RabGEF1 Functions As An Oncogene In Glioma Through AKT And Erk Signaling Pathways

Background:RabGEF1,a guanine-nucleotide exchange factor(GEF)for Rab5,which belongs to the small G protein family.More and more studies have shown that RabGEF1 plays an oncogenic role in certain human cancers.However,there is no study for the function of RabGEF1 in glioma.Our previous study found that RabGEF1 was significantly up-regulated in human glioma tumor tissues.In addition,the knockdown of RabGEF1 was found to reduce cell viability of glioma cells,induce cell cycle arrest,apoptosis,inhibited cell migration and invasion.in U251 cells.By studying the cell AKT and Erk pathways s we found that p-AKT,p70S6K and p-Erk all decreased when RabGEF1 knockdown,indicating that RabGEF1 may act on the proliferation,invasion and apoptosis of glioma through AKT and Erk pathways.Here,we reported that the down-regulation of RabGEF1 inhibited proliferation,metastasis and induced autophagy in glioma in vitro,and functions as an oncogene in glioma through AKT and Erk signaling pathways.Methods:Pathological specimens of glioma were collected.RabGEF1 expression in glioma tissues and normal controls were measured by using Immunohistochemistry(IHC)analysis.siRNA1-4 that targeted sifferent sites of RabGEF1 gene were conducted and the inteference efficiencies were verified by qRT-PCR assay.Western blot was used to detect the expression of interest proteins.Cell proliferation was detected by using CCK-8 and clone formation assay.Cell migration and invasion were respectively analyzed by scratch assay and transwell assay.Flow cytometry was used to detect cell cycle distribution and apoptosis.Results:RabGEF1 was significantly up-regulated in human glioma tumor tissues compared with normal brain tissues.Western blot and qRT-PCR assays confirmed the effectiveness of RabGEF1 knockdown in mRNA and protein level.RabGEF1 knockdown was found to reduce cell viability,induce cell cycle arrest and apoptosis in U251 cells.Cell migration and invasion were also inhibited when RabGEF1 silencing.Mechanism studies showed that Cyclin D1 and CDK4/6 were significantly down-regulated by RabGEF1 knockdown.p-53 mediated apoptotic pathway was activated by down-regulation of RabGEF1.including increased p53,Bim.Bax,Active-caspase3 and decreased Bcl2.Moreover.RabGEF1 knockdown also induced autophagy in glioma cells,leading to up-regulation of Beclin-1 and LC3 and down-regulation of p62.The investigation of AKT and Erk pathways suggested that p-AKT.p70S6K and p-Erk were all decreased when RabGEF1 silencing.Conclusion:In conclusion,our data suggest that RabGEFl is up-regulated in human glioma and down-regulation of RabGEF1 inhibited cell proliferation,metastasis and induced autophagy in glioma through inactivation of AKT and Erk signaling pathways.