[Apoptosis of chronic myeloid leukemia stem/progenitor cells induced by anti-CD44 monoclonal antibody IM7 in vitro].

The aim of this study was to investigate the apoptosis-inducing effect of anti-CD44 monoclonal antibody IM7 on chronic myeloid leukemia (CML) stem/progenitor cells in vitro and to explore its possible mechanism. Leukemic stem/progenitor cells (LSPCs) expressing CD34(+), CD38(-) and CD123(+) were isolated from bone marrow (BM) cells of 20 patients with newly-diagnosed chronic myeloid leukemia by using EasySep(TM) magnetic beads. The percentage of apoptotic CML-LSPCs was assayed by Annexin-V/PI staining; the expression changes of c-myc and NF-kappaB mRNA were detected by real-time quantitative PCR (RQ-PCR) and RT-PCR; the NF-kappaB activity was detected by NF-kappaB Activation Nuclear Translocation Assay Kit; the BCL-2 protein expression was determined in the Western blot method. The results showed that the IM7 effectively induced apoptosis of CML-LSPCs; the mean percentage of early apoptotic cells significantly increased, as compared with the untreated control CML-LSPCs cells 12.58 +/- 2.84% vs 5.42 +/- 1.84% (p < 0.05). The c-myc, NF-kappaB mRNA expressions were down-regulated as compared with the control group (0.65 +/- 0.10 vs 1.00, 0.42 +/- 0.21 vs 1.00, respectively) (p < 0.01) by RQ-PCR and (0.49 +/- 0.09 vs 0.60 +/- 0.12, 0.47 +/- 0.11 vs 0.67 +/- 0.08, respectively)(p < 0.01) by RT-PCR. The BCL-2 protein level in CML-LSPCs treated with IM7 also decreased as compared with the control group (p < 0.01). In addition, the depression of NF-kappaB activity was observed through fluorescence microscope. It is concluded that the anti-CD44 monoclonal antibody IM7 effectively induces apoptosis of CML-LSPCs through down-regulating c-myc and bcl-2 mRNA expression, and decreasing NF-kappaB activity in CML-LSPCs.