miR‐665, and ZEB1 were determined by quantitative reverse transcription PCR (qRT‐PCR). The functional experiments were carried out with wound healing and transwell assays. And, the luciferase reporter and RNA pull‐down assays were employed to examine the crosstalk between circ‐TSPAN4, miR‐665, and ZEB1. In vivo metastasis experiment was tested by the lung metastasis model.

Results

Circ‐TSPAN4 was significantly upregulated in LUAD tissues and cell lines. The increased circ‐TSPAN4 was linked to advanced tumor‐node‐metastasis stage, lymph node and distant metastasis, and poor outcome. Lentivirus‐mediated stably circ‐TSPAN4 knockdown dramatically attenuated the metastatic ability of LUAD cells both in vitro and in vivo. Mechanistically, circ‐TSPAN4 directly interacted with miR‐665, but not miR‐4731‐5p, to increase the expression of ZEB1, which is a well‐known metastasis trigger. Importantly, the reduced metastatic capacity caused by circ‐TSPAN4 depletion was partially rescued by miR‐665 silencing or ZEB1 overexpression.

Conclusions

Circ‐TSPAN4 plays a pivotal metastasis‐promoting role in LUAD through acting as a sponge for miR‐665 and upregulating ZEB1.

Potential Diagnostic and Prognostic Biomarkers of Circular RNAs for Lung Cancer in China

Emerging evidence demonstrated that circular RNAs (circRNAs) were dysregulated in lung cancer, indicating that circRNAs might serve as novel diagnostic and prognostic biomarkers for lung cancer. However, the clinical value of circRNAs on lung cancer remains unclear. This study aimed to evaluate the efficiency of circRNAs in the diagnosis and prognosis for lung cancer in China. 2122 Chinese individuals were enrolled in this investigation for assessment of diagnostic value and examination of prognostic analysis. In the diagnostic analysis, the pooled sensitivity, specificity, PLR, NLR, DOR, and AUC of the sROC curve with their 95% CIs were 0.80 (95%CI: 0.74-0.84), 0.80 (95%CI: 0.73-0.86), 3.97 (95%CI: 2.80-5.62) and 0.26 (95%CI: 0.19-0.34), 15.51 (95%CI: 8.76-24.47), and 0.85 (95%CI: 0.82-0.88), respectively. As for the prognostic power of circRNAs, lung cancer patients with higher expression levels of circRNAs tend to possess lower overall survival with the overall pooled HR (1.70, 95%CI: 1.26-2.29). Furthermore, in stratified analysis, upregulated and downregulated circRNAs were manifested to exert significant effects on prognosis with HR values of 2.17 (95%CI: 1.74-2.72) and 0.52 (95%CI: 0.34-0.80). This study validates that circRNAs are promising diagnostic and predictive biomarkers for lung cancer patients in China.

Hsa_circ_0003998 may be used as a new biomarker for the diagnosis and prognosis of hepatocellular carcinoma

Background

Circular RNAs (circRNAs) play important roles in the progression of cancers, but the precise role of circRNAs in the diagnosis and prognosis of hepatocellular carcinoma (HCC) remains to be clarified. The aim of the current study was to explore the diagnostic and prognostic values of hsa_circ_0003998 in HCC.

Methods

CircRNAs expression was measured using RNA-seq analysis from HCC tissues (n=6) (three cases with or without portal vein invasion). Hsa_circ_0003998 in 200 pairs of HCC and adjacent noncancerous tissues and HCC cell lines was examined using qRT-PCR and the clinicopathologic significance was determined. We also detected the plasma levels of hsa_circ_0003998 in HCC, hepatitis B patients and healthy controls. The clinical diagnosis and prognostic values were further determined using receiver operating characteristic (ROC) curve, Kaplan–Meier curve and Cox regression.

Results

Hsa_circ_0003998 was upregulated in HCC tissues (P<0.001) and HCC cell lines (HepG2, HuH7, MHCC97H) (P<0.001). In addition, upregulation of hsa_circ_0003998 level was associated with higher serum alpha-fetoprotien (AFP) level (P=0.003), larger tumor diameter (P=0.009), lower differentiation level (P=0.023) and microvascular invasion (P=0.028). The plasma level of hsa_circ_0003998 in HCC patients was significantly higher than those in hepatitis B patients (P<0.001) and healthy controls (P<0.001). Its level was significantly reduced after the operation (P<0.001). The area under the ROC curve (AUC) for distinguishing HCC from adjacent noncancerous tissues was 0.894 (95% CI=0.86–0.922, P<0.001), the sensitivity and specificity were 0.84 and 0.8, respectively. Comparing with hepatitis B patients and healthy controls, hsa_circ_0003998, respectively, had an AUC value of 0.833 (95% CI=0.763–0.889, P<0.001) and 0.892 (95% CI=0.831–0.937, P<0.001). Their sensitivity and specificity were 0.83, 0.7 and 0.8, 0.84, respectively. Moreover, the combination of hsa_circ_0003998 and AFP showed the highest AUC value of 0.947, the sensitivity and specificity were 0.88 and 0.92, respectively. The hsa_circ_0003998 (P=0.003) and AFP (P=0.008) levels were independent prognostic factors for HCC. The overall survival of HCC patients with high level of hsa_circ_0003998 was significantly poorer than those with low level (P=0.005).

Conclusion

Our findings suggest that hsa_circ_0003998 may be used as a novel potential biomarker for the diagnosis and prognosis of HCC patients.