L1CAM and neoplasm: Untransduced T cells were able to migrate into the tumor model (mean=22,334 cells, range=20,203-23,004 cells), but their numbers corresponded to only about 10% of the CD28-costimulated and 25% of the 4-1BB–costimulated L1CAM-CAR T cells that infiltrated the 3D tumor model (Figure 1C).