CDK9 and cancer: In addition, approximately one of three PP2A subunits can occur as a dimer consisting of just one A and one C subunit.120,121 PP2A is considered a tumor suppressor, and its activity and expression are decreased in many cancer cell.122,123 Restoration of PP2A activity through synergy with a MEK inhibitor, DUSP inhibitor, or CDK9 inhibitor is a promising strategy in cancer therapy.122,123