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

Open AccessPublished:December 18, 2019DOI:https://doi.org/10.1016/j.cancergen.2019.12.004

      Highlights

      • Hsa_circ_0062389 expression is significantly increased in NSCLC.
      • hsa_circ_0062389 might serve as a ceRNA to evaluate CCNE1 expression through sponging miR-103a-3p.

      Abstract

      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.

      Keywords

      Introduction

      Lung cancer is the most common type of malignancy and has high mortality worldwide [
      • Jemal A.
      • Bray F.
      • Center M M.
      • et al.
      Global cancer statistics[J].
      ]. Non-small cell lung cancer (NSCLC) is a subtype of lung cancer and occupies 85–90% of all lung cancer patients [
      • Molina J R.
      • Yang P.
      • Cassivi S D.
      • et al.
      Non-small cell lung cancer: epidemiology, risk factors, treatment, and survivorship.
      ,
      • Cruz C S D.
      • Tanoue L T.
      • Matthay R A
      Lung cancer: epidemiology, etiology, and prevention.
      ]. Although the development of novel therapeutic approaches during the past century, the recurrence rate is still disappointing and 5-year overall-survival remains unsatisfied (lower than 20%) [
      • de Groot P.
      • Munden R F
      Lung cancer epidemiology, risk factors, and prevention.
      ,
      • Didkowska J.
      • Wojciechowska U.
      • Mańczuk M.
      • et al.
      Lung cancer epidemiology: contemporary and future challenges worldwide.
      ]. Therefore, it is urgent to find effective treatment to overcome this malignancy.
      Circular RNA (circRNA) can form a circular structure in the way of being circularized by joining free 3′- to 5′-ends, which is a large group of non-coding RNA [
      • Qu S.
      • Yang X.
      • Li X.
      • et al.
      Circular RNA: a new star of noncoding RNAs.
      ,
      • Li Y.
      • Zheng Q.
      • Bao C.
      • et al.
      Circular RNA is enriched and stable in exosomes: a promising biomarker for cancer diagnosis.
      ]. Recently, emerging studies have shown that dysregulated circRNAs are implicated in pathological and physiological activities of various human cancers [
      • Kristensen L S.
      • Hansen T B.
      • Venø M T.
      • et al.
      Circular RNAs in cancer: opportunities and challenges in the field[J].
      ]. For example, Chen et al. found that hsa_circ_0000190 was downregulated in gastric cancer and associated with advanced clinical features and poor prognosis [
      • Chen S.
      • Li T.
      • Zhao Q.
      • et al.
      Using circular RNA hsa_circ_0000190 as a new biomarker in the diagnosis of gastric cancer.
      ]. Chen et al. showed that circRNA_100782 regulated cells proliferation via the IL6-STAT3 axis in pancreatic carcinoma [
      • Chen G.
      • Shi Y.
      • Zhang Y.
      • et al.
      CircRNA_100782 regulates pancreatic carcinoma proliferation through the IL6-STAT3 pathway.
      ]. Zhang et al. found that circRNA_069718 promoted triple-negative breast cancer cells proliferation and invasion through Wnt/β-catenin [
      • Zhang J.
      • Xu H D.
      • Xing X J.
      • et al.
      CircRNA_069718 promotes cell proliferation and invasion in triple-negative breast cancer by activating Wnt/β-catenin pathway.
      ]. Hsa_circ_0062389 is located in human chromosome 22q11.21. The biological functions of hsa_circ_0062389 in NSCLC have never been explored.
      In the present study, we found that hsa_circ_0062389 expression was upregulated in NSCLC tissues and cell lines. High hsa_circ_0062389 expression was correlated with advanced clinical features and poor prognosis. Subsequently, hsa_circ_0062389 knockdown reduced NSCLC cells proliferation and arrested cells in G0/G1 phase. Mechanistically, we showed that hsa_circ_0062389 sponged miR-103a-3p to promote CCNE1 expression in NSCLC. Conclusively, our study identified a novel hsa_circ_0062389/miR-103a-3p/CCNE1 axis in lung cancer progression.

      Materials and methods

      Tissue specimens

      A total of 33 paired of NSCLC tissues were collected from patients by surgical resection in the People's Hospital of Bozhou City between April 2014 and April 2017. None patients received any radiotherapy or chemotherapy before surgery. The fresh specimens were immediately frozen in liquid nitrogen and stored at −80 °C until use. This study was approved by the Ethics Committee of People's Hospital of Bozhou City. Informed consents were signed by all patients prior to participating in this study.

      Cell culture and transfection

      Human lung cancer cell lines (H1650, H23, H522, A549, H1703, H460) and human bronchiolar epithelial cell line (BEAS-2B) were obtained from ATCC (Manassas, VA, USA). Cells were cultured in DMEM medium (Gibco, Grand Island, NY, USA) contained with 10% fetal bovine serum (FBS, Gibco), 100 µg/ml streptomycin and 100 IU/ml penicillin followed by preservation in 5% CO2 at 37 °C.
      siRNAs targeting hsa_circ_0062389 (si-circ_0062389#1 5′- TGCAGACCTCCCGACCTCTTT-3′; si-circ_0062389#2 sequence is 5′- ATCTGCTGTCTGCAGACCTCC-3′), negative control siRNA (si-NC), miR-103a-3p mimics and inhibitors were designed and synthesized by GenePharma (Shanghai, China). Cell transfection was using Lipofectamine 2000 reagents (Invitrogen, Carlsbad, CA, USA).

      RNA extraction and qRT-PCR

      Total RNA was extracted using Trizol reagent (Invitrogen) as previously described [
      • Zhang H.
      • Yang F.
      • Chen S J.
      • et al.
      Upregulation of long non-coding RNA MALAT1 correlates with tumor progression and poor prognosis in clear cell renal cell carcinoma.
      ]. Samples were incubated with RNase R at 37 °C for 15 min to degrade linear RNA before reverse transcription. Reverse transcription and PCR of circRNAs and mRNAs were conducted using the Goscript™ Reverse Transcription System and GoTaq® qPCR Master Mix (Promega, Madison, WI, USA). MiRNA qRT-PCR Detection Kit (Genecopoeia, Rockville, MD, USA) was employed for miRNAs. U6 or GAPDH was the normalized control and relative expression was determined using the 2−ΔΔCT method.

      Cell proliferation assays

      Cell proliferation was determined by Cell Counting Kit-8 (CCK-8; Dojindo, Japan) and colony formation assays. CCK8 assay was performed as previously reported [
      • Li L.
      • Wang Q F.
      • Zou M L.
      • et al.
      Overexpressed lncRNA ZEB1-AS1 promotes cell invasion and angiogenesis through Wnt/β-catenin signaling in non-small cell lung cancer.
      ].
      As for colony formation assay, 500 cells were seeded into the 6-well plates and cultured for 14 days. Colonies were fixed by 4% paraformaldehyde and stained by 0.4% crystal violet solution. Then, clones were imaged under a microscope (Nikon, Japan).

      Dual-luciferase reporter assay

      The dual-luciferase reporter system (Promega, Madison, WI, USA) was employed for gene detection according to the manufacturer's instructions. Mutant-type plasmids of hsa_circ_0062389-MUT and CCNE1-MUT and wild-type plasmids of hsa_circ_0062389-WT and CCNE1-WT were constructed using pmirGLO. Lipofectamine 2000 was used for co-transfection with 50 nM miR-103a-3p mimics or negative control and mutant- or wild-type plasmid into HEK-293T cells. 48 h later, the relative luciferase activity was determined by the Dual Luciferase Reporter Assay System (Promega) according to the manufacturer's protocol. Renilla luciferase activity was normalized control.

      Statistical analysis

      All statistical analyses were performed with SPSS 19.0 (IBM, Armonk, NY, USA). Data were expressed as the mean ± SD. Differences were calculated using the student's t-test or one-way ANOVA. The expression correlation was determined by Spearman's correlation analysis. p values <0.05 were considered significant.

      Results

      Hsa_circ_0062389 was up-regulated in NSCLC

      The previous study showed that hsa_circ_0062389 was one of the most upregulated circRNAs in NSCLC tissues [
      • Chen L.
      • Nan A.
      • Zhang N.
      • et al.
      Circular RNA 100146 functions as an oncogene through direct binding to miR-361-3p and miR-615-5p in non-small cell lung cancer.
      ]. However, the roles of hsa_circ_0062389 were still unclear. In the present study, qRT-PCR showed that hsa_circ_0062389 expression was upregulated in NSCLC tissues and cell lines (Fig. 1A and B). High hsa_circ_0062389 expression was associated with advanced TNM stage, and lymph-node metastasis in NSCLC patients (Fig. 1C and D). These results suggested that hsa_circ_0062389 might play critical roles in NSCLC tumorigenesis.
      Fig. 1
      Fig. 1Hsa_circ_0062389 was upregulated in NSCLC. (A) Hsa_circ_0062389 expression in 33 paired NSCLC tissues. (B) Hsa_circ_0062389 expression in NSCLC cell lines. (C, D) High hsa_circ_0062389 expression was associated with advanced TNM stage, and lymph-node metastasis in NSCLC patients. *p < 0.05.

      Hsa_circ_0062389 promoted the proliferation and invasion in NSCLC cells

      Through inquiring from circBase, we showed that hsa_circ_0062389 is derived from the PI4KA locus, which is located on chromosome 22q11.21 (Fig. 2A). To investigate the roles of hsa_circ_0062389, we silenced hsa_circ_0062389 expression in A549 and H460 cells (Fig. 2B). CCK8 assay showed that hsa_circ_0062389 knockdown suppressed the proliferation of A549 and H460 cells (Fig. 2C and D). Colony formation assay further confirmed the effects of hsa_circ_0062389 knockdown on NSCLC cells proliferation (Fig. 2E and F). Additionally, flow cytometry analysis showed that hsa_circ_0062389 silencing arrested NSCLC cells cycle in G0/G1 phase (Fig. 2G and 2H). These results suggested that hsa_circ_0062389 might exert as an oncogenic circRNA in NSCLC progression.
      Fig. 2
      Fig. 2Hsa_circ_0062389 promoted the proliferation and invasion of lung cancer cells. (A) The information about hsa_circ_0062389. (B) Si-hsa_circ_0062389 decreased hsa_circ_0062389 expression in A549 and H460 cells. (C, D) Si-hsa_circ_0062389 decreased A549 and H460 cells proliferation abilities in vitro. (E, F) Si-hsa_circ_0062389 reduced A549 and H460 cells colony numbers. (G, H) Hsa_circ_0062389 silencing arrested A549 and H460 cells cycle in G0/G1 phase. *p < 0.05.

      Hsa_circ_0062389 is targeted by miR-103a-3p

      Previous studies indicated that circRNAs might function as a miRNA sponge to regulate gene expression by binding functional miRNAs [
      • Meng S.
      • Zhou H.
      • Feng Z.
      • et al.
      CircRNA: functions and properties of a novel potential biomarker for cancer.
      ,
      • Militello G.
      • Weirick T.
      • John D.
      • et al.
      Screening and validation of lncRNAs and circRNAs as miRNA sponges.
      ]. In the present study, we determined the main distribution of hsa_circ_0062389 in NSCLC cells (Fig. 3A). Subsequently, we analyzed the potential targets of hsa_circ_0062389 via bioinformatics method, and miR-103a-3p ranked top among all candidates (Fig. 3B–D). QRT-PCR showed that miR-103a-3p expression was significantly decreased in NSCLC tissues and cell lines (Fig. 3E and F). Kaplan–Meier analysis showed that low miR-103a-3p expression was correlated with poor overall survival of patients (Fig. 3G and H). In addition, Luciferase reporter assay indicated that miR-103a-3p mimics significantly reduced luciferase activities of hsa_circ_0062389-Mut group (Fig. 3I). Hsa_circ_0062389 knockdown promoted miR-103a-3p expression in A549 and H460 cells (Fig. 3J). These data suggested that miR-103a-3p could be bind to hsa_circ_0062389 in NSCLC.
      Fig. 3
      Fig. 3Direct interaction of hsa_circ_0062389 with miR-103a-3p. (A) Cytoplasmic and nuclear levels of hsa_circ_0062389 in A549 and H460 cells. (B–D) Bioinformatics evidence of miR-103a-3p binding onto hsa_circ_0062389. (E, F) MiR-103a-3p expression in NSCLC tissues and cell lines. (G, H) Low miR-103a-3p expression was correlated with poor prognosis of NSCLC patients. (I) MiR-103a-3p mimics reduced relative luciferase activities of hsa_circ_0062389-Mut group. (J) Hsa_circ_0062389 knockdown promoted miR-103a-3p expression in A549 and H460 cells. *p < 0.05.

      MiR-103a-3p directly targeted CCNE1

      Next, we explored the potential targets of miR-103a-3p by bioinformatics prediction. CCNE1 was selected for subsequent analyses (Fig. 4A and B). Luciferase reporter assay indicated that miR-103a-3p mimics significantly reduced luciferase activities of CCNE1-Mut group (Fig. 4C). Moreover, miR-103a-3p mimics suppressed the expression of CCNE1 in A549 and H460 cells (Fig. 4D). These data indicated that CCNE1 might act as a direct target of miR-103a-3p.
      Fig. 4
      Fig. 4MiR-103a-3p directly targeted CCNE1. (A) Potential binding genes of miR-103a-3p. (B) The predicted binding sites of miR-103a-3p with CCNE1. (C) MiR-103a-3p mimics reduced relative luciferase activities of CCNE1-Mut group. (D) MiR-103a-3p mimics suppressed CCNE1 mRNA expression in A549 and H460 cells. *p < 0.05.
      Then, we determined CCNE1 expression in NSCLC tissues, IHC showed that CCNE1 expression was significantly increased in NSCLC tissues (Fig. 5A). And the results were further confirmed by the TCGA database (Fig. 5B). In addition, we showed that CCNE1 expression was significantly reduced in lung tissues by NCBI and UCSC online database (Fig. 5C and D). Kaplan–Meier analysis showed that high CCNE1 expression was correlated with poor overall survival of patients (Fig. 5E and F).
      Fig. 5
      Fig. 5CCNE1 expression in NSCLC. (A) IHC showed that CCNE1 expression was significantly increased in NSCLC tissues. (B) TCGA database showed that CCNE1 expression was significantly increased in NSCLC tissues (LUAD and LUSC). (C, D) NCBI and UCSC online database showed that CCNE1 expression was significantly reduced in lung tissues. (E, F) High CCNE1 expression was correlated with poor overall survival of NSCLC patients. LUAD: Lung adenocarcinoma; LUSC: Lung squamous cell carcinoma; * p< 0.05.

      Hsa_circ_0062389 promoted NSCLC progression via miR-103a-3p/CCNE1 axis

      We further explored whether hsa_circ_0062389 regulated NSCLC progression via miR-103a-3p/CCNE1 axis. QRT-PCR showed that hsa_circ_0062389 knockdown reduced the expression of CCNE1, which was abrogated via miR-103a-3p inhibitors (Fig. 6A). In addition, we utilized miR-103a-3p inhibitors and CCNE1 overexpression vectors (pcDNA3-CCNE1) to perform rescue assays (Fig. 6B and C). Colony formation assay showed found that miR-103a-3p inhibitors reversed the effects of hsa_circ_0062389 knockdown on A549 cells proliferation (Fig. 6D). Cell cycle assay showed CCNE1 overexpression abolished the effects of hsa_circ_0062389 knockdown on H460 cells cycle (Fig. 6E). Therefore, these data indicated that hsa_circ_0062389 might promote lung cancer proliferation through regulating the miR-103a-3p/CCNE1 axis (Fig. 6F).
      Fig. 6
      Fig. 6Hsa_circ_0062389 promoted NSCLC progression via miR-103a-3p/CCNE1 axis. (A) MiR-103a-3p inhibitors reversed the effects of hsa_circ_0062389 knockdown on CCNE1 expression. (B, C) The transfected efficiency of miR-103a-3p inhibitors or CCNE1 overexpression vectors in lung cancer cells. (D) MiR-103a-3p inhibitors reversed the effects of hsa_circ_0062389 knockdown on A549 cells colony numbers. (E) CCNE1 overexpression abolished the effects of hsa_circ_0062389 knockdown on H460 cells cycle distribution. (F) Hsa_circ_0062389/miR-103a-3p/CCNE1 axis in NSCLC. *p < 0.05.

      Discussion

      Recent studies indicated that circRNAs play key roles in lung cancer progression. For example, Luo et al. showed that hsa_circ_0000064 was upregulated in lung cancer and promoted tumor proliferation and invasion ability [
      • Luo Y H.
      • Zhu X Z.
      • Huang K W.
      • et al.
      Emerging roles of circular RNA hsa_circ_0000064 in the proliferation and metastasis of lung cancer.
      ]. Qiu et al. suggested that circRNA FGFR3 promoted NSCLC progression through the Galectin‐1‐AKT/ERK1/2 axis [
      • Qiu B Q.
      • Zhang P F.
      • Xiong D.
      • et al.
      CircRNA fibroblast growth factor receptor 3 promotes tumor progression in non‐small cell lung cancer by regulating Galectin‐1‐AKT/ERK1/2 signaling.
      ]. Wang et al. found that hsa_circ_0012673 served as a sponge of miR-22 to promote lung adenocarcinoma cells proliferation [
      • Wang X.
      • Zhu X.
      • Zhang H.
      • et al.
      Increased circular RNA hsa_circ_0012673 acts as a sponge of miR-22 to promote lung adenocarcinoma proliferation.
      ]. In this study, we identified a circRNA hsa_circ_0062389 which is derived from the PI4KA locus (located on chromosome 22q11.21). We showed that hsa_circ_0062389 is highly expressed in NSCLC tissues and cell lines. High hsa_circ_0062389 expression was associated with advanced TNM stage and lymph-node metastasis. In function assays, we showed that hsa_circ_0062389 inhibition reduced NSCLC cells proliferation in vitro. These data suggested that hsa_circ_0062389 might act as a novel oncogene in NSCLC progression.
      Increasing studies showed that circRNAs could serve as ceRNAs to sequester away the miRNA from its target genes [
      • Meng S.
      • Zhou H.
      • Feng Z.
      • et al.
      CircRNA: functions and properties of a novel potential biomarker for cancer.
      ]. For example, Zhao et al. found that circFADS2 regulated the proliferation and invasion through serving as a sponge of miR-498 in lung cancer [
      • Zhao F.
      • Han Y.
      • Liu Z.
      • et al.
      circFADS2 regulates lung cancer cells proliferation and invasion via acting as a sponge of miR-498.
      ]. Xue et al. showed that hsa_circ_0081143 promoted cisplatin resistance in gastric cancer by targeting miR-646-CDK6 axis [
      • Xue M.
      • Li G.
      • Fang X.
      • et al.
      hsa_circ_0081143 promotes cisplatin resistance in gastric cancer by targeting miR-646/CDK6 pathway.
      ]. In the present study, we determined the potential miRNA targets via bioinformatics method. Results showed that miR-103a-3p might be targeted by hsa_circ_0062389. Subsequently, qRT-PCR showed that miR-103a-3p expression was significantly decreased and correlated with poor overall survival in NSCLC patients. Moreover, luciferase reporter assay and qRT-PCR suggested that hsa_circ_0062389 directly interacted with miR-103a-3p in NSCLC. Therefore, we suggested that hsa_circ_0062389 might function as a miR-103a-3p sponge in lung cancer progression.
      Cyclin E1 (CCNE1) a vital cell cycle regulator, plays an important role in human malignancies [
      • Honda R.
      • Lowe E D.
      • Dubinina E.
      • et al.
      The structure of cyclin E1/CDK2: implications for CDK2 activation and CDK2‐independent roles.
      ]. For example, Gurzov et al. showed that CCNE1 knockdown induced apoptosis in cancer cells [
      • Gurzov E N.
      • Izquierdo M
      Cyclin E1 knockdown induces apoptosis in cancer cells.
      ]. Hui et al. showed that miR-195 suppressed the glioma cells proliferation via targeting CCND1 and CCNE1 [
      • Hui W.
      • Yuntao L.
      • Lun L.
      • et al.
      MicroRNA-195 inhibits the proliferation of human glioma cells by directly targeting cyclin D1 and cyclin E1.
      ]. Yang et al. found that circRNA circAGFG1 served as a sponge of miR-195-5p to promote breast cancer progression by regulating CCNE1 expression [
      • Yang R.
      • Xing L.
      • Zheng X.
      • et al.
      The circRNA circAGFG1 acts as a sponge of miR-195-5p to promote triple-negative breast cancer progression through regulating CCNE1 expression.
      ]. In the present study, we found that CCNE1 expression was significantly increased in NSCLC patients and correlated with poor prognosis. Subsequently, bioinformatics analysis showed that CCNE1 was the most potential target of miR-103a-3p. Luciferase reporter and qRT-PCR assays further confirmed the interaction between miR-103a-3p and CCNE1. Moreover, rescue assays showed that miR-103a-3p inhibition or CCNE1 overexpression reversed the effects of hsa_circ_0062389 knockdown on lung cancer progression. Thus, we indicated that hsa_circ_0062389 might serve as a ceRNA for miR-103a-3p to promote CCNE1 expression in lung cancer.
      In conclusion, our present study identified a novel circRNA hsa_circ_0062389 in NSCLC progression. In mechanism, we showed that hsa_circ_0062389 could sponge miR-103a-3p to modulate the expression of CCNE1 in lung cancer, which might provide a potential therapeutic target lung cancer management.

      Declarations

      Ethics approval and consent to participate

      Ethical approval was given by the Ethics Committee of People's Hospital of Bozhou City.

      Availability of data and materials

      The dataset supporting the conclusions of this article is included within the article.

      Funding

      None.

      CRediT authorship contribution statement

      Yahui She: Project administration, Investigation, Methodology, Writing - original draft. Yuanyuan Han: Project administration. Guangting Zhou: Software. Fangyan Jia: Investigation. Tan Yang: Investigation. Zuojun Shen: Project administration, Writing - review & editing.

      Declaration of Competing Interest

      All the authors declare that they have no conflict of interest.

      Appendix. Supplementary materials

      References

        • Jemal A.
        • Bray F.
        • Center M M.
        • et al.
        Global cancer statistics[J].
        CA Cancer J Clin. 2011; 61: 69-90
        • Molina J R.
        • Yang P.
        • Cassivi S D.
        • et al.
        Non-small cell lung cancer: epidemiology, risk factors, treatment, and survivorship.
        Mayo Clinic Proc. 2008; 83: 584-594
        • Cruz C S D.
        • Tanoue L T.
        • Matthay R A
        Lung cancer: epidemiology, etiology, and prevention.
        Clin Chest Med. 2011; 32: 605-644
        • de Groot P.
        • Munden R F
        Lung cancer epidemiology, risk factors, and prevention.
        Radiologic Clin. 2012; 50: 863-876
        • Didkowska J.
        • Wojciechowska U.
        • Mańczuk M.
        • et al.
        Lung cancer epidemiology: contemporary and future challenges worldwide.
        Ann Transl Med. 2016; 4
        • Qu S.
        • Yang X.
        • Li X.
        • et al.
        Circular RNA: a new star of noncoding RNAs.
        Cancer Lett. 2015; 365: 141-148
        • Li Y.
        • Zheng Q.
        • Bao C.
        • et al.
        Circular RNA is enriched and stable in exosomes: a promising biomarker for cancer diagnosis.
        Cell Res. 2015; 25: 981
        • Kristensen L S.
        • Hansen T B.
        • Venø M T.
        • et al.
        Circular RNAs in cancer: opportunities and challenges in the field[J].
        Oncogene. 2018; 37: 555
        • Chen S.
        • Li T.
        • Zhao Q.
        • et al.
        Using circular RNA hsa_circ_0000190 as a new biomarker in the diagnosis of gastric cancer.
        Clin Chim Acta. 2017; 466: 167-171
        • Chen G.
        • Shi Y.
        • Zhang Y.
        • et al.
        CircRNA_100782 regulates pancreatic carcinoma proliferation through the IL6-STAT3 pathway.
        Onco Targets Ther. 2017; 10: 5783
        • Zhang J.
        • Xu H D.
        • Xing X J.
        • et al.
        CircRNA_069718 promotes cell proliferation and invasion in triple-negative breast cancer by activating Wnt/β-catenin pathway.
        Eur Rev Med Pharmacol Sci. 2019; 23: 5315-5322
        • Zhang H.
        • Yang F.
        • Chen S J.
        • et al.
        Upregulation of long non-coding RNA MALAT1 correlates with tumor progression and poor prognosis in clear cell renal cell carcinoma.
        Tumor Biol. 2015; 36: 2947-2955
        • Li L.
        • Wang Q F.
        • Zou M L.
        • et al.
        Overexpressed lncRNA ZEB1-AS1 promotes cell invasion and angiogenesis through Wnt/β-catenin signaling in non-small cell lung cancer.
        Int J Clin Exp Patho. 2017; 10: 3990-3997
        • Chen L.
        • Nan A.
        • Zhang N.
        • et al.
        Circular RNA 100146 functions as an oncogene through direct binding to miR-361-3p and miR-615-5p in non-small cell lung cancer.
        Mol. Cancer. 2019; 18: 13
        • Meng S.
        • Zhou H.
        • Feng Z.
        • et al.
        CircRNA: functions and properties of a novel potential biomarker for cancer.
        Mol Cancer. 2017; 16: 94
        • Militello G.
        • Weirick T.
        • John D.
        • et al.
        Screening and validation of lncRNAs and circRNAs as miRNA sponges.
        Brief Bioinformatics. 2016; 18: 780-788
        • Luo Y H.
        • Zhu X Z.
        • Huang K W.
        • et al.
        Emerging roles of circular RNA hsa_circ_0000064 in the proliferation and metastasis of lung cancer.
        Biomed Pharmacother. 2017; 96: 892-898
        • Qiu B Q.
        • Zhang P F.
        • Xiong D.
        • et al.
        CircRNA fibroblast growth factor receptor 3 promotes tumor progression in non‐small cell lung cancer by regulating Galectin‐1‐AKT/ERK1/2 signaling.
        J Cell Physiol. 2019; 234: 11256-11264
        • Wang X.
        • Zhu X.
        • Zhang H.
        • et al.
        Increased circular RNA hsa_circ_0012673 acts as a sponge of miR-22 to promote lung adenocarcinoma proliferation.
        Biochem Biophys Res Commun. 2018; 496: 1069-1075
        • Zhao F.
        • Han Y.
        • Liu Z.
        • et al.
        circFADS2 regulates lung cancer cells proliferation and invasion via acting as a sponge of miR-498.
        Biosci Rep. 2018; 38 (BSR20180570)
        • Xue M.
        • Li G.
        • Fang X.
        • et al.
        hsa_circ_0081143 promotes cisplatin resistance in gastric cancer by targeting miR-646/CDK6 pathway.
        Cancer Cell Int. 2019; 19: 25
        • Honda R.
        • Lowe E D.
        • Dubinina E.
        • et al.
        The structure of cyclin E1/CDK2: implications for CDK2 activation and CDK2‐independent roles.
        EMBO J. 2005; 24: 452-463
        • Gurzov E N.
        • Izquierdo M
        Cyclin E1 knockdown induces apoptosis in cancer cells.
        Neurol Res. 2006; 28: 493-499
        • Hui W.
        • Yuntao L.
        • Lun L.
        • et al.
        MicroRNA-195 inhibits the proliferation of human glioma cells by directly targeting cyclin D1 and cyclin E1.
        PLoS One. 2013; 8: e54932
        • Yang R.
        • Xing L.
        • Zheng X.
        • et al.
        The circRNA circAGFG1 acts as a sponge of miR-195-5p to promote triple-negative breast cancer progression through regulating CCNE1 expression.
        Mol Cancer. 2019; 18: 4