[Role of vascular endothelial growth factor (VEGF) in development and progress of refractory acute myeloid leukemia].

Background & Objective: The mechanism of refractory leukemia is very complex. Recent studies have shown that overexpression of vascular endothelial growth factor (VEGF) was detected in bone marrow from acute myeloid leukemia (AML) patients, suggesting it may play an important role in AML. However,the effect of VEGF in the development of refractory leukemia is not clear. The current study was designed to explore the effect of overexpression of VEGF on the abnormal proliferation and harringtonine-induced apoptosis of HL-60 cells and to observe VEGF expression in the progression of refractory AML.

Methods: HL-60 cells were transfected with the VEGF(165)cDNA sense vector (HL-60/VEGF(165)) and with the pcDNA3.1-vector (HL-60/neo) as the control using lipofectamine. Reverse transcription-polymerase chain reaction (RT-PCR) was used to determine VEGF mRNA. VEGF concentrations in the cell cultural supernatant were determined by enzyme linked immunosorbent assay (ELISA). Cell proliferation was determined by MTT and colony forming assay in vitro.Flow cytometric Annexin-V-FITC/PI dual labeling technique was performed to observe the effect of VEGF(165) cDNA transfection on harringtonine-induced apoptosis of HL-60 cells. ELISA was used to detect VEGF concentrations in the plasma from refractory and non-refractory AML patient.

Results: The mean VEGF concentration in the cell cultural supernatant of HL-60/VEGF(165) cells (399.07+/-12.45 ng/L) was 2-folds higher than that in HL-60/neo cells (184.45+/-10.53 ng/L)(P< 0.01). The VEGF(165)cDNA sense vector transfected HL-60 exhibited a 2-fold increase in VEGF secretion. The growth rate of HL-60/VEGF(165) cells was significantly higher than those of the controls, and colony formation capacity of HL-60/VEGF(165) increased significantly(P< 0.05);the colony numbers were (157.00+/-17.00)/500 cells and (110+/-12.90)/500 cells for HL-60/VEGF(165) and HL-60/neo, respectively. HL-60/VEGF(165) had less apoptotic cells than HL-60/neo in the same culture condition. High expression of VEGF could reduce the harringtonine-induced apoptosis of HL-60 cells. Refractory AML patients had higher mean plasma VEGF levels (558.90+/-271.25 ng/L) than non-refractory patients(392.54+/-217.82 ng/L), and significant difference was observed between them (P< 0.05).

Conclusion: VEGF expression in refractory AML patients is higher than that in non-refractory AML patients. VEGF plays an important role in the abnormal proliferation and apoptosis of AML cells. High expression of VEGF could reduce the harringtonine- induced apoptosis of HL-60 cells.