As OA, a PP2A inhibitor, promotes tumor growth, and inactivation of PP2A is required for the cellular malignant transformation induced by SV40 and RalA, the tumor suppressor role of PP2A is strongly suggested.[15, 35, 37, 38] Importantly, aberrant expression of the PP2A inhibitors, such as SET and cancerous inhibitor of PP2A (CIP2A), in tumor cells are the major causes of PP2A dysfunction in human cancers. This evidence concerns the gene PTPA and neoplasm.