miRNA-155 knockdown targets WM cells in the context of bone marrow microenvironment in vivo. (A) In vivo confocal imaging. GFP⁺ WM cells were transfected using either control probe or miRNA-155 knockdown probe, and then injected in mice 24 hours after transfection. GFP⁺ WM cells (green) were excited with a 491-nm solid state laser. Blood vessels (red) were imaged using Angiosense-750 (VisEn Medical) excited with a 750-nm laser. Images of parasagittal vasculature and GFP⁺ tumor cells in the mouse skull bone marrow. Control probe–transfected cells homed and adhered more than the miRNA-155–transfected counterparts. (B) Detection of human IgM from serum of control probe–injected (n = 4) and miRNA-155 knockdown probe–injected (n = 4) mice. Serum of noninjected mice was used as negative control. Average obtained from each group is shown. (C) Kaplan-Meier curve showing survival in each group; mean survival was 14 days versus 20 days (P < .001), and overall survival was 15 days versus 21 days, respectively, in control probe–injected versus miRNA-155 knockdown probe–injected mice.