Circular RNA hsa_circ_0006168 contributes to cell proliferation, migration and invasion in esophageal cancer by regulating miR-384/RBBP7 axis via activation of S6K/S6 pathway

Z.-F. Xie, H.-T. Li, S.-H. Xie, M. Ma

Department of Thoracic Surgery, the First Affiliated Hospital of Medical College of Shantou University, Shantou, Guangdong, China. ianyuzhilipsvxb@163.com

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• Oncology

OBJECTIVE: Esophageal cancer (EC) ranks as the sixth leading cause of cancer-related mortality worldwide. Circular RNAs (circRNAs) are involved in the pathogenesis of different cancers. However, the regulatory mechanism of circ_0006168 in EC progression is still unclear.

MATERIALS AND METHODS: The expression of circ_0006168, microRNA (miR)-384, and retinoblastoma binding protein 7 (RBBP7) in tumors and cells was measured by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The stability of circ_0006168 was analyzed after RNase R treatment. 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay was conducted to evaluate cell viability. Transwell assay was applied to determine cell migration and invasion. Glucose consumption and lactate production were detected using glucose detection and lactic acid detection kits. The interaction between miR-384 and circ_0006168 or RBBP7 was certified by Dual-Luciferase reporter system. Protein expression of pyruvate kinase (PK), RBBP7, S6 ribosomal protein kinase (S6K), phosphorylated S6K (p-S6K), S6, phosphorylated S6 (p-S6) was analyzed by Western blot.

RESULTS: Circ_0006168 and RBBP7 were over-expressed while miR-384 was low-expressed in EC tumors and cells. The repression of circ_0006168 attenuated cell proliferation, migration, invasion, and glycolysis in EC. Of note, circ_0006168 functioned as a sponge while RBBP7 acted as a target of miR-384 in EC. Rescue experiment revealed that miR-384 inhibitor abrogated circ_0006168 silencing-induced repression on cell proliferation, migration, and invasion in EC. Meanwhile, upregulation of RBBP7 restored the inhibition of miR-384 on EC cell progression. Moreover, circ_0006168 was able to improve RBBP7 level by interacting with miR-384. Also, circ_0006168 could activate S6K/S6 pathway by regulating RBBP7 expression.

CONCLUSIONS: Abundance of circ_0006168 contributes to cell proliferation, migration, invasion, and glycolysis in EC by competitively sponging miR-384 to facilitate RBBP7 expression, representing prospective targets for EC therapy.

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