Radiosensitization by siRNA-mediated knockdown of Erk1/2 in UMSCC-10A cells.

<p>(A) Radiosensitization by Erk1/2 knockdown. Cells were transfected using Lipofectamine 2000 and siRNA that targets Erk1/2. Seventy-two hours later, one portion of the cells was reserved for immunoblotting (top) and the other portion was plated for the clonogenic assay (bottom, mean ± SEM, n = 3). (B) The cell survival ratio was measured in UMSCC-10A cells that were treated with isoalantolactone, radiation alone or with a combination of the isoalantolactone and radiation after siRNA-mediated knockdown of Erk1/2. Isoalantolactone at a dose of 5 μM was added to the cultured cells 72 hours prior to radiation 4 Gy exposure. The results are presented as the mean±SEM from three independent experiments.^##<i>P</i><0.01, compared with the control. * <i>P</i><0.05, compared with the Erk1/2 siRNA. ** <i>P</i><0.01, compared with the control siRNA. (C) Representative images for a cell proliferation assay at difference time after cells by Erk1/2 silencing treated with isoalantolactone at 5 μM or combination of isoalantolactone and radiation 4 Gy. The results are presented as the mean±SEM from three independent experiments. ** <i>P</i><0.01, compared with the control cells. (D) Apoptosis was analyzed by flow cytometry using Annexin V-FITC and propidium iodide (PI) staining in UMSCC-10A cells. Cells were transfected using Erk1/2 siRNA and treated with radiation or isoalantolactone individually. The data are expressed as the means ± SEM of three independent experiments where similar results were obtained. **<i>P</i><0.01 compared with the control siRNA.