Correlation Of Expression Of Vascular Endothelial Cell Growth Factor And KDR Receptor To Invasion Potential In Acute Leukemia

Objective: Angiogenesis is an absolute requirement for the growth, proliferation and migration of solid tumor cells.Vascular endothelial cell growth factor (VEGF) is the best characterised positive regulator for angiogenesis. VEGF levels have become an independent predictor of outcome in patients with solid tomor. The two primary cellular receptors KDR. Studies suggest that expression of KDR is important for angiogenesis and migration of solid tumor whereas Flt-1 may be more important for vascular remodeling. High expression of VEGF and KDR in several human tumor have been demonstrated. Furthermore, disruption of KDR signaling resulted in inhibition of tumor growth and tumor metastasis. More recently, a mounting body of evidence has been accumulating suggesting a high microvessel density in patients with acute leukemia. Overexpression of VEGF is associated with increased angiogenesis. Late studies suggest overexpression of VEGF in some leukemic cell lines. KDR was thought to be exclusively expressed by adult endothelial cells. However , it has recently been shown that KDR is present on a subset of primitive hematopoietic stem cells as well as on some leukemic cell lines.Leukemias orginate from hematopoietic stem cells at different stages of their maturation and differentiation. So, we hypothesized that VEGF and its receptor KDR may play important roles in the development of leukemia. The purpose of the current study is to investigate that theexpression of VEGF and KDR receptor by the well-established leukemic cell line HL-60 and leukemic blasts from patients with acute leukemia is associated with their biologic functional response in leukemogenesis and to obtain a novel therapeutic approach for the treatment of a subset of acute leukemia.Methods: 1. The serum and leukemic cell culture supernatants VEGF levels were measured by sandwich ELISA in 88 acute leukemia patients including 25 acute leukemia patients with extramedullary infiltration and 30 healthy individuals.2. Bone marrow samples from 45 patients with de novo acute leukemia including 30 patients of acute leukemia with extramedullary infiltration and 20 healthy individuals were obtained. Mononuclear cells were separated by density gradient centrifugation. Expression of VEGF and receptor KDR in leukemic cell line HL-60 , leukemic blasts and healthy mononuclear cell was determined by immunocytochemical staining, reverse transcription-polymerase chain reaction (RT-PCR) and western blot.3. Transwell chamber in vitro invasion assay was used to detect the invasive capacity in vitro in KDR+ leukemic cell line HL-60 and leukemic blasts incubated with or without VEGF.4.Supernatants from healthy mononuclear cell and KDR+ leukemic cell were collected after incubation in serum-free medium with or without VEGF. Their activity of MMP-2 was measured by gelatinolytic zymography.Results: 1. The prechemotherapeutic serum and supernatant VEGF level in newly diagnosed or relapsed patients with acute leukemia was significantly higher than those of healthy subjects (P<0.01). The serum VEGF level was correlated with the count of blast cells in bone marrow or peripheral blood of patients with acute leukemia (P<0.01). The serumVEGF level in patients of acute leukemia with extramedullary infiltration was significantly higher than those of patients without extramedullary infiltration.2. The positive VEGF expression were detected by immunocytochemical staining in 33 (73.3%) acute leukemia samples. The expression of VEGF in patients with acute myeloid leukemia(75.8%) and in patients with acute lymphatic leukemia (66.7%) were obviously higher than those of healthy subjects(P<0.01). The expression of VEGF in patients of acute leukemia with extramedullary infiltration(86.7%) was significantly higher than those of patients without extramedullary infiltration(46.7%)(P<0.05). The positive VEGF expression was detected in leukemic cell line HL-60.3. The positive VEGF/KDR expression were detected by RT-PC...