Fig. 4

Decreased c-Myc protein induced by matrine and rescued by proteasome inhibitor. a Effect of matrine on c-Myc protein expression in NK92 cells. NK92 cells were treated with matrine at 1.96 mM for 48 h, and c-Myc protein levels were measured by western blot. b c-Myc mRNA levels in NK92 cells were determined by quantitative RT-PCR at 24 h after matrine treatment at 0, 1.2, 2.4, and 3.6 mM (*p < 0.05, **p < 0.01 compared to 0 mM group). c CHX chase assay for the half-time of c-Myc. NK92 cells were treated with or without 1.96 mM matrine for 12 h. Cells were then treated with CHX (100 μg/mL) for the indicated minutes, and western blotting was performed. d c-Myc levels were quantified relative to GAPDH levels and graphed as percent c-Myc protein remaining after CHX treatment. Half-lives of c-Myc were calculated from exponential line equations and shown for each treat. e c-Myc protein levels were determined at 6 h post-treatment of MG132 and/or matrine, and (f) the relative intensities of target proteins were normalized to those of GAPDH. Analyses in triplicates. (*p < 0.05, **p < 0.01)