The suppressor of cytokine signalling-1 (SOCS-1) gene is overexpressed in Philadelphia chromosome negative chronic myeloproliferative disorders

The suppressor of cytokine signalling-1 (SOCS-1) is a negative regulator of signal transduction mediated by cytoplasmic tyrosine kinases such as the Janus kinases (JAKs). We investigated SOCS-1 expression in bone marrow cells from Philadelphia chromosome negative chronic myeloproliferative disorders (Ph− CMPD) and normal haematopoiesis (n = 121), and additionally in peripheral blood samples (n = 18). Except for chronic idiopathic myelofibrosis harbouring wild-type JAK2, other Ph− CMPD expressed significantly higher SOCS-1 levels of up to 14-fold compared to the control group (p < 0.001) independent of the JAK2 status. The mononuclear cell fraction but not granulocytes in patients with Polycythaemia vera also significantly overexpressed SOCS-1. We conclude that up-regulation of the SOCS-1 gene might reflect a compensatory feedback mechanism with different emphasis among Ph− CMPD subtypes independent of an underlying JAK2 (V617F) mutation.