Experimental Studies And Clinical Significance Of Bone Marrow Angiogenesis And Related Mechanism In Adult Patients With Acute Leukemia

Angiogenesis, which refers to new blood vessel growing from existing vessels, is a multistep process including degradation of extracellular matrix, stimulation, proliferation and migration of endothelial cells. It is regulated by interactions among several vascular growth factors, cytokines and their inhibitors. Vascular endothelial growth factor (VEGF), the specific mitogenic activator of vascular endothelial cell, is the most effective, specific and popular angiogenesis regulator studied now. VEGF combines mainly with two tyrosine kinase receptors, fins-like tyrosine kinase-1 (FLT-1) and kinase-domain insert containing receptor (KDR), to activate endothelial cell mitogen. It has been established that the growth, invasion and metastasis of solid tumors are angiogenesis-dependent.As one of the malignant cloning diseases derived from hematopoietic stem cell, acute leukemia is a "fluid" tumor. Angiogenesis was first demonstrated in the bone marrow of child with acute lymphoblastic leukemia (ALL) by Perez-Atayde in 1997. Researches on angiogenesis in adult patients with acute myeloid leukemia (AML), especially with ALL, are very limited in abroad, and none in China so far. Furthermore, the alternation of gene expression and protein secretion of VEGF and itsreceptors FLT-1, KDR in bone marrow of patients with different types of acute leukemia in different phase, and the relationships between the extent of VEGF in bone marrow fluid and microvassel counts in bone marrow of patients are still not elucidated. The related reports are not found in the aspect whether Homoharringtonine (HIT) reduces expression of VEGF in the leukemic cells and influences the angiogenesis to relieve leukemia.Bone marrow biopsy specimens from 95 adult patients with acute leukemia (70 cases with newly diagnosed untreated acute leukemia, 5 cases with relapse/refractory acute leukemia, 20 cases with acute leukemia achieving bone marrow remission) and 15 normal controls were referred to our experiments. Microvessels in bone marrow were counted by immunohistochemical identification of microvascular endothelial cells with anti-human von Willebrand Factor (the microvessel density of a bone marrow specimen section was calculated as the mean value of all independent readings and recorded as the number of microvessels per 400 times field) under light microscopy in 400 times field (one field equals to 0.233 mm2). The results were as follows: both microvessel counts in patients with newly diagnosed and untreated acute leukemia (23.09?.747x400 field ) were significantly higher than those in the bone marrow remission patients (8.40?.20/x400 field) and in the control patients (7.41?.49/X400 field) (p<0.001). There was also statistical significance between the latter two groups (p<0.05). On the other hand, statistic analysis revealed no significance in microvessel counts of newly diagnosed, untreated group, compared with those of relapse/refractory group. In the newly diagnosed untreated group, the microvessel counts showed any difference neither between 23 ALL patients and 43 ANLL patients (23.90?.147x400 field vs. 22.61?.21/x400 field, p>0.05), nor between patients with Mi.3and M^s, two subtypes of FAB (22.89?.507x400 field vs.22.27?.96/x 400 field, pX).05). There was a certain correlation between the microvessel counts and the percentage of blast cells in bone marrow(r=0.31 l,p<0.01). These results indicated an increase of the microvessl counts in bone marrow of patients with different types of acute leukemia. However, the microvessel count was not a valuable index to predict the prognosis of induction chemotherapy at the first diagnosis.To explore the possible effects of VEGF on acute leukemia pathogenesis, we used techniques such as reverse transcription polymerase chain reaction (RT-PCR), culture of bone marrow mononuclear cells (MNCs) in vitro, ELISA and MTT methods to evaluate the mRNA expressions of VEGF, FLT-1 and KDR of bone marrow MNCs in patients with different types of acute leukemia at different phase, as well as the l...