OBJECTIVETo investigate the effect of homoharringtonine (HHT) on proliferation and apoptosis of CML cell line K562 cells and to explore its possible mechanism through mTOR pathway.

METHODSK562 cells were cultured with different concentrations of HHT or in its combination with mTOR inhibitor rapamycin (RAPA) for 24 hours. The cell viability was analyzed by CCK-8 assay, the cell apoptosis was detected by flow cytometry, the expressions of BCL-6, Caspase-3 and mTOR signal pathway related proteins was assayed by Western blot, the expression of BCL-6 mRNA was determined by RT-PCR.

RESULTSThe HHT inhibited proliferation and induced apoptosis of K562 cells in a concentration-dependent manner(r=0.970). With the increasing of HHT concentration, the expression level mTOR signal pathway related proteins increased(r=0.908), while the mRNA and protein expression levels of BCL-6 decreased(r=-0.961, r=-0.981), as compared with the HHT alone, the combination of HHT with RAPA could down-regulate the expression of mTOR signal pathway related protein and caspase-3, and up-regulated expression of BCL-6.

CONCLUSIONHHT induces apoptosis of K562 cells by inhibiting BCL-6 expression through mTOR signal pathway.