[Combined Effect of Bortezomib and Homoharringtonine on K562 Cells and their Mechanisms]

To explore the effects of BTZ plus HHT on proliferation and apoptosis of K562 cells, and to clarify the relationship between the mechanism inderlying the effect of BTZ plus HHT on K562 cells and BCL-2, BAX, MCL-1 proteins.

The K562 cells were divided into 4 groups by different treatment: BTZ(20 nmol/L), HHT(40 ng/ml), BTZ(20 nmol/L)+HHT(40 ng/ml) and control. The proliferation inhibition rates of K562 cells in each group were detected by using MTT, and the early apoptosis rates of K562 cells in each group were assayed by using flow cytometry with Annexin V-FITC/PI staining. The proteins level of BCL-2, BAX and MCL-1 in each group were examined by using Western blot.

The inhibition rate of K562 cell proliferation in combined group was higher than that in BTZ, HHT alone group(P<0.01). The early apoptosis rate of K562 cells in combined group was increased significantly in comparison with BTZ and HHT alone group(P<0.05). The BCL-2 protein level of K562 cells in combined group was significantly lower than that in BTZ and HHT alone group(P<0.05). BAX protein level of K562 cells in combined group was higher than that in BTZ and HHT alone group(P<0.05). The Orders of the MCL-1 protein level of K562 cells in 4 groups were BTZ>Control>BTZ plus HHT>HHT(P<0.05 ).

The combination of BTZ and HHT exerts the synergistic effect of anti-proliferative activity and induces apoptosis against K562 cells in vitro. The combination can induce apoptosis of K562 cells via suppression of BCL-2 protein and up-regulation of BAX protein. HHT can increase the sensitivity of K562 cells to BTZ by down-regulating the expression of MCL-1 protein.