ERBB2 and neoplasm: To explore this further and the influence of PTPN2 deficiency on CAR T‐cell memory, we re‐implanted HER‐2+ tumour cells into control HER‐2 transgenic mice, or those mice in which HER‐2+ tumours had been previously cleared by PTPN2‐deficient HER‐2 CAR T cells (Fig 5D and E).