OBJECTIVETo study the protective effect of bone marrow stromal cells (BMSCs) upon childhood leukemia cells and the influence of VLA-4 antibody in vitro on leukemia cell apoptosis.

METHODSBMSCs from children with acute leukemia-were isolated by human lymphocyte separation medium. BMSCs (adherent) and leukemia cells (suspended) were cultured in vitro. This study included four groups: leukemia cells alone (control), leukemia cells+BMSCs, leukemia cells+BMSCs supernatant and leukemia cells+BMSCs+VLA-4 antibody. The apoptosis rate of leukemia cells in the four groups was determined by Annexin Ⅴ-FITC double-labeled flow cytometry. The expression of survivin and bcl-2 genes in leukemia cells was ascertained by RT-PCR.

RESULTSThe apoptosis rate of leukemia cells in the leukemia cells+BMSCs and the leukemia cells+BMSCs supernatant groups was lower than that in the control group (P<0.05). Compared with the leukemia cells+BMSCs and the leukemia cells+BMSCs supernatant groups, the apoptosis rate of leukemia cells in the VLA-4 antibody group increased significantly (P<0.05). In the VLA-4 antibody group, the apoptosis rate of leukemia cells increased with prolonged culture time. There were significant differences in the apoptosis rate between 12 hrs and 24 hrs after VLA-4 antibody treatment (P<0.01). The expression of survivin and bcl-2 genes in leukemia cells from the VLA-4 antibody groups was reduced compared with that from the leukemia cells+BMSCs and the leukemia cells+BMSCs supernatant groups (P<0.05).

CONCLUSIONSBMSCs play protective roles on leukemia cells. VLA-4 antibody can block the adhesion between BMSCs and leukemia cells and promote leukemia cell apoptosis.