Studies On Expression Of Vascular Endothelial Growth Factor In Acute Myeloid Eukemia And Effect On Harringtonine-induced Apoptosis Of HL-60 Cells

OBJECTIVE Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis by acting as a potent inducer of vascular permeability as well as serving as a specific endothelial cell mitogen. The importance of angiogenic factors such as VEGF,although clearly established in solid tumors,has not been fully elucidated in human hematopoietic neoplasms.This study is to investigate VEGF in the occurrence and progression of acute myeloid leukemia (AML). It comprises three parts:l.To estimate VEGF expression in the bone marrow cells from normal and adult AML patients and various leukemia cell lines.2 To explore the effect of autocrine VEGF on the abnormal proliferation of AML cells. 3. To observe the effect of VEGF 165 cDNA transfection on harringtonine -induced apoptosis of HL-60 cells.MATIERIALS AND METHODS Reverse transcription-polymerase chain reaction(RT-PCR) was used for detection of VEGF mRNA.VEGF concentrations in the cell cultural supernatant and the plasma from normal and AML patient bone marrows were determined by enzume linked immunosorbent assay(ELISA). HL-60 cells were transfected with the VEGF165cDNA sense vector ( HL-60/S ) and with the PcDNA3.1- vector ( HL-60/V ) as the control using lipofictamine .Cell proliferation was determined by MTT and colony forming assay in vitro. Flow cytometric Annexin - V-FITC/ PI dual labeling technique was perform to observe the effect of VEGF 165 cDNA transfection on apotosis and haningtonine -induced apoptosis of HL-60 cells.RESULTS VEGFmRNA expression was present in most of the humatopoietic cell lines HL-60 K562 Raji,but not in the Jurkat cells. The expression rate of VEGFmRNA in the bone marrow cells from newly diagnosed or relapsed AML patients (83.87%) was higher than the rates in normal subjects(31.25%)and AML patients with allogenic bone marrowtransplantation(41.67%). But there was no significant difference between de novo AML patients and AML patients in complete remission(CR) after a median follow-up of 6 months. VEGFmRNA was positive in 15 of 15 cases of refractory AML patients,and in 11 of 16 cases of non-refractory AML patients.Refractory and non-refractory AML patients had higher mean plasma VEGF levels than the normal donors and AML patients with transplantation did,without significant differences observed in the latter 2 groups . With also significant difference between them,refractory and non-refractory AML groups had respectively 11.0 and 7.0 - fold higher VEGF levels in the culture supernatant than the normal donor group did. Baseline VEGF levels in the plasma of patients in CR after a median follow-up of 6 months were significantly lower than those patients with newly diagnosed or relapsed AML,and higher than AML patients with allogenic bone marrow transplantation and normal donor.PCR> RT-PCR method were applied to confirmed that VEGF 165 cDNA had transfected in HL-60 cell line. HL-60/S transfectants exhibited a 3 -fold increase in VEGF secretion.,and showed an increaseing growth rate and. colony forming efficiency as compared to HL-60/V. HL-60/S had less apoptotic cells than HL-60/V in the same culture condition. High expression of VEGF could deduce the harringtonine -induced apoptosis of HL-60 cells.CONCLUSION The abnormality of VEGF transcription and translation expession may play an important role in the development of AML. VEGF might be used to evaluate prognosis of AML. VEGF plays an important role in the abnormal proliferating and apoptosis in AML cells through an autocrine mechanism.High expression of VEGF could deduce the harringtonine -induced apoptosis of HL-60 cells.