The Expression Of PREX2a In Human Gliomas And The Effect On Its Biological Behavior

Objective:Glioma is the most common malignant tumor in human brain. PREX2a is a guanosine exchange factor (GEF), participating in the Rac guanosine triphosphatase (GTPase) catalytic process. The expression of PREX2a has been reported to be significantly higher in a variety of tumors when compared with normal tissues, suggesting that it might be involved in the occurrence and development of cancer. However, either the role of PREX2a in the development of glioma or the involved molecular mechanism has not been fully uncovered. The present study determined the expression of PREX2a in normal brain tissue and WHO I-IV grade glioma tissues, to initially explore the relationship between PREX2a and glioma. We then applied RNA interference technology to decrease the expression of PREX2a in glioma cell line SWO-38, to further investigated the biological characteristics (proliferation, apoptosis, cell cycle and invasion capacity) of glioma cells after PREX2a was deregulated, as well as the involved molecular mechanisms. Method1.Fluorescence RT-PCR and Western Blot were used to determine the mRNA and protein expression levels of PREX2a in normal brain tissue and WHO Ⅰ-Ⅳ grade glioma tissues.2.PREX2a specificied siRNA was used to decrease the PREX2a expression in glioma cell line SWO-38, and fluorescent RT-PCR and Western Blot were performed to determine the interference effect.3.MTT assay was performed to examine the proliferation ability of glioma cell line SWO-38after PREX2a was deregulated.4.Flow cytometry assay was performed to examine the apoptosis level in glioma cell line SWO-38after PREX2a was deregulated.5.Flow cytometry assay was performed to determine the cell cycle in glioma cell line SWO-38after PREX2a was deregulated.6.TRANS WELL was performed to determine the invasion ability of glioma cell line SWO-38after PREX2a was deregulated.7.Western Blot was applied to determine phosphorylation levels of PTEN、Akt、mTOR in glioma cell line SWO-38after PREX2a was deregulated.Result1.The mRNA and protein expression levels of PREX2a in glioma tissues were significantly increased when compared with those in normal brain tissues, which were positively correlated with gliomas WHO grade. No significant difference of PREX2a mRNA was found between normal brain tissue and WHO I glioma, and between WHO III glioma and WHO IV glioma (P>0.05). Difference between the rest of any two groups was statistically significant (P<0.05). PREX2a mRNA and protein levels had no correlation with age and gender (P>0.05).2.After PREX2a specified siRNA transfection, the mRNA expression levels of PREX2a in glioma cell line SWO-38was decreased by78%, and the protein expression levels of PREX2a in glioma cell line SWO-38were decreased by72%, suggesting that the RNA interference was successful.3.After PREX2a specified siRNA transfection, the cell proliferation of glioma cell line SWO-38was significantly decreased by32%. The difference was statistically significant when compared with other groups (P<0.01).4.The cell apoptosis level of glioma cell line SWO-38was remarbably increased after the expression of PREX2a was suppressed. The percentage of apoptotic cells in Control, NC, and PREX2a RNAi group was2.91%±0.12%,3.04%±0.14%,11.87%±0.46%, respectively (P<0.01).5.The cell cycle of glioma cell line SWO-38was arrested after the expression of PREX2a was deregulated. After transfection, SWO-38cells in PREX2a RNAi group exhibited a significant increase in the cell fraction of G1phase (Control:36.87%±2.31%, NC:37.65%±2.57%, PREX2a RNAi:67.03%±2.92%, P<0.01) and a corresponding reduction in the fraction of cells in S phase (Control:39.36%±2.54%, NC:38.71%±2.36%, PREX2a RNAi:24.63%±2.17%, P<0.01), and G2-M phase (Control:23.77%±3.86%, NC:23.64%±3.14%, PREX2a RNAi:8.34%±3.83%,P<0.01).6.The invasion ablity of glioma cell line SWO-38was deregulated after the expression of PREX2a was decreased. The percentage of invasiveness cells in Control, NC, and PREX2a RNAi group was100%±5.27%,99.9%±1.83%,58.9%±5.29%respectively (P<0.01).7.After the expression of PREX2a was reduced, the phosphorylation level of PTEN in glioma cell line SWO-38was decreased, suggesting that the activity of PTEN was upregulated, and the phosphorylation levels of Akt and mTOR were also decreased, indicating that their activtity was inhibited.ConclusionThis study showed that PREX2a played a positive regulatory role in the occurrence and development of glioma, participating in the promotion of survival, proliferation, and invasion of glioma. The present study furter indicated that the regulatory molecular mechanism of PREX2a in glioma cells involved the inhibition of PTEN activity, as well as the enhancement of the activity of the PI3K/Akt/mTOR signaling pathway, which can promote cell survival, proliferation and migration, and plays a key role in the pathological process of malignant tumors.In summary, the present study reveals a crucial role of PREX2a in the regulation of the development of glioma as well as the related molecular mechanism. As a result, PREX2a may become a promising molecular target for the treatment of glioma.