Abstract: ObjectiveTo investigate the inhibitory effect of polyphyllin D on the proliferation of human chronic myelogenous leukemia (CML) cell line K562 cells and its mechanism. MethodsMethyl thiazolyl thiazolium (MTT) assay was used to evaluate the inhibition effect of polyphyllin D on the proliferation of K562 cells. Flow cytometry was used to determine the effect of polyphyllin D on the apoptosis of K562 cells. The related proteins were analyzed by Western blotting. ResultsThe MTT assay showed that polyphyllin D obviously inhibited the growth of K562 cells. The hemiinhibitory concentration (IC50) of 24 hours for the K562 cells was (0.8±0.1)μmol/L. Flow cytometric results demonstrated that polyphyllin D significantly induced apoptosis in a dosedependent manner, and the apoptosis rates of 0, 0.4, 0.8, 1.2 μmol/L polyphyllin D were (1.73±0.33)%, (14.47±2.57)%, (24.10±3.52)%, (31.51±4.09)% after 24 hours, with a significant difference (F=58.231, P＜0.001). Western blotting showed that polyphyllin D significantly downregulated the expression of Bcl2, and this was accompanied by upregulation of Bax, decrease of the Bcl2/Bax ratio, upregulation of cytochrome c and activation of caspase3. Otherwise, polyphyllin D obviously induced monocyte differentiation by increasing CD14 expression on the surface of K562 cells. ConclusionPolyphyllin D can significantly inhibit the proliferation of K562 cells, and the mechanism may be realized by inducing apoptosis and promoting monocyte differentiation.

Key words: Leukemia, Apoptosis, Cell differentiation, Polyphyllin D