PTEN and acute lymphoblastic leukemia: To confirm that the absence of T-ALL in dKO mice is not due to a block in T cell development in the Pten; Spi1-null T progenitor cells (Champhekar et al., 2015; Spain et al., 1999), we first quantified CD3+ T cells in the WT, Pten-null and dKO mice and found relatively normal numbers of CD3+ cells in the dKO thymus (Figure 6F).