AKT1 and neoplasm: The resulting tumors exhibited an overall expression pattern similar to that of PTEN WT tumors (Fig. S5), but had undetectable levels of PTEN in the tumor bulk regions and elevated levels of phosphorylated Akt, a marker of PI3K activity, and elevated phosphorylated ribosomal protein S6, a marker of mTORC1 pathway activation (Fig. S4A and S4B).