Proliferation Inhibition And Radiosensitization Of 6-bromoisovanillin On Human Glioma U-251 Cells

ObjectiveTo investigate effects of vanillin derivative bromoisovanillin (6-bromine-5-hydroxyl-4-methoxy-benzaldehyde, BVAN08) on the growth inhibition, the radiosensitization of human glioma cell line U-251, and the relative mechanism to provide further convincing evidences and experimental data for exploring BVAN08 as a new anticancer drug.MethodsMTT was performed to analyze the cytotoxicity and proliferation inhibitive effect of BVAN08; colony-forming ability assay was used to determine the survival curve of U-251 cells exposed to different doses of 60Coγirradiation, the radiosensitization of U-251 cells by BVAN08-which treated cells before the irradiation or after irradiation. Flow cytometry was used to detect the cell cycle changes and apoptosis induction; Cellular morphology changes were observed by light microscope; and the autophagic cell death was observed by TEM (transmission electron microscope); Expression changes of DNA-PKcs protein were detected by Western blot.ResultsThe MTT analysis data indicated an dose-dependently and time-dependently inhibitive effect of BVAN08 on the proliferation of glioma U-251 cells at the concentrations from 10μmol·L-1 to 100μmol·L-1; The IC50 of BVAN08 treatment for 48h and 72h were 55.33μmol·L-1 and 52.70μmol·L-1 respectively; An obvious G2/M arrest (63.3%) was observed in U-251 cells after 12h treatment with 60μmol·L-1 BVAN08 and apoptosis and autophagic cell death were also triggered at the same time. BVAN08 shows obvious radiosensitization on U-251 cells, and the most effective sensitizing effect was obtained when cells were pretreated with BVAN08 12h before irradiation. The enhanced ratio of radiosensitization (cell killing) by 20μmol·L-1 BVAN08 on 2 Gy irradiation is 3.14. Western blotting analysis showed the expression of DNA-PKcs was obviously inhibited by BVAN08.ConclusionsBVAN08 inhibits the proliferation of human glioma cells via inducing apoptosis and autophygic cell death, and exhibiting radiosensitizing effect. The anticancer activity of BVAN08 could be fulfilled through two aspects, killing the cancer cells directly and sensitizing cancer cells to radiotherapy. The radiosensitization of BVAN08 may be related with G2/M arrest and the inhibition of DNA-PKcs expression which is a critical component involved in the non-homologous end joining pathway of DNA double-strand breaks repair.