PTPA and chronic myelogenous leukemia, BCR-ABL1 positive: Very commonly, PP2A inactivation in cancer occurs through overexpression of the endogenous PP2A inhibitors SET (Suvar/Enhancer of zeste/Trithorax) and CIP2A (cancerous inhibitor of PP2A), for example in chronic myeloid leukaemia and in many solid tumour types [136].