The Functions And Mechanisms Of Rab18 In Human Glioma

BackgroundGliomas are the most common primary tumors of the central nervous system and account for 40%-50%of brain tumors,which are of high malignancy,poor prognosis and high mortality.In recent years,the epidemiological investigation found that the incidence of gliomas increased significantly and showed a trend of youth,which has increasingly become one of the major challenges in the field of neurosurgery and oncology.It is an important task to explore more biomarkers for the diagnosis and treatment of gliomas.Rab protein family is the largest subfamily of Ras superfamily,which contains more than 60 members.Several Rab proteins have been reported to be related to the occurrence and development of human gliomas,such as Rab 13,which affect the proliferation,differentiation,apoptosis,invasion and metastasis in gliomas.These findings are of great significance to the clinical diagnosis,treatment and prognosis of gliomas in the future.However,there are no reports about the functions and mechanisms of Rab 18 in human gliomaAimsThe purpose of this study is to preliminarily verify the value of Rab 18 expression level in the diagnosis and progression of human glioma.In order to provide an ideal candidate target for clinical treatment of human glioma,we explored the mechanisms of Rabl8 on the proliferation and apoptosis of human glioma cells by silencing Rab18.MethodsHuman glioma tissue samples(n=33)and normal brain tissue samples(n=15)were obtained by surgery.According to WHO classification,glioma tissue samples were divided into low-grade group(WHO Ⅰ-Ⅱ,n=14)and high-grade group(WHOⅢ-Ⅳ,n=19).None of the patients had received chemotherapy or radiation therapy before surgery.In addition,human glioma cell lines were transfected by siRNA technology.The cell lines were divided into siRab18 group(transfected with Rab18 siRNA,experimental group),siNC group(transfected with NC siRNA,negative control group)and WT group(not transfected,blank control group).HE staining was used to observe the histological morphology of different grades glioma.qRT-PCR and Western-blot assay were used to detect the mRNA and protein expression levels of Rab18 in human glioma tissues and cells.CCK-8 assay was used to detect cell proliferation,and flow cytometry was used to detect cell cycle distribution and apoptosis.ResultsThe mRNA and protein expression levels of Rab18 in human gliomas(n=33)were significantly higher than that in normal brain tissues(n=15),in which the expression of Rab18 in high-grade gliomas(WHO Ⅲ-Ⅳ,n=19)was significantly higher than that in low-grade gliomas(WHO Ⅰ-Ⅱ,n=14)(P<0.01),indicating that the expression level of Rab18 was related to the malignant degree of gliomas.Among the three common human glioma cells,the expression level of Rab18 in U251 and U87 cells were significantly higher than that in T98G cells(P<0.01),indicating that the expression of Rab18 in different glioma cells were different.Not only the expression levels of Rab18 and cell proliferation downregulated significantly,but also induced human glioma cell cycle arrest in G0/G1 phase accompanied by a reduction in S-phase cell percentage after Rab18 silencing,which indicated that Rab18 silencing could significantly inhibit the expression of Rab18 and proliferation in glioma cells via cell cycle arrest(P<0.01).In addition,the early stage and late stage apoptotic population were higher in both glioma cell lines after Rab18 silencing(P<0.01).The results showed that the mRNA and protein expression levels of apoptosis related proteins P53,Caspase 7,Bax and Bim were significantly increased(P<0.01),which was an important mechanism of Rab18 silencing promoting apoptosis of human glioma cells.ConclusionsIn conclusion,the expression levels of Rab18 are related to the malignant degree of gliomas.The higher the malignant degree of glioma is,the higher the expression levels of Rab18 is,which preliminarily proves that the expression levels of Rab18 has an important value for the diagnosis and progress in human gliomas.Rab18 silencing can not only inhibit cell proliferation in gliomas via cell cycle arrest,but also promote cell apoptosis via upregulating the expression levels of apoptosis related proteins P53,Caspase 7,Bax and Bim,which indicates that Rab18 is an ideal target for clinical treatment of human glioma.