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Published on: October 11, 2018
[Relationship between BH3 mimetic S1 and expression of BCL-2 family members in acute myeloid leukemia]
Xiao-Bo Wang1, Ming Shi2, Li-Jun Mu1
1Department of Hematology, The Second Affiliated Hospital of Dalian Medical University, Dalian 116023, Liaoning Province, China.
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 semi-quantitatively 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 co-immunoprecipitation.
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 27 cases) with IC(50)>30 µmol/L. The ratio of pBCL-2/(BCL-2+MCL-1) showed a good linear correlation with the IC(50) values. (R(2) = 0.71, P < 0.0001). PD98059 suppressed BCL-2 phosphorylation. When PD98059 suppressed BCL-2 phosphorylation, 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.
Insights
BH3 mimetic S1 induces apoptosis in acute myeloid leukemia (AML) cells. Combining S1 with PD98059 reduces BCL-2 phosphorylation, enhancing S1
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Death Mechanisms
Background:
- Acute myeloid leukemia (AML) is a heterogeneous hematologic malignancy.
- BH3 mimetics are a class of drugs targeting BCL-2 family proteins to induce apoptosis.
- Understanding molecular biomarkers of drug response is crucial for AML treatment.
Purpose of the Study:
- To investigate molecular biomarkers of apoptosis induced by the BH3 mimetic S1 in human primary AML cells.
- To evaluate the efficacy of combining S1 with a MEK/ERK inhibitor (PD98059) in AML.
- To elucidate the role of BCL-2 phosphorylation in S1 resistance.
Main Methods:
- Primary AML mononuclear cells were isolated and treated with S1.
- Apoptosis was assessed by flow cytometry and cell viability by XTT assay.
- Expression of BCL-2 family proteins and phosphorylated BCL-2 was analyzed by Western blot.
- Co-immunoprecipitation was used to study protein interactions.
Main Results:
- S1 induced apoptosis in primary AML cells, with sensitivity varying among patients.
- A correlation was found between the ratio of pBCL-2/(BCL-2+MCL-1) and S1 IC(50) values.
- Combining S1 with PD98059 suppressed BCL-2 phosphorylation and significantly increased apoptosis in resistant cells.
Conclusions:
- BCL-2 phosphorylation is a key mechanism of resistance to BH3 mimetic S1 in AML.
- Inhibiting BCL-2 phosphorylation with PD98059 enhances S1-induced apoptosis.
- Combination therapy targeting BCL-2 phosphorylation may overcome S1 resistance in AML patients.
