PROM1 and glioblastoma: Using electron microscopy for ultrastructural analysis, we observed the presence of electron-dense granules on the cell surface of the CD133+ glioblastoma and UCB cells, thus demonstrating the presence of anti-CD133 monoclonal antibodies bound to magnetics beads recognizing the CD133 membrane proteins on the cell surface (Figure 3B, 3C, 3H, 3I, 3L, 3M).