Furthermore, treating the Pten-null T-ALL model with PI3K inhibitors is effective only before the onset of leukemia, not after leukemia is already underway (Guo et al., 2011; Schubbert et al., 2014), suggesting that this driver mutation is not responsible for the maintenance of LSC ‘stemness’ once it has been generated. The gene discussed is PTEN; the disease is leukemia.