Abstract
MicroRNAs (miRs) serve important roles in the development and progression of various human cancer types, including glioma. Recently, miR-219 has been suggested to function as a tumor suppressor in glioma; however, the underlying mechanism remains largely unknown. The aim of this study was to investigate the regulatory mechanism of miR-219 in the malignant phenotypes of glioma cells. Quantitative polymerase chain reaction (qPCR) and western blotting were conducted to examine the mRNA and protein expression. An MTT assay, wound healing assay and Transwell assay were used to study cell proliferation, migration and invasion. The qPCR data indicated that the expression of miR-219 was significantly decreased in glioma tissues compared with normal brain tissues. In addition, a low expression of miR-219 was identified to be associated with an advanced pathological grade. In vitro experiments demonstrated that miR-219 was also downregulated in several common glioma cell lines, including A172, U87, U251 and U373, when compared with that in normal astrocytes. Ectopic expression of miR-219 caused a significant decrease in U87 cell proliferation, migration and invasion. Luciferase reporter assay data indicated that Sal-like protein 4 (SALL4) was a direct target gene of miR-219, while the protein expression of SALL4 was negatively regulated by miR-219 in U87 cells. Furthermore, SALL4 was significantly upregulated in glioma tissues and cell lines, and upregulation of SALL4 was associated with a higher pathological grade. Furthermore, overexpression of SALL4 significantly attenuated the suppressive effects of miR-219 on U87 cell proliferation, migration and invasion, suggesting that miR-219 serves a suppressive role in glioma growth and metastasis via targeting SALL4. Therefore, the present study highlighted the clinical significance of the miR-219/SALL4 axis in glioma.