This study was aimed to investigate the effects of proteasome inhibitor bortezomib (Velcade, PS-341) on the activation of NF-kappaB and the expression of intercellular adhesion molecule-1 (ICAM-1) in K562 cells. The K562 cells were incubated in the culture of RPMI 1640 with 10% calf serum in 12-well plates and exposed to 0, 10, 20, 30, 50 and 100 nmol/L of bortezomib for 6 hours. The activation of NF-kappaB was analyzed by SP immunohistochemistry, meanwhile RT-PCR was performed to detect expression of ICAM-1. The results showed that the activation of NF-kappaB and the expression of ICAM-1 in K562 cells decreased significantly after bortezomib treatment. The inhibitory effect on ICAM-1 was probably related with the activity suppression of NF-kappaB. It is concluded that proteasome inhibitor bortezomib downregulates the expression of K562 cell ICAM-1 by inhibiting the activity of NF-kappaB, which provides a new way for the target therapy in acute leukemia.