In vivo ST3GAL6 knockdown. (A) Graphic representation of the anatomic region of the mouse skull examined using confocal microscopy. (B) Representative in vivo confocal microscopy images of scrambled control MM1S-GFP⁺ cells demonstrating homing to the BM of SCID-Bg mice 18 hours after tail vein injection of 1 × 10⁶ cells (left panel). In these mice, GFP⁺ cells were visible within the vessels and in the surrounding BM niche, indicating their homing ability. The right panel demonstrates the corresponding vessels in mice that received shST3GAL6 cells; in these mice, there was no evidence of GFP⁺ cells arriving to the BM, indicating an impaired ability of these cells to home. Images are representative of n = 3 per group. (C) Quantification of in vivo homing of shST3GAL6 or scrambled control GFP⁺ cells to the BM in vivo. shST3GAL6 cells demonstrated a reduced homing ability, P = .0015. (D) Representative in vivo confocal microscopic images demonstrating a reduction in engraftment and tumor growth of ST3GAL6 knockdown cells in the BM niche of the skull 4 weeks after IV injection of 5 × 10⁶ shST3GAL6 or scrambled control cells (n = 3/group). (E) Quantification of in vivo engraftment of shST3GAL6 cells vs scrambled controls. shST3GAL6 cells demonstrated significantly reduced engraftment, P < .0001.