L1CAM and neuroblastoma: L1CAM-specific second-generation CAR T cells [20] expressing CARs harboring either CD28 (L1CAM-CD28 CAR) or 41BB (L1CAM-4-1BB CAR) as costimulatory domain (Figure S1A) and enriched for homogenous levels of EGFRt expression by cetuximab immunomagnetic positive selection (Figure S1B) were cocultured with the selected neuroblastoma reporter cells in different effector to target (E:T) ratios ranging from 10:1 to 1:10.