[Relationship between BH3 mimetic S1 and expression of BCL-2 family members in acute myeloid leukemia].

Objective:This study was to investigate the molecular biomarkers of apoptosis induced by BH3 mimetic S1 in human primary AML cells.Methods:Mononuclear cells were isolated from 27 newly diagnosed AML samples.Apoptosis was analyzed by flow cytometry.IC_(50) value of S1 on these samples was determined by XTT assay.The expression level of BCL-2 family members and phosphorylated BCL-2 were assessed by Western blot with subsequent semiquantitatively densitometric analysis.XTT assay was performed to determine the cell viability of the combined use of S1 and MEK/ERK inhibitor PD98059.The interactions between BCL-2 and pro-apoptosis proteins were tested by coimmunoprecipitation.Results:The flow-cytometry detection showed that S1 induced the apoptosis of primary AML cells.Based on the responses,27 primary samples could be classified into three groups:(1) a sensitive group(12 of 27 cases)with IC_(50) 14 μmol/L,(2) an intermediate group(8 of 27 cases) with IC_(50) of 14-30 μmol/L and(3) a resistant group(7 of 27cases) with IC_(50) 30 μmol/L.The ratio of pBCL-2/(BCL-2 + MCL-L) showed a good linear correlation with the IC_(50) values.(R~2 =0.71,P0.0001).PD98059 suppressed BCL-2 phosphorylation.When PD98059 suppressed BCL-2phosphorylation,the apoptotic rate of drug-resistant cells induced by S1 increased from 9.8%to 64.5%(combination index,CI=0.4),accompanied by more dissociation of BCL-2 heterodimers.Conclusion:The combination of S1 with PD98059 decrease pBCL-2 level of AML patients and inhibits of the anti-apoptotic function of BCL-2 through enhancing the dissociation of BCL-2 heterodimers.