This study was aimed to investigate the effect of proteasome inhibitor MG-132 at different doses on cultured K562 cell apoptosis. MTT assay was used to observe the activity of K562 cell proliferation inhibition rate after treating for 48 hours at different doses (0, 2, 4, 8, 16, 32 micromol/L). Immunocytochemistry was used to detect the NF-kappaB activity and glucocorticoid receptor (GR) expression. Flow cytometry was used to determine the K562 cell apoptosis. The results indicated that proliferation inhibition rate of K562 cells after treated for 48 hours showed dose-dependent, the inhibitory rates of cell proliferation in test groups were significant higher than that in control group, and the effect in 32 micromol/L test group was the most obvious (45.24 +/- 4.12)% (p < 0.05). The NF-kappaB activity and GR expression after treating for 48 hours showed dose-dependent. Compared with control group, the NF-kappaB activities in test groups were lower (p < 0.05), and the NF-kappaB activity in 32 micromol/L test group was the lowest (63.60 +/- 2.95); the GR expression in test groups was higher (p < 0.05), and the GR expression in 16 micromol/L test group was the highest (75.62 +/- 2.70). The K562 cell apoptosis rate after treating for 48 hours also showed dose-dependent. Compared with control group, the K562 cell apoptosis rates in test groups were higher (p < 0.05), the K562 cell apoptosis rate in 32 micromol/L test group was the highest (21.37 +/- 2.02)%. It is concluded that the MG-132 may induce K562 cell apoptosis and proliferation inhibition through up-regulation of NF-kappaB activity and down-regulation of GR expression both in dose-dependent manner.