Journal of

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Introduction: Leukemia is a heterogeneous malignant disease in which progression at the level of CD34+ cells has a major impact in drug resistance and relapse. The multi-drug resistance gene product, P-glycoprotein is an inhibitor of apoptosis proteins (IAPs), such as Survivin that are expressed simultaneously with several putative drug resistance parameters in CD34+ leukemia cells. In fact, IAPs over-expression and their anti-apoptotic splice variants are associated with CD34 positivity, poor response to chemotherapy and reduced overall survival in leukemic patients. Recently, adenosine 5ʹ-triphosphate (ATP) has been reported to inhibit proliferation and induce apoptosis in several human cell lines. The K562 CD34+ human myeloid leukemia cell line has the unique feature of expressing significant functional IAPs and other drug-resistance genes. Thus, the efficacy of ATP in overcoming the resistance and expression profile of Survivin and its splice variants were examined in K562 cells in the present study. Methods: K562 cell were cultured and treated several times with different concentrations of ATP. Apoptosis was studied by fluorescent microscopy(Ao/EtBr double staining) and DNA fragmentation assay. The expression level of Survivin and its splice variants was studied by semiquantative RT-PCR method. Results: The results showed that over-expression of Survivin and its anti-apoptotic splice variant, 3b splice variant were decreased after treatment by ATP in a time- and dose-dependent manner. The expression levels of other splice variants (ΔEx3, 2b, 2α and 3α) did not show significant difference between the control and the treated cells. Conclusion: The results showed that ATP attenuated expression of Survivin and its anti-apoptotic splice variant, meaning that this nucleotide can facilitate apoptosis in drug-resistant leukemia cells. In addition, combination of ATP with standard chemotherapies may be utilized for inhibition of drug-resistance in leukemia cells.