Inducible expression of MPN alleles in the background of a constitutive COX-2/PGE2 knockout will test the role of inflammation in MPN initiation, whereas constitutive expression of MPN mutations and subsequent inducible deletion of a COX-2/PGE2 axis gene will test for the requirement of an inflammatory milieu in maintaining the MPN phenotype. The gene discussed is PTGS2; the disease is myeloproliferative disorder.