Changes in Intracellular signal transduction in 4 T1 cells in co-culture with MSC/IFNβ/GFP. 4 T1 breast cancer cells were co-cultured with MSC/IFNβ/GFP for 48 hours. Western blot were performed to examine changes in expression levels of several oncoproteins and proteins involved in metastasis., pStat3, pSrc and pAKT were inactivated; and expression of c-Myc and mmp2 was completely abolished (a). (Quantitative analysis is shown in lower panel of a). Similar results were observed when 4 T1 cells were treated with recombinant murine IFNβ, b (quantitative analysis in b, lower panel). c shows inhibition of Stat3 activation after 4 T1 cells were co-cultured with MSC/IFN-β/GFP or murine recombinant IFN-β. d: immunohistochemical staining of pStat3 in 4 T1 tumor in vivo after systemic administration of MSC/IFN-β/GFP cells in mice, d, right panel; mice treated with MSC/GFP, as the control, showed a strong pStat3 activity in 4 T1 tumors, (left panel)