AKT1 and neoplasm: The PTEN gene is a tumor suppressor encoding the phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase protein (PTEN), which negatively regulates the intracellular levels of phosphatidylinositol-3,4,5-trisphosphate and the AKT/PKB pathway, involved in promoting cell survival and growth in response to extracellular signals.