Because the cells which make up the lumen-obliterating lesions in the lungs from PAH patients are abnormal and have been characterized as ‘quasi malignant’ [17] and because of the cellular and molecular cross talk between chronic inflammation, angiogenesis and cancer and a postulated role for cyclooxygenase 2 (COX-2) metabolites, in particular prostaglandin E2, in the pathobiology of metastasizing cancers [18,19,20,21,22], our second goal was to test a COX-2 inhibitor in the SuHx model of severe angioobliterative pulmonary hypertension (PAH)[16,23,24]. This evidence concerns the gene PTGS2 and pulmonary arterial hypertension.