| Objective: To investigate the inhibitory and apoptosis-inducing effects of parthenolide (PTL) on human leukemia K562 cells and leukemia stem cells(LSC) in K562 cell population. Method: MTT assay was used to detect the proliferating activity of K562 cells, and the cellular apoptosis was assed with Annexin V/PI double staining. Flow cytometry (FCM) was employed to determine the relative proportion of LSC in K562 cells. The self-renewal and proliferating potential were examined with methylcellulose colony-forming units(CFU) assay. Result: By use of MTT assay, we found PTL had evident inhibitory effect on the proliferation of K562 cells, the 50% inhibitory concentration (IC50) values were 17.1 μmol?L-1, 8.67 μmol?L-1 and 9.42 μmol?L-1 for 24, 48 and 72 h, respectively. After administration with 5 μmol?L-1 and 10 μmol?L-1 PTL, the apoptotic rate of K562 cells was (49.56?.11)% and (71.88?.12)%, and (52.63?.14)% and (57.50?.47)% in LCS-like(CD34 CD38－) cells in K562 cell population, respectively. A slightly increase of relative content of LSC in K562 cells was observed, and there was an 15-fold increase in the higher concentration of PTL-treated cells. The methylcellulose colony-forming units assay showed a 24.1% to 89.2% decrease in the CFU of K562 cells administrated with 0.5 μmol?L-1 to 4.0 μmol?L-1 PTL, and the CFU of the surviving cells increased by 5.0% to 50.0% on condition that K562 cells were pre-treated with 5 μmol?L-1 to 15 μmol?L-1 PTL for 48 h. Conclusions: PTL eminently inhibits proliferation of K562 cells and LSC in K562 cells, and induces to apoptosis. |