Objective: To investigate the inhibitory and apoptosis-inducing effects of parthenolide (PTL) on human leukemia K562 cells and its leukemia stem cells (LSC).
Method: MTT assay was used to detect the proliferating activity of K562 cells, and the cellular apoptosis was assayed 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 significant inhibitory effect on the proliferation of K562 cells, the 50% inhibitory concentration (IC50) values were 17.1, 8.67, 9.42 micromol x L(-1) for 24, 48 and 72 h, respectively. After administration with 5 micromol x L(-1) and 10 micromol x L(-1) PTL, the apoptotic rate of K562 cells was (49.56 +/- 5.11)% and (71.88 +/- 2.12)%, and (52.63 +/- 4.14)% and (57.50 +/- 4.47)% in LCS-like (CD34 + CD38-) cells in K562 cell population, respectively. A slightly increase of relative content of LSC in K562 cells was observed. There was an 15-fold increase in the higher concentration of the 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 micromol x L(-1) to 4.0 micromol x 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 micromol x L(-1) to 15 micromol x L(-1) PTL for 48 h.
Conclusion: PTL eminently inhibits proliferation of K562 cells and LSC in K562 cells, and induces the cell apoptosis.