| Objective: Gliomas account for about 50% of primary brain tumors,clinical treatment results are not significant. Surgical operation is the main treatment method,but it's hard to eradicate gliomas because of the tumors'infiltration growth pattern. In addition, the radio-sensitivity of glioma therapeutic is very low, and chemotherapy is easy to produce drug resistance, so a variety of treatment programs focus on the combinaed therapy. VEGF (Vascular Endothelial Growth Factor) is a kind of signal peptide structure of glycoprotein, its expression levels positively correlate with the occurrence and the development of malignant gliomas. Cyclin B1 is a G2/M phase check point regulatory protein, which plays an important role on cell proliferation regulation, and is also highly expressed in glioma cells. Thalidomide, a non-barbiturate drug, is used as a sedative antiemetic drug, and shows a significant teratogenic effect, has once been banned. In the follow-up study of the teratogenic effects by thalidomide, we found that drug could inhibit the expression of VEGF, thereby inhibiting angiogenesis, anti-tumor proliferation, which suggest an important value on tumor research. The purpose of this study is to find out the inhibition of the glioma cells proliferation; the effect of radiation sensitivity in glioma cell line U251 treated with thalidomide and the potential mechanism.Methods: Survival of the cells was assessed by MTT assay; 3H-TdR incorporation assay were used to investigate the inhibition of DNA synthesis by thalidomide alone and combined with X-ray;The cell viability was assessed by colony formation assay. Thalidomide inhibition of the invasive ability was observed by cell scratch test;VEGF mRNA expressions were evaluated using RT-PCR assay. Cell cycle distribution was analyzed by flow cytometry. Protein expression was detected by Western blot analysis.Results:①Thalidomide cytotoxicity slowly increased in accordance with the concentration of drugs.②Cells have overgrown the middle blank in the control group after cultured 48h,and the inhibition was enhanced with the concentration of thalidomide raising up.③The concentration of thalidomide and radiation dose had interaction on U251 cells survival (p<0.01);When the survival rate of glioma U251 cells is 50%,the radio-sensitization factors of 100μg/mL thalidomide is 1.51.④Thalidomide inhibit DNA synthesis depended on the concentration of thalidomide and radiation dose.⑤Thalidomide markedly downregulated VEGF mRNA, combined with X-ray showed a synergistic action.⑥Low dose X-ray induced VEGF protein expression in 24h. Ionizing radiation induced Cyclin B1 expression,but did not remove G2/M arrest combined with thalidomide.⑦Cell cycle analysis showed that: thalidomide change cell cycle distribution.The percentage of the cell population in G0/G1 was at most,but had no statistical significance.Conclusion:①Thalidomide was a low toxicity to U251 cell.②Thalidomide had a better radio sensitization effects.③Thalidomide inhibit DNA synthesis of U251 cells.④RT-PCR test results showed that thalidomide significantly inhibited VEGF mRNA expresison.Western Blot test results showed that low dose X-ray induced VEGF protein expression.In short, the experiment results show that thalidomide have some effects of radiosensitivity on glioma cell U251, by inhibiting VEGF mRNA expression level.
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