Human mesenchymal stem cells have emerged as attractive cellular vehicles to deliver therapeutic genes for ex-vivo therapy of diverse diseases because they have the capability to migrate into tumor or lesion sites. Previously, we showed that mesenchymal stem cells could be utilized as a cellular vehicle to deliver a bacterial cytosine deaminase suicide gene to brain tumors. Here, we assessed whether transduction with a retroviral vector encoding cytosine deaminase gene might alter the stem cell property of mesenchymal stem cells. Mesenchymal stem cells were transduced at passage 1 and cultivated up to passage 11. We found that proliferative and differentiation potential, chromosomal stability and surface antigenicity of mesenchymal stem cells were not altered by retroviral transduction. The results indicate that retroviral vectors can be safely utilized for deliver suicide genes to mesenchymal stem cells for ex-vivo therapy. We also found that the single retroviral transduction was sufficient for the sustainable expression up to passage 10. The long-lasting expression of transduced gene warrants manufacturing the transduced mesenchymal stem cells tractable and manageable for allogeneic transplantation.