siRNA-mediated Silencing of Survivin Inhibits Proliferation and Enhances Etoposide Chemosensitivity in Acute Myeloid Leukemia Cells

Background: Overexpression of survivin, a known inhibitor of apoptosis, is associated with tumor progressionand drug resistance in numerous malignancies, including leukemias. The aim of this study was to investigate theeffect of a specific survivin small interference RNA (siRNA) on proliferation and the sensitivity of HL-60 acutemyeloid leukemia (AML) cells to the chemotherapeutic drug etoposide. Materials and
Methods: The cells weretransfected with siRNAs using Lipofectamine™2000 transfection reagent. Relative survivin mRNA and proteinlevels were measured by quantitative real-time PCR and Western blotting, respectively. Trypan blue exclusionassays were performed to monitor tumor cell proliferation after siRNA transfection. The cytotoxic effects ofetoposide and survivin siRNA, alone and in combination, on leukemic cells were determined using MTT assay.Apoptosis was assessed by ELISA cell death assay.
Results: Survivin siRNA markedly reduced both mRNA andprotein expression levels in a time-dependent manner, leading to distinct inhibition of cell proliferation andincreased spontaneous apoptosis. Surprisingly, survivin siRNA synergistically increased the cell toxic effects ofetoposide. Moreover, survivin down-regulation significantly enhanced its induction of apoptosis.
Conclusions: Ourstudy suggests that down-regulation of survivin by siRNA can trigger apoptosis and overcome drug resistanceof leukemia cells. Therefore, survivin siRNA may be an effective adjuvant in AML chemotherapy