BH3 mimetic ABT-737 induces apoptosis in CD34+ acute myeloid leukemia cells and shows synergistic effect with conventional chemotherapeutic drugs

Abstract

Aims: Acute myeloid leukemia (AML) is an immunophenotypically heterogenous malignant disease. The early immature CD34⁺ AML cell subpopulation is frequently impervious to intensive chemotherapy, making them largely responsible for relapse of AML. CD34⁺ AML cells have higher level of Bcl-2 protein expression than the CD34^- subpopulation. As such, development of drugs that specifically target the Bcl-2 may have the potential to eliminate immature CD34⁺ AML progenitor cells and provide therapeutic benefit. In this work, we made an attempt to investigate the cytotoxic effect of a novel Bcl-2 family inhibitor, ABT-737, on CD34⁺ AML cell lines (KG1a and Kasumi-1) as well as CD34⁺ primary AML cells.

Methods: Primary human CD34⁺ cells were isolated from bone marrow mononuclear cells using CD34 MicroBead kit. The growth inhibitory effect was measured by cell counting kit-8. Apoptosis was analyzed by annexin V/PI assays. Protein expression was determined by Western blotting analysis.

Results: Inhibition of Bcl-2 by ABT-737 effectively inhibited growth and induced apoptosis in CD34⁺ AML cell lines and CD34⁺ primary AML cells without affecting CD34⁺ normal hematopoietic cells. Furthermore, Western blot analysis showed that ABT-737 induced apoptosis associated with caspase-3 activation and poly ADP-ribose polymerase (PARP) degradation. Finally, ABT-737 synergistically enhanced the cytotoxic effect of cytarabine and daunorubicin in CD34⁺ AML cells.

Conclusion: Taken together, these findings indicate that ABT-737 may offer as a promising molecular targeting agent in CD34⁺ AML.

Keywords: ABT-737; Bcl-2; acute myeloid leukemia; apoptosis.