Effect of SSH1/SSH2 expression changes by shRNA in glioma cell lines on response to radiotherapy and cofilin-1 reactivation.

Abstract

e13505 Background: Radiotherapy has become the most important treatment for malignant glioma following surgery. However, development of radioresistance in glioma cells limits therapeutic efficacy. The slingshot (SSH) family of phosphatases is a potent regulator of Cofilin-1 activation. Methods: We investigate the role of SSH1(slingshot protein phosphatase 1) and SSH2 in radioresistance via using shRNA to block SSH1/2 expression in U251 and U373 cells as well as established radioresistant U251 (RR-U251) and U373 (RR-U373) cells. Results: We found that both SSH1 and SSH2-shRNA efficiently sensitized glioma cells to radiation with a sensitization enhancement ratio (SER) of 1.01-1.73. In SSH1-silenced cells, the cell viability, migration, and invasion abilities following radiation were remarkably reduced and radiation induced cell apoptosis was markedly enhanced compared with control cells. While in SSH2-silenced cells, the alterations were not as significant. Furthermore, the result of Western-blot suggested that radiosensization of SSH1/SSH2 silencing was mediated by inhibiting reactivation of phosphorylated CFL-1. Conclusions: Our study demonstrated that SSH1 and SSH2 are valid radiosensitizing targets in not only normal glioma cells but radioresistant lines, suggesting a novel therapeutic strategy to improve the efficacy of radiotherapy in patients with glioma.