CIP2A and cancer: 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.