Abstract:

Objective   To observe the radiosensitivity of VPA to C6 glioma cells in vitro, so as to provide experimental evidences to the therapy of cerebral gliomas. Methods   Rat C6 glioma cells were cultured commonly in vitro. MTT assays was used to measure the proliferation inhibition rate of C6 glioma cells with VPA in different concentrations (0,0.25,0.5,1,2,4mmol/L) and different durations (24,48,72h) to choose the appropriate concentration and time. C6 cells incubated with 0.5mmol/L VPA were exposed to different doses of X-ray irradiation (IR) (0,2,4,6,8Gy). Cloning experiments were used to determine the radiosensitizing effect of VPA. Flow cytometry double staining with Annexin V-FITC and propidium iodide (PI) was used to detect the effects of various concentrations of VPA on the apoptosis rate of C6 glioma cells. Trials were divided into the control group, the medication group, the irradiated group and the joint group. Real time PCR was used to detect the expression of Bcl-2 and Bax. Results   VPA inhibited the proliferation of rat C6 glioma cells in vitro significantly in a time and concentration dependent manner (P<0.05). VPA at the concentration of 0.5mmol/L had a lower toxicity on C6 glioma cells and enhanced the killing effect of X-ray on C6 cells. The sensitization enhancement ratio (SER) was 1.30. VPA induced apoptosis in C6 cells, the apoptosis rate was increasing along with the concentration of VPA.The difference of the apoptosis rate among different concentrations was statistically significant(P<0.05). On the transcriptional level translation, after the treatment with VPA, the expression of Bcl-2 decreased, whereas the expression of Bax increased. Conclusion   VPA inhibits the growth of rat C6 glioma cells in a dose and time dependent manner. Low concentration of VPA is low-toxic and can enhance the radiosensitivity of C6 glioma cells, and the mechanisms for this action might include directly inhibiting cellular proliferation, inducing apoptosis and regulating the expression of apoptosis-related genes.

Key words: Histone deacetylase inhibitors; Sodium valproate; Gliomas; C6 cells; Radiosensitivity; Apoptosis