Circ_DLG1 facilitates esophageal squamous cell carcinoma progression by mediating miR-338-3p/MAP3K9 axis via activating MAPK/ERK pathway

Abstract

Background: Esophageal squamous cell carcinoma (ESCC) is an aggressive malignancy with a high incidence and poor prognosis. The document of circular RNAs (circRNAs) is frequently associated with cancer development. This study intended to explore the functional mechanism of circ_DLG1 in ESCC.Methods: The expression of circ_DLG1, miR-338-3p and Mitogen-Activated Protein Kinase Kinase Kinase 9 (MAP3K9) was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Cell cycle, proliferation, migration and invasion were performed for functional analysis using flow cytometry, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) and transwell assay, respectively. The protein levels of MAP3K9, p38, phosphor p38 (p-p38), ERK1/2, phosphor ERK1/2 (p-ERK1/2) were detected by western blot. Bioinformatics tool for target prediction used the online tool starBase. Dual-luciferase reporter assay was performed to verify the target relationship. The animal experiments were performed to ascertain the role of circ_DLG1 in vivo.Results: The expression of circ_DLG1 was elevated in ESCC tissues, plasma and cells. Circ_DLG1 knockdown inhibited cell cycle, proliferation, migration and invasion. MAP3K9 was highly expressed in ESCC tissues and cells, and its overexpression rescued the effects of circ_DLG1 knockdown. MiR-338-3p was a link between circ_DLG1 and MAP3K9, and circ_DLG1 regulated the expression of MAP3K9 by targeting miR-338-3p. The MAPK/ERK pathway was involved in the circ_DLG1/miR-338-3p/MAP3K9 regulatory axis. Circ_DLG1 knockdown blocked the tumor growth in vivo by regulating miR-338-3p and MAP3K9.Conclusion: Circ_DLG1 contributed to the malignant progression of ESCC by mediating the miR-338-3p/MAP3K9 axis via activating the MAPK/ERK signaling pathway. This paper provided a novel action mode of circ_DLG1 in ESCC.