Mouse tumours showed prototypical activating mutations affecting Notch1 and loss of the tumour-suppressor genes Pten and Ikzf1, supporting the fact that the p53 null Zeb2 transgenic mouse model closely recapitulates human T-cell leukaemia35, 36, 37, and is in keeping with the higher occurrence of IKZF1 mutations in ETP-ALLs7. This evidence concerns the gene PTEN and neoplasm.