 This mutation (V617F), a change of valine to phenylalanine at the 617 position, appears to render hematopoietic cells more sensitive to growth factors such as erythropoietin and thrombopoietin, because the receptors for these growth factors require JAK2 for signal transduction.An inhibitor of JAK2-STAT5, AZD1480, was pointed as having activity in primary and CRPC.Jak2 mutation, when demonstrable, is one of the methods of diagnosing polycythemia vera.