EIF4EBP1 and angiosarcoma: We then focused on the analysis of the PI3K/mTOR and MAPK pathways as these are known to be regulated respectively by two of the targeted genes, Pten and Ptpn12. Western blot analysis revealed that phospho-4EBP1 is elevated in all tumors including those that were Pten wild-type, suggesting that activation of the mTOR pathway is important for angiosarcoma growth (Figure 2B).