PTEN and acute lymphoblastic leukemia: SPI1 is an ETS domain-containing transcription factor critical for early T cell progenitor function (Zhang et al., 2012), and its overexpression or translocation induces T progenitor cell proliferation and blocks differentiation (Anderson et al., 2002; Seki et al., 2017), similar to the effects we observed in the Pten-null T-ALL model.