AIM：To study the potentiation of anti-tumor effect induced by cytosine arabinoside (AraC)with(-)-epigallocatechin-3-gallate(EGCG).METHODS:Growth curve method and MTT assay were used to measure the cytotoxic effect of AraC alone or in combination with EGCG on HL-60 cells,Folw cytometry was used to study the cell cycle distribution of HL-60 cells.Nullification assay was used to examine whether EGCG would nullify the rescue effect of dexoycytidine (dCdR)to AraC,Western blot analysis was empolyed to investigate bcl-2 expression .Inracellular Ca^2+ assay was evaluated.RESULTS:Inhibition of HL-60 cell proliferation induced by AraC was enhanced by EGCG,with multiplication time prolonging from 48h to 70h and growth saturation density decreasing from 5.78 to 5.54 .The MTT results indicated that IC50 was decreased from(0.34±0．29）μmol/L（AraC alone)to(0.11±0.09）μmol/L（P<0.05)(in combination with ECGC).Cell cycle analysis in dicated that Arat AraC blocked HL-60 cells in G1 phase,inhibited cells in S phase,EGCG had no effect on cell cycle at the current concentration,but enhanced the cell arrest by AraC.Nullification assay indicated that IC50 was 0.03 μmol/L(AraC alone)，increased to 0.02 mmol/L when rescued with dCdR,and finally decreased to 4.8μmol/L when addition with EGCG.The expression of bcl-2 protein was down-regulated after treatment with AraC in combination with EGCG.the intracellular Ca^2+ was increased after treatment by AraC in combination with EGCG.CONCLUSION:The combination with EGCG could enhance the anti-tumor effect of AraC on HL-60 cells.

完成机构：[1]第一军医大学第二附属医院药理科，广州510280 [2]中国医学科学院北京北京协和医科大学医药生物技术研究所肿室，北京100080

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