OBJECTIVETo explore the effects of homoharringtonine (HHT) alone or combined with imatinib (IM) on K562 cell proliferation and apoptosis, as well as the mRNA and protein expression of BCL6.

METHODSThe CCK-8 was used to detect the inhibitory effect of drugs on cell growth, the flow cytometry was used to detect the cell apoptosis. The expression of BCL6 protein was assayed by Western blot, and BCL6 mRNA expression was detected by RT-PCR.

RESULTSHHT alone displayed a proliferation inhibition effect with dose- dependent manner, and induced apotosis; after combination of HHT and IM drugs, both the inhibitory rate and the apoptosis rate were significantly increased compared with the drug alone(P<0.05). Western blot showed that the expression of BCL6 protein was down-regulated after being treated with HHT, however, the BCL6 protein was up-regulated after being treated with IM . The effect of drug combination showed that BCL6 protein significantly down-regulated(P<0.05 ). The expression of BCL6 mRNA was decreased both in the treatment of HHT or IM alone when compared with control. And the effect of drug combination showed that BCL6 mRNA expression was more significantly down-regulated(P<0.05 ).

CONCLUSIONHHT can inhibit the K562 cell proliferation and induce apoptosis of K562 cells. Combination of IM with HHT shows a significant synergistic effect, the mechanism may be associated with down-regulation of BCL6.