Abstract

Circular RNA mediator of cell motility 1 (circ-MEMO1) was identified as an oncogene in non-small cell lung cancer (NSCLC). Nevertheless, the working mechanism behind circ-MEMO1-mediated progression of NSCLC is barely known. Quantitative real-time polymerase chain reaction (qRT-PCR) was applied to detect the expression of circ-MEMO1, microRNA-101-3p (miR-101-3p), and KRAS proto-oncogene, GTPase (KRAS). Cell proliferation and aerobic glycolysis were detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and glycolysis detection kits. Flow cytometry was used to evaluate cell cycle progression and apoptosis of NSCLC cells. Western blot assay was used to measure the protein expression of hexokinase 2 (HK2), lactate dehydrogenase A (LDHA), KRAS, CD9, CD81, tumor susceptibility 101 (TSG101), and Golgi matrix protein 130 kDa (GM130). The target relationship between miR-101-3p and circ-MEMO1 or KRAS was predicted by StarBase software and confirmed by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and RNA-pull down assay. In vivo tumor growth assay was conducted to assess the effect of circ-MEMO1 in vivo. Exosomes were isolated using the ExoQuick precipitation kit. Circ-MEMO1 was up-regulated in NSCLC, and high expression of circ-MEMO1 predicted poor prognosis in NSCLC patients. Circ-MEMO1 accelerated the proliferation, cell cycle progression, and glycolytic metabolism and inhibited the apoptosis of NSCLC cells. Circ-MEMO1 negatively regulated the expression of miR-101-3p through direct interaction, and si-circ-MEMO1-induced biological effects were attenuated by the introduction of anti-miR-101-3p. MiR-101-3p directly interacted with the 3′ untranslated region (3′ UTR) of KRAS messenger RNA (mRNA), and KRAS level was regulated by circ-MEMO1/miR-101-3p axis. Circ-MEMO1 silencing suppressed the NSCLC tumor growth in vivo. ROC curve analysis revealed that high expression of serum exosomal circ-MEMO1 (exo-circ-MEMO1) might be a valuable diagnostic marker for NSCLC. Circ-MEMO1 facilitated the progression and glycolysis of NSCLC through regulating miR-101-3p/KRAS axis.

Highlights

  • The activation of pro-tumor genes and the inactivation of antitumor genes both contribute to the initiation and progression of cancers

  • We analyzed the expression of circ-MEMO1 in non-small cell lung cancer (NSCLC) tissues and adjacent normal tissues to explore if circ-MEMO1 was dysregulated in NSCLC

  • Circ-MEMO1 was down-regulated in tumor tissues in a total of seven NSCLC patients compared with adjacent normal tissues (Figure 1A)

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Summary

Introduction

The activation of pro-tumor genes and the inactivation of antitumor genes both contribute to the initiation and progression of cancers. KRAS proto-oncogene GTPase (KRAS) is a member of pro-tumor genes that always abnormally activated in diverse cancers (Chen et al, 2014). We provided a novel signal axis in which KRAS was activated by its upstream genes and participated in the progression of non-small cell lung cancer (NSCLC). Exosomes are small extracellular vesicles (30–150 nm) that are released by many types of cells. Exosomal circ_0044516 accelerated the progression of prostate cancer by targeting miR-29a-3p (Li et al, 2020). Liu et al (2020) revealed that circ-MMP2 could be transferred between different hepatocellular carcinoma (HCC) cell lines, and circMMP2 accelerated HCC cells motility via miR-136-5p/MMP2 axis. We investigated the role of circ-MEMO1 and assessed the clinical diagnostic significance of serum exosomal circMEMO1 in NSCLC

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