Fig. 1

Synergistic effects of bortezomib and IR on the viability of human oral cancer cells. a Concentration-dependent effects of bortezomib on the cell viability of SCC-9, SAS and SCC-25 cells. Cells were treated with 0, 10, 15, 20, 25 or 30 nM of bortezomib for 24 h. *p < 0.05, control versus bortezomib. b Dose-dependent effects of IR on cell viability of SCC-9, SAS and SCC-25 cells. Cells were treated with 0, 2, 4, 6, or 8 Gy of IR for 24 h. *p < 0.05, control versus IR. c Dose-dependent effects of bortezomib combined with IR on cell viability of SCC-9, SAS and SCC-25 cells. *p < 0.05, control versus IR + bortezomib. d Combination index (CI) plot of bortezomib, IR, or their combinations on SCC-9, SAS and SCC-25 cells. e Bortezomib decreases the clonogenic survival in SAS cells after IR treatment. Cells were stained with crystal violet. f Colonies containing> 50 cells were scored as positive. Data are presented as the mean ± standard deviation from three independent experiments. *p < 0.05, IR versus IR + bortezomib (25 nM), **p < 0.05, IR versus IR + bortezomib (30 nM)