Abstract: AIM: To investigate the effect of recombinant human leukemia inhibitory factor (rh-LIF) on human myeloid leukemia cell line HL-60. METHODS: HL-60 cells were treated with various concentrations of rh-LIF (10-4 000 U·ml^-1) for a few days, cell cycle and cell apoptosis rate were analysed by flow cytometry.Cell apoptosis was also observed under microscope with TUNEL.Expression of P53 protein after addition of rh-LIF (800 U ·ml^-1) was observed by immunohistochemistry, and p53 mRNA and bcl-2 mRNA were assayed by in situ hybridization. RESULTS: Cell apoptosis rates (CAR) in rh-LIF groups by flow cytometry were higher than those in control group, and 1 000 U·ml^-1 rh-LIF had the most potent effect on induction of apoptosis. There was also a marked increase of positive-cells by TUNEL method in a concentration-dependent pattern on the 3rd day after addition of rh-LIF (10-1 000 U · ml^-1).Following addition of rh-LIF (800 U·ml^-1) and incubation for 2 to 6 days, the expression of P53 protein and p53 mRNA of HL-60 cells increased obviously, and bcl-2mRNA expression decreased in a time-dependent pattern(vs control, P <0.01). CONCLUSION: rh-LIF can induce apoptosis, and the effects may be related to the increase of P53 protein and decrease of bcl-2 mRNA expression.

Key words: recombinant human leukemia inhibitory factor, apoptosis, HL-60 cell, bcl-2, p53