| Residual leukemic cells remain to the origin of leukemia relapse after chemotherapy remission so that the leukemic iatreusiology was usually restricted. The aim of this experiment was remidmently to study the mechanism of acute leukemic bone marrow stroma in residual leukemia development. With the method of bone marrow stromal cell culture system or co-culture system of bone marrow stromal cells,HL-60 cells and idarubicin, light microscope, electron microscope, flow cytometry and enzyme-linked immunoadsodent assay respectively to investigate the growth properties of leukemic bone marrow stroma, the expression of VCAM-1(vascular cell adhesion molecule-1),Fn(fibronectin) and IL-6(interleukin-6),TNF-α(tumor necrosis factor-alpha) in culture medium, moreover, roles of acute leukemic bone marrow stromal cell in residual leukemia development were also investigated. The main results are as follows:1. The growth of acute leukemic bone marrow stromal cell was delayed. The time of sticking to wall, the time of microplexus formation, the time of colony formation, the time of confluence formation, were all significantly delayed (P<0.05). The number of CFU-F and the content of VCAM-1 in stromal cells from acute leukemia was respectively significantly decreased with that of controls(P<0.05),in addition, the content of Fn in stromal cells from acute leukemia was identical with that of controls(P>0.05) ,whereas, the content of IL-6 and TNF-α in the culture medium from acute leukemic bone marrow stromal cells was significantly increased compared with that ofcontrols.2. The action of acute leukemic bone marrow stromal cells on proliferation of HL-60 cells was significantly increased, while that on induction differentiation is significantly decreased compared with that of the controls.3. The capacity for binding of HL-60 cells to acute leukemic stromal cell adherence layer was significantly increased compared with that of the controls. Adherent HL-60 cell cycle status was evaluated after 72 hours of co-culture with bone marrow stromal cells. HL-60 cells had 48.51% in G0/G1 cultured with acute leukemic stromal cells, while significally decreased to 33.25% in G0/G1 cultured with normal bone marrow stromal cells (P<0.05).4. The effect of IDA was dosage and time-dependency. HL-60 cells were 96% killed after 72 hours of treated with 50ng/ml or 75ng/ml IDA in medium alone. The effect was decreased dramatically during co-culture in the presence of bone marrow stromal cells, although the descent tendency of HL-60 cell viable was seen with the dosage of IDA increasing. HL-60 cells treated with 25ng/ml IDA were 52.1-71% viable, in addition HL-60 cells remained 11.7-20.1% viable treated with 75ng/ml IDA. After 72 hours of treated with 50ng/ml IDA, HL-60 cell viable significantly increased to 41.2% in acute leukemic bone marrow stromal cells compared to 33.9% in normal controls. The results supported the conclusion that acute leukemic bone marrow stromal cell co-culture consistently resulted in higher viable of HL-60 cells.5. Using a blocking anti-VCAM-1 antibody, IDA (50ng/ml), HL-60 cells co-cultured 24 hours with leukemic stromal cells or normal stromal cells, viable of HL-60 cells were respectively from 78%, 70.2% viable reduced to 39.47%, 34.33% compared with treated no anti-VCAM-1 antibody (P<0.05). These observations support the conlusion that role of bone marrow stroma protecting HL-60 cells from chemotherapy through inter-adhesiveness. IDA(50ng/ml) was cultured for 24 hours in stromal cell-conditioned medium or simple medium alone and effect on HL-60 cells of 24h was evaluated, regardless of the leukemic stromal cell groups, normal stromal cell groups or simple medium groups, Significantly differences in viable of HL-60 cells was observed compared to control fresh medium (P<0.05), while no difference was seen between them (P>0.05). The observation support the conclusion that bone marrow stromal cell or stromal cell conditioned-culture medium had no roles in inactivation IDA and that effect on HL-60...
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