| Glioblastoma multiforme(GBM) is the most common malignant tumor of the central nervous system, accounting for 35.12% to 61.10% of intracranial tumors. GBM cells contains a mixture cell populations with high propensity to infiltrate throughout the brain, showing devastating malignant process. Although most of GBM cells are killed by therapeutic treatments, there always are a small number of radioresistant cells which induce recurrence. It has been demonstrated that these radioresistant cells possess the features of stem cells, showing stem cell surface markers, infinite proliferation, self-renewal ability and pluripotency. Recently, there are studies even indicate that the differentiation process of tumor cells is reversible. Differentiated tumor cells, after ionizing radiation, could be reprogrammed to regain the ability of stem cells.Translationally controlled tumor protein(TCTP), also named histamine releasing factor, is a widely expressed and highly conserved protein. In recent years, studies indicate that TCTP has several important biological functions, including regulation of the cell cycle, proliferation, malignant metastases, anti-apoptosis, tumor drug resistance, etc. Recently, the role of TCTP in cancer stem cells has been discussed deeply. Studies have shown that TCTP is involved in regulating of cancer stem cells, supported by suppression of the malignant phenotype and cellular reorganization under the decreased expression of TCTP. These phenomena hint not only a critical role of TCTP in maintenance of malignant phenotype, but also a promising target molecular in the development of the cancer treatment.Based on these important functions of TCTP, this study aims at the role of TCTP in maintaining stemness of glioma stem cells and in radioresistance of GBM cells. We used colony forming assay to detect the proliferation ability of cells. Wound healing assay and HoloMonitor image analysis were used to detect the migration ability of cells. The expression level of protein and mRNA were respectively measured by Western blot, immunohistochemistry and RT-RCR. Flow cytometry was used to detect the stem cell markers and cell sorting. The self-renewal ability was detected by spheroid formation assay. In vivo nude model was used to measure the tumorigenicity of cells.Western blot results showed that TCTP is more highly expressed in tumorspheres and stem-like cells. Reduction of TCTP expression induced the obviously lower proliferation and migration ability. TCTP is very important for the maintenance of stemness. The expression level of stem cell markers, percentage of stem cells and spheroid forming number were significantly reduced after reduction of TCTP expression. The tumorigenicity of GBM cells was inhibited by TCTP knockdown and expressions of stem cell markers in transplanted tumors were also reduced. After 3Gy X-ray radiation, the proportion of CD49f+ cells in the sorted non-CSCs increased significantly. At the same time, the expression of TCTP increased significantly, accompanied by increased expression of stem cell markers, self-renewal ability, percentage of stem-like cells and tumorigenicity. Reduction of TCTP expression enhanced the sensitivity of GBM cells to radiotherapy. After 3Gy or 6Gy X-ray radiation, along with the increase of TCTP expression, DNA damage repair-related proteins increased significantly. Reduction of TCTP expression enhanced the inhibition of 3Gy X-ray radiation on proliferation, migration and self-renewal ability of GBM cells.Our study showed that TCTP was highly expressed in GBM stem like cells and affected the malignant phenotype of GBM cells. The high expression of TCTP played a crucial role in maintaining self-renewal and cancer stem-like properties in GBM cells and tumorspheres which enriches the CSCs. Our study preliminarily showed that TCTP in involved in the radiation-induced regain of stemness of GBM non-stem cells. We also showed that the inhibition of TCTP is a promising target for GBM radiotherapy. |
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