Inhibition of the Rac1-WAVE2-Arp2/3 signaling pathway promotes radiosensitivity via downregulation of cofilin-1 in U251 human glioma cells

The Ras-related C3 botulinum toxin substrate 1 (Rac1)-WASP-family verprolin-homologous protein-2 (WAVE2)-actin-related protein 2/3 (Arp2/3) signaling pathway has been identified to be involved in cell migration and invasion in various types of cancer cell. Cofilin-1 (CFL-1), which is regulated by the Rac1-WAVE2-Arp2/3 signaling pathway, may promote radioresistance in glioma. Therefore, the present study aimed to investigate the potential role of the Rac1-WAVE2-Arp2/3 signaling pathway in radioresistance in U251 human glioma cells and elucidate its affect on CFL-1 expression. Western blot analysis was performed to evaluate the protein expression of CFL-1. In the present study, Rac1 was inhibited by NSC 23766, WAVE2 was inhibited by transfection with short hairpin (sh)RNA-WAVE2 using Lipofectamine (TM) 2000 and Arp2/3 was inhibited by CK-666. Cell viability was measured using the 3-(4,5dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide assay, the cell migration ability was examined by a wound-healing assay, and the cell invasion ability was assessed using a Transwell culture chamber system. The results showed that inhibition of the Rac1-WAVE2-Arp2/3 signaling pathway using NSC 23766, shRNA-WAVE2 or CK-666 reduced the cell viability, migration and invasion abilities in U251 human glioma cells, concordant with a reduced expression of CFL-1. Furthermore, the expression of CFL-1 was significantly increased in radioresistant U251 glioma cells when compared with normal U251 human glioma cells. These findings indicate that inhibition of the Rac1-WAVE2-Arp2/3 signaling pathway may promote radiosensitivity, which may partially result from the down-regulation of CFL-1 in U251 human glioma cells.