Objective: To study the expression of X-linked inhibitor of apoptosis protein (XIAP)-associated factor 1 (Xaf1) in human leukemia HL-60 and K562 cells treated with interferon alpha (INFalpha) and the demethylating agent 5-AZA-CdR, and observe the synergetic antitumor effect of Xaf1 inducer and (-)-epigallocatechin-3-gallate (EGCG).
Methods: Human leukemia HL-60 and K562 cells were treated for 48 h with 1000 U/ml INFalpha and different doses of 5-AZA-CdR, and the mRNA expressions of both Xaf1 and XIAP were measured by RT-PCR. The leukemia cells were also treated with the optimal Xaf1 inducer in combination with EGCG, after which flow cytometry was employed to examine the changes in the members of the Bcl-2 family, mitochondrial transmembrane potential and apoptosis.
Results: As the dose increased, 5-AZA-CdR dose-dependently up-regulated the mRNA expression of Xaf1 in HL-60 and K562 cells; INFalpha treatment also resulted in increased Xaf1 expression, but 5 micromol/L 5-AZA-CdR showed the most potent effect. Neither INFalpha nor 5-AZA-CdR caused significant changes in XIAP expression. Combined treatment with 5-AZA-CdR and EGCG altered the expressions of Bcl-2 (Bcl-xl) and Bax in HL-60 and K562 cells, decreased the mitochondrial transmembrane potential and induced cell apoposis, and the two agents exhibited obvious synergistic effect.
Conclusion: INFalpha and 5-AZA-CdR can induce Xaf1 mRNA expressions in HL-60 and K562 cells, and the effect of 5-AZA-CdR was dose-dependent. 5-AZA-CdR and EGCG induces apoptosis of leukemia cells in vitro, and they exhibits obvious synergetic effects.