Scientific Journal of

Abstract
Background and Objectives
The expression of Numb as a cell-fate determinant gene leads to inhibition of leukemic cell growth. The high levels of Musashi2 (Msi2) results in down-regulation of Numb in chronic myeloid leukemia cells. In this study we knocked down Msi2 using RNA interference (RNAi) strategy and investigated the effects of this knock down on the expression of Musashi2-Numb axis and genes involved in proliferation and apoptosis.
 
Materials and Methods
In this experimental study, synthetic double stranded siRNAs designed to target human Msi2 were transfected to K562 cells using Lipofectamine in duplicate. Changes in the expression levels of Msi-2, Numb, P21, and Bcl-2 genes 48h after transfection were evaluated by real-time PCR. Induction of apoptosis in transfected leukemic cells was determined using Annexin-PI staining and flowcytometry analysis. Data were analyzed by t-test.
 
Results
We found that upon Msi2 suppression, the expression levels of the cell-fate determinant Numb showed two-fold increase in K562 cells (p < 0/05). Msi2 down-regulation and subsequent increase in Numb expression levels caused the elevated expression of p21, as a cell cycle regulator (p < 0/05). In addition, Msi2 down-regulation promoted cell apoptosis via the down-regulation of Bcl-2 expression (p < 0/05). We observed that the rates of apoptosis in leukemic increased to 52% and 60%, 24h and 48h after transfection.
 
Conclusions 
It seems that Msi2 could be an option for targeting leukemic cells and its down-regulation through RNAi strategy may lead to induction of apoptosis in leukemic cells. This approach may open up new opportunities for leukemia therapy.