Background
Circ_DLG1 is found to be aberrantly expressed in esophageal squamous cell carcinoma (ESCC) tissues, but its role in the progression of ESCC remains to be elucidated.
Methods
The expression of circ_DLG1, miR-338-3p and mitogen-activated protein kinase kinase kinase 9 (MAP3K9) was measured by qRT-PCR. Cell cycle, viability, migration and invasion were investigated using flow cytometry, MTT assay and transwell assay, respectively. The protein levels of MAP3K9, p38, phosphor p38 (p-p38), ERK1/2 (ERKs), phosphor ERKs (p-ERKs) were detected by western blot. Dual-luciferase reporter assay and RIP assay were performed to verify the putative relationship between miR-338-3p and circ_DLG1 or MAP3K9. Animal experiments were performed to ascertain the role of circ_DLG1 in vivo.
Results
Circ_DLG1 expression was elevated in ESCC tissues, plasma and cells. Circ_DLG1 knockdown inhibited cell proliferation, migration and invasion. MAP3K9 was highly expressed in ESCC, and its overexpression rescued the effects of circ_DLG1 knockdown on cell proliferation and metastasis. Besides, circ_DLG1 positively regulated MAP3K9 expression by competitively targeting miR-338-3p. Also, miR-338-3p inhibition or MAP3K9 overexpression recovered the inhibiting effect of circ_DLG1 knockdown on the phosphorylated levels of p38 and ERKs. In addition, circ_DLG1 knockdown blocked the tumor growth in vivo by regulating the miR-338-3p/MAP3K9 axis.
Conclusion
Circ_DLG1 promoted malignant progression of ESCC by mediating the miR-338-3p/MAP3K9/p38/ERK pathway, indicating that targeted inhibition of the circ_DLG1/miR-338-3p/MAP3K9/p38/ERK axis might be an effective strategy for the treatment of ESCC.
