Molecular Mechanism Of Radiosensitization Effect Of Paclitaxel On Human Oral Epithelium Carcinoma (KB) Cell Line

Background and Objective Paclitaxel is a radiosensitizer,which may stabilize microtubules,block the G2/M phase of the cell cycle and thus modulate the radioresponsiveness of tumor cells.However,its potential molecular mechanisms of the radiosensitization have not been well understood yet.This study was to investigate the radiosensitizing effect of paclitaxel on human oral epithelium carcinoma(KB) cell line and to reveal the molecular mechanism of radiosensitization.Method Inhibitory effect of different concentration of paclitaxel and different dose of radiation on KB cell line growth was analyzed using colony formation test,and radiosensitizing effect was measured by calculating the sensitizing enhancement ratio (SER) with multi-target single hit model.After exposed to paclitaxel and radiation,the cell cycle analysis of KB was performed by FCM.Human Oligo microarray was used to screen the genes showing altered expression related to radiosensitization of paclitaxel. The PRC1 and Cyclin B2 genes related to cell mitosis,screened by micoarray,were confirmed by real-time quantitative PCR.Result The proliferation of KB cells has been significantly inhibited by paclitaxel combined with ionizing radiation,the SERDo and SERDq were 2.40±1.87 and 12.23±2.81 respectively at the concentration of 20 nmol/L.The cell cycle characteristics have changed after drug treated combined with irradiation,the percentage of G1 phase cells decreased from 48.32±2.40 to 15.73±7.00(P＜0.01),the percentage of G2/M phase cells increased from 13.66±2.16 to 52.51±5.02(P＜0.01) and the percentage of apoptosis cells is 11.78±0.49%(P＜0.05),lower than the group of paclitaxel treated only. Screened by Oligo microarray,176 differential expressed genes had been identified to be related to radiosensitization of paclitaxel.10 genes had been found to be related to regulating cell division among these genes,including 2 up-regulated and 8 down-regulated genes.Especially,it had been confirmed that the expression of PRC1 and Cyclin B2 related to cell mitosis was decreased by RT-PCR and chip results.Conclusion The radiosensitization of paclitaxel on KB ceils may be explained that the down-regulated expression of PRC1 and Cyclin B2 resulted in inhibition of mitotic spindle formation,trigger multinuclear giant cell formation and get cell necrosis finally.