Keywords: 
• cytarabine /
• daunorubicin /
• all-trans retinoic acid /
• HL-60 /
• combination /
• apoptosis /
• anti-apoptosis protein

Abstract: Objective To investigate variance of apoptosis and correspondingly mechanism in HL-60 cell line in vitro by different combinations adminstration of three drug including cytarabine,daunorubicin and all-trans retinoic acid.Methonds HL-60 cell line was cultured in vitro,cell suspension was divided into different 7 groups which's density was 2.0×10⁵/ml : Group A: control;Group B:Ara-C and ATRA were simultaneous applied in cells for 48 h(Ara-C+ATRA 48 h);Group C: ATRA and Ara-C subsequently administrated respectively for 24 h that is ATRA was applied first for 24 h,then followed by Ara-C for 24 h.Group D: Ara-C and ATRA subsequently administrated respectively for 24 h that is Ara-C was applied first for 24 h,then followed by ATRA for 24 h;Group E: DNR and ATRA simultaneously administrated for 48 h;Group F: DNR and ATRA subsequently administrated respectively for 24 h that is DNR was applied first for 24 h,then followed by ATRA for 24 h.Group G: ATRA and DNR subsequently administrated respectively for 24 h that is ATRA was applied first for 24 h,then followed by DNR for 24 h.All drug concentrations of Ara-C,DNR and ATRA were 1.0×10^-7 mol/L.The ratio of apoptosis cells was evaluated by flow cytometry.Anti-apoptosis protein Bcl-2 was checked by Western Blotting. Results The ratio of cell apoptosis in D group increase slightly,the rate of increase in apoptosis was(50±14.7) %,its protein Bcl-2 disappeared.Compared with control group,both two groups including E and G groups caused the apoptosis ratio significant higher.The alive cells' ratio in E group was reduced to the highest degree and the amount of dead cells increased to a degree of(4.00±0.56) %.Anti-apoptosis protein Bcl-2 in E,F,G groups all disappeared. Conclusion Combination DNR and ATRA simultaneously can effectively decrease HL-60 survival.Three ways of combination DNR with ATRA can signifi- cantly cause protein Bcl-2 disappear.But low dose of Ara-C was administrated first then followed by ATRA can not only increase slightly the ratio of apoptosis of HL-60 cell,but also inhibited anti-apoptosis protein Bcl-2 to express and effectively controled the way of HL-60 cell's death to apoptosis,and we concluded that this combination is the most potentiall way.