CD70-specific T cells kill CD70-positive tumor cell lines. (A) CD70-CAR T cells (solid lines) killed K562.70 cells but not parental K562 cells. Nontransduced control T cells (dashed lines) did not kill either target. (B) CD70-CAR T cells (solid lines) killed CD70-positive Daudi, U266, SNK6, and SNT16 tumor cell lines; control T cells (dashed lines) did not. (C) CD70-specific T cells or nontransduced T cells were labeled with CFSE and cocultured with SNT16 cells at a ratio of 2:1. CD70-specific T cells proliferated and killed SNT16 cells, as shown by CFSE dilution of CD3⁺ cells and by the lack of CD3/CFSE-negative cells in the culture compared with nontransduced T cells. (D) In all coculture experiments, only CD70-specific T cells eliminated the CD3/CFSE–negative CD70⁺ tumor cells Daudi, U266, SNK6, and SNT16.