Fig. 3

NEDD8 expression alters the radiosensitivity of oral cancer cells. A RT‒PCR (upper) and Western blot (lower) analyses of NEDD8 mRNA and protein levels, respectively, in the parental (PT) HSC4 cells and HSC4 cells transfected with nonsilencing (NS) control and 2 independent NEDD8 shRNAs. B and C Representative crystal violet staining (B) and the results obtained from three independent colony formation assays (C) for the indicated HSC4 cell variants postexposure to the designed irradiation doses. D RT‒PCR (upper) and Western blot (lower) analyses of NEDD8 mRNA and protein levels, respectively, in parental HSC3 cells and HSC3 cells transfected with vector control (VC) and plasmid-containing wild-type or constitutively active (CA) NEDD8 gene. E and F Representative crystal violet staining (E) and data from three independent colony formation assays (F) for the indicated HSC3 cell variants after treatment with the designed irradiation doses. G and H Crystal violet staining (G) and histogram (H) for data from three independent experiments (EXPs) of colony formation assay for HSC4 cells pretreated with the indicated concentration of MLN4924 for 24 h followed by irradiation exposure at 4 Gy. The symbols “*”, “**” and “***” represent statistical significance at p < 0.05, 0.01 and 0.001, respectively