MicroRNA-155Regulates Cell Proliferation And Invasion By Target FOXO3a In Glioma

Objective: To investigate the expression of microRNA-155in human glioma cellsand tissue samples. Then further explore the physiological functions of miR-155in cellgrowth and whether miR-155had a direct functional role in facilitating glioma cellsmigration and invasion, In particular, we aim to elucidate the underline mechanism ofmiR-155. The ultimate goal is to provide an exciting new theoretical basis for treatment ofhuman glioma.Methods: PartⅠ:1. Human glioma cell lines U87, U373, U251, SHG44and T98werechosen, the normal human brain astrocytes1800was taken as control. In addition, wecollected seven cases of human glioma specimens and two normal brain tissue. UsingqRT-PCR to detect the expression of miR-155in glioma cells and tissue specimens.2.miR-155mimics, miR-N.C. were transfected to some cells which expressed lower levels ofmiR-155; miR-155inhibitor (anti-miR-155), anti-N.C. were transfected to another cellswhich expressed higher levels of miR-155. Then, we evaluated the cell proliferation, cycle,apoptosis, migration, and invasion using Cell Counting Kit-8assay, Annexin-V/FITC assay,cell cycle assay, wound healing, and transwell assay in glioma cells. PartⅡ:1. Predictedthe potential gene targets of miRNA-155by Targetscan and miRbase bioinformaticssoftware. Western blot and qRT-PCR technology were used to examine the expression ofthe target gene FOXO3a in glioma and control group.2. Constructed a psiCHECK2plasmids for the FOXO33’UTR, the effect of miR-155on FOXO3a was evaluated byluciferase reporter gene assay and western blot.Results: PartⅠ:1. MiR-155expression in glioma group was significantly higher thanthe normal control group (P <0.05), it was the highest and lowest in the U87cell line andU251cell lines, respectively.2. miR-155gain of function promotes whereas knockdown ofmiR-155reduces cell proliferation, migration and invasion. But it had no influence on cell cycle. PartⅡ:1. By analysising bioinformatics software we found that FOXO3a is targetgenes of miR-155; Western blot show that FOXO3a protein expression in glioma groupwas lower than that in normal control group.2. The luciferase activity of vector wasdramatically decreased when the psi-FOXO3a vector was co-transfected with miR-155mimics. As expected, the luciferase levels of psi-FOXO3a-3’UTR were restored aftertransfection with the anti-miR-155. Furthermore, Western blot raised the possibility thatmiR-155suppresses FOXO3a protein synthesis by a post-transcriptional repressionmechanism.Conclusion: In summary, we have characterized that miR-155is commonly andmarkedly up-regulated in human glioma, and is able to promote the proliferation andinvasion ability of glioma cells in vitro. By bioinformatics and biological function test weverified that FOXO3a is the direct target genes of miR-155. This provides a theoreticalbasis for further in-depth study of glioma pathogenesis and treatment.