CD44 and sarcoma: PTPN2‐deficient CD8+ HER‐2 CAR T cells were more activated, as assessed by the expression of CD44, CD25, PD‐1 and LAG‐3, after overnight incubation with HER‐2‐expressing 24JK (24JK‐HER‐2) sarcoma cells, but importantly, not HER‐2‐negative 24JK control cells (Fig EV1B).