ERBB2 and neoplasm: Moreover, PTPN2‐deficient CD8+ HER‐2 CAR T cells exhibited increased antigen‐specific cytotoxic capacity in vitro (Fig EV1C; Appendix Fig S4A), as assessed by the increased intracellular expression of IFNγ (required for tumour eradication by CAR T cells in vivo; Moeller et al, 2005), TNF and granzyme B upon challenge with 24JK‐HER‐2 cells but not 24JK cells.