OBJECTIVETo investigate the inhibitory and apoptosis-inducing effects of parthenolide (PTL) on human leukemia K562 cells and its leukemia stem cells (LSC).

METHODMTT 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.

RESULTBy 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.

CONCLUSIONPTL eminently inhibits proliferation of K562 cells and LSC in K562 cells, and induces the cell apoptosis.