We also demonstrated that the deregulated serine phosphorylation of STAT5b may be due to the defective activity of the protein phosphatase 2A as the consequence of increased inhibition exerted by the allosteric inhibitor CIP2A; furthermore, it is shown here for the first time, to the best of our knowledge, that CIP2A is over-expressed in MPN patients compared to healthy controls. The gene discussed is CIP2A; the disease is myeloproliferative neoplasm.