Is Rescued by the AKT/Protein Kinase B Oncogene Tumor Suppressor Induces Cell Death

PTEN/MMAC1 is a tumor suppressor gene that is mutated in a variety of cancers. PTEN encodes a phosphatase that recognizes phosphoprotein substrates and the phospholipid, phosphatidylinositol-3,4,5-triphosphate. PTEN inhibited cell growth and/or colony formation in all of the epithelial lines tested with one exception. The decrease in cellular proliferation was associated with an induction of apoptosis and an inhibition of signaling through the phosphatidylinositol 3'-kinase pathway. Akt/protein kinase B, a gene whose antiapoptotic function is regulated by phosphatidylinositol3,4,5-triphosphate, was able to rescue cells from PTEN-dependent death. PTEN, therefore, appears to suppress tumor growth by regulating phos phatidylinositol .V-kinu.su signaling.