To explore the relationship between liver injury and tumor formation; and particularly the cell types that undergo each of these two processes (tumor formation vs. liver injury), we targeted the deletion of Pten to the Sox9+ cells in the adult liver (Sox9-Pten, PtenloxP/loxP; Sox9-CreERT+; R26RYFP + tamoxifen). The gene discussed is PTEN; the disease is neoplasm.