PIK3CA and neoplasm: Inositol polyphosphate 4-phosphatase type II (INPP4B) dephosphorylates PI(3,4)P2 downstream of class I PI3K to form phosphatidylinositol 3-phosphate (PI(3)P), also suppresses AKT signaling, and is proposed to function as a tumor suppressor in some cancers5,6.