TNFRSF17 and neoplasm: Three non-mutually exclusive possibilities could explain the particularly strong persistence of BCMA−/CS1+ tumor cells in animals treated with OR-gate CAR-T cells: (i) the OR-gate CAR-T cells were less effective against CS1 than against BCMA, (ii) the residual tumor cells have become unrecognizable or resistant to CAR-T cells, or (iii) the BCMA−/CS1+ tumor line has an inherent growth advantage over the wildtype and BCMA+/CS1− MM.1 S lines.