[Mechanism of mTOR Pathway in K562 cell Apoptosis Induced by Homoharringtonine].

Objective: To 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.

Methods: K562 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.

Results: The 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.

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