Down-Regulation of Mcl-1 by Small Interference RNA Induces Apoptosis and Sensitizes HL-60 Leukemia Cells to Etoposide

  • Karami, Hadi (Immunology Research Center, Department of Medical Immunology, Faculty of Medicine, Tabriz University of Medical Sciences) ;
  • Baradaran, Behzad (Immunology Research Center, Department of Medical Immunology, Faculty of Medicine, Tabriz University of Medical Sciences) ;
  • Esfehani, Ali (Hematology and Oncology Research Center, Shahid Ghazi Hospital, Tabriz University of Medical Sciences) ;
  • Sakhinia, Masoud (Faculty of Medicine, University of Liverpool) ;
  • Sakhinia, Ebrahim (Tuberculosis and Lung Diseases Research Centre, Department of Medical Genetics, Faculty of Medicine, Tabriz Genetic Analysis Centre, Tabriz University of Medical Sciences)
  • Published : 2014.01.30


Background: Acute myeloid leukemia (AML) is a fatal hematological malignancy which is resistant to a variety of chemotherapy drugs. Myeloid cell leukemia-1 (Mcl-1), a death-inhibiting protein that regulates apoptosis, has been shown to be overexpressed in numerous malignancies. In addition, it has been demonstrated that the expression level of the Mcl-1 gene increases at the time of leukemic relapse following chemotherapy. The aim of this study was to target Mcl-1 by small interference RNA (siRNA) and analyze its effects on survival and chemosensitivity of acute myeloid leukemia cell line HL-60. Materials and Methods: siRNA transfection was performed with a liposome approach. The expression levels of mRNA and protein were measured by real-time quantitative PCR and Western blot analysis, respectively. Trypan blue assays were performed to evaluate tumor cell growth after siRNA transfection. The cytotoxic effects of Mcl-1 siRNA (siMcl-1) and etoposide were determined using MTT assay on their own and in combination. Apoptosis was quantified using a DNA-histone ELISA assay. Results: Transfection with siMcl-1 significantly suppressed the expression of Mcl-1 mRNA and protein in a time-dependent manner, resulting in strong growth inhibition and spontaneous apoptosis. Surprisingly, pretreatment with siMcl-1 synergistically enhanced the cytotoxic effect of etoposide. Furthermore, Mcl-1 down-regulation significantly increased apoptosis sensitivity to etoposide. No significant biological effects were observed with negative control siRNA treatment. Conclusions: Our results suggest that specific suppression of Mcl-1 by siRNA can effectively induce apoptosis and overcome chemoresistance of leukemic cells. Therefore, siMcl-1 may be a potent adjuvant in leukemia chemotherapy.


Supported by : Tabriz University of Medical Sciences


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